[go: up one dir, main page]
Next Issue
Volume 14, July-1
Previous Issue
Volume 14, June-1
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.8
3.1
Journals
Materials
Volume 14
Issue 12
materials-logo

Journal Menu

► Journal Menu

Journal Browser

► Journal Browser
share announcement

Materials, Volume 14, Issue 12 (June-2 2021) – 299 articles

Cover Story (view full-size image): The constant development of environmental protection causes the necessity to increase the efficiency of machines. By increasing the efficiency of machines, energy losses can be limited, leading to lower energy consumption. Friction reduction leads to an increase in efficiency and a decrease in wear. In this paper, selected surface texturing methods, such as burnishing and abrasive jet machining, with their limitations are presented. Thanks to those processes, various surface textures can be obtained. Examples of applications of these methods for friction and wear reduction are shown. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
12 pages, 3929 KiB  
Article
Advantages of Porcine Xenograft over Autograft in Sinus Lift: A Randomised Clinical Trial
by Francisco Correia, Daniel Humberto Pozza, Sónia Gouveia, António Campos Felino and Ricardo Faria-Almeida
Materials 2021, 14(12), 3439; https://doi.org/10.3390/ma14123439 - 21 Jun 2021
Cited by 14 | Viewed by 3454
Abstract
This study aimed to compare the performance of intra-oral autologous bone grafts versus porcine xenografts in a two-step lateral window sinus lift. This split-mouth randomised controlled trial sequentially enrolled 12 patients with a 6-month follow-up. For each patient, a simultaneous randomised bilateral maxillary [...] Read more.
This study aimed to compare the performance of intra-oral autologous bone grafts versus porcine xenografts in a two-step lateral window sinus lift. This split-mouth randomised controlled trial sequentially enrolled 12 patients with a 6-month follow-up. For each patient, a simultaneous randomised bilateral maxillary sinus lift was performed and filled with autologous bone from the mandible (control) or a porcine xenograft (test). A bone biopsy sample was collected during the implant placement for histological and histomorphometric analysis. CT scans were performed at the beginning and at the end of the trial to assess radiological evolution. A comparison of initial and six-month CT scans indicated statistically significant increases in bone level for both materials (7.8 ± 2.4 mm for autologous and 8.7 ± 2.2 mm for xenograft, p < 0.05), and there were no significant differences between the performance of the two materials over time (p = 0.26). The histological analysis showed various stages of the remodelling process and no cells or other signs of inflammation or infection were visible in both groups. The porcine xenografts presented similar results for the studied variables when compared to autologous bone, being a reasonable alternative for a sinus lift. Full article
(This article belongs to the Special Issue Biomaterials Development and Evaluation for Dentistry)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>A</b>) Example of the measurements at the baseline. (<b>B</b>) Example of the measurements at the 6 months.</p> Full article ">Figure 2
<p>(<b>A</b>) Example of an autograft-regenerated sinus side—H&amp;E staining—50×. (<b>B</b>) Example of a xenograft-regenerated sinus side—H&amp;E staining—50×.</p> Full article ">Figure 3
<p>(<b>A</b>) Example of autologous bone graft—H&amp;E coloration—200×. (<b>B</b>) Example of xenograft particles—H&amp;E staining—200×. (<b>C</b>) Autologous bone graft sample—H&amp;E staining—400×. (<b>D</b>) Example of xenograft particle in high magnification—H&amp;E staining—400×. Legend: * immature bone, + autologous bone graft, # osteocyte, % xenograft, ¶ soft tissue, @ osteoblast, ± osteoclast, &amp; Howship lacunae.</p> Full article ">Figure 4
<p>Clustered 95% confidence intervals for average THT by patient and by material, obtained from 10 slides in each condition.</p> Full article ">
33 pages, 18667 KiB  
Article
Rational Choice of Reinforcement of Reinforced Concrete Frame Corners Subjected to Opening Bending Moment
by Michał Szczecina and Andrzej Winnicki
Materials 2021, 14(12), 3438; https://doi.org/10.3390/ma14123438 - 21 Jun 2021
Cited by 5 | Viewed by 2728
Abstract
This paper discusses a choice of the most rational reinforcement details for frame corners subjected to opening bending moment. Frame corners formed from elements of both the same and different cross section heights are considered. The case of corners formed of elements of [...] Read more.
This paper discusses a choice of the most rational reinforcement details for frame corners subjected to opening bending moment. Frame corners formed from elements of both the same and different cross section heights are considered. The case of corners formed of elements of different cross section is not considered in Eurocode 2 and is very rarely described in handbooks. Several reinforcement details with both the same and different cross section heights are presented. The authors introduce a new reinforcement detail for the different cross section heights. The considered details are comprised of the primary reinforcement in the form of straight bars and loops and the additional reinforcement in the form of diagonal bars or stirrups or a combination of both diagonal stirrups and bars. Two methods of static analysis, strut-and-tie method (S&T) and finite element method (FEM), are used in the research. FEM calculations are performed with Abaqus software using the Concrete Damaged Plasticity model (CDP) for concrete and the classical metal plasticity model for reinforcing steel. The crucial CDP parameters, relaxation time and dilatation angle, were calibrated in numerical tests in Abaqus. The analysis of results from the S&T and FE methods allowed for the determination of the most rational reinforcement details. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>CDP yield surface in the meridian plane.</p> Full article ">Figure 2
<p>CDP plastic flow potential surface in the meridian plane.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>c</b>) CDP plastic flow potential surface in the meridian plane.</p> Full article ">Figure 4
<p>Setup for compression test: mesh (<b>a</b>) and boundary conditions (<b>b</b>).</p> Full article ">Figure 5
<p>Volumetric strain vs. longitudinal strain for different dilatation angle values in the uniaxial compression test.</p> Full article ">Figure 6
<p>Volumetric strain vs. longitudinal strain for different dilatation angle values in the biaxial 1:1 compression test.</p> Full article ">Figure 7
<p>Geometry of specimen in the uniaxial tension test; dimensions in (mm).</p> Full article ">Figure 8
<p>Crack width vs. stress relationship assumed in the uniaxial tension test.</p> Full article ">Figure 9
<p>Displacement vs. stress relationship obtained for different relaxation time values.</p> Full article ">Figure 10
<p>Displacement vs. stress relationship obtained for different relaxation time values.</p> Full article ">Figure 11
<p>(<b>a</b>) Crack pattern, relaxation time equal to 0. (<b>b</b>) Crack pattern, relaxation time equal to 0.0001 s. (<b>c</b>) Crack pattern, relaxation time equal to 0.001 s.</p> Full article ">Figure 12
<p>Geometry and main reinforcement for the case of elements with the same cross section heights; dimensions in (mm).</p> Full article ">Figure 13
<p>Geometry and main reinforcement for the case of elements with different cross section heights; dimension in (mm).</p> Full article ">Figure 14
<p>Geometry and main reinforcement for the case of elements with different cross section heights; dimensions in (mm).</p> Full article ">Figure 15
<p>Loading scheme for the case of elements with different cross section heights; dimensions in (mm).</p> Full article ">Figure 16
<p>Truss schemes assumed for each reinforcement detail in the S&amp;T method; dimensions in (mm).</p> Full article ">Figure 16 Cont.
<p>Truss schemes assumed for each reinforcement detail in the S&amp;T method; dimensions in (mm).</p> Full article ">Figure 17
<p>Truss schemes assumed for each reinforcement detail in the S&amp;T method; dimensions in (mm).</p> Full article ">Figure 17 Cont.
<p>Truss schemes assumed for each reinforcement detail in the S&amp;T method; dimensions in (mm).</p> Full article ">Figure 18
<p>Meshing of concrete and reinforcing steel (detail NO. 7) and analyzed nodal displacement.</p> Full article ">Figure 19
<p>Boundary conditions and ideally elastic fragments of reinforcement (in red).</p> Full article ">Figure 20
<p>Equivalent plastic strains in tension PEEQT for chosen reinforcement details in the plane stress state.</p> Full article ">Figure 21
<p>Nodal displacement vs. loading parameter in the plane stress state.</p> Full article ">Figure 22
<p>Crack width vs. loading parameter in the plane stress state.</p> Full article ">Figure 23
<p>Meshing of frame corner and analyzed nodal displacement for the case of elements with different cross section heights.</p> Full article ">Figure 24
<p>Equivalent plastic strains in tension PEEQT for the chosen reinforcement details in the plane stress state.</p> Full article ">Figure 25
<p>Nodal displacement vs. loading parameter in the plane stress state.</p> Full article ">Figure 26
<p>Crack width vs. loading parameter in the plane stress state.</p> Full article ">Figure 27
<p>Corner efficiency factor vs. reinforcement ratio—detail No. 4, (<b>a</b>) the same section heights, (<b>b</b>) different section heights.</p> Full article ">Figure 28
<p>Nodal displacement vs. loading parameter for different diagonal reinforcement areas, (<b>a</b>) in the plane stress state, (<b>b</b>) in the plane strain state.</p> Full article ">Figure 29
<p>DAMAGET maps in the plane stress state for different areas of diagonal reinforcement: (<b>a</b>) 2ϕ8 mm, (<b>b</b>) 2ϕ12 mm, (<b>c</b>) 2ϕ16 mm bars.</p> Full article ">Figure 30
<p>Crack width for different areas of diagonal reinforcement, (<b>a</b>) the plane stress state, (<b>b</b>) the plane strain state.</p> Full article ">Figure 31
<p>Boundary conditions (<b>a</b>) and reinforcement (<b>b</b>) of modeled RV9 specimen.</p> Full article ">Figure 32
<p>Meshing of modeled RV9 specimen (<b>a</b>) with zoomed corner zone (<b>b</b>).</p> Full article ">Figure 33
<p>Force–displacement relationships obtained in FEM analysis and laboratory tests.</p> Full article ">Figure 34
<p>(<b>a</b>–<b>d</b>) PEEQT maps in FEM analysis in four selected time steps.</p> Full article ">Figure 35
<p>A sketch of the crack pattern obtained in Johansson’s laboratory tests (reprinted with permission from Johansson [<a href="#B13-materials-14-03438" class="html-bibr">13</a>], Copyright 2000, M. Johansson).</p> Full article ">
16 pages, 5658 KiB  
Article
Fast Solution Synthesis of NiO-Gd0.1Ce0.9O1.95 Nanocomposite via Different Approach: Influence of Processing Parameters and Characterizations
by Jorge Durango-Petro, Christopher Salvo, Jonathan Usuba, Gonzalo Abarzua, Felipe Sanhueza and Ramalinga Viswanathan Mangalaraja
Materials 2021, 14(12), 3437; https://doi.org/10.3390/ma14123437 - 21 Jun 2021
Cited by 5 | Viewed by 2546
Abstract
The synthesis of the nickel oxide-gadolinium doped ceria (NiO-GDC with 65:35 wt. %) nanocomposite powders with a stoichiometry of Gd0.1Ce0.9O1.95 was performed via fast solution combustion technique; using three different mixing methods: (i) CM (metal cations in an [...] Read more.
The synthesis of the nickel oxide-gadolinium doped ceria (NiO-GDC with 65:35 wt. %) nanocomposite powders with a stoichiometry of Gd0.1Ce0.9O1.95 was performed via fast solution combustion technique; using three different mixing methods: (i) CM (metal cations in an aqueous solution), (ii) HM (hand mortar), and (iii) BM (ball milling). The nanocomposite powders were calcined at 700 °C for 2 h and characterized by Transmission Electron Microscopy (TEM), X-ray fluorescence (XRF), and X-ray Diffraction XRD. The TEM and XRD analyses evidenced the well-dispersed NiO and GDC crystallites with the absence of secondary phases, respectively. Later, the calcined powders (NiO-GDC nanocomposites) were compacted and sintered at 1500 °C for 2 h. The microhardness of the sintered nanocomposites varies in accordance with the synthesis approach: a higher microhardness of 6.04 GPa was obtained for nanocomposites synthesized through CM, while 5.94 and 5.41 GPa were obtained for ball-milling and hand-mortar approach, respectively. Furthermore, it was observed that regardless of the long time-consuming ball-milling process with respect to the hand mortar, there was no significant improvement in the electrical properties. Full article
(This article belongs to the Special Issue Novel Ceramic Materials for the Energy Transition)
►▼ Show Figures

Figure 1

Figure 1
<p>(<b>a</b>) XRD patterns of the NiO-GDC calcined powders obtained by CM, BM, and HM methods; (<b>b</b>,<b>c</b>) enlarged views of selected diffraction peaks of the CM-p for GDC and NiO phase, respectively, (p represents the calcined powder).</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) TEM images and (<b>c</b>) SAED pattern of NiO powders.</p> Full article ">Figure 3
<p>(<b>a</b>,<b>b</b>) TEM images and (<b>c</b>) SAED pattern of GDC powders.</p> Full article ">Figure 4
<p>(<b>a</b>,<b>b</b>) TEM images and (<b>c</b>) SAED pattern of NiO-GDC nanocomposites obtained by CM method.</p> Full article ">Figure 5
<p>(<b>a</b>) TEM image and (<b>b</b>,<b>c</b>) spot SAED patterns of NiO-GDC nanocomposites obtained by conventional BM method.</p> Full article ">Figure 6
<p>XRD patterns of the NiO-GDC sintered discs obtained by CM, BM, and HM methods (d represents the sintered disc).</p> Full article ">Figure 7
<p>SEM images of the fracture surfaces for the sintered samples processed through (<b>a</b>,<b>b</b>) CM, (<b>d</b>,<b>e</b>) BM, and (<b>g</b>,<b>h</b>) HM methods. Grain size distribution for the sintered samples processed through (<b>c</b>) CM, (<b>f</b>) BM, and (<b>i</b>) HM methods.</p> Full article ">Figure 8
<p>Impedance spectra at 350 °C for the sintered samples processed through CM (red), BM (blue), and HM (black) methods.</p> Full article ">Figure 9
<p>Arrhenius plots of total conductivity for the sintered samples processed through CM (red), BM (blue), and HM (black) methods.</p> Full article ">
15 pages, 2665 KiB  
Article
Selenite Substituted Calcium Phosphates: Preparation, Characterization, and Cytotoxic Activity
by Antonia Ressler, Maja Antunović, Matija Cvetnić, Marica Ivanković and Hrvoje Ivanković
Materials 2021, 14(12), 3436; https://doi.org/10.3390/ma14123436 - 21 Jun 2021
Cited by 12 | Viewed by 2853
Abstract
The aim of this study was to prepare a biomimetic selenium substituted calcium phosphate system for potential application in osteosarcoma therapy. Calcium phosphate (CaP) systems substituted with selenite ions were prepared by the wet precipitation method, using biogenic CaCO3 (derived from cuttlefish [...] Read more.
The aim of this study was to prepare a biomimetic selenium substituted calcium phosphate system for potential application in osteosarcoma therapy. Calcium phosphate (CaP) systems substituted with selenite ions were prepared by the wet precipitation method, using biogenic CaCO3 (derived from cuttlefish bone), CO(NH2)2-H3PO4, and Na2SeO3·5H2O as reagents. Starting reaction mixtures were prepared based on the formula for selenite-substituted hydroxyapatite, Ca10(PO4)6-x(SeO3)x(OH)2, with Ca/(P + Se) molar ratio of 1.67 and Se/(P + Se) molar ratio of: 0, 0.01, 0.05, and 0.10, respectively. The prepared CaP powders were characterized by Fourier transform infrared spectrometry, elemental analysis, scanning electron microscopy, X-ray powder diffraction analysis and Rietveld refinement studies. Phase transformation and ion release were analyzed during 7 days of incubation in simulated body fluid at 37 °C. The metabolic activity of healthy and osteosarcoma cell lines was assessed by cell cytotoxicity and viability test. The as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP). Along with the selenite substitution, the presence of Sr2+, Na+, and Mg2+ was detected as a result of using cuttlefish bone as a precursor for Ca2+ ions. Inductively coupled plasma mass spectrometry analysis showed that the Se/(P + Se) molar ratios of selenite substituted powders are lower than the nominal ratios. Heat treated powders were composed of HAp, α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). Doping CaP structure with selenite ions improves the thermal stability of HAp. The powder with the Se/(P + Se) molar ratio of 0.007 showed selective toxicity to cancer cells. Full article
(This article belongs to the Special Issue Collection of Papers in Materials Science from Croatia)
►▼ Show Figures

Figure 1

Figure 1
<p>Rietveld analysis of powder X-ray diffraction data (<b>A</b>) and X-ray diffraction analysis patterns (<b>B</b>) for as-prepared non-substituted (CaP_Se0) and Se-substituted (CaP_Se1, CaP_Se5, CaP_Se10) CaP powders. Observed (blue empty circles) and calculated (red solid lines) intensities. The difference between the observed and calculated intensities is plotted below the profile (R<sub>wp</sub> &lt; 10%; R<sub>exp</sub> &lt; 3%). Bragg positions of hydroxyapatite, octacalcium phosphate, and silicon (standard) are marked below each pattern.</p> Full article ">Figure 2
<p>Unit cell parameters of HAp phase as a function of Se/(P + Se) molar ratio in as-prepared powders (black circles) compared to the literature data [<a href="#B20-materials-14-03436" class="html-bibr">20</a>] (empty circles).</p> Full article ">Figure 3
<p>Rietveld analysis pattern of powder diffraction data for heat treated CaP powders. Observed (blue empty circles) and calculated (red solid lines) intensities. The difference between the experimental and calculated intensities is plotted below the profile (R<sub>wp</sub> &lt; 11%; R<sub>exp</sub> &lt; 3%). Bragg positions of hydroxyapatite, β-tricalcium phosphate, α-tricalcium phosphate, and silicon (standard) are marked below each pattern.</p> Full article ">Figure 4
<p>FTIR spectra of as-prepared (<b>A</b>) and heat-treated (<b>B</b>) non-substituted (CaP_Se0) and Se-substituted (CaP_Se1, CaP_Se5, CaP_Se10) CaP powders.</p> Full article ">Figure 5
<p>SEM micrographs of as-prepared CaP powders. Scale bars: 5 μm.</p> Full article ">Figure 6
<p>Released SeO<sub>3</sub><sup>2−</sup> ion concentration during 7 days of incubation at 37 °C.</p> Full article ">Figure 7
<p>The effect of supernatant of calcium phosphate powders on cell viability (%) of HEK 293 (<b>A</b>) and U2OS (<b>B</b>) cells, respectively. The significant difference between two groups: ** (<span class="html-italic">p</span> &lt; 0.05), * (<span class="html-italic">p</span> &lt; 0.01).</p> Full article ">
19 pages, 11735 KiB  
Article
NBT-Pluronic F-127 Hydrogels Printed on Flat Textiles as UV Radiation Sensors
by Elżbieta Sąsiadek, Malwina Jaszczak, Joanna Skwarek and Marek Kozicki
Materials 2021, 14(12), 3435; https://doi.org/10.3390/ma14123435 - 21 Jun 2021
Cited by 10 | Viewed by 2340
Abstract
This work reports on the surface-modified woven fabrics for use as UV radiation sensors. The cotton and polyamide fabrics were printed with radiochromic hydrogels using a screen-printing method. The hydrogels used as a printing paste were composed of water, poly(ethylene oxide)-block-poly(propylene [...] Read more.
This work reports on the surface-modified woven fabrics for use as UV radiation sensors. The cotton and polyamide fabrics were printed with radiochromic hydrogels using a screen-printing method. The hydrogels used as a printing paste were composed of water, poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127) as a gel matrix and nitro blue tetrazolium chloride as a radiation-sensitive compound. The development of the hydrogels’ colour occurs after exposure to UV radiation and its intensity increases with increasing absorbed dose. The features of the NBT-Pluronic F-127 radiochromic hydrogels and the fabrics printed with the hydrogels were examined using UV-Vis and reflectance spectrophotometry as well as scanning electron microscopy (SEM). The effects of NBT concentration and UV radiation type (UVA, UVB, UVC) on dose responses of the hydrogels and printed fabrics were also examined. The results obtained reveal that the fabrics printed with NBT-Pluronic F-127 hydrogels can be potentially useful as UV radiation sensors. Full article
(This article belongs to the Section Smart Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic illustration of the screen-printing and irradiation process of flat woven fabric.</p> Full article ">Figure 1 Cont.
<p>Schematic illustration of the screen-printing and irradiation process of flat woven fabric.</p> Full article ">Figure 2
<p>The absorbance spectra of NBT-Pluronic F-127 hydrogels with 1 g/dm<sup>3</sup> (<b>a</b>–<b>c</b>), 2 g/dm<sup>3</sup> (<b>d</b>–<b>f</b>) and 5 g/dm<sup>3</sup> (<b>g</b>–<b>i</b>) NBT irradiated with UVA (<b>a</b>,<b>d</b>,<b>g</b>), UVB (<b>b</b>,<b>e</b>,<b>h</b>) and UVC (<b>c</b>,<b>f</b>,<b>i</b>) radiation in the dose range of 0–3 J/cm<sup>2</sup>.</p> Full article ">Figure 3
<p>The dose responses of NBT-Pluronic F-127 hydrogels containing 1 g/dm<sup>3</sup> (<b>a</b>), 2 g/dm<sup>3</sup> (<b>b</b>) and 5 g/dm<sup>3</sup> (<b>c</b>) NBT irradiated with UVA, UVB and UVC radiation in the dose range of 0–3 J/cm<sup>2</sup> with corresponding photographs illustrating the samples’ colour changes after irradiation (absorbed doses: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 0.7, 1, 1.5, 2 and 3 J/cm<sup>2</sup>, from left to right).</p> Full article ">Figure 4
<p>The dose responses of NBT-Pluronic F-127 hydrogels containing 1, 2 and 5 g/dm<sup>3</sup> NBT irradiated with UVB radiation in the dose range of 0–3 J/cm<sup>2</sup> with corresponding photographs illustrating the samples’ colour changes after irradiation with doses 0, 0.07, 0.7 and 3 J/cm<sup>2</sup> (from <b>left</b> to <b>right</b>).</p> Full article ">Figure 5
<p>Dependence of the reflectance of light at 530 nm versus absorbed dose (<b>a</b>) and stability over time (<b>b</b>) for the cotton and polyamide fabrics printed with NBT-Pluronic F-127 hydrogel and irradiated with UVB radiation. The values of light reflectance for non-printed cotton and polyamide woven fabrics was: 79.60 and 72.60, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) Non-printed polyamide (<b>a</b>) and cotton (<b>b</b>) fabrics after RGBreader analysis; (<b>c</b>): The scale for the assessment of the unevenness of the RGB channel on the textiles’ surface (RGB values 0: ideal black; 255: ideal white) [<a href="#B20-materials-14-03435" class="html-bibr">20</a>].</p> Full article ">Figure 7
<p>Green channels maps (second column) for polyamide (<b>a</b>) and cotton (<b>b</b>) fabrics printed with NBT-Pluronic F-127 hydrogel and irradiated with 2 J/cm<sup>2</sup> of UVB radiation (first column).</p> Full article ">Figure 8
<p>(<b>a</b>,<b>b</b>) Analysis of polyamide and cotton fabrics—the green RGB channel profiles (1 pix = 0.1 mm) for (i) non-printed, (ii) printed and non-irradiated and (iii) printed and irradiated with 0.5 J/cm<sup>2</sup> of UVB irradiation polyamide (<b>a</b>) and cotton (<b>b</b>) fabrics; (<b>c</b>): Comparison of polyamide vs. cotton fabrics irradiated with 0.5 J/cm<sup>2</sup> of UVB.</p> Full article ">Figure 8 Cont.
<p>(<b>a</b>,<b>b</b>) Analysis of polyamide and cotton fabrics—the green RGB channel profiles (1 pix = 0.1 mm) for (i) non-printed, (ii) printed and non-irradiated and (iii) printed and irradiated with 0.5 J/cm<sup>2</sup> of UVB irradiation polyamide (<b>a</b>) and cotton (<b>b</b>) fabrics; (<b>c</b>): Comparison of polyamide vs. cotton fabrics irradiated with 0.5 J/cm<sup>2</sup> of UVB.</p> Full article ">Figure 9
<p>SEM images of the non-printed cotton fabric (<b>a</b>), non-printed polyamide fabric (<b>b</b>), cotton fabric printed with NBT-Pluronic F-127 hydrogel (<b>c</b>) and polyamide fabric printed with NBT-Pluronic F-127 hydrogel (<b>d</b>).</p> Full article ">Figure 10
<p>The pattern design (<b>a</b>); the pattern printed on cotton fabric with NBT-Pluronic F-127 hydrogel containing 1 g/dm<sup>3</sup> NBT, non-irradiated (<b>b</b>) and irradiated with 0.05 J/cm<sup>2</sup> (<b>c</b>) and 0.7 J/cm<sup>2</sup> (<b>d</b>) of UVB radiation; an example of the location of the pattern on the protective clothing (<b>e</b>).</p> Full article ">
18 pages, 11302 KiB  
Article
Towards Enhancing the Potential of Injection Molding Tools through Optimized Close-Contour Cooling and Additive Manufacturing
by Sebastian Gries, Guillaume Meyer, Andreas Wonisch, Reinhard Jakobi and Christian Mittelstedt
Materials 2021, 14(12), 3434; https://doi.org/10.3390/ma14123434 - 21 Jun 2021
Cited by 6 | Viewed by 2722
Abstract
This work deals with the parametric optimization of the position and form of a conformal cooling used in the injection molding industry. Based on a literature survey, an optimization routine concerning the parameter optimization of cooling system designs was developed and implemented with [...] Read more.
This work deals with the parametric optimization of the position and form of a conformal cooling used in the injection molding industry. Based on a literature survey, an optimization routine concerning the parameter optimization of cooling system designs was developed and implemented with the help of the software package Moldflow. The main objective of the optimization is to reduce the cooling time; the second is to obtain an optimized homogeneous temperature distribution over the complete tool surface. To enable a comparison of the new close-contour solution with a classical manufacturing process, an optimized cooling system simulation, based on a conventional manufacturing solution, was established. It can be shown that the optimized close-contour cooling design offers significant advantages that cannot be exploited using classical manufacturing. Finally, the additive manufacturing of a prototype in the framework of powder bed fusion is documented as a proof of concept. Full article
(This article belongs to the Special Issue Polymers and Injection Molding Simulation)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic representation of a conventional cooling system (<b>left</b>) and a close-contour cooling system (<b>right</b>).</p> Full article ">Figure 2
<p>The Powder Bed Fusion (PBF) process.</p> Full article ">Figure 3
<p>The reference molded part.</p> Full article ">Figure 4
<p>Experimental set-up: The injection molding tool (<b>left</b>); relevant detail of the tool for the cooling system (<b>right</b>). In the picture on the right, the molded part in the cavity is red; the mold core is dark grey; the inner core is light grey on the right; the die is light grey on the left. The observable cooling channels are in blue and divided by pass partition plates in yellow.</p> Full article ">Figure 5
<p>Sectional view of the solid mold core; cooling system consisting of channels with circular cross-sections, divided by pass partition plates. The cooling system consists of eight channels.</p> Full article ">Figure 6
<p>Model sketch of the initial configuration (mesh for tooling is omitted), cooling channels are given in blue; channels including pass partition plates are highlighted in yellow.</p> Full article ">Figure 7
<p>CAD model of the mold core (<b>left</b>), initial cooling system (<b>middle</b>), channel axes (<b>right</b>).</p> Full article ">Figure 8
<p>Graphical representation of the design variables for the optimization of the conventional cooling system.</p> Full article ">Figure 9
<p>Initial close-contour cooling system in top view (<b>left</b>) and rib region parametrization (<b>middle</b> to <b>right</b>).</p> Full article ">Figure 10
<p>Averaged temperature distribution on the surfaces of the mold part for the initial configuration: Upper surface (<b>left</b>), lower surface (<b>right</b>).</p> Full article ">Figure 11
<p>Initial configuration (<b>left</b>) and optimized configuration (<b>right</b>) of the conventional cooling system.</p> Full article ">Figure 12
<p>Temperature distribution on the lower surface of the cavity: initial configuration (<b>left</b>), optimized configuration (<b>right</b>).</p> Full article ">Figure 13
<p>Mold part and final optimized configuration of the close-contour cooling system.</p> Full article ">Figure 14
<p>Temperature distribution in the tool cavity for close-contour cooling: a comparison between initial configuration (<b>left</b>) and optimized configuration (<b>right</b>).</p> Full article ">Figure 15
<p>Temperature distribution on the surfaces of the mold part for optimized close-contour cooling.</p> Full article ">Figure 16
<p>Temperature of the cooling medium for the initial (<b>left</b>) and optimized (<b>right</b>) close-contour cooling system.</p> Full article ">Figure 17
<p>Graphical comparison of the temperature distribution on the lower tool surface: initial configuration (<b>a</b>) and optimized conventional configuration (<b>b</b>); initial close-contour configuration (<b>c</b>) and optimized close-contour cooling system (<b>d</b>).</p> Full article ">Figure 18
<p>3D sectional model of the injection molding tool from two perspectives.</p> Full article ">Figure 19
<p>Sketch of the injection molding tool on the build platform of the PBF system.</p> Full article ">Figure 20
<p>Support Structures.</p> Full article ">Figure 21
<p>The final manufactured injection molding tool with the principle part (<b>left</b>) and sectional part exhibiting the integrated cooling channels (<b>right</b>).</p> Full article ">
18 pages, 7150 KiB  
Article
Effect of Co Substitution and Thermo-Magnetic Treatment on the Structure and Induced Magnetic Anisotropy of Fe84.5−xCoxNb5B8.5P2 Nanocrystalline Alloys
by Aleksandra Kolano-Burian, Przemyslaw Zackiewicz, Agnieszka Grabias, Anna Wojcik, Wojciech Maziarz, Maciej Szlezynger, Patryk Wlodarczyk, Maciej Kowalczyk and Lukasz Hawelek
Materials 2021, 14(12), 3433; https://doi.org/10.3390/ma14123433 - 21 Jun 2021
Cited by 7 | Viewed by 2435
Abstract
In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe84.5-xCoxNb5B8.5P2 (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on [...] Read more.
In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe84.5-xCoxNb5B8.5P2 (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on a semi-industrial scale by the melt-spinning technique. The subsequent nanocrystallization processes were carried out under different conditions (with/without magnetic field). The comprehensive studies have been carried out using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hysteresis loop analyses, vibrating sample magnetometry and Mössbauer spectroscopy. Moreover, the frequency (up to 300 kHz) dependence of power losses and permeability at a magnetic induction up to 0.9 T was investigated. On the basis of some of the results obtained, we calculated the values of the activation energies and the induced magnetic anisotropies. The X-ray diffraction results confirm the surface crystallization effect previously observed for phosphorous-containing alloys. The in situ microscopic observations of crystallization describe this process in detail in accordance with the calorimetry results. Furthermore, the effect of Co content on the phase composition and the influence of annealing in an external magnetic field on magnetic properties, including the orientation of the magnetic spins, have been studied using various magnetic techniques. Finally, nanocrystalline Fe64.5Co20Nb5B8.5P2 cores were prepared after transverse thermo-magnetic heat treatment and installed in industrially available portable heating equipment. Full article
(This article belongs to the Special Issue Nanocomposite Magnetic Materials for Energy Conversion)
►▼ Show Figures

Figure 1

Figure 1
<p>Melt spinning casting setup used in the research, 50.8 mm wide ribbon obtained during the casting, exemplary wound cores prepared for annealing.</p> Full article ">Figure 2
<p>Differential scanning calorimetry curves of Fe<sub>84.5-x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> (x = 0–20 at.%) alloys. The heating rate is 20 °C/min.</p> Full article ">Figure 3
<p>(<b>a</b>) The activation energy for the crystallization process derived from the FWO model related to the progress of crystallization; (<b>b</b>) The average values of the activation energies derived from the Kissinger model.</p> Full article ">Figure 4
<p>The X-ray diffraction patterns of Fe<sub>84.5</sub><sub>−x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> ribbons in as-spun state.</p> Full article ">Figure 5
<p>A set of BF images recorded for the Fe<sub>84.5</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> ribbon during in situ heat treatment up to 600 °C.</p> Full article ">Figure 6
<p>A set of BF images recorded for the Fe<sub>64.5</sub>Co<sub>20</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> ribbon during in situ heat treatment up to 600 °C.</p> Full article ">Figure 7
<p>A set of BF, DF and SADP images for as-spun and in situ heat-treated Fe<sub>84.5</sub><sub>−x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> (x = 0, 5, 10, 15, 20 at.%) ribbons.</p> Full article ">Figure 8
<p>The example of BF and DF images of the Fe<sub>64.5</sub>Co<sub>20</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> ribbon taken at 500 and 600 °C.</p> Full article ">Figure 9
<p>HREM image with corresponding FFT and IFFT taken from marked areas of the Fe<sub>69.5</sub>Co<sub>5</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> ribbon.</p> Full article ">Figure 10
<p>STEM-HAADF image with elemental mapping of Fe<sub>69.5</sub>Co<sub>5</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub>.</p> Full article ">Figure 11
<p>M vs. T curves of Fe<sub>84.5</sub><sub>−x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> (x = 0–20 at.%).</p> Full article ">Figure 12
<p>(<b>a</b>) Hysteresis loops for a Fe<sub>64.5</sub>Co<sub>20</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> core after annealing at 455 °C without magnetic field (black) and in presence of a transverse magnetic field 140 kA/m (green) and on insert after annealing at 525 °C without magnetic field (black) and in presence of a transverse magnetic field 140 kA/m (green); (<b>b</b>) Hysteresis loops for Fe<sub>84.5</sub><sub>−x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> (<span class="html-italic">x</span> = 0–20 at.%) cores annealed at 525 °C in a presence of transverse magnetic field 140 kA/m.</p> Full article ">Figure 13
<p>Mössbauer spectra of Fe<sub>84.5</sub><sub>−x</sub>Co<sub>x</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> alloys annealed at 525 °C for 20 min without (left column) and with (right column) the magnetic field of 125 kA/m.</p> Full article ">Figure 14
<p>(<b>a</b>) Distributions of hyperfine fields determined from the Mössbauer spectra in <a href="#materials-14-03433-f013" class="html-fig">Figure 13</a> (left column); (<b>b</b>) Distributions of hyperfine fields determined from the Mössbauer spectra in <a href="#materials-14-03433-f013" class="html-fig">Figure 13</a> (right column).</p> Full article ">Figure 15
<p>(<b>a</b>) Core losses (P<sub>s</sub>) for the Fe<sub>64.5</sub>Co<sub>20</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> core as a function of magnetization (B<sub>m</sub>) for 10–300 kHz; (<b>b</b>) magnetic permeability (µ) for the Fe<sub>64.5</sub>Co<sub>20</sub>Nb<sub>5</sub>B<sub>8.5</sub>P<sub>2</sub> core as a function of frequency for B<sub>m</sub> = 0.1–0.5 T.</p> Full article ">Figure 16
<p>EFD Induction mobile induction heating equipment Miniac [<a href="#B28-materials-14-03433" class="html-bibr">28</a>].</p> Full article ">
13 pages, 3449 KiB  
Article
Feasibility of Cobalt-Free Nanostructured WC Cutting Inserts for Machining of a TiC/Fe Composite
by Edwin Gevorkyan, Mirosław Rucki, Tadeusz Sałaciński, Zbigniew Siemiątkowski, Volodymyr Nerubatskyi, Wojciech Kucharczyk, Jarosław Chrzanowski, Yuriy Gutsalenko and Mirosław Nejman
Materials 2021, 14(12), 3432; https://doi.org/10.3390/ma14123432 - 21 Jun 2021
Cited by 21 | Viewed by 2311
Abstract
The paper presents results of investigations on the binderless nanostructured tungsten carbide (WC) cutting tools fabrication and performance. The scientific novelty includes the description of some regularities of the powder consolidation under electric current and the subsequent possibility to utilize them for practical [...] Read more.
The paper presents results of investigations on the binderless nanostructured tungsten carbide (WC) cutting tools fabrication and performance. The scientific novelty includes the description of some regularities of the powder consolidation under electric current and the subsequent possibility to utilize them for practical use in the fabrication of cutting tools. The sintering process of WC nanopowder was performed with the electroconsolidation method, which is a modification of spark plasma sintering (SPS). Its advantages include low temperatures and short sintering time which allows retaining nanosize grains of ca. 70 nm, close to the original particle size of the starting powder. In respect to the application of the cutting tools, pure WC nanostructure resulted in a smaller cutting edge radius providing a higher quality of TiC/Fe machined surface. In the range of cutting speeds, vc = 15–40 m/min the durability of the inserts was 75% of that achieved by cubic boron nitride ones, and more than two times better than that of WC-Co cutting tools. In additional tests of machining 13CrMo4 material at an elevated cutting speed of vc = 100 m/min, binderless nWC inserts worked almost three times longer than WC-Co composites. Full article
(This article belongs to the Collection Machining and Manufacturing of Alloys and Steels)
►▼ Show Figures

Figure 1

Figure 1
<p>Photo of the nano-crystalline binderless tungsten carbide (nWC) cutting inserts.</p> Full article ">Figure 2
<p>Measurement of hardness and fracture toughness: (<b>a</b>) Experimental stand; (<b>b</b>) Indentation in the brittle material; (<b>c</b>) Radial cracks.</p> Full article ">Figure 3
<p>XRD of the WolCar obtained with electroconsolidation at <span class="html-italic">T</span> = 1700 °C and <span class="html-italic">P</span> = 45 MPa, for 2 min.</p> Full article ">Figure 4
<p>The fracture surfaces of sintered tungsten carbide (WC): (<b>a</b>) and (<b>b</b>) pure WC (WolCar) using the electroconsolidation method at <span class="html-italic">T =</span> 1700 °C and <span class="html-italic">P</span> = 35 MPa during 3 min; (<b>c</b>) Standard blend of 8 wt.% Co and 92 wt.% of WC using conventional vacuum sintering method at <span class="html-italic">T =</span> 1350 °C for 1 h, the surface without etching; (<b>d</b>) The same as (<b>c</b>), but after etching.</p> Full article ">Figure 5
<p>Quality of the TiC/Fe composite surface machined with different inserts: (<b>a</b>) BK6; (<b>b</b>) WolCar.</p> Full article ">Figure 6
<p>WC sintering power consumption <span class="html-italic">P<sub>r</sub></span> versus temperature.</p> Full article ">Figure 7
<p>Pinch effect in the sintered powder volume: (<b>a</b>) Uniform current distribution along cross-sectional area; (<b>b</b>) Conductor with the surface current.</p> Full article ">Figure 8
<p>Effect of the process parameters on the characteristics of sintered WC: (<b>a</b>) Impact of the electric power <span class="html-italic">P<sub>e</sub></span> on hardness <span class="html-italic">HV</span> and fracture toughness <span class="html-italic">K<sub>IC</sub></span>; (<b>b</b>) Changes of the current density <span class="html-italic">I<sub>e</sub></span> and temperature <span class="html-italic">T</span> during the process.</p> Full article ">Figure 9
<p>Durability of cutting inserts at different cutting speeds when machining TiC/Fe composite: 1—WolCar, 2—CBN, 3—BK8.</p> Full article ">Figure 10
<p>Flank wear of WolCar cutting inserts: (<b>a</b>) Photo; (<b>b</b>) SEM image.</p> Full article ">
13 pages, 3151 KiB  
Article
A Study on Heat Storage and Dissipation Efficiency at Permeable Road Pavements
by Ching-Che Yang, Jun-Han Siao, Wen-Cheng Yeh and Yu-Min Wang
Materials 2021, 14(12), 3431; https://doi.org/10.3390/ma14123431 - 21 Jun 2021
Cited by 11 | Viewed by 2350
Abstract
The main contributing factor of the urban heat island (UHI) effect is caused by daytime heating. Traditional pavements in cities aggravate the UHI effect due to their heat storage and volumetric heat capacity. In order to alleviate UHI, this study aims to understand [...] Read more.
The main contributing factor of the urban heat island (UHI) effect is caused by daytime heating. Traditional pavements in cities aggravate the UHI effect due to their heat storage and volumetric heat capacity. In order to alleviate UHI, this study aims to understand the heating and dissipating process of different types of permeable road pavements. The Ke Da Road in Pingtung County of Taiwan has a permeable pavement materials experiment zone with two different section configurations which were named as section I and section II for semi-permeable pavement and fully permeable pavement, respectively. The temperature sensors were installed during construction at the depths of the surface course (0 cm and 5 cm), base course (30 cm and 55 cm) and subgrade (70 cm) to monitor the temperature variations in the permeable road pavements. Hourly temperature and weather station data in January and June 2017 were collected for analysis. Based on these collected data, heat storage and dissipation efficiencies with respect to depth have been modelled by using multi regression for the two studied pavement types. It is found that the fully permeable pavement has higher heat storage and heat dissipation efficiencies than semi-permeable pavement in winter and summer monitoring period. By observing the regressed model, it is found that the slope of the model lines are almost flat after the depth of 30 cm. Thus, from the view point of UHI, one can conclude that the reasonable design depth of permeable road pavement could be 30 cm. Full article
(This article belongs to the Special Issue Temperature Reduction Technologies Meet Asphalt Pavement: Green and Sustainability)
►▼ Show Figures

Figure 1

Figure 1
<p>Location of the study area.</p> Full article ">Figure 2
<p>The pavement designs of this study.</p> Full article ">Figure 3
<p>Sketch for the sensor locations in the study.</p> Full article ">Figure 4
<p>Temperature distribution at each depth of Section I from the 22nd to the 28th of January.</p> Full article ">Figure 5
<p>Temperature distribution at each depth of Section II from the 22nd to the 28th of January.</p> Full article ">Figure 6
<p>Temperature distribution at each depth of Section I from the 21st to the 25th of June.</p> Full article ">Figure 7
<p>Temperature distribution at each depth of Section II from the 21st to the 25th of June.</p> Full article ">Figure 8
<p>Relationships between heat storage efficiency verse permeable road pavements depth (<b>a</b>) Model for semi-permeable road pavement. (<b>b</b>) Model for fully permeable road pavement.</p> Full article ">Figure 9
<p>Relationships between heat dissipation efficiency verse permeable road pavements depth (<b>a</b>) Model for semi-permeable road pavement. (<b>b</b>) Model for fully permeable road pavement.</p> Full article ">
13 pages, 5082 KiB  
Article
Microstructure and Mechanical Properties of Modern 11%Cr Heat-Resistant Steel Weld Joints
by Grzegorz Golański, Jacek Słania, Marek Sroka, Paweł Wieczorek, Michał Urzynicok and Ryszard Krawczyk
Materials 2021, 14(12), 3430; https://doi.org/10.3390/ma14123430 - 21 Jun 2021
Cited by 3 | Viewed by 2060
Abstract
In addition to good high-temperature creep resistance and adequate heat resistance, steels for the power industry must have, among other things, good weldability. Weldability of such steels is one of the criteria determining whether or not the material is suitable for applications in [...] Read more.
In addition to good high-temperature creep resistance and adequate heat resistance, steels for the power industry must have, among other things, good weldability. Weldability of such steels is one of the criteria determining whether or not the material is suitable for applications in the power industry. Therefore, when materials such as martensitic steel Thor 115 (T115) are introduced into the modern power industry, the quality and properties of welded joints must be assessed. The paper presents the results of metallographic and mechanical investigations of T115 martensitic steel welded joints. The analysis was carried out on joints welded with two filler metals: WCrMo91 (No. 1) and EPRI P87 (No. 2). The scope of the investigations included: microstructural investigations carried out using optical, scanning and transmission electron microscopy and mechanical testing, i.e., Vickers microhardness and hardness measurement, static tensile test and impact test. The macro- and microstructural investigations revealed correct structure of the weld, without welding imperfections. The microstructural investigations of joint No. 1 revealed a typical structure of this type of joint, i.e., the martensitic structure with numerous precipitates, while in joint No. 2, the so-called Nernst’s layers and δ-ferrite patches were observed in the weld fusion zone as well as the heat affected zone (HAZ). The mechanical properties of the test joints met the requirements for the base material. A slight influence of the δ-ferrite patch on the strength properties of joint No. 2 was observed, and its negative effect on the impact energy of HAZ was visible. Full article
(This article belongs to the Special Issue Electron Microscopy for Understanding of the Relationship between the Structure, the Properties and the Functions of Metals, Semiconductors, Ceramics, Carbon Materials, Composites and Coatings)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic of the specimens prepared for mechanical tests from the welded joint.</p> Full article ">Figure 2
<p>Microstructure of T115 steel in initial condition by scanning electron microscopy (SEM).</p> Full article ">Figure 3
<p>Microstructure of Thor 115 in initial condition by transmission electron microscopy (TEM).</p> Full article ">Figure 4
<p>Precipitates in Thor 115 steel in initial condition: (<b>a</b>) M<sub>23</sub>C<sub>6</sub>; (<b>b</b>) MC.</p> Full article ">Figure 5
<p>Macroscopic image of test joints: (<b>a</b>) joint No. 1; (<b>b</b>) joint No. 2; where: WM-weld; HAZ—heat affected zone; BM—basic material.</p> Full article ">Figure 6
<p>Microstructure of joint No. 1 in the vicinity of the fusion line—coarse grained heat-affected zone (CGHAZ).</p> Full article ">Figure 7
<p>The δ-ferrite in the vicinity of the fusion line—CGHAZ, joint No. 2; WM—weld metal.</p> Full article ">Figure 8
<p>Microstructure of fine-grained heat-affected zone (FGHAZ)/intercritical heat-affected zone (ICHAZ) in T115 steel joint—joint No. 1.</p> Full article ">Figure 9
<p>Microstructure of FGHAZ/ICHAZ in T115 steel joint—joint No. 2.</p> Full article ">Figure 10
<p>Nernst’s fingers in the weld of joint No. 2.</p> Full article ">Figure 11
<p>Hardness distribution profile across the cross-section of the joint welded with: (<b>a</b>) CrMo91, (<b>b</b>) EPRI P87.</p> Full article ">Figure 12
<p>Tensile strength of the test joints welded at a specific temperature.</p> Full article ">Figure 13
<p>Impact energy of the welded joints for both filler metals.</p> Full article ">
17 pages, 30863 KiB  
Article
On Coolant Flow Rate-Cutting Speed Trade-Off for Sustainability in Cryogenic Milling of Ti–6Al–4V
by Asif Iqbal, Guolong Zhao, Hazwani Suhaimi, Malik Muhammad Nauman, Ning He, Juliana Zaini and Wei Zhao
Materials 2021, 14(12), 3429; https://doi.org/10.3390/ma14123429 - 21 Jun 2021
Cited by 5 | Viewed by 2142
Abstract
Application of cryogenic fluids for efficient heat dissipation is gradually becoming part and parcel of titanium machining. Not much research is done to establish the minimum quantity of a cryogenic fluid required to sustain a machining process with respect to a given material [...] Read more.
Application of cryogenic fluids for efficient heat dissipation is gradually becoming part and parcel of titanium machining. Not much research is done to establish the minimum quantity of a cryogenic fluid required to sustain a machining process with respect to a given material removal rate. This article presents an experimental investigation for quantifying the sustainability of milling a commonly used titanium alloy (Ti–6Al–4V) by varying mass flow rates of two kinds of cryogenic coolants at various levels of cutting speed. The three cooling options tested are dry (no coolant), evaporative cryogenic coolant (liquid nitrogen), and throttle cryogenic coolant (compressed carbon dioxide gas). The milling sustainability is quantified in terms of the following metrics: tool damage, fluid cost, specific cutting energy, work surface roughness, and productivity. Dry milling carried out the at the highest level of cutting speed yielded the worst results regarding tool damage and surface roughness. Likewise, the evaporative coolant applied with the highest flow rate and at the lowest cutting speed was the worst performer with respect to energy consumption. From a holistic perspective, the throttle cryogenic coolant applied at the highest levels of mass flow rate and cutting speed stood out to be the most sustainable option. Full article
(This article belongs to the Special Issue Additive and Subtractive Manufacturing of Advanced Materials: Applications, Future Trends and Perspectives of Industry 4.0)
►▼ Show Figures

Figure 1

Figure 1
<p>The experimental setup: (<b>a</b>) the work plate, cutter, and force plate; (<b>b</b>) milling under evaporative cryogenic cooling; (<b>c</b>) the side- and end-mill cutter used in the experiments; and (<b>d</b>) milling under throttle cryogenic cooling.</p> Full article ">Figure 2
<p>Experimental results regarding tool wear, categorized with respect to the choice of coolant.</p> Full article ">Figure 3
<p>Micrographs of the milling cutters used in the following runs: (<b>a</b>) coolant = dry, <span class="html-italic">V</span><sub>c</sub> = 150 m/min; (<b>b</b>) coolant = evaporative, flow rate = 0.2 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min; (<b>c</b>) coolant = evaporative, flow rate = 0.6 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min; (<b>d</b>) coolant = throttle, flow rate = 0.4 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min; and (<b>e</b>) coolant = throttle, flow rate = 0.6 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min.</p> Full article ">Figure 4
<p>Experimental results regarding specific cutting energy.</p> Full article ">Figure 5
<p>Experimental results regarding work surface roughness.</p> Full article ">Figure 6
<p>Magnified views of the milled surfaces generated in the following runs: (<b>a</b>) coolant = dry, <span class="html-italic">V</span><sub>c</sub> = 50 m/min; (<b>b</b>) coolant = evaporative, flow rate = 0.2 kg/min, <span class="html-italic">V</span><sub>c</sub> = 50 m/min; (<b>c</b>) coolant = evaporative, flow rate = 0.4 kg/min, <span class="html-italic">V</span><sub>c</sub> = 150 m/min; (<b>d</b>) coolant = evaporative, flow rate = 0.6 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min; (<b>e</b>) coolant = throttle, flow rate = 0.2 kg/min, <span class="html-italic">V</span><sub>c</sub> = 50 m/min; and (<b>f</b>) coolant = throttle, flow rate = 0.6 kg/min, <span class="html-italic">V</span><sub>c</sub> = 200 m/min.</p> Full article ">Figure 7
<p>Experimental results regarding <span class="html-italic">F</span><sub>xy</sub> (resultant of the coplanar components) and <span class="html-italic">F</span><sub>z</sub> (the component acting along the tool’s axis).</p> Full article ">Figure 8
<p>The calculated values of specific coolant consumption cost against different combinations of cutting speed and coolant’s mass flow rate.</p> Full article ">
11 pages, 2337 KiB  
Article
Assessing the Interfacial Dynamic Modulus of Biological Composites
by Yaniv Shelef, Avihai Yosef Uzan, Ofer Braunshtein and Benny Bar-On
Materials 2021, 14(12), 3428; https://doi.org/10.3390/ma14123428 - 21 Jun 2021
Cited by 5 | Viewed by 2078
Abstract
Biological composites (biocomposites) possess ultra-thin, irregular-shaped, energy dissipating interfacial regions that grant them crucial mechanical capabilities. Identifying the dynamic (viscoelastic) modulus of these interfacial regions is considered to be the key toward understanding the underlying structure–function relationships in various load-bearing biological materials including [...] Read more.
Biological composites (biocomposites) possess ultra-thin, irregular-shaped, energy dissipating interfacial regions that grant them crucial mechanical capabilities. Identifying the dynamic (viscoelastic) modulus of these interfacial regions is considered to be the key toward understanding the underlying structure–function relationships in various load-bearing biological materials including mollusk shells, arthropod cuticles, and plant parts. However, due to the submicron dimensions and the confined locations of these interfacial regions within the biocomposite, assessing their mechanical characteristics directly with experiments is nearly impossible. Here, we employ composite-mechanics modeling, analytical formulations, and numerical simulations to establish a theoretical framework that links the interfacial dynamic modulus of a biocomposite to the extrinsic characteristics of a larger-scale biocomposite segment. Accordingly, we introduce a methodology that enables back-calculating (via simple linear scaling) of the interfacial dynamic modulus of biocomposites from their far-field dynamic mechanical analysis. We demonstrate its usage on zigzag-shaped interfaces that are abundant in biocomposites. Our theoretical framework and methodological approach are applicable to the vast range of biocomposites in natural materials; its essence can be directly employed or generally adapted into analogous composite systems, such as architected nanocomposites, biomedical composites, and bioinspired materials. Full article
(This article belongs to the Section Biomaterials)
►▼ Show Figures

Figure 1

Figure 1
<p>(<b>a</b>) Schematic examples of the interfacial regions in biocomposites: graded matrix properties, shaped matrix-reinforcement connection, and staggered matrix-reinforcement connection. (<b>b</b>) Mechanical modeling of a biocomposite segment (length <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mi>c</mi> </msub> </mrow> </semantics></math> and dynamic modulus <math display="inline"><semantics> <mrow> <msubsup> <mi>E</mi> <mi>c</mi> <mo>*</mo> </msubsup> </mrow> </semantics></math>), which includes an effective viscoelastic interface (length <math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mi>i</mi> </msub> </mrow> </semantics></math> and dynamic modulus <math display="inline"><semantics> <mrow> <msubsup> <mi>E</mi> <mi>i</mi> <mo>*</mo> </msubsup> </mrow> </semantics></math>) between adjacent elastic reinforcements (elastic modulus <math display="inline"><semantics> <mrow> <msub> <mi>E</mi> <mi>f</mi> </msub> </mrow> </semantics></math>).</p> Full article ">Figure 2
<p>The correspondence between <math display="inline"><semantics> <mrow> <msub> <mi>E</mi> <mi>i</mi> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>E</mi> <mi>c</mi> </msub> </mrow> </semantics></math> for various biocomposite configurations. The dashed lines indicate the theoretical results via Equation (4), and the symbols indicate the corresponding finite-element results (<a href="#app1-materials-14-03428" class="html-app">Table S1 in Supporting Information</a>). The colors indicate data sets with the same <math display="inline"><semantics> <mrow> <msub> <mi>k</mi> <mi>E</mi> </msub> </mrow> </semantics></math> parameter: black, red, and green correspond to <math display="inline"><semantics> <mrow> <msub> <mi>k</mi> <mi>E</mi> </msub> <mo>=</mo> <mn>0.1</mn> <mo>,</mo> <mo> </mo> <mo> </mo> <mn>0.3</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mn>0.8</mn> </mrow> </semantics></math>, respectively. The circle and square symbols represent different viscoelastic biocomposite configurations (<math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>c</mi> </msub> <mo>≠</mo> <mn>0</mn> </mrow> </semantics></math>), while the plus and asterisk symbols represent the corresponding biocomposite configurations, but with completely elastic properties (<math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>c</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math>).</p> Full article ">Figure 3
<p>The correspondence between <math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>i</mi> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>c</mi> </msub> </mrow> </semantics></math> for various biocomposite configurations. The dashed lines indicate the theoretical results via Equation (4), and the symbols indicate the corresponding finite-element results (<a href="#app1-materials-14-03428" class="html-app">Table S2 in Supporting Information</a>). The colors indicate data sets with the same <math display="inline"><semantics> <mrow> <msub> <mi>k</mi> <mi>δ</mi> </msub> </mrow> </semantics></math> parameter: black, red, and green correspond to <math display="inline"><semantics> <mrow> <msub> <mi>k</mi> <mi>δ</mi> </msub> <mo>=</mo> <mn>1.05</mn> <mo>,</mo> <mo> </mo> <mn>2.5</mn> </mrow> </semantics></math>, and <math display="inline"><semantics> <mn>5</mn> </semantics></math>, respectively. The range of <math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>i</mi> </msub> </mrow> </semantics></math> spans between completely elastic (<math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>0</mn> </mrow> </semantics></math>) and predominantly viscoelastic (<math display="inline"><semantics> <mrow> <mi>tan</mi> <msub> <mi>δ</mi> <mi>i</mi> </msub> <mo>=</mo> <mn>1</mn> <mo>/</mo> <mn>2</mn> </mrow> </semantics></math>) interfaces.</p> Full article ">Figure 4
<p>Schematic descriptions of zigzag-shaped sutural interfaces in biocomposites and their geometrical parameters. (<b>a</b>) A biocomposite segment with an underlying sutural interface. (<b>b</b>) An isolated interfacial region (one period) from the biocomposite. (<b>c</b>) Schematic examples of sutural interfaces with the same matrix length (<math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mi>m</mi> </msub> </mrow> </semantics></math>), but different zigzag angles (<math display="inline"><semantics> <mrow> <mi>θ</mi> <mo>=</mo> <mrow> <mn>10</mn> </mrow> <mo>°</mo> <mo>,</mo> <mo> </mo> <mrow> <mn>45</mn> </mrow> <mo>°</mo> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mo>~</mo> <mrow> <mn>70</mn> </mrow> <mo>°</mo> </mrow> </semantics></math>).</p> Full article ">Figure 5
<p>Simulation results for the interfacial dynamic modulus of biocomposites with zigzag-shaped sutural interfaces. (<b>a</b>) the modulus magnitude and (<b>b</b>) the loss coefficient of the interfacial region for different zigzag angles (<math display="inline"><semantics> <mi>θ</mi> </semantics></math>), achieved by back-calculations from far-field DMA testing on the biocomposite (<math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mi>i</mi> </msub> <mo>/</mo> <msub> <mi>L</mi> <mi>c</mi> </msub> <mo>=</mo> <mn>0.1</mn> </mrow> </semantics></math>), and by direct DMA testing on the interfacial region (<math display="inline"><semantics> <mrow> <msub> <mi>L</mi> <mi>i</mi> </msub> <mo>/</mo> <msub> <mi>L</mi> <mi>c</mi> </msub> <mo>=</mo> <mn>1</mn> </mrow> </semantics></math>).</p> Full article ">
13 pages, 1380 KiB  
Article
Photobiomodulation with Red and Near-Infrared Light Improves Viability and Modulates Expression of Mesenchymal and Apoptotic-Related Markers in Human Gingival Fibroblasts
by Ievgeniia Kocherova, Artur Bryja, Katarzyna Błochowiak, Mariusz Kaczmarek, Katarzyna Stefańska, Jacek Matys, Kinga Grzech-Leśniak, Marzena Dominiak, Paul Mozdziak, Bartosz Kempisty and Marta Dyszkiewicz-Konwińska
Materials 2021, 14(12), 3427; https://doi.org/10.3390/ma14123427 - 21 Jun 2021
Cited by 15 | Viewed by 3295
Abstract
Photobiomodulation (PBM), also called low-level laser treatment (LLLT), has been considered a promising tool in periodontal treatment due to its anti-inflammatory and wound healing properties. However, photobiomodulation’s effectiveness depends on a combination of parameters, such as energy density, the duration and frequency of [...] Read more.
Photobiomodulation (PBM), also called low-level laser treatment (LLLT), has been considered a promising tool in periodontal treatment due to its anti-inflammatory and wound healing properties. However, photobiomodulation’s effectiveness depends on a combination of parameters, such as energy density, the duration and frequency of the irradiation sessions, and wavelength, which has been shown to play a key role in laser-tissue interaction. The objective of the study was to compare the in vitro effects of two different wavelengths—635 nm and 808 nm—on the human primary gingival fibroblasts in terms of viability, oxidative stress, inflammation markers, and specific gene expression during the four treatment sessions at power and energy density widely used in dental practice (100 mW, 4 J/cm2). PBM with both 635 and 808 nm at 4 J/cm2 increased the cell number, modulated extracellular oxidative stress and inflammation markers and decreased the susceptibility of human primary gingival fibroblasts to apoptosis through the downregulation of apoptotic-related genes (P53, CASP9, BAX). Moreover, modulation of mesenchymal markers expression (CD90, CD105) can reflect the possible changes in the differentiation status of irradiated fibroblasts. The most pronounced results were observed following the third irradiation session. They should be considered for the possible optimization of existing low-level laser irradiation protocols used in periodontal therapies. Full article
(This article belongs to the Special Issue Laser Processing of Biocompatible Materials: From Fundamentals to Applications)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic representation of the experimental design. (<b>A</b>) Gingival tissue samples were enzymatically digested to isolate the gingival fibroblasts for further primary in vitro culture. The cells were propagated and passaged three times and immunophenotyped before the experiment. (<b>B</b>) The cells were divided into control (untreated) and two experimental groups, which were subjected to LLLT sessions with red (635 nm) or near-infrared (808 nm) light. Following 24 h after each LLLT session, the metabolic activity assay was performed. The cells were harvested for gene expression analysis. The conditioned medium was collected to assess the level of extracellular oxidative stress and inflammation markers, created with BioRender.</p> Full article ">Figure 2
<p>Phenotypical characterization of human primary gingival fibroblasts. Isolated cells were positive for <span class="html-italic">CD44</span>, <span class="html-italic">CD90</span>, and <span class="html-italic">CD105</span>.</p> Full article ">Figure 3
<p>(<b>A</b>) The growth curve is showing the level of metabolic activity normalized to cell number. (<b>B</b>) Mean cells number in the irradiated and non-treated groups assessed with TOX8 metabolic activity assay. Results expressed as mean ± SD. ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001.</p> Full article ">Figure 4
<p>The levels of extracellular oxidative stress and inflammation markers in cultured human gingival fibroblasts. Results expressed as mean ± SD. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001.</p> Full article ">Figure 5
<p>Expression of genes involved in apoptotic pathways in cultured human gingival fibroblasts. Results expressed as mean ± SD, n = 12. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01.</p> Full article ">Figure 6
<p>Gene expression of markers characteristic for mesenchymal stem cells in cultured human gingival fibroblasts. Results expressed as mean ± SD, n = 12. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001.</p> Full article ">
10 pages, 4578 KiB  
Article
Influence of Welding Speeds on the Morphology, Mechanical Properties, and Microstructure of 2205 DSS Welded Joint by K-TIG Welding
by Shuwan Cui, Shuwen Pang, Dangqing Pang and Zhiqing Zhang
Materials 2021, 14(12), 3426; https://doi.org/10.3390/ma14123426 - 21 Jun 2021
Cited by 16 | Viewed by 2542
Abstract
In this paper, 8.0 mm thickness 2205 duplex stainless steel (DSS) workpieces were welded with a keyhole tungsten inert gas (K-TIG) welding system under different welding speeds. After welding, the morphologies of the welds under different welding speed conditions were compared and analyzed. [...] Read more.
In this paper, 8.0 mm thickness 2205 duplex stainless steel (DSS) workpieces were welded with a keyhole tungsten inert gas (K-TIG) welding system under different welding speeds. After welding, the morphologies of the welds under different welding speed conditions were compared and analyzed. The microstructure, two-phase ratio of austenite/ferrite, and grain boundary characteristics of the welded joints were studied, and the microhardness and tensile properties of the welded joints were tested. The results show that the welding speed has a significant effect on the weld morphology, the two-phase ratio, grain boundary misorientation angle (GBMA), and mechanical properties of the welded joint. When the welding speed increased from 280 mm/min to 340 mm/min, the austenite content and the two-phase ratio in the weld metal zone (WMZ) decreased. However, the ferrite content in the WMZ increased. The proportion of the Σ3 coincident site lattice grain boundary (CSLGB) decreased as the welding speed increased, which has no significant effect on the tensile strength of welded joints. The microhardness of the WMZ and the tensile strength of the welded joint gradually increased when the welding speed was 280–340 mm/min. The 2205 DSS K-TIG welded joints have good plasticity. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic diagram of keyhole tungsten inert gas (K-TIG) welding.</p> Full article ">Figure 2
<p>Tensile test specimen dimension.</p> Full article ">Figure 3
<p>Cross section of 2205 DSS K-TIG welded joints at different weld speeds: (<b>a</b>) 280 mm/min, (<b>b</b>) 300 mm/min, (<b>c</b>) 320 mm/min, (<b>d</b>) 340 mm/min, and (<b>e</b>) 360 mm/min.</p> Full article ">Figure 4
<p>Weld width at different welding speeds.</p> Full article ">Figure 5
<p>Microstructure of 2205 DSS K-TIG welded joint. (<b>a</b>) BM. WMZ under different welding speeds (mm/min): (<b>b</b>) 280, (<b>c</b>) 300, (<b>d</b>) 320, and (<b>e</b>) 340.</p> Full article ">Figure 6
<p>Phase content and austenite/ferrite ratio in the BM and WMZ under different welding speeds.</p> Full article ">Figure 7
<p>GBMA distribution maps of the welded joint. (<b>a</b>) BM. WMZ under different welding speeds (mm/min): (<b>b</b>) 280, (<b>c</b>) 300, (<b>d</b>) 320, and (<b>e</b>) 340.</p> Full article ">Figure 7 Cont.
<p>GBMA distribution maps of the welded joint. (<b>a</b>) BM. WMZ under different welding speeds (mm/min): (<b>b</b>) 280, (<b>c</b>) 300, (<b>d</b>) 320, and (<b>e</b>) 340.</p> Full article ">Figure 8
<p>Microhardness distribution trend map of WMZ under different welding speeds.</p> Full article ">Figure 9
<p>SEM image of tensile fracture. (<b>a</b>) BM. Welded joints under different welding speeds (mm/min): (<b>b</b>) 280, (<b>c</b>) 300, (<b>d</b>) 320, and (<b>e</b>) 340.</p> Full article ">
10 pages, 36578 KiB  
Article
Evaluation of the Composite Mechanism of Nano-Fe2O3/Asphalt Based on Molecular Simulation and Experiments
by Yuhao He, Qing Zeng, Yaru Liu, Peng Liu, Yuqin Zeng, Zhenghong Xu and Qicheng Liu
Materials 2021, 14(12), 3425; https://doi.org/10.3390/ma14123425 - 21 Jun 2021
Viewed by 2054
Abstract
Asphalt, as an indispensable binder in road paving, plays an important role in transportation development. However, the mechanism of action between the modifier and asphalt cannot be fully explained by the existing test methods. This paper combines molecular simulations with experiments to provide [...] Read more.
Asphalt, as an indispensable binder in road paving, plays an important role in transportation development. However, the mechanism of action between the modifier and asphalt cannot be fully explained by the existing test methods. This paper combines molecular simulations with experiments to provide a research and analysis tool to evaluate the “structure−performance” relationship of asphalt. From the trend of experimental results, the optimal content of Nano-Fe2O3 is 1% to 3%. The AFM micrograph of the asphalt material shows that at 3%, the Nano-Fe2O3 can be effectively dispersed in the asphalt and the unique “ bee structures “ of the asphalt can be adsorbed around the modifier. Molecular dynamics studies and results show that when Nano-Fe2O3 are incorporated into the asphalt and have a strong adsorption force on the colloidal structure of asphalt, the “ bee structures “ can be adsorbed around the Nano-Fe2O3. In the range of 208–543 K, the sol-gel structure of asphalt in the Nano-Fe2O3/asphalt composite system is gradually disrupted. Full article
(This article belongs to the Section Construction and Building Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>SEM image of Nano-Fe<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 2
<p>Structural model of asphalt SARA and Nano-Fe<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 3
<p>Effect of different Nano-Fe<sub>2</sub>O<sub>3</sub> on asphalt viscosity at different temperatures.</p> Full article ">Figure 4
<p>FTIR maps of modified asphalt with different Nano-Fe<sub>2</sub>O<sub>3</sub> doping.</p> Full article ">Figure 5
<p>Microscopic characterization of AFM at different doping levels.</p> Full article ">Figure 6
<p>RDF between Nano-Fe<sub>2</sub>O<sub>3</sub> and asphalt components in Nano-Fe<sub>2</sub>O<sub>3</sub>/asphalt composite system. Figures (<b>a</b>–<b>f</b>) are RDF curves at different temperatures.</p> Full article ">
12 pages, 2488 KiB  
Article
Capture of Fullerenes in Cages and Rings by Forming Metal-π Bond Arene Interactions
by Citlalli Rios, Bertha Molina and Roberto Salcedo
Materials 2021, 14(12), 3424; https://doi.org/10.3390/ma14123424 - 21 Jun 2021
Cited by 1 | Viewed by 1866
Abstract
Nowadays, the task of the selectively capture of fullerene molecules from soot is the subject of several studies. The low solubility of fullerenes represents a drawback when the goal is to purify them and to carry out chemical procedures where they participate. There [...] Read more.
Nowadays, the task of the selectively capture of fullerene molecules from soot is the subject of several studies. The low solubility of fullerenes represents a drawback when the goal is to purify them and to carry out chemical procedures where they participate. There are different molecules that can act as a kind of cocoon, giving shelter to the fullerene cages in such a way that they can be included in a solution or can be extracted from a mix. In this work, a theoretical study of some known and new proposed organic molecules of this kind is presented. In all cases, the interaction occurs with the help of a metallic atom or ion which plays the role of a bridge, providing a place for a metallocene like interaction to occur. The thermodynamic arguments favoring the formation of this adduct species are addressed as well as the nature of the bond by means QTAIM parameters and frontier molecular orbitals analysis. Full article
(This article belongs to the Special Issue Theoretical Chemistry of Fullerenes and Related Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>The molecular traps under study. (<b>a</b>) A molecule prepared by Beuerle and his coworkers [<a href="#B33-materials-14-03424" class="html-bibr">33</a>]. (<b>b</b>) A domestic designed structure with coronene fragments in the edges. (<b>c</b>) A molecule inspired by a macrocycle synthesized by Bain and coworkers [<a href="#B34-materials-14-03424" class="html-bibr">34</a>].</p> Full article ">Figure 2
<p>Frontier molecular orbitals of molecule <b>a</b>.</p> Full article ">Figure 3
<p>π-stacking interaction between fullerene and molecule <b>a</b>.</p> Full article ">Figure 4
<p>Fullerene molecule trapped into the hollow of molecule <b>c</b>.</p> Full article ">Figure 5
<p>Fullerene and molecule <b>a</b> complex with metallocene bond.</p> Full article ">Figure 6
<p>Frontier molecular orbitals of the complex between C<sub>60</sub>M fragment and molecule <b>a</b>.</p> Full article ">Figure 7
<p>Frontier molecular orbitals of the complex between molecule <b>c</b> and C<sub>60</sub>M fragment.</p> Full article ">Figure 8
<p>Frontier molecular orbitals of the complex between molecule <b>b</b> and C<sub>60</sub>Ni fragment.</p> Full article ">Figure 9
<p>Frontier molecular orbitals of the complex between molecule <b>b</b> and C<sub>60</sub>Cr fragment.</p> Full article ">
17 pages, 1586 KiB  
Article
Concrete Modular Pavement Structures with Optimized Thickness Based on Characteristics of High Performance Concrete Mixtures with Fibers and Silica Fume
by Audrius Vaitkus, Judita Gražulytė, Ovidijus Šernas, Martynas Karbočius and Rafal Mickevič
Materials 2021, 14(12), 3423; https://doi.org/10.3390/ma14123423 - 21 Jun 2021
Cited by 3 | Viewed by 2459
Abstract
Usually, C30/37 strength class concrete is used to construct concrete pavements on a rigid, semi-rigid or flexible base. Concrete with such a strength delivers essential design characteristics: flexural strength and tensile splitting strength are between 4.5–5.4 MPa and 2.8–3.7 MPa, respectively. Design characteristics [...] Read more.
Usually, C30/37 strength class concrete is used to construct concrete pavements on a rigid, semi-rigid or flexible base. Concrete with such a strength delivers essential design characteristics: flexural strength and tensile splitting strength are between 4.5–5.4 MPa and 2.8–3.7 MPa, respectively. Design characteristics can be significantly increased by densifying the concrete mixture, i.e., adding silica fume, steel or polypropylene macro fibers. As high-performance concrete characteristics are 20–60% higher than those for standard concrete (C30/37), new possibilities to reduce the thickness of concrete pavement slabs appear. The theoretical analysis of concrete pavement structures with high-performance concrete mixtures (C40/50, C45/55 and C50/60) showed that slab thickness could be reduced by 6–39% compared to a standard concrete pavement structure depending on the concrete properties and design method. From all those pavement structures, three concrete mixtures were determined as the most rational ones in terms of PCP thickness reduction and total pavement cost: (i) with 49.5 kg/m3 of steel fibers and 25.2 kg/m3 of silica fume; (ii) with 10.0 kg/m3 of polypropylene fibers (type A); (iii) with 49.5 kg/m3 of steel fibers. Full article
(This article belongs to the Special Issue Study on Advanced Cement-Based Materials and Their Applications)
►▼ Show Figures

Figure 1

Figure 1
<p>The minimum PCP thickness calculated by the RDO Beton 09 method.</p> Full article ">Figure 2
<p>The minimum PCP thickness calculated with the design software StreetPave.</p> Full article ">Figure 3
<p>Calculated PCP thicknesses on hydraulically bound base.</p> Full article ">Figure 4
<p>Calculated PCP thicknesses on crushed aggregates base.</p> Full article ">Figure 5
<p>The relationship between the calculated PCP thickness according to the RDO Beton 09 method and the concrete tensile splitting strength.</p> Full article ">Figure 6
<p>The relationship between the calculated PCP thickness using the software StreetPave and the concrete flexural strength.</p> Full article ">Figure 7
<p>Cost of fresh concrete in terms of compressive strength.</p> Full article ">Figure 8
<p>Cost of fresh concrete in terms of flexural strength.</p> Full article ">Figure 9
<p>Cost per square meter of pavement on the crushed aggregate base and hydraulically bound base.</p> Full article ">
20 pages, 23764 KiB  
Review
A Review on Cement Asphalt Emulsion Mortar Composites, Structural Development, and Performance
by Hussaini Abdullahi Umar, Xiaohui Zeng, Xuli Lan, Huasheng Zhu, Yirui Li, Hong Zhao and Haichuan Liu
Materials 2021, 14(12), 3422; https://doi.org/10.3390/ma14123422 - 21 Jun 2021
Cited by 12 | Viewed by 3333
Abstract
The use of cement emulsified asphalt mortar (CA mortar) in the track structure of high-speed speed railways has been gaining considerations by many researchers due to its coupled merits of the strength of cement as well as the flexibility of asphalt material. The [...] Read more.
The use of cement emulsified asphalt mortar (CA mortar) in the track structure of high-speed speed railways has been gaining considerations by many researchers due to its coupled merits of the strength of cement as well as the flexibility of asphalt material. The asphalt to cement ratio (A/C) and the compatibility among constituent materials are crucial to the properties of CA mortar. To improve the performance properties and application of CA mortar, it is imperative to have a broad understanding of the composition mechanisms and compatibility between constituent materials. This paper summarizes interesting research outcomes related to the composition and properties of CA mortar. The consumption of water by cement promotes the breakdown of emulsified asphalt, likewise, the adsorption of asphalt droplets on the surface of cement grains retards the hydration process of cement. An appropriate A/C is required for the cement hydration rate to match the speed of demulsification of asphalt emulsion. Depending on the type and properties for which the CA mortar is designed to possess, the A/C ranges from 0.2 to 0.6 for type 1 (CAM I), and 0.6 to 1.2 for type 2 (CAM II). This paper also discusses measures taken to improve performance properties, compatibility, the interaction between constituent materials of CA mortar, and the use of additives as a partial replacement of cement in CA mortar production. The current review also suggests areas of interest for future research studies. This paper is useful to those who aim to understand or study the composition mechanisms and performance properties of CA mortar. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Structure of a slab ballastless track; (<b>a</b>) China Railway Track System (CRTS) I [<a href="#B7-materials-14-03422" class="html-bibr">7</a>], (<b>b</b>) CRTS II [<a href="#B15-materials-14-03422" class="html-bibr">15</a>]. CA: cement emulsified asphalt.</p> Full article ">Figure 2
<p>Schematic representation of layer arrangement and load transfer in the ballastless slab track system [<a href="#B12-materials-14-03422" class="html-bibr">12</a>].</p> Full article ">Figure 3
<p>Flow chart for CA mortar preparation; (<b>a</b>) dry mixing method (<b>b</b>) wet mixing method.</p> Full article ">Figure 4
<p>Dispersion state [<a href="#B3-materials-14-03422" class="html-bibr">3</a>].</p> Full article ">Figure 5
<p>Schematic representation of asphalt net formation on cement grain [<a href="#B31-materials-14-03422" class="html-bibr">31</a>].</p> Full article ">Figure 6
<p>Stages in the breakdown or demulsification of asphalt emulsion [<a href="#B37-materials-14-03422" class="html-bibr">37</a>].</p> Full article ">Figure 7
<p>SEM images for the microstructure of CA paste hydrating at (<b>a</b>) 0 h after mixing (<b>b</b>) 3 h (<b>c</b>) 6 h (<b>d</b>) 12 h (<b>e</b>) 24 h (<b>f</b>) 28 days curing age [<a href="#B42-materials-14-03422" class="html-bibr">42</a>].</p> Full article ">Figure 8
<p>Isothermal calorimetry curves for cement with anionic emulsion and anionic emulsifier [<a href="#B55-materials-14-03422" class="html-bibr">55</a>].</p> Full article ">Figure 9
<p>Isothermal calorimetry curves for cement with cationic emulsifiers [<a href="#B55-materials-14-03422" class="html-bibr">55</a>].</p> Full article ">
16 pages, 5759 KiB  
Article
Negative Poisson’s Ratio-Spacer Design and Its Thermo-Mechanical Coupling Analysis Considering Specific Force Output
by Qianqian Yuan, Yongsheng Zhu, Ke Yan, Yiqing Cai and Jun Hong
Materials 2021, 14(12), 3421; https://doi.org/10.3390/ma14123421 - 21 Jun 2021
Viewed by 2287
Abstract
Aiming at the problems of a complex structure or poor controllability of the existing bearing preload control devices, a method of self-regulation via a negative Poisson’s ratio (NPR) spacer is proposed. Firstly, the principle of preload automatic adjustment at the bearing operation was [...] Read more.
Aiming at the problems of a complex structure or poor controllability of the existing bearing preload control devices, a method of self-regulation via a negative Poisson’s ratio (NPR) spacer is proposed. Firstly, the principle of preload automatic adjustment at the bearing operation was introduced and the NPRs with three types of cell structures were analyzed. Furthermore, a thermo-mechanical coupling analysis model of the NPR spacer was established and the deformation and force output characteristics of the NPR spacer were studied and experimentally verified. It is found that the concave hexagonal cell structure has the optimal deformation characteristics for bearing preload adjustment. When the temperature is considered, the absolute value of Poisson’s ratio of the NPR spacer decreases as the speed increases and the elongation of the NPR spacer and the output forces are much larger than those without temperature consideration. With the increase in temperature or rotating speed, the axial elongation and output forces of the NPR spacer increases while the effect of temperature is relatively larger. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic of spindle structure.</p> Full article ">Figure 2
<p>Principle of preload adjustment of NPR spacer. (<b>a</b>) Initial assembly stage of spacer, (<b>b</b>) Operation stage of spacer, (<b>c</b>) Cell contraction under compression, (<b>d</b>) Spacer expansion by centrifugal force, (<b>e</b>) Cell expansion under centrifugal force.</p> Full article ">Figure 3
<p>Periodic arrangement of cell structure.</p> Full article ">Figure 4
<p>Finite element method model.</p> Full article ">Figure 5
<p>Contour maps of horizontal (<span class="html-italic">u</span><sub>x</sub>) and vertical (<span class="html-italic">u</span><sub>y</sub>) components of displacement field in different cells: (<b>a</b>) X-direction displacement of internally concave hexagonal, (<b>b</b>) Y-direction displacement of internally concave hexagonal, (<b>c</b>) X-direction displacement of H-shaped, (<b>d</b>) Y-direction displacement of H-shaped, (<b>e</b>) X-direction displacement of star-shaped, and (<b>f</b>) Y-direction displacement of star-shaped NPR periodic cell structures.</p> Full article ">Figure 6
<p>Three-dimensional NPR spacer structure.</p> Full article ">Figure 7
<p>Flowchart of output force calculation.</p> Full article ">Figure 8
<p>Thermo-mechanical coupling analysis flowchart.</p> Full article ">Figure 9
<p>Spindle-bearing system temperature field at 8000 r/min.</p> Full article ">Figure 10
<p>Temperature fields of NPR spacer at different speeds. (<b>a</b>) Temperature field of NPR spacer with speed of 2000 r/min, (<b>b</b>) Temperature field of NPR spacer with speed of 4000 r/min, (<b>c</b>) Temperature field of NPR spacer with speed of 6000 r/min, (<b>d</b>) Temperature field of NPR spacer with speed of 8000 r/min.</p> Full article ">Figure 11
<p>Poisson’s ratio variation of NPR spacer with speed.</p> Full article ">Figure 12
<p>Elongations of NPR spacer at different speeds.</p> Full article ">Figure 13
<p>Output forces of NPR spacer at different speeds.</p> Full article ">Figure 14
<p>NPR spacer thermo-mechanical coupling test rig.</p> Full article ">Figure 15
<p>Effect of speed and temperature on the elongation of the NPR spacer.</p> Full article ">Figure 16
<p>Effect of speed and temperature on the output force of the NPR spacer.</p> Full article ">
10 pages, 1538 KiB  
Article
Research into the Strength of an Open Wagon with Double Sidewalls Filled with Aluminium Foam
by Oleksij Fomin, Mykola Gorbunov, Juraj Gerlici, Glib Vatulia, Alyona Lovska and Kateryna Kravchenko
Materials 2021, 14(12), 3420; https://doi.org/10.3390/ma14123420 - 20 Jun 2021
Cited by 34 | Viewed by 2411
Abstract
The research is concerned with the use of double walls filled with aluminium foam for an open wagon in order to decrease the dynamic stresses during the operational modes. The research presents the strength calculation for the bearing structure of an open wagon [...] Read more.
The research is concerned with the use of double walls filled with aluminium foam for an open wagon in order to decrease the dynamic stresses during the operational modes. The research presents the strength calculation for the bearing structure of an open wagon with consideration of the engineering solutions proposed. It was found that the maximum equivalent stresses appeared in the bottom section of the centre sill behind the back support; they amounted to about 315 MPa and did not exceed the allowable values. The maximum displacements were detected in the middle section of the centre sill and amounted to 9.6 mm. The maximum deformations were 1.17 × 10−2. The research also presents the strength calculation for a weld joint in the maximum loaded zones of the bearing structure of an open wagon and gives the results of a modal analysis of the bearing structure of the improved open wagon. It was found that the critical oscillation frequencies did not exceed the allowable values. The results of the research may be useful for those who are concerned about designing innovative rolling stock units and improving the operational efficiency of railway transport. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Bearing structure of an open wagon of circular pipes filled with aluminium foam.</p> Full article ">Figure 2
<p>Components of the bearing structure of an open wagon of double walls (<b>a</b>) side wall; (<b>b</b>) end wall.</p> Full article ">Figure 3
<p>Design diagram of an open wagon: <math display="inline"><semantics> <mrow> <msub> <mi>P</mi> <mi>l</mi> </msub> </mrow> </semantics></math>—the longitudinal force, <math display="inline"><semantics> <mrow> <msubsup> <mi>P</mi> <mi>v</mi> <mrow> <mi>s</mi> <mi>t</mi> </mrow> </msubsup> </mrow> </semantics></math>—the vertical static load, <math display="inline"><semantics> <mrow> <msub> <mi>P</mi> <mi>b</mi> </msub> </mrow> </semantics></math>—the bulk freight.</p> Full article ">Figure 4
<p>Stresses on components of the bearing structure of a circular-piped wagon.</p> Full article ">Figure 5
<p>Contact assembly between the intermediate vertical post and the cross bearer of an open wagon frame.</p> Full article ">Figure 6
<p>Forms of the oscillations of the bearing structure of an open wagon (scale 20:1) (<b>a</b>) 1st natural frequency; (<b>b</b>) 2nd natural frequency; (<b>c</b>) 3rd natural frequency; (<b>d</b>) 4th natural frequency.</p> Full article ">
16 pages, 5055 KiB  
Article
Surface Properties and Morphology of Boron Carbide Nanopowders Obtained by Lyophilization of Saccharide Precursors
by Dawid Kozień, Piotr Jeleń, Joanna Stępień, Zbigniew Olejniczak, Maciej Sitarz and Zbigniew Pędzich
Materials 2021, 14(12), 3419; https://doi.org/10.3390/ma14123419 - 20 Jun 2021
Cited by 5 | Viewed by 2112
Abstract
The powders of boron carbide are usually synthesized by the carbothermal reduction of boron oxide. As an alternative to high-temperature reactions, the development of the carbothermal reduction of organic precursors to produce B4C is receiving considerable interest. The aim of this [...] Read more.
The powders of boron carbide are usually synthesized by the carbothermal reduction of boron oxide. As an alternative to high-temperature reactions, the development of the carbothermal reduction of organic precursors to produce B4C is receiving considerable interest. The aim of this work was to compare two methods of preparing different saccharide precursors mixed with boric acid with a molar ratio of boron to carbon of 1:9 for the synthesis of B4C. In the first method, aqueous solutions of saccharides and boric acid were dried overnight at 90 °C and pyrolyzed at 850 °C for 1 h under argon flow. In the second method, aqueous solutions of different saccharides and boric acid were freeze-dried and prepared in the same way as in the first method. Precursors from both methods were heat-treated at temperatures of 1300 to 1700 °C. The amount of boron carbide in the powders depends on the saccharides, the temperature of synthesis, and the method of precursor preparation. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>MIR spectra of the raw material dried at 90 °C and freeze-dried boric acid (H<sub>3</sub>BO<sub>3</sub>).</p> Full article ">Figure 2
<p>MIR spectra of the different saccharide precursors mixed with boric acid with a molar ratio of boron to carbon of 1:9: (<b>a</b>) dried at 90 °C and (<b>b</b>) freeze-dried.</p> Full article ">Figure 2 Cont.
<p>MIR spectra of the different saccharide precursors mixed with boric acid with a molar ratio of boron to carbon of 1:9: (<b>a</b>) dried at 90 °C and (<b>b</b>) freeze-dried.</p> Full article ">Figure 3
<p>Deconvolution of the Raman spectra of (<b>a</b>) HES and (<b>b</b>) precursor prepared from a mixture of lyophilized HES and boric acid both pyrolyzed at 850 °C.</p> Full article ">Figure 4
<p>An example of a deconvoluted <sup>11</sup>B MAS NMR spectrum of fructose mixed with boric acid in a molar ratio of 9 C:1 B and then recrystallized.</p> Full article ">Figure 5
<p>Boron edge spectra obtained from the PEEM/XAS research line for recrystallized and freeze-dried precursor after pyrolyzing at 850 °C.</p> Full article ">Figure 6
<p>Boron K edge XAS spectra for powders of boron carbide obtained from recrystallized and freeze-dried precursor after pyrolyzing at 850 °C and heat treatment at 1700 °C (spectra in color) and reference spectra of commercial B<sub>4</sub>C (black) and amorphous boron (gray). Vertical lines indicate the characteristic spectral features for the B<sub>4</sub>C reference sample.</p> Full article ">Figure 7
<p>The X-ray patterns of the powders prepared from the mixtures of dextrin: (<b>a</b>) recrystallized and (<b>b</b>) lyophilized.</p> Full article ">Figure 8
<p>Temperature dependences of boron carbide content in the prepared powders from recrystallization and freeze-drying: (<b>a</b>) glucose, (<b>b</b>) fructose, (<b>c</b>) dextrin, and (<b>d</b>) HES.</p> Full article ">Figure 8 Cont.
<p>Temperature dependences of boron carbide content in the prepared powders from recrystallization and freeze-drying: (<b>a</b>) glucose, (<b>b</b>) fructose, (<b>c</b>) dextrin, and (<b>d</b>) HES.</p> Full article ">Figure 9
<p>The changes in the crystallize size of boron carbide obtained with different precursors mixed with boric acid with a molar ratio of 9 C:1 B using both methods and heat treatment from 1300 to 1700 °C: (<b>a</b>) glucose, (<b>b</b>) fructose, (<b>c</b>) dextrin, and (<b>d</b>) HES.</p> Full article ">Figure 9 Cont.
<p>The changes in the crystallize size of boron carbide obtained with different precursors mixed with boric acid with a molar ratio of 9 C:1 B using both methods and heat treatment from 1300 to 1700 °C: (<b>a</b>) glucose, (<b>b</b>) fructose, (<b>c</b>) dextrin, and (<b>d</b>) HES.</p> Full article ">Figure 10
<p>SEM images of the boron carbide obtained from powders prepared at the same temperature using saccharides: (<b>a</b>) glucose, (<b>b</b>) freeze-drying glucose, (<b>c</b>) fructose, (<b>d</b>) freeze-drying fructose, (<b>e</b>) dextrin, (<b>f</b>) freeze-drying dextrin, (<b>g</b>) HES, and (<b>h</b>) freeze-drying HES [<a href="#B16-materials-14-03419" class="html-bibr">16</a>].</p> Full article ">Figure 10 Cont.
<p>SEM images of the boron carbide obtained from powders prepared at the same temperature using saccharides: (<b>a</b>) glucose, (<b>b</b>) freeze-drying glucose, (<b>c</b>) fructose, (<b>d</b>) freeze-drying fructose, (<b>e</b>) dextrin, (<b>f</b>) freeze-drying dextrin, (<b>g</b>) HES, and (<b>h</b>) freeze-drying HES [<a href="#B16-materials-14-03419" class="html-bibr">16</a>].</p> Full article ">
8 pages, 1207 KiB  
Article
Behavior of Ternary Mixtures of Hydrogen Bond Acceptors and Donors in Terms of Band Gap Energies
by Alberto Mannu, Francesca Cardano, Salvatore Baldino and Andrea Fin
Materials 2021, 14(12), 3418; https://doi.org/10.3390/ma14123418 - 20 Jun 2021
Cited by 2 | Viewed by 2328
Abstract
Three ternary mixtures composed by choline chloride (ChCl), ethylene glycol (EG), and a second hydrogen bond donor (HBD) as ethanol (A), 2-propanol (B), and glycerol (C) were studied in terms of composition related to the band gap energy (BGE). A Design of Experiments [...] Read more.
Three ternary mixtures composed by choline chloride (ChCl), ethylene glycol (EG), and a second hydrogen bond donor (HBD) as ethanol (A), 2-propanol (B), and glycerol (C) were studied in terms of composition related to the band gap energy (BGE). A Design of Experiments (DoE) approach, and in particular a Simple Lattice three-components design, was employed for determining the variation of the BGE upon the composition of each system. UV-VIS analysis and subsequent Tauc plot methodology provided the data requested from the DoE, and multivariate statistical analysis revealed a drop of the BGE in correspondence to specific binary compositions for systems A and B. In particular, a BGE of 3.85 eV was registered for the mixtures ChCl/EtOH (1:1) and ChCl/2-propanol (1:1), which represents one of the lowest values ever observed for these systems. Full article
(This article belongs to the Special Issue Advances and Applications in Deep Eutectic Solvents Technology)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>UV-VIS spectra of systems A5 (<b>a</b>), C5 (<b>b</b>), A7 (<b>c</b>), and C7 (<b>d</b>).</p> Full article ">Figure 2
<p>Tauc plots relative to the systems A4, B4, C4, ChCl/EG (1:1) and A5, ChCl/EtOH (1:1).</p> Full article ">Figure 3
<p>Estimated response surface for systems (<b>A</b>–<b>C</b>).</p> Full article ">
18 pages, 8924 KiB  
Article
Effect of Fe and Cr on the Macro/Micro Tribological Behaviours of Copper-Based Composites
by Zhongyi Zhang, Haibin Zhou, Pingping Yao, Kunyang Fan, Yongqiang Liu, Lin Zhao, Yelong Xiao, Taimin Gong and Minwen Deng
Materials 2021, 14(12), 3417; https://doi.org/10.3390/ma14123417 - 20 Jun 2021
Cited by 7 | Viewed by 1973
Abstract
Fe and Cr are regarded as two of the most important friction components in Cu-based composites (Cu–BCs). In this study, the microstructural detection and micro- and macro-tribology evaluation of Cu–BCs containing Fe and Cr were performed. The results indicated that both Fe and [...] Read more.
Fe and Cr are regarded as two of the most important friction components in Cu-based composites (Cu–BCs). In this study, the microstructural detection and micro- and macro-tribology evaluation of Cu–BCs containing Fe and Cr were performed. The results indicated that both Fe and Cr formed diffusion interfaces with the copper matrix. Because of the generation of a defect interface layer, the Cr/Cu interface exhibited a low bonding strength. Owing to the excellent binding interface between Fe and Cu, the high coefficient of friction (COF) of Fe, and the formation of a mechanical mixing layer promoted by Fe, the Cu–BCs containing Fe presented better friction performance under all braking energy per unit area (BEPUA) values. The main wear mechanism of Cu–BCs containing Fe and Cr changed from abrasion to delamination with an increase in BEPUA, and the delamination of Cu–BCs containing Fe was induced by breaks in the mechanical mixed layer (MML). Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Preparation process for Cu–BCs.</p> Full article ">Figure 2
<p>Structure chart of the MM-3000 friction tester.</p> Full article ">Figure 3
<p>Typical morphology of the Fe and Cr particles: (<b>a</b>) Fe particle and (<b>b</b>) Cr particle.</p> Full article ">Figure 4
<p>Microstructure of the Cu–Fe sample (<b>a</b>) and the characteristics of the Fe/Cu interface (<b>b</b>).</p> Full article ">Figure 5
<p>Microstructure of the Cu–Cr sample and interface characteristics. (<b>a</b>) Microstructure of the Cu–Cr sample (A2); (<b>b</b>) enlarged image of the Cr friction component; (<b>c</b>) characteristics of the Cr/Cu interface.</p> Full article ">Figure 6
<p>Microstructure of Cu–BCs: (<b>a</b>) Cu-Fe-Gr and (<b>b</b>) Cu-Cr-Gr.</p> Full article ">Figure 7
<p>Brinell hardness of Cu–BCs.</p> Full article ">Figure 8
<p>Scratch grooves of the Fe/Cu interface and Cr/Cu interface with different forces: (<b>a</b>) 0.3 N Fe/Cu interface; (<b>b</b>) 0.5 N Fe/Cu interface; (<b>c</b>) 0.3 N Cr/Cu interface; and (<b>d</b>) 0.5 N Cr/Cu interface.</p> Full article ">Figure 9
<p>Curves of the coefficient of friction plotted versus the sliding distance in the Cu/Fe and Cr/Cu interface regions under different applied loads: (<b>a</b>) Fe/Cu interface regions and (<b>b</b>) Cu/Cr interface regions.</p> Full article ">Figure 10
<p>Curves for the <span class="html-italic">h<sub>rd</sub></span>, <span class="html-italic">h<sub>pd</sub></span> of friction plotted against the sliding distance in the Fe/Cu and Cr/Cu interface regions under different forces: (<b>a</b>) Cu/Fe interface regions and (<b>b</b>) Cu/Cr interface regions.</p> Full article ">Figure 11
<p>The schematic of indenter scratching on Cu–BCs.</p> Full article ">Figure 12
<p>The worn surfaces of Cu–BCs containing Fe and Cr tested under different BEPUAs: (<b>a</b>) Fe low-BEPUA; (<b>b</b>) Fe medium-BEPUA; (<b>c</b>) Fe high-BEPUA; (<b>d</b>) Cr low-BEPUA; (<b>e</b>) Cr medium-BEPUA; and (<b>f</b>) Cr high-BEPUA.</p> Full article ">Figure 13
<p>Subsurface and wear debris of Cu–BCs containing Fe and Cr tested under different BEPUA conditions: (<b>a</b>) Fe low-BEPUA; (<b>b</b>) Fe medium-BEPUA; (<b>c</b>) Fe high-BEPUA; (<b>d</b>) Cr low-BEPUA; (<b>e</b>) Cr medium-BEPUA; (<b>f</b>) Cr high-BEPUA.</p> Full article ">Figure 14
<p>Evolution of the wear mechanism for Cu–BCs containing Fe and Cr under high BEPUA.</p> Full article ">Figure 15
<p>The instantaneous coefficients of friction of Cu–BCs containing Fe (<b>a</b>) and Cr (<b>b</b>).</p> Full article ">Figure 16
<p>Variations in the coefficient of friction with the number of tests (<b>a</b>) and the mean coefficient of friction (<b>b</b>) of Cu–BCs containing Fe and Cr.</p> Full article ">Figure 17
<p>The wear rate of Cu–BCs and its counterpart: (<b>a</b>) wear rate of Cu–BCs and (<b>b</b>) wear rate of counterpart.</p> Full article ">
16 pages, 10036 KiB  
Article
Corrosion Fatigue Damages of Rebars under Loading in Time
by Yaroslav Blikharskyy, Jacek Selejdak and Nadiia Kopiika
Materials 2021, 14(12), 3416; https://doi.org/10.3390/ma14123416 - 20 Jun 2021
Cited by 26 | Viewed by 2572
Abstract
Nowadays, a relatively small number of studies concern the study of corrosion processes in reinforced concrete structures under load. Additionally, rather little research has been carried out concerning changes in the stress–strain state parameters of structures under the simultaneous action of aggressive environment [...] Read more.
Nowadays, a relatively small number of studies concern the study of corrosion processes in reinforced concrete structures under load. Additionally, rather little research has been carried out concerning changes in the stress–strain state parameters of structures under the simultaneous action of aggressive environment and load. This issue requires additional experimental and theoretical investigation. Determination of mechanical properties, fatigue characteristics and susceptibility to corrosion cracking was performed on samples of reinforcing St3GPF steel. The chemical composition of steel was determined by structural analysis. The spectral method for the determination of alloying elements and impurities in steels is based on the excitation of iron atoms and admixtures by electric discharge, decomposition of radiation into a spectrum, followed by its registration on photoplate with the use of electrograph. Experimental tests of samples in an aggressive environment under the action of statically applied tensile force showed that corrosion damage has little effect on the strength characteristics. At the same time, the decrease in area reduction and the decrease in strain were recorded. Additionally, the action of cyclic loads in an aggressive environment leads to a significant reduction in the fatigue limit to values from 20 to 24% of the yield strength of the original samples, which is 2–3 times lower than the fatigue limit of undamaged samples. Full article
(This article belongs to the Special Issue Manufacturing and Fatigue Properties of Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>The initial microstructure of reinforcing steel St3GPF.</p> Full article ">Figure 2
<p>Testing of samples by machine IM-4R: (<b>a</b>) general view; (<b>b</b>) the sample during the test.</p> Full article ">Figure 3
<p>Installation scheme for study of metals in corrosion fatigue conditions. 1: the cell for corrosion environment; 2: oil seal; 3: sample; 4: fluoroplastic plugs; 5: corrosive environment; Р: load.</p> Full article ">Figure 4
<p>Testing of samples with the use of machine ІМА-5: (<b>a</b>) general view; (<b>b</b>) the sample after testing.</p> Full article ">Figure 5
<p>Kinematic scheme of this installation. 1: sample; 2,3: connecting rods; 4: clamps with ball joints; 5: slab; 6: tension screws; 7: levers; 8: loads; 9: container for corrosive environment.</p> Full article ">Figure 6
<p>Testing of samples on the installation for cracking research of samples: (<b>а</b>) installation general view; (<b>b</b>) sample during testing.</p> Full article ">Figure 7
<p>The scheme of testing machine IM-4R on tension. 1: sample; 2: electric motor; 3: strain sensor; 4: load sensor; 5: diagram device; 6: screws.</p> Full article ">Figure 8
<p>Microscope Neophot-2.</p> Full article ">Figure 9
<p>Fatigue curves on the air (1, 2) and in 3% solution of NaCl (3) for steel St3GPF. 1: initial samples without corrosion damages; 2: samples with corrosion damages in the air; 3: samples with corrosion damages in the aggressive environment.</p> Full article ">Figure 10
<p>The character of damages for reinforcing steel after 15 days of exposure in corrosive environment. 1: undamaged metal; 2: corrosion ulcer.</p> Full article ">Figure 11
<p>The character of damages of reinforcing steel after 20 days of exposure in corrosive environment. 1: undamaged metal; 2: corrosion ulcer.</p> Full article ">Figure 12
<p>The character of damages of reinforcing steel after 25 days of exposure in corrosive environment. 1: undamaged metal; 2: corrosion ulcer; 3: standard smooth polished metal plate.</p> Full article ">Figure 13
<p>The character of damages of reinforcing steel after 30 days of exposure in corrosive environment. 1: undamaged metal; 2: corrosion ulcer, 3: standard smooth polished metal plate.</p> Full article ">Figure 14
<p>Metallography of samples with corrosion damage (15 days of exposure) after fatigue tests in air (±σ = 170 MPa). 1: undamaged metal; 2: corrosion ulcer; 4: corrosion crack.</p> Full article ">Figure 15
<p>Metallography of samples with corrosion damage (15 days of exposure) after fatigue tests in air (±σ = 200 MPa). 1: undamaged metal; 2: corrosion ulcer; 4: corrosion crack.</p> Full article ">Figure 16
<p>Metallography of samples with corrosion damage (15 days of exposure) after fatigue tests in air (±σ = 250 MPa). 1: undamaged metal; 2: corrosion ulcer; 4: corrosion crack.</p> Full article ">Figure 17
<p>Destruction character for testing rebar samples. (<b>a</b>,<b>b</b>) Tested samples for corrosion fatigue in aggressive environments; (<b>c</b>) tested samples for static load in the air; (<b>d</b>) tested samples for corrosion cracking with a welded rebar.</p> Full article ">
19 pages, 8772 KiB  
Article
Experimental Investigation of the Performance of a Hybrid Self-Healing System in Porous Asphalt under Fatigue Loadings
by Shi Xu, Xueyan Liu, Amir Tabaković and Erik Schlangen
Materials 2021, 14(12), 3415; https://doi.org/10.3390/ma14123415 - 20 Jun 2021
Cited by 21 | Viewed by 2343
Abstract
Self-healing asphalt, which is designed to achieve autonomic damage repair in asphalt pavement, offers a great life-extension prospect and therefore not only reduces pavement maintenance costs but also saves energy and reduces CO2 emissions. The combined asphalt self-healing system, incorporating both encapsulated [...] Read more.
Self-healing asphalt, which is designed to achieve autonomic damage repair in asphalt pavement, offers a great life-extension prospect and therefore not only reduces pavement maintenance costs but also saves energy and reduces CO2 emissions. The combined asphalt self-healing system, incorporating both encapsulated rejuvenator and induction heating, can heal cracks with melted binder and aged binder rejuvenation, and the synergistic effect of the two technologies shows significant advantages in healing efficiency over the single self-healing method. This study explores the fatigue life extension prospect of the combined healing system in porous asphalt. To this aim, porous asphalt (PA) test specimens with various healing systems were prepared, including: (i) the capsule healing system, (ii) the induction healing system, (iii) the combined healing system and (iv) a reference system (without extrinsic healing). The fatigue properties of the PA samples were characterized by an indirect tensile fatigue test and a four-point bending fatigue test. Additionally, a 24-h rest period was designed to activate the built-in self-healing system(s) in the PA. Finally, a damaging and healing programme was employed to evaluate the fatigue damage healing efficiency of these systems. The results indicate that all these self-healing systems can extend the fatigue life of porous asphalt, while in the combined healing system, the gradual healing effect of the released rejuvenator from the capsules may contribute to a better induction healing effect in the damaging and healing cycles. Full article
(This article belongs to the Special Issue Experimental Testing and Constitutive Modelling of Pavement Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>The basic principle of crack healing in asphalt pavement: (<b>a</b>) a crack generated in asphalt mastic; (<b>b</b>) the ‘mobile phase’ induced at the crack face; (<b>c</b>) closure of the crack by the ‘mobile phase’ and (<b>d</b>) immobilisation after healing (Hager et al., 2010).</p> Full article ">Figure 2
<p>Development of the calcium alginate capsules healing system.</p> Full article ">Figure 3
<p>The research methodology of this study.</p> Full article ">Figure 4
<p>Images of a single calcium alginate capsule. Reproduced with permission from refs. [<a href="#B24-materials-14-03415" class="html-bibr">24</a>,<a href="#B26-materials-14-03415" class="html-bibr">26</a>]. Copyright 2018 Elsevier Ltd.</p> Full article ">Figure 5
<p>Cylinder and beam samples’ detailed drilling/cutting schematic: (<b>a</b>) cylinder samples drilled from Slab_type_1 and (<b>b</b>) beam samples cut from Slab_type_2.</p> Full article ">Figure 6
<p>The ITF test: (<b>a</b>) the loading configuration schematic and (<b>b</b>) ITF test data example, where the red dashed line indicates the fatigue life.</p> Full article ">Figure 7
<p>4PB fatigue test: (<b>a</b>) beam samples, (<b>b</b>) 4PB testing schematic, (<b>c</b>) testing setup and (<b>d</b>) loading configuration.</p> Full article ">Figure 7 Cont.
<p>4PB fatigue test: (<b>a</b>) beam samples, (<b>b</b>) 4PB testing schematic, (<b>c</b>) testing setup and (<b>d</b>) loading configuration.</p> Full article ">Figure 8
<p>4PB test data example, where the slope of the red dashed line shows the damage rate.</p> Full article ">Figure 9
<p>24-h rest period for the healing of various healing systems.</p> Full article ">Figure 10
<p>The adjustable wooden box for the confining of beam specimen: (<b>a</b>), (<b>b</b>) and (<b>c</b>) show the schematic confining process for a beam specimen, while (<b>d</b>) shows the image of a beam specimen confined in the wooden box.</p> Full article ">Figure 11
<p>The damaging and healing programme for PA samples with various healing systems.</p> Full article ">Figure 12
<p>The opened capsules on fracture faces after fatigue loadings: (<b>a</b>) fracture faces of a cylinder specimen after ITF and (<b>b</b>) fracture face of a beam specimen after 4PB damaging and healing tests.</p> Full article ">Figure 13
<p>Indirect tensile fatigue results of cylinder specimens from all PA mixture groups.</p> Full article ">Figure 14
<p>Four-point bending fatigue test results for the induction healing system in PA mixture with different ageing levels: (<b>a</b>) total number of 4PB fatigue loading cycles and (<b>b</b>) the fatigue healing index.</p> Full article ">Figure 15
<p>Four-point bending fatigue test results for the aged mixture with various healing systems: (<b>a</b>) the capsule healing system, (<b>b</b>) the induction healing system, (<b>c</b>) the combined healing system and (<b>d</b>) the reference mix.</p> Full article ">Figure 16
<p>Number of 4PB fatigue loadings leading to failure of all beam specimens.</p> Full article ">Figure 17
<p>Development of flexural stiffness for the various healing systems.</p> Full article ">Figure 18
<p>The damage rate acquired from each 4PB damaging and healing cycle.</p> Full article ">Figure 19
<p>The fatigue healing index for various healing systems.</p> Full article ">
16 pages, 4864 KiB  
Article
The Influence of Titanium Dioxide on Silicate-Based Glasses: An Evaluation of the Mechanical and Radiation Shielding Properties
by Badriah Albarzan, Mohamed Y. Hanfi, Aljawhara H. Almuqrin, M. I. Sayyed, Haneen M. Alsafi and K. A. Mahmoud
Materials 2021, 14(12), 3414; https://doi.org/10.3390/ma14123414 - 20 Jun 2021
Cited by 26 | Viewed by 2567
Abstract
The mechanical and radiation shielding features were reported for a quaternary Na2O-CaO-SiO2-TiO2 glass system used in radiation protection. The fundamentals of the Makishima–Mazinize model were applied to evaluate the elastic moduli of the glass samples. The elastic moduli, [...] Read more.
The mechanical and radiation shielding features were reported for a quaternary Na2O-CaO-SiO2-TiO2 glass system used in radiation protection. The fundamentals of the Makishima–Mazinize model were applied to evaluate the elastic moduli of the glass samples. The elastic moduli, dissociation energy, and packing density increased as TiO2 increased. The glasses’ dissociation energy increased from 62.82 to 65.33 kJ/cm3, while the packing factor slightly increased between 12.97 and 13.00 as the TiO2 content increased. The MCNP-5 code was used to evaluate the gamma-ray shielding properties. The best linear attenuation coefficient was achieved for glass samples with a TiO2 content of 9 mol%: the coefficient decreased from 5.20 to 0.14 cm−1 as the photon energy increased from 0.015 to 15 MeV. Full article
(This article belongs to the Special Issue Radiation Shielding Materials)
►▼ Show Figures

Figure 1

Figure 1
<p>Variation of glass density and molar volume versus TiO<sub>2</sub> concentration.</p> Full article ">Figure 2
<p>The 3D geometry described by the MCNP-5 input file.</p> Full article ">Figure 3
<p>Variation of the dissociation energy (G<sub>t</sub>) and the packing density (<span class="html-italic">V<sub>t</sub></span>) versus TiO<sub>2</sub> concentration.</p> Full article ">Figure 4
<p>Variation of elastic moduli like the Young (<span class="html-italic">E</span>), bulk (<span class="html-italic">B</span>), shear (<span class="html-italic">K</span>), and longitudinal (<span class="html-italic">L</span>) properties as a function of TiO<sub>2</sub> concentration.</p> Full article ">Figure 5
<p>Dependence of the Poisson ratio and microhardness on TiO<sub>2</sub> concentration.</p> Full article ">Figure 6
<p>Change in LAC against incoming gamma-ray energy.</p> Full article ">Figure 7
<p>Ratios of MAC values computed by Phy-X against those simulated with the MCNP code.</p> Full article ">Figure 8
<p>HVL of glasses as a function of energy.</p> Full article ">Figure 9
<p>Changes in HVL in the glasses at stationary gamma photon energy (0.015, 0.15, 1.5, and 15 MeV).</p> Full article ">Figure 10
<p>Change in Z<sub>eff</sub> as a function of gamma-photon energy.</p> Full article ">Figure 11
<p>Change in Z<sub>eff</sub> at a fix four photon energies.</p> Full article ">Figure 12
<p>Change in equivalent atomic number (Z<sub>eq</sub>) against incoming photon energy.</p> Full article ">Figure 13
<p>Dependence of EBF and EABF on the radiation energy.</p> Full article ">Figure 14
<p>EBF changes against the penetration depth of the glasses at various gamma photon energies (0.015, 0.15, 1.5, and 15 MeV).</p> Full article ">Figure 15
<p>EABF changes against the penetration depth of the glasses at various gamma photon energies (0.015, 0.15, 1.5, and 15 MeV).</p> Full article ">
17 pages, 6212 KiB  
Article
The Combined Use of Gentamicin and Silver Nitrate in Bone Cement for a Synergistic and Extended Antibiotic Action against Gram-Positive and Gram-Negative Bacteria
by John Jackson, Joey Lo, Eric Hsu, Helen M. Burt, Ali Shademani and Dirk Lange
Materials 2021, 14(12), 3413; https://doi.org/10.3390/ma14123413 - 20 Jun 2021
Cited by 14 | Viewed by 2606
Abstract
Using bone cement as a carrier, gentamicin was for years the default drug to locally treat orthopedic infections but has lost favor due to increasing bacterial resistance to this drug. The objective of this study was to investigate the effect of combining gentamicin [...] Read more.
Using bone cement as a carrier, gentamicin was for years the default drug to locally treat orthopedic infections but has lost favor due to increasing bacterial resistance to this drug. The objective of this study was to investigate the effect of combining gentamicin with silver nitrate in bone cement against S. aureus and P. aeruginosa. Antibacterial effects (CFU counts) of gentamicin and silver were initially studied followed by studies using subtherapeutic concentrations of each in combination. The release rates from cement were measured over 10 days and day 7 release samples were saved and analyzed for antibiotic activity. A strong synergistic effect of combining silver with gentamicin was found using both dissolved drugs and using day 7 bone cement release media for both Gram-positive and Gram-negative bacteria. The cement studies were extended to vancomycin and tobramycin, which are also used in bone cement, and similar synergistic effects were found for day 7 release media with P. aeruginosa but not S. aureus. These studies conclude that the combined use of low loadings of gentamicin and silver nitrate in bone cement may offer an economical and much improved synergistic method of providing anti-infective orthopedic treatments in the clinic. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Bacterial concentration at t = 4 h for (<b>a</b>) AgNO<sub>3</sub> against <span class="html-italic">S. aureus</span>, (<b>b</b>) gentamicin against <span class="html-italic">S. aureus,</span> (<b>c</b>) AgNO<sub>3</sub> against <span class="html-italic">P. aeruginosa</span>, (<b>d</b>) gentamicin against <span class="html-italic">P. aeruginosa</span>.</p> Full article ">Figure 2
<p><span class="html-italic">P. aeruginosa</span> concentration at t = 4 h with 0.1 µg/mL gentamicin and varying Ag concentrations (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 3
<p><span class="html-italic">S. aureus</span> concentration at t = 4 h with 0.25 µg/mL gentamicin and varying Ag concentrations (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 4
<p>Time course of Ag release from Palacos bone cement films. Cement loaded with or without dextran T70 (18% <span class="html-italic">w/w</span>) and silver nitrate. (Silver loaded at 0.8% and gentamicin at 0.8% <span class="html-italic">w/w</span>). No DEX both refers to cement with gentamicin and Ag and no dextran (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 5
<p>Time course of gentamicin release from Palacos bone cement films. Cement loaded with or without dextran T70 18% <span class="html-italic">w/w</span>) and gentamicin. (Silver loaded at 0.8% and gentamicin at 0.8% <span class="html-italic">w/w</span>) No DEX both refers to cement with gentamicin and Ag and no dextran (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 6
<p>Time course of Ag release from Palacos bone cement films (no dextran) loaded with Ag alone or Ag plus gentamicin. (Silver loaded at 0.8% and gentamicin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 7
<p>Time course of gentamicin release from Palacos bone cement films (no dextran) loaded with gentamicin alone or gentamicin plus Ag. (Silver loaded at 0.8% and gentamicin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 8
<p>Bacterial concentrations of <span class="html-italic">S. aureus</span> incubated in day 7 release media from (<b>a</b>) Ag-releasing bone cement, (<b>b</b>) gentamicin-releasing bone cement, (<b>c</b>) Ag + gentamicin-releasing bone cement (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 9
<p>Bacterial concentrations of <span class="html-italic">P. aeruginosa</span> incubated with day 7 release media from (<b>a</b>) Ag-releasing bone cement, (<b>b</b>) gentamicin-releasing bone cement, (<b>c</b>) Ag + gentamicin-releasing bone cement (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 10
<p>Time course of release of vancomycin from bone cement films containing vancomycin alone or vancomycin with Ag. (Silver loaded at 0.8% and vancomycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 11
<p>Time course of release of tobramycin from bone cement films containing tobramycin alone or tobramycin plus Ag. (Silver loaded at 0.8% and tobramycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 4).</p> Full article ">Figure 12
<p>Bacterial concentrations of <span class="html-italic">P. aeruginosa</span> incubated in various dilutions of the 7-day incubation release media of bone cement containing (<b>a</b>) Ag, (<b>b</b>) Ag + tobramycin, (<b>c</b>) tobramycin. (Silver loaded at 0.8% and tobramycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 13
<p>Bacterial concentrations of <span class="html-italic">P. aeruginosa</span> incubated in various dilutions of the 7-day incubation release media of bone cement containing (<b>a</b>) Ag, (<b>b</b>) Ag + vancomycin, (<b>c</b>) vancomycin. (Silver loaded at 0.8% and vancomycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 14
<p>Bacterial concentrations of <span class="html-italic">S. aureus</span> incubated in various dilutions of the 7-day incubation release media of bone cement containing (<b>a</b>) Ag, (<b>b</b>) Ag + tobramycin, (<b>c</b>) tobramycin. (Silver loaded at 0.8% and tobramycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 15
<p>Bacterial concentrations of <span class="html-italic">S. aureus</span> incubated in various dilutions of 7-day incubation release media from bone cement loaded with (<b>a</b>) Ag, (<b>b</b>) Ag + vancomycin, (<b>c</b>) vancomycin. (Silver loaded at 0.8% and vancomycin at 0.8% <span class="html-italic">w/w</span>) (<span class="html-italic">n</span> = 3).</p> Full article ">
20 pages, 309 KiB  
Editorial
Testing of Materials and Elements in Civil Engineering
by Krzysztof Schabowicz
Materials 2021, 14(12), 3412; https://doi.org/10.3390/ma14123412 - 20 Jun 2021
Cited by 14 | Viewed by 4589
Abstract
This issue is proposed and organized as a means to present recent developments in the field of testing of materials in civil engineering. For this reason, the articles highlighted in this issue should relate to different aspects of testing of different materials in [...] Read more.
This issue is proposed and organized as a means to present recent developments in the field of testing of materials in civil engineering. For this reason, the articles highlighted in this issue should relate to different aspects of testing of different materials in civil engineering, from building materials and elements to building structures. The current trend in the development of materials testing in civil engineering is mainly concerned with the detection of flaws and defects in elements and structures using destructive, semi-destructive, and nondestructive testing. The trend, as in medicine, is toward designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Very interesting results with significance for building practices of testing of materials and elements in civil engineering were obtained. Full article
(This article belongs to the Special Issue Testing of Materials and Elements in Civil Engineering)
19 pages, 9059 KiB  
Article
A Cellulose-Derived Nanofibrous MnO2-TiO2-Carbon Composite as Anodic Material for Lithium-Ion Batteries
by Shun Li, Ming Yang, Guijin He, Dongmei Qi and Jianguo Huang
Materials 2021, 14(12), 3411; https://doi.org/10.3390/ma14123411 - 20 Jun 2021
Cited by 3 | Viewed by 2390
Abstract
A bio-inspired nanofibrous MnO2-TiO2-carbon composite was prepared by utilizing natural cellulosic substances (e.g., ordinary quantitative ashless filter paper) as both the carbon source and structural matrix. Mesoporous MnO2 nanosheets were densely immobilized on an ultrathin titania film precoated [...] Read more.
A bio-inspired nanofibrous MnO2-TiO2-carbon composite was prepared by utilizing natural cellulosic substances (e.g., ordinary quantitative ashless filter paper) as both the carbon source and structural matrix. Mesoporous MnO2 nanosheets were densely immobilized on an ultrathin titania film precoated with cellulose-derived carbon nanofibers, which gave a hierarchical MnO2-TiO2-carbon nanoarchitecture and exhibited excellent electrochemical performances when used as an anodic material for lithium-ion batteries. The MnO2-TiO2-carbon composite with a MnO2 content of 47.28 wt % exhibited a specific discharge capacity of 677 mAh g−1 after 130 repeated charge/discharge cycles at a current rate of 100 mA g−1. The contribution percentage of MnO2 in the composite material is equivalent to 95.1% of the theoretical capacity of MnO2 (1230 mAh g−1). The ultrathin TiO2 precoating layer with a thickness ca. 2 nm acts as a crucial interlayer that facilitates the growth of well-organized MnO2 nanosheets onto the surface of the titania-carbon nanofibers. Due to the interweaved network structures of the carbon nanofibers and the increased content of the immobilized MnO2, the exfoliation and aggregation, as well as the large volume change of the MnO2 nanosheets, are significantly inhibited; thus, the MnO2-TiO2-carbon electrodes displayed outstanding cycling performance and a reversible rate capability during the Li+ insertion/extraction processes. Full article
(This article belongs to the Special Issue Feature Paper in Section Materials Chemistry)
►▼ Show Figures

Figure 1

Figure 1
<p>Electron micrographs of the cellulose-derived MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% composite. (<b>a</b>) FE-SEM image of the composite showing nanofiber assemblies; (<b>b</b>) an individual composite material separated from the assemblies; (<b>c</b>) TEM image of an individual MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% composite; (<b>d</b>) partially magnified TEM image (marked by the red frame) showing the MnO<sub>2</sub> nanosheets with porous structures.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) STEM images of an individual MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% composite nanofiber with the corresponding EDS elemental mapping of (<b>c</b>) C, (<b>d</b>) Ti, (<b>e</b>) O and (<b>f</b>) Mn. Scale bars = 500 nm.</p> Full article ">Figure 3
<p>Electron micrographs of the MnO<sub>2</sub>-carbon-40.15% nanocomposite derived from a natural cellulose substance. (<b>a</b>) FE-SEM image of the sample, displaying nanofiber assemblies. (<b>b</b>) An individual composite nanofiber isolated from the assemblies. (<b>c</b>,<b>d</b>) The TEM images of an individual MnO<sub>2</sub>-carbon-40.15% nanofiber at different magnifications.</p> Full article ">Figure 3 Cont.
<p>Electron micrographs of the MnO<sub>2</sub>-carbon-40.15% nanocomposite derived from a natural cellulose substance. (<b>a</b>) FE-SEM image of the sample, displaying nanofiber assemblies. (<b>b</b>) An individual composite nanofiber isolated from the assemblies. (<b>c</b>,<b>d</b>) The TEM images of an individual MnO<sub>2</sub>-carbon-40.15% nanofiber at different magnifications.</p> Full article ">Figure 4
<p>(<b>a</b>–<b>c</b>) STEM images of an individual MnO<sub>2</sub>-carbon-40.15% composite with the corresponding EDS elemental mapping of (<b>d</b>) C, (<b>e</b>) O, and (<b>f</b>) Mn. Scale bars = 300 nm.</p> Full article ">Figure 4 Cont.
<p>(<b>a</b>–<b>c</b>) STEM images of an individual MnO<sub>2</sub>-carbon-40.15% composite with the corresponding EDS elemental mapping of (<b>d</b>) C, (<b>e</b>) O, and (<b>f</b>) Mn. Scale bars = 300 nm.</p> Full article ">Figure 5
<p>(<b>a</b>) X-ray diffraction patterns, (<b>b</b>) Raman spectra and (<b>c</b>) TGA curves of the samples. Curve i: MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28%; curve ii MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-37.81%: curve iii MnO<sub>2</sub>-carbon-40.15%; curve iv: MnO<sub>2</sub>-carbon-33.30%; curve v: TiO<sub>2</sub>-carbon; curve vi: MnO<sub>2</sub>-NPs. (<b>d</b>) High-resolution XPS spectra of Mn 2p regions of the MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% composite.</p> Full article ">Figure 6
<p>(<b>a</b>) Nitrogen adsorption–desorption isotherms and the (<b>b</b>) pore-size distribution curves of the MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% and MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-37.81% composites.</p> Full article ">Figure 7
<p>Cyclic voltammetry curves of (<b>a</b>) MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28%, (<b>b</b>) MnO<sub>2</sub>-carbon-40.15% composite and (<b>c</b>) MnO<sub>2</sub>-NPs tested in the initial four charge/discharge cycles at a scan rate of 0.2 mV s<sup>−1</sup> between 0.01 and 3 V (vs. Li/Li<sup>+</sup>).</p> Full article ">Figure 8
<p>Galvanostatic charge/discharge profiles of (<b>a</b>) MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28%, (<b>b</b>) MnO<sub>2</sub>-carbon-40.15%, (<b>c</b>) TiO<sub>2</sub>-carbon and (<b>d</b>) MnO<sub>2</sub>-NPs anode materials measured at a current density of 100 mA g<sup>−</sup><sup>1</sup> between 0.01 and 3.0 V.</p> Full article ">Figure 9
<p>(<b>a</b>) Cycling performances of MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28%, 37.81%, MnO<sub>2</sub>-carbon-40.15%, 33.30% composites, TiO<sub>2</sub>-carbon and MnO<sub>2</sub>-NPs electrodes at a current density of 100 mA g<sup>−1</sup> as well as the Coulombic efficiency curve of the MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28% composite. (<b>b</b>) Rate performances of the corresponding electrodes at various current rates.</p> Full article ">Figure 10
<p>Electrochemical impedance spectra (Nyquist plots) of the MnO<sub>2</sub>-TiO<sub>2</sub>-carbon-47.28%, MnO<sub>2</sub>-carbon-40.15% and TiO<sub>2</sub>-carbon electrodes after 200 charge/discharge cycles. The inset is the equivalent circuit model used to fit the impedance spectra.</p> Full article ">Scheme 1
<p>Schematic illustration of the fabrication processes of the MnO<sub>2</sub>-TiO<sub>2</sub>-carbon (<b>a</b>–<b>d</b>) and MnO<sub>2</sub>-carbon (<b>a</b>–<b>f</b>) composites derived from natural cellulosic substances. (<b>b</b>) The TiO<sub>2</sub> gel film coated cellulose nanofiber was obtained by means of a surface sol–gel process. (<b>c</b>) The TiO<sub>2</sub> coated carbon nanofiber and (<b>e</b>) the carbon nanofiber were fabricated through carbonization of the TiO<sub>2</sub> gel film coated cellulose nanofiber and the cellulose nanofiber in an argon atmosphere, respectively. (<b>d</b>) MnO<sub>2</sub>-TiO<sub>2</sub>-carbon and (<b>f</b>) MnO<sub>2</sub>-carbon were fabricated via a hydrothermal process by employing KMnO<sub>4</sub> as precursor.</p> Full article ">
9 pages, 2232 KiB  
Article
EPR Spectroscopy as a Tool to Characterize the Maturity Degree of Humic Acids
by Bozena Debska, Ewa Spychaj-Fabisiak, Wiesław Szulc, Renata Gaj and Magdalena Banach-Szott
Materials 2021, 14(12), 3410; https://doi.org/10.3390/ma14123410 - 20 Jun 2021
Cited by 7 | Viewed by 3527
Abstract
The major indicator of soil fertility and productivity are humic acids (HAs) arising from decomposition of organic matter. The structure and properties of HAs depend, among others climate factors, on soil and anthropogenic factors, i.e., methods of soil management. The purpose of the [...] Read more.
The major indicator of soil fertility and productivity are humic acids (HAs) arising from decomposition of organic matter. The structure and properties of HAs depend, among others climate factors, on soil and anthropogenic factors, i.e., methods of soil management. The purpose of the research undertaken in this paper is to study humic acids resulting from the decomposition of crop residues of wheat (Triticum aestivum L.) and plant material of thuja (Thuja plicata D.Don.ex. Lamb) using electron paramagnetic resonance (EPR) spectroscopy. In the present paper, we report EPR studies carried out on two types of HAs extracted from forest soil and incubated samples of plant material (mixture of wheat straw and roots), both without soil and mixed with soil. EPR signals obtained from these samples were subjected to numerical analysis, which showed that the EPR spectra of each sample could be deconvoluted into Lorentzian and Gaussian components. It can be shown that the origin of HAs has a significant impact on the parameters of their EPR spectra. The parameters of EPR spectra of humic acids depend strongly on their origin. The HA samples isolated from forest soils are characterized by higher spin concentration and lower peak-to-peak width of EPR spectra in comparison to those of HAs incubated from plant material. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>EPR spectra of the HAs extracted from forest soils (<b>a</b>) and isolated from incubated samples of plant material (<b>b</b>).</p> Full article ">Figure 2
<p>The deconvoluted EPR spectra recorded for samples: (<b>a</b>) extracted from forest soils and (<b>b</b>) isolated from incubated samples of plant material. Δ<span class="html-italic">B</span>—peak-to-peak width of experimental line. G—Gaussian; L—Lorentzian components; G + L—sum of both components. (The accuracy of the numerical fitting in this case is better than 0.99 correlation coefficient).</p> Full article ">Figure 3
<p>The parameters of EPR spectrum from <a href="#materials-14-03410-f002" class="html-fig">Figure 2</a>a as a function of microwave power: (<b>a</b>)/ line widths of Gaussian and Lorentzian components <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>B</mi> <mrow> <mi>G</mi> <mtext> </mtext> </mrow> </msub> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mo>Δ</mo> <msub> <mi>B</mi> <mi>L</mi> </msub> </mrow> </semantics></math> (<b>b</b>)/ A<sub>G</sub> and A<sub>L</sub> of Gaussian and Lorentzian components, respectively.</p> Full article ">Figure 4
<p>Florescence spectra (excitation 340 nm) of the HAs isolated from: (<b>a</b>) incubated samples of plant material, (<b>b</b>) forest soils.</p> Full article ">
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-299
Previous Issue
Next Issue
Back to TopTop