Mechanical Activation

This article reports the results of an investigation into the efficiency of mechanical activation to increase the reactivity in alkali activated mortar synthesized from low-grade clay. Mechanical activation significantly changed the structure of clay, increasing the specific surface area, and decreasing the particle size. The 7-day compressive strength of mortar synthesized from untreated clay was 31.7 MPa, which increased to 35.3 after 4 h milling. A further increase of grinding time to 8 h did not result in any increase in compressive strength which is attributed to a decrease in the workability. However, the extent of reactivity did significantly increase as determined from solid-state MAS NMR, FTIR, and EDS analyses. Solid-state MAS NMR results revealed the increased formation of Q 4 (2Al) silicon sites, which is correlated with improved reaction. Furthermore, the EDS and FTIR analysis results indicated greater incorporation of aluminium into the matrix structure with increased grinding time.

Lithium-ion batteries (LIBs) have revolutionized the portable electronic devices and electric vehicles (EV) and because of this huge demand, it is important to meet high power, high specific energy, and long cycle life. All mentioned characteristics are directly related to the choice of anode and cathode electrodes. Currently, graphite is used as anode, while lithium cobalt oxide serves as cathode dominantly. Although graphite can deliver ~ 370 mA h g-1 capacity without significant capacity decay for several cycles, however it is not enough to fulfill the requirements for many applications. Silicon with the theoretical capacity of about 10 times higher than graphite is a promising anode. However, this material suffers from huge volume expansion during cycling in addition to its intrinsic low conductivity. From the cathode viewpoint, the need for materials with less cobalt content is necessary. The resources for cobalt element is very limited while the price of cobalt increasing. Furthermore, cobalt is known as toxic element. Therefore, substitution of cobalt with other elements such as manganese and nickel is necessary. Lithium nickel manganese cobalt oxide (NMC) cathode family materials are introduced following this idea. Here in this thesis, two different approaches are introduced to harness the problems associated with silicon anodes. The first approach is the core/shell design and the second one is the silicon/graphite nanocomposite with tailored structure and engineered voids. Both of these designs can be synthesized easily without complicated synthesis steps and harmful chemicals. They have the potential of being commercialized and they do not need expensive equipment. The silicon anodes have been tested successfully in the half-cell coin cells. As for the cathode side, two different members of NMC family materials (NMC333 and NMC532) have been tested. To enhance their electrochemical properties and rate capabilities, a facile surface modification using phosphoric acid was employed. This technique resulted in the formation of thin lithium phosphate coating around the particle. The electrodes performed very well in half-cell configuration. It is expected by utilizing the proposed cathode and anode materials in full-cell set up, a high performance battery with fast charge ability is obtained.

In this study, effect of mechanical activation in planetary ball mill and disc mill, on carbothermic reduction of celestite ore with coke was investigated. Celestite ore (96% SrSO 4) from Sivas district was blended with excess metallurgical coke and mechanically activated for 1, 5, 15 and 45 min. Mechanically activated blends were analyzed by Particle Size Analyzer, Thermal Gravimetric Analyzer (TGA), Differential Scanning Calorimetric Analyzer (DSC), and X-Ray Diffractometer (XRD). The finest particles were obtained at 45 min disc milling, of which d50 was 1.30 µm. TGA and DSC analyses showed that the reaction temperature was decreasing from 973°C to 892°C, by 1 min disc milling and 45 min planetary ball milling, respectively. XRD peaks broadened and peak intensities decreased by extending the mechanical activation time in both type of milling processes. All of the mechanically activated powders were roasted at 900, 1000, and 1100°C. According to XRD analyses; it is possible to see some peaks of strontium sulphide (SrS) after roasting at 900 and 1000°C, however, at 1100°C carbide formation is obtained.

The study developed new, novel, and cheaper materials as micronutrients for plants. These studies showed that some copper ore can be utilized as a cheaper source of copper micronutrients. This method would be economically feasible for agriculture. The study has shown that roasting increased the recovery of copper from different ores differently. As the roasting time and temperature increase, the leaching of copper will also increase. The leaching of copper maximum in a sample was in the order of leaching of copper in three ores is as Sample C>sample D>Waziristan chalcopyrite. The experiments showed that the untreated raw oxidized copper ore show significant leaching which is 9.5% for saline and 35.5% for fertile soils respectively. This is an important finding which showed that oxidized copper ores can directly be used as slow-release micronutrients. A cheap process based on grinding to 200 mesh would be feasible. It is further seen that roasting at 750 o C is suitable for treating sulfide ores. The acidification has shown much improvement in leaching and providing micronutrients to the soil.

Cementation is one of the simplest and low cost methods. It is widely used in industry for recovery of metal and removal of metal ions from dilute wastes, and for purification of solutions. In the present investigations, copper powder was prepared by cementation from a copper sulphate solution of 0.08 M by slowly adding the activated iron powder. Activation of iron powder was done by milling it in an attrition mill. Kinetics of the cementation reaction was evaluated by measuring the rate of decrease of metal ions concentration in the solution by spectro-photometry. Studies of the results have shown significant improvement in the cementation rate. Cemented copper powder obtained was characterized for its purity, particle size, grain size and morphology by EDS, laser particle size analyser, XRD studies, TEM and SEM, respectively. The cemented copper powder was found to have particle size in the range of 180 nm to 46 μm having polygon shape. The average grain size in the powder particles was found to be 54 nm. Few core-shell particles with entrapped iron in copper particles have also been detected.

Burnt clay pozzolana produced from a clay deposit at Mankranso in Ghana has been activated by mechanical means through roll milling and ball milling as well as chemically by the addition of 1% - 4% m/m Na2SO4. The pozzolana sample was chemically suitable with total SiO2 + Al2O3 + Fe2O3 content ≥70% as stipulated by the ASTM C 618 standard. The particle sizes, surface characteristics and specific surface areas obtained by the types/degrees of milling were analyzed and their effect on the strength development of Portland pozzolana cement mortar cubes prepared from the pozzolana samples was evaluated. Compressive strengths obtained showed that the activated pozzolana could be used to replace up to 40% ordinary Portland cement (OPC) and satisfy the EN 197-1 and ASTM C 595 standard requirements. Comparatively, the chemically activated pozzolana cement mortars attained higher compressive strengths than the mechanically activated pozzolana cement mortars at equal ages of tests and the same pozzolana content levels. The chemically activated pozzolana cement mortars attained higher 2 day strengths than OPC at sulphate concentrations of 3% and 4% for all pozzolana content levels between 30% - 40%. SEM image and insoluble residue in HCl of a 2 day old chemically activated pozzolana cement paste confirmed dissolution of fine pozzolana particles in the alkaline media which influenced higher early age strengths. The highest 28 day compressive strength of 54.2 MPa was obtained at 4% sulphate concentration and 30% pozzolana content for the chemically activated pozzolana. The highest 28 days compressive strength for the mechanically activated pozzolana was 35.6 MPa—obtained for the roll milled product at 30% pozzolana content. Standard consistence of the pozzolana cement pastes increased with increasing pozzolana fineness and pozzolana content. Increasing Na2SO4 concentration however had no effect on standard consistence. Setting times decreased with increase in both fineness and sulphate concentration. The EN 197-1 standard for initial setting time was satisfied by the chemically activated pozzolana cement mortars at all pozzolana content levels. Pozzolana samples activated by roll milling and 36 h ball milling had faster initial setting times than the EN 196-1 standard at all pozzolana content levels beyond 30%. The ASTM C 595 requirement for initial set was however satisfied at all pozzolana content levels.

Objective(s): Hardystonite (HT) is Zn-modified silicate bioceramics with promising results for bone tissue regeneration.
However, HT possesses no obvious apatite formation. Thus, in this study we incorporated Sr and Ti into HT to
prepare Sr-Ti-hardystonite (Sr-Ti-HT) nanocomposite and evaluated its in vitro bioactivity with the purpose of
developing a more bioactive bone substitute material.
Materials and methods: The HT and Sr-Ti-HT were prepared by mechanical milling and subsequent heat treatment.
Calcium oxide (CaO), zinc oxide (ZnO) and silicon dioxide (SiO2) (all from Merck) were mixed with molar ratio of 2:1:2.
The mixture of powders mixture was then milled in a planetary ball mill for 20 h. In the milling run, the ball-to-powder
weight ratio was 10:1 and the rotational speed was 200 rpm. After synthesis of HT, 3% nanotitanium dioxide (TiO2,
Degussa) and 3% strontium carbonate (SrCO3, Merck) were added to HT and then the mixture was ball milled and
calcined at 1150°C for 6 h. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), Transmission electron
microscopy (TEM) and Fourier transform infra-red spectroscopy (FT-IR) performed to characterize the powders.
Results: XRD and FT-IR confirmed the crystal phase and silicate structure of HT and TEM images demonstrated the
nanostructure of powders. Further, Sr-Ti-HT induced apatite formation and showed a higher human mesenchymal stem
cell (hMSCs) adhesion and proliferation compared to HT.
Conclusion: Our study revealed that Sr-Ti-HT with a nanostructured crystal structure of 50 nm, can be prepared by
mechanical activation to use as biomaterials for orthopedic applications.

The study of kaolinite surfaces is of industrial importance. In this work we report the application of chemometrics to the study of modified kaolinite surfaces. DRIFT spectra of mechanochemically activated kaolinites (Kiralhegy, Zettlitz, Szegi and Birdwood) were analysed using, Principal Component Analysis (PCA), and multi-criteria decision making (MCDM) methods, PROMETHEE and GAIA. The clear discrimination of the Kiralhegy spectral objects on the two PC scores plots (400-800 and 800-2030 cm-1) indicated the dominance of quartz. Importantly, no ordering of any spectral objects appeared to be related to grinding time in the PC plots of these spectral regions. Thus, neither the kaolinite nor the quartz, are systematically responsive to grinding time according to the spectral criteria investigated. The third spectral region (2600-3800 cm-1 – OH vibrations), showed apparent systematic ordering of the Kiralhegy and, to a lesser extent, Zettlitz spectral objects with grinding time. This was attributed to the effect of the natural quartz on the delamination of kaolinite and the accompanying phenomena (i.e. formation of kaolinite spheres and water). With the MCDM methods, it was shown that useful information on the basis of chemical composition, physical properties and grinding time can be obtained. For example, the effects of the minor chemical components (e.g. MgO, K 2 O etc) indicated that the Birdwood kaolinite is arguably the most pure one analysed. In another MCDM experiment, some support was obtained for the apparent trend with grinding time noted in the PC plot of the OH spectral region.

Activation methods and curing regimes have crucial effects on the strength of mortars and concretes. The objective of this investigation is to examine the early and later compressive strength of activated ordinary Portland cement (OPC)–ground granulated blast-furnace slag (GGBFS) mortars and identify the most effective activation technique. The methods of activation used were thermal, mechanical and thermal–mechanical combined. Two curing regimes were adopted and five groups of mortars were prepared. It was observed that OPC–GGBFS mortars have greater sensitivity to OPC mortars against the curing regimes. However, the study revealed that there was no particular activation method which when used gave the best results for both early and later strengths and did not cause strength loss. It also proved that the most effective activation method for early strength is a combination of both the thermal and mechanical, while for later strengths, none of the activation methods was recommended.

Activation methods and curing regimes have crucial effects on the strength of mortars and concretes. The objective of this investigation is to examine the early and later compressive strength of activated ordinary Portland cement (OPC)-ground granulated blast-furnace slag (GGBFS) mortars and identify the most effective activation technique. The methods of activation used were thermal, mechanical and thermal-mechanical combined. Two curing regimes were adopted and five groups of mortars were prepared. It was observed that OPC-GGBFS mortars have greater sensitivity to OPC mortars against the curing regimes. However, the study revealed that there was no particular activation method which when used gave the best results for both early and later strengths and did not cause strength loss. It also proved that the most effective activation method for early strength is a combination of both the thermal and mechanical, while for later strengths, none of the activation methods was recommended. © 2010 Elsevier Ltd.

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The manuscript investigates the effect of mechanical activation by the wavedisintegration
method on the pre-biotic properties of the dietary supplement
composition of wheat germ (Vitazar dietary supplement), arabinogalactan of
Dahurian larch (Flarabin dietary supplement), and selenium xanthan (Seleksen
dietary supplement). The authors revealed the changes in the phase state of the
crystal lattices of the nanopowders of the studied biological objects. The manuscript
determines the parameters of the accumulation of lactobacilli and bifidobacteria
biomass during the fermentation of substrates containing milk, and the composition of
dietary supplements in the concentration range of 1-5%. The manuscript shows the
possibility of reducing the accumulation time of active cells to concentrations of not
less than 109 CFU/g of lactobacilli L. Сasei subsp. Rhamnosus, as well as consortia
consisting of lactobacilli: L. acidophilus, L. plantarum, L. fermentum, of
bifidobacteria: Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium
adolescentis; of lactobacilli and bifidobacteria: L. Сasei subsp. Rhamnosus, L.
acidophilus, L. plantarum, L. fermentum, Bifidobacterium bifidum, Bifidobacterium
longum, Bifidobacterium adolescentis L. The manuscript studies the process of
biomass accumulation of probiotic microflora and its metabolites (lactic acid) on
substrates containing the composition of dietary supplements in mechanically
activated form. The authors established that being a source of dietary fibers, polyand
oligosaccharides, vitamins, mineral substances, antioxidants, the composition
under study can support the active development of lactobacilli and bifidobacteria,
forming a favorable environment for them. The authors recorded accumulation of
microflora metabolites by an increase in the titration rate, as well as by a change in
CFU in 1 g of the fermented substrate. In the study of the fermentation process'
kinetics, the main stages of the fermentation process were identified, the lag-phase
time was reduced to 1-1.2 hours, activation of the exponential phase of the process,
and a rather long period of growth retardation and a stable state of the biosystem
with preservation of probiotic microorganism concentration not less than 109 CFU/g.