- Chemical Engineering and Advanced Materials
Newcastle University
Merz Court
Newcastle upon Tyne
NE1 7RU
UK - +44 191 208 7913
- Chemistry, Chemical Engineering, Nanotechnology, Nanoscience, Environmental Engineering, Nanomechanics, and 14 moreNanoindentation, Materials Science, Renewable Energy, Surface Coatings, Tribology, Glass, Composite Materials and Structures, Biomaterials, X-ray Diffraction, Filtration, Porous Materials, Microelectronic Reliability, Optical Coatings, and Finite Element Analysis (Engineering)edit
- Currently Cookson Group Chair of Materials Engineering at Newcastle University where I have been working for over twe... moreCurrently Cookson Group Chair of Materials Engineering at Newcastle University where I have been working for over twenty years on the mechanics of coatings and layered materials. Previously I ran coating facilities and undertook contract research in Surface Engineering at AEA Technology, Harwell Laboratory.edit
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PolyHIPEs (polymers synthesized within high internal phase emulsions) are porous materials with high specific surface area which suggests their use in ion exchange applications. We have successfully synthesized and functionalized such... more
PolyHIPEs (polymers synthesized within high internal phase emulsions) are porous materials with high specific surface area which suggests their use in ion exchange applications. We have successfully synthesized and functionalized such materials to make then hydrophilic by mixing an oil phase and an aqueous phase containing deionized water and sulphuric acid. The PolyHIPE samples were also subjected to a further microwave-assisted post-sulphonation process to increase hydrophilicity and water uptake. Post sulphonation results in a higher concentration of benzenesulphonic acid groups which are necessary for ion exchange. PolyHIPE beads processed in this manner were able to remove low concentrations (∼20mg/l) of nickel and copper ions from solution with high removal efficiency (80-95%) depending on the initial pH of the water. However, recovery of the metal through regeneration at different pH levels was less successful.
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3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials... more
3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials such as polylactic acid (PLA), polystyrene and nylon are used. This study explores how the process parameters, e.g. build orientation and infill pattern/density, affect the mechanical response of PLA samples produced using FFF. Digital image correlation (DIC) was employed to get full-field surface-strain measurements. The results show the influence of build orientation and infill density is significant. For on-edge orientation, the tensile strength and Young’s modulus were 55 MPa and 3.5 GPa respectively, which were about 91% and 40% less for the upright orientation, demonstrating a significant anisotropy. The tensile strength and Young’s modulus increased with increasing infill density. In contrast, different infill patterns have no significant ef...
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This paper presents a numerical investigation of the effects of lamination orientation on the fracture behaviour of rectangular steel wires for civil engineering applications using fi nite element (FE) analysis. The presence of... more
This paper presents a numerical investigation of the effects of lamination orientation on the fracture behaviour of rectangular steel wires for civil engineering applications using fi nite element (FE) analysis. The presence of mid-thickness across-the-width lamination changes the cup and cone fracture shape exhibited by the lamination-free wire to a V-shaped fracture with an opening at the bottom/pointed end of the V-shape at the mid-thickness across-the-width lamination location. The presence of mid-width across-the-thickness lamination changes the cup and cone fracture shape of the lamination-free wire without an opening to a cup and cone fracture shape with an opening at the lamination location. The FE fracture behaviour prediction approach adopted in this work provides an understanding of the effects of lamination orientation on the fracture behaviour of wires for civil engineering applications which cannot be understood through experimental investigations because it is impossi...
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The effects of the miniature channel-shaped scratches not detectable by the present inline elec-tromagnetic defect detection system employed for wires ’ surface defect detection on the fracture behaviour of the wires for civil engineering... more
The effects of the miniature channel-shaped scratches not detectable by the present inline elec-tromagnetic defect detection system employed for wires ’ surface defect detection on the fracture behaviour of the wires for civil engineering applications were investigated numerically. Finite element analysis revealed that both miniature channel-shaped across-the-thickness and across-the-width scratches change the fracture behaviour of the wires in terms of the fracture initiation locations and fracture process sequence. However, miniature across-the-thickness scratches does not affect the fracture shape of the wire while miniature across-the-width scratches changed the wires ’ cup and cone fracture to a fracture shape with a predominantly fl at fracture. These results provide an understanding of the fracture behaviour of wires with miniature scratches and serve as an alternative or a complimentary tools to experimental or fractographic failure analysis of wires with miniatures scratche...
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ABSTRACT
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Steel wires are used for pre-stressing concrete structural units and for the construction of suspension bridges among other applications in civil engineering. The reverse bending and straightening of wires by rollers is employed as a... more
Steel wires are used for pre-stressing concrete structural units and for the construction of suspension bridges among other applications in civil engineering. The reverse bending and straightening of wires by rollers is employed as a routine quality check to detect laminations in wires. Experimental work on the reverse bending of wires and Finite Element (FE) simulation of bending of wires has been investigated previously but the simulation of the reverse bending and straightening of wire has not been studied in detail. Also, the FE simulation of the bending of wire round a mandrel reported in the literature was conducted by pinning the nodes on one end of the wire to the mandrel and applying a concentrated load to the free end of the wire to bend the wire, which does not replicate the bending process in practice. In this paper, three dimensional FE simulation of the reverse bending of steel wires conducted as a part of the research to investigate the effects of the combination of r...
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Modification of the chemomechanical behaviour of the surface of sapphire by ion implantation to improve its near-surface mechanical properties has been investigated. 300 keV Ti+ ions at various doses were implanted and the concentration... more
Modification of the chemomechanical behaviour of the surface of sapphire by ion implantation to improve its near-surface mechanical properties has been investigated. 300 keV Ti+ ions at various doses were implanted and the concentration and damage profiles characterised using Rutherford Backscattering (RBS). At high doses (≥ 3 × 1016 Ti+ cm−2), a surface amorphous layer is formed due to implantation-induced damage. Nanoindentation was used to determine the hardness behaviour of the ion-implanted layer. Hardness increases at low implantation doses, associated with implantation-induced damage, but it is also observed that chemomechanical softening of the surface is reduced due to the removal of adsorbed water. In situ Raman scattering measurements demonstrate this removal at low doses and the re-establishment of the adsorbed water layer at high doses. The adsorption process is changed due to the introduction of carbon into the sapphire surface during implantation. For the optimum-impl...
Atomized spray plasma deposition (ASPD) provides a single-step, low-temperature, and dry approach for the preparation of high refractive index hybrid polymer or polymer–inorganic nanocomposite coatings. Refractive indices as high as 1.936... more
Atomized spray plasma deposition (ASPD) provides a single-step, low-temperature, and dry approach for the preparation of high refractive index hybrid polymer or polymer–inorganic nanocomposite coatings. Refractive indices as high as 1.936 at 635 nm wavelength have been obtained for ASPD 4-bromostyrene/toluene–TiO2 nanocomposite layers containing low titania loadings. Thin films with any desired refractive index up to 1.936 can be easily deposited onto a variety of substrates by varying the precursor mixture composition. ASPD overcomes disadvantages commonly associated with alternative fabrication methods for depositing high refractive index coatings (elevated temperatures, wet processes, UV curing steps, and much greater inorganic loadings).
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Surface interactions and modifications have become increasingly critical for a broad range of manufacturing technologies. Applications can be in traditional manufacturing sectors and in manufacturing processes for microelectronics,... more
Surface interactions and modifications have become increasingly critical for a broad range of manufacturing technologies. Applications can be in traditional manufacturing sectors and in manufacturing processes for microelectronics, optics, and micro-/nanoelectromechanical systems (MEMS/NEMS). Many applications demand engineered surfaces at different length scales that will function under extreme conditions. The goal of this book is to advance understanding of these diverse applications. In the field of tribological coatings, the increasing sophistication of coating processes to provide control over materials and composition gradients is being exploited to tailor properties such as adhesion, stresses, thermal barrier and wear resistance. Understanding the influence of nanostructure in coatings has become pivotal in the development of hard and wear-resistant materials. Modeling and simulation continue to make contributions to the understanding and predication of surface properties and...
Background Fatigue failure criteria for fibre reinforced polymer composites used in the design of marine structures are based on the micromechanical behaviour (e.g. stiffness properties) of their constituents. In the literature, there is... more
Background Fatigue failure criteria for fibre reinforced polymer composites used in the design of marine structures are based on the micromechanical behaviour (e.g. stiffness properties) of their constituents. In the literature, there is a lack of information regarding the stiffness degradation of fibres, polymer matrix and fibre/matrix interface regions affected by environmental fatigue. Objective The aim of present study is to characterize the stiffness properties of composite constituents using the nanoindentation technique when fatigue failure of composites is due to the combined effect of sea water exposure and cyclic mechanical loads. Methods In the present study, the nanoindentation technique was used to characterize the stiffness properties of composite constituents where the effects of neighbouring phases, material pile up and viscoplasticity properties of the polymer matrix are corrected by finite element simulation. Results The use of finite element simulation in conjunct...
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Glass fibre reinforced polymer composites are frequently used in marine applications where the combined effects of cyclic loads and the seawater environment limit their fatigue life. This paper aims to demonstrate the degradation that... more
Glass fibre reinforced polymer composites are frequently used in marine applications where the combined effects of cyclic loads and the seawater environment limit their fatigue life. This paper aims to demonstrate the degradation that seawater causes to the stiffness of the composites. Three-point bending fatigue properties of cross-ply woven glass fibre composites commonly used to manufacture tidal turbine blades are reported for both wet and dry conditions. Failure analysis based on the Digital Image Correlation method was performed to identify damaged zones on the test coupon surface and to follow failure progression during the fatigue tests. To characterize the damage in the composite, stiffness degradation has been monitored during the entire fatigue history. Scanning electron microscopy was used to identify multiple failure mechanisms on the specimen fracture surface. In addition, for further verification of microscopy results, X-Ray Micro-computed tomography, was used to char...
Although the literature is abundant with the experimental methods to characterize mechanical behavior of parts made by fused filament fabrication 3D printing, less attention has been paid in using computational models to predict the... more
Although the literature is abundant with the experimental methods to characterize mechanical behavior of parts made by fused filament fabrication 3D printing, less attention has been paid in using computational models to predict the mechanical properties of these parts. In the present paper, a numerical homogenization technique is developed to predict the effect of printing process parameters on the elastic response of 3D printed parts with cellular lattice structures. The development of finite element computational models of printed parts is based on a multi scale approach. Initially, at the micro scale level, the analysis of micro-mechanical models of a representative volume element is used to calculate the effective orthotropic properties. The finite element models include different infill densities and building/raster orientation maintaining the bonded region between the adjacent fibers and layers. The elastic constants obtained by this method are then used as an input for the c...
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Conventional scratch adhesion testing of hard ceramic coatings on hard substrates requires such high critical loads that the deformation behavior of the substrate is assessed more than the behavior of the film. An alternative is to use... more
Conventional scratch adhesion testing of hard ceramic coatings on hard substrates requires such high critical loads that the deformation behavior of the substrate is assessed more than the behavior of the film. An alternative is to use fixed-load multi-pass testing, which ...
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Graphene quantum dots (GQDs), a novel type of zero-dimensional fluorescent materials, have gained considerable attention owing to their unique optical properties, size and quantum confinement. However, their high cost and low yield remain... more
Graphene quantum dots (GQDs), a novel type of zero-dimensional fluorescent materials, have gained considerable attention owing to their unique optical properties, size and quantum confinement. However, their high cost and low yield remain open challenges for practical applications. In this work, a low cost, green and renewable biomass resource is utilised for the high yield synthesis of GQDs via microwave treatment. The synthesis approach involves oxidative cutting of short range ordered carbon derived from pyrolysis of biomass waste. The GQDs are successfully synthesised with a high yield of over 84%, the highest value reported to date for biomass derived GQDs. As prepared GQDs are highly hydrophilic and exhibit unique excitation independent photoluminescence emission, attributed to their single-emission fluorescence centre. As prepared GQDs are further modified by simple hydrothermal treatment and exhibit pronounced optical properties with a high quantum yield of 0.23. These modif...
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3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials... more
3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials such as polylactic acid (PLA), polystyrene and nylon are used. This study explores how the process parameters, e.g. build orientation and infill pattern/density, affect the mechanical response of PLA samples produced using FFF. Digital image correlation (DIC) was employed to get full-field surface-strain measurements. The results show the influence of build orientation and infill density is significant. For on-edge orientation, the tensile strength and Young’s modulus were 55 MPa and 3.5 GPa respectively, which were about 91% and 40% less for the upright orientation, demonstrating a significant anisotropy. The tensile strength and Young’s modulus increased with increasing infill density. In contrast, different infill patterns have no significant ef...
The purpose of this research was to determine which environmental factors within the pen space differ between the locations where pigs choose to lie and areas they avoid. Data on external weather conditions and the construction parameters... more
The purpose of this research was to determine which environmental factors within the pen space differ between the locations where pigs choose to lie and areas they avoid. Data on external weather conditions and the construction parameters for an existing commercial finishing pig building were input into a Dynamic Thermal (DT) model generating heat flow and surface temperature patterns in the structure and these were then input into a Computational Fluid Dynamics (CFD) model to generate data on the theoretical spatial patterns of temperature and air velocity within one room of this building on a specified day. The exact location of each pig in six selected pens within this room was taken from images from ceiling-mounted video cameras at four representative time points across the day. Using extracted air velocity and temperature data at the height of 0.64 m above the floor and a grid of approximately 600 mm to create a series of ‘cells’, the effective draught temperature (TED) was cal...
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ABSTRACTThe process-induced stress in interconnects within integrated circuits (IC) has a direct influence on the mean time to failure of the devices. Since measurement of stress in individual metallised lines is not possible by existing... more
ABSTRACTThe process-induced stress in interconnects within integrated circuits (IC) has a direct influence on the mean time to failure of the devices. Since measurement of stress in individual metallised lines is not possible by existing techniques, another approach has been adopted where a test structure is generated during fabrication based on a micro-rotating cantilever sensor. To support the design, finite element modeling (FEM) has been performed. By comparing the rotation predicted by FEM simulations and that observed experimentally, a clear discrepancy is observed which is critically dependent on the details of the sensor design, the pattern transfer of the lithographic process and on the dry etching processing.
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Strain engineering is used to maintain Moore's Law in scaled CMOS devices and as a technology booster for More-than-Moore devices in the nanoelectronics era. Strain is crucial because of its... more
Strain engineering is used to maintain Moore's Law in scaled CMOS devices and as a technology booster for More-than-Moore devices in the nanoelectronics era. Strain is crucial because of its ability to increase electron and hole mobilities in Si. However, accurate correlations ...
Research Interests: Materials Engineering, Materials Science, Raman Spectroscopy, Atomic Force Microscopy, Sample Preparation, and 11 moreNanowires, Finite element modelling, Data Collection, Strain Measurement, Silicon on Insulator, Surface Morphology, Tip Enhanced Raman Spectroscopy, High Resolution, Spatial resolution, Materials Processing, and Silicon Germanium
Hardness response of electroplated nickel coatings on copper substrates was studied over a range of applied loads and two decades of indentation depths. The hardness values were determined experimentally using a combination of... more
Hardness response of electroplated nickel coatings on copper substrates was studied over a range of applied loads and two decades of indentation depths. The hardness values were determined experimentally using a combination of conventional Vickers testing and microhardness measurements. The results were analysed using the work-of-indentation model for the hardness of coated systems, which was originally proposed and applied by the authors to the study of hard ceramic layers on steel substrates.