Dermot Brabazon

Abstract The modeling and simulation of laser surface processing enables the prediction of the process response at certain levels of input and control parameters. The process response can be optimized by the selection of the appropriate levels of input parameters. Experimental design techniques allow modeling of process input parameters and output response, and provides a mathematical relationship that is able to predict a desired response at certain input parameters. In this chapter, a review of the methods for the experimental development of laser processing is presented. Detailed introduction and methodology for Design of Experiments (DoE) technique is presented for laser processing. Specific examples of the use of experimental design techniques for process response modeling and optimization are presented for Laser Cladding, Laser Surface Melting, and Laser Shock Peening.

The selective extraction of specific proteins is of significant interest within the fields of proteomics and glycoproteomics. One approach to obtain selective extraction is to utilise solid phase extraction (SPE) columns [1], whereby the column stationary phase incorporates a selective ligand (e.g. a selective protein for efficient trap and release of the target). Recent results have shown that the covalent attachment of 20 nm gold based nano-particles (AuNP) on polymer monolith-based stationary phases can lead to a significant increase in surface area, chemical functionality, and, correspondingly, an increase in the column’s efficiency. In addition, the immobilisation chemistry of proteins on gold based nanoparticles is well known [2] and, in many instances, the protein-NP interaction confers additional stability to the protein [4]. The use of nanoparticles as stationary phases in chemical and biological separation has also been noted [5] and has wide scope for practical applicatio...

Exergy analysis has been applied to desalination membrane processes in an effort to characterise energy consumption and to optimise energy efficiency. Several models have been used to this end in the literature. One assumption that is common in these analyses is that of ideal solution behavior. However, seawater and other aqueous solutions of interest do not behave ideally. Indeed, even when ideal behavior is not assumed, there are several approaches to calculate these activity values, which are typically a function of the molality and ionic strength of the electrolytic solution. What is not clear from the published literature is the impact that the choice of activity calculation model has on the exergy analysis results. The objective of this research was to undertake the exergy analysis of a seawater membrane desalination plant using the Szargut chemical exergy approach and to compare the activity calculation approaches. The chemical exergy of the seawater was calculated using seve...

The capability of 3D printing technologies for direct production of complex 3D structures in a single step has recently attracted an ever increasing interest within the field of microfluidics. Recently, ultrafast lasers have also allowed developing new methods for production of internal microfluidic channels within the bulk of glass and polymer materials by direct internal 3D laser writing. This review critically summarizes the latest advances in the production of microfluidic 3D structures by using 3D printing technologies and direct internal 3D laser writing fabrication methods. Current applications of these rapid prototyped microfluidic platforms in biology will be also discussed. These include imaging of cells and living organisms, electrochemical detection of viruses and neurotransmitters, and studies in drug transport and induced-release of adenosine triphosphate from erythrocytes.

Researchers have developed techniques for multi-layered fabrication of microfluidic chips which allow for increased scope of channel geometries and associated improved sensing capabilities. In these techniques, slits have been fabricated in thin layers of polymer or ...

Implant-associated infection is a major source of morbidity in orthopaedic surgery. There has been extensive research into the development of materials that prevent biofilm formation, and hence, reduce the risk of infection. Silver nanoparticle technology is receiving much interest in the field of orthopaedics for its antimicrobial properties, and the results of studies to date are encouraging. Antimicrobial effects have been seen when silver nanoparticles are used in trauma implants, tumour prostheses, bone cement, and also when combined with hydroxyapatite coatings. Although there are promising results with in vitro and in vivo studies, the number of clinical studies remains small. Future studies will be required to explore further the possible side effects associated with silver nanoparticles, to ensure their use in an effective and biocompatible manner. Here we present a review of the current literature relating to the production of nanosilver for medical use, and its orthopaedi...

Ceramic particles generally have poor wettability by liquid metal, leading to a major drawback in fabrication of cast metal matrix composites (MMCs). In this work, the effect of 1 wt. % of Ca, Mg, Si, Ti, Zn and Zr interfacial-active alloying elements was studied on the incorporation of micron-sized SiC particles into the molten pure aluminum using the vortex casting method at 680 degC. The results indicated that Ti, Zr, Zn and Si were not positively effective in improving particulate incorporation, while Ca and especially Mg were very efficient at increasing the incorporation of ceramic particles into the molten Al. Also, it was revealed that Al 3 Ti, and Al 3 Zr intermetallic phases were formed for samples containing Ti and Zr, making hybrid MMCs with a higher amount of hardness. Finally, it was found that a reaction layer between Al and SiC particles was formed at the Al/SiC interface for all of the samples, expect for the ones containing Si and Ti, indicating that for most of the samples at 680 degC an exothermic reaction took place between the Al and SiC particles.

The formation of a uniform nickel phosphorous (Ni–P) electroless (EL) coating on micron-sized SiC particles was investigated in this study. Metal coated ceramic particles could be used in applications including as the fabrication of cast metal matrix composites.Such ceramic particles have a better wettability in molten metal. In this work, the effects of EL coating parameters, SiC particle size and morphology on the coating uniformity and mechanical bonding at the SiC/Ni–P interface were studied. The results indicated that etching treatment was very effective (especially for coarse powders) on the mechanical bonding at the interface. Theoptimum values of bath temperature and pH were determined to be 50 +/- 2 degC and 8 +/- 0.2 degC, respectively. The best uniformity and mechanical bonding were obtained for SiC particles with average particle size of 80 μm (considered relatively as coarse powders in this study). The ball milling of SiC particles (with the average particle size of 80 μm) for 1 h led to the formation of a multi-modal particle size distribution which resulted in a non-uniform quality of particulate coating. The larger SiC particles after ball milling were more completely covered by the Ni–P coating compared to the smaller more fragmented particles. The smaller ceramic particles processed via Ni–P EL coating lead to formation of segregated clusters of Ni–P and therefore such ceramic particles contained many uncoated parts.

The degree of the biocompatibility of polycarbonate (PC) polymer used as biomaterial can be controlled by surface modication for various biomedical engineering applications. In the past, PC samples were treated by ex-cimer laser for surface reorganization however associated process alteration of bulk properties is reported. Extreme ultraviolet radiation can be employed in order to avoid bulk material alteration due to its limited penetration. In this study, a 10 Hz laser-plasma EUV source based on a double-stream gas-pu target irradiated with a 3 ns and 0.8 J Nd:YAG laser pulse was used to irradiate PC samples. The PC samples were irradiated with dierent number of EUV shots. Pristine and EUV treated samples were investigated by scanning electron microscopy and atomic force microscopy for detailed morphological characterization of micropatterns introduced by the EUV irradiation. Associated chemical modications were investigated by X-ray photoelectron spectroscopy. Pronounced wall-type micro-and nanostructures appeared on the EUV modied surface resulting in a change of surface roughness and wettability.

The direct thermal method is used for the creation of globular microstructures suitable for semi-solid metal forming. In this paper, both simulation and experimental results using direct thermal method are presented. ProCAST® software was used to estimate temperature distribution inside the aluminum billet. In validation work, molten aluminum A356 was poured into metallic copper tube molds and cooled down to the semi-solid temperature before being quenched in water at room temperature. The effect of pouring temperatures of 630°C, 650°C, 665°C, 680°C and holding times of 45 s and 60 s on the microstructure of aluminum A356 alloy were investigated. The simulation results showed that the average temperature rate within the copper mold, from initial pouring temperature to just before quenching, was approximately 1°C/s. Examination of the solidified microstructures showed that the microstructure was more spherical when lower pouring temperatures and holding periods were used. From the micrographs it was found that the most globular and smallest structures were achieved at processing parameters of 630°C and 45 s.

This paper presents the effects of different cooling rates on thermal profiles and microstructures of aluminum 7075. The 7075 alloy was heated in a graphite crucible to 750°C. In the experimental work two thermocouples were used to record the temperatures at the center and 30mm from the center of the graphite crucible. A slow cooling rate condition was achieved by placing the crucible into a chamber with Kaowool insulation. A higher cooling rate was achieved by placing the crucible in open atmosphere with controlled air flow over the crucible. The slow and high cooling rates were 0.03°C/s and 0.4°C/s respectively. The Data Acquisition (DAQ) system implemented using LabVIEW software was used to record the temperature-time profiles. The enthalpy of phase change at each temperature was estimated from the cooling curves. The changes of cooling rate were directly related to phase transformation including at liquidus, eutectic and solidus temperatures. The dendritic coherency point (DCP) was determined from analysis of the temperature difference between two thermocouples. The formation of DCP was found to be delayed with use of the slow cooling rate. DCP occurred at 615.2°C (0.75 fraction solid) for the slow cooling rate and at 633.1°C (0.3 fraction solid) for the higher cooling rate. The microstructure features were also found to alter significantly with the different cooling rates used. The microstructure was more spheroidal for the slow cooling rate compared with the higher cooling rate.

The evolution of microstructure affect from different pouring temperatures and holding times using a direct thermal method is presented in this paper. The direct thermal method is one of the thermal techniques which are used to produce semi-solid metal feedstock. In this experimental work, aluminium 7075 alloy was used. The experiments were carried out by processing a sample with a 0.7 °C/s cooling rate to evaluate the formation of the microstructure. In direct thermal method experiment, a molten 7075 was poured into a cylindrical copper mould at different pouring temperatures of 680 °C and 660 °C meanwhile the holding time of 20 s, 40 s and 60 s before quenched into room temperature water. The sample processed by the cooling rate of 0.7 °C/s produced a large microstructure. The formation of a spheroidal microstructure was obtained with the combination of a suitable pouring temperature and holding time. The pouring temperature of 665 °C and the holding time of 60 s produced a finer and uniform microstructure that is suitable for semi-solid feedstock. Introduction Semi-solid metal (SSM) processing occurs between liquidus and solidus temperature range in which fluidity of molten metal changes greatly. Instead of a dendritic microstructure as per conventional processing, a spheroidal microstructure is formed by using SSM processing. The main advantage of SSM processing compared with other conventional processes is a low shrinkage porosity defect [1-3]. It occurs from smooth die filling action which eliminated air entrapment. This produced a high integrity product that has a fine and uniform microstructure. SSM processing also are able to produce a near-net-shape product. It is used to manufacture a variety of products with complex shape geometries. SSM processing involves with three important steps which consist of feedstock preparation, reheating or holding in a semi-solid condition and forming operation [4]. The feedstock billet which originally is in dendritic is transformed to a spheroidal microstructure by using an appropriate method and technique. The selection of the technique used is based on material type, weight and size. The spheroidal feedstock is then reheated or held in the semi-solid temperature range with a heating regime to ensure a homogenous temperature throughout the billets, by using a heating mechanism such as induction heating. Finally, the spheroidal feedstock is processed by using conventional process such as casting or forging termed thixocasting or thixoforging respectively, which has a heating condition in the range of semi-solid temperature. These processes use less force compared with excessive force in conventional process during the forming action which is affected by the existence of spheroidal microstructure within feedstock billet. There are several methods used recently to produce SSM feedstock [4]: methods consisting of liquid metal routes, solid state routes and combination methods. In the liquid metal routes, raw material is melted above its liquidus temperature and processed to create a spheroidal microstructure. Mechanical stirring for instance is the technique used to form a spheroidal microstructure which involves a shaft rotation within the liquid metal [5, 6]. Solid state route on the other hand is a process which produces a spheroidal microstructure without melting the raw material. Strain induced melt activation and recrystallization and partial melting is the technique which is grouped in this category

An innovative two-stage reheating process has been developed to improve the thixotropic behavior of semi-solid wrought aluminum alloy during thixoforming. The variation of the mi-crostructural evolution mechanisms with temperature and holding time during a traditional process and two-stage reheating process are presented in this paper. A preferred semi-solid microstructure with spherical-like grains surrounded by a uniform liquid film was obtained in the two-stage reheating process. The semi-solid microstructure obtained via this two-stage reheating process had a number of features beneficial for semi-solid metal processing, including smaller equivalent diameters, a higher degree of sphericity, a lower coarsening rate constant of solid grains and a reduced amount of entrapped liquid compared with that produced by the traditional reheating process. These results indicate that the two-stage reheating process is a promising method for manufacturing wrought aluminum alloy during thixoforming.

Ceramic particles typically do not have sufficiently high wettability by molten metal for effective bonding during metal matrix composite fabrication. In this study, a novel method has been used to overcome this drawback. Micron-sized SiC particles were coated by a cobalt metallic layer using an electroless deposition method. A layer of cobalt on the SiC particles was produced prior to incorporation in molten pure aluminum in order to improve the injected particle bonding with the matrix. For comparison, magnesium was added to the melt in separate experiments as a wetting agent to assess which method was more effective for particle incorporation. It was found that both of these methods were more effective as regard ceramic particulate incorporation compared with samples produced with as-received SiC particles injected into the pure aluminum matrix. SEM images indicated that cobalt coating of the particles was more effective than magnesium for incorporation of fine SiC particles (below 30 lm), while totally the incorporation percentage of the particles was higher for a sample in which Mg was added as a wetting agent. In addition, microhardness tests revealed that the cobalt coating leads to the fabrication of a harder composite due to increased amount of ceramic incorporation, ceramic-matrix bonding, and possibly also to formation of Al-Co intermetallic phases.

Stir casting is an economical process for the fabrication of aluminum matrix composites. There are many parameters in this process, which affect the final microstructure and mechanical properties of the composites. In this study, micron-sized SiC particles were used as reinforcement to fabricate Al-3 wt% SiC composites at two casting temperatures (680 and 850 °C) and stirring periods (2 and 6 min). Factors of reaction at matrix/ceramic interface, porosity, ceramic incorporation, and agglomeration of the particles were evaluated by scanning electron microscope (SEM) and high-resolution transition electron microscope (HRTEM) studies. From microstructural characterizations , it is concluded that the shorter stirring period is required for ceramic incorporation to achieve metal/ce-ramic bonding at the interface. The higher stirring temperature (850 °C) also leads to improved ceramic incorporation. In some cases, shrinkage porosity and intensive formation of Al_4C_3 at the metal/ceramic interface are also observed. Finally, the mechanical properties of the composites were evaluated, and their relation with the corresponding microstructure and processing parameters of the composites was discussed.

Three kinds of A356 based composites reinforced with 3 wt.% Al 2 O 3 (average particle size: 170 lm), 3 wt.% SiC (average particle size: 15 lm), and 3 wt.% of mixed Al 2 O 3 –SiC powders (a novel composite with equal weights of reinforcement) were fabricated in this study via a two-step approach. This first process step was semi-solid stir casting, which was followed by rolling as the second process step. Electroless deposition of a copper coating onto the reinforcement was used to improve the wettability of the ceramic particles by the molten A356 alloy. From microstructural characterization, it was found that coarse alumina particles were most effective as obstacles for grain growth during solidification. The rolling process broke the otherwise present fine silicon platelets, which were mostly present around the Al 2 O 3 particles. The rolling process was also found to cause fracture of silicon particles, improve the distribution of fine SiC particles, and eliminate porosity remaining after the first casting process step. Examination of the mechanical properties of the obtained composites revealed that samples which contained a bimodal ceramic reinforecment of fine SiC and coarse Al 2 O 3 particles had the highest strength and hardness.

Three kinds of A356 based composites reinforced with 3 wt.% Al 2 O 3 (average particle size: 170 lm), 3 wt.% SiC (average particle size: 15 lm), and 3 wt.% of mixed Al 2 O 3 –SiC powders (a novel composite with equal weights of reinforcement) were fabricated in this study via a two-step approach. This first process step was semi-solid stir casting, which was followed by rolling as the second process step. Electroless deposition of a copper coating onto the reinforcement was used to improve the wettability of the ceramic particles by the molten A356 alloy. From microstructural characterization, it was found that coarse alumina particles were most effective as obstacles for grain growth during solidification. The rolling process broke the otherwise present fine silicon platelets, which were mostly present around the Al 2 O 3 particles. The rolling process was also found to cause fracture of silicon particles, improve the distribution of fine SiC particles, and eliminate porosity remaining after the first casting process step. Examination of the mechanical properties of the obtained composites revealed that samples which contained a bimodal ceramic reinforecment of fine SiC and coarse Al 2 O 3 particles had the highest strength and hardness.

Ceramic particles typically do not have a sufficiently high wettability for incorporation into molten metal during aluminum matrix composite manufacturing. Metallic coatings on ceramic particles could improve their wettability by the molten aluminum and hence provide a better bonding between the reinforcement and matrix. In this study, micrometer-sized SiC particles were coated by copper, nickel, and cobalt metallic layers using electroless deposition method. These metallic layers were produced separately prior to ceramic incorporation into molten pure aluminum, in order to compare their effects on the microstructure and mechanical properties of the produced composites. The experimental results showed that copper was the most effective and nickel the least effective of these coating metals for incorporation of the SiC particles into the molten aluminum. It was additionally found that the composite, which contained the copper coated SiC particles , produced the highest microhardness and tensile strength, while that fabricated with the cobalt-coated SiC particles produced the lowest microhardness and tensile strength.

The paper presents an overview of measured mechanical properties of thixoformed aluminium 7075 feedstock produced by the direct thermal method (DTM). The DTM feedstock billets were processed with a pouring temperature of 685 degC and holing periods of 20, 40 and 60 s before being quenched and subsequently thixoformed. A conventionally cast feedstock billet was produced with a pouring temperature of 685 deg C and was allowed to solidify naturally without quenching. The feedstock billets were later formed by an injection test unit in the semi-solid state. Tensile testing was then conducted on the thixoformed feedstock billets. Tensile properties for 7075 DTM thixoformed feedstock billets were found to be significantly influenced by the thixoformed component density. Samples with longer holding times were found to have higher density and tensile strength.

Uniform dispersion of SiC nanoparticles with a high propensity to agglomerate within a thixoformed aluminium matrix was attained using a graphene encapsulating approach. The analytical model devised in this study has demonstrated the significant role of shear lag and thermally activated dislocation mechanisms in strengthening aluminium metal matrix composites due to the exceptional negative thermal expansion coefficient of graphene sheets. This, in turn, triggers the pinning capacity of nano-sized rod-liked aluminium carbide, prompting strong interface bonding for SiC nanoparticles with the matrix, thereby enhancing tensile elongation.

Cigarette smoking interferes with the metal homeostasis of the human body, which plays a crucial role for maintaining the health. A significant flux of heavy metals, among other toxins, reaches the lungs through smoking. In the present study, the relationship between toxic element (TE) exposure via cigarette smoking and rheumatoid arthritis incidence in population living in Dublin, Ireland, is investigated. The trace {zinc (Zn), copper (Cu), manganese (Mn), and selenium (Se)} and toxic elements arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) were determined in biological (scalp hair and blood) samples of patients diagnosed with rheumatoid arthritis, who are smokers living in Dublin, Ireland. These results were compared with age-and sex-matched healthy, nonsmoker controls. The different brands of cigarette (filler tobacco, filter, and ash) consumed by the studied population were also analyzed for As, Cd, Hg, and Pb. The concentrations of trace and TEs in biological samples and different components of cigarette were measured by inductively coupled plasma mass spectrophotometer after microwave-assisted acid digestion. The validity and accuracy of the methodology were checked using certified reference materials. The recovery of all the studied elements was found to be in the range of 96.4–99.8 % in certified reference materials. The filler tobacco of different branded cigarettes contains Hg, As, Cd, and Pb concentrations in the ranges of 9.55–12.4 ng, 0.432– 0.727 μg, 1.70–2.12 μg, and 0.378–1.16 μg/cigarette, respectively. The results of this study showed that the mean values of As, Cd, Hg, and Pb were significantly higher in scalp hair and blood samples of rheumatoid arthritis patients as compare to healthy controls, while Zn, Cu, Mn, and Se concentrations were found to be lower in rheumatoid arthritis patients, the difference was significant in the case of smoker patients (p<0.001). The levels of four toxic elements were 2–3-folds higher in scalp hair and blood samples of nonrheumatoid arthritis smoker subjects as compared to nonsmoker controls. The high exposure of toxic metals as a result of cigarette smoking may be synergistic with risk factors associated with rheumatoid arthritis.

Cigarette smoking interferes with the metal homeo-stasis of the human body, which plays a crucial role for maintaining the health. A significant flux of heavy metals, among other toxins, reaches the lungs through smoking. In the present study, the relationship between toxic element (TE) exposure via cigarette smoking and diabetic mellitus incidence in population living in Dublin, Ireland is investigated. The trace [zinc (Zn) and selenium (Se)] and toxic elements arsenic (As), aluminum (Al), cadmium (Cd), nickel (Ni), mercury (Hg), and lead (Pb) were determined in biological (scalp hair and blood) samples of patients diagnosed with diabetic mellitus, who are smokers living in Dublin, Ireland. These results were compared with age-and sex-matched healthy, nonsmokers controls. The different brands of cigarette (filler tobacco, filter, and ash) consumed by the studied population were also analyzed for As, Al, Cd, Ni, Hg, and Pb. The concentrations of TEs in biological samples and different components of cigarette were measured by inductively coupled plasma atomic emission spectrophotometer after microwave-assisted acid digestion. The validity and accuracy of the methodology were checked using certified reference materials (CRM). The recovery of all the studied elements was found to be in the range of 96.4–99.7 % in certified reference materials. The filler tobacco of different branded cigarettes contains Hg, As, Al, Cd, Ni, and Pb concentrations in the ranges of 9.55–12.4 ng/cig-arette, 0.432–0.727 μg/cigarette, 360–496 μg/cigarette, 1.70– 2.12 μg/cigarette, 0.715–1.52 μg/cigarette, and 0.378– 1.16 μg/cigarette, respectively. The results of this study showed that the mean values of Al, As, Cd, Hg, Ni, and Pb were significantly higher in scalp hair and blood samples of diabetic mellitus patients in relation to healthy controls, while the difference was significant in the case of smoker patients (p<0.001). The levels of all six toxic elements were twofolds to threefolds higher in scalp hair and blood samples of nondi-abetic mellitus smoker subjects as compared to nonsmoker controls. The high exposure of toxic metals as a result of cigarette smoking may be synergistic with risk factors associated with diabetic mellitus.

In this study, the hot extrusion process was applied to stir cast aluminum matrix–SiC composites in order to improve their microstructure and reduce cast part defects. SiC particles were ball milled with Cr, Cu, and Ti as three forms of carrier agents to improve SiC incorporation. Large brittle ceramic particles (average particle size: 80 μm) were fragmented during ball-milling to form nanoparticles in order to reduce the cost of composite manufacturing. The experimental results indicate that full conversion of coarse micron sized to nanoparticles, even after 36 h of ball milling, was not possible. Multi modal SiC particle size distributions which included SiC nanoparticles were produced after the milling process, leading to the incorporation of a size range of SiC particle sizes from about 50 nm to larger than 10 μm, into the molten A356 aluminum alloy. The particle size of the milled powders and the amount of released heat from the reaction between the carrier agent and molten aluminum are inferred as two crucial factors that affect the resultant part tensile properties and microhardness.