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The success of semi-solid metal forming is dependent on a globular solid grain formation within a liquid phase. This paper presents experimental works concerning semi-solid metal processing of aluminium 7075 feedstock billets which were produced by direct thermal method. The flowability of feedstock billets was evaluated by an injection test processing unit. The feedstock billets were heated to a temperature of 620 °C by using a box furnace before transferred into a forming die. The formed feedstock billet was removed from the forming die after it was cooled to ambient temperature. Several analyses were conducted on the formed feedstock billets including dimensional measurement and microstructure analysis. The results show that the feedstock billets which contained the highest amount of free secondary phase were most successfully formed. Microstructure analysis results also revealed the formation of more globular and larger α–Al solid grains in the same feedstock billets. In this experimental work, the feedstock billets with higher amount of secondary (liquid) phase had a significant effect on formability. It is concluded that in order to achieve successful formability of the direct thermal method feedstock billets, the billets need to a have higher secondary phase content. Thus, important preparation methods of feedstock billets were characterised in order to allow for SSM processing.

The chapter deals with vacuum casting, a process that refers to the casting and solidification of alloys within low pressure atmospheres which are often purged with inert gas. Pressures set at 0.1 Pa and below are commonly used with vacuum casting technology. This technology is employed where high cleanliness and purity are required during liquid metal processing. Vacuum casting helps to avoid contamination from reaction of the liquid metal with either the environment gases or crucible and mold container materials. In addition, recent advances in the high pressure die casting process, a process where a hydraulically powered plunger injects liquid metal alloys at high speed into a reusable steel mold are described for die castings produced from aluminum alloys, magnesium alloys, and zinc alloys. A review follows of the fabrication of composites by casting techniques, a promising route for manufacturing near net shape parts at relatively low cost and looks at several liquid fabrication techniques available to manufacture composite materials, classified according to the type of reinforcement. Fabrication techniques can vary considerably and include stir casting, liquid metal infiltration, squeeze casting, spray co-deposition, and compocasting. The chapter concludes with a review of both single roller and twin roller roll casting, processes that can cast strip directly from the melt in a one step, promising savings in effort and energy.

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.

BACKGROUND The incidence of Rheumatoid Arthritis (RA) has increased among people who smoke tobacco. In the present study, the association between toxic metals exposure via cigarette smoking and rheumatoid arthritis incidence in the population living in Dublin, Ireland, is investigated. The different brands of cigarettes (filler tobacco, filter and ash) consumed by the population studied were analysed for Cd, Ni, and Pb. METHODS The concentrations of toxic elements in biological samples and different components of cigarettes 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. RESULTS The filler tobacco of different branded cigarettes contain Cd, Ni, and Pb concentrations in the ranges of 1.73-2.02, 0.715-1.52, and 0.378-1.16 μg/cigarette, respectively. The results of this study showed that the mean values of cadmium nickel, and lead were significantly higher in scalp hair and blood samples of rheumatoid arthritis patients when related to healthy controls, while the difference was significant in the case of smoker patients (p < 0.001). The levels of all three toxic metals were 2- to 3-fold higher in scalp hair and blood samples of non arthritis smoker subjects as compared to nonsmoker controls. CONCLUSIONS The high exposure of toxic metals as a result of cigarette smoking may be synergistic with risk factors associated with rheumatoid arthritis.

The early development of metallic glasses was achieved through the rapid cooling of micrometer-thick thin ribbons via planar flow casting. These early developments were made with alloy compositions that could not be cast into thicker sections while maintaining their amorphous nature. This limitation was due to the relatively slower cooling rates resulting from the larger volume and associated energy contained within these larger volume sections. The problem of casting larger sections with amorphous structures was overcome primarily by the discovery of new alloy compositions that do not necessitate as high a cooling rate, as well as by designing processes that allow for more rapid cooling for larger volumes. Bulk metallic glass (BMG) processing was established with modified centrifugal casting, die casting, and splat casting techniques that incorporate high-speed injection and suction mechanisms, as well as high thermal conductivity copper molds. Although many casting techniques have been reported, the main goal has been to improve the glass-forming ability (GFA) and thus achieve larger section thicknesses that remain amorphous within the BMG alloy component. Most investigations on the development of BMG alloys have examined the effects of thermal field and alloy composition on the properties of BMG alloys. In particular, the effects of multicomponent BMG alloy systems containing rare earth, transition metals, and metalloids elements have been investigated.

The success of any implant, dental or orthopaedic, is driven by the interaction of implant material with the surrounding tissue. In this context, the nature of the implant surface plays a direct role in determining the long term stability as physico-chemical properties of the surface affect cellular attachment, expression of proteins, and finally osseointegration. Thus to enhance the degree of integration of the implant into the host tissue, various surface modification techniques are employed. In this work, laser surface melting of titanium alloy Ti–6Al–4V was carried out using a CO2 laser with an argon gas atmosphere. Investigations were carried out to study the influence of laser surface modification on the biocompatibility of Ti–6Al–4V alloy implant material. Surface roughness, microhardness, and phase development were recorded. Initial knowledge of these effects on biocompatibility was gained from examination of the response of fibroblast cell lines, which was followed by examination of the response of osteoblast cell lines which is relevant to the applications of this material in bone repair. Biocompatibility with these cell lines was analysed via Resazurin cell viability assay, DNA cell attachment assay, and alamarBlue metabolic activity assay. Laser treated surfaces were found to preferentially promote cell attachment, higher levels of proliferation, and enhanced bioactivity when compared to untreated control samples. These results demonstrate the tremendous potential of this laser surface melting treatment to significantly improve the biocompatibility of titanium implants in vivo. yes

In this work, various three-dimensional (3D) scaffolds were produced via micro-stereolithography (µ-SLA) and 3D printing (3DP) techniques. This work demonstrates the advantages and disadvantages of these two different rapid prototyping methods for production of bone scaffolds. Compared to 3DP, SLA provides for smaller feature production with better dimensional resolution and accuracy. The permeability of these structures was evaluated experimentally and via numerical simulation utilizing a newly derived Kozeny-Carman based equation for intrinsic permeability. Both experimental and simulation studies took account of porosity percentage, pore size, and pore geometry. Porosity content was varied from 30% to 70%, pore size from 0.34 mm to 3 mm, and pore geometries of cubic and hexagonal closed packed were examined. Two different fluid viscosity levels of 1 mPa · s and 3.6 mPa · s were used. The experimental and theoretical results indicated that permeability increased when larger pore size, increased fluid viscosity, and higher percentage porosity were utilized, with highest to lowest degree of significance following the same order. Higher viscosity was found to result in permeabilities 2.2 to 3.3 times higher than for water. This latter result was found to be independent of pore morphology type. As well as demonstrating method for determining design parameters most beneficial for scaffold structure design, the results also illustrate how the variations in patient's blood viscosity can be extremely important in allowing for permeability through the bone and scaffold structures.

A new characterisation method, based on the utilisation of focussed ion beam-scanning electron microscopy (FIB-SEM), has been employed for the evaluation of morphological parameters in porous monolithic materials. Sample FIB serial sectioning, SEM imaging and image processing techniques were used to extract the pore boundaries and reconstruct the 3D porous structure of carbon and silica-based monoliths. Since silica is a non-conducting material, a commercial silica monolith modified with activated carbon was employed instead to minimise the charge build-up during FIB sectioning. This work therefore presents a novel methodology that can be successfully employed for 3D reconstruction of porous monolithic materials which are or can be made conductive through surface or bulk modification. Furthermore, the 3D reconstructions were used for calculation of the monolith macroporosity, which was in good agreement with the porosity values obtained by mercury intrusion porosimetry (MIP).

The dynamic batch adsorption of methylene blue (MB), a widely used and toxic dye, onto nanocrystalline cellulose (NCC) and crushed powder of carbon monolith (CM) was investigated using the pseudo-first- and -second-order kinetics. CM outperformed NCC with a maximum capacity of 127 mg/g compared to 101 mg/g for NCC. The Langmuir isotherm model was applicable for describing the binding data for MB on CM and NCC, indicating the homogeneous surface of these two materials. The Gibbs free energy of -15.22 kJ/mol estimated for CM unravelled the spontaneous nature of this adsorbent for MB, appreciably faster than the use of NCC (-4.47 kJ/mol). Both pH and temperature exhibited only a modest effect on the adsorption of MB onto CM. The desorption of MB from CM using acetonitrile was very effective with more than 94 % of MB desorbed from CM within 10 min to allow the reusability of this porous carbon material. In contrast, acetonitrile was less effective than ethanol in desorbing MB from NCC. The two solvents were incapable of completely desorbing MB on commercial granular coal-derived activated carbon.

Background: 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 hypertension incidence in population living in Dublin, Ireland is investigated. Methods: The different brands of cigarette (filler tobacco, filter and ash) consumed by the studied population were analyzed for cadmium (Cd), nickel (Ni), and lead (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. Results: The filler tobacco of different branded cigarettes contains Cd, Ni and Pb concentrations in the ranges of 1.73-2.02, 0.715-1.52 and 0378-1.16 pg/cigarette, respectively. The results of this study showed that the mean values of Cd, Ni and Pb were significantly higher in scalp hair and blood samples of hypertensive patients in relation to healthy controls, while the difference was significant in the case of smoker patients (p < 0.001). The levels of all the three TEs were 2-3 folds higher in scalp hair and blood samples of non-hypertensive smoker subjects as compared to nonsmoker controls. Conclusion: The high exposure of toxic metals as a result of cigarette smoking may be synergistic with risk factors associated with hypertension.

Polymeric biomaterials are being widely used for the treatment of various traumata, diseases and defects in human beings due to ease in their synthesis. As biomaterials have direct interaction with the extracellular environment in the biological world, biocompatibility is a topic of great significance. The introduction or enhancement of biocompatibility in certain polymers is still a challenge to overcome. Polymer biocompatibility can be controlled by surface modification. Various physical and chemical methods (e.g., chemical and plasma treatment, ion implantation, and ultraviolet irradiation etc.) are in use or being developed for the modification of polymer surfaces. However an important limitation in their employment is the alteration of bulk material. Different surface and bulk properties of biomaterials are often desirable for biomedical applications. Because extreme ultraviolet (EUV) radiation penetration is quite limited even in low density mediums, it could be possible to use it for surface modification without influencing the bulk material. This article reviews the degree of biocompatibility of different polymeric biomaterials being currently employed in various biomedical applications, the surface properties required to be modified for biocompatibility control, plasma and laser ablation based surface modification techniques, and research studies indicating possible use of EUV for enhancing biocompatibility.

In order to increase the efficiency of solar cell modules it is necessary to make the optimum use of light incident upon them. Much research has been done on improving light absorption through front surface texturisation and light trapping schemes. Laser light is commonly used in industry for various applications including marking and texturisation. By controlling laser parameters, it is possible to tailor macro and micro structures in most materials. The CO2 laser used in this investigation emits radiation at 10.6 μm with the ability to pulse in the micro-second range. The laser was used to ablate grooved textures in the fused quartz material, used in this study as the light trapping medium, following which an analysis of the effects of the laser parameters on the texture geometry and surface morphology was performed through a combination of cross sectioning and scanning electron microscopy. Transmission through the textured glass was improved for most samples after acid etching. The light trapping effects of the best performing textures were analysed by investigating the effects on a silicon solar cell’s performance at varying angles of incidence. Results indicated a significant increase in light trapping when light was incident at acute angles. For an angle of incidence of 10∘ a relative increase in efficiency of up to 51 % was observed.

Static and dynamic models of the characteristic responses of sliotar cores made of both cork and polyurethane were studied in this work in order to understand their constitutive behaviour. Data from quasi-static tests at 10 mm/s and from dynamic impacts at speeds from 5 to 25 m/s were used to develop and evaluate the models. The quasi-static response was described well by Hertzian theory. A non-linear HunteCrossley model and a modified linear KelvineVoigt model were used to predict the dynamic response with set mass and shape coefficient parameters. The HunteCrossley model predicted well both the maximum force and maximum deflection for each ball type. The HunteCrossley model generally captured the experimental contact times well with a mean difference between experimental and model contact times of 8.3%. The mean difference between the KelvineVoigt model and experimental contact times was 7.6%, while the corresponding mean difference for the coefficient of restitution was 13.1%. Overall, the modified KelvineVoigt model predicted the parameters of contact time and coefficient of restitution well. Contact time and coefficient of restitution prediction in this linear model were not particularly sensitive to the strain rate.

Capillary electrophoresis (CE) has been used for over 30 years as an efficient separation technique [1]. These separations are typically preformed using capillaries with internal diameter ranging from 2 μm to 200μm and as the diameter increases above 100μm, a reduction in separation performance is observed [2]. One of the main factors limiting the overall performance of CE separations is Joule heating associated with the passing of the electric current through resistive medium. The high surface-to-volume ratio in a smaller capillary diameter allows for efficient heat dissipation which is beneficial for compound separation, however, simultaneously this has a negative impact on the detection performance due to the corresponding reduction in analyte volume available for detection [3]. Historically when capillaries were first used for CE, they were coated with polyimide and presented excellent robustness but posed problems with optical detection as polyimide is highly absorbing below 550nm preventing optical detection in that spectral range. Such capillaries were striped of the coating to enable the optical detection in UV and low wavelength visible range. However, capillaries striped of their coating are brittle and can easily be damaged making usage often impractical. The introduction of the polytetrafluoroethylene (PTFE) coated capillaries allowed for optical detection within the UV range as well as across the entire visible spectrum. Although the PTFE coated capillaries are not as durable as the polyimide coated capillaries, they are significantly more robust than coatless ones and allow for easier deployment during typical daily laboratory routine. Absorbance photometry is a detection technique used to determine the concentration of target species in a liquid sample based on interaction between the probe light and species [4]. Typically it is a measurement of the light intensity with and without a sample placed in the light path. A scheme of light intensity measurement with the sample located for detection is presented in Figure 1. The sample transmittance, T, is defined as the ratio of the initial light intensity, I 0 , to the recorded light intensity, I 1 (Eq. 1). I 0 should be measured with the sample holding cuvette empty. This allows for reflections and potential absorption by the cuvette material to be taken into account during sample measurement. Sample absorbance, A, is measured as the negative log of the transmittance (Eq. 2). The cuvette length 𝑙 is known, as well as species molar absorptivity coefficient α, which is a specific characteristic of every species. Light attenuation along the light path is governed by Beer-Lambert’s law where c is molar concentration (Eq. 3) [5]. The method of calculating the actual optical path length is presented elsewhere [6]. Despite excellent performance in analyte separation, CE techniques still constitute a minority of the commercial applications due to detection limitations imposed by popular absorbance photometric detectors. Various developments in CE have occurred such as the development of UV-transparent capillaries which facilitated CE by making it possible to employ the commercially available detectors. In the past different approaches have also been employed to alter the geometry of the detection system in order to improve the detection performance for CE. These include the application of rectangular capillaries to reduce refraction effects on the cylindrical boundaries [2], multi-reflection cells for increased signal intensity [7], and development of Z-shaped flow cells with increased optical pathlength for analyte detection [8]. Some detectors were built employing these methods, but to date the majority of the commercially available absorbance based detectors work on the basis of a single passage of light through the sample contained in a capillary. To gain a better understanding of light propagation through capillaries and how to improve detection levels, the modelling of the light propagation through capillaries has been previously undertaken. Much of this work was limited to two-dimensional projections and two-layer models (no coating present) taking into account capillary material and inner cavity [9]. Previous numerical simulations of light propagation through capillaries have been reported as a tool for flow-cell design and have been limited to prediction of light path for these specific cases only [10]. The numerical problem of ray-tracing through a capillary is an excellent example where advantage can be taken of the ability to perform numerous calculations quickly on a computer to allow for ray paths, ray path overlaps, and resultant light intensities to be calculated. This book chapter presents a theoretical study on the light propagation through coated capillaries, focusing on PTFE-coated capillaries. These models can be used to increase the performance of absorbance photometric detection and for associated photochemical applications.

In this study, the effects of laser parameters on the properties of glazed die steel were investigated. A Rofin DC-015 diffusion-cooled CO2 slab laser with 10.6 µm wavelength was used. Die steel sample surfaces were prepared with a 3 µm roughness and chemically treated to improve CO2 laser wavelength absorbance. One set of processing parameters were processed through the thermal simulation program and correlated with physical results determined from actual test samples. Set processing parameters were 1138 W peak power, 2900 Hz PRF, 24% duty cycle and 261 mm/s traverse speed. Scanning Electron Microscopy (SEM) micrographs and micro-hardness properties of the affected surface were measured. An analytical mathematical model of the heat field generated in the laser glazing process was used to predict the nominal temperature distribution in the surface and dimensions of melt pool. A thermal model using point source surface energy inputs was used to predict the thermal profiles in the die steel. This allowed estimation of the depths of microstructurally altered regions. For higher energy absorbance, the depth of the glazed surface increased from 20 μm to 40 μm. At high nominal heating to cooling rate ratios, high micro-hardness values were recorded.

This paper presents a fast fabrication process of microfluidic channels with quartz substrates. Microchannels were ablated on the surface of quartz samples with a CO2laser. Double sided Pressure Sensitive Adhesive (PSA) was applied to bond the samples with scribed microchannels to flat glass sheets. Dimensions of the fabricated channels were characterised with optical microscopy and laser profilometry. The recorded data was modelled with a BoxBehnken experiment design using Response Surface Methodology. Characterisation included also the measurement of optical transmission through the processed glass and measurement of flow rate through the fabricated channels. With an average width of 165 µm and depth of 280µm, fabricated channels had appropriate dimensions for a range of microfluidic applications. A significant width of the laser processed channels provided 100% transmission for a wide range of the optical spectrum. These fabricated channels were also shown to not significantly retard the fluid flow rate thus making these channels applicable for integration into numerous detection systems for chemical separation applications.

Aims: Studies on soil mechanics have established that when vibration is applied to an aggregate, it results in more efficient alignment of particles and reduces the energy required to impact the aggregate. Our aim was to develop a method of applying vibration to the bone impaction process and assess its impact on the mechanical properties of the impacted graft. Methods: Phase 1. Eighty bovine femoral heads were milled using the Noviomagus bone mill. The graft was then washed using a pulsed lavage normal saline system over a sieve tower. A vibration impaction device was developed which housed two 15V DC motors with eccentric weights attached inside a metal cylinder. A weight was dropped onto this from a set height 72 times so as to replicate the bone impaction process. A range of frequencies of vibration were tested, as measured using an accelerometer housed in the vibration chamber. Each shear test was then repeated at four different normal loads so as to generate a family of stress-strain curves. The Mohr-Coulomb failure envelope from which the shear strength and interlocking values are derived was plotted for each test. Phase 2. Experiments were repeated with the addition of blood so as to replicate a saturated environment as is encountered during operative conditions. Results Phase 1. Graft impacted with the addition of vibration at all frequencies of vibration showed improved shear strength when compared to impaction without vibration. Vibration at sixty Hertz was displayed the largest effect and was found to be significant. 3 Phase 2. Graft impacted with the addition of vibration in a saturated aggregate displayed lower shear strengths for all normal compressive loads than that of impaction without vibration. Conclusions Civil engineering principles hold true for the impaction bone grafting procedure. In a dry aggregate the addition of vibration may be beneficial to the mechanical properties of the impacted graft. In our system the optimal frequency of vibration was 60 Hz. Under saturated conditions the addition of vibration is detrimental the shear strength of the aggregate. This may be explained by the process of liquefaction.

In this work the affects of laser characteristics on surface morphology, microstructure, microhardness and wear rates of high velocity oxygen fuel (HVOF) WC–CoCr coatings were investigated. Continuous and pulsed laser treatments were applied on the HVOF coatings using a CO2 laser of 10.6 μm wavelength. Continuous laser treatment significantly improved homogeneity of the coatings. Pulsed laser treatment produced significantly higher discontinuities compared to continuous mode. Microhardness increased by 45% for continuous mode laser modified WC-CoCr coatings. However, wear resistance deteriorated, with a notable 40% increase in wear rate. The variations in coating properties were attributed to the re-melting and rapid quenching of the CoCr bonding matrix allowing for WC redistribution.

This paper presents a laser surface modification process of AISI H13 tool steel using three sizes of laser spot with an aim to achieve reduced grain size and surface roughness. A Rofin DC'015 diffusion'cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). Metallographic study and image analysis were done to measure the grain size and the modified surface roughness was measured using two'dimensional surface profilometer. From metallographic study, the smallest grain sizes measured by laser modified surface were between 0.51 3m and 2.54 3m. The minimum surface roughness, Ra, recorded was 3.0 3m. This surface roughness of the modified die steel is similar to the surface quality of cast products. The grain size correlation with hardness followed the findings correlate with Hall'Petch relationship. The potential found for increase in surface hardness represents an important method to sustain tooling life.

The abnormal metabolism of metal ions plays an important role in health and disease conditions, and studies about them have been attracting significant interest. The aim of our study was to assess the heavy metals (cadmium (Cd), nickel (Ni), lead (Pb), and zinc (Zn)) in scalp hair samples of 50 Irish and 78 Pakistani hypertensive patients of an urban population together with 50 Irish and 96 Pakistani non-hypertensive male subjects in the age group of 30–50 years. The concentrations of trace and toxic elements were measured by inductively coupled plasma–atomic emission spectrophotometer and atomic absorption spectrophotometer before microwave-assisted acid digestion. The validity and accuracy of the methodology were checked using certified reference materials, and by the conventional wet acid digestion method on the same certified reference materials and on real samples. The recovery of all the studied elements was found to be in the range of 97.5–99.7% in certified reference material. The results of this study showed that the mean values of cadmium, nickel, and lead were significantly higher in scalp hair samples of both Pakistani and Irish hypertensive patients than in referents (p

The incidence of hypertension has been associated to cigarette smoking and consumption of alcohol. In the present study, trace and toxic elements were determined in scalp hair of patients diagnosed with hypertension who are smokers and habitual alcohol drinkers living in Dublin, Ireland. These results were compared with age- and sex-matched healthy, nonsmokers, nondrinking controls. The concentrations of trace and toxic elements 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 material (NCS ZC 81002b) and by the conventional wet acid digestion method on the same certified reference material and on real samples. The recovery of all the studied elements was found to be in the range of 97.5%–99.7% in certified reference material. The results of this study showed that the mean values of cadmium, copper, iron, nickel and lead were significantly higher in scalp hair samples of both smoker and nonsmoker hypertensive patients than referents (P

This paper presents the utilisation of Response Surface Methodology (RSM) as the prediction tool for the laser micro-machining process. Laser internal microchannels machined using pulsed Nd:YVO4 laser in polycarbonate were investigated. The experiments were carried out according to 33 factorial Design of Experiment (DoE). In this work the three input process set as control parameters were laser power, P; pulse repetition frequency, PRF; and sample translation speed, U. Measured responses were the channel width and the micro-machining operating cost per metre of produced microchannels. The responses were sufficiently predicted within the set micro-machining parameters limits. Two factorial interaction (2FI) and quadratic polynomial regression equations for both responses were constructed. It is proposed that the developed prediction equations can be used to find locally optimal micro-machining process parameters under experimental and operational conditions.

This paper presents the thermal fatigue resistance of laser treated steels. The C40 and AISI H13 steels were machined into a geometry which allowed thermal gradients on the inner and outer surface during testing. A CO2 laser system was used with a focused spot size of 0.09 mm on the sample surface. The laser peak power and pulse repetition frequency (PRF) range were set to 760 and 1515 W, and 2900 to 3500 Hz respectively. The thermal fatigue machine used consists of Nabertherm model cylindrical high temperature furnace with digital control panel, controlled temperature quenching system, and pneumatics control sample movement mechanism. The thermal fatigue test involved immersion of samples into molten aluminium, and quenched in ionised water emulsion at 17 °C temperature. The quenching system equipped with thermocouple to control the water temperature. Testing was done at a total of 1,750 number of cycles. Internal surface cooling was controlled by water inlet and outlet tubes. Samples were cleaned using NaOH solution after thermal fatigue testing to remove oxides on the surface. The solution temperature and magnetic stirrer speed were set to 100 °C and 4.5 rpm respectively. Samples were characterised using scanning electron microscope (SEM), energy discharge x-ray spectroscopy (EDXS) and 2D stylus profilometer. Presence of different phases on the sample surface were analysed from back-scattered detector micrographs. Heat checks were observed on laser glazed surface at several regions. Carbides and oxides elements were detected on the sample surface after the thermal fatigue test. The relationship between surface roughness of laser treated surface and thermal fatigue behaviour was investigated.

In this work the affects of laser characteristics on microstructure and microhardness of high velocity oxygen fuel sprayed (HVOF) WC–CoCr coatings were investigated. The coating was deposited with a Sulzer Metco WokaJet™-400 kerosene fuel and the laser surface treatments were applied using CO2 laser with 10.6 μm wavelength. Large variations in surface properties were produced from variation in the laser processing parameters. In total, four levels of peak power (100, 200, 300 and 350 W), four levels of spot diameter (0.2, 0.4, 0.6 and 1 mm) and three levels of pulse repetition frequency (PRF) were investigated. An initial set of tests were followed by a more detailed 33 factorial design of experiments. Pulse repetition frequency and duty cycle were set in order to maintain the same overlap in the x and y directions for the raster scanned sample spot impact dimensions. Overlaps of 30% were used in the initial tests and 10% in the more detailed trials. The results have shown that care must be taken to keep the irradiance at a relatively low level compared to uncoated surfaces. High irradiance can in this case result in rough and porous surfaces. Lower levels of irradiance are shown to provide more uniform microstructures, reduced porosity and increased microhardness.

Microfluidics is a technology where application span the biomedical field and beyond. Single cell analysis, tissue engineering, capillary electrophoresis, cancer detection, and immunoassays are just some of the applications within the medical field where microfluidics have excelled. The development of microfluidic technology has lead to novel research into fuel cells, ink jet printing, microreactors and electronic component cooling areas as diverse as food, pharmaceutics, cosmetics, medicine and biotechnology have benefited from these developments. Since laminar flow is prevailing at most flow regimes in the micro-scale, thorough mixing is a challenge within microfluidics. Therefore, understanding the flow fields on the micro-scale is key to the development of methods for successfully microfluidic mixing applications.

The geometry of bone scaffolds plays a crucial role in bone tissue regeneration. This architecture, especially pore size and shape, determines the mechanical strength of the scaffold. A number of previous workers have indicated the parameters which are believed to be the main stimulus in the adaptive bone remodelling process. An ideal bone manufacturing system would deliver bone morphogenetic proteins (BMP) and provide adequate mechanical properties. The aim of this study was to design a highly osteoconductive and mechanically strong bone regeneration scaffold which can be successfully manufactured. Three porous architectures of scaffold were designed using Solid EdgeTM 3D solid modelling software. The equivalent trabecular structure model consisted of repeatable unit cells arranged in layers to fill the chosen scaffold volume. The three different unit cell structures examined include cubic, triangular, and hexagonal polyhedral. Designed scaffold’s pores were varied in this study to 120, 340 and 600µm. This range was selected to meet one of the requirements of the scaffold design – the macropores must be at least 100µm in diameter, so the cells can penetrate and proliferate within the structure. The strengths of each scaffold were determined using ANSYSTM finite element software. Trabecular scaffold designs were analysed independently and in connection with simulated cortical bone in order to investigate their stress-strain response. As well as providing useful information on strengths developed from these topologies, the models developed indicated geometric constraints in order to tailor scaffolds to specific patient needs.

Due to limited lifetime for biomedical implants, material engineers have strived to improve the surface properties of existing biomaterials. Widely used methods of surface modification include film deposition such as physical vapour deposition (PVD), chemical vapour deposition (CVD) and diamond like carbon coating (DLC). Internal stresses make it difficult to bond such coatings to the substrates thus weakening the structure and limiting the life of implants. Laser glazing can achieve an amorphous layer on a component surface. Advantages of an amorphous layer include increased hardness, wear and corrosion resistance. These advantages arise from the elimination of crystalline anisotropy and inter-crystalline defects. These latter crystalline features provide the dislocation nucleation sites and shorter diffusion paths for enhanced oxidation and corrosion degradation. The current study introduced a surface modification method of laser glazing of biomedical AISI 316L austenitic stainless steel to improve tribological properties. This stainless steel is commonly used in orthopaedics owing to its high corrosion resistance. However, due to its low hardness (250 HV), its tribological properties are poor. A pulsed CO2 laser was used with peak power and pulse width being varied between 0.4 to 1.5kW and 30µs to 120 µs respectively. The laser beam spot size, sample speed, percentage overlap and pulse repetition frequency were kept at 90µm, 570 rpm, 50% and 5 kHz respectively. These parameters were optimised from literature parameters using design of experiments software. This paper presents and discusses the effects of these processing parameters on the morphology of the glazed zone. Microstructure and chemical composition were determined by scanning electron microscopy (SEM), optical microscopy, and electron dispersive spectroscopy (EDS). X-ray diffraction (XRD) was used to analyse the degree of crystallinity in the glazed zone. A stylus profilometer and micro-hardness tester were also used to investigate the effects of glazing on roughness and hardness of the modified stainless steel layer. A strong correlation between irradiance, depth of processing and roughness of processed material was found. Increased depth of altered microstructure and increased roughness were linked to higher levels of irradiance.

This paper presents laser surface modification work performed to improve the lifetime of die materials. Die material AISI H13, with typical hardness in the range of 42 to 48 HRC, offers high wear and corrosion resistance. However the cyclic high temperature conditions along with exposure to high viscosity molten metal in semi-solid forming cause the die to wear and crack with resultant shortened die lifetime. In this study, the thermal stability of die material at elevated temperature was investigated through micro-hardness testing and a metallographic study. AISI H13 samples were laser glazed using CO2 continuous wave mode laser with 10.6 µm wavelength. Samples were attached to a specially designed rotating chuck to enable it to be rotated at speeds up to 1500 rpm and allow flat surface glazing to take place. The micro- hardness was measured for as-glazed samples and annealed samples which were held at temperatures ranging from 550oC to 800oC with 50oC intervals. The metallographic study conducted examined the formation of three zones at different depths which were the glazed zone, the heat affected zone and the substrate. As a result of rapid heating and cooling from the laser glazing process, a metallic glass layer was developed which exhibited an average micro-hardness of 900 HV when exposed to 3.34E+10 W/m2 laser irradiance within a range of 0.0011 to 0.0018 s exposure time. Crystallization in glazed zone increased as the annealing temperature increased. As the annealing temperature reached above approximately 600oC, the micro-hardness decreased to approximately 600 HV (equivalent to approx. 54 HRC) due to local crystallization. These findings show potential direct application of glazed dies for non-ferrous semi-solid forming and the requirement for thermal barrier protection for application at higher temperatures.

Although from an athletic performance perspective it may be beneficial to undertake drop jump training when fatigued (principle of "specificity" of training), such endur-ance fatigue may expose the body to a greater risk of injury if it causes an increase in peak impact accelerations. This study aimed to determine if endurance fatigue resulted in an increase in tibial peak impact acceleration and an associated change in knee kinematics when completing plyometric drop jumps. Fifteen females performed drop jumps from 3 heights (15, 30, and 45 cm) when fatigued and nonfatigued. Treadmill running was used to induce endurance fatigue. The following variables were assessed: tibial peak impact acceleration, knee angle at initial ground contact, maximum angle of flexion, range of flexion, and peak knee angular velocity. Fatigue resulted in significantly greater (p < 0.05) tibial peak impact acceleration and knee flexion peak angular velocity in drop jumps from 15 and 30 cm, but not from 45 cm. Fatigue had no effect on any of the knee angles assessed. The neuromuscular system was affected negatively by endurance fatigue at 15 and 30 cm, indicating that coaches should be aware of a potential increased risk of injury in performing drop jumps when fatigued. Because from the greater drop height of 45 cm the neuromuscular system had a reduced capacity to attenuate the impact accelerations per se, whether nonfatigued or fatigued, this would suggest that this height may have been too great for the athletes examined.

Journal article Selective laser sintering (SLS) enables the fabrication of complex geometries with the intricate and controllable internal architecture required in the field of tissue engineering. In this study hydroxyapatite and poly-epsilon-caprolactone, considered suitable for hard tissue engineering purposes, were used in a weight ratio of 30:70. The quality of the fabricated parts is influenced by various process parameters. Among them Four parameters, namely laser fill power, outline laser power, scan spacing and part orientation, were identified as important. These parameters were investigated according to a central composite design and a model of the effects of these parameters on the accuracy and mechanical properties of the fabricated parts was developed. The dimensions of the fabricated parts were strongly dependent on the manufacturing direction and scan spacing. Repeatability analysis shows that the fabricated features can be well reproduced. However, there were deviations from the nominal dimensions, with the features being larger than those designed. The compressive modulus and yield strength of the fabricated microstructures with a designed relative density of 0.33 varied between 0.6 and 2.3 and 0.1 and 0.6 MPa, respectively. The mechanical behavior was strongly dependent on the manufacturing direction. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. peer-reviewed

Pure cobalt ferrite ceramic powder was prepared using standard solid-state ceramic processing. Uniaxially pressed pure cobalt ferrite discs, sintered under isothermal ramp rate and single dwell time conditions, yielded a maximum theoretical density (%Dth) of

There are many factors which influence the incorporation of particulate in metal matrix composites (MMCs). This paper presents work which examines the effect of viscosity during Al–SiC MMC production. Processing periods (up to 65 min), stirring speeds (50–500 rpm), and re-inforcement sizes (13–100 μm) for two different viscosity levels (1 and 300 mPa s) were investigated. Computer simulations, room temperature analogue fluid simulations, and MMC castings were performed. Volume fraction results of SiC at different locations within the fluids were assessed by each of these methods and compared. From these tests, a stirring speed of 200 rpm for the lower viscosity fluid and 300 rpm for the higher viscosity fluid were found to be best in order to produce uniform distributions of SiC. In order to obtain a uniform re-inforcement distribution in the lower viscosity system, stirring periods were found to range from 14 to 170 s and for the higher viscosity system from 540 to more than 3920 s. Fully uniform suspensions remained for just a couple of seconds in the lower viscosity system compared to about an hour for the higher viscosity system. The modelling approach chosen was found to be useful in predicting settling behaviour in the semi-solid metal.

Examples of sheet materials for which optical inspection systems have been reported include paper webs, textile fabric, glass material, hot slabs and cold-rolled metal strip. These inspection systems are essential tools for the implementation of modem statistical process control procedures. Interferometric methods, despite their high accuracy, are mostly too sensitive to be practical for application in production. Laser triangulation is frequently the best solution for these types of applications because it combines the advantage of noncontact inspection with the ability to measure with sub-micrometer resolution. A fibre optic intensity-based sensor however requires a much simpler optical system, and therefore, can be made very small. These systems also are less costly and can be used to detect surface roughness. Such a laser scanner consists of two parts: an illumination part and an imaging part. The intensity of the detected light in the imagining part depends upon how far the reflecting surface is from the fibre optic end(s). Light scattering from a test surface may be a changed by different microstructures encountered. However, a sudden change in the light intensity would occur when the incident light beam encounters a defect.

Introduction There is a paucity of information about the light and heat output of laryngoscopy equipment. We became concerned about the potential of a laryngoscope blade burn following an episode during intubation We mounted an in-vitro study of larynoscopes to determine the temperatures reached during clinical use. Methods The temperature of the incandescent light bulb from ten different laryngoscopes was measured using a Real Time controller from National Instruments for data logging into a PC. A second set of tests were performed using two fibre optic laryngoscope head designs. The temperature was measured every half a second for ten minute duration from the point in time at which the light was turned on in all devices. The temperature fall times from closing and simultaneous turning off of the laryngoscope light were also recorded. Results Peak temperature was found to be consistently above 50 °C in four different brands of light bulb protruding laryngoscope heads. On closing the laryngoscope temperatures were all below 30° at a one minute interval. In comparison, the fibre optic laryngoscope heads did not reach temperatures higher than 27.5°C. Discussion The findings from our study indicate that within 30 seconds all ten laryngoscopes, with light-bulb sources, had gained significant heat to cause thermal injury to neonatal skin. LED laryngoscopes did not. Conclusions We recommend that the laryngoscope blade is not left open prior to intubation and that it is closed between intubation attempts.

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A technique for the in-process measurement of polymer stationary phase growth inside fused silica capillaries during the fabrication of monolithic porous layer open tubular (monoPLOT) columns is presented. In this work, capacitively coupled contactless conductivity detection (C4D) was applied as an online measurement tool for porous polymer layer growth within fused silica capillaries. The relationship between effective capillary diameter and C4D response was investigated for two polymers, butyl methacrylate–ethylene dimethacrylate (BuMA–EDMA) and polystyrene–divinylbenzene (PS–DVB) over a range of capillary diameters and layer thicknesses. The described technique can be used with both thermal and photo-initiated approaches for monoPLOT fabrication and provides an accurate, real-time measurement of the porous layer growth within the capillary, which should vastly improve column-to-column reproducibility. The technique was shown to be very precise, with a measured %RSD < 10%.

Miniaturized, portable instrumentation has been gaining popularity in all areas of analytical chemistry. Capillary electrophoresis (CE), due to its main strengths of high separation efficiency, relatively short analysis time and low consumption of chemicals, is a particularly suitable technique for use in portable analytical instrumentation. In line with the general trend in miniaturization in chemistry utilizing microfluidic chips, the main thrust of portable CE (P—CE) systems development is towards chip-based miniaturized CE. Despite this, capillary-based (non-chip) P—CE systems have certain unmatched advantages, especially in the relative simplicity of the regular cylindrical geometry of the CE capillary, maximal volume-to-surface ratio, no need to design and to fabricate a chip, the low costs of capillary compared to chip, and better performance with some detection techniques. This review presents an overview of the state of the art of P—CE and literature relevant to futuredevelopments. We pay particular attention to the development and the potential of miniaturization of functional parts for P—CE. These include components related to sample introduction, separation and detection, which are the key elements in P—CE design. The future of P—CE may be in relatively simple, rugged designs (e.g., using a short piece of capillary fixed to a chip-sized platform on which injection and detection parts can be mounted). Electrochemical detection is well suited for miniaturization, so is probably the most suitable detection technique for P—CE, but optical detection is gaining interest, especially due to miniaturized light sources (e.g., light-emitting diodes).

A high temperature and shear rate capillary viscometer has been designed, constructed and recently commissioned. This device will be used to measure the viscosity of semi-solid metals under the high temperature and shear rate conditions, similar to those found in industry. Design criteria for the device included a requirement for a highly controllable temperature (±1ºC) up to 650ºC, capability for injection shear rates above 10,000s−1 and controllable injection profiles. The design of this viscometer was aided with the use of numerical modelling methods based on a power law thixotropic fluid flow relation. This analysis allowed calculation of required injection speeds and expected system forces. Computational modelling work, based on current power law fluid models, was also performed in order to investigate how the viscosity would be expected to fluctuate with shear rate and fraction solid. This data could then be used to compare with experimental work. The computational model was a 2D two-phase theoretical unsteady state model. This was used to evaluate the viscosity of semi-solid metals passing through the designed capillary viscometer at injection speeds of 0.075, 0.5 and 1 m/sec. The effects of fractions solid (fs) of the metal from 0.25, 0.3, 0.33 and 0.50 were also investigated. Strong correlations between these parameters and the resulting viscosity were noted.

In recent years variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, became evident in championship matches. The current standard has not provided adequate repeatability of ball performance. A new method for assessing the dynamic impact behaviour of approved sliotar cores has been characterised. This test system was developed to measure the performance characteristics, such as coefficient of restitution, deformation and contact time, and the viscoelastic properties of dynamic stiffness and hysteresis energy dissipation. In this paper, the relationship between the viscoelastic properties and the coefficient of restitution is presented.

During the last two decades, the development of laboratory scale extreme ultraviolet sources has been intensified due to growing interest in use of extreme ultraviolet sources photons for various applications in science and technology. In this study, we present a potential application of extreme ultraviolet sources surface modification of polymers to be used as substrates for cancer cell identification. The surface modification of polytetrafluoroethylene (PTFE) polymer samples was performed by a lab scale compact laser-plasma extreme ultraviolet sources source based on a double-stream gas-puff target. The gas target was irradiated with a 3 ns/0.8 J Nd:YAG laser pulse at 10 Hz with 50 and 300 pulses. HCV29 non-malignant transitional epithelium and T24 bladder cells adhesion and proliferation studies on pure and extreme ultraviolet sources modified PTFE surfaces were performed. The extreme ultraviolet sources modified surfaces demonstrated regular increase in cancer cell proliferation comparing to pristine sample. Initial results indicate that extreme ultraviolet sources treated substrates can facilitate the identification of cancer cells

In this paper, we outline a novel technique for the deposition of nanostructured thin films utilizing a modified form of pulsed laser deposition (PLD). We demonstrate confined atmospheric PLD (CAP) for the deposition of gold on cyclic olefin polymer substrates. The deposition process is a simplified form of conventional PLD, with deposition conducted under atmospheric conditions and the substrate and target in close proximity. It was found that this confinement results in the deposition of nanostructured thin films on the substrate. Infrared spectroscopy showed no significant change of polymer surface chemistry as a result of the deposition process, and optical spectroscopy revealed plasmonic behavior of the resulting thin film. The effect of laser fluence on the deposition process was also examined with more uniform films deposited at higher fluences.

Oxide ceramic matrix composites (CMCs) are promising materials for extreme application environments where high temperatures combined with mechanical loads under oxidative or corrosive conditions are required. Oxide ceramic matrices must be developed to build composites that fulfill these requirements. This article disserts on the aspects of sol-gel processing and freeze gelation most important for their application in the production of ceramic matrix composites. Several methods for matrix infiltration and preform fabrication are also discussed, with a focus on the filament winding technique. Finally, the final properties of materials prepared via the filament winding and freeze gelation techniques is demonstrated.

Thanks to their peculiar morphing capabilities, Shape Memory Alloys (SMA) materials are being increasingly adopted in many engineering fields, such as automotive and aerospace. Indeed, their pseudo-elastic behavior and their shape memory effect, which allows the recovery of an initial state after a deformation, make them particularly suitable for switch actuators and morphing structures applications. In this work, the behavior of SMAs is investigated. Then, a user defined material model (UMAT) has been implemented in the Abaqus Standard Finite Element (FE) environment to numerically simulate the behavior of SMAs, including their pseudo-elastic behavior and shape memory effect. The material model, validated by means of comparisons with analytical data, has been used to investigate the feasibility of a bi-stable biased actuator operated by SMA springs.

Lap joining configuration for Friction Stir Welding process is a methodology mostly dedicated to heterogeneous bonding. This welding technology was applied to join pure titanium with pure aluminum by varying the rotation speed and the movement speed of the tool. Regardless of the process parameters, it was found that the maximum strength of the junction remains almost constant. Microstructural observations by means of Scanning Electron Microscopy and Energy Dispersive Spectrometry analysis enable to describe the interfacial join and reveal asymmetric Cold Lap Defects on the sides of the junction. Chemical analysis shows the presence of one exclusive intermetallic compound through the interface identified as TiAl3. This compound is responsible of the crack spreading of the junction during the mechanical loading.The original version of this article supplied to AIP Publishing contained an accidental inversion of the authors, names. An updated version of this article, with the authors names formatted correctly was published on 20 October 2017.Lap joining configuration for Friction Stir Welding process is a methodology mostly dedicated to heterogeneous bonding. This welding technology was applied to join pure titanium with pure aluminum by varying the rotation speed and the movement speed of the tool. Regardless of the process parameters, it was found that the maximum strength of the junction remains almost constant. Microstructural observations by means of Scanning Electron Microscopy and Energy Dispersive Spectrometry analysis enable to describe the interfacial join and reveal asymmetric Cold Lap Defects on the sides of the junction. Chemical analysis shows the presence of one exclusive intermetallic compound through the interface identified as TiAl3. This compound is responsible of the crack spreading of the junction during the mechanical loading.The original version of this article supplied to AIP Publishing contained an accidental inversion of the aut...

The aim of this paper is to study how knowledge is generated during a product's design. We show how the knowledge generation takes place and how it should be used. That means to use the generated and capitalised knowledge for internal and external learning; learning and training should be considered as a highly added value service which accompanied any physical product. Some potential ways of knowledge usage is explored and some results are provided helping decision-makers to perform their tasks as efficiently as possible. This is a generic learning positioning grid. To design a product for learning is our research field.