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1
Ramaswamy, Raghupathy. "Thermal behavior of food materials during high pressure processing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1190122901.
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Kotecha, Rutvij. "Atmospheric Pressure Microwave Plasma for Materials Processing and Environmental Applications." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342544640.
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Amouroux-Berthe, Solange Claire. "Pressure driven transport of non-wetting fluids in membranes used in composite processing." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 254 p, 2009. http://proquest.umi.com/pqdweb?did=1885755801&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Taveri, Gianmarco. "Geopolymers Incorporating Wastes and Composites Processing." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-403861.
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Buildings construction and realization of public infrastructures have always been a primary need in the human society, developing low cost and user-friendly materials which also encounter safety and durability requirements. Portland cement is the most used material in construction industry from the industrial revolution up to date, but the raising concerns related to the climate change are pushing the governments worldwide to replace it with more eco-friendly and greener materials. Geopolymers are considered to be best alternatives to Portland cement in construction industry, but issues related to cost and mechanical properties are still hindering the commercialization of this material. Geopolymer incorporating wastes is one of the solutions. Fly ash, a thermal power plant by-product, and borosilicate glass, a recycled glass from pharmaceutical vials, are suitable candidates in geopolymers activation. NMR and FTIR spectroscopies demonstrated that borates from borosilicate glass are active compounds in geopolymerization, substituting the alumina is its role, composing a B-Al-Si network never observed before. Various fly ash and borosilicate glass weight contents were studied in terms of mechanical properties (compression test, 3-point bending test). It was found that fly ash 55 wt.% and borosilicate 45 wt.% composition activated in 13 M NaOH solution holds the best compressive and flexural strength (45 and 4 MPa respectively), 25% stronger than similar counterparts found in literature. Cellulose fibres in different weight contents were dispersed into the geopolymeric paste to produce geopolymer composites, with the aim to render the material more suitable for structural applications. 3-point bending test showed an improvement of the flexural strength of about 165% (12 MPa), while the chevron notch method displayed a fracture toughness of 0.7 MPam1/2, in line with the results of geopolymer composites found in literature. In this thesis work, fly ash was also successfully densified in 3 M NaOH solution and distilled water through a new method based on hydraulic pressure, called hydro-pressure sintering. This innovative technology involves a drastic reduction of NaOH utilization in geopolymerization, rendering the material more eco-friendly. XRD spectroscopy conducted on produced samples revealed a higher formation of crystals, most likely induced by the application of hydraulic pressure (450 MPa).
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Hannibal, Paul. "Compressibility Measurement and Modeling to Optimize Flow Simulation of Vacuum Infusion Processing for Composite Materials." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4433.
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Out-of-autoclave manufacturing processes for composite materials are increasing in importance for aerospace and automotive industries. Vacuum Infusion processes are leading the push to move out of the autoclave. An understanding of the various process parameters associated with resin infusion is necessary to produce quality product. Variance in compaction, resin, and vacuum pressures are studied, concentrating on developing a compaction pressure profile as it relates to fiber volume fraction. The purpose of this research is twofold: (1) to show and quantify the existence of a resin pressure gradient in compression testing using rigid tooling, and (2) to use measured test data to validate and improve resin flow simulation models. One-dimensional compression tests revealed a pressure gradient across the diameter of the compression tool. The pressure gradient follows trends consistent with Darcy's Law. Compression tests revealed fabric hysteresis during compaction as shown in previous studies. Fiber compaction pressure was found to not be directly equal to compressive forces of the Instron when resin is present in the system. The relationship between Instron, resin and compaction pressures is defined. The compression study was used to validate previously developed flow simulation models. Resin pressures are critical to developing an accurate two-dimensional radial flow simulation for low permeability fabrics. It is feasible to determine final fiber volume fraction at a given compaction pressure.
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Moussa, Sherif Omar Hassan. "Transient processing and characterizatin of advanced materials /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115572.
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Kyriazis, Panagiotis A. "Analysis and processing of mechanically stimulated electrical signals for the identification of deformation in brittle materials." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4604.
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The fracture of brittle materials is of utmost importance for civil engineering and seismology applications. A different approach towards the aim of early identification of fracture and the prediction of failure before it occurs is attempted in this work. Laboratory experiments were conducted in a variety of rock and cement based material specimens of various shapes and sizes. The applied loading schemes were cyclic or increasing and the specimens were tested to compression and bending type loading of various levels. The techniques of Pressure Stimulated Current and Bending Stimulated Current were used for the detection of electric signal emissions during the various deformation stages of the specimens. The detected signals were analysed macroscopically and microscopically so as to find suitable criteria for fracture prediction and correlation between the electrical and mechanical parameters. The macroscopic proportionality of the mechanically stimulated electric signal and the strain was experimentally verified, the macroscopic trends of the PSC and BSC electric signals were modelled and the effects of material memory to the electric signals were examined. The current of a time-varying RLC electric circuit was tested against experimental data with satisfactory results and it was proposed as an electrical equivalent model. Wavelet based analysis of the signal revealed the correlation between the frequency components of the electric signal and the deformation stages of the material samples. Especially the increase of the high frequency component of the electric signal seems to be a good precursor of macrocracking initiation point. The additional electric stimulus of a dc voltage application seems to boost the frequency content of the signal and reveals better the stages of cracking process. The microscopic analysis method is scale-free and thus it can confront with the problems of size effects and material properties effects. The AC conductivity time series of fractured and pristine specimens were also analysed by means of wavelet transform and the spectral analysis was used to differentiate between the specimens. A non-destructive technique may be based on these results. Analysis has shown that the electric signal perturbation is an indicator of the forthcoming fracture, as well as of the fracture that has already occurred in specimens.
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Gireesh, Guruprasad. "INFLUENCE OF PROCESSING VARIABLES ON MICROSTRUCTURE DEVELOPMENT AND HARDNESS OF BULK SAMPLES OF TWO NOVEL CERAMICS PREPARED BY PLASMA PRESSURE COMPACTION." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1144246756.
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Bancora, Simone. "Characterization of fabric layups by pressure print analysis and simulation of dual-scale flow based on topological skeletonization : application to composite materials processing." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0049.
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Dans cette thèse, nous nous intéressons aux préformes fibreuses dans le cadre du procédé Resin Transfer Moulding (RTM). L'objectif de la thèse est double : proposer une nouvelle méthodologie pour obtenir des données géométriques à la mésoéchelle des préformes et fournir un nouveau modèle numérique capable de prédire la perméabilité ou d'effectuer des simulations d’écoulement efficaces à la méso-échelle. Dans la première partie, l'accent est mis sur l'acquisition de données géométriques : nous proposons une nouvelle méthodologie basée sur l'analyse du champ de pression supporté par une préforme sèche sous compactage. Un film sensible à la pression mesure le champ de pression par un empilement de plis contre les parois du moule. Profitant de l’architecture périodique des textiles, les empreintes révélées par le champ de pression sont interprétées par analyse spectrale de Moiré pour mesurer l'orientation et la distribution spatiale de chaque couche dans l’empilement. Dans la seconde partie, le modèle numérique de la préforme est utilisé pour effectuer des simulations numériques d'écoulement à l'échelle des fils, afin d’en caractériser la perméabilité ou d’effectuer directement des simulations de remplissage. La géométrie 3D de l’empilement est remplacée par un squelette préservant les propriétés topologiques nécessaires à la résolution numérique du problème d'écoulement bidimensionnel, réduisant considérablement le coût de calcul par rapport à une approche 3D complète. Ce modèle de réduction du volume poreux en squelette est d'abord formulé dans sa version simple échelle (écoulement inter-mèche), puis étendu en double échelle (écoulement inter- et intra-mèche). Le potentiel du modèle est illustré à travers plusieurs cas tests. Cette recherche propose une méthodologie allant de l'acquisition de données géométriques à la simulation numérique double-échelle de l'écoulement au sein dans un empilement de tissus<br>In this work, we study continuous fiber preforms in the context of Resin Transfer Moulding (RTM) processes. The aim of the thesis is two-fold: propose a new methodology to obtain mesoscale geometrical data from preforms and provide a new numerical model able to predict permeability or perform mesoscale filling simulations in a computationally efficient way. In the first part, the focus is on the acquisition of geometrical data from preforms: we propose a novel methodology based on the analysis of the pressure field experienced by a dry preform under compaction. By using a commercial pressure-sensitive film, the pressure field exerted by a stack of layers against mould walls is captured and analyzed. Taking advantage of the periodic morphology of textiles, geometric patterns revealed by the pressure field are interpreted according to spectral Moiré analysis to recover the orientation and spatial distribution of each individual layer in the stack. In the second part, the reconstructed digital architecture of the preform is used to carry out numerical flow simulations at the scale of the yarns, to characterize permeability of the stack or directly perform filling simulations. The stack geometry is replaced by a skeletonized representation of the same, on which a two-dimensional flow problem can be solved numerically, greatly reducing the computational cost when compared to a full 3D approach. This “medial skeleton” model is first formulated in its single-scale version (flow in channels) and then extended to dual-scale (flow in channels and yarns). The model potential is illustrated through several test cases. This research establishes a pathway going from the non-destructive acquisition of data to the simulation of the dual-scale flow inside a multi-layer layup of textiles
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Bessho, Naoki. "Advanced pressure swing adsorption system with fiber sorbents for hydrogen recovery." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42822.
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A new concept of a "fiber sorbent" has been investigated. The fiber sorbent is produced as a pseudo-monolithic material comprising polymer (cellulose acetate, CA) and zeolite (NaY) by applying hollow fiber spinning technology. Phase separation of the polymer solution provides an appropriately porous structure throughout the fiber matrix. In addition, the zeolite crystals are homogeneously dispersed in the polymer matrix with high loading. The zeolite is the main contributor to sorption capacity of the fiber sorbent. Mass transfer processes in the fiber sorbent module are analyzed for hydrogen recovery and compared with results for an equivalent size packed bed with identical diameter and length. The model indicates advantageous cases for application of fiber sorbent module over packed bed technology that allows system downsizing and energy saving by changing the outer and bore diameters to maintain or even reduce the pressure drop. The CA-NaY fiber sorbent was spun successfully with highly porous structure and high CO2 sorption capacity. The fiber sorbent enables the shell-side void space for thermal moderation to heat of adsorption, while this cannot be applied to the packed bed. The poly(vinyl alcohol) coated CA-NaY demonstrated the thermal moderation with paraffin wax, which was carefully selected and melt at slightly above operating temperature, in the shell-side in a rapidly cycled pressure swing adsorption. So this new approach is attractive for some hydrogen recovery applications as an alternative to traditional zeolite pellets.
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Souza, Ricson Rocha de. "Sinterização e caracterização de SrBi2Ta2O9 obtido por processamento em alta pressão e baixas temperaturas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/141957.
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O processamento em alta pressão é um método alternativo para a produção de materiais cerâmicos. Neste trabalho, pressões na ordem de 7,7 GPa e 2,5 GPa foram aplicadas em amostras, em diferentes temperaturas, que foram colocadas em uma célula de reação específica, gerando diferentes efeitos na formação de fases. A composição de fases foi analisada por difração de raios X e a evolução microestrutural, associada ao processamento em alta pressão, foi investigada por microscopia eletrônica por varredura em associação com a espectroscopia por dispersão de energia. Um analisador de resposta de frequência foi utilizado para obter as curvas ferroelétricas por espectroscopia de impedância eletroquímica. A utilização de alta pressão (2,5 GPa) possibilitou a obtenção de amostras de SrBi2Ta2O9 monofásicas com elevada densidade relativa, acima de 93%, após sinterização a uma temperatura de 900 °C. Essa temperatura é inferior às usualmente necessárias para obter alta densificação utilizando métodos convencionais de sinterização. Além disso, as amostras processadas em alta pressão apresentaram uma resposta dielétrica similar às amostras de SrBi2Ta2O9 sinterizadas por processos convencionais em temperaturas acima de 1000 ºC.<br>High-pressure processing is a very attractive approach for the production of ceramic materials. In this work, pressures about 7.7 GPa and 2.5 GPa were applied in SrBi2Ta2O9 samples at different temperatures placed in a specific reaction cell. X-ray diffraction was used to identify the different phases produced as a function of the processing conditions. The microstructural evolution, associated to the high-pressure processing, was investigated by scanning electron microscopy in association with energy dispersive spectroscopy. Frequency response analysis was used to obtain the ferroelectric curves by electrochemical impedance spectroscopy. A highly densified (> 93% of theoretical density) single-phase (SrBi2Ta2O9) sample was obtained after processing at 2.5 GPa and 900 ºC. This temperature is lower than those necessary to obtain high densification, when conventional sintering processes are employed. In addition, the samples produced by high pressure processing showed a dielectric response similar to SrBi2Ta2O9 samples sintered by conventional processes at temperatures above 1000 ºC.
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Penny, George B. S. "High-pressure synthesis of electronic materials." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4161.
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High-pressure techniques have become increasingly important in the synthesis of ceramic and metallic solids allowing the discovery of new materials with interesting properties. In this research dense solid oxides have been synthesised at high pressures, and structural investigations have been conducted using x-ray and neutron diffraction. The perovskite LaPdO3 has been synthesised at pressures of 6{10GPa. Neutron diffraction studies have been carried out from 7{260K to investigate any structural distortions, particularly related to the possibility of charge order at low temperatures. No reduction in symmetry associated with charge ordering has been observed; the material appears to remain metallic with only one unique Pd site down to 7K. LaPdO3 adopts the GdFeO3-type Pbnm structure. The PdO6 octahedra exhibit a tetragonal distortion throughout the temperature range with a shortening of the apical Pd{O bonds of 2:5% relative to the equatorial bonds. Attempts to prepare analogues of the perovskite containing smaller rare earths have resulted in multi-phase samples, and further RPdO3 perovskites remain inaccessible although there is evidence for a small amount of the perovskite phase in the products of synthesis attempts with neodymium. Three new oxypnictide superconductors, RFeAsO1 xFx (R = Tb, Dy and Ho) have been synthesised at 7{12GPa. The materials are isostructural with other recently discovered iron arsenide superconductors and have Tc's of 52:8 K, 48:5K and 36:2K respectively, demonstrating a downturn in Tc in the series for smaller R. Systematic studies on TbFeAsO0.9F0.1 and HoFeAsO0.9F0.1 show negative values of dTc=dV in contrast to those reported for early R containing materials. Low-temperature neutron diffraction measurements on both materials, and synchrotron studies on HoFeAsO0.9F0.1 reveal no tetragonal to orthorhombic transitions as observed in early R-containing materials with lower doping levels. Magnetic reflections are evident but they are shown to be from R2O3 and RAs impurities with TN's of 5:5K for Tb2O3, 6:5K for HoAs and 1:7K < TN < 4K for Ho2O3. The implications of these results for superconductivity in the iron arsenides are discussed.
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Hsueh, Hung-Chung. "Physics of anisotropic materials under pressure." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/14119.
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The structural, vibrational, and electronic properties of anisotropic materials under compression are comprehensively investigated in this thesis. Recent developments in the techniques of high-pressure X-ray diffraction and Raman scattering, and significant advances in first principle simulations provide detailed high-pressure studies of condensed matter systems. In view of the widely disparate strength of cohesive forces, these studies consist of ionic compounds, quasi-two dimensional semiconductors, quasi-molecular solids, and end with liquid crystals. As a result of the coexistence of different hierarchical interactions in anisotropic systems, evidence of preferential pressure-induced enhancement of weak bonding is found not only in the structural response to external hydrostatic pressure but also in vibrational and electronic behaviour. Further, the understanding of pressure-induced breakdown of rigid-layer vibrations (explored in layered compounds), pressure-induced electron transfer in molecular crystals, and strong overlap of inter- and intra-molecular vibrational modes of liquid crystals provides insight into the essential physics of flexible molecular systems.
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Davidson, Alistair J. "High-pressure studies of energetic materials." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/16976.
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Although high pressure has been used extensively to study a range of materials that include metals, minerals, and ices, a class of material that has received rather less attention is energetic materials (explosives, propellants). The work presented has used high-pressure techniques to investigate polymorphism in energetic materials. Novel-high pressure phases of RDX (cyclotrimethylenetrinitramine or cyclonite) and ammonium perchlorate are reported, which have both been structurally characterised using single-crystal X-ray and powder neutron diffraction. Of particular importance has been the successful determination of the structure of the elusive high-pressure –form of RDX. Equations of state for both polymorphs of both compounds have been determined. High-pressure measurements of HMX (cyclotetramethylenetetranitramine or octogen) revealed no phase transitions up to 8.46 GPa. An equation of state up to this pressure has been determined. Crystallisation of HMX from DMSO at 0.1 GPa gives a 1:2 HMX-DMSO solvate which has been structurally characterised by single-crystal X-ray diffraction. The high-pressure behaviour of TATP (triacetone triperoxide) has been explored. Hydroxylammonium perchlorate has been investigated using high-temperature single-crystal X-ray diffraction and powder neutron diffraction, and a high-temperature phase has been fully structurally characterised for the first time. High-pressure studies of hydroxylammonium perchlorate indicate the presence of two new polymorphs. High-pressure measurements have been conducted on ammonium nitrate up to 7.85 GPa, showing no phase transitions. An equation of state has been determined over this pressure range. Studies have also been undertaken on the simple molecular compound thiourea dioxide. Two new high-pressure phases have been identified and structurally characterised using both single-crystal X-ray and powder neutron diffraction.
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McMonagle, Charles James. "Effect of pressure on porous materials." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31504.
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Research to design and synthesise new porous materials is a rapidly growing field with thousands of new systems proposed every year due to their potential use in a multitude of application in a wide range of fields. Pressure is a powerful tool for the characterisation of structure-property relationships in these materials, the understanding of which is key to unlocking their full potential. In this thesis we investigate a range of porous materials at a range of pressures. Over time the chemical architecture and complexity of porous materials has increased. Although some systems display remarkable stability to high-pressures, which we generally think of as being above 1 GPa (10,000 bar), in general, the compressibility of porous materials have increased substantially over the last 10 years, rendering most unstable at GPa pressures. Here we present new methods for investigating porous materials at much more moderate pressures (100's of bar), alongside more traditional high-pressure methods (diamond anvil cell techniques), finishing with gas sorption studies in a molecular based porous material. Here, the design and development of a new moderate pressure sapphire capillary cell for the small molecule beamline I19 at the Diamond Light Source is described. This cell allowed access to pressures of more than 1000 bar regularly with a maximum operating pressure of 1500 bar with very precise pressure control (< 10 bar) on both increasing and decreasing pressure. This cell closes the gap between ambient pressure and the lowest pressures attainable using a diamond anvil cell (DAC), which is generally above 0.2 GPa (2000 bar). Along with the development of the sapphire capillary pressure cell, the compression to 1000 bar of the small organic sample molecule Hexamethylenetetramine (hexamine, C6H12N4) and its deuterated form (C6D12N4) was determined, demonstrating the precision possible using this cell. Solvent uptake into porous materials can induce large structural changes at 100's of bar. In the case of the Sc-based Metal-organic framework (MOF), Sc2BDC3 (BDC = 1,4-benzenedicarboxylate), we used the sapphire capillary pressure cell to study changes in the framework structure on the uptake of n-pentane and isopentane. This work shows how the shape and smaller size of n-pentane facilitated the swelling of the framework that could be used to explain the increase in stability of the MOF to applied pressure. The effect of pressure on the previously unreported Cu-framework bis[1-(4- pyridyl)butane-1,3-dione]copper(II) (CuPyr-I) was investigated using high-pressure single-crystal diffraction techniques (DAC). CuPyr-I was found to exhibit high-pressure and low-temperature phase transitions, a pressure induced Jahn- Teller switch (which was hydrostatic medium dependent), piezochromism, and negative linear compressibility. Although each of these phenomena has been reported numerous times in a range of materials, this is to the best of our knowledge the first example to have been observed within the same material. The final two chapters investigate the exceptional thermal, chemical, and mechanical stability of a porous molecular crystal system (PMC) prepared by the co-crystallisation of a cobalt phthalocyanine derivative and a fullerene (C 60 or C70). The stabilising fullerene is captured in the cavity between two phthalocyanines in a ball and socket arrangement. These PMCs retain their porous structure: on the evacuation of solvent of crystalisation; on heating to over 500 K; on prolonged immersion in boiling aqueous acid, base, and water; and at extreme pressures of up to 5.85 GPa, the first reported high-pressure study of a PMC. the reactive cobalt cation is accessible via the massive interconnected voids, (8 nm3), as demonstrated by the adsorption and binding of CO and O2 to the empty metal site using in situ crystallographic methods available at beamline I19, Diamond Light Source.
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Staneff, Geoff D. Asimow Paul David. "High-pressure synthesis of thermoelectric materials /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05262005-004951.
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Patz, Timothy Matthew. "Laser Processing of Biological Materials." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7451.
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I have explored the use of the matrix assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW) to create thin films of biological materials. MAPLE is a novel physical vapor deposition technique used to deposit thin films of organic materials. The MAPLE process involves the laser desorption of a frozen dilute solution (1-5%) containing the material to be deposited. A focused laser pulse (~200 mJ/cm2) impacts the frozen target, which causes the solvent to preferentially absorb the laser energy and evaporate. The collective action of the evaporated solvent desorbs the polymeric solute material towards the receiving substrate placed parallel and opposite to the target. The bioresorbable polymer PDLLA and the anti-inflammatory pharmaceutical dexamethasone were processed using MAPLE, and characterized using Fourier transform infrared spectroscopy, atomic force microscopy and x-ray photoelectron spectroscopy. MDW is a CAD/CAM controlled direct writing process. The material to be transferred is immersed in a laser-absorbing matrix or solution and coated onto a target or support positioned microns to millimeters away from a receiving substrate. Using a UV microscope objective, a focused laser pulse is directed at the backside of the ribbon, so that the laser energy first interacts with the matrix at the ribbon/matrix interface. This energy is used to gently desorb the depositing material and matrix onto the receiving substrate. I have deposited neuroblasts within a three-dimensional extracellular matrix. These two laser processing techniques have enormous potential for functional medical device and tissue engineering applications.
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Liyanage, Chamadari Hemamala Uswatte Kruger Michael B. "High pressure studies of negative thermal expansion materials and nanocrystalline materials." Diss., UMK access, 2007.
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Thesis (Ph. D.)--Dept. of Physics and Dept. of Mathematics. University of Missouri--Kansas City, 2007.<br>"A dissertation in physics and mathematics." Advisor: Michael B. Kruger. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed July 16, 2008. Includes bibliographical references (leaves 137-143). Online version of the print edition.
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Lakshmanan, Ramamoorthi. "High-pressure processing of cold-smoked salmon." Thesis, University of Strathclyde, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415299.
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Lukinov, Tymofiy. "Atomistic modeling of materials under extreme pressure." Licentiate thesis, KTH, Kondenserade materiens teori, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145172.
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This thesis is dealing with simulation of polycrystalline materials underthe conditions of anisotropic pressure and temperature. Work has been carriedout in three steps: Research of the inuence of point defects and grain boundaries on theprocess of melting. The inuence of defects' concentration, grain sizeand lattice direction mismatch on the superheating temperature wasstudied. Investigation of the boundaries of application of the metadynamics methodto the simple atomic model with Buckingham interaction. The solidsolidphase transition, where one of the phases has temperature inducedstability was conrmed. We found the optimal size of simulation boxto study the solid-solid phase transitions using the metadynamics technique. A model of polycrystalline materials based on macroscopic approximationwas formulated. This model was applied to the model of the polycrystallinematerial using cellular automata. Using this approximationthe eect of anisotropic stress caused by anisotropic heating was studied.<br><p>QC 20140611</p>
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Gulia, Kiran. "Pulsed laser processing of dielectric materials." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2035.
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The thesis investigates the wavelength dependent laser ablp..~ion in dielectric materials used for the fabrication ofhigh density Printed Circuit Boards (PCBs) in the electronics industry. Here the market for consumer and industrial products of ever-rising complexity has led to a demand for increased miniaturisation and low costs of multilevel printed circuit boards (PCBs) interconnected by microvias, which electrically connect the various circuit layers. Laser machining offers a potential solution to this need. The main objective of the research is to investigate the wavelength-dependence of the laser machining/drilling efficiency of two important sets of PCB materials, categorised as Organics and Ceramics using a carbon dioxide laser which can be tuned across its emission spectrum in the 9flm - 11 flm spectral region.. The organics include commercially available electronic materials with trade names such as Kapton, ArIon, FR4 and RCC and the ceramics materials studied are alumina and low temperature cofired ceramic (LTCC). The aim is to determine the optimum laser wavelength for maximum processing efficiency Le. to find the wavelength where the laser parameters are best matched to the optical, thermal and mechanical properties of each of the materials. A CO2 laser machining system was constructed which incorporated a novel laser source developed in the research programmes. The laser source was a MOPA system with a line-tuneable cw oscillator and a five pass power planar waveguide rf discharge-excited power operating in the so-called enhanced power regime to produce maximum peak power. An Acousto-optic modulator between the master oscillator and the amplifier allowed convenient control of pulse amplitude and duration. The system enabled the wavelength dependent studies on the wavelength and pulse energy dependence of the laser ablation properties (e.g. ablation threshold fluence and ablation rates) - to derive the so-called 'ablation spectrum' of the selected materials A comparison is made of the wavelength dependence of ablation with the room temperature absorption spectrum measured for each material using ellipsometry. It was observed that the 'ablation spectrum' information does not always appear to match the simple expectations derived from the room temperature 'absorption spectrum' of the material. This disparity in results is likely due to the change of absorption properties of • material because of rise in temperature, chemical decomposition or melting of material during ablation. However, the room temperature absorption spectrum (while not adequate alone), did provide a useful guide to the selection of a sub-set of the 40+ lines that would otherwise have to be studied. The results may be of direct application in the electronics industry to increase the efficiency oflaser machining.
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Thomas, Rachel Elizabeth. "High temperature processing of kaolinitic materials." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/6075/.
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Calcination, is the process of heating a substance, to a temperature below its fusing point, with a resultant loss of water. It is one of the most important techniques currently used to enhance the properties, and therefore value, of kaolin. The overall aim of this project was to provide a better understanding of the principles of the kaolin calcination reaction in order to enhance the efficiency, quality and sustainability of the Imerys calcining operations. This research has shown a strong correlation between the chemistry of kaolin and the colour of the calcined product. This is due to the influence of contaminant materials on the colour of the hydrous kaolin, which in turn affects the calcined material. The strongest colour influencing factor is the presence of iron, particularly if it is present on the surface of the kaolin. Surface iron is currently reduced using a reductive bleaching process. This has an improving influence on even the most contaminated kaolins, however there can be quite a lot of interbatch variability. Despite its effect on colour the chemistry of kaolin has little influence on post calcination reactivity. Reactivity is due to physical factors such as particle and agglomerate size and the penetration of heat into the material. Any kaolin will calcine to produce a low reactivity product; provided the heat is able to penetrate into the bed and that the material is able to remain at temperature for sufficient time for the calcination reaction to occur. Another outcome of the research was the discovery that a higher temperature and shorter time period has little on the end calcined product but has implications for lower energy usage.
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Tobin, Amberly Hope. "OHD Processing of Coal Waste Materials." OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2045.
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AN ABSTRACT OF THE THESIS OF Amberly Hope Tobin, for the Master of Science degree in Organic Geochemistry, presented on August 4th 2016, at Southern Illinois University Carbondale. TITLE: OHD PROCESSING OF COAL WASTE MATERIALS MAJOR PROFESSOR: Dr. Susan M. Rimmer This research addresses coal-waste utilization via the OHD process and the implications for both economic and environmental impacts. The goal of this project is to determine if coal-waste products can be processed by the OHD technique. Furthermore, this project will determine what types of products are produced from the coal-waste materials and will compare these to those produced by the OHD processing of raw coal. This research has the potential to be beneficial to the coal industry as OHD would allow production of high-value products from what is currently viewed as a waste material; additionally, this research will provide a way to recycle what is considered a hazardous waste product and provide an incentive to reclaim coal slurry ponds that are an environmental concern. A preliminary suite of grab samples from an active coal slurry pond along with a stream reject sample were obtained in order to determine if these types of materials could be processed via OHD. After these samples were deemed viable in the OHD process, core samples were taken from a large slurry pond. These cores were then ii sampled at 2 ft (0.61 m) intervals. The key analyses performed were geochemical, petrographic, OHD, and GC-MS. Geochemical analysis included carbon, sulfur, moisture, volatile matter, ash, and fixed carbon content of the coal-waste samples before OHD, and provided a basis for comparison with raw coal samples. Petrographic analysis was performed to determine the maceral composition before the OHD processing. The OHD process is the core technique of this research project. The preliminary slurry pond samples were processed in a small semi-continuous OHD reactor. While the stream reject and slurry pond core samples were processed using a continuous OHD reactor, as this type of reactor is best suited for fine-grained slurries. GC-MS was used to examine the OHD liquid products analysis in order to determine the types of compounds present in the final liquefied product; these products were then compared to raw coal OHD products in order to determine their economic potential. Petrography of the coal-waste materials showed that these samples did contain a notable amount of coal; predominantly vitrinites and inertinites were observed in the samples. Geochemical analysis proved that there were significant amounts of organic carbon in these materials, ranging between 25 and 37%. OHD processing was successful on all coal-waste materials, although the continuous OHD reactor tended to work better with the fine-grained slurries than the semi-continuous OHD reactor. The GC-MS analysis of the coal-waste OHD product showed very similar suites of compounds to that of a bulk coal OHD product; in general, almost all major compounds that are found in a typical coal OHD product were also found in the coal-waste OHD products. This suggests that these slurry ponds, which are typically regarded as waste products, could be viable feedstocks for OHD processing.
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SONG, HYO-JIN. "PROCESSING PHASE TRANS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132249697.
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Baklar, Mohammed Adnan. "Processing organic semiconductors." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1311.
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In recent years, there has been a considerable interest in organic semiconducting materials due to their potential to enable, amongst other things, low-cost flexible opto-electronic applications, such as large-area integrated circuitry boards, light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Promisingly, improved electronic performance and device structures have been realized with e.g. OLEDs entering the market and organic field-effect transistors (OFETs) reaching the performance of amorphous silicon devices; however, it would be too early to state that the field of organic semiconductors has witnessed the sought-after technological revolution. Initial progress in the field was mostly due to synthetic efforts in the form of enhanced regularity and purity of currently used materials, the creation of new molecular species, etc. In this thesis we show that the advancement of physico-chemical aspects – notably materials processing – and the realisation of increased order and control of the solid state structure is critical to realize the full intrinsic potential that organic semiconductors possess. We first investigated how the bulk charge-transport properties of the liquid-crystalline semiconductor poly(2,5-bis (3-dodecylthiophen-2-yl)thieno[3,2-b]thiophenes) (pBTTT-C12) can be enhanced by annealing in the mesophase. To this end, temperature treatment of a period of hours was necessary to realize good bulk charge transport in the out-of-plane directions. This behaviour is in strong contrast to in-plane charge transport as measured in thin-film field-effect structures, for which it was shown that annealing times of 10 min and less are often sufficient to enhance device performance. Our observation 4 may aid in future to optimize the use of pBTTT polymers in electronic devices, in which good bulk charge transport is required, such as OPVs. In the second part of thesis, we explored ink-jet printing of pBTTT-C12, in order to realize precise deposition of this material into pre-defined structures. In organic electronic applications this can, amongst other things, enable deposition of different semiconductors or reduction of the unwanted conduction pathways that often result in undesirable parasitic ‘cross-talk’, for instance, between pixels in display products. We demonstrate the integration of ink-jet printed transistors into unipolar digital logic gates that display the highest signal gain reported for unipolar-based logic gates. Finally, recognizing that a broad range of conjugated organic species fall in the category of “plastic crystals”, we explored the option to process this class of materials in the solid state. We find that solid-state compression moulding indeed can effectively be applied to a wide spectrum of organic small molecular and polymeric semiconductors without affecting adversely the intrinsic favourable electronic characteristics of these materials. To the contrary, we often observe significantly enhanced [bulk] charge transport and essentially identical field-effect transistor performance when compared with solution- or melt-processed equivalents. We thus illustrate that fabrication of functional organic structures does not necessitate the use of solution processing methods, which often require removal of 99 wt% or more of solvent, or precursor side-products, nor application of cumbersome vapour deposition technologies.
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King, Alexander J. "High Pressure Processing of Corn and Wheat Starch :." Connect to this title online, 2005. http://hdl.handle.net/1811/298.
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Thesis (Honors)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formattted into pages: contains 46 p.; also includes graphics. Includes bibliographical references (p. 42-46). Available online via Ohio State University's Knowledge Bank.
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Al-Zubaydi, Ahmed. "High-pressure torsion processing of AZ91 magnesium alloy." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386345/.
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AZ91 magnesium alloy has been successfully processed at room temperature by high–pressure torsion as well as at elevated temperatures. Ultrafine grains and nano–sized particles of β–phase have developed with increasing number of turns. The hydrostatic pressure, the geometry of the processing zone and the unidirectional nature of torsional straining during the HPT processing have facilitated processing of AZ91 alloy at room temperature. Extensive grain refinement and twinning segmentation of the coarse grains have been observed in the microstructures processed at room temperature and elevated temperatures, respectively. The twins have been observed at all processing temperatures during processing and their distribution was proportional to the processing temperature and number of turns. The morphology and distribution of the β–phase have altered during processing, with fragmentation of coarse clusters of the β–phase into nano–sized particles and the alignment of these particles in the direction of torsional strain being observed. Microstructural homogeneity has gradually developed at a relatively low number of turns using the lower processing temperature and continued with increasing number of turns. A significant improvement in the strength of the alloy has been found after HPT processing at all processing temperatures. The dislocation density has developed significantly for the alloy processed at room temperature rather than at elevated temperatures with increasing number of turns. An experimental Hall–Petch relationship has emphasized a significant dependence of the strength on grain size for the alloy processed at room temperature. The high–strain rate superplasticity, low–temperature superplasticity, and thermal stability of the processed alloy have been observed and attributed to the ultrafine–grained microstructures produced by HPT at room temperature and the dispersion of nano–sized β–phase particles. Grain–boundary sliding was the main deformation mechanism during the high–strain rate superplasticity regime. Glide–dislocation creep accommodated by grain–boundary sliding was the deformation mechanism operating during the low–temperature superplasticity regime. At high temperature and slow strain rate grain–boundary sliding was accommodated by a diffusion creep mechanism.
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Thumthanaruk, Benjawan. "The effect of high pressure processing on polyphenoloxidase /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486463321626645.
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Horkeby, Filip, and Melanie Larsson. "Quality Assurance of Pressure Equipment Materials and Steelwork." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127336.
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Kvalitetskraven i samhället blir allt högre och det blir allt tuffare för producenterna att hålla de kvalitetskrav som krävs av kund, men också att uppnå de kvalitetsdirektiv som finns i EU idag. Det finns idag en mängd olika definitioner på vad kvalitet är och hur kvaliteten ska uppnås. EU kräver att alla produkter ska ha CE-märkning, vilket är en försäkring om att produkterna håller den kvalitet som definierad av EUs lagstiftning. För att möta de krav som finns på kvalitet idag undersöker Siemens Industrial Turbomachinery AB om deras leverantörer följer de direktiv som krävs för tryckbärande anordningar. För att materialen i de tryckbärande anordningarna ska vara godkända krävs det att ståltillverkaren är godkänd för tillverkningen. Ståltillverkaren ska kunna bekräfta godkännandet genom att uppvisa ett så kallat PED certifikat (Pressure Equipment Directive, 97/23/EC).
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Kelsey, Alasdair. "Computer simulation of pressure effects in tetravalent materials." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/15142.
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<I>Ab initio</I> electronic structure calculations within the density functional formalism have been performed to study the behaviour of various types of bonding under pressure. Primarily covalent bonding is studied in the III-V semiconductor materials GaAs and InSb by studying their sequence of phase transitions under pressure. The stability of a new phase of GaAs is reported. Calculations on the more ionic copper halides have also been performed. The effect of directional bonding on the ease with which the lowest energy structure is found can then studied by comparison of the two systems. Simulations of the layered material TiS<SUB>2</SUB> under pressure show good agreement with experiment and the calculated band structures show a semiconductor to semi-metal transition at approximately the same pressure as experiment. Some of the motivation for studying materials under pressure comes from effects caused by lattice mis-match in semiconductor heterojunctions. The last chapter concerns whether the macroscopic theory of elasticity can be applied to heterojunctions where there are just a few inserted layers. While theory holds for the stoichiometric InAs in GaAs it is shown to fail in the case of AlAs in Si.
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MENESCARDI, FRANCESCA. "HIGH PRESSURE MATERIALS DISCOVERY WITH ADVANCED COMPUTATIONAL METHODS." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/822394.
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The focus of this thesis is the prediction of new materials that can be formed or synthesized under
high pressure. It has been shown by several works in literature, that pressure can alter the
chemistry of an element by activating its (semi)core electrons, unoccupied orbitals and even the
non-atom-centered quantum orbitals located on the interstitial sites, leading to many new
surprising phenomena.
In this work I applied three different strategies to predict new compounds under pressure:
explore known polymorphs (aka prototypes)
global optimization via genetic algorithms
data mining and high-throughput calculations
The first strategy can be easily applied to compounds with few components, fixed stoichiometry
and at moderate pressure. The idea is that atoms with similar radius and valence tend to
crystallize with the same structure. This is the case of ABO3 oxides which constitute the largest
family of oxides: the crystal structure at ambient pressure is found to depend on the atomic radii
of the elements. The most common is the perovskite structure where tilting of octahedra and offcentering
of the B-cation is responsible for a large variety of physical properties. In addition to the
perovskite structure few other structures are know (i.e. ilmenite, wollastonite, calcite, aragonite,
enstatite, corundum). The most important is the post-perovksite which is formed from the
perovskite structure when the rotation of the octahedra exceeds a critical angle.
The second strategy is more computationally expensive than the first and must used when the
pressure is very high and when the stoichiometry is not fixed because of pressure-induced
chemical reactions. In this case pressure induces such large changes in the valence configuration
that no iso-structural compound exists at ambient pressure. Crystal structure prediction is in
principle a computationally intractable problem. In recent years, clever optimization methods such
as genetic algorithms (i.e. USPEX) have provided an effective and successful solution to this
problem.
The third strategy builds upon the ideas of the first strategy by trying to establish structure-property
relations. Here the aim is to find new materials with specific physical properties by
exploring existing databases. Where information is missing, high-through calculations are used to
fill in the blanks. This field of research is very active and was boosted by machine learning in the
last few years. The main drawback of machine learning is that it is not always interpretable and
accessible to experimental groups. In this thesis I report two case studies: the first is the search of
exfoliable topological materials and the search low/ambient-pressure post-perovskites.
Calculations were performed employing plane wave code Quantum Espresso (QE).
In addition to these three topics, my PhD work focused also on improving the reality of first
principles calculations such that they can be directly compared to experiments. The first issue I
addressed is the dependence of the calculated equations of state (EOS) on the choice of the
exchange-correlation (XC) functional. This is extremely important in magnetic perovskites like
SrRuO3 since the volume affects the magnetic moments and vice versa. I found the PBEsol
functional reproduces the EOS and lattice parameters of perovskites with few exceptions. In the
case of post-perovskites the calculated lattice parameters show some systematic deviations from
the experimental ones.
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English, Jennifer M. "Wireless micromachined ceramic pressure sensors for high termperature environments." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15790.
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Kaewmaraya, Thanayut. "First-Principles Studies of Materials Properties : Pressure-Induced Phase Transitions & Functional Materials." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-251343.
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This thesis presents the first-principles studies of materials properties within the framework of the density functional theory (DFT). The thesis constitutes three main parts, i. e., pressure-induced phase transitions in solids, data-storage and clean-energy materials. The first part focuses on the predictions of crystal structures and the determinations of electronic properties of Xe-H2, FeB4 and Co3O4. Pressurizing Xe-H2 compound yields the formation of H-rich Xe(H2)8, which can exhibit a metallic feature at comparatively lower pressure than pure hydrogen. Hard superconducting FeB4 gets transformed into a novel transparent phase under pressure owing to the enhanced overlap of atomic cores. Spinel Co3O4 undergoes the phase transition from a cubic to a monoclinic because of the charge transfer between cations via the increased 3d-3d interactions. The second part involves the study of structural and electronic properties of phase-change memory materials (PCMs), i. e., Ge2Sb2Te5 (GST) and Ga-doped In2O3. Van der Waals (vdW) interaction must be considered to obtain accurate crystal structure of layered GST. For Ga-doped In2O3 (GIO), the local structure of amorphous GIO is found to resemble that of amorphous In2O3, except the vicinity of doping atoms. The electronic property of a-GIO is metallic, which considerably differs from the semiconducting feature of the crystalline GIO. This emphasizes the contrast in the conductivity of the crystalline and amorphous upon phase switching of GIO. The third part associates with the search for clean-energy materials, viz., hydrogen production, hydrogen storage and green Mg-ion batteries. For hydrogen production, the role of intrinsic point defects to water adsorption on ZnO(10-10) surface is investigated. The findings show that the Zn and O defect-sites are energetically not favorable for the water adsorption and dissociation. For the purpose of storing hydrogen in a solid phase, silicene, doped by alkaline and alkaline earth metals, is investigated. We find that Li-doped and Na-doped silicene can attain the superior storage capacity. For cathode material of Mg-ion batteries, Mg2Mo6S8, the diffusivity of Mg ions occurs through an available channel in the bulk with the onset temperature of 200 K.
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Dinda, Guru Prasad. "Nonequilibrium processing of amorphous and nanostructured materials." Karlsruhe FZKA, 2006. http://nbn-resolving.de/urn:nbn:de:0005-072055.
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Rozenburg, Keith Gregory. "Processing study of fine grained piezoelectric materials." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/18948.
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Lin, Chang-Yi. "Processing and properties of functionally gradient materials." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284594.
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Moorhouse, Colin. "Laser processing of printed circuit board materials." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/195.
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Legros, Robert. "Processing of vegetable materials in fluidised beds." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/847633/.
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Fluidised beds have not yet been widely utilised for processing of vegetable products. The main reason is that the materials often possess physical properties that render them difficult to handle by existing fluidisation techniques. The vegetable product chosen for this work is cut lamina tobacco provided by British American Tobacco Company Limited. The objectives of this project are to develop a fluidised bed device capable of handling cut lamina tobacco and to investigate the use of the device for heat and mass transfer operations. It is shown that conventional technology, such as spouted beds or slot spouted beds, cannot cope with cut lamina tobacco because of its entangled nature. A novel design of contacting device is developed, suitable for maintaining controlled inventory of cut lamina tobacco. The device uses relatively high velocity gas jets to create a well defined flow pattern which the solid follows, thereby disentangling the tobacco fibres. Heat transfer experiments show that heat transfer coefficients in the mobilised bed are sufficiently high to permit rapid equilibration of the bed mass with the gas. The high recirculation rate of the solid also ensures that the temperature is uniform everywhere in the bed. Drying tests in the mobilised bed show that the overall mass transfer is not gas phase limited but is controlled by internal migration of moisture within the tobacco particles. The effective diffusion coefficients calculated from the drying curves showed an Arrhenius-type relationship with temperature, with values in the range 2.7X10[-6] to 17.5X10[-6] cm[2]/s for a temperature range of 40°-85°C. Mobilisation of the tobacco results mainly from momentum transfer from the gas jets to the plug of tobacco. The maximum bed pressure drop is below that calculated to support the bed weight (or DeltaP[mf]), due to the contribution of the inlet momentum flux of the mobilising gas jets. A model is developed which adequately predicts the maximum mobilising flowrate at incipient mobilisation. The heat and mass transfer equations combined with the analysis of incipient mobilisation are used in a demonstration design of a complete continuous mobile bed dryer for a primary tobacco process.
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Tsang, Sideny C. N. "Processing and rheological studies of cellulosic materials." Thesis, Sheffield Hallam University, 1987. http://shura.shu.ac.uk/20456/.
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The present studies are concerned with the modelling of the manufacturing process of nitrocellulose-base propellant in which cellulose acetate is substituted as a model for the explosive nitrocellulose. An investigation of the inter-relationships between processing and rheological and morphological properties has been carried out on cellulose acetate doughs, using modified torque and capillary extrusion rheometers. Some of the doughs show a yield stress and behave as Herschel-Bulkley fluids. The yield stress is found to be smaller than that of nitrocellulose doughs, and there is some evidence of shear heating. Mixing time and mixing temperature showed no influence on the rheological parameters of the doughs. These results suggest that the change in rheological properties of propellant doughs is attributed to the change in crystallinity and fibrosity after processing. The rheological properties of doughs are greatly affected by extrusion temperature, solvent, plasticiser and filler content. The interaction between the solvents and plasticisers with cellulose acetate was explained by adopting a model consisting of a rigid backbone chain from which protruded flexible side groups. In good solvents these side groups extend causing interactions between molecules, giving rise to dough up and elasticity. In poor solvents, dough up becomes difficult and the elasticity is low because the flexible side groups retract towards the stiff backbone chain. The morphology of solvated doughs is examined using solution viscometry, infrared spectroscopy, scanning electron microscope, differential scanning calorimetry, x-ray diffraction and dynamic mechanical thermal analysis. All these techniques showed that the solvation process had no significant effect on the molecular architecture of the cellulose acetate, in which the original crystallinity of the material is low. From this it was concluded that changes in the rheological properties of nitrocellulose doughs as a function of the process variables was due to changes induced in the crystallites rather than in the amorphous regions.
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Santamato, Alberto. "Quantum information processing with integrated photonic materials." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707742.
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Kachlík, Martin. "Processing of Electroceramic Materials for Advanced Applications." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-234434.
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Disertační práce se zabývá přípravou pokročilých keramických materiálů se zajímavými fyzikálními vlastnostmi. Materiály, připravené v rámci této práce, byly vyrobeny tuho-fázovými popř. hydrotermálními syntézami. První ze zkoumaných materiálů je elektrokeramika EuTiO3 s perovskitovou mřížkou. Absence termodynamických dat tohoto systému vedla k rozsáhlému experimentálnímu výzkumu vhodných podmínek jeho přípravy. Tři směsi práškových prekurzorů (Eu2O3 s Ti2O3 nebo TiO2 – rutil či anatas) byly homogenizovány mletím v planetovém mlýnu a formovány izostatickým tlakem 300 MPa. Vzniklé keramické polotovary diskového tvaru byly slinovány konvenčními metodami v redukčních atmosférách (Ar + 7 % H2 nebo pouze čistý H2) popř. pokročilou slinovací metodou Spark Plasma Sintering (SPS). Následně byl studován vliv slinovací metody, teploty, složení atmosféry a prodlevy na finální hustotu a fázovou čistotu vzorků. Tento výzkum vyústil v úspěšnou přípravu jednofázové EuTiO3 objemové keramiky s relativní hustotou vyšší než 95 % teoretické hustoty (%TH). S ohledem na dostupnou literaturu jsou tyto materiály jedinými publikovanými vzorky fázově čisté EuTiO3 keramiky s tak nízkou porozitou. Důležitost těchto výsledků je podložena čtyřmi publikacemi v impaktovaných časopisech, kde byly vlastnosti měřené na těchto vzorcích prezentovány. Spektra infračervené odrazivosti byla porovnána s výsledky v literatuře. Byla tak demonstrována nezbytnost fázově čistých vzorků s minimálním porozitou pro měření jejich reálných (neovlivněných) fyzikálních vlastností. Další výzkum byl zaměřen na hydrotermální syntézu (HTS) keramického prášku Eu0,5Na0,5TiO3. Prezentované HTS byly uskutečněny ve vysoce zásaditém prostředí vodných roztoků NaOH nebo KOH při teplotách 220 – 250 °C. Experimenty s různými koncentracemi prekurzorů (EuCl3 a TiCl4) a redukčních činidel vedly k přípravě jednofázového práškového perovskitu Eu0,5Na0,5TiO3 s krychlovými částicemi s rozměry pod 1 m. Jiný titaničitan - MgTiO3 – byl syntetizován tuho-fázovou reakcí směsi práškových prekurzorů MgO a TiO2. Směsi byly mechanicky aktivovány v kulovém mlýnu po dobu 0, 10, 40, 80 nebo 160 min. Keramická tělesa byla slinována pomocí dvou různých přístupů a to buď metodou Two-step Sintering (TSS) na teplotách 1300 °C (30 min) a následně 1200 °C (20 h) nebo nejprve konvenčním slinováním při 1300 °C popř. 1400 °C po dobu 30 min a poté ještě pomocí metody Hot Isostatic Press (HIP) na 1200 °C popř. 1280 °C. V případě HIP-ovaných vzorků při 1280 °C po 3 hodiny v inertní Ar atmosféře o tlaku 200 MPa byly získány fázově čisté keramické vzorky MgTiO3 s relativní hustotou nad 93 %TH. Poslední z prezentovaných materiálů je Ba(Ca)Ti(Zr)O3 bezolovnatá piezokeramika, která byla připravena tuho-fázovou reakcí práškových směsí mletých v planetovém kulovém mlýnu za rozdílných podmínek. Keramická tělesa lisovaná izostatickým tlakem (300 MPa) byla dále zhutněna beztlakým slinováním na teplotách 1200, 1300, 1400 popř. 1500 °C po dobu 1 h na vzduchu. Byly studovány potřebné podmínky pro přípravu jednofázové perovskitové Ba0,85Ca0,15Ti0,9Zr0,1O3 keramiky s požadovanou mikrostrukturou. Úspěšně tak byly připraveny vzorky fázově čisté Ba(Ca)Ti(Zr)O3 keramiky o relativní hustotě až 96 %TH. Prezentované výsledky potvrzují význam volby vhodné metody výroby a potřebných parametrů k získání pokročilých elektrokeramických materiálů s požadovanou mikrostrukturou i fázovým složením a tudíž i pro správné stanovení jejich fyzikálních vlastností.
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Sequeira, Lopes Tavares Sandra. "Optimisation of low pressure processing for honeycomb sandwich structures /." [S.l.] : [s.n.], 2009. http://library.epfl.ch/theses/?nr=4497.
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Shook, Carla Marie. "The effects of high pressure processing on diced tomatoes." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1392909096.
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Lou, Fangfei. "Survival of Nonculturable Human Noroviruses during High Pressure Processing." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408727004.
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Huang, Ching-Yao. "Applications of Pressure Cycling on Metal Matrix Composite Processing /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933648651449.
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Michel, de Arévalo Aymeé. "Phytosterol enrichment in vegetable oil by high pressure processing." Aachen Shaker, 2008. http://d-nb.info/994829892/04.
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Lecky, Matthew. "Continuous high pressure carbon dioxide processing of watermelon juice." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011651.
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Dancer, Claire E. J. "Ceramic processing of magnesium diboride." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:40e122d4-5bdf-4cf4-b23b-5d7286ede4c0.
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This thesis describes the fabrication and characterization of ex situ magnesium diboride (MgB<sub>2<) bulk material to study its sintering behaviour. Since the discovery of superconductivity in magnesium diboride in 2001, many research studies have identified the attractive properties of this easy-to-fabricate, low cost superconductor which can attain high critical current density even without heat-treatment. However there is little consensus in the literature on the processing requirements to produce high quality MgB<sub>2< material with low impurity content and high density. In this work, the key parameters in the production of dense ex situ MgB<sub>2< produced from Alfa Aesar MgB<sub>2< powder are established by examining the effect of modifying the characteristics of the starting material and the processing parameters during pressureless and pressure assisted heat-treatment. The particle size distribution, impurity content and particle morphology of Alfa Aesar MgB<sub>2< powder were determined using laser dffraction, X-ray diffraction, X-ray photoelectron spectroscopy, electron dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. This powder was also modified by separation (sieving and sedimentation) and milling (ball milling and attrition milling), with changes made to the powder determined by the same techniques. A pressureless heat-treatment method using a magnesium diboride powder bed was developed. This minimised MgO formation in samples produced from as-purchased MgB<sub>2< powder to less than 8 wt.% for heat-treatment at 1100°C. MgO content was determined by X-ray diffraction using calibrated standards. MgB<sub>2< bulk material was produced from as-purchased and modified powders by pressureless heat-treatment under Ar gas, and characterized using Archimedes' density method, X-ray diffraction, Vickers hardness testing, scanning electron microscopy, and magnetization measurements. Very limited densification was observed for all samples prepared by pressureless heat-treatment, with only limited increases in connectivity observed for some samples heat-treated at 1100°C. Pressure-assisted bulk samples were prepared from as-purchased MgB<sub>2< and selected modified powders using resistive sintering, spark plasma sintering, and hot pressing. These were characterized using the same techniques, which indicated much more extensive densification with similar levels of impurity formation as for pressureless heat-treatment at 1100°C. The results indicate that densification and applied pressure are strongly correlated, while the effect of temperature is less significant. The optimum processing environment (inert gas or vacuum) was dependent on the technique used. These results indicate that pressure-assisted heat-treatment is required in order to produce dense bulk MgB<sub>2<.
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Court, Simon E. C. "The ignition of polymeric materials in high-pressure oxygen." Thesis, London South Bank University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618661.
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Baril, Martin. "A high-pressure vibrational study of metal pyrophosphate materials /." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99320.
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The effect of high external pressures on the Raman spectra of various metal pyrophosphate salts has been investigated with the aid of a diamond-anvil cell and a Raman microspectrometer. The pressure dependences of the Raman-active bands were determined from the wavenumber vs. pressure plots. The KMHP2O7·2H2O [M = Co(II), Mn(II), Zn(II) and Mg(II)] series of salts was studied at pressures up to about 50 kbar (ca. 50,000 atm). The Co(II) salt displayed an irreversible, pressure-driven, structural transformation at around 29 kbar. The M4(P2O 7)2·10H2O [M = Zn(II) and Mn(II)] salts were also investigated. A reversible phase transition was observed to take place for the Zn(II) salt in the pressure range of 15-20 kbar. Three other pyrophosphate materials, K4P2O7, Co 2P2O7·6H2O and Ca2KH 3(P2O7)2·3H2O, were also examined at high-pressure, but no pressure-driven phase transitions were observed in these cases.