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T Sands - One of the best experts on this subject based on the ideXlab platform.
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understanding the rocksalt to wurtzite phase Transformation through Microstructural analysis of al sc n epitaxial thin films
Applied Physics Letters, 2016Co-Authors: Bivas Saha, Sammy Saber, Eric A Stach, E P Kvam, T SandsAbstract:Rocksalt-to-wurtzite structural phase transitions in semiconducting materials (such as III–V nitrides, ZnO, CdSe, and others) have been studied for several decades. Almost all experimental works related to this phase transition involve diamond anvil cells to apply hydrostatic pressure, and as a result, direct observation of the Microstructural Transformation during the phase transition has not been possible. In this article, we have addressed and uncovered the intimate Microstructural details and epitaxial relationships between phases by capturing what is essentially a thin-film snapshot of the Transformation after growth of AlxSc1-xN films with a composition chosen to be close to the equilibrium phase boundary between wurtzite and rocksalt. The results support the hypothesis that the Transformation is triggered by defects at rs- {01¯1} growth fronts that offer a nearly invariant plane with respect to the parallel w- {21¯1¯0} planes. The intermediate crystal structures and their epitaxial relationships ar...
M. E. Fitzpatrick - One of the best experts on this subject based on the ideXlab platform.
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Effect of near-surface residual stress and microstructure modification from machining on the fatigue endurance of a tool steel
Journal of Materials Engineering and Performance, 2002Co-Authors: F. Ghanem, H. Sidhom, C. Braham, M. E. FitzpatrickAbstract:This study concerns the effect of machining on the fatigue life of an EN X155CrMoV12 tool steel (SAE J438b), with regard to the generation of near-surface residual stress and Microstructural modification of the machined surface. Two possible methods for machining tool steels were compared: electro-discharge machining (EDM), a high energy density process, and milling, a more conventional cutting process. Particular attention was given to characterization of the surface roughness, microstructure, and residual stress, using a combination of Microstructural analysis, crack observation, scanning electron microscopy (SEM), x-ray diffraction (XRD), and chemical composition changes by energy-dispersive x-ray. A decrease of around 35% in the fatigue limit was observed for the EDM samples, compared with the milled samples. This was attributed to a tensile residual stress state after EDM, combined with significant phase Transformation and hydrogen embrittlement. The milled surfaces showed no Microstructural Transformation or surface cracking and contained compressive residual stresses, all of which contributed to an improved fatigue resistance.
Le Feunteun STEVEN - One of the best experts on this subject based on the ideXlab platform.
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Digestion of milk protein gels in simulated gastric environment: exploration of the disintegration process and diffusion behavior of pepsin
2016Co-Authors: Floury Juliane, BIANCHI Tiago, THEVENOT Jonathan, Dupont Didier, Jamme Frederic, Lutton Evelyne, Panouille Maud, Boue François, Le Feunteun STEVENAbstract:The gastric digestion comprises three phases: physical disintegration, chemical breakdown and nutrient release. Controlling food proteins gelation conditions leads to the formation of particles with specific structural features that change protein digestibility. The development of foods with specific proteolysis rates allows their fit to different ‘nutritional vulnerable groups’ (newborn,elderly, obese, athletes) needs. The hypothesis is that the overall proteolysis reaction rate is limited by the pepsin diffusion rate within the protein structures generated in the stomach.Three milk gels with the same protein concentration but different microstructures were prepared either by rennet, acid coagulation of non-fat milk, or heat treatment of whey proteins. The disintegration of the different gel networks was investigated under digestion in simulated gastric conditions, and the effect of the acidic environment uncoupled from the enzyme effect. The first effect was monitored during 30 minutes before addition of pepsin for two hours of digestion.Kinetics of the process was surveilled by particle size measurements and matter loss.Proteolysis was characterized by SDS-PAGE, and diffusion of fluorescently labelled (FITC) pepsin within the gels was followed using fluorescent recovery after photobleaching with confocal microscopy. In contrast to acid and whey protein gels, rennet gels underwent large Microstructural modifications under acidic conditions, forming extremely compact protein aggregates that significantly slowed down pepsin diffusion rates through the modified gel network. Microscopic observations showed slower morphological evolution during the enzymatic digestion, whose rates depended on the gel considered. Moreover, pepsin was able to diffuse within the aggregates.Recent microscopic observations obtained by tryptophan fluorescence imaging on the SOLEIL synchrotron DISCO beamline suggest that the particles were enzyme digested inside out. In this study, we succeeded in interpret the digestion phases as Microstructural Transformation,enzymatic reaction and diffusion phenomena in order to further dismantle the digestion process from a process engineering perspective.
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Digestion of milk protein gels in simulated gastric environment: exploration of the disintegration process and diffusion behavior of pepsin
2016Co-Authors: Floury Juliane, BIANCHI Tiago, THEVENOT Jonathan, Dupont Didier, Jamme Frederic, Lutton Evelyne, Panouille Maud, Boue François, Le Feunteun STEVENAbstract:The gastric digestion comprises three phases: physical disintegration, chemical breakdown and nutrient release. Controlling food proteins gelation conditions leads to the formation of particles with specific structural features that change protein digestibility. The development of foods with specific proteolysis rates allows their fit to different ‘nutritional vulnerable groups’ (newborn,elderly, obese, athletes) needs. The hypothesis is that the overall proteolysis reaction rate is limited by the pepsin diffusion rate within the protein structures generated in the stomach.Three milk gels with the same protein concentration but different microstructures were prepared either by rennet, acid coagulation of non-fat milk, or heat treatment of whey proteins. The disintegration of the different gel networks was investigated under digestion in simulated gastric conditions, and the effect of the acidic environment uncoupled from the enzyme effect. The first effect was monitored during 30 minutes before addition of pepsin for two hours of digestion.Kinetics of the process was surveilled by particle size measurements and matter loss.Proteolysis was characterized by SDS-PAGE, and diffusion of fluorescently labelled (FITC) pepsin within the gels was followed using fluorescent recovery after photobleaching with confocal microscopy. In contrast to acid and whey protein gels, rennet gels underwent large Microstructural modifications under acidic conditions, forming extremely compact protein aggregates that significantly slowed down pepsin diffusion rates through the modified gel network. Microscopic observations showed slower morphological evolution during the enzymatic digestion, whose rates depended on the gel considered. Moreover, pepsin was able to diffuse within the aggregates.Recent microscopic observations obtained by tryptophan fluorescence imaging on the SOLEIL synchrotron DISCO beamline suggest that the particles were enzyme digested inside out. In this study, we succeeded in interpret the digestion phases as Microstructural Transformation,enzymatic reaction and diffusion phenomena in order to further dismantle the digestion process from a process engineering perspective.
J A Szpunar - One of the best experts on this subject based on the ideXlab platform.
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evaluation of microstructure and texture across the welded interface of super duplex stainless steel and high strength low alloy steel
Surface & Coatings Technology, 2015Co-Authors: Abbas Eghlimi, M Shamanian, Masoomeh Eskandarian, Azam Zabolian, Majid Nezakat, J A SzpunarAbstract:Abstract The evolution of microstructure and texture across the fusion boundary of a dual-layer super duplex stainless steel clad metal produced on a high strength low alloy steel substrate by gas tungsten arc welding process was examined by optical microscopy, X-ray diffraction, electron backscatter diffraction, and energy-dispersive X-ray spectroscopy. It was found that a martensitic band with occasional Type I and Type II boundaries separated the substrate's heat affected zone from the high austenite containing region of the clad metal. Due to the competitive growth, both the ferrite and austenite grains showed almost the same ║ ND orientation near the fusion boundary. While the texture of the austenite was not as strong as that of the ferrite across the cladding layers, the results confirmed that the austenite daughter phase was formed with a close Kurdjumov–Sachs orientation relationship with respect to the parent ferrite phase. It was also found that although both the residual stress and reheating caused some Microstructural Transformation and texture modification to some parts of the cladding, the major factors affecting the texture were unidirectional solidification, competitive growth, and δ/γ orientation relationship. The only exception was related to the occasional highly deformed mostly austenite area adjacent to the fusion boundary, where partial recrystallization led to formation of some annealing twins. The findings suggested that the reheating which occurred during the deposition of the second layer generated higher ferrite content and produced some secondary austenite with dominant Widmanstatten morphology across the first cladding layer. Moreover, it imposed higher residual strain and also promoted limited recrystallization adjacent to the fusion boundary.
Bivas Saha - One of the best experts on this subject based on the ideXlab platform.
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understanding the rocksalt to wurtzite phase Transformation through Microstructural analysis of al sc n epitaxial thin films
Applied Physics Letters, 2016Co-Authors: Bivas Saha, Sammy Saber, Eric A Stach, E P Kvam, T SandsAbstract:Rocksalt-to-wurtzite structural phase transitions in semiconducting materials (such as III–V nitrides, ZnO, CdSe, and others) have been studied for several decades. Almost all experimental works related to this phase transition involve diamond anvil cells to apply hydrostatic pressure, and as a result, direct observation of the Microstructural Transformation during the phase transition has not been possible. In this article, we have addressed and uncovered the intimate Microstructural details and epitaxial relationships between phases by capturing what is essentially a thin-film snapshot of the Transformation after growth of AlxSc1-xN films with a composition chosen to be close to the equilibrium phase boundary between wurtzite and rocksalt. The results support the hypothesis that the Transformation is triggered by defects at rs- {01¯1} growth fronts that offer a nearly invariant plane with respect to the parallel w- {21¯1¯0} planes. The intermediate crystal structures and their epitaxial relationships ar...