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Pengsheng Wei - One of the best experts on this subject based on the ideXlab platform.
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Using the universal phase diagrams to describe Pore Shape development in solid for different solidification rates
International Journal of Heat and Mass Transfer, 2020Co-Authors: Pengsheng Wei, Yi-ji Huang, C.c. ChangAbstract:Abstract This study shows that there exist the universal three phase diagrams to describe general development of the Pore Shape in solid, resulting from a bubble captured by a solidification front with different solidification rates. Pore formation and its Shape strongly determine microstructural quality of materials, functional materials encountered in biology, chemistry, engineering, foods, and phenomena of geophysics and climate change, and so on. The solidification rate plays an important role in solute transport and gas pressure, contact angle of the bubble cap, and Pore Shape in solid. Three universal phase diagrams are under dimensionless coordinate systems of (1) solidification rate, temperature gradients in solid and liquid at the solidification front, (2) solidification rate, contact angle and growth rate of base radius of the cap, and (3) apex radius, contact angle and base radius of the cap. Solidification rate is determined by temperature gradients in liquid and solid at the solid-liquid interface governed by the Stefan boundary condition, whereas apex radius is determined by solute gas pressure in the Pore governed by the Young-Laplace equation, equation of state, and different cases governing directions of mass transfer in the Pore. Extending previous analysis, phase diagrams in this study confirm that the bubble cannot be completely entrapped in Case 2b, which represents a stronger effect of Pore volume expansion on solute gas pressure than solute transport from the surrounding liquid to Pore in the early stage. The computed and measured results of development of the Pore Shape are in good agreement.
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Effects of initial contact angle on Pore Shape in solid
International Journal of Thermal Sciences, 2018Co-Authors: Pengsheng Wei, S.y. Hsiao, Wang LiweiAbstract:Abstract The Pore Shape affected by initial contact angle of a bubble entrapped by a solidification front is predicted. Initial contact angle affects bubble nucleation, surface area and solute transport across the bubble cap, solid gas pressure in the Pore and Shape of Pores in solid. Porosity influences microstructure and functional properties of materials, etc. This work accounts for solute transport across the coupled Shape of cap in balance of pressures and physico-chemical equilibrium. Similar to previous work, it shows that Pore Shape depends on directions and magnitudes of solute across the cap. In contrast to Case 2, solute transport in Case 1 is from the Pore into surrounding liquid in the early stage. The results find that a decrease in initial contact angle expedites bubble entrapment in Case 1. Solute gas pressure in the Pore further exhibits three stages for initial contact angle greater than 90°. Significant drops occur in the early and late stages. In the middle stage, where contact angle is near 90°, solute concentration at the cap is about initial solute concentration in liquid, and responsible for length of the Pore. Except for initial contact angle less than 90°, an isolated Pore cannot be formed in Case 2. The predicted Pore Shape agrees with experimental data.
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Effects of physico-chemical interfacial equilibrium on Pore Shape in solid
International Journal of Heat and Mass Transfer, 2018Co-Authors: S.y. Hsiao, Pengsheng Wei, Wang LiweiAbstract:Abstract The Shape of a Pore, resulting from a bubble entrapped by a solidification front, for different Henry’s law constants at the cap is predicted in this work. Henry’s law, indicating an interfacial physico-chemical equilibrium, is essentially required to relate solute concentration in liquid at the cap by solute gas pressure in the Pore. Pore formation and its Shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work applies a previous model accounting for mass and momentum transport of solute across a self-consistently determined Shape of the bubble cap subject to different cases characterized by different directions and magnitude of solute transport across the cap. Case 1 is referred to solute transport from the Pore across cap to surrounding liquid in the early stage. Cases 2a and 2b, corresponding to low and high Henry’s law constants, respectively, indicate opposite directions of species transport across the cap. An increase in Henry’s law constant decreases Pore radius and time for entrapment in Case 1. The Pore cannot be entrapped as a Pore in solid in Cases 2. The predicted Pore Shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the Pore Shape have therefore been obtained.
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Effects of Bubble Location on Pore Shape in Solid
Journal of Mechanics, 2017Co-Authors: S.y. Hsiao, Pengsheng WeiAbstract:AbstractThe Shapes of a Pore resulting from an entrapped bubble by a solidification front for different locations of the bubble below the free surface are predicted in this work. Bubble location is an important factor affecting temperature gradient in liquid, solute gas dissipated into the ambient, heterogeneous nucleation of the bubble and Shape of the bubble cap, and subsequent entrapment and the Pore Shape in solid. The Shapes of Pores in solid influence not only material properties, but also contemporary issues of engineering, biology, medical technology and science, etc. This study takes into account solute transport across a coupling Shape of the Pore cap determined by the Young-Laplace equation governing balance of liquid, gas and capillary pressures. The results find that increases in depthwise location of a bubble increase Pore radius and time for bubble entrapment as solute transport is from the Pore across cap emerged through a concentration boundary layer along the solidification front into surrounding liquid in the early stage. On the other hand, the bubble cannot be entrapped, provided that solute transport in opposite directions across the cap submerged in a concentration boundary layer along the solidification front. The predicted growth and entrapment of a tiny bubble as a Pore in solid agree with experimental data. Understanding and controlling of the Pore Shape via controlling bubble location is of interest and challenging.
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Effects of supersaturation on Pore Shape in solid
Journal of Crystal Growth, 2017Co-Authors: Pengsheng Wei, S.y. HsiaoAbstract:Abstract The Shape of a Pore resulting from a bubble entrapped by a solidification front with different supersaturation ratios is predicted in this work. Supersaturation ratio, representing the ratio between solute concentration and saturation solute concentration, determines nucleation of a bubble and development of the Pore Shape in the early stage. Pore formation and its Shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work extends and combines previous models accounting for realistic mass and momentum transport, and physico-chemical equilibrium of solute gas across the bubble cap to self-consistently determine Shape of the bubble cap beyond the solidification front and the Pore Shape in solid. The study also deal with that Pore formation can be resulted from three different mechanisms, depending on the directions and magnitude of solute gas transport across the bubble cap. Case 1 is subject to solute transport from the Pore across the cap into the surrounding liquid in the early stage. Cases 2a and 2b indicate opposite direction of solute transport. In contrast to Case 2b, the effect of solute transport on solute gas pressure in the Pore in Case 2a is stronger than that of Pore volume expansionin the last stage. The results find that an increase in supersaturation ratio decreases Pore radius and time for bubble entrapment in Case 1. The bubble cannot be entrapped in Case 2. The predicted Pore Shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the Pore Shape have therefore been obtained.
S.y. Hsiao - One of the best experts on this subject based on the ideXlab platform.
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Effects of physico-chemical interfacial equilibrium on Pore Shape in solid
International Journal of Heat and Mass Transfer, 2018Co-Authors: S.y. Hsiao, Pengsheng Wei, Wang LiweiAbstract:Abstract The Shape of a Pore, resulting from a bubble entrapped by a solidification front, for different Henry’s law constants at the cap is predicted in this work. Henry’s law, indicating an interfacial physico-chemical equilibrium, is essentially required to relate solute concentration in liquid at the cap by solute gas pressure in the Pore. Pore formation and its Shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work applies a previous model accounting for mass and momentum transport of solute across a self-consistently determined Shape of the bubble cap subject to different cases characterized by different directions and magnitude of solute transport across the cap. Case 1 is referred to solute transport from the Pore across cap to surrounding liquid in the early stage. Cases 2a and 2b, corresponding to low and high Henry’s law constants, respectively, indicate opposite directions of species transport across the cap. An increase in Henry’s law constant decreases Pore radius and time for entrapment in Case 1. The Pore cannot be entrapped as a Pore in solid in Cases 2. The predicted Pore Shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the Pore Shape have therefore been obtained.
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Effects of initial contact angle on Pore Shape in solid
International Journal of Thermal Sciences, 2018Co-Authors: Pengsheng Wei, S.y. Hsiao, Wang LiweiAbstract:Abstract The Pore Shape affected by initial contact angle of a bubble entrapped by a solidification front is predicted. Initial contact angle affects bubble nucleation, surface area and solute transport across the bubble cap, solid gas pressure in the Pore and Shape of Pores in solid. Porosity influences microstructure and functional properties of materials, etc. This work accounts for solute transport across the coupled Shape of cap in balance of pressures and physico-chemical equilibrium. Similar to previous work, it shows that Pore Shape depends on directions and magnitudes of solute across the cap. In contrast to Case 2, solute transport in Case 1 is from the Pore into surrounding liquid in the early stage. The results find that a decrease in initial contact angle expedites bubble entrapment in Case 1. Solute gas pressure in the Pore further exhibits three stages for initial contact angle greater than 90°. Significant drops occur in the early and late stages. In the middle stage, where contact angle is near 90°, solute concentration at the cap is about initial solute concentration in liquid, and responsible for length of the Pore. Except for initial contact angle less than 90°, an isolated Pore cannot be formed in Case 2. The predicted Pore Shape agrees with experimental data.
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Effects of Bubble Location on Pore Shape in Solid
Journal of Mechanics, 2017Co-Authors: S.y. Hsiao, Pengsheng WeiAbstract:AbstractThe Shapes of a Pore resulting from an entrapped bubble by a solidification front for different locations of the bubble below the free surface are predicted in this work. Bubble location is an important factor affecting temperature gradient in liquid, solute gas dissipated into the ambient, heterogeneous nucleation of the bubble and Shape of the bubble cap, and subsequent entrapment and the Pore Shape in solid. The Shapes of Pores in solid influence not only material properties, but also contemporary issues of engineering, biology, medical technology and science, etc. This study takes into account solute transport across a coupling Shape of the Pore cap determined by the Young-Laplace equation governing balance of liquid, gas and capillary pressures. The results find that increases in depthwise location of a bubble increase Pore radius and time for bubble entrapment as solute transport is from the Pore across cap emerged through a concentration boundary layer along the solidification front into surrounding liquid in the early stage. On the other hand, the bubble cannot be entrapped, provided that solute transport in opposite directions across the cap submerged in a concentration boundary layer along the solidification front. The predicted growth and entrapment of a tiny bubble as a Pore in solid agree with experimental data. Understanding and controlling of the Pore Shape via controlling bubble location is of interest and challenging.
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Effects of supersaturation on Pore Shape in solid
Journal of Crystal Growth, 2017Co-Authors: Pengsheng Wei, S.y. HsiaoAbstract:Abstract The Shape of a Pore resulting from a bubble entrapped by a solidification front with different supersaturation ratios is predicted in this work. Supersaturation ratio, representing the ratio between solute concentration and saturation solute concentration, determines nucleation of a bubble and development of the Pore Shape in the early stage. Pore formation and its Shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work extends and combines previous models accounting for realistic mass and momentum transport, and physico-chemical equilibrium of solute gas across the bubble cap to self-consistently determine Shape of the bubble cap beyond the solidification front and the Pore Shape in solid. The study also deal with that Pore formation can be resulted from three different mechanisms, depending on the directions and magnitude of solute gas transport across the bubble cap. Case 1 is subject to solute transport from the Pore across the cap into the surrounding liquid in the early stage. Cases 2a and 2b indicate opposite direction of solute transport. In contrast to Case 2b, the effect of solute transport on solute gas pressure in the Pore in Case 2a is stronger than that of Pore volume expansionin the last stage. The results find that an increase in supersaturation ratio decreases Pore radius and time for bubble entrapment in Case 1. The bubble cannot be entrapped in Case 2. The predicted Pore Shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the Pore Shape have therefore been obtained.
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Bond number effects on Pore Shape in solid
International Journal of Thermal Sciences, 2017Co-Authors: S.y. Hsiao, Pengsheng WeiAbstract:Abstract The Pore Shape affected by Bond number, indicating the ratio between hydrostatic pressure and capillary pressure, of a bubble entrapped by a solidification front is predicted. Bond number is responsible for bubble nucleation, surface area and Shape of the bubble or Pore cap beyond the solidification front. Surface area determines solute transport across the cap, whereas contact angle of the cap delineates Pore Shape in solid. The critical velocity for entrapment of a bubble is also related to Bond number. Pore formation in solid influence not only microstructure of materials, but also contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work extends previous models accounting for mass and momentum transport of solute across a coupled Shape of the bubble cap to predict the Pore Shape in solid. The study also accounts for different directions and magnitudes of solute transport across the cap in different cases. Case 1 is subject to solute transport from the Pore across an emerged cap in a concentration boundary layer on the solidification front to surrounding liquid in the early stage. Case 2 indicates solute transport across a submerged cap in a concentration boundary layer to the Pore. In contrast to Case 2a, Pore value expansion in Case 2b exhibits a more important role in solute concentration at the cap than solute transport across the cap in the late stage. The results show that an increase in Bond number decreases Pore radius and time for bubble entrapment in Case 1. An isolated Pore cannot be formed in Cases 2a and 2b. The predicted growth and entrapment of a tiny bubble as a Pore in solid are found to agree with experimental data. A realistic prediction and control of the Pore Shape in solid via Bond number has therefore been obtained.
Willi Pabst - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Young’s modulus and thermal conductivity evolution of partially sintered alumina ceramics with Pore Shape changes from concave to convex
Journal of the European Ceramic Society, 2018Co-Authors: Tereza Uhlířová, Vojtěch Nečina, Willi PabstAbstract:Abstract Numerical calculations of the effective (relative) Young’s modulus and thermal conductivity have been performed for porous model materials on computer-generated digital microstructures with a transition from concave to convex Pore Shape. The results are compared to the case of purely concave and convex Pores (isolated or overlapping). It is shown that the Pabst-Gregorova cross-property relation for isotropic porous materials with isometric Pores gives an excellent prediction of effective (relative) properties for materials with a transition from concave to convex Pore Shape. With accuracy better than 0.010 relative property units (RPU) this prediction is far better than the prediction by any other cross-property relation currently known. For the intermediate (concave-convex) microstructures the accuracy of this cross-property relation is better than that for microstructures with purely concave Pores (accuracy better than 0.034 RPU) and, surprisingly, even better than for purely convex Pores (accuracy better than 0.011–0.013 RPU).
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modeling of young s modulus and thermal conductivity evolution of partially sintered alumina ceramics with Pore Shape changes from concave to convex
Journal of The European Ceramic Society, 2017Co-Authors: Tereza Uhlířová, Vojtěch Nečina, Willi PabstAbstract:Abstract Numerical calculations of the effective (relative) Young’s modulus and thermal conductivity have been performed for porous model materials on computer-generated digital microstructures with a transition from concave to convex Pore Shape. The results are compared to the case of purely concave and convex Pores (isolated or overlapping). It is shown that the Pabst-Gregorova cross-property relation for isotropic porous materials with isometric Pores gives an excellent prediction of effective (relative) properties for materials with a transition from concave to convex Pore Shape. With accuracy better than 0.010 relative property units (RPU) this prediction is far better than the prediction by any other cross-property relation currently known. For the intermediate (concave-convex) microstructures the accuracy of this cross-property relation is better than that for microstructures with purely concave Pores (accuracy better than 0.034 RPU) and, surprisingly, even better than for purely convex Pores (accuracy better than 0.011–0.013 RPU).
Tereza Uhlířová - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Young’s modulus and thermal conductivity evolution of partially sintered alumina ceramics with Pore Shape changes from concave to convex
Journal of the European Ceramic Society, 2018Co-Authors: Tereza Uhlířová, Vojtěch Nečina, Willi PabstAbstract:Abstract Numerical calculations of the effective (relative) Young’s modulus and thermal conductivity have been performed for porous model materials on computer-generated digital microstructures with a transition from concave to convex Pore Shape. The results are compared to the case of purely concave and convex Pores (isolated or overlapping). It is shown that the Pabst-Gregorova cross-property relation for isotropic porous materials with isometric Pores gives an excellent prediction of effective (relative) properties for materials with a transition from concave to convex Pore Shape. With accuracy better than 0.010 relative property units (RPU) this prediction is far better than the prediction by any other cross-property relation currently known. For the intermediate (concave-convex) microstructures the accuracy of this cross-property relation is better than that for microstructures with purely concave Pores (accuracy better than 0.034 RPU) and, surprisingly, even better than for purely convex Pores (accuracy better than 0.011–0.013 RPU).
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modeling of young s modulus and thermal conductivity evolution of partially sintered alumina ceramics with Pore Shape changes from concave to convex
Journal of The European Ceramic Society, 2017Co-Authors: Tereza Uhlířová, Vojtěch Nečina, Willi PabstAbstract:Abstract Numerical calculations of the effective (relative) Young’s modulus and thermal conductivity have been performed for porous model materials on computer-generated digital microstructures with a transition from concave to convex Pore Shape. The results are compared to the case of purely concave and convex Pores (isolated or overlapping). It is shown that the Pabst-Gregorova cross-property relation for isotropic porous materials with isometric Pores gives an excellent prediction of effective (relative) properties for materials with a transition from concave to convex Pore Shape. With accuracy better than 0.010 relative property units (RPU) this prediction is far better than the prediction by any other cross-property relation currently known. For the intermediate (concave-convex) microstructures the accuracy of this cross-property relation is better than that for microstructures with purely concave Pores (accuracy better than 0.034 RPU) and, surprisingly, even better than for purely convex Pores (accuracy better than 0.011–0.013 RPU).
B. X. Wang - One of the best experts on this subject based on the ideXlab platform.
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Microstructural effect on radiative scattering coefficient and asymmetry factor of anisotropic thermal barrier coatings
Journal of Quantitative Spectroscopy and Radiative Transfer, 2018Co-Authors: Xiang-feng Chen, Changying Zhao, B. X. WangAbstract:Abstract Thermal barrier coatings are common porous materials coated on the surface of devices operating under high temperatures and designed for heat insulation. This study presents a comprehensive investigation on the microstructural effect on radiative scattering coefficient and asymmetry factor of anisotropic thermal barrier coatings. Based on the quartet structure generation set algorithm, the finite-difference-time-domain method is applied to calculate angular scattering intensity distribution of complicated random microstructure, which takes wave nature into account. Combining Monte Carlo method with Particle Swarm Optimization, asymmetry factor, scattering coefficient and absorption coefficient are retrieved simultaneously. The retrieved radiative properties are identified with the angular scattering intensity distribution under different Pore Shapes, which takes dependent scattering and anisotropic Pore Shape into account implicitly. It has been found that microstructure significantly affects the radiative properties in thermal barrier coatings. Compared with spherical Shape, irregular anisotropic Pore Shape reduces the forward scattering peak. The method used in this paper can also be applied to other porous media, which designs a frame work for further quantitative study on porous media.