An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has be...An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.展开更多
The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated s...The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated suspensions exhibited Newtonian flow behaviors, while the fully-flocculated suspensions demonstrated very high viscosity and shear yield stress.展开更多
Comparison between filter pressing and isostatic pressing for submicrometer alumina powder has been systematically made. Obvious improvements in true porosity, sintering behaviour, and microstructure of green compacts...Comparison between filter pressing and isostatic pressing for submicrometer alumina powder has been systematically made. Obvious improvements in true porosity, sintering behaviour, and microstructure of green compacts without cracking and in agglomeration of final ceramics have been achieved.展开更多
Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K....Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K. An optimum level of Dispex A40 for full deflocculation is found to be at 0.18% mass fraction of the powder, at which the rheological behaviour shows little different to that of adjusting the pH to 4 to obtain full deflocculation. It is demonstrated that the shear stress drop can roughly work as an index for the thixotropy in particular fixed conditions, and consequently an index for the deflocculation as the shear stress drop becomes larger when the level of the flocculation increases, and vice versa. It is also found that the addition of Dispex A40 can prevent the filter cakes from cracking, whereas the cakes at various pH values with polyvinyl alcohol as a sole polymer normally develop cracking during drying.展开更多
The pH dependence of the extrapolated shear yield stress for Alcoa A16 a-Al2O3 suspensions at the powder volume fraction of 0.27 with and without addition of both polyvinyl alcohol (PVA) and polyethylene glycol (PEG) ...The pH dependence of the extrapolated shear yield stress for Alcoa A16 a-Al2O3 suspensions at the powder volume fraction of 0.27 with and without addition of both polyvinyl alcohol (PVA) and polyethylene glycol (PEG) each at fixed 0.18% of the powder mass was studied. With the polymer added, the full deflocculation of the suspension shifts from about pH=4 to around pH=1.5, at which the minimum value of shear yield stress is higher than that at pH=4. The addition of both PVA and PEG was found to prevent the filter cake from cracking.展开更多
文摘An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
基金Partly supported by Scientific Research Foundation for Returned Overseas Scholars from State Education Committee of China
文摘The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated suspensions exhibited Newtonian flow behaviors, while the fully-flocculated suspensions demonstrated very high viscosity and shear yield stress.
文摘Comparison between filter pressing and isostatic pressing for submicrometer alumina powder has been systematically made. Obvious improvements in true porosity, sintering behaviour, and microstructure of green compacts without cracking and in agglomeration of final ceramics have been achieved.
文摘Variation of plastic viscosity and extrapolated shear yield stress with the concentration of Dispex A40 for the concentrated Alcoa A16 alpha -Al2O3 suspensions at 0.27 powder volume fraction was investigated at 294 K. An optimum level of Dispex A40 for full deflocculation is found to be at 0.18% mass fraction of the powder, at which the rheological behaviour shows little different to that of adjusting the pH to 4 to obtain full deflocculation. It is demonstrated that the shear stress drop can roughly work as an index for the thixotropy in particular fixed conditions, and consequently an index for the deflocculation as the shear stress drop becomes larger when the level of the flocculation increases, and vice versa. It is also found that the addition of Dispex A40 can prevent the filter cakes from cracking, whereas the cakes at various pH values with polyvinyl alcohol as a sole polymer normally develop cracking during drying.
文摘The pH dependence of the extrapolated shear yield stress for Alcoa A16 a-Al2O3 suspensions at the powder volume fraction of 0.27 with and without addition of both polyvinyl alcohol (PVA) and polyethylene glycol (PEG) each at fixed 0.18% of the powder mass was studied. With the polymer added, the full deflocculation of the suspension shifts from about pH=4 to around pH=1.5, at which the minimum value of shear yield stress is higher than that at pH=4. The addition of both PVA and PEG was found to prevent the filter cake from cracking.