Showing 3 results for Gel Casting
N. Miadi, H. Sarpoolaky, H. Ghassai,
Volume 32, Issue 1 (6-2013)
Abstract
In this study, mullite– irconia composite samples were prepared by reaction sintering of alumina and zircon powder via gel casting process. Gel casting is a new ceramic forming technique. This process is based on the casting of slurry, containing ceramic powder, dispersant and premix monomer solution. To achieve stabilized, high solid loading (80 wt%) and castable slurry, the rheological properties of slurry were optimized. The monomers polymerized the slurry to form gelled specimens. After gelation, the specimens were unmolded, then dried out under controlled condition. Burning out and sintering of the specimens was carried out in the range of 1400-1700°C. Apparent porosity and bulk density of the sintered samples were measured by soaking in water. Crystalline phase evolution and microstructure were determined by XRD and SEM techniques. Results showed that the reaction sintering and mullite formation was completed at 1700°C due to very slow diffusion of Al3+ ions within amorphous silica formed at the decomposition of zircon. The sintered samples at this temperature also showed the lowest apparent porosity (≈ 4%) and the highest bulk density (≈3.40 gr/cm-3).
L. Akbarshahi, H. Sarpoolaki, H. Ghassai,
Volume 33, Issue 1 (7-2014)
Abstract
In this research according to unique properties of fused silica and Its numerous applications fused silica parts with 77% by weight solid loading formed by gel casting. Rheological behavior of the slurry and sintering conditions were optimized. Sample sintered at optimum conditions has bulk density of 1.71 g/cm3, open porosity of 18.13%, water absorption of 10.60%, linear shrinkage after firing of 3.5%, closed porosity of 1.09% and relative density of 78.80%. Its thermal expansion coefficient in range of room temperature to 1000 ◦C has been measured 0.4432×10-6 1/ . Results showed that With increasing temperature and time In addition to the increased vscous flow, Crystallization also extend. Finally sintered at high temperature and short time for an instance with the lowest overall high crystallinity and density, were found suitable
M. Haghshenas Gorgani, M. Mirkazemi, F. Golestanifard,
Volume 37, Issue 4 (3-2019)
Abstract
In this research, the rheological behavior and stability of suspensions containing Si3N4, Al2O3, Y2O3 and starch were investigated in order to use them in the starch consolidation casting of porous silicon nitride. Dolapix CE64 was used as the dispersant. Then, the effect of some parameters such as Si3N4 surface oxidation, dispersant content, solid loading and starch content on the viscosity and rheological behavior of Si3N4-starch slurry was determined. Surface oxidation of Si3N4 powder at 800°C for 2 hours reduced the viscosity of the slurry, effectively. The best dispersant content was 0.4 wt. %, relative to ceramic powders. Slurries containing 30 to 40 vol. % and 7.5 to 25 vol. % starch, relative to total solid loading, had the suitable viscosity and the sufficient stability for casting by the starch consolidation method.
