Zhang Jingxian

Deflocculants for tape casting of TiO2 slurries

Abstract Five dispersants, polycondensed fatty acid, castor oil, phosphate ester, polyvinyl butyral (B79), polyvinyl butyral (B98) are used as dispersant. The dispersability of TiO 2 slurries is studied through ESA measurement, rheological characterization and FTIR test. ESA measurement shows that the adsorption of PVB79 and phosphate ester is of physical and chemical type, respectively. Rheology, TG–DTA and sedimentation measurements show that in the absence of binder, PVB79 is the best dispersant; after the addition of binder, phosphate ester is the best one. The adsorption of dispersants on powder surface is also characterized by FTIR. The dispersion and stability mechanism is discussed.

Binary solvent mixture for tape casting of TiO2 sheets

Abstract Four azeotropic binary solvent mixtures based on ethanol/methyl ethyl ketone, ethanol/toluene, isopropanol/methyl ethyl ketone and isopropanol/toluene were studied for the dispersion of TiO2 powders. Two different polyvinyl butyral polymers (PVB79 and PVB98) were selected as dispersant and as binder and dibutyl phthalate (DBP) was used as plasticizer. The dispersability of TiO2 suspensions was characterized by rheological measurements and sedimentation tests. After tape casting, the properties of Green tapes were tested in term of density, surface roughness and strength. Results showed that azeotropic EtOH/MEK mixture is the effective solvent system for tape casting of TiO2 sheets. The TiO2 tapes served for multilayer ceramic/metal composite manufacturing.

Microstructure and Thermal Shock Resistance of ZrB 2 and ZrB 2 -20vol% SiC Composites from Aqueous Tape Casting: Microstructure and Thermal Shock Resistance of ZrB 2 and ZrB 2 -20vol% SiC Composites from Aqueous Tape Casting

The microstructure and thermal shock resistance of ZrB2 and ZrB2-20vol% SiC (ZS20) composites prepared by aqueous tape casting and hot-pressing were investigated. Zr-B-C and Zr-B-W solid solution phases were formed in ZS20 composites, but not formed in ZrB2 samples. The diffraction peaks for ZrB2 of ZS20 composites shifted to higher 2 theta values possibly due to the formation of solid solution phases which resulted in a decrease in lattice parameters. The critical thermal shock values for ZrB2 and ZS20 were measured to be 298 degrees C and 306 degrees C respectively using water quench tests. The thermal shock resistance of ZrB2 and ZS20 were also calculated and compared with the experimental data. The results revealed that the measured thermal shock resistance of ZS20 composites was lower than the calculated ones, which might be due to the thermal residual stress in the samples resulted from the difference in thermal expansion coefficient of ZrB2 matrix and SiC second phase as well as the solid solutions phases.