Papers by Author: Shi Tian

Abstract: In this paper, the unidirectional SiC fiber-reinforced aluminum phosphates composites, in which the SiC fibers were heat-treated at different temperature, time and in different method, were prepared. The dielectric and mechanical properties of the composites were studied. The influences of heat treatment of SiC fiber on the properties of the SiC fiber-reinforced aluminum phosphates composite were investigated in detail. The flexural strength, relative dielectric constant and dielectric dissipation factor of the composite were measured. And the microstructure of the composite was characterized by SEM (scanning electronic microscope). The results show that heat treatment of SiC fiber has a great influence on mechanical and dielectric properties of the composite. The heat treatment decreases the dielectric constant and dielectric dissipation factor of the composite enormously. But at the same time, the heat treatment of the SiC fiber makes an unfavorably strongly bonded SiC fiber/aluminum phosphates matrix interface, which decreases the strength of the composite extraordinarily. And the composite displays a completely brittle failure behavior without fiber debonding and pulling out, which is detected by SEM.

Abstract: PbTiO3 nano-sized powders were synthesized at 150oC by a new hydrothermal [denoted as sol-hydrothermal] method by using modified titanium tetra-n-butoxide and lead acetate as the precursors. Furthermore, tetragonal PbTi0.8O2.6 nano-sized powders were obtained by this method at 80oC. Compared with hydrothermal synthesis, the effect of temperature on the formation of products prepared by sol-hydrothermal was investigated. The characteristics of products were studied by XRD, TEM and SAXS. The results show sol-hydrothermal method choosing acetylacetonate-modified titanium tetra-n-butoxide and lead acetate to form a sol could obtain PbTiO3 in 120nm size and PbTi0.8O2.6 powders with average diameter of 30nm, and both of them are pure tetragonal phase. In addition, PbTi0.8O2.6 could be converted into PbTiO3 gradually after annealed at giving condition.

Abstract: Reaction between nanometer γ-Al2O3 and H3PO4 to form AlPO4 by hydro-thermal method was studied. The microstructure of the reaction product was examined by SEM (scanning electronic microscope). The phase transformation of AlPO4 was investigated by DSC (differential scanning calorimeter) and XRD (X-ray Diffraction). The relative dielectric constant and dielectric dissipation factor of different kinds of aluminum phosphates were measured. Results of the study led to the optimal parameter of the reaction and showed that aluminum phosphate is a good matrix to make functional ceramic-matrix composites.