Papers by Author: Yong Fei Gu

Abstract: Aluminum nitride (AlN) is a stoichiometric compound with the hexagonal wurtzite structure. AlN has excellent thermal conductivity and good properties as electronic insulator. It displays good mechanical resistance up to elevated temperatures and is resistant against corrosion by molten metals. Bulk AlN may therefore be used as a refractory structural material as well as a substrate for high power microelectronic devices. However, it is very difficult for sintering high-density AlN at lower temperature than 1800°C. Nano-sized AlN powders were sintered by hot press sintering at low temperature of 1500~1700°C and mechanical properties were investigated. β-AlN and β-Al2O3 were detected when the sintering temperature is 1600°C. The phase transition β-AlN to α-AlN was discovered at a 1700°C sintering temperature. Relative density and average grain size were increasing with the increasing of sintering temperature, and fracture form is intercrystalline crack in 1500°C and transcrystalline crack in 1700°C. 97.3% relative density and 850nm average grain size were deserved at 1700°C.

Abstract: Y2O3 nano-phase powders were prepared by polyacrylamide gel method. The mechanism of polyacrylamide gel process and its calcinations procedure were analyzed. The high purity yttria powders can be produced by polyacrylamide gel method at the calcination temperature of 850°C, which is about 100°C lower than prepared by precipitation method. The microstructure of yttria powders prepared in different proportion of monomer and network agent was investigated. When the mole proportion of monomer and network agent is 5:1, the average size of grains is less than 20nm. Some grains grow abnormally if the proportion deviate from this value and there are a lot agglomerates. Development of such an inexpensive and easy technique for synthesis of high purity yttria nano-phase powders can be of commercial significance.