Jingguo Li

Mechanical properties and electrical conductivity of TiN–Al2O3 nanocomposites

Abstract TiN–Al2O3 nanocomposites with various additions of TiN were prepared by hot pressing of nano TiN–Al2O3 powder that was produced by in-situ nitridation of nano TiO2–Al2O3 powder. TiO2–Al2O3 powder mixtures are prepared by a heterogeneous precipitation method. The effects of nano TiN particles on the mechanical properties and electrical conductivity of TiN–Al2O3 nanocomposites were studied. Experimental results show that the addition of 20 vol.% TiN could increase the bending strength of hot-pressed Al2O3 from 370 to 725 MPa and the fracture toughness from 3.40 to 5.27 MPa m1/2, respectively. The resistivity of nanocomposites decreases with increasing amount of TiN and reaches to a minimum value of 5.5×10−3 Ω cm for the nanocomposite with 25 vol.% TiN.

Preparation of ultrafine InN powder by the nitridation of In2O3 or In(OH)3 and its thermal stability

Crystalline InN powder has been prepared by the nitridation of In2O3 and In(OH)3 with NH3 gas for the first time, and ultrafine InN powder in the size range 50–300 nm and with a specific surface area of 8 m2 g−1 has been obtained using In2O3 nanoparticles as the starting material. The resulting powders were characterized by XRD, FE-SEM, TEM, TG-DSC and BET surface area techniques. It was found that nanosized In2O3 was completely converted into InN at 600 °C within 8 h. The thermal stability of the ultrafine InN powder in air and under a nitrogen atmosphere was also investigated. It was observed that InN began to be oxidized into In2O3 at 389 °C and decomposed in the narrow temperature range of 595–696 °C in flows of air and N2, respectively.

The influence of the preparation method on the microstructure and properties of Al2O3/TiN nanocomposites

Abstract Al2O3/TiN nanocomposites were fabricated by hot pressing of powders prepared through ball milling (BM) and in-situ nitridation (PN) methods, respectively. And the mechanical and electrical properties as well as microstructure of the nanocomposites were studied. It was found that TiN showed a strong reinforcing effect in both materials. Due to the difference in the powder preparation method, the Al2O3/TiN nanocomposite from PN powder showed a finer TiN particle size and a more uniform microstructure than the nanocomposite from BM powder. As a result, the former material showed a superior electrical conducting behavior and better mechanical properties.