• Journal of the Korean Society for Heat Treatment
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• v.10 no.2
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• pp.138-149
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• 1997

TiN and AlN are ceramic materials with extensive applications due to its excellent mechanical and chemical properties at elevated temperature. The purpose of this research is to develop the method for the synthesis of ternary nitride powder, titanium-aluminum-nitrogen system, which have an excellent property of both TiN and AlN. The ternary nitride such as $Ti_3AlN$, $Ti_2AlN$ and $Ti_3Al_2N_2$ can be synthesized by the interdiffusion nitriding method in Ar gas, however, the ternary nitride coexist with TiN, AlN, $Ti_3Al$ and ${\alpha}$-Ti. The ternary nitride are stable below $1400^{\circ}C$, but these are gradually decomposed into TiN, $Ti_3Al$ and AlN above $1400^{\circ}C$. The thermal oxidation characteristics of the Ti-Al-N compound synthesized by the interdiffusion nitriding method is superior to that of the TiN+AlN mixed powder, and the oxidation for both materials show the differential behaviors.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.386-391
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• 2014

Silicon nitride ($Si_3N_4$) is regarded as one of the most promising materials for high temperature structural applications due to its excellent mechanical properties at both room and elevated temperatures. However, one high-temperature $Si_3N_4$ material intended for use in radomes has a relatively high dielectric constant of 7.9 - 8.2 at 8 - 10 GHz. In order to reduce the dielectric constant of the $Si_3N_4$, an in-situ reaction process was used to fabricate $Si_3N_4-SiO_2$-BN composites. In the present study, an in-situ reaction between $B_2O_3$ and $Si_3N_4$, with or without addition of BN in the starting powder mixture, was used to form the composite. The in-situ reaction process resulted in the uniform distribution of the constituents making up the composite ceramic, and resulted in good flexural strength and dielectric constant. The composite was produced by pressure-less sintering and hot-pressing at $1650^{\circ}C$ in a nitrogen atmosphere. Microstructure, flexural strength, and dielectric properties of the composites were evaluated with respect to their compositions and sintering processes. The highest flexural strength (193 MPa) and lowest dielectric constant (5.4) was obtained for the hot-pressed composites. The strength of these $Si_3N_4-SiO_2$-BN composites decreased with increasing BN content.