Effect of BN addition on mechanical and electrical properties of oxidative sintered porous Si3N4-BN composites
Hong Lin, Hong Lin, Guoqing Feng, Hongyu Wang, Haiyi Peng, Liangliang Cao, Huixing Lin, Huixing Lin, Hongtao Li, Fancheng Meng
Abstract
In order to explore the effects of BN addition on the mechanical and electrical properties of oxidative sintered Si 3 N 4 -BN composites, Si 3 N 4 -BN composites with BN powder dosage of 0-40 wt% are prepared by molding technology, and the effects of different BN contents on the phase, morphology, bulk density, porosity, flexural strength at room temperature, dielectric constant and dielectr loss of the composite system are studied. With the increase of BN content, at different temperatures, the oxidation product B 2 O 3 of BN and the oxidation product SiO 2 of Si 3 N 4 firstly react on the surface to form B 2 O 3 –SiO 2 glass phase, which densify the surface and affects the oxidation degree of internal grains. At the same time, a small amount of B 2 O 3 escaping from the surface, so that the open pores of the composites decrease firstly and then increase slightly, and the dielectric constant increases firstly and then decreases. The results show that when the amount of BN micronized powder is 10 wt%, the oxidation sintered Si 3 N 4 -BN composite material at 1500 °C have pores that retain the sheet structure of boron nitride , and the amorphous material flows to fill the pores, so it have high volume density (1.85 g/cm 3 ), low porosity (apparent porosity 6.37%), and high mechanical properties (flexural strength 127.86Mpa), higher dielectric constant (3.94) and lower dielectr loss (4.0 × 10 −4 ).