Combustion Synthesis of TiN-BN Nanostructured Composite Powder with the Use of Sodium Azide and Precursors of Titanium and Boron

Abstract

The composite powder of TiN-BN is of interest from the point of view of the use for sintering the TiN-BN composite ceramics, which compared with TiN ceramics would have less britlleness, better machinability and good tribological properties. Possibility of obtaining a composite powder of TiN-BN with the application of process of combustion synthesis (CS) or self-propagating high-temperature synthesis (SHS) from powder mixtures of sodium azide and halide salts KBF 4 , NH 4 BF 4 , (NH 4 ) 2 TiF 6 and Na 2 TiF 6 as precursors of titanium and boron was investigated. It was shown that these mixtures are capable of burning and obtaining agglomerated composite powders. TiN-BN powder with an admixture of KF is formed only in combustion of "KBF 4 -NaN 3 -Na 2 TiF 6 " system with the increased content of halide salt of boron KBF 4 . In all other cases, the synthesized product has other composition: TiN-BN-TiB, TiN-TiB, TiN, often with an admixture of salts KF, NaF, Na 3 TiF 6 as by-products. Agglomerated composite powders as TiN-BN and others consist of nano-sized (less than 100 nm) and ultra-dispersed (100-500 nm) particles. The size of the agglomerates is in the range from 10-30 microns to 100-200 microns.