The mechanism of combustion synthesis of (TiCxNy-TiB2)/Ni from a Ni-Ti-C-BN system

The combustion reaction mechanism of the Ni-Ti-C-BN system was investigated by a combustion front quenching method. The results showed that the SHS reaction in the Ni-Ti-C-BN system starts with the formation of TiNx and TiB from the solid-state reaction between Ti and BN. Meanwhile, the solid-state reaction between Ni and Ti occurs at some locations to form Ni3Ti. Subsequently, the resultant TiNx reacts with Ni to form the Ni-Ti compounds such as NiTi and Ni3Ti. As the temperature increases further, Ni-Ti liquid appears between NiTi and Ni3Ti, and some B atoms that diffused away from BN could dissolve into the Ni-Ti liquid to form TiB2. The heat generated from these reactions promotes the further dissolution of the C, B and N atoms in the Ni-Ti liquid to form the Ni-Ti-B-N-C liquid. As the B, N and C atoms in the liquid become sufficiently supersaturated, precipitation of plenty of TiB2 and TiCxNy grains occurs. In addition, the reasons for the prior formation of TiB2 over TiCxNy and separated residence of the TiB2 and TiCxNy grains in the microstructure were discussed.

Graphical AbstractIn this work, the combustion reaction mechanism of the Ni-Ti-C-BN system was investigated by a combustion front quenching method. The results showed that the ceramic phases of TiCxNy and TiB2 were formed through the dissolution–reaction–precipitation mechanism.Figure optionsDownload as PowerPoint slide