Self-Propagation High Temperature Synthesis Of TiB₂ And TiB₂-Al₂O₃ Composite In Air Atmosphere

Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 and TiB2-Al2O3 powders from B2O3-TiO2-Mg and B2O3-TiO2-Al systems respectively in air atmosphere. The physical -chemical process of the combustion synthesis and the effect of diluence on the reduction process and characteristic of ceramic powder products were studied.The results of analysis of different thermal analysis (DSC-TG) indicated that the chemical process of B2O3-TiO2-Mg system in air atmosphere is similar to that of reacted in argon atmosphere. The adiabatic temperature and combustion temperature decreased while particle size and half width of particle distribution of TiB2 powder product increased with the diluence (TiB2) addition ranging from 0wt% to 20wt%.The XRD patterns indicated that the TiB2 powder product was a mixture of TiB2 and a little TiO2 and TiN2-SEM of the product illustrated that fine TiB2 powder can obtained by SHS with reduction process in air atmosphere.The chemical process of B2O3-TiO2-Al system in air atmosphere was also similar to that of reacted in argon atmosphere. The adiabatic temperature and combustion temperature decreased with increasing of the diluence (TiB2 or Al2O3) addition. The XRD patterns indicated that the product as combusted was a mixture of TiB2 and Al2O3.Based on SHS TiB2-Al2O3 powder, dense TiB2-Al2O3 composites were obtained by hot-pressing .The sintering were carried out at same temperature and microstructure of the samples were studied by SEM .The hardness, relative density and bending strength (3 pt) of the sample changed with the variations of the composition.The mechanical properties of TiB2-Al2O3 composites increased with the content of TiB2, but decreased when the mole ratio of TiB2: A12O3 was more than 49.31: 50.69. SEM analysis indicated that evenly distributed fine crystal grain was the reason of good bending strength. Optimize sintering parameter, like sintering temperature, pressure and heating time, would increase the mechanical propertiesof the material.