Abstract: Monolithic B₄C ceramics were prepared by hot-pressing using three types of B4C powders with average particle of 3.5 μm, 1.5 μm and 200 nm, respectively. The effect of particle size on densification and microstructure of sintered ceramics was studied. The activation energy difference of the starting powders in the initial sintering stage was obtained in terms of dwelling time as a function of linear shrinkage and plastic deformation mechanism. The result shows that at the same process, the diffusion activation energy and densification initial temperature of the powders decrease with the mean particle size decreasing, and the time of plastic flow in the initial sintering stage is also shortened markedly, while the relative density and densification rate are higher. The microstructure and mechanical properties of sinterd samples are also improved with mean particle size decreasing. The relative density of 90.5% and hardness of (17±1.8) GPa are achieved for the B4C ceramics sintered from the powders with mean particle size of 200 nm for 1 h at 1850℃.

Key words: boron carbide, densification, hot pressing, mechanical property