The pressureless sintering of pure boron carbide is difficult to densify. The main factors affecting the density of boron carbide ceramics are sintering temperature and powder particle size. Sintered at 2300 ° C under normal pressure, the relative density of its products is generally lower than 80%, and it is prone to abnormal grain growth and surface melting. Increasing the specific surface area of boron carbide powder and reducing its average particle size can increase the sintered density to a certain extent. Therefore, in order to reduce the sintering temperature and improve the overall performance of boron carbide products, it is generally necessary to add sintering aids, such as elemental boron, carbon, aluminum, etc., to promote the sintering of boron carbide.
Spark plasma sintering (SPS)
Spark plasma sintering (SPS), which has been developed in recent years, is a new rapid sintering process that can achieve fast and efficient sintering of materials at low temperatures. In the SPS sintering process, the discharge plasma generated instantly when the electrode is fed with a pulsed direct current, so that each particle in the sintering system uniformly generates Joule heat to activate the particle surface. SPS can effectively use the self-heating inside the powder, and the dispersion of the discharge points can achieve uniform heating. In addition, SPS can achieve effective discharge between particles to cause local high temperature, local melting of the particle surface, and peeling of the surface oxide film. Using this new sintering technology can achieve high-density sintering of boron carbide ceramics without sintering aids, and the product structure is uniform and the chemical composition is controllable.