Study On Preparation And Sintering Mechanism Of Boron Carbide Ceramics By Oscillating Pressure Sintering

Boron carbide is a strategic material with lower density and lower coefficient of linear thermal expansion,at the same time,it has extremely high hardness and high elastic modulus that can be ranked in the top three,which makes it a candidate for excellent structural ceramics.Boron carbide also has a series of excellent properties such as high melting point,good thermal stability,strong resistance to chemical erosion and neutron absorption.The fields of blasting nozzles,neutron absorption and radiation protection materials have broad application prospects.However,due to the high covalent bond content,high melting point,low diffusion coefficient and high vapor pressure between boron carbide atoms,it is very difficult to densify,which seriously affects the application of boron carbide ceramics in real society.Therefore,the densification behavior of boron carbide ceramics was systematically studied for this status quo.This paper uses 2-3μm boron carbide powder as raw material to prepare boron carbide ceramics by hot oscillatory pressing technology.Hot oscillatory pressing is based on hot pressing to make static pressure into dynamic pressure of oscillating change.Compared with hot pressing sintering,hot oscillatory pressing can obtain higher density,smaller grain size and more uniform structure,so as to obtain a significant improvement in mechanical properties.Therefore,in this paper,boron carbide ceramics are prepared from sintering temperature and sintering pressure by hot oscillatory pressing sintering technology and hot pressing sintering technology.Analysis of microstructure,density and mechanical properties of sintered samples.At the same time,the densification kinetics and densification mechanism of hot oscillatory pressing sintering technology were explored.The results show that in the experiments at different sintering temperatures,hot oscillatory pressing can prepare fully dense boron carbide ceramics at a lower temperature than the hot pressing sintering technology,and has better mechanical properties.The densification process of boron carbide ceramics sintered by external oscillatory force field and static force field was comparatively studied.Compared with the static force field,the boron carbide ceramics had a higher densification rate under the oscillatory force field.Therefore,the densification mechanism at different sintering temperatures was further analyzed,and the results showed that the densification process of hot oscillatory pressing sintering technology is dominated by dislocation slip plastic deformation.In the experiments of different sintering pressures,the results show that the 1750°C oscillatory sintering stress index is 11/2,and a flexural strength of 689±57MPa.