Preparations And Properties Of High Performance Boron Carbide Ceramics

Boron carbide?B₄C?ceramic is one of the special ceramics with the greatest potential.It is widely used in military,nuclear and other fields because of its low density,high hardness,low expansion coefficient,high chemical inertness,low dielectric constant and other excellent properties.However,further application of boron carbide is restricted due to its large brittleness and difficulty of sintering densely.In order to solve these problems,reaction sintering and hot pressing were presented in this paper to prepare boron carbide composite.The effects of different Carbon coated dispersion processes and the content of silicon carbide fiber?SiC_f?on microstructure and properties of the composites were studied.The influences of addition graphene oxide?GO?on the microstructure and the properties of the composites were mainly investigated in hot press sintering.Conclusions are as follow:?1?Usually,phenolic resin is as carbon source.C-coated boron carbide powder can be obtained by ultrasonic dispersion process during mechanical stirring.B₄C composite material can be prepared by sintering reaction that phase composition involves B₄C,SiC,Si and B₁₂?C,Si,B?₃.The B₄C phase in the microstructure of the material is more evenly dispersed.The Rockwell hardness and flexural strength of the material can reach 89HRA and 313MPa respectively.The mechanical properties of the composites are better than that of mechanical agitation-increased by 4.5%and 32%.?2?B₄C composites were prepared by sintering reaction as reinforcing phase of SiC_f.The results show that B₄C,SiC,Si and B₁₂?C,Si,B?₃are phase composite components.Open porosity rate of the composites B₄C increases with SiC_f.The hardness decreases with the increase of SiC_f.The bending strength increases first and then decreases with the increase of SiC_f.When SiC_f is added in an amount of 8wt%,the flexural strength reaches 378MPa.?3?B₄C composites were prepared by hot sintering reaction as reinforcing phase of graphene oxide.The results show that B₄C and graphene oxide are phase composite components.Open porosity rate of the composites B₄C increases with the increase of graphene oxide,and the hardness decreases with the increase of graphene oxide.The flexural strength increases first and then decreases with the increase of graphene oxide.When the content of graphene oxide is low,graphene oxide of composite can be uniformly dispersed in boron carbide.When the amount of graphene oxide addition is 1wt%,the flexural strength of the material reaches the maximum of 479MPa.