Pressureless sintering preparation method of boron carbide composite material

Abstract

The invention discloses a pressureless sintering preparation method of a boron carbide composite material. Preparation raw materials comprise 83-94.9% of boron carbide, 1-6% of hafnium boride, 1-5% oftitanium dioxide, 0.1-6% of carbon, 2-20% of a binder, 0.5-5% of polyimide and 0.5-2% of a dispersing agent. The pressureless sintering preparation method comprises the following steps: ball milling,spray drying, sieving and drying, mixing, compression molding, biscuit vacuum sintering and the like. The boron carbide ceramic composite material is reasonable in compatibility; on the basis of boron carbide powder, a certain amount of hafnium boride and titanium dioxide are added as toughening phases, and optimized preparation process conditions are controlled, so that the prepared boron carbide composite material has the characteristics of high hardness, small specific gravity, high temperature resistance, good chemical stability, small thermal expansion coefficient, good thermal conductivity and the like, and meanwhile, the toughness is improved.

Description

technical field [0001] The invention relates to an inorganic composite material, in particular to a boron carbide composite material, and to a preparation method thereof. Background technique [0002] Due to its high hardness (second only to diamond and cubic boron nitride), boron carbide has a small specific gravity (2.52g / cm 3 ), high elastic modulus (450GPa), high temperature resistance, good chemical stability, small thermal expansion coefficient, good thermal conductivity and good neutron absorption capacity, etc., so in the mechanical seal industry, light bulletproof armor, hard grinding Materials, wear-resistant bearings, advanced refractory materials, aerospace, nuclear reactor shielding materials and many other fields have been widely used. However, since the covalent bond fraction of boron carbide is as high as 93.94%, it is higher than other structural ceramics, such as SiC (88%), SiN 4 (70%), etc., and therefore pure boron carbide is difficult to sinter and com...

AI Technical Summary

Problems solved by technology

However, since the covalent bond fraction of boron carbide is as high as 93.94%, it is higher than other structural ceramics, such as SiC (88%), SiN 4 (70%), etc., and therefore pure boron carbide is difficult to sinter and compact; simultaneously boron carbide is a brittle material with fracture toughness K IC ≤2.2MPa·m 1 / 2 , it is necessary to improve the mechanical properties of the material

In order to obtain dense B 4 C. Generally, it is produced by hot pressing sintering method. During the preparation, it is carried out in a vacuum hot pressing furnace or an ordinary hot pressing furnace. The hot pressing temperature is 2100°C and the pressure is 80-100 MPa. due to B 4 The thermal shock resistance of C is poor, so the cooling should be slow, and the hot pressing temperature should not be too high, and B will appear at 2150°C at 80-100MPa 4 C-C eutectic liquid phase, but the temperature is too low, the product density is low, the sintering process control conditions are strict, the preparation time is long, and due to the need for slow cooling, it is not suitable for the preparation of large-sized boron carbide ceramic composite materials

Pressureless sintering, also known as atmospheric pressure sintering, although boron carbide ceramic products with large size and complex shape can be prepared, but the density of boron carbide ceramics prepared by pressureless sintering is low at present, which leads to relatively low strength, hardness and toughness of ceramics. Poor, becoming a bottleneck restricting the application of boron carbide ceramics

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