Preparation And Properties Of B₄C-based Composite With Layered Structure

Ceramic materials have excellent comprehensive properties including high strength, high hardness, high temperature anti-oxidation, small high-temperature creep, excellent wear resistance under high temperature, small thermal expansion coefficient, low density, and so on. Ceramic materials also have energy-absorbing effect, worn effect and kinetic effect, and they are conducive to playing a useful anti-missile capability. These properties that metallic materials, polymer materials and composite materials do not have make ceramic materials obtain a wide range of applications in armor protection. Ceramic materials have become one of the leading armor materials and played an irreplaceable role. Boron carbide ceramics have high hardness which is second only to diamond and cubic boron nitride, about30GPa and low density (2.52g/cm3), so that they have good application prospects in the military field. However, the low toughness of B4C ceramic materials seriously affects their ballistic performance. Therefore, how to improve the fracture toughness of boron carbide ceramic materials became the primary problem in the production of armored bulletproof materials. This paper shows that with the methods of layered composite structure design and adding a second phase particle, we can achieve the purpose of through increased toughness. By hot pressing process, we prepared B4C/B4C-Ti3SiC2, B4C/B4C-Ti2AlC, B4C/B4C-8%Si series, B4C/B4C-Si series and B4C/B4C-W2B5series two-layer composite ceramic materials, and studied their phase composition, microstructure, mechanical properties and reinforcement toughening mechanism in detail.The results showed that by hot pressing process that conducted first at1500℃holding for1h, then at1900℃for1h in vacuum with a pressure of30MPa, finally under the pressure with the furnace cooling for30min, we prepared high density, high performance and a good interface bonding B4C-based ceramics composite materials with layered structure. Based on the study of the mechanical properties of the two-layer composite ceramic materials, the experimental results were shown as follows. Among the B4C/B4C-Ti3SiC2, B4C/B4C-Ti2AlC and B4C/B4C-8%Si specimens, the B4C/B4C-8%Si composite ceramic materials showed the optimum properties and the ceramic layer hardness, toughness layer hardness, flexural strength and fracture toughness were31.1GPa,33.3GPa,524MPa and3.5MPa-m1/2, respectively. For the-Si series, the B4C/B4C-12%Si composite ceramic materials had the optimum comprehensive properties and the ceramic layer hardness, toughness layer hardness, flexural strength and fracture toughness were34.8GPa,35.2GPa,344MPa and4.6MPa-m1/2, respectively. For the B4C/B4C-W2B5layered composite materilas, the B4C/B4C-52%W2B5composite showed the optimum mechanical properties and the ceramic layer hardness, toughness layer hardness, flexural strength and fracture toughness were32.0GPa,3O.8GPa,418MPa and4.6MPa-m1/2, respectively.