A boron carbide vest is a bullet proof armor made of strong and light ceramic material. Its main function is to shatters the bullet upon impact, so that the energy from the impact can be dissipated within the armor system.
Boron carbide is one of the strongest and most lightweight known ceramic materials, making it the ideal choice for body armors. Moreover, boron carbide is chemically inert and is able to resist corrosion in the harshest environments.
A method for producing a reaction-bonded boron carbide (RBC) composite material is disclosed in U.S. Patent 3,796,564. This method is essentially a form of reactive infiltration, wherein a molten silicon infiltrant, containing both boron and silicon, is contacted to a porous mass or preform containing a blend of boron carbide particulate and free carbon.
The molten infiltrant is heated to a temperature above the boron carbide and free carbon to infiltrate into the porous mass or preform without pressure or vacuum assistance, forming a composite body of near theoretical density with some residual unreacted infiltrant phase. The molten silicon reacts with some or all of the boron carbide in the porous mass or preform to produce a composite body that is a refractory metal (e.g., boron carbide) reinforced with a matrix phase of silicon carbide.
However, if the silicon carbide matrix phase is too large or coarsely grained, it can cause excessive boron carbide reaction to occur, which can decrease the strength of the resulting body. This may be undesirable in certain applications, such as armor. Alternatively, if the boron carbide grains are smaller or finer, it may be possible to suppress the boron carbide reaction. This allows a relatively fine-grained microstructure to be maintained in the resultant RBBC, which is desirable for a variety of precision equipment applications.