How much do you know about ballistic silicon carbide?
We can usually see such a scene in movies: a gunfight erupts, bullets fly, and the protagonist is attacked by a bullet on the chest, but predictably, he regains consciousness and opens his jacket to reveal an intact bulletproof vest with a shiny bullet perfectly mushroomed from impact. Do such bulletproof vests really exist in real life, or only in movies?
Bulletproof vests and hard armor plates have become standard equipment for law enforcement and military. However, soft body armor has a low protection level and can only resist the attack of low-speed bullets, high-speed bullets can only be resisted with the help of hard armor plates which are usually inserted into soft vests to provide additional protection. Compared with soft body armor, hard protective inserts are much heavier, but ordinary ceramic composite plates can all meet people’s requirements for weight, performance and price. At present, there are many kinds of bulletproof ceramics, among which the silicon carbide has always been regarded as the ideal material for making bulletproof equipment based on its high strength and lighter weight. Silicon carbide (SIC) has two main crystal structures, cubic β-SIC and hexagonal α-SIC. Silicon carbide is a compound with strong covalent bond, and the ionic bond of Si-C is only about 12%, which bring SIC many benefits, such as better mechanical properties, great oxidation resistance, good wear resistance and low friction coefficient. In addition, it also has good thermal stability, high hot strength, low thermal expansivity, high thermal conductivity, great thermal shock resistance and chemical corrosion resistance, etc. All those make SIC preferred by military experts of different countries and has gain a great application in many fields. However, SIC has also a fatal defect---the molecular structure determines its low toughness. When the impact occurs, with the super-high strength SIC can absolutely resist the huge kinetic energy of the bullet and instantly smash the bullet into pieces, during which due to the low toughness, SIC cracks or even fragments. Therefore, SIC plates cannot withstand repeated shootings, and can only be used as disposable plates. However, according to many researchers in the field of material molecule, the low toughness of SIC can be theoretically compensated and overcome by controlling the sintering process and the preparation of ceramic fibers. Once realized, it will greatly improve the application of SIC in the bulletproof field, making it the most ideal material for manufacturing bulletproof equipment.