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Properties and characteristics of SIC and Alumina Ceramic armor plate

Time:2022-10-27     Author:KINGCERA(Translated by Echo Huang)    Reader:

As we all know, bulletproof ceramic plays an essential role in defence field. Compared to traditional bulletproof metals, it has many advantages such as high compressive strength, high KIC, high hardness and wear resistance. At present, the most popular bulletproof ceramics are SIC (silicon carbide) ceramics and high Al₂O₃(alumina) ceramics. 

1. Characteristics of regular bulletproof materials

Mental: the production process is simple but with high density, which means the weight is heavy and might affect using effect. When the metal resists the impact of the warhead, it will form plastic deformation and absorb energy, so the bulletproof effect is not ideal. 
Ceramic: bulletproof ceramics are mainly divided into three categories:
a. oxide ceramics (mainly alumina ceramics),
b. non-oxide ceramics (such as silicon carbide ceramics, boron carbide ceramics, silicon nitride ceramics, aluminum nitride ceramics) 
c. binary systems (such as B4C-TIB2-based ceramics) 
Among all, non-oxide ceramics have higher physical properties and lower density (except TIB2-based ceramics), but the manufacturing method is mainly hot pressing technology, which costs more and is difficult to industrialize production. Luckily, SIC and Al₂O₃are good choices for us because of their high performance-cost ratio.
Bulletproof ceramic produced by KINGCERA
Bulletproof ceramic produced by KINGCERA

2.Performance requirements of ceramic armor plate

Bulletproof ceramics are fragile and easy to crack in a very short time, which is caused by many factors. Therefore, the performance requirements for bulletproof ceramics are complex, such as density, porosity, hardness, fracture toughness, elastic modulus, sound speed, mechanical strength, etc.
Armor plate produced by KINGCERA

Alumina ceramic body armor plates produced by KINGCERA


3.Composite methods and bulletproof principle of armor plate

Regular composite methods: ceramics tile/ monolithic ceramic insert + back plate (PE/Aramid)
Bulletproof principle: when resisting the impact of the warhead, ceramic armor plate will hardly produce plastic deformation, and its high strength and high hardness can dissipate or even break the warhead. The energy of the high-velocity warhead is absorbed during the blocking process. 
Today, let’s talk about the popular armor plates - SIC and Al₂O₃.

4.Al₂O₃ armor plate

The bulletproof alumina ceramic is made of industrialized ultrafine alumina powder, and the alumina oxide powder should be transformed into α-Al₂O₃ with a more stable crystal structure and chemical properties. The purity of α-Al₂O₃ should be more than 95%. The purity of 99 alumina ceramic in KINGCERA is more than 99%. 
When the purity exceeds 95%, the main crystal phase of Al₂O₃ is corundum. With the increase of Al₂O₃ content, the corundum content also increases accordingly. The final ceramic grain size depends on the particle size and distribution of the original Al₂O₃ powder. Since the Al₂O₃ powder has a smaller size, the sintered ceramic has a fine microstructure, 2-4 μm and 1-3 μm. The ceramic does not contain glass phase, and then adds a certain proportion of zirconia, and the ZrO₂ grains smaller than 1 μm are evenly distributed among the corundum crystals of 1 to 2 μm. It is possible that the ZrO₂ phase prevents the growth of corundum crystals during sintering and forms a good microstructure.
The porosity of bulletproof alumina ceramics should be as low as possible to improve hardness and elastic modulus. Its porosity is close to zero, and its water absorption does not exceed 0.02%. The hardness of the bulletproof ceramic is very high, which should be higher than that of the flying warhead. For Al₂O₃ ceramics, the hardness can reach HRA88 or more, which fully meets the conditions. The speed at which sound travels in a ceramic indicates the ability of the ceramic to dissipate energy on the impact surface. Therefore, the bulletproof ceramic should have a high speed of sound, which also indirectly means that the ceramic has good densification and low closed pores. The sound speed of Al₂O₃ porcelain can reach 10500-11500m/s, which has obvious advantages compared with other bulletproof ceramics.
99 alumina ceramic produced by KINGCERA
99 alumina ceramic produced by KINGCERA

5.SIC armor plate

SIC is a covalent compound dominated by covalent bonds. The basic unit is a tetrahedron when carbon and silicon form a SIC crystal by stacking SIC tetrahedra. The hardness is higher than corundum and ranks among the top ordinary abrasives, second only to several super hard materials. The Mohs notch hardness is 92, and the Kjeldahl microhardness is 2200~2800kg/mm (load 100g). Although the thermal hardness of silicon carbide decreases with the increase in temperature, it is still much higher than that of corundum.
SIC ceramic produced by KINGCERA
SIC ceramic produced by KINGCERA

6.Performance index of KINGCERA’s SIC and 99 Al₂O₃ ceramic

As a professional manufacturer of special ceramics, KINGCERA has nearly 30 years of experience in R&D and production of ceramics.
The bulletproof 99 alumina ceramic produced by KINGCERA has alumina purity ≥99%, hardness ≥HRA88, density ≥3.9g/cm³, bending strength >350MPA, impact toughness ≥2.2 J/cm², elasticity modulus >317GPA. KINGCERA’s 99 Al₂O₃ ceramic is NIJ 0101.06 qualified for level III and Level IV standards. 
The bulletproof SIC ceramic produced by KINGCERA has silicon carbide purity ≥98%, density ≥3.1g/cm³, hardness ≥ HRA92, and bending strength >400MPA, which is NIJ 0101.06 qualified for Level IV standards. With our design and mould-making team, we can produce various ceramic shapes and thicknesses. 

KINGCERA is a globally direct bulletproof ceramic manufacturer
KINGCERA is a globally direct bulletproof ceramic manufacturer

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