Ceramic Materials: The Leading Lights in Ballistic Defense

In the collective perception, Ceramics Are considered fragile items. However, after processing with modern technology, ceramics have undergone a remarkable transformation into a hard and high-strength new material. This is particularly evident in the field of ballistic protection, where ceramics have shone brightly, becoming a highly sought-after material for bulletproof applications.

Part Ⅰ：The Bulletproof Principle of Ceramic Materials

The fundamental principle of armored protection is to dissipate the energy of projectiles, reduce tThe energy absorption process of ballistic ceramics can be roughly divided into three stages: (1) Initial impact stage: The projectile strikes the surface of the ceramic, bluntly deforming the projectile and absorbing energy while creating a fine and hard fragment area through the fracturing of the ceramic surface; (2) Erosion stage: The blunt projectile continues to erode the fragment area, forming a continuous layer of ceramic fragments; (3) Deformation, cracking, and fracture stage: Finally, tensile stress is generated within the ceramic, causing it to shatter, and subsequently, the backing material deforms, absorbing all remaining energy through its deformation. During the impact of the projectile against the ceramic, both the projectile and the ceramic experience damage.ation, while ceramic materials absorb energy through a micro-cracking process.

The energy absorption process of ballistic ceramics can be roughly divided into three stages:

(1) Initial impact stage: The projectile strikes the surface of the ceramic, bluntly deforming the projectile and absorbing energy while creating a fine and hard fragment area through the fracturing of the ceramic surface;

(2) Erosion stage: The blunt projectile continues to erode the fragment area, forming a continuous layer of ceramic fragments;

(3) Deformation, cracking, and fracture stage: Finally, tensile stress is generated within the ceramic, causing it to shatter, and subsequently, the backing material deforms, absorbing all remaining energy through its deformation. During the impact of the projectile against the ceramic, both the projectile and the ceramic experience damage.

Part Ⅱ：Requirements for Material Properties of Bulletproof Ceramics
Due to the inherent brittleness of ceramics, they tend to fracture under projectile impact rather than undergo plastic deformation. Under tensile loading, fractures primarily initiate at inhomogeneous sites such as pores and grain boundaries. Therefore, to minimize microscopic stress concentration, armor ceramics should be of high quality, with low porosity (achieving 99% of theoretical density) and a fine-grained structure.

Part Ⅲ：The most commonly used ballistic ceramic materials

Since the 21st century, the development of ballistic ceramics has been rapid, with various types including alumina, silicon carbide, boron carbide, Silicon Nitride, and titanium boride. Among these,alumina ceramics (Al₂O₃), silicon carbide ceramics (SiC), and boron carbide ceramics (B₄C) have the most extensive applications. Alumina ceramics have the highest density; however, they have relatively lower hardness, a lower processing threshold, and are more affordable. They are categorized based on purity into 85/90/95/99 alumina ceramics, with corresponding increases in hardness and price.

Silicon carbide ceramics have a relatively low density and high hardness, making them high-performance structural ceramics. Therefore, they are currently the most widely used ballistic ceramics domestically. Boron carbide ceramics have the lowest density and the highest hardness among these ceramics, but they also have stringent requirements for processing techniques, necessitating high-temperature and high-pressure sintering, which results in the highest cost among the three types of ceramics.

Comparing these three commonly used ballistic ceramic materials, alumina ballistic ceramics have the lowest cost but their ballistic performance is far inferior to that of silicon carbide and boron carbide. Therefore, among the domestic production units of ballistic ceramics, silicon carbide and boron carbide are predominantly used, while alumina ceramics are quite rare. However, single crystal alumina can be used to prepare transparent ceramics, which are widely utilized as optical functional transparent materials in military equipment such as individual body armor visors, missile detection windows, vehicle observation windows, and submarine periscopes.

Part Ⅳ：The two most popular types of ballistic ceramic materials

• Silicon carbide bulletproof ceramic

Silicon carbide covalent bonds are extremely strong, and still have high-strength bonding at high temperatures, which endows silicon carbide ceramics with excellent strength, high hardness, wear resistance, corrosion resistance, high thermal conductivity, good thermal shock resistance and other properties. At the same time, silicon carbide ceramics are moderately priced and cost-effective, and are one of the high-performance armor protection materials with the most development potential.

Silicon carbide ceramics have a vast development potential in the field of armor protection, and their applications are becoming more diverse in areas such as individual equipment and special vehicles. When used as protective armor materials, factors such as cost and specific application scenarios are taken into consideration. Typically, small ceramic panels are arranged and bonded to a composite backing to form a ceramic composite target plate, in order to overcome the failure caused by tensile stress on the ceramics, and to ensure that during projectile impact, only a single panel is shattered without compromising the integrity of the overall armor.

• Boron carbide bulletproof ceramics

Boron carbide is a superhard material with a hardness second only to diamond and cubic boron nitride among known materials, with a hardness of up to 3000kg/mm². low density, only 2.52g/cm³, which is 1/3 of steel; high elastic modulus of 450GPa; The melting point is high, about 2447°C; It has a low coefficient of thermal expansion and high thermal conductivity. In addition, boron carbide has good chemical stability, acid and alkali corrosion resistance, does not react with acid and alkali and most inorganic compound liquids at room temperature, and only has slow corrosion in hydrofluoric acid-sulfuric acid and hydrofluoric acid-nitric acid mixtures. And it does not wett and does not interact with most molten metals. Boron carbide also has a good ability to absorb neutrons, which other ceramic materials do not have. B4C's density is the lowest among several commonly used armor ceramics, and its high elastic modulus makes it a good choice for materials in military armor and space domains. The main problems with B4C are that it is expensive (about 10 times more than alumina) and brittle, which limits its widespread application as single-phase protective armor.

Part Ⅴ： Upgrade of bulletproof ceramic

Although the ballistic potential of silicon carbide and boron carbide is very large, the problems of poor fracture toughness and brittleness of single-phase ceramics cannot be ignored. The development of modern technology has put forward requirements for the functionality and economy of bulletproof ceramics: multi-functional, high-performance, lightweight, low cost and safety. Therefore, in recent years, experts and scholars hope to achieve the toughness, lightweight and economy of ceramics through microscopic adjustments, including multi-ceramic system composites, functional gradient ceramics, layered structure design, etc., and such armor is lighter than today's armor, which better improves the mobility performance of combat units. Functional gradient ceramics show regular changes in material properties through microscopic design components.

For example, titanium boride and titanium metal, as well as metal/ceramic composite systems such as alumina, silicon carbide, boron carbide, silicon nitride and aluminum metal, have a gradient change in performance along the thickness position, that is, the transition from high hardness to high toughness bulletproof ceramics is prepared.
Nano complex phase ceramics are complex phase ceramics formed by adding submicron or nanoscale dispersed particles to matrix ceramics. Such as SiC-Si3N4-Al2O3, B4C-SiC, etc., have a certain improvement in the hardness, toughness and strength of ceramics. According to reports, Western countries are studying the sintering of nanoscale powders to prepare ceramics with a grain size of tens of nanometers to achieve material toughening, and bulletproof ceramics are expected to achieve a big breakthrough in this regard.