What Are the Uses of Advanced Composite Ceramic Substrates in Missiles?

In the mid-1980s, the United States developed an aerospace aircraft program that required both high-temperature tolerance and light mass. For this purpose, a variety of new high-temperature materials were developed, including advanced resin matrix composites, metal matrix composites, ceramic matrix composites, and carbon/carbon composites. Ceramic material is the preferred material for missile radome because of its excellent mechanical, thermal and electrical properties. The radome is the most widely used ceramic matrix composite material in missile structure.

Missile radome

The missile radome is located at the front end of the missile. Its function is to protect the navigation antenna from damage so that the missile can effectively hit the target. It is not only an important part of the aerodynamic shape of the missile but also the protection device of the antenna. During the flight of the missile, the radome should not only withstand aerodynamic heating and mechanical overload, resist the erosion of rain, sand, and other adverse working conditions, but also meet the stringent requirements of electrical performance proposed by the missile control loop. Therefore, the missile radome material should have the following properties:

Missile-radome

  • Excellent dielectric properties

In the guidance system, the transmission efficiency and aiming error of the radome are very sensitive to the dielectric properties of the material and its relationship with temperature and frequency. It is required that the material has low dielectric constant (10) and dielectric loss, and the dielectric properties do not change obviously with temperature and frequency.

  • Good heat resistance and thermal shock resistance

The high Mach number of missile can make the radome of instantaneous heating rate is as high as above 120 ℃ / s, so the material is required to have good thermal shock resistance, and the molecular structure of the material is required to be stable when the temperature is raised, and the material properties (such as dielectric properties and mechanical properties) change little to ensure that the radome can work normally when the temperature is raised.

  • High strength structural properties

The strength of the radome material should be high and rigid enough to satisfy the mechanical stress and bending moment caused by the longitudinal or transverse acceleration of the aerodynamic forces in the spacetime of the missile flying at high speed.

  • Resistance to rain erosion

It plays a decisive role in the design allowable range of impact Angle and the sensitivity of aircraft in rain erosion.

  • Low-temperature sensitivity

The dielectric properties and strength properties of general materials change obviously when they work at high temperature. Therefore, the properties of the radome material, especially the dielectric properties and strength, are affected by the temperature change as little as possible.

Ceramic-based missile radome

Ceramic-based missile radome materials mainly include silicon nitride based, a silicon oxide based and phosphate-based materials. Silicon nitride ceramics have not only excellent mechanical properties and high thermal stability but also low dielectric constant. Its decomposition temperature is 1900 ℃, and its erosion resistance is better than fused silica, and it can withstand 6 ~ 7 Ma rating of flight conditions. Silicon nitride ceramic composite radome is one of the main research targets in various countries, which has been identified as the most promising radome material by the test of the Georgia Institute of Technology. Yttria Stabilized Zirconia (YTZ), also known as yttria-zirconia, is the strongest ceramic material. This material offers the highest flexural strength of all zirconia-based materials, and the research on zirconia-based materials as missile radome is in progress.

Ceramic-based-missile-radome

  • Silica-based material

Because of the high flying Mach number of the missile and the relatively long heating time, if the radome of the medium-range missile is made of a single quartz ceramic material, it cannot meet the bearing requirement of thermal stress. In order to meet the requirements of medium and long-range ground-to-ground tactical and strategic missile radome, quartz glass, high-silica puncture fabric and orthogonal tri-directional quartz fabric reinforced silica matrix composites have been developed and successfully applied.

  • Phosphate-based materials

Phosphate matrix composite material is a kind of Russian characteristic permeable material, which is made by impregnating cloth or fabric with a phosphate solution and then curing under pressure. Aluminum phosphate has stable performance in 1500 ~ 1800 ℃. At present, such materials have been used in cruise missiles, anti-missile missiles, tactical missiles and space shuttles. The most obvious disadvantage of phosphate is that it is highly hygroscopic, so the surface of the composite material needs to be coated with an organic coating for moisture-proof treatment.

  • Silicon carbide ceramic matrix composites

Silicon carbide ceramic matrix composites have a series of excellent properties, such as low density, high-temperature resistance, ablation resistance, erosion resistance, and oxidation resistance, and it has a wide application prospect in the field of aerospace. Since the late 1980s, the United States has successfully developed a series of C/SiC, SiC/SiC ceramic matrix composites, which can be applied to the re-entry nose cone of missiles, the front end of wings and other heat-resistant structures.

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Zirconia Ceramic Structural Parts VS Auto Parts

As we all know, a car is a product with an extremely demanding operating environment and working conditions, so the various components that make up this giant must have very superior functions. The zirconia ceramic structure has been widely used in auto parts.

Zirconia ceramic structure parts with excellent performance just make up for the lack of metal materials, so they began to be accepted by the automobile. For example, it has a long vibration tolerance of 20 grams; as parts used in combustion and exhaust system, it can endure 50 ~ 60 ℃/S of thermal shock for a long time; due to strong mechanical reliability of the zirconia ceramic, the failure rate is usually between 10 and 5; it can also be mass produced and low in price, which is convenient for the formation of industrial management.

Zirconia Ceramic Structural Parts
Zirconia Ceramic Structural Parts

In recent years, scientists in the international special ceramics field have developed a large number of automobile special ceramics through hard research, and experiments and industrial applications have proved that the superior mechanical properties and high-temperature chemical properties of ceramic materials have far surpassed those of metal materials or other materials. At present, the applications of zirconia ceramic structure parts in auto parts industry are as follows.

Zirconia ceramic oxygen sensor

The zirconia ceramic oxygen sensor has high mechanical properties and reliability. As a component of clean exhaust, O2 concentration in automobile exhaust is measured, and the measured value is fed back to the gas and fuel supply system of the engine to keep the fuel always in full combustion state. Since all phases of the ceramic material are partially stabilized zirconia mixed with fully cubic, tetragonal and monoclinic crystals, the mechanical properties are superior during use and the heat generated by friction can be reduced.

Zirconia ceramic valve heater

In order to make the engine burn completely when starting, a heating device, the valve heater, is installed on the suction side of the engine, which is used to heat the air so that the fuel vaporizes and mixes completely. In order to control the temperature and improve the reliability of the device, the barium titanate ceramic PTC (thermistor) is used as the valve heater. After adopting the ceramic valve heater, the engine is in full combustion state when it starts, so as to improve thermal efficiency, energy saving, and purification and exhaust efficiency.

Zirconia ceramic engine

The application of special ceramics in the automobile has been popularized by the piston engine, and there will also be an auxiliary combustion chamber, piston head, cylinder liner, cylinder head, pressurized rotor, etc. Special ceramic materials such as silicon nitride, silicon carbide, and partially stabilized zirconia are also being considered for these parts.

Zirconia ceramic engine
Zirconia ceramic engine

Zirconia ceramic sensor

The shock absorber of the high-class car is a smart shock absorber which is developed by using the positive piezoelectric effect, inverse piezoelectric effect and electrostrictive effect of sensitive ceramics. The smart shock absorber, with its ability to recognize and self-regulate the road, minimizes the vibration of cars on rough roads, making them comfortable for the passenger.

Intelligent ceramic wipers

The intelligent ceramic windshield wiper is made of barium titanate, which can automatically sense rainfall and adjust the windshield wiper to the best speed. Some other ceramic sensing elements, such as thermal, pressure, humidity and magnetic ceramic materials, can also be sensitive to temperature, humidity, condensation, anti-freezing, etc. with automatic control and adjustment.

In addition, many parts, and small devices used in automobiles are made of special ceramic materials, such as the electronic buzzer, ultrasonic vibrator, heat absorbing glass, photocell, oil plug ring, oil seal, etc. These kinds of automobile products made of new special ceramic materials generally have high physical and chemical properties, such as anti-seismic, wear-resisting, anti-corrosion, high-temperature resistant, lightweight and easy to process and produce.

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