Iron containing silicon carbide on ultra high temperature absorber provides powerful technical support
The application of stealth technology to improve the attack and survivability of modern weapon system and improve the overall operational effectiveness has become an important part of weapon development in all countries. With the increase of the speed of Aeronautics and Astronautics, the development of high temperature electromagnetic wave absorbing materials which can adapt to the high Maher number determines the development level of the new weapon to a great extent. For example, the electromagnetic absorption coatings on the stealth aircraft in the US can reduce the reflection of radar waves in a wide frequency band by 7~10 dB.
The new wave absorbing materials need to meet the characteristics of "thin, light, wide and strong". If the harsh conditions (such as high temperature, oxidation and corrosion) are taken into consideration, there will be higher requirements for absorbing materials. At present, the rate of cruise missile, ground to ground missile and air to air missile has reached more than 5 Maher, and the running rate of airspace aircraft in the future is close to 10 Maher, which puts forward the requirement of high temperature resistance to electromagnetic window materials subjected to intense aerodynamic heating. In the case of more than 1000 degrees of gas heating temperature above 1000, the polymer and metal material can not meet the requirements of the absorbing materials because of chemical decomposition and strength reduction. Therefore, the development of high temperature stealth or high temperature absorbing materials is developing carbon, ceramic materials and their composite materials. The advantages of high temperature mechanical properties are good high temperature mechanical properties (melting point above 2000 C, small creep) and density. Low (about iron 1/4 ~ 1/3), stable wave absorption performance (resistance wave absorption and resistance with temperature rising more stable, no electromagnetic loss attenuation and yield effect), can also effectively weaken the infrared radiation signal, and silicon carbide based ceramics are the main components for the production of multiband ultra high temperature absorbing materials. It is reported that the SiC fiber reinforced glass ceramic matrix composite has been reported in the United States and can be applied to the rear of the tail nozzle of the F117 stealth aircraft and can withstand a high temperature of 1093 degrees centigrade. In order to overcome the lack of magnetic loss and narrow wave width of SiC ceramics, polyferric caranane (PFCS) has been synthesized by National University of Defense Technology in China, and the Si-C-Fe-O fiber with low resistivity to l0 ~ 2 Omega M can be produced. This kind of silicon carbide fiber containing iron particles can be used to prepare a good high temperature and broadband electromagnetic wave absorbing material. If the content and distribution of iron particles can be optimized and the bulk preparation ability is formed, the iron containing silicon carbide materials will provide a powerful technical support for the development of ultra high temperature absorbing materials in China.
Nanoscale absorbing materials have the characteristics of wide frequency band, light mass, and many other characteristics. Therefore, nanomaterials are studied and explored as a new generation of absorbing materials in the United States, Russia, France, Germany and Japan. The absorption principle of nanomaterials is due to the quantum tunneling effect, quantum size effect and interfacial effect of nanomaterials, and these absorption effects will be maintained at high temperature. The high temperature absorbing nano ceramics mainly refers to the doped ceramic materials based on SiC. They have certain wave absorbing properties, and have the advantages of high temperature resistance, small relative density, high strength and high resistivity.
The combination of nanoscale and fibrosis can greatly improve the mechanical and absorbing properties of the ceramic materials, such as the SiC nanowire epoxy composite made by a university in Taiwan, which has excellent electromagnetic wave absorption ability in a wide frequency range.
The porous structure and high specific surface area can enhance the surface polarization and anisotropy of the material, and enhance the electromagnetic wave absorption mechanism of nanomaterials, such as surface polarization, quantum tunneling effect, multiple scattering of interface and so on. Therefore, the preparation of hollow or porous nanostructured ceramic fibers will be an important research direction for new high temperature absorbing materials.