The Preparation Of Cenosphere Composite Absorbent

Microwave absorbing materials, converting electro-magnetic energy into heat, reducing the intensity of the reflected wave, to obtain electro-magnetic compatibility, have been widely used in aerospace filed, radar technology and military facilities, and they are researching hotspot in these technology field. The shortcomings of electromagnetic wave absorbent are weak absorption, heavy density, and narrow-bandwidth. To overcome these shortcomings, composite of different absorbents is may be a good solution.The M-type ferrite is thought to be a very important magnetic absorbent for its special properties, such as high resistivity, strong absorption and wide-bandwidth. But the microwave absorption properties of the ferrite are high density. It is hard to use widely because of its density. The microwave absorption properties of ferrite are not as good as metal powder at high frequency. The metal powder is widely used as microwave absorbent for its high specific saturation magnetization, high magnetic susceptibility. But the microwave absorption properties of the metal powder are narrow-bandwidth. The electromagnetic properties of the ferrite and metal powder are complementary. The combination of them is expected to create good electromagnetic wave absorption composite. But the defect of high density is not benefit for the preparation of light absorber. In response to the need for high performance absorber, in this paper, the composite-coating absorbers with hollow cenosphere as nuclear are prepared by sol-gel and electroless plating technology. The main work and achievements of this paper are listed as follow:(1) Fore treatment of electroless Ni-P is studyed:PdCl2 activator and AgNO3 are used as activator in the chemical plating, to compare results and analysis the reason.(2) Study the effect of the solution composition, temperature, PH, loading capacity on the performance of Ni-P coating layer. The best electroless processing is obtained. The magnetic properties of Ni-P coated cenospheres are 8s (2.18emu/g) and He (29.93KA/m).(3) Thin films of Barium hexaferrite are prepared on fly ash cenpsphere particles by sol-gel. The magnetic properties of Ni-P coated cenospheres are 8s (6.59emu/g) and He (315.6KA/m).