Preparation And Applications Of Lightweight Magnetic Material

A characteristic of the conventional magnetic, the heavy density, causes a few obstacles to application in practice. For example, conventional magnetic particles in magnetorheological fluids(MRF) can easily settle and make MRF unstable. Radar absorbing coating (RAC)that contains conventional magnetic particles is heavier than normal. If the density of magnetic particles can be reduced, its application should be widened.One focus of this paper is to synthesize a kind of light magnetic material based on coating of light material-hollow glass micro-sphere with magnetic metal by electroless plating method. And the effect of the light magnetic material applied to MRF and RAC is another focus.In the research of surface pretreatment process of electroless nickel on hollow glass micro-spheres, we explored a new pretreatment technology that treated hollow glass micro-spheres with coupling agent solution. The new pretreatment method followed by electroless plating can increase the number of active spots on the surface of glass spheres, improve the plating speed, complete the plating coat, plate metal on 10 um diameter micro-sphere. In our experiment, the new pretreatment method had been adopted in electroless nickel plating and electroless cobalt plating process .Through study about the influence of various parameters of plating bath - PH valve, plating temperature, reducing agent and stabilizer concentration and plating time, optimal plating condition was gotten finally. At the same time, we made some studies of instruction about the process of electroless cobalt plating of hollow glass micro-spheres too.The properties of products - density, morphology and structure of deposits were analyzed. The results showed: The density of products (3 g/cm3) was lower than the density of conventional magnetic particles (7~8 g/cm3). Under scanning electron microscopy it revealed that the typical surface morphologies of electroless nickel deposits consist of cellular formations and the layer of metal became thick as plating time goes on. The structure of crystals of plating coat was investigated by X-diffract and infrared spectra. It was found that the structure varied with the magnetism of material. When the structure varied from crystal to cryptocrystal, the magnetism became mild. Heat treatment on electroless nickel deposits can crystallize the deposit structure and improve the magnetism of product. But heat treatment on electroless cobalt deposits can make the structure oxidation.The kind of light magnetic material is benefited to manufacture MRF and RAC. Results showed as follows: The speed of settling of magnetic particle became slowly. The sediment stability was evidently improved and the apparent viscosity of MRF under magnetic field was larger than the initial viscosity. In RAC, the coating consists of light magnetic material and resins had some effect on electromagnetic radar absorb.In a word, low density, complete and continuous coat and dispersed material can be gotten by simple electroless nickel or cobalt plating on hollow glass micro-spheres. The kind of light magnetic material should have a wild application in future.