Study Of The Electroless Plating Ni-B And Ni-Mo-B On Micrometer Diamond Particles

Diamond has many characters, such as high thermal, low permittivity, high band gap, super high hardness, low friction etc, which makes it possible to be widely used in industry. In nowadays diamond tools applications, people usually choose metals with low melting point as bonding agent. Because diamond belongs to nonmetal, there is high interface energy between diamond and metal(or alloy),which makes it difficult for metal or alloy to infiltrate the diamond .The diamond is easy to fall off from the tools while in the process of work, so the diamond can't be made full use, which will reduce diamond's life. Because electro less plating doesn't need special huge equipment, low cost, and has no limit to material shape, it is a best choice to coat metals on micro-meter diamond by electro less plating method.In the experiment, the diamond particles we used are 10 micrometer in particle size and specific area is 0.8930m /g. After a series of pre-treatments on artificial diamond, such as oil removal, alligatoring, sensitizing treatment, we successfully plated nickel film and nickel-molybdenum film on micrometer diamond particles by ways of dropping nickel chloride slowly and continuous instillation. The influence of mass concentration of nickel chloride hexhydrate, sodium borohydride, ethylenediamine, sodium molybdate, PH, temperature on relative deposition rate were studied with L₁₆(4⁵) orthogonal test, and the optimized parameters were obtained. The coating pHase constitutions and topograpHy were measured by X-ray-diffraction (XRD) and Scanning Electron Microscopy (SEM) separately.The SEM images of nickel coating show that the coating is sporadically downy masses by one time plating, and existence of many uncovered diamond particles;but the four time plating coating is better than one time plating coating except some pinpoint holes. In the continuous instillation the coating present homogeneous globular particle on diamond surface and uncoated particle decreases. The XRD results show that the coating composition is Ni and Ni₂B.In the electro less plating Ni-Mo-B alloy, the operation mode is the same as chemical nickel plating. The results show one time electro less deposits is powdered substance and cladding exist some uncoated regularly shaped small diamond. But the small diamond particles don't conglomerate into micro-aggregates. After four times plating, the coating looks better than one time coating and takes on even scales. In the continuous instillation the coating assume sporadically downy masses, and many diamond surfaces uncover coatings. The XRD proves the coatings are main Ni and Ni₂B except little molybdenum.