Metal coated ceramic particles are of great interest for the fabrication of higher quality metal matrix composites (MMCs). MMCs are composite materials consisting of a metal or alloy matrix containing ceramic particles, which show higher strength, higher wear resistance, enhanced high-temperature properties and increased chemical and erosion resistance compared to pure metals. However the main drawback in fabricating MMCs is caused by the low wettability of ceramic particles by metals because of their high difference in surface energy leading to particle aggregation and inhomogeneous particle distributions and resulting in MMCs with poor mechanical properties. A simple and elegant solution for these drawbacks is to coat the ceramic particles with a thin metal layer prior to the mixing process, thus minimizing the surface energy difference between particles and metal matrix.
Electroless plating is a widespread method for the fabrication of metal coatings because of its versatility, fast deposition rate, simplicity, and hence suitability for mass production. However in order to obtain homogeneous metal coatings the substrates need to be activated first, traditionally performed by immersing the substrate in solutions containing Pd or other noble metal ions, which catalyze the subsequent metal plating process. Regarding the high surface to volume ratio of small particles this activation process is extremely expensive and not suitable for a homogeneous particle coating. We have developed new activation methods based on (3-mercaptopropyl)triethoxysilane (MPTES), 3-aminopropyl phosphonic acid or polydopamine promoting the electroless deposition of metals even on nanoparticles.
The procedure is highly efficient and versatile regarding the surface of the ceramic particles and the choice of metals which can be deposited. Oxidic but also carbidic particles have been plated homogeneously with different metals such as copper, nickel, cobalt or silver.