Microstructure and electromagnetic properties of Al₁₈B₄O₃₃w/Co composite particles prepared by electroless plating method

Al₁₈B₄O₃₃w/Co composite particles were prepared successfully through electroless plating Co on Al₁₈B₄O₃₃ whiskers. The growth behavior of the coatings, the effect of the process parameters and the electromagnetic properties of the prepared Al₁₈B₄O₃₃w/Co composite particles were investigated. The reduced Co nucleated first on the pre-activated surface of the whiskers to form insular particles which then grew larger gradually and eventually merged together to form continuous coatings. The reaction rate increased but the mass gain decreased with the increase of the bath pH and the bath temperature. The crystallinity of the deposited Co decreased with the increase of phosphorous content as well as the bath temperature. The effect of loading is much weaker compare to that of bath pH and bath temperature. The permittivity and the permeability of the prepared Al₁₈B₄O₃₃w/Co composite particles are markedly higher than those of the raw Al₁₈B₄O₃₃ whiskers in microwave band. Relaxation resonance is found in the samples with thick Co coatings due to the presence of eddy current, which deteriorates the permeability of the Al₁₈B₄O₃₃w/Co composite particles.