Preparation of Silver-Coated Al–Si Particles by a Polyol Method

抄録

Silver-coated Al–Si alloy particles were prepared by a polyol method to develop a novel conductive filler. The influence of the reaction temperature, reaction time, concentration of silver ions, and addition of a protective agent on the size of the silver particles formed and silver coverage on the Al–Si alloy particles was investigated. The addition of polyvinylpyrrolidone into the liquid phase led to a reduction in the size of the silver particles and an increase in the silver coverage on the alloy surface. The optimum concentration of silver ions for silver coating ranged from 3.8×10⁻² to 1.5×10⁻¹ mol/L, and an excess amount of silver ions (0.3 mol/L) caused agglomeration of the particles. The coating of the alloy was achieved by the adhesion of small silver particles onto the alloy surface, followed by growth of the particles with increasing reaction time. Control of the thickness of the layer was possible by changing the silver nitrate concentration in ethylene glycol within a range not exceeding 0.3 mol/L. Silver nitrate concentrations of 7.5×10⁻³ or 1.5×10⁻² mol/L were suitable to obtain particles with a thin silver layer and high coverage. Coverage of the entire surface of Al–Si alloy particles was achieved by coating Al–Si particles at AgNO₃ concentration of 3.8×10⁻² mol/L and then recoating the coated particles at the concentration of 1.5×10⁻² mol/L. Silver consumption after first coating and recoating was 2 and 78%, respectively, based on the amount of silver in the staring material and it was confirmed that silver was efficiently used for coating in the recoating process.