単一液滴の乾燥過程と噴霧熱分解法による酸化物微粒子の生成機構の解析

抄録

The formation mechanism of solid particles derived from droplets by spray pyrolysis was studied. A droplet of zinc nitrate aqueous or methanol solution weighing 1 to 3mg was set on the tip of a 0.1mmφ Pt wire, This droplet was dried in a furnace at a desired temperature. Decreases in weight and diameter of the droplet by evaporation of solvent were measured with a balance and a camera system, The (droplet weight)^2/3 vs. time curve was divided into two parts: a straight portion in the first stage (part 1) and a curved one in the following stage (part 2). The critical particle size, which corresponds to the formation of hard shell on the surface of the droplet, was estimated from the droplet weight at the joint of part 1 and part 2. This critical particle size was sensitive to the drying temperature and increased when the drying temperature increased. This relationship was also confirmed in a spray pyrolysis process. For constant drying temperature, the porosity of the particles was constant even the initial concentration of droplets changed, and the particle size changed with 1/3 power of the initial concentration.