EVALUATION AND CONTROL OF FORMATION OF ULTRAFINE PARTICLES BY GAS PHASE CHEMICAL REACTION.

对气相化学反应生成超细颗粒进行了实验和理论研究。主要研究内容如下：(1)在实验中，将含有超细晶种二氧化钛的四丙醇钛(TTIP)蒸气以层流形式引入可控圆柱炉中，并在不同条件下测量了均匀成核和非均相成核形成的二氧化钛气溶胶的颗粒性质。(2)在理论计算中，采用简化的反应凝聚模型(SRC模型)，用简化的反应凝聚模型(SRC模型)和描述TTIP蒸气热分解生成TiO_2单体的同步因子的布居平衡方程，研究了TTIP蒸气的初始浓度、反应温度和颗粒性质对化学气相沉积(CVD)抑制均匀成核的影响。解决了层流管流中二氧化钛气溶胶的布朗凝聚和扩散沉积问题。模拟结果较好地解释了晶种颗粒的存在抑制均匀成核的实验趋势。

The formation of ultra-fine particles by gas phase chemical reaction has been studied experimentally and theoretically. The major points obtained in this study are as follows.(1) In the experiment, the titanium tetraisopropoxide (TTIP) vapor containing ultrafine seed TiO_2 particles is introduced into the well-controlled cylindrical furnace in a laminar flow, and the particle properties of TiO_2 aerosol by homogeneous and heterogeneous nucleation were measured under various conditions. By comparing the particle numbers and size distributions of the resulting aerosol with those of introduced seed particles and those of homogeneously nucleated particlesin the a bsence of seed particles, effects of initial concentrations of TTIP vapor, reaction temperature, and properties of seed particles on the suppression of homogeneous nucleation by chemical vapor deposition (CVD) are experimentally clarified.(2) In the theoretical calculation, the simplified reaction coagulation model (SRC model) was used to evaluate the particle formation by the gas phase chemical reaction, and the population balanceequation expressing the simultaneous factors of generation of TiO_2 monomers by thermal decomposition of TTIP vapor, brownian coagulation and diffusive deposition of TiO_2 aerosols in a laminar pipe flow was solved. The exprimental tendencies on the suppression of homogeneous nucleation by the existence of seed particles was explained well by the simulation results.