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

对气相化学反应形成超细颗粒进行了实验和理论研究。本研究得出的主要观点如下。(1)实验将含有超细TiO_2种子颗粒的四异丙醇钛（TTIP）蒸汽以层流方式引入控制良好的圆柱形炉，在不同条件下分别采用均质成核和非均质成核的方法测量了TiO_2气溶胶的颗粒性能。通过比较得到的气溶胶的粒子数和粒径分布，与引入种子粒子和无种子粒子时均成核粒子的粒子数和粒径分布，实验阐明了TTIP蒸汽初始浓度、反应温度和种子粒子性质对化学气相沉积（CVD）抑制均成核的影响。(2)在理论计算中，采用简化反应混凝模型（SRC模型）对气相化学反应的颗粒形成进行了评价，求解了TiO_2气溶胶在层流管内热分解、布朗混凝和扩散沉积生成TiO_2单体的同时因素的种群平衡方程。模拟结果很好地解释了种子粒子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.