Development of Continuous Synthesis Process of Nanosize Titania Particles for Dye-Sensitized Solar Cell

本研究的目的是构建平均粒径小于50 nm、几何标准差小于1.2的单分散纳米二氧化钛（TiO_2）的连续合成工艺。制备纳米TiO_2颗粒的方法有堆积法和击穿法。本研究以醇盐法为构筑法，水解法为分解法。首先，研究了正钛酸四乙酯（TEOT）水解缩合反应合成TiO_2颗粒的醇氧法。采用间歇式反应器对制备纳米颗粒的条件进行了考察。将TEOT的乙醇溶液和聚合物分散剂羟丙基纤维素（HPC）与水-乙醇溶液混合进行反应。在TEOT浓度为0.025 mol/dm^3、水浓度为0.025 mol/dm^3、HPC浓度为2.5 g/dm^3的条件下，得到的颗粒平均粒径为38 nm，几何标准差为1.19。在间歇实验的基础上，采用所提出的段塞流管式反应器系统进行了连续合成。在该系统中，用于颗粒成核的填充床与段塞流时效管串联在一起。连续系统得到的颗粒平均粒径和几何标准差与间歇式反应器基本相同。采用间歇式反应器进行大颗粒除以颗粒表面溶解的聚合反应。用硝酸对醇盐法制得的颗粒进行胶化处理。硝酸浓度存在最优值，得到粒径为32 nm的颗粒，比醇盐法得到的颗粒小。几何标准差为1.22。

The purpose of this study is to construct the continuous synthesis process of monodispersed nanosize titania (TiO_2) particles in which mean particle size is under 50 nm and geometric standard deviation is under 1.2. To synthesis the nanosize TiO_2 particles, there are a build-up and a breakdown method. In this study, alkoxide method was used as a build-up method, and peptization was used as a breakdown method.First, alkoxide method, the synthesis method of TiO_2 particles by hydrolysis and condensation reaction of tetraethyl orthotitanate (TEOT), was examined. The condition to prepare the nanosize particles was examined by using a batch reactor. The ethanol solution of TEOT and hydroxypropyl cellulose (HPC), a polymer dispersant, was mixed with the water-ethanol solution to progress the reaction. At 0.025 mol/dm^3 of TEOT, 0.025 mol/dm^3 of water, and 2.5 g/dm^3 of HPC, the particle with 38 nm of mean particle size and 1.19 of geometric standard deviation was obtained.Based on the result of the batch experiment, the continuous synthesis was carried out using a slug flow tubular reactor system we have proposed. In this system, a packed bed for the nucleation of particles is connected in series with a slug flow aging tube. Mean particle size and geometric standard deviation of the particles obtained by the continuous system were almost same as that of the batch reactor.The peptization in which large particle was divided by the dissolution of the particle surface was carried out by using the batch reactor. The particle obtained by the alkoxide method was peptized using nitric acid. The optimum value exists for the nitric acid concentration, and the particle with 32 nm was obtained, which was smaller than the particle obtained by the alkoxide method. The geometric standard deviation was 1.22.