MECHANISM OF PARTICLE FORMATION BY HOMOGENEOUS AND HETEROGENEOUS NUCLEATIONS IN GAS-PHASE, LIQUID-PHASE AND SOLID-PHASE

颗粒大小的控制起着关键作用，因为最终的材料性能通常取决于初级颗粒的大小。均相成核在过去得到了广泛的研究。然而，现有理论的复杂性阻碍了其在材料制造等应用领域的实际应用。因此，除了经典的成核热力学理论外，还提出了能够准确估计成核粒子的数量、浓度和平均尺寸的模型，该模型是操作条件和物料性质的函数。用化学还原法制备银颗粒的液相成核实验成功地证实了该模型的预测。本研究的目的是使用不同的颗粒形成方法来检验先前模型的有效性。所获得的结果可以总结如下。第一年，单体扩散系数对…的影响对于采用液相还原法制备银粒子的体系，研究了较多的粒子产生，这也是以前模型中考虑的因素之一。通过加入增稠剂改变溶液粘度来控制单体扩散系数，实验发现产生的颗粒数浓度与单体扩散系数成反比，从而导致颗粒尺寸减小，定量支持了该模型。在第二年，用一个简单但实用的均匀成核模型研究了凝结水汽形成气溶胶粒子的机制。该模型是对先前开发并成功测试的液相均相成核模型的动力学机制的扩展，允许可靠地估计所产生的颗粒的平均尺寸和数浓度作为材料性质和操作条件的函数。考虑扩散损失和壁面凝结的模型预测值与实验结果吻合较好。较少

Control of particle size plays a critical role because the final material properties usually depend on the size of the primary particles. Homogeneous nucleation has been extensively studied in the past. However, the complexity of the available theory prevents its practical use in applied fields such as materials manufacturing. Thus apart from the classical thermodynamical theories on nucleation, the model which enables accurate estimation of the number concentration and average size of the nucleated particles as a function of the operating conditions and materiel properties has been proposed. Liquid-phase nucleation experiments in which silver particles were generated by a chemical reduction method have successfully confirmed the predictions of the model. The objective of this research is to check the validity of the previous model, using various method of particle formation. The results obtained can be summarized below. At the first year, the effect of monomer diffusion coefficient on … More particle generation, which is one of the factors included in the previous model, was studied for systems where silver particles were generated by a reduction method in liquid phase. The monomer diffusion coefficient was controlled by changing viscosity of the solution by addition of a thickener, and it was found experimentally that the number concentration of particles generated was inversely proportional to monomer diffusion coefficient resulting in particle size reduction, which quantitatively supported the model. At the second year, the mechanism of aerosol particle formation from a condensing vapor is examined using a simple but practical homogeneous nucleation model. The model, which is an extension to the kinetic regime of a model previously developed and successfully tested for liquid-phase homogeneous nucleation, allows reliable estimation of the average size and number concentration of the generated particles as a function of material properties and operating conditions. The model predictions taken into accout for diffusion losses and wall condensation are in excellent agreement with the experimental results. Less