模拟微重力条件下分散体系的聚集速率

IMECH-IR > 力学所知识产出(1956-2008)

	模拟微重力条件下分散体系的聚集速率
	乔润龙
导师	胡文瑞 ; 孙祉伟
	1999
学位授予单位	中国科学院力学研究所
学位授予地点	北京
学位类别	博士后
关键词	模拟微重力密度匹配聚集速率自然对流分散体系的浊度
摘要	设计了地面实验，单因素地测量了沉降和对流对分散体系聚集速率的影响。本工作富有新意的要点如下：1。用浓度比例法和空白对照实验，验证了浊度法测量聚集速率的有效性。又用显微成象分析进一步做了旁证。2。对直径为1μm和2μm的聚苯乙烯胶乳球，应用密度匹配法检查重力引起的沉降对聚集的影响，所得结果显示，重力引起的沉降会减慢聚集速率，但幅度不大。对1μm和2μm的胶乳球，分别减小7%和11%，即随粒径的增加，沉降的影响有变大的趋势。3。为了在较长时间（1小时）内在样品池中建立并保持稳定微对流（小到5μm/s），需要在样品池两边保持稳定的微小温度差（小到0.1 ℃），这个技术困难得到成功的解决。配合我们研制的显微放大设施，使我们能单因素地研究微对流对聚集过程影响成为可能。4。采用在测量聚集速率的同时，控制并监视对流的办法。发现微对流会减慢聚集过程，而稍快的小对流有加速聚集过程的趋势。但幅度都很小。我们的实验事实不支持荷兰科学家推测的对流会急剧减慢分散体系的聚集过程。
英文摘要	The effect of gravitational sedimentation and free convection on coagulation rate of dispersions was measured separately in ground-based experiments. Main contributions of this thesis are summarized as follows: -We tested the validity of using turbidity versus time towards determining the coagulation rate through concentration and blank experiments. It was verifyed with analysis by microscopic image. -The influence of gravitation sedimentation on coagulation process of dispersion systems was tested with a density-matching method for 1 μm and 2 μm polystyrene particles. The result shows that gravity slows coagulation rate slightly 7% and 11% for 1 μm and 2 μm particles respectively. And the effect of sedimentation increases with increasing particle size. -A small constant temperature difference is kept between the two walls of the sample cell in order to maintain a constant convection in the cell. The free convection is monitored with microscopic image technique so that we can study the effect of convection on coagulation process separately. -Free convection was controlled and monitored when coagulation rates of dispersions were measured. It is found that a microconvection can reduce coagulation rate and a small convection can increase coagulation rate by a very small margin. Our experimental results do not support Folkersma's assumption that free convection slows rapidly coagulation rate.
索取号	29871
语种	中文
文献类型	学位论文
条目标识符	http://dspace.imech.ac.cn/handle/311007/23650
专题	力学所知识产出(1956-2008)
推荐引用方式 GB/T 7714	乔润龙. 模拟微重力条件下分散体系的聚集速率[D]. 北京. 中国科学院力学研究所,1999.

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