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CHARACTERIZATION OF SIMULATED MICROSTRUCTURES IN POLYDISPERSE PARTICLE DEPOSITION
Rajagopalan, Raj,Kim, Hern 한국화학공학회 1994 Korean Journal of Chemical Engineering Vol.11 No.4
The deposition of polydisperse particles under the influence of gravity is examined using computer simulation. A parameter, σ, that represents the standard deviation of particle size is used for studying the effect of the variation in polydispersity on the resulting microstructures. Structural correlations are examined through contact networks, radial and angular distribution functions, and diffraction patterns. The results show that the onset of ordering appears near σ=0.05 as σ is decreased. The long-range ordering of the structures is not influenced by the introduction of a small amount of polydispersity, which may increase the uniformity of local density distribution in the angular direction. Polydisperse systems with small deviations in size display stronger positional order in some directions and this in turn contributes to the uniformity of overall packing structures.
Rajagopalan, Raj,Kim, Hern 한국화학공학회 1994 Korean Journal of Chemical Engineering Vol.11 No.4
The simultaneous effects of adhesion and polydispersity on packing (or deposit) microstructures and their bulk properties are examined. The results show that the microstructures and bulk properties of the deposits vary sharply with the introduction of even small adhesion and polydispersity. A structural phase diagram is obtained as functions of adhesion and polydispersity. Increases in adhesion lead to noticeable or large fluctuations in packing fractions for polydisperse systems. However, the packing fraction can be stabilized and the fluctuations greatly reduced regardless of fhe magnitude of the polydispersity index by keeping the adhesion relatively low (i.e., s≤0.1).
MICROSTRUCTURAL ANALYSIS OF SINTERING BEHAVIOR OF INTRA - GRAIN PORES
Rajagopalan, Raj,Kim, Hern 한국화학공학회 1998 Korean Journal of Chemical Engineering Vol.15 No.6
A lattice-based Monte Carlo simulation approach has been developed for studying the behavior of intragrain pores during the intermediate and final stages of sintering. The changes of the microstructures and the resulting properties of intra-grain pores during sintering are easily examined. The sintering behavior such as pore size distribution, average pore size, etc. is in very good agreement with the experimental observations. In addition, the relationships between the number of pores and the average pore volume agree well with theory.
Rajagopalan, Raj,Kim, Hern 한국화학공학회 1995 NICE Vol.13 No.1
The simultaneous effects of adhesion and polydispersity un packing(or deposit) microstructures and their bulk properties are examined. the results show that the microstructures and bulk properties of the deposits vary sharply with the introduction of even small adhesion and polydispersity. A structural phase diagram is obtained as functions of adhesion and polydispersity. Increases in adhesion lead to noticeable or large fluctuations in packing fractions for polydisperse systems. However, the packing fraction can be stabilized and the fluctuations greatly reduced regardless of the magnitude of the polydispersity index by keeping the adhesion relatively low(i.e., s≤0.1).
김헌,Rajagopalan,Raj 한국화학공학회 1994 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.32 No.5
Hard-sphere입자들의 침적시 미세구조 및 부피분율과 같은 성질의 변화를 조사하기 위한 Monte Carlo 모사모델이 개발되었다. 다양한 입자계 및 공정조건의 영향을 분석하기 위한 주요 매개변수로서 Peclet수가 사용되었다. 침적물이 결정구조를 형성하는 최적조건, 동적 상거동, 초기 부피분율의 영향, 복합분산입자들의 분리 등이 검토되었다. 본 모델로 예측한 여러 결과들이 실험관찰과 정성적으로 잘 일치하는 것이 주목되었다. 본 모델은 여러 관련된 실험연구를 설계하는 간편하고도 효과적인 기구로서 사용될 수 있다. A Monte Carlo simulation model was developed to investigate the changes of microstructures and their properties such as packing fraction during the deposition of hard-sphere particles. As a major parameter Peclet number was used to analyze the effects of particulate systems and process conditions. The optimum conditions where the deposits form ordered structures, the dynamic phase behavior, the effects of initial volume fraction, the size fractionation of polydisperse particles, and so on were also examined. It was noted that a number of results predicted from the present model are in good qualitative agreement with experimental observations. The present model can be used as a simple and effective tool for designing a number of related experimental studies.