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Interfacial Solid-Liquid Diffuseness and Instability by the Maximum Entropy Production Rate (MEPR) Postulate

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2015, PhD, University of Cincinnati, Engineering and Applied Science: Materials Science.
Numerous investigations spanning over sixty years have failed to comprehensively validate any of the currently existing solid-liquid growth instability theories. A recent comparison of the linear stability-model predicted solute diffusion coefficients from both land and space based solidification experiments, with the independently measured solute diffusion coefficients obtained from non-solidification experiments has also failed to show any correlation with measurements made by direct (non-solidification) techniques. A new model based on maximum entropy production rate postulate (MEPR) is proposed for the prediction of solid-liquid interface stability. A test of the new MEPR model with numerous published experiments shows that all published instability conditions of planar to perturbed interface are accurately predicted to the right order by the new model. The MEPR model avoids the association of a solid-liquid surface energy for the solid-liquid interface between the phases or a liquid diffusion coefficient which are both key features of the existing models. The development of the model has led to the establishment and confirmation of the two major types of solid-liquid interfaces being noted; a diffuse interface and a sharp interface. The formation of either a diffuse interface or a sharp interface at the solid-liquid interface is determined by a constant N. A diffuse interface is present when N is greater than two whiles a sharp interface is formed when N is less than one but greater than zero. The model is able to predict the diffuseness interface thickness and the number of lattice spacings called the driving force diffuseness. An inverse form of the Jackson’s criterion is introduced as thermal roughness which is unified into the diffuseness model as the total diffuseness. The total diffuseness is the sum of the driving force diffuseness and thermal diffuseness which is able to accurately predict the conditions for facet and non-facet formation at interface breakdown. It is also able to predict the facet to non-facet transition with changing solidification conditions. The diffuse interface and the sharp interface are both critical in predicting facets and non-facets at the interface at instability. In model also establishes a new interface instability criterion for the presence of both diffuse interface and sharp interface which can correctly predict the order of V/GL ratio for the instabilities from a planar interface into a perturbed interface if the corresponding partition coefficient are known.
Jainagesh Sekhar, Ph.D. (Committee Chair)
Relva Buchanan, Sc.D. (Committee Member)
Jude Iroh, Ph.D. (Committee Member)
Rodney Roseman, Ph.D. (Committee Member)
Vijay Vasudevan, Ph.D. (Committee Member)
206 p.

Recommended Citations

Citations

  • Bensah, Y. D. (2015). Interfacial Solid-Liquid Diffuseness and Instability by the Maximum Entropy Production Rate (MEPR) Postulate [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310971

    APA Style (7th edition)

  • Bensah, Yaw. Interfacial Solid-Liquid Diffuseness and Instability by the Maximum Entropy Production Rate (MEPR) Postulate. 2015. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310971.

    MLA Style (8th edition)

  • Bensah, Yaw. "Interfacial Solid-Liquid Diffuseness and Instability by the Maximum Entropy Production Rate (MEPR) Postulate." Doctoral dissertation, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310971

    Chicago Manual of Style (17th edition)