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COMSATS Institute of Information Technology Lahore
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Papers by Matthew Seabaugh
27th Annual Cocoa Beach Conference on Advanced Ceramics and Composites: A: Ceramic Engineering and Science Proceedings, Volume 24, Issue 3
ABSTRACT
The anisotropic grain growth of liquid phase sintered alpha alumina was investigated. Samples of ... more The anisotropic grain growth of liquid phase sintered alpha alumina was investigated. Samples of controlled anisotropic fraction (˜9 mum major axis, aspect ratio = 10) were prepared by adding anisotropic template particles to matrix material of fine particle size (initial median size = 0.2 mum) with CaO and SiO2 additives. The resulting slurry was tape cast, laminated and sintered to produce highly textured materials. This process is called templated grain growth, or TGG. The sample texture was measured by x-ray diffraction rocking curve measurements, and the orientation distribution function was fit using the March-Dollase function. The fitting parameters were used to calculate the stereological correction factors for template size, which was measured by image analysis of SEM micrographs. Together, these techniques yielded accurate measurements of the growth of the anisotropic template particles during sintering. Texture development in TGG materials was found to be directly controlled by the growth of the template particles, which in turn was strongly affected by liquid phase content and initial template concentration. Single crystal samples were embedded in alumina matrices of the same composition as the TGG samples. Growth of several crystal directions was measured under a variety of sintering conditions. Growth was found to be strongly affected by liquid phase content. Growth of the single crystals in non-basal directions was modeled using a diffusion controlled model of growth, while the basal growth of the single crystals was found to agree well with a two-dimensional nucleation and growth model. Using the expressions obtained for single crystal growth, the anisotropic grain growth of the template particles in the TGG samples was modeled. Template size and concentration played significant roles in the growth of template particles. These effects can be accommodated for within the single crystal growth theories to provide a measure of the effect of template-template impingement on growth.
Interface Sci, 2000
Single crystals of α-alumina with {0001}, {1120} and {0112} orientations were embedded in a matri... more Single crystals of α-alumina with {0001}, {1120} and {0112} orientations were embedded in a matrix of liquid phase sintered alumina to study α-alumina single crystal growth in the presence of a calcium aluminosilicate liquid. Growth on the {1120} and {0112} surfaces was observed to occur by a diffusion-controlled mechanism while growth on the basal surface was controlled by two-dimensional nucleation. Growth models, which incorporate the change in matrix grain size, were derived and shown to fit the growth kinetics.
27th Annual Cocoa Beach Conference on Advanced Ceramics and Composites: A: Ceramic Engineering and Science Proceedings, Volume 24, Issue 3
ABSTRACT
The anisotropic grain growth of liquid phase sintered alpha alumina was investigated. Samples of ... more The anisotropic grain growth of liquid phase sintered alpha alumina was investigated. Samples of controlled anisotropic fraction (˜9 mum major axis, aspect ratio = 10) were prepared by adding anisotropic template particles to matrix material of fine particle size (initial median size = 0.2 mum) with CaO and SiO2 additives. The resulting slurry was tape cast, laminated and sintered to produce highly textured materials. This process is called templated grain growth, or TGG. The sample texture was measured by x-ray diffraction rocking curve measurements, and the orientation distribution function was fit using the March-Dollase function. The fitting parameters were used to calculate the stereological correction factors for template size, which was measured by image analysis of SEM micrographs. Together, these techniques yielded accurate measurements of the growth of the anisotropic template particles during sintering. Texture development in TGG materials was found to be directly controlled by the growth of the template particles, which in turn was strongly affected by liquid phase content and initial template concentration. Single crystal samples were embedded in alumina matrices of the same composition as the TGG samples. Growth of several crystal directions was measured under a variety of sintering conditions. Growth was found to be strongly affected by liquid phase content. Growth of the single crystals in non-basal directions was modeled using a diffusion controlled model of growth, while the basal growth of the single crystals was found to agree well with a two-dimensional nucleation and growth model. Using the expressions obtained for single crystal growth, the anisotropic grain growth of the template particles in the TGG samples was modeled. Template size and concentration played significant roles in the growth of template particles. These effects can be accommodated for within the single crystal growth theories to provide a measure of the effect of template-template impingement on growth.
Interface Sci, 2000
Single crystals of α-alumina with {0001}, {1120} and {0112} orientations were embedded in a matri... more Single crystals of α-alumina with {0001}, {1120} and {0112} orientations were embedded in a matrix of liquid phase sintered alumina to study α-alumina single crystal growth in the presence of a calcium aluminosilicate liquid. Growth on the {1120} and {0112} surfaces was observed to occur by a diffusion-controlled mechanism while growth on the basal surface was controlled by two-dimensional nucleation. Growth models, which incorporate the change in matrix grain size, were derived and shown to fit the growth kinetics.