Dimensional and formation analysis of interpenetrating phase composites
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The properties of interpenetrating phase composites produced by using partially sintered materials and infiltration techniques were studied. Alteration of the particle matrix with respect to particle size and the sintered network may significantly alter mechanical properties of infused network. Two alumina powders, RC172 and A16SG, were dry-pressed and centrifugally cast while In-Ceram alumina was slip cast according to the manufacturer's recommendation. Specimens were then sintered between 1250 degrees C and 1400 degrees C. Green densities and sintered densities were measured and the microstructure of selected specimens was examined by scanning electron microscope. The strength was evaluated using a biaxial strength test. The results showed that the strength of partially sintered alumina was significantly different between small particles (less than 0.3 [mu]m) and larger particles (larger than 1.2 [mu]m) at the same sintering temperature and time. Dry-pressed specimens sintered at 1250 degrees C were separated into two groups for either glass infusion or resin infusion. The results indicated that the biaxial strength of alumina matrix was greatly increased by both glass and resin infusion. Altering the matrix, such as reducing the particle size, can further enhance the strength of the infused materials. Three different particle sizes of hydroxyapatite powders, 40 [mu]m, 20 [mu]m and less than 20 [mu]m, were used to study sintering mechanisms and resin infusion of hydroxyapatite. The results showed that there was a significant difference between biaxial strengths of infused disks of small particles (less than 20 [mu]m) and larger particles (40 [mu]m) when sintered at 1350 degrees C. The strength of resin infused disks of hydroxyapatite increased as particle size decreased. The reinforcement effect of fumed silica added to heat cured resin composite was studied. Two particle sizes of fumed silica were used, 0.007[mu]m and 0.011[mu]m. The results demonstrated that the addition of the low level of small particle silica filter has a pronounced influence on the properties of composite and interpenetrating composite materials.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Thesis (D.Sc.D.)--Boston University, Henry M. Goldman School of Dental Medicine, 2002 (Restorative Sciences/Biomaterials).Includes bibliography (leaves 133-139).
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