Papers by Keyword: Anisotropic Crystal Growth

Abstract: The biomimetic method of achieving dense platelike grain growth of the high temperature superconducting ceramic YBa2Cu3O7 (YBCO) has been studied. By using various organic matrices (dextran and chitosan) having different molecular structures, the final size and arrangement of the platelike YBCO grains exhibit significant differences, possible reasons for which are discussed. The different organic matrices used also indirectly affect the superconducting properties of the YBCO formed. By elucidating the role of the organic matrix in the biomimetic synthesis process in this way, the whole process could be controlled more precisely, leading to structural and electrical properties of the final product more desireable for specific applications.

Abstract: β-Si3N4 and β-SiAlON powders were prepared by combustion synthesis with SrCO3 and NH4F used as additives. The resultant β-Si3N4 and β-SiAlON powders consisted of elongated prismatic microcrystals. By adding SrCO3, the anisotropic growth of β-Si3N4 and β-SiAlON crystals is improved and their aspect ratios increase. The addition of NH4F enhanced nitridation reactions and reduced the residual Si in combustion products. It was proposed that the elongated prismatic β-Si3N4 and β-SiAlON crystals grew from liquid phase and the composition and property of this liquid was affected by the addition of SrCO3.