Papers by Keyword: Solution Technique

Abstract: Pure and stable YAG (Y3Al5O12) powders were synthesized by a PVA (polyvinyl alcohol) polymer solution technique. PVA was used as an organic carrier for the precursor ceramic gel. The PVA affected crystallization behavior, powder morphology, specific surface area and crystalline size of the synthesized powders. The precursor gels were crystallized to YAG at relatively a low temperature of 900 °C. The synthesized powders, which have nano-sized primary particles, were soft and porous, and the porous powders were ground to sub-micron size by a simple ball milling process. The ball-milled powders were densified to 94% relative density at 1500 °C for 1h. In this study, the characteristics of the synthesized YAG powders were examined by using X-ray diffractometer, simultaneous differential scanning calorimetry and electrophoretic light scattering spectrophotometer. And the morphologies of the powders and the densified samples were observed by scanning electron microscopy.

Abstract: Soft and porous CaO-SiO2 powders (CaSiO3, Ca2SiO4, Ca3SiO5) were fabricated by organic-inorganic solution technique. Calcium nitrate and Ludox SK silica sol were dissolved in D.I. water and then 5 wt% polyvinyl alcohol solution was added as a polymeric carrier. The metal cations were dispersed well in solution and a homogeneous polymeric network was formed. The organic-inorganic precursor gels were turned to porous powder having volume expansion through an explosive oxidation reaction during calcination process. The polyvinyl alcohol content and heating rate were affected on the explosive reaction behavior. It may be speculated that the reaction between oxygen and unstable calcium cations resulted in the vigorous exothermic reaction and simultaneously the reaction made extensive void, which is accompanied with volume expansion in the powder structure, by the thermal decomposition in a moment of organic substance, polyvinyl alcohol. The porous powders were crystallized at relatively lower temperatures, and the crystalline development was dependent on the polymer content.