Polymer Solution Route for Synthesis of Nano-Sized, SiO₂ Based Ceramic Powders

Nano-sized SiO₂ based powders were fabricated by a polymer solution technique. Nitrate metal sources and Ludox series silica sol were dissolved in D.I. water and then polyvinyl alcohol solution was added as a polymeric carrier. The metal cations were dispersed well in the solution and a homogeneous polymeric network was formed. The organic-inorganic precursor gels were turned to a porous powder with expanded volume through an explosive oxidation reaction during calcination process. The polymer molecular weight, polymer content and heating rate affected the particle agglomeration and size. The reaction between oxygen and unstable metal cations resulted in a vigorous exothermic reaction and simultaneously the reaction created extensive voids, which accompanied soft powders. The porous powders were crystallized at relatively lower temperature, and easily ground to a very fine powder having nano-sized particles. The crystalline development was also dependent on the polymer type, and the weak hydrogen bonding by optimum polymer content promoted homogeneous entrapment between the -(OH) hydroxyl groups and cations, which are solvates by water molecules.