졸-겔법으로 제조한 ZrO2·SiO2계 결정화 유리의 결정화 및 파괴인성에 관한 연구

A Study of Crystallization and Fracture Toughness of Glass Ceramics in the ZrO2·SiO2 Systems Prepared by the Sol-Gel Method

  • 신대용 (강원대학교 신소재공학과) ;
  • 한상목 (강원대학교 신소재공학과) ;
  • 강위수 (강원대학교 농업기계공학전공)
  • 발행 : 2000.06.30

초록

Precursor gels with the composition of $xZrO_2{\cdot}(100-x)SiO_2$ systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence on tetragonal to monoclinic transformation of $ZrO_2$ was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal $ZrO_2$ occurred through 3-dimensional diffusion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about $310{\sim}325{\pm}10kJ/mol$. The growth of $t-ZrO_2$, in proportion to the cube of radius, increased with increasing heating temperature and heat-treatment time. It was suggested that the diffusion of Zr4+ions by Ostwald ripening was rate-limiting process for the growth of $t-ZrO_2$ crystallite size. The fracture toughness of $xZrO_2{\cdot}(100-x)SiO_2$ systems glass ceramics increased with increasing crystallite size of $t-ZrO_2$. The fracture toughness of $30ZrO_2{\cdot}70SiO_2$ system glass ceramics heated at $1,100^{\circ}C$ for 5 h was $4.84Mpam^{1/2}$ at a critical crystaliite size of 40 nm.

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