Accession Number : ADA290562

Title :   High-Toughness Glass-Ceramics.

Descriptive Note : Final rept. 1 Jul 91-30 Jun 94,

Corporate Author : RENSSELAER POLYTECHNIC INST TROY NY DEPT OF MATERIALS ENGINEERING

Personal Author(s) : Tomozana, Minoru

PDF Url : ADA290562

Report Date : 31 AUG 1994

Pagination or Media Count : 10

Abstract : Two different methods were used to prepare tough glass-ceramics containing ZrO2. One was to melt ZrO2-containing Li2O-Al2O3-SiO2 glasses and transform them by control led crystallization. The other was to sinter BaO-SiO2-Al2O3 glass powder together with ZrO2 powder. In both materials, some toughness improvement by the transformation of zirconia during fracture was observed. However, unexpectedly, the greater toughness improvement was realized when the zirconia particles in the glass-ceramics were transformed prior to the fracture by cooling to a lower temperature, e.g., liquid nitrogen temperature. This drastic increase of the fracture toughness was attributed to the deflection of the propagating crack by the large stress fields around the transformed (monoclinic) zirconia. The examination of the fracture surface demonstrated clearly that the crack deflection is taking place in the specimen with transformed zirconia. (MM)

Descriptors :   *CERAMIC MATRIX COMPOSITES, *TOUGHNESS, *GLASS, *CERAMIC MATERIALS, TEMPERATURE, POWDERS, DEFLECTION, CRYSTALLIZATION, COOLING, FRACTURE(MECHANICS), HEAT TREATMENT, CRACK PROPAGATION, MELTING, ZIRCONIUM OXIDES, SINTERING.

Subject Categories : Ceramics, Refractories and Glass
      Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE