Stabilization of tetragonal phase in polycrystalline zirconia

Westinghouse Research Laboratories
Journal of Materials Science (Impact Factor: 2.31). 11/1977; 12(12):2421-2426. DOI: 10.1007/BF00553928

ABSTRACT It is shown that the tetragonal phase can be stabilized in the sintered body of a partially stabilized zirconia (PSZ) containing low concentrations of yttria. Such sintered body containing the metastable phase undergoes stress-induced phase transformation by the absorption of thermal or mechanical stress and exhibits strengths in excess of 690 MPa (100ksi).

1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dense un-doped monoclinic ZrO2 (m-ZrO2) compacts were prepared successfully by microwave sintering with a TE666 resonant mode and temperature ranges from 1350 degrees C to 1550 degrees C. XRD and SEM techniques were used to characterize the samples. A dense and homogeneous microstructure was observed with the grain size of 1 pm, which is smaller than that of conventional sintered ones. A monoclinic ZrO2 phase without detectable tetragonal ZrO2 (t-ZrO2) was found for both microwave sintered and conventional sintered samples. Density of samples was measured according to the Archimedes principle. The results showed a relative density of 99.0% for microwave sintered samples which is higher than that of conventional sintered ones. The microhardness was investigated by indentation test with the highest value of 4.0 GPa. Meanwhile, microcracks were observed on the edges of the indentation but not at the tips for microwave sintered samples which indicated good toughness. Optimized microwave sintering temperature of m-ZrO2 compacts was 1450 degrees C for 30 min with the microhardness of 4.0 GPa and relative density of 99.0%.
    Ceramics International 08/2014; 40(7-7, Part B):10483-10488. DOI:10.1016/j.ceramint.2014.03.019 · 2.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In reaction sintering of silicon carbide, newly formed grains bind the already existing grains in a compact of silicon carbide and carbon mixture under heating in an atmosphere of silicon vapour. Powders of silicon carbide were prepared and characterized for specific surface area, average particle size and size distribution. The compaction characteristics of the mixtures of different silicon carbide and carbon powders and the optimum compaction pressures for bringing about proper “siliciding” (reaction of silicon vapour and particulate carbon) were studied and evaluated. Siliciding studies were carried out in the temperature range of 1500°–2000°C in argon atmosphere at pressures from 760 torr to 10−1 torr. The sintered specimens were characterized for bulk density by water displacement method and completion of reaction by X-ray diffraction. Sintered densities of the order of 80–85% of the theoretical value could be obtained by optimizing argon partial pressure and increasing the reaction temperature to 2000°C. XRD investigations revealed that a small amount of free silicon was always left behind in the matrix.
    Transactions - Indian Ceramic Society 05/2014; 48(6):107-114. DOI:10.1080/0371750X.1989.10822959 · 0.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper the problem of transformation toughening in anisotropic solids is addressed in the framework of Stroh formalism. The fundamental solutions for a transformed strain nucleus located in an infinite anisotropic elastic plane are derived first. Furthermore, the solution for the interaction of a crack tip with a residual strain nucleus is obtained. On the basis of these expressions, fundamental formulations are presented for the toughening arising from transformations using the Green's function method. Finally, a representative example is studied to demonstrate the relevance of the fundamental formulation.
    Journal of Applied Mechanics 09/2013; 80(5):051001. DOI:10.1115/1.4023476 · 1.40 Impact Factor