Crystallization of Eutectic Microstructures from Oxide and Carbide Melts

The theoretical aspect of the directional solidification :is briefly described. Two different experimental techniques were used for the production of directionally solidified high refractory oxide and carbide eutectics. Microstructure, crystallography, mechanical properties and mechanism of failure were investigated. Some of the inves·tLgated eutectics retain considerable strength at elevated temperature, whereas the majority of alloys and sintered oxide bodies show rapid loss in strength. Eutectic in the system B4C-SiC shows excepti.onally high wear r~sisfance

Crystallization of Eutectic Microstructures from Oxide and Carbide Melts

The theoretical aspect of the directional solidification :is briefly described. Two different experimental techniques were used for the production of directionally solidified high refractory oxide and carbide eutectics. Microstructure, crystallography, mechanical properties and mechanism of failure were investigated. Some of the inves·tLgated eutectics retain considerable strength at elevated temperature, whereas the majority of alloys and sintered oxide bodies show rapid loss in strength. Eutectic in the system B4C-SiC shows excepti.onally high wear r~sisfance

Relative energetics and structural properties of zirconia using a self-consistent tight-binding model

We describe an empirical, self-consistent, orthogonal tight-binding model for zirconia, which allows for the polarizability of the anions at dipole and quadrupole levels and for crystal field splitting of the cation d orbitals. This is achieved by mixing the orbitals of different symmetry on a site with coupling coefficients driven by the Coulomb potentials up to octapole level. The additional forces on atoms due to the self-consistency and polarizabilities are exactly obtained by straightforward electrostatics, by analogy with the Hellmann-Feynman theorem as applied in first-principles calculations. The model correctly orders the zero temperature energies of all zirconia polymorphs. The Zr-O matrix elements of the Hamiltonian, which measure covalency, make a greater contribution than the polarizability to the energy differences between phases. Results for elastic constants of the cubic and tetragonal phases and phonon frequencies of the cubic phase are also presented and compared with some experimental data and first-principles calculations. We suggest that the model will be useful for studying finite temperature effects by means of molecular dynamics.Comment: to be published in Physical Review B (1 march 2000

Effect of Dopants on Zirconia Stabilization—An X-ray Absorption Study: III, Charge-Compensating Dopants

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66100/1/j.1151-2916.1994.tb05404.x.pd