Hydroxylapatite-zirconia composites: Thermal stability of phases and sinterability as related to the CaO-ZrO(2)phase diagram

Evis, Zafer
Doremus, RH
Composites of hydroxylapatite ( HA) with pure zirconia, and 3 and 8% Y2O3 in zirconia, were pressure-less sintered at temperatures from 900 to 1300 degrees C, and hot-pressed at 1200 degrees C in argon gas atmosphere for 1 h. The reactions and transformations of phases were monitored with X-ray diffraction and thermal analysis. At sintering temperatures higher than 1000 degrees C, calcium from HA diffused into the zirconia phase, and the HA phase decomposed to tri-calcium phosphate (TCP). Above about 1200 degrees C, CaZrO3 was formed. These reactions and transformations were interpreted in terms of the ZrO2-CaO phase diagram. On the other hand, zirconia and hydroxylapatite phases in hot pressed composite remained mainly stable suggesting that air in the sintering environment increased the reactivity between the phases. The highest densification was found in a composite initially containing 10% monoclinic ZrO2 sintered at 1300 degrees C. The densification of the composites decreased at lower sintering temperatures and higher zirconia contents upon air-sintering. (C) 2005 Springer Science + Business Media, Inc.


Hot-pressed hydroxylapatite/monoclinic zirconia composites with improved mechanical properties
Evis, Zafer (Springer Science and Business Media LLC, 2007-04-01)
Composites of hydroxylapatite (HA) and monoclinic zirconia were hot-pressed at 1100 degrees C and 1200 degrees C under vacuum to study the phase transformations and the mechanical properties. X-ray diffraction results showed a higher phase transformation from monoclinic-ZrO2 to tetragonal-ZrO2 when the sintering temperature increased from 1100 degrees C to 1200 degrees C. HA decomposed faster when the amount of ZrO2 in the composites increased. Moreover, small amount of alpha-TCP and CaZrO3 was observed in ...
Trapping centers and their distribution in Tl2InGaSe4 single crystals by thermally stimulated luminescence
Delice, S.; IŞIK, MEHMET; Hasanlı, Nızamı (Springer Science and Business Media LLC, 2014-03-01)
Thermoluminescence (TL) measurements in Tl2InGaSe4-layered single crystals have been carried out in the temperature range of 10-200 K at various heating rates (0.2-1.0 K s(-1)) to get information about the characteristics of traps. Two TL overlapping glow peaks related to defect levels have been clearly observed. Thermal cleaning procedure was applied to the glow curves to separate overlapped peaks. Initial rise, peak shape, and heating rate methods were used to calculate the activation energies of the reve...
Sintering and humidity-sensitive behaviour of the ZnCr2O4-K2CrO4 ceramic system
Bayhan, M; Hashemi, T; Brinkman, AW (Springer Science and Business Media LLC, 1997-12-15)
Solid state reaction at elevated temperatures and the sintering behaviour of zinc chromite formed by zinc oxide and chromite oxide were investigated. Crystalline structure, surface and fractured morphologies and humidity-sensitivity characteristics of ZnCr2O4-K2CrO4-CuO were studied. The fired ceramic body, which proved to be mainly constructed from ZnCr2O4 spinel grains, was porous. The humidity characteristics of the sensor showed that the resistance decreased as a logarithmic function with an increase in...
Electrical conductivity and Hall mobility in p-type TlGaSe2 crystals
Qasrawi, AF; Hasanlı, Nızamı (Elsevier BV, 2004-07-02)
Systematic dark electrical conductivity and Hall mobility measurements have been carried out in the temperature range of 200-350 K on p-type TlGaSe2 crystals. The analysis of the temperature-dependent electrical conductivity and carrier concentration reveals the extrinsic type of conduction with an acceptor impurity level located at 0.33 eV, and donor and acceptor concentrations of 9.0 x 10(15) and 1.3 x 10(16) cm(-3), respectively. A hole and electron effective masses of 0.520m(0) and 0.325m(0), respective...
KOC, R; ANDERSON, HU (Springer Science and Business Media LLC, 1992-10-15)
Electrical conductivity and Seebeck coefficients of (La, Ca) (Cr, Co) O3 were measured as a function of temperature. The electrical conductivity as measured in air from 100 to 1100-degrees-C increased with increasing Co and Ca content. The Seebeck coefficients were positive, indicating p-type conductivity. The substitution of Co for Cr significantly decreased the Seebeck coefficients, indicating that the substitution resulted in an increase in site occupancy, associated with the Co. The additional Ca substi...
Citation Formats
Z. Evis and R. Doremus, “Hydroxylapatite-zirconia composites: Thermal stability of phases and sinterability as related to the CaO-ZrO(2)phase diagram,” JOURNAL OF MATERIALS SCIENCE, pp. 1127–1134, 2005, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/42092.