共查询到20条相似文献,搜索用时 0 毫秒
1.
Krzysztof Haberko Waldemar Pyda Jan Piekarczyk Miroslaw M. Bucko 《Journal of the American Ceramic Society》1992,75(5):1272-1275
Fully tetragonal and sintered 13 mol% TiO2 ─3 mol% Y2 O3 ─84 mol% ZrO2 was thermally treated at 1300°C for 1 h in argon in the presence of carbon. No phase changes occurred on the as-received surface and in the bulk of the material, but t → m transformation occurred on polished surfaces under reducing conditions, and it resulted in increased fracture toughness, Young's modulus, and modulus of rigidity. Deoxidation of the system occurred and 0.174 wt% of carbon was found in the sample. This seemed to stabilize the tetragonal phase. 相似文献
2.
Alan Bleier Paul F. Becher Kathleen B. Alexander C. Gary Westmoreland 《Journal of the American Ceramic Society》1992,75(10):2649-2658
Aqueous processing of Al2 O3 ─ZrO2 (123 mol% CeO2 ) composites, combined with sintering conditions, was used to control the microstructure and its influence on the martensitic transformation temperature of t -ZrO2 and the transformation-toughening contribution at room temperature. The resultant ZrO2 grain sizes in the dense composites were related to the transformation-toughening behavior of t -ZrO2 . The data show that (1) the best processing conditions exist when the electrophoretic mobilities of the two solids are positive, adequately high to ensure colloidal stability, efficient packing,and uniform ZrO2 distribution but differ greatly in magnitude, (2) the colloidal stability of ZrO2 controls the overall stability and the rheological and processing behavior of this mixture, (3) the grain size distribution in dense pieces sintered for 1 h at 1500°C is comparable to the particle size distribution of the powders, (4) the martensite start temperature for the tetragonal to-monoclinic transformation in Al2 O3 containing 20 and 40 vol% ZrO2 increases and can approach 0°C with increasing average ZrO2 grain size, and as a result, (5) the fracture toughness values at room temperature are raised from 4–5 MPa.m1/2 to 9–12 MPa.m1/2 for these two compositions. 相似文献
3.
The fracture strengths of sintered Al2 O3 containing 20 and 40 vol% ZrO2 (12 mol% CeO2 )—zirconia-toughened alumina (ZTA)—composites along with the fracture resistance can be increased (e.g., to ∼900 MPa and >12 Mpa·m1/2 , respectively), by increasing the mean grain size of the t -ZrO2 (and the Al2 O3 ) from ∼0.5 μm to ∼3 μm. At these lower t -ZrO2 contents, the fracture strength-fracture resistance curves show a continuous rise as opposed to the strength maxima observed in polycrystalline t -ZrO2 (12 mol% CeO2 ), CeTZP, and ZrO2 (12 mol% CeO2 ) ceramics containing ≤20 vol% Al2 O3 . The toughened composites also exhibit excellent damage resistance with fracture strengths of 500 MPa retained with surfaces containing ∼150- N Vickers indentations which produce cracks of ∼160-μm radius. Greater damage resistance correlates with an increase in the apparent R -curve response of these composites. 相似文献
4.
Robert G. Hill Christopher Goat David Wood 《Journal of the American Ceramic Society》1992,75(4):778-785
A SiO2 ─Al2 O3 ─CaO─CaF2 ionomer glass was investigated using thermal analysis, X-ray diffraction, and scanning electron microscopy. The purpose of this investigation was to control the susceptibility of the glass to acid attack. The differential thermal analysis trace exhibited a sharp glass transition at about 645°C and two exotherms. The first exotherm corresponded to liquid–liquid phase separation followed by crystallization of fluorite. The second, much larger, exotherm was the result of crystallization of the remaining glass phase to form anorthite. Prolonged heat treatment below the glass-transition temperature demonstrated that crystallization of fluorite can occur without prior liquid–liquid phase separation. 相似文献
5.
Kazuki Okada Yu-ichi Yoshizawa Taketo Sakuma 《Journal of the American Ceramic Society》1991,74(11):2820-2823
Grain-size distribution in various Al2 O3 ─ZrO2 (2.5 mol% Y2 O3 ) ceramics during high-temperature annealing was examined. In alumina-rich alloys, the grain size of major and minor phases was very different, while grain size was almost uniform in zirconia-rich alloys. This difference in grainsize distribution was related to the difference in grain growth rate of the major phase and to the effectiveness of grain-boundary pinning by minor-phase grains. 相似文献
6.
Yoshio Sakka Yasumichi Oishi Ken Ando Yoji Ikeda 《Journal of the American Ceramic Society》1993,76(5):1381-1383
Zr–Hf interdiffusion was studied in the temperature range of 1650° to 1850°C in air for polycrystalline fluorite-cubic systems of 90CeO2 ·10(Zr1- x Hf x )O2 and 60CeO2 ·40(Zr1- x Hf x )O2 . Lattice and grain-boundary diffusion parameters were calculated from the Zr–Hf concentration distributions by using the grain-boundary diffusion equation of Oishi and Ichimura. The cation iattice diffusivity was close to that in the fluorite-cubic Y2 O2 -ZrO2 solid solution. 相似文献
7.
The compositional range for glass formation below 1600°C in the Sm2 O3 ─Al2 O3 ─SiO2 system is (9–25)Sm2 O3 ─(10–35)Al2 O3 ─(40–75)SiO2 (mol%). Selected properties of the Sm2 O3 ─Al2 O3 ─SiO2 (SmAS) glasses were evaluated as a function of composition. The density, refractive index, microhardness, and thermal expansion coefficient increased as the Sm2 O3 content increased from 9 to 25 mol%, the values exceeding those for fused silica. The dissolution rate in 1 N HCl and in deionized water increased with increasing Sm2 O3 content and with increasing temperature to 70°C. The transformation temperature ( T g ) and dilatometric softening temperature ( T d ) of the SmAS glasses exceeded 800° and 850°C, respectively. 相似文献
8.
Asoke C. D. Chaklader Sankar Das Gupta Edmond C. Y. Lin Boris Gutowski 《Journal of the American Ceramic Society》1992,75(8):2283-2285
Al2 O3 and SiC composite materials have been produced from mixtures of aluminosilicates (both natural minerals and synthetic) and carbon as precursor materials. These composites are produced by heating a mixture of kaolinite (or synthetic aluminosilicates) and carbon in stoichiometric proportion above 1550°C, so that only Al2 O3 and SiC remain as the major phases. A similar process has also been used for synthesizing other composite powders having mixtures of Al2 O3 , SiC, TiC, and ZrO2 in different proportions (all compounds together or selective mixtures of some of them), as desired. The microstructure of hot-pressed dense compacts, produced from these powders, revealed that the SiC phase is distributed very homogeneously, even occasionally within Al2 O3 grains on a nanosize scale. The homogeneous distribution of SiC particles within the system produced high fracture toughness of the hot-pressed material (KIC ∼ 7.0 MPa · m1/2 ) and having Vicker's hardness values greater than 2000 kgf/mm2 . 相似文献
9.
Cristina Leonelli Tiziano Manfredini Mariano Paganelli Gian Carlo Pellacani Jose Luis Amoros Albaro Jose Emilio Enrique Navarro Maria Jose Orts Silvia Bruni Franco Cariati 《Journal of the American Ceramic Society》1991,74(5):983-987
In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li2 O─Al2 O3 ─SiO2 glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, developing a very close network of interlocked crystals of synthetic β-spodumene-silica solid solutions (LiAlSi4 O10 ). The results of this research are expected to establish the conditions under which these glass-ceramic systems can be practically used as tile glazes. 相似文献
10.
Subsolidus Phase Relationships in Part of the System Si,Al,Y/N,O: The System Si3 N4 ─AIN─YN─Al2 O3 ─Y2 O3
Wei-Ying Sun Tseng-Ying Tien Tung-Sheng Yen 《Journal of the American Ceramic Society》1991,74(11):2753-2758
The subsolidus phase relationships in the system Si,Al,Y/N,O were determined. Thirty-nine compatibility tetrahedra were established in the region Si3 N4 ─AIN─Al2 O3 ─Y2 O3 . The subsolidus phase relationships in the region Si3 N4 ─AIN─YN─Y2 O3 have also been studied. Only one compound, 2YN:Si3 N4 , was confirmed in the binary system Si3 N4 ─YN. The solubility limits of the α'─SiAION on the Si3 N4 ─YN:3AIN join were determined to range from m = 1.3 to m = 2.4 in the formula Y m /3 Si12- m Al m N16 . No quinary compound was found. Seven compatibility tetrahedra were established in the region Si3 N4 ─AIN─YN─Y2 O3 . 相似文献
11.
Kazunari Sasaki Petr Bohac Ludwig J. Gauckler 《Journal of the American Ceramic Society》1993,76(3):689-698
Phase equilibria in the system ZrO2 ─InO1.5 have been investigated in the temperature range from 800° to 1700°C Up to 4 mol%, InO1.5 is soluble in t -ZrO2 at 1500°C. The martensitic transformation temperature m → t of ZrO2 containing InO1.5 is compared with that of ZrO2 solid solutions with various other trivalent ions with different ionic radii. The diffusionless c → t ' A phase transformation is discussed. Extended solid solubility from 12.4 ± 0.8 to 56.5 ± 3 mol% InO1.5 is found at 1700°C in the cubic ZrO2 phase. The eutectoid composition and temperature for the decomposition of c -ZrO2 solid solution into t -ZrO2 +InO1.5 solid solutions were determined. A maximum of about 1 mol% ZrO2 is soluble in bcc InO1.5 phase. Metastable supersaturation of ZrO2 in bcc InO 1.5 and conditions for phase separation are discussed. 相似文献
12.
An optimal set of thermodynamic functions for the ZrO2 ─YO1.5 system are obtained using phase diagram and thermodynamic data. The liquid is described by a subregular solution model. Both cubic ZrO2 and YO1.5 solid solutions are regarded as one cubic solution, which is also treated as a subregular solution. The ordered Zr3 Y4 O12 phase is treated as a stoichiometric compound. A regular solution model is applied to the other solid solutions. Tentative equilibrium boundaries between monoclinic and tetragonal ZrO2 solid solutions are evaluated from information about the T 0 line. The calculated phase diagram and thermodynamic functions agree well with experimental data. 相似文献
13.
Takashi Wakasugi Fumitaka Tsukihashi Nobuo Sano 《Journal of the American Ceramic Society》1991,74(7):1650-1653
The BN solubilities for B2 O3 , B2 O3 ─SiO2 , and B2 O3 ─CaO systems have been measured mainly at 1823 K using a graphite crucible. The capability of the systems for nitrogen dissolution is compared with that of silicate systems in terms of nitride capacity. The dependence of nitrogen solubility in molten CaO containing 15 mol% of B2 O3 on oxygen and nitrogen partial pressures is also investigated. It has been found that there are two mechanisms for nitrogen dissolution, namely as chemically bonded nitrogen and as physically dissolved nitrogen gas. 相似文献
14.
15.
Osamu Yamaguchi Masakazu Shirai Masaru Yoshinaka 《Journal of the American Ceramic Society》1988,71(12):510-C
In the system ZrO2 -Al2 O3 , cubic ZrO2 solid solutions containing up to 40 mol% Al2 O3 crystallize at low temperatures from amorphous materials prepared by the simultaneous hydrolysis of zirconium and aluminum alkoxides. The values of the lattice parameter, a, increase linearly from 0.5095 to 0.5129 nm with increasing Al2 O3 content. At higher temperatures, the solid solutions transform into tetragonal ZrO2 and α-Al2 O3 . Pure ZrO2 crystallizes in the tetragonal form at 415° to 440°C. 相似文献
16.
Annealing of ZrO2 -toughened Al2 O3 (ZTA) at elevated temperatures causes growth of both the intergranular ZrO2 particles and the Al2 O3 "matrix" grains. Exaggerated ("breakaway") grain growth occurs in some, but not all, specimens. Analytical electron microscopy of two ZTA's, both of which contained a continuous amorphous (glassy) grain-boundary phase, but only one of which showed breakaway grain growth, revealed that the occurrence of breakaway grain growth could be correlated with the chemistry of the ubiquitous glassy grain-boundary phase. 相似文献
17.
The phase diagram for the CuO-rich part of the La2 O3 ─CuO join was redetermined. La2 Cu2 O5 was found to have a lower limit of stability at 1002°± 5°C and an incongruent melting temperature of ∼1035°C. LagCu7 O19 had both a lower (1012°± 5°C) and an upper (1027°± 5°C) limit of stability. Subsolidus phase relations were studied in the La2 O3 ─CuO─CaO system at 1000°, 1020°, and 1050°C in air. Two ternary phases, La1.9 Ca1.1 Cu2 O5.9 and LaCa2 Cu3 O8.6 , were stable at these temperatures, with three binary phases, Ca2 CuO3 , CaCu2 O3 , and La2 CuO4 . La2 Cu2 O5 and La8 Cu7 O19 were stable only at 1020°C, and did not support solid-solution formation. 相似文献
18.
Mikio Fukuhara 《Journal of the American Ceramic Society》1989,72(2):236-242
The effect of Al2 O3 and (Ti or Si)C additions on various properties of a (Y)TZP (yttria-stabilized tetragonal zirconia polycrystal)–Al2 O3 –(Ti or Si)C ternary composite ceramic were investigated for developing a zirconia-based ceramic stronger than SiC at high temperatures. Adding Al2 O3 to (Y)TZP improved transverse rupture strength and hardness but decreased fracture toughness. This binary composite ceramic revealed a rapid loss of strength with increasing temperature. Adding TiC to the binary ceramic suppressed the decrease in strength at temperatures above 1573 K. The residual tensile stress induced by the differential thermal expansion between ZrO2 and TiC therefore must have inhibited the t - → m -ZrO2 martensitic transformation. It was concluded that a continuous skeleton of TiC prevented grain-boundary sliding between ZrO2 and Al2 O3 . In contrast, for the ternary material containing β-SiC in place of TiC, the strength decreased substantially with increasing temperature because of incomplete formation of the SiC skeleton. 相似文献
19.
The phase composition of fine ZrO2 and ZrO─Y2 O3 powders prepared by the process of spray pyrolysis was detected using XRD. An interesting phenomenon has been observed. In this paper, the influence of the temperature and carrier gas flux on the phase composition of as-prepared powders is described. The formation and transformation mechanisms of the powder phase in the process are also discussed. 相似文献
20.
Michael J. McGarry Ronald A. McCauley 《Journal of the American Ceramic Society》1992,75(10):2874-2876
The subsolidus phase equilibria of the MgO─V2 O5 ─SiO2 system was studied by solid-state reaction and powder X-ray diffractometry. The resulting ternary is discussed with respect to corrosion of magnesia- and silica-containing refractories by vanadium-containing fuels. 相似文献