共查询到20条相似文献,搜索用时 15 毫秒
1.
Joanne H. Markis Kevin Clemens Minoru Tomozawa 《Journal of the American Ceramic Society》1981,64(1):20-C-
Immiscibility temperature of 13 mol% Na2 O-87 mol% SiO2 glass was found to increase with F addition. Electron micrographs indicated that the microstructure size did not change appreciably with F addition. 相似文献
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Na2 O-SiO2 glasses with high water contents (up to =72 wt%) were prepared under high-pressure hydrothermal conditions. Hardness, crack initiation, and glass-transition temperature were investigated. The hardness and the glass-transition temperature decreased and the crack initiation threshold increased with increasing water content, which suggests that dissolved water promotes deformation by plastic flow. 相似文献
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《Journal of the American Ceramic Society》1975,58(3-4):147-147
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Sung-Tae Kwon Doh-Yeon Kim Thae-Khapp Kang Duk N. Yoon 《Journal of the American Ceramic Society》1987,70(4):69-C-
Alumina powder compacts sintered at various temperatures were isostatically hot-pressed. The specimens sintered to the closed-pore state can be densified further by hot isostatic pressing. If the open pores are eliminated during sintering, sintering at a low temperature is desirable to achieve a full densification after hot-pressing. Sintering at high temperatures causes pores to be trapped inside the grains; these pores are difficult to eliminate by subsequent hot-pressing. 相似文献
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L. M. FOSTER G. V. CHANDRASHEKHAR J. E. SCARDEFIELD R. B. BRADFORD 《Journal of the American Ceramic Society》1980,63(9-10):509-512
A new phase diagram for the system Na2 O-Ga2 O3 (>50 mol% Ga2 O3 ) is presented. It is based on information from differential thermal analysis, X-ray examination of quenched samples, and a radiochemical technique for determining the compositions of a primary phase and a liquid in equilibrium with it. The diagram provides a guide for the growth of primary crystals of the two ionically conducting sodium gallates that are analogs of the technologically important β- and β"-aluminas. 相似文献
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Ki-Woong Chae Doh-Yeon Kim Byung-Chan Kim Kyung-Bae Kim 《Journal of the American Ceramic Society》1993,76(7):1857-1860
The densification of Al2 O3 –30TiC (in weight percent) composite is investigated as a function of Y2 O3 additions. It is observed that very small amounts of Y2 O3 are effective in aiding the densification. The density was observed to pass through a maximum at 0.35 wt% of Y2 O3 . The gas-generating reaction of Al2 O3 with TiC is likely to be suppressed by the addition of Y2 O3 . 相似文献
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Günther H. Frischat Wolfgang Krause Horst Hübenthal 《Journal of the American Ceramic Society》1984,67(1):10-C-
Up to 3.3 wt% nitrogen can be incorporated into Na2 O-B2 O3 glass melts. The melting procedure is described, and structure models are given. In contrast to N-containing silicate glasses, the borate glasses were transparent; however, micrographs of their fracture surfaces showed some crystallinity. Properties were determined as a function of the N and Na2 O contents of the glasses. Compared with N-containing silicate glasses, the properties of borate glasses are much less changed by the nitrogen introduced. 相似文献
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Donald B. Dingwell 《Journal of the American Ceramic Society》1992,75(6):1656-1657
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The dynamic stress intensity factors, which were determined with newly developed bar impact facilities and a new data reduction procedure, for an Al2 O3 ceramic and 29 vol% SiCw /Al2 O3 composite were virtually identical, thus indicating that the short SiC whiskers were ineffective under dynamic fracture. SEM studies revealed five distinct fracture morphologies with increased percentage area of transgranular fracture in both materials with rapid crack propagation. Also, the high dynamic stress intensity factor caused multiple microscopic crack planes to form and then join as the crack advanced. 相似文献
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Manuel Belmonte Jose S. Moya Pilar Miranzo 《Journal of the American Ceramic Society》1995,78(6):1661-1667
The sintering behavior of an Al2 O3 compact containing uniformly dispersed Al2 O3 platelets has been investigated. The results reveal a significant decrease in the sintering rate as well as the formation of voids and cracklike defects in the presence of nonsinterable platelets. The addition of a small amount (2 vol%) of tetragonal-ZrO2 particles enhances the sintering rate, increases end-point density (∼99.5% of theoretical density) and prevents formation of sintering defects. 相似文献
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Subsolidus phase relationships in the Ga2 O3 –Al2 O3 –TiO2 system at 1400°C were studied using X-ray diffraction. Phases present in the pseudoternary system include TiO2 (rutile), Ga2−2 x Al2 x O3 ( x ≤0.78 β-gallia structure), Al2−2 y Ga2 y O3 ( y ≤0.12 corundum structure), Ga2−2 x Al2 x TiO5 (0≤ x ≤1 pseudobrookite structure), and several β-gallia rutile intergrowths that can be expressed as Ga4−4 x Al4 x Ti n −4 O2 n −2 ( x ≤0.3, 15≤ n ≤33). This study showed no evidence to confirm that aluminum substitution of gallium stabilizes the n =7 β-gallia–rutile intergrowth as has been mentioned in previous work. 相似文献
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The thermal stress resistance of aluminas is strongly influenced by the surface heat transfer coefficient (h). In liquid quenches, h, which is a function of boiling phenomena, varies with bath and sample temperature. Thus, while a 22°C water quench yields ΔTc values essentially independent of the alumina properties or correspondingly, sample thickness, t, raising the bath to 100°C leads to a strong size dependence of ΔTc (i.e. ΔTc >> ∼250°C for t<1.8 mm). 相似文献
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Pertinent works of previous investigators are reviewed briefly. A superior technique for the preparation of experimental glasses of high purity and chemical homogeneity is presented. Devitrification growth-rate data and traction-viscosity data are reported for high-silica glasses of the system Al2 O3 -SiO2 . Glasses with added Al2 O3 were found to devitrify to cristobalite more rapidly than ultrapure silica glasses at a given temperature, and yet their fluidities (i.e., reciprocal viscosities) were found to be less. The devitrification growth rate, g, was found to be of zero order and to follow the temperature dependence In( g/T ) = -(B/T) + In A over the temperature range 1561°K. T 1730°K. 相似文献
15.
The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated. 相似文献
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Debao Zhang Baoyu Chen Zhuping Liu Shunguang Li Lili Hu 《Journal of the American Ceramic Society》2004,87(12):2228-2231
Er3+ -doped sodium lanthanum aluminosilicate glasses with compositions of (90− x )(0.7SiO2 ·0.3Al2 O3 )· x Na2 O·8.2La2 O3 · 0.6Er2 O3 ·0.2Yb2 O3 ·1Sb2 O3 (in mol%) ( x = 12, 20, 24, 40, 60 mol%) were prepared and their spectroscopic properties were investigated. Judd–Ofelt analysis was used to calculate spectroscopic properties of all glasses. The Judd–Ofelt intensity parameter Ω t ( t = 2, 4, 6) decreases with increasing Na2 O. Ω2 decreases rapidly with increasing Na2 O while Ω4 and Ω6 decrease slowly. Both the fluorescent lifetime and the radiative transition rate increase with increasing Na2 O. Fluorescence spectra of the 4 I 13/2 to 4 I 15/2 transition have been measured and the change with Na2 O content is discussed. It is found that the full width at half-maximum decreases with increasing Na2 O. 相似文献
18.
Ryan K. Roeder Kevin P. Trumble Keith J. Bowman' 《Journal of the American Ceramic Society》1997,80(1):27-36
Composites containing Ce-ZrO2 , Al2 O3 , and aligned Al2 O3 platelets were produced by centrifugal consolidation and pressureless sintering, followed by heat treatments at 1600°C for varied duration. Constituents in the consolidated microstructures were either uniformly distributed throughout or segregated into gradient layers, depending critically on platelet content. Quantitative image analysis was used to examine microstructure development with heat treatment. Changes in the volume fraction, dimensional anisotropy, and gradient of pores and platelets, as well as changes in the phase gradient, were quantified. Microstructure development was strongly dependent on the initial microstructure design attained from suspension processing. 相似文献
19.
Oxide crystallite formation and growth from freeze-dried sulfates were studied for the representative materials Al2 O3 and Fe2 O3 . Transmission and scanning electron micrographs showed the formation and growth of chainlike aggregates of crystallites. Aggregation occurred as part of the nucleation and growth of the oxide, and discrete oxide particles were never present. Orientation of the chain aggregates was related to the ice structure formed during freezing. X-ray line broadening data showed that crystallite size is a function of the 1/5 to 1/7 power of time for isothermal treatments. A qualitative analysis of material transport favored the surface diffusion mechanism. 相似文献
20.
Doreen D. Edwards Pollyanna E. Folkins Thomas O. Mason 《Journal of the American Ceramic Society》1997,80(1):253-257
Subsolidus phase relationships in the Ga2 O3 –In2 O3 system were studied by X-ray diffraction and electron probe microanalysis (EPMA) for the temperature range of 800°–1400°C. The solubility limit of In2 O3 in the β-gallia structure decreases with increasing temperature from 44.1 ± 0.5 mol% at 1000°C to 41.4 ± 0.5 mol% at 1400°C. The solubility limit of Ga2 O3 in cubic In2 O3 increases with temperature from 4.X ± 0.5 mol% at 1000°C to 10.0 ± 0.5 mol% at 1400°C. The previously reported transparent conducting oxide phase in the Ga-In-O system cannot be GaInO3 , which is not stable, but is likely the In-doped β-Ga2 O3 solid solution. 相似文献