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Sintering and Heterogeneous Catalysis (Proceedings of the Sixth International Conference on Sintering and Related Phenomena). This Conference was also the 20th Conference on ceramic sciences.

作者： Messing, G.L. Selcuker, A.R. Bradt, R.C. Pennsylvania State Univ Ceramic Science & Engineering Program University Park PA USA Pennsylvania State Univ Ceramic Science & Engineering Program University Park PA USA

ISBN: (纸本)0306416662

The densification by the reactive phase calsintering of a compact formed from an oxide precursor is presented. The essential features of the process are the development of a reactive, high surface area matrix upon calcination of the precursor and the presence of a reactive liquid phase during sintering. The densification process is described for Fe//2O//3 doped dolomite in terms of the elimination of intra-aggregate and interaggregate porosities via liquid phase sintering. It is demonstrated that high densities ( greater than equivalent to 95%) and rapid sintering kinetics can be obtained with coarse ( greater than 10 mu m) precursor powders.

关键词： ceramic materials

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EFFECT OF ALKALI HYDROXIDES ON THE STRENGTH AND FATIGUE OF FUSED-SILICA OPTICAL FIBER

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JOURNAL OF THE AMERICAN ceramic SOCIETY 1991年第10期74卷 2592-2598页

作者： MATTHEWSON, MJ RONDINELLA, VV LIN, BC KEYES, SW Fiber Optic Materials Research Program Department of Ceramic Science and Engineering Rutgers University Piscataway New Jersey 08855-0909

A two-point bend technique is used to determine the strength of "pristine" bare fused silica optical fiber in aqueous solutions of the group I alkali metal hydroxides (Li through Cs) in the concentration range 10(-4)N to 1N (pH range 10 to 14). In the highest concentration solutions, a strong cation effect is exhibited with a minimum strength for KOH while fibers in LiOH and CsOH are typically 20% and 10% stronger, respectively. The cation effect decreases with decreasing concentration until at 10(-4)N no effect is apparent. Tetramethylammonium hydroxide gives intermediate strengths between CsOH and LiOH. The results correlate closely with published results for the dissolution rate of silica which exhibit a maximum rate for KOH. In contrast, the results do not correlate with published subcritical crack growth data which show no cation effect for Na through Cs. These results support the pit etching model for pristine fiber strength proposed by Kurkjian et al. and argue against the presence of cracks or cracklike objects in these materials.

关键词： optical fibers strength fatigue alkalies hydroxides

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Multiple-Mist Regions on Glass Fracture Surfaces

Multiple-Mist Regions on Glass Fracture Surfaces

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1979 Symposium on Fractography and Materials science

作者： Abdel-Latif, A.I.A. Bradt, R.C. Tressler, R.E. Materials Engineering General Electric Co. Valley Forge Space Division PhiladelphiaPA19101 United States Ceramic Science and Engineering Department of Materials Science and Engineering Ceramic Science and Engineering Ceramic Science Program Pennsylvania State University University ParkPA16802 United States

ISBN: (纸本)9780803107335

Observations of the formation of multiple-mist regions on the fracture surfaces of soda-lime-silicate and fused silica glasses are reported. These regions occur only in high-strength specimens. The same empirical equation that is applicable to the basic fracture mirror-primary mist also describes secondary and tertiary mist regions, although the proportionality constants increase as the order of the mist region increases. Results suggest that these mist radii constants may be related in specific ratios, which decrease with successive mist regions. Criteria of mist-region formation are reviewed with respect to additional restrictions imposed by the consideration of multiple mists. The authors suggest that an energy criterion is most applicable, and a schematic diagram is proposed. Copyright © 1981 by AS FM International.

关键词： Fracture

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A GRUNEISEN RELATION ON CONSTANT-PRESSURE LINES

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JOURNAL OF THE AMERICAN ceramic SOCIETY 1992年第12期75卷 3341-3345页

作者： BURNS, SJ DAHAKE, G DING, Z KUDALLUR, S KUMAR, S LI, KJ SRINIVASAN, R STACK, K VENKATARAMAN, N WANG, C YANG, FQ ZHOU, YY Materials Science Program Department of Mechanical Engineering University of Rochester Rochester New York 14627–0133 Member American Ceramic Society.

Gruneisen's constant, gamma, is ideally temperature-independent on constant-volume lines;a similar constant, lambda, which is ideally temperature-independent on isobaric lines, has been found. The comparison between gamma and lambda shows that both expressions contain the ratio of the volumetric thermal expansion coefficient to the specific heat capacity;gamma has an additional temperature dependence due to the thermal part of the compressibility, whereas lambda has only a slight thermal component due to the volume per unit mass. Lambda has been chosen so that lambda = gamma at the point where the temperature and pressure are both zero. For most materials it is expected that lambda greater-than-or-equal-to gamma with a different temperature dependence. It is shown empirically for a selection of ceramics that lambda is nearly temperature-independent and has a value between 0.7 and 1.4.

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UNIFORM HYDROLYSIS OF METAL ALKOXIDES VIA HOMOGENEOUS GENERATION OF WATER

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JOURNAL OF NON-CRYSTALLINE SOLIDS 1991年第2-3期135卷 259-264页

作者： LEAUSTIC, A RIMAN, RE Fiber Optic Materials Research Program Department of Ceramic Science and Engineering Rutgers The State University PO Box 909 Piscataway NJ 08855-0909 USA

In situ polymerization of titanium, silicon, zirconium, and aluminum-zirconium alkoxides was accomplished via homogeneous generation of water. Tertiary alcohol dehydration, pinacol rearrangement, esterification, amide synthesis/decomposition, and Hoffman degradation (quaternary ammonium hydroxide base decomposition) were the potential water-generating methods examined. Using tertiary alcohol dehydration or esterification reactions, it was possible to synthesize gels and powders. Some physical and chemical characteristics of these materials are reported.

关键词： Oxides

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Sol-gel synthesis of rare-earth-doped lanthanum halides for highly efficient 1.3-mu m optical amplification

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OPTICS LETTERS 1997年第10期22卷 691-693页

作者： Ballato, O Riman, RE Snitzer, E Fiber Optic Materials Research Program Department of Ceramic Science and Engineering Rutgers The State University of New Jersey Brett and Bowser Roads Piscataway New Jersey 08855-0909

Praseodymium- and dysprosium-doped lanthanum halide powders have been synthesized by a sol-gel-reactive-atmosphere approach. Emission at 1.3 mu m from a sol-gel-derived material was observed for the first time to our knowledge. Measured lifetimes corresponded to radiative quantum efficiencies of approximately 8% for Pr3+:LaF3, 78% for Pr3+:LaCl3, and 78% for Dy3+:LaCl3. The spectroscopic properties of these hosts are shown to be comparable with those of melt-grown single-crystal analogs, verifying the ability of inexpensive and low-temperature solution-based methodologies to produce low-phonon-energy materials. (C) 1997 Optical Society of America.

关键词： Erbium doped fiber amplifiers Fluorescent materials Optical amplification Optical amplifiers Ti:sapphire lasers X ray diffraction

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Fracture Mist Region in a Soda-Lime-Silica Float Glass

Fracture Mist Region in a Soda-Lime-Silica Float Glass

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1982 Symposium on Fractography of ceramic and Metal Failures

作者： Ball, M.J. Landini, D.J. Bradt, R.C. Ceramic Science and Engineering Program Department of Materials Science and Engineering Pennsylvania State University University ParkPA16802 United States

ISBN: (纸本)9780803102156

The mist region near the fracture origin was studied in a series of soda-lime-silica float glass specimens ranging in strength from about 30 to 90 MPa. Both the mirror/mist and the mist/hackle radii were measured to ascertain the dependence of the width of the mist region on the strength level. The mirror/mist constant was found to be 1.80±0.15 MN/m3/2 and the mist/hackle constant to be 2.42±0.16 MN/m3/2. Both analytically and experimentally, the width of the mist region was found to be inversely related to the square of the fracture stress;that is, (Wmist) is proportional to (1/σ2f). This suggests a dependence of the mist region width on the elastic strain energy at fracture initiation. The surface topography of the mist region was analyzed by a scanning electron microscopy computerized contour mapping technique to determine the surface roughness within the mist region. It was observed that the average root-mean-square roughness in the mist region was proportional to the fracture stress squared. This suggests that the fracture surface roughness of the mist region, or alternatively the true surface area of the mist region, is also determined by the stored elastic strain energy in the specimen before fracture. It is concluded that the mist region width and the mist region roughness are both determined by a strain energy criterion. It is suggested that they may be related through a generalized mist region parameter. Copyright © 1984 by ASTM International.

关键词： Glass

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Elevated temperature instrumented Charpy impact of a sintered silicon carbide

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ceramics International 1983年第4期9卷 114-118页

作者： Chandan, H.C. Hermansson, L. Abe, H. Bradt, R.C. Ceramic Science and Engineering Program Department of Materials Sciences and Engineering The Pennsylvania State University University Park PA 16802 United States

A commercially available, densely sintered alpha silicon carbide was tested in air from room temperature to 1700°C using a modified instrumented pendulum unit and standard Charpy size test specimens. The resistance heated silicon carbide specimens exhibited only elastic behavior, even at 1700°C. A compliance analysis of the test revealed a linear elastic decrease of the absorbed impact energy and also a decrease of the fracture stress of the silicon carbide with increasing temperature. © 1983.

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NONLINEAR HERTZIAN INDENTATION FRACTURE-MECHANICS

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JOURNAL OF THE AMERICAN ceramic SOCIETY 1995年第9期78卷 2321-2327页

作者： BURNS, SJ CHIA, KY Materials Science Program Department of Mechanical Engineering University of Rochester Rochester New York 14627–0133 Member American Ceramic Society. Standard Ceramics Inc. Alfred New York 14802–0848.

Indentation cracking under blunt indenters is analyzed using nonlinear fracture mechanics. The usual assumptions of linear elastic fracture mechanics have been replaced with a nonlinear load vs load-point displacement curve while assuming the material is linear elastic, The load, the load-point displacement, and a function of the crack area have been related to the crack driving force, J, while assuming a cone fracture under the Hertzian sphere, Experimentally, it was found that the load-displacement curve during loading, cracking, and unloading is nonlinear. The crack length is empirically shown to be proportional to the load-point displacement for several indenters, The experimentally measured relations between indenter load, load-point displacement, and crack geometries are then analyzed with mechanical energy balances based on the similitude of crack lengths with load-point displacements. The Hertz hardness that describes the nonlinear load vs load-point displacement relation during cracking is derived on the constant J line in load-displacement space. Finally, well-known experimental expressions that relate load to crack length are shown to be indistinguishable from the load-point displacement analysis reported.

关键词： Fracture mechanics

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NONLINEAR COMPLIANCE TESTING APPLIED TO INDENTATION CRACKING IN ceramicS

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JOURNAL OF THE AMERICAN ceramic SOCIETY 1995年第9期78卷 2328-2334页

Indentation cracking under sharp-pointed indenters is analyzed using compliance-based, nonlinear, fracture mechanics, The stress intensity factor, K, in linear elastic fracture mechanics is well known to be proportional to the load, P;in this nonlinear analysis K is proportional to P-3/4. The observed relation between indenter load-point displacement and crack length is based on similitude of crack lengths with load-point displacements as a strain-controlled fracture. The equations that relate load and a function of the crack length to the crack driving force, J, have been found for Vickers indentations. Analysis of the nonlinear load vs displacement assumes an equilibrium crack in the elastic material surrounding the indent, The hardness that describes the load vs load-point displacement during cracking is derived on a constant J line in load-displacement space. The crack length is shown experimentally to be proportional to the load-point displacement after crack initiation for several different indenters in ZnS. The measured loading curves are nonlinear and display crack initiation during loading, The K-Ic expressions found here are very similar to correlations that have been applied to indentation cracks.

关键词： ceramic materials

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