摘要:

Letter ofTransmittalThis paper is part of the proceedings of the Standard Testing Procedure Committee of the Glass Container Association of America. The reasons that caused the Committee to ask for a more or less formal statement of what was known on this subject will be apparent from the paper itself. The members of the Committee, namely, Mr. Bowes, Mr. Flint, Mr. Hiller, Mr. Lyon, and Mr. Roche, as well as Mr. Hendrickson, Mr. Lester, myself, and various others associated with the Committee, have read the paper and offered criticisms. Although we do not necessarily, either as individuals or as a Committee, concur in all that is said, we believe that the paper offers a new approach to some difficult problems connected with strength, a primary concern of the Committee, and that it may act as a basis for industrial advances or for further contributions by others outside the Committee.V. L. Hall,Secretary, GlassContainerAssociation

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05481.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05482.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The rate processes which occur during anodic bonding are modeled using data from various studies. For a given materials system, the process occurs at constant total charge transfer. The observed activation energies are consistent with dc conduction in the glass. The charge transfer required for bonding to aluminum anodes decreases with increasing alkali content of the glass, which is probably due to increasing solubility and mobility of aluminum in depletion layers with higher vacancy contents. The voltage required for bonding at constant time and varying temperature is also consistent with constant charge transfer. The kinetic data are consistent with an electrochemical oxidation model where the rate of bonding is limited by the rate of establishment of the depletion layer.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05483.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Aqueous processing of Al2O3─ZrO2(123 mol% CeO2) composites, combined with sintering conditions, was used to control the microstructure and its influence on the martensitic transformation temperature oft‐ZrO2and the transformation‐toughening contribution at room temperature. The resultant ZrO2grain sizes in the dense composites were related to the transformation‐toughening behavior oft‐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 ZrO2distribution but differ greatly in magnitude, (2) the colloidal stability of ZrO2controls 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 Al2O3containing 20 and 40 vol% ZrO2increases and can approach 0°C with increasing average ZrO2grain size, and as a result, (5) the fracture toughness values at room temperature are raised from 4–5 MPa.m1/2to 9–12 MPa.m1/2for these

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05484.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

When partially sintered cubic ZrO2–10 mol% Y2O3specimens are heat‐treated at 1500°C with powder mixtures of MgO and ZrO2–10Y2O3at varying ratios, the grain boundaries migrate, leaving behind new solid solutions enriched with MgO but depleted of Y2O3. With increasing MgO content in the solute source powder, the average migration velocity increases, and the MgO content increases and the Y2O3content decreases slightly in these new solid solutions. With increasing MgO content in the solute source, the grain boundaries tend to be corrugated and faceted. Migration reversal is also observed at the corrugated boundaries. These variations of the grain boundary migration behavior with the MgO content in the solute source are consistent with the diffusional coherency strain energy as the driving force for the mig

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05485.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Stoichiometric albite glass (NaAlSi3O8) was seeded with 5 wt% crystalline anorthite (CaAl2Si2O8) to make albite glass‐ceramics. The epitaxial crystallization of the albite glass to the glass‐ceramics was investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). High albite was observed as the major crystallization product over the temperature range of 800–1200°C. No crystalline albite could be crystallized frompurealbite glass without seeds. Small amounts of nepheline (NaAlSiO4), however, crystallized along with albite after heat treatments at temperatures lower than 1000°C. The platelike microstructure of albite crystals was revealed in the seeded glasses. The albite blades grew epitaxially from the anorthite seeds, and the Ca content decreased in the direction away from the seeds. The degree of crystallization and the grain size were dependent upon the heat treatment conditions. By increasing the particle size of the seed, the crystallization process was retarded and the resultant microstructure was degraded. The seeding efficiency was also lowered by adding nonisostructural hexagonal anorthite seeds which produced less albite but more nepheline crystals. Crystallization of albite glass by seeding with 5 wt% anorthite is much greater than with the surface nucleation which takes place in a homogeneous 95 wt% albite + 5 wt% anorth

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05486.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The isothermal oxidation of HfC powders was carried out at temperatures of 480° to 600°C at oxygen pressure of 4, 8, and 16 kPa, using an electromicrobalance. The oxidized product was identified by X‐ray analysis, Raman spectroscopy, X‐ray photoelectron spectroscopy, and electron diffraction, and the morphology of the oxidized grains was observed by scanning electron microscopy. Oxidation proceeds by two processes: a diffusion‐controlled process operates up to about 50% oxidation and a phase‐boundary‐controlled process operates above about 50% oxidation. The activation energies for both processes are the same (197 ± 15 kJ.mol−1). The change in the oxidation process is associated with the generation of cracks on the grains, resulting from the growth or expansion stress due to the formation of monoclinic HfO2microcrystallites less than 3 nm in size. In the latter process, the thickness of the diffusion layer is kept constant, being time‐independent, which allows the process to apparently obey the phase‐boundary

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05487.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A calculational thermodynamic investigation of the chemical vapor deposition (CVD) of YBa2Cu3O7−xfrom organometallic precursors has been performed, based on the minimization of the Gibbs energy of the Y‐Ba‐Cu‐C‐O‐H chemical system. Thermodynamic data for the participating compounds were selected after a critical assessment of the available thermochemical information and are self‐consistent with an accepted phase diagram. The results are presented in CVD diagrams which illustrate the influence of the most commonly used operating conditions of temperature, pressure, and initial gas composition on the formation of

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05488.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Quantitative fractography is often used to study material failure mechanisms. During calculation of surface or profile roughness parameters, the magnification used in obtaining fractographic data is found to influence the value of the parameters. Fractal geometry has been developed into a tool capable of defining surface and profile topography without sensitivity to magnification, and several studies have related fractal dimension (DF) to other physical or mechanical properties. In this study, we obtained the fractal dimension of profiled fracture surfaces of one glass and three proprietary dental porcelains. The fracture toughness (K1c) of these materials was also measured using the indentation‐strength method. Results show the surfaces to be fractal. No quantitative relationship between fractal dimension and toughness was found. Differences inK1cwere demonstrated between some materials. It is postulated that the size range within which fractal dimension can be defined as constant is dependent on the toughening mechanism, and that the relationship betweenKIcandDFcannot be identical for all material

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05489.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The compressive stress–strain relation in optical fiber, which is important for a fiber during bending, is shown experimentally to be an asymmetric continuation of the already known nonlinear relation in the tensile region. Measured strengths of optical fibers in fatigue experiments can be 50% higher because of nonlinear corrections. Consequently decreases in measured corrosion susceptibilities, up to 10%, result in estimated fiber lifetimes, which decrease by an order of magnitude. The elastic line of a fiber inserted in a two‐point‐bending testing apparatus, however, is hardly influenced by nonlinear elastic ef

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb05490.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY