ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11987a.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The effect of chemical bonding between phases of a glass matrix‐metal composite on strength and fracture behavior was investigated. When no chemical bonding occurs, strengthening can be achieved through the mechanical formation of an interface between the dispersant and matrix. Even greater strengthening can be obtained by the formation of a chemical bond. Strengthening occurs by the limitation of the Griffith flaw size and is controlled by micromechanical stress concentrations developed on loading. Internal stresses developed on cooling from the fabrication temperature control the path of fracture. A chemical bond counteracts the micromechanical stress concentration and therefore increases the strengt

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11989.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The extents of the liquidus and solidus fields were determined for tungsten bronze‐type solid solutions in the Na2O‐BaO‐Nb2O5system by DTA and melt crystal growth experiments. Bronze‐type solid solutions exist to 7.1Na2O‐34.9BaO‐58Nb2O5in the Nb2O5‐rich region and from 12Na2O‐38BaO‐50Nb2O5to 4.6Na2O‐45.4BaO‐50Nb2O5along the NaNbO2‐BaNb2O6join, which includes NaBa2Nb5O15=10Na2O‐40BaO‐50Nb2O6. There is little, if any, solid solubility of compositions with a deficiency of Nb2O5. Curie temperatures decline rapidly and dielectric constant peaks broaden with Nb2O5substitution because the Nb:O ratio becomes greater than the octahedral 1:3 ratio. Useful ferroelectrics exist along the NaNbO3‐BaNb2O6join where the Nb:O ratio is 1:3. Large striae‐free crystals, with less optical scattering than Czochralski‐grown crystals, were grown from unseeded Na2O‐rich melts (e.g. 15Na2O‐37.5BaO‐47.5Nb2O5) cooled from 1520° to 1300°C at 2°C/h. Annealing effects on these crystals whose compositions l

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11990.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

A correlation between plastic deformation at crack tips in sodium chloride and the measured value of the fracture surface energy is presented. Plastic deformation can either aid or hinder crack growth, depending on the mode of deformation at the crack tip. If plane‐stress deformation occurs, crack motion is hindered by step formation, dislocation generation, and plastic blunting of the crack tip. If plane‐strain deformation occurs, crack motion is aided by stress fields that arise from the deformation. The specific surface free energy of sodium chloride, {100} plane, is estimated to be less than 0.37 J

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11991.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The addition of CaO to ThO2inhibits discontinuous grain growth and allows sintering to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The optimum amount of CaO added is 2.0 mol%, which exceeds the solid solubility limit. A model of second‐phase inclusions impeding grain boundary motion was used to explain the result

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11992.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The dissolution of CsXeF7in molten alkali fluoroberyllate glasses between 250° and 500°C is described. The apparent small solubility of Xe(VI) in these ionic glass‐forming melts (about 1 to 2 wt% or less) may be related to retention of a molecular configuration by XeF6that is caused by its strong fluoride ion donor properties and/or to the nonmelting behavior of numerous MF‐XeF6salts when they are heated. Rather low‐softening (about 100°C) glasses were also prepared in the TIHF2‐NaHF2‐BeF2system, whereas TlHF2has a relatively low melting point (about 85°C). Contrary to expectations, Xe(VI) appears to oxidize TI+in these molten glass environm

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11993.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Previous measurements of the thermal conductivity of TiC, ZrC, and NbC by the present authors showed that at low temperatures the phonon‐electron scattering in these materials is strong and gives rise to an unusual temperature dependence of the lattice thermal conductivity. The Callaway analysis of those data is now extended to include the high‐temperature data of Taylor for TiC. The analysis of the thermal conductivity of TiC from 2° to 2000°K indicates that: (1) For samples with higher carbon contents, it is necessary to modify the phonon‐electron relaxation rate at low temperatures and (2) a strong point‐defect scattering term is required to explain the high‐temperature data. This scattering is due primarily to force‐constant changes rather than mass changes which are introduced by the presence

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11994.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Opalescence and clearing techniques were used to determine the metastable immiscibility surface for sodium borosilicate solutions. These results indicate that a three‐liquid region, which may or may not be metastable to two‐liquid regions, underlies the immiscibility surf

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11995.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The subsolidus portion of the system CdO‐PbO‐O was investigated at high temperatures and oxygen pressures in cold‐seal pressure vessels. Specially prepared cadmium hydroxide precipitate was used to achieve reaction equilibria. Two ternary oxide phases exist in the system: Cd2PbO4is stable under all conditions investigated; CdPb2O5dissociates (2CdPb2O5⇋ Cd2PbO4+Pb3O4+O2). The P‐T univariant curve was mapped. Compatibility triangles illustrate the phase equilibria of the system. Cell constants for Cd2PbO4are:a0=5.671,b0=9.902,C0= 3.139, all ±0.001 Å. The space group was determined asPbam(Pba2); Cd2PbO4is isostructural with the Sr2PbO4structure type. Derived average metal‐oxygen distances are: Cd–O 2.35 and Pb–O 2.08 Å. The structure of C

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11996.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Submicron hafnium oxide powder prepared by hydrolytic decomposition of alkoxides was studied. The particle size range of this powder was 10 to 50 Å. Emission spectrographic analysis of the powder after it was calcined at 250°C for 0.5 h indicated a purity of>99.995%. Up to 320°C, the powder showed no crystallinity by X‐ray analysis. The amorphous HfO2was isothermally aged at 5° to 10°C intervals between 200° and 500°C. X‐ray diffraction patterns indicate a sharp transition from an amorphous state to the monoclinic phase at 325°C. High‐temperature X‐ray studies and DTA suggest nucleation and growth of small crystallites at 420°C leading to conversion to monoclinic HfO2at 480°C. BET surface area measurements and TGA of the powders were also conducted. A powder which transformed at 325°C to the monoclinic phase was isothermally aged below 325°C for 1

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb11997.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY