ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15091.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The specific energy of water in a clay‐water system, called the moisture stress, is a fundamental parameter governing physical behavior in unfired clay bodies. The importance of moisture stress for studying moisture movement, changes in strength, and other physical properties during drying, is shown. The relations between moisture stress and moisture content for 18 typical New Zealand ceramic bodies have highly characteristic shapes from which the suitability of the material for ceramic use can be deduced. Moisture stress ranges from approximately 0.4 × 106ergs/g at extrusion, through 2 × 107ergs/g at the shrinkage limit, to 1010ergs/g at oven dryness. The dependence of moisture stress on the structural arrangement of clay particles, resulting in a very marked hysteresis, is discussed. The usefulness of the moisture stress concept in understanding practical problems is emphasi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15092.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Activity‐composition relations in Mn‐Co orthosilicate and metasilicate solid solutions were determined at 1200° to 1250°C by equilibrating selected phase assemblages with metallic cobalt and a gas phase of known oxygen potentials at a total pressure of 1 atm. The orthosilicate solid solution shows a slight negative departure from ideality, whereas the metasilicate solid solution is ideal. The stability data derived for the Mn2SiO4and MnSiO3end‐members are in good agreement with those previously determined from the system MnO‐“FeO”‐SiO2. The free‐energy change for the reaction 2CoSiO3= Co2‐SiO4+ SiO2was determined to be

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15093.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The initial shrinkage of powder compacts of rutile was measured in air at 700° to 1130°C. The shrinkage behavior agrees well with a model based on grain‐boundary diffusion. The apparent activation energy for the shrinkage rate is 76.9 ± 2.5 kcal/mole. Changes in ambient atmosphere (O2, N2, vacuum) had no effect on the initial sintering kine

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15094.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The elastic constants and coefficients of thermal expansion of polycrystalline forsterite (Mg2SiO4) and steatite (MgSiO3) were determined from room temperature to 1000°K. Two elastic moduli, the adiabatic bulk modulus,Bs, and the shear modulus, G, decrease linearly with temperature above 500°K. The Grüneisen constant γ and a parameter δ, defined as — (dBs/dT)/αBs, calculated from the present data were virtually independent of temperature at the high‐temperature range. Poisson's ratio, δ, rises linearly with temperature over the range of measurement; the slope is highest for materials with the lowest room‐temperatur

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15095.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The 1300°C isotherm of the system MgO–FeO–Fe2O3was studied thermogravimetrically under conditions of controlled fugacity of oxygen. The magnesioferrite solid solutions that coexist in equilibrium with magnesiowüstite solid solutions have a cation to anion ratio experimentally indistinguishable, in the present study, from 0.750. Curves are presented expressing the change in composition of coexisting magnesioferrite and magnesiowüstite phases as a function of temperature and oxygen fugacity. These curves for the system MgO‐FeO‐Fe2O3can be used (1) to predict compositional relations under isothermal conditions for temperatures where reaction rates are sluggish, (2) as additional oxygen buffer curves for experimental control of oxygen fugacity, and (3) in certain instances to distinguish equilibrium from nonequilibrium a

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15096.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The thermal expansion of a number of cubic refractory compounds of thorium was measured by high‐temperature X‐ray diffraction. The coefficients of thermal expansion range from 7.5 to 8.2 × 10−6/°C for ThN, ThC0.84, ThP0.71, ThP0.61, and Th3P4between 900° and 1300°, 1450°, 1750°, 1750°, and 1150°, respectively; the coefficients for ThS, ThB6, and ThO2are in the range of 11.2 to 12.0 × 10−6/°C between 900° and 1400°, 1700°, and 2100°, respectively. The results are discussed in relation to other properti

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15097.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Plastic deformation was studied in hot‐pressed poly crystalline specimens of titanium carbide, vanadium carbide, niobium carbide, tantalum carbide, and tungsten carbide tested in four‐point bending and under compression to 2100°C. Transition from brittle to ductile behavior occurred at approximately half the absolute melting temperature for each material. Above this temperature the yield strengths decreased exponentially with increasing temperature. Between the ductile‐brittle transition temperature and about 1900°C the apparent activation energy for flow in the carbides with the rock‐salt structure was near O.S ev/atom. Above 1900°C the value was approximately 2 ev/atom; the value for tungsten carbide was apparently 0.3 ev/atom to 2070°C. Vanadium carbide and titanium carbide recovered extensively on annealing for short times near 2000°C. No such recovery occurred in tungsten carbide under these conditions. The results for polycrystalline carbides were compared with available data for single crystals of tita

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15098.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The system Zr‐O was studied in the composition range 50 to 66.7 at.% O by metallographic analysis, high‐temperature X‐ray analysis, and lattice parameter determinations at room temperature. The solubility of zirconium in zirconia was determined from 1200° to 2000°C, and the cubic‐tetragonal inversion temperature of ZrO2was shown to be lowered to approximately 1490°C for samples containing α‐Zr and oxide phase. Alpha zirconium has greater solubility in the cubic phase than in the tetragonal phase, and the inversion is revealed, in samples quenched from the cubic field, by the exsolution of α‐Zr, which is metallographically characterized as striations. At room temperature, the striations are oriented with the 111 and 11° planes of mo

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15099.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Quasi‐thin sections of large‐grained ferroelectric barium‐strontium titanate ceramic compositions were observed under crossed polars. Dielectric constant and light transmission were measured as a function of temperature and applied dc voltages. Microscopic observations, such as changes in structure and in optical anisotropy with temperature and simultaneously applied electric fields, are described. Optical data indicate that static electric fields readily induce anisotropy in the isotropic grains at the ferroelectric to paraelectric transition of the ceramic. Below the transition temperature, the effect of the field on the optical and dielectric properties diminishes. Contrary to single‐crystal barium titanate, a field‐produced reorientation of domains in the ceramic at temperatures below the transition proceeds with difficulty, and is sometimes achieved only after long exposures to high‐bia

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb15100.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY