ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15403.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Guarded measurements of the electrical conductivity of high‐purity, polycrystalline Y2O3in thermodynamic equilibrium with the gas phase were made under controlled temperature and oxygen partial pressure conditions. Data are presented as isobars from 1200° to 1600°C, and as isotherms from oxygen partial pressures of 10−1to 10−17atm. The ionic contribution to the total conductivity, determined by the blocking electrode polarization technique, was less than 1% over the entire range of temperatures and oxygen partial pressures studied. Yttria is shown to be an amphoteric semiconductor with the region of predominant hole conduction shifting to higher pressures at higher temperatures. In the region ofp‐type conduction, the conductivity is represented by the expression σ= 1.3 × 103pO23/16exp (‐1.94/kT). The observed pressure dependence is attributed to the predominance of fully ionized yttrium vacancies. Yttria is shown to be a mixed conducto

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15404.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The variation of elastic constants of MgO with pressure was determined by using McSkimin's pulse superposition technique. Measurements were made up to 2 kbars pressure at room temperature and liquid nitrogen temperature. The room‐pressure values of the adiabatic elastic constants, based on a density at 23°C of 3.5833 g/cm3, are (in kilobars

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15405.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The creep rate of polycrystalline thorium dioxide is reported for 1400° to 1800°C and for 4000, 7500, and 11,000 psi. The microstructure of deformed specimens contained intergranular voids which formed by the apparent growth and coalescence of pores along the grain boundaries. Grain‐boundary sliding also occurred during creep. The strain rate‐stress relation indicates a viscous type of creep process. A mechanism of creep is proposed which involves a diffusional transport of material and which accounts for the appearance of the intergranular

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15406.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Crystals of potassium tantalum niobate (KTN) were grown by two techniques: (1) pulling in the 〈100〉 direction with a continuously increasing crystal diameter, and (2) growing {100} platelets while floating on the surface of the melt. The amount of tantalum in the crystals increased rapidly with increasing potassium in the melt. The rate of potassium oxide evaporation from the melt was signific

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15407.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The decomposition of boehmite, or alpha alumina monohydrate, was studied in water vapor and nitrogen atmospheres between 430° and 500°C. Powder samples used consisted of agglomerates of very small boehmite crystallites. The rate of decomposition was determined with a transducer which measured the loss of sample weight due to the liberation of gaseous water. A linear rate law is obeyed by the decomposition of boehmite and, because of the characteristics of the fractional weight loss‐time curve, an interface model was suggested as the mechanism of decomposition. The activation energy was 70 kcal/mole. The effect of water vapor on the rate of decomposition was investigated. A simple forward‐back reaction mechanism did not satisfactorily explain the data. Two models, either of which could be valid, were proposed to describe the relation between decomposition rate and water vapor pressure: (1) An adsorption‐desorption process of water on the boehmite was assumed, and (2) an intermediate species of Al2O3entering into the decomposition reaction was

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15408.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Gamma‐induced coloration in borate glasses containing arsenic was studied to secure information on: (a) the effect of addition of As2O3on the induced coloration of the alkali borate base glass, and (b) the possibility of using radiation‐induced coloration in studying structural changes. At concentrations of less than 10 mole % As2O3, arsenic takes network‐modifying positions and at concentrations greater than 10.0 mole % As2O3, it takes network‐forming positions. Between 15.0 and 25.0 mole % As2O3, an additional change in the structure was detected. This change may be confined to the mode of arrangement of the structural units associated with the formation of groups or compounds. Additional studies based on infrared absorption, ultraviolet absorption edge, and density measurements, as well as the chemical analysis of the glasses, confirmed the structural changes suggested from irradiation

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15409.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

New data obtained on the join Ca2SiO4‐CaMgSiO4established a limit of crystalline solubility of Mg in α‐Ca2SiO4corresponding to the composition Ca1.90Mg0.10SiO4at 1575°C. The α‐α’Ca2SiO4inversion temperature is lowered from 1447° to 1400°C by Mg substitution in the lattice. α'‐Ca2SiO4takes Mg into its lattice up to the composition Ca1.94Mg0.06SiO4at 1400°C and to Ca1.96Mg0.04SiO4at 900°C. A new phase (T) reported previously by Gutt, with the approximate composition Ca1.70Mg0.30SiO4, was stable between 979° and 1381°C, and should be stable at liquidus temperatures in multicomponent systems in

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15410.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Preferential diffusion of Ni2+and Co2+along grain boundaries was observed in certain bicrystals of MgO. This enhancement is attributed to impurity segregation at the boundary. The identified impurities responsible for the effect are the principal impurities in the single‐crystal MgO: Ca, Si, and Fe. No enhancement was observed in any bicrystal prepared above 1300°C, a temperature similar to that at which studies of the mechanical properties of MgO have implied a reabsorption of impurity precipitates into solid solution. It is concluded that enhanced grain‐boundary diffusion of cations in MgO is an extrinsic, rather than an intrinsic, property of the boun

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15411.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Ways of describing and defining progress of fining or the standard to be achieved are discussed. Methods of measurement are also discussed. Published quantitative data which can be used to test proposed hypotheses or theories are reviewed. Finally, processes known to be important in eliminating gas bubbles from liquids, namely rise and bursting at the surface, coalescence, and growth or dissolving are discussed.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb15412.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY