ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13154.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Cation self‐diffusion was measured in single‐crystal strontium titanate. Nonhomogeneous diffusion kinetics were observed and were interpreted by the Fisher model. The composite diffusion coefficient,P, of the Fisher model is shown to have a dependence on dislocation density, ρ, in single crystals at 1875°C given by:for strontium, andfor titanium.It has previously been shown that oxygen ions have enhanced diffusivities in dislocation pipes; therefore, in SrTiO3all ions exhibit enhanced dislocation diffusion. Based on an assumed maximum value for lattice diffusion, the temperature dependence of strontium dislocation pipe diffusion is given by:whereh2is the dislocation core

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13155.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The effects of water vapor on the initial sintering of magnesia powder compacts were studied from 800° to 1107°C. The magnesia was obtained by thermal decomposition of magnesium oxalate. Water vapor partial pressures from 8 × 10–4to 658 mm were used. Initial sintering occurred by a grain‐boundary vacancy‐diffusion mechanism with magnesium assumed to be the slow moving species. Increasing water vapor partial pressure increased sintering rates. A model based on the solubility of the hydroxide ion in MgO relates this increase to the increase in the cation vacancy concentration. The grain‐boundary diffusion coefficient,DG, varied withPH2O. For partial pressures up to about 5 mm,nwas approximately ½ and for partial pressures above 5 mm it was between 1.0 and 1.5. The activation energy for densification was 80 kcal/mole for partial pressures up to about 5 mm and 48 kcal/mole above this parti

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13156.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The variation of refractive index of vitreous silica with purely hydrostatic pressure to 7 kbars was determined from the shift of the localized interference fringes across the specimen kept in an optical pressure bomb. Allowance for the change in the thickness of the specimen was made with the help of Murnaghan's finite‐strain theory and the recently determined third‐order elastic constants. The refractive index for λ 5893 A increases linearly with pressure with a slope of 9.2 × 10−4/kbar up to 4 kbars; thereafter it increases nonlinearly. The increase in the refractive index, however, is linear with respect to the Lagrangian strain in the range investigated, except for a slight tendency for departure from linearity at the highest pressures. No hysteresis effects caused by permanent densification were noted. The results are interpreted in the light of Mueller's theory of photoelasticity of amorphous

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13157.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The technique for the preparation of polyphase refractories for electron probe investigations is described. Chemical changes occurring during heating of an unused chemically bonded magnesia‐chrome refractory were studied and the spatial distribution of Fe, Cr, Al, Mg, Ca, and Si at different temperatures was determined. The development of the reaction layer around the chromite grains, the migration of ions into the periclase grains, and the distribution of ions in silicates were followed qualitatively usingKαX‐ray and electron back‐scattering di

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13158.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Properties of uranium monophosphide were determined at room and at high temperatures. Heating UP above 1400°C in vacuum resulted in preferential loss of phosphorus, producing a slight contraction of the cubic lattice. Effect of temperature and time on the densification, lattice structure, and stoichiometry of UP is discussed. Properties determined include hardness, melting temperature, electrical resistivity, vaporization behavior, irradiation behavior, thermal expansion, high‐temperature compatibility, and some chemical properti

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13159.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The interdiffusion of ferric oxide and silica between Na2O‐SiO2and Na2O‐SiO2‐Fe2O3melts containing the same mole % Na2O was studied at 1200°C in air. Values in the range lO−5to lO−8cm2sec−1were obtained depending on the composition of the binary melt. The results were rationalized on the basis of the changing ionic nature of the iron with the soda‐silica ratio of the ternary melt. It is concluded that significant concentrations of iron cations are present in the melt only if the mole fraction of soda is less than 0.3. A cursory examination of the relative electrical conductivity of a binary and a ternary melt tends to confi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13160.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Bubble formation at both electrodes in the systems metal | glass | oxide, metal is investigated by short‐circuiting, or application of an electromotive force. The systems investigated included noble metals, soda‐lime‐silicate glass, and simple or complex oxides which operate as electronic or ionic conductors. Oxygen was considered as the main gaseous component produced by an electrochemical process. The analysis of the current‐potential curves defining the kinetics of the electrochemical processes on the surface of two electrodes, points to the possible existence and the importance of bubble formation when two electrodes are short‐

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13161.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Oxygen reboil often occurs when glass is melted in air in platinum containers. Oxygen blisters develop even when well‐fined glass is remelted under similar conditions. Experiments show that this reboil is prevented or greatly reduced by: (1) Eliminating electron conductors from the system, (2) removing oxygen from the atmosphere over the melt, (3) applying an external bucking potential, (4) reversing concentration gradients, or (5) removing temperature gradients. These results suggest that oxygen reboil, which occurs at a platinum‐glass interface, results from the discharge of a concentration cell or a thermal cell. The proposed mechanism is: O2−→½ O2+ 2e−at the anode and ½ O2+ 2e−→ O2−at the cathode, with electron transport in the platinum and, to complete the circuit, alkali

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13162.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

The oxidation‐reduction equilibrium in Na2O‐2SiO2glass melts containing either copper or silver was studied by systematically varying the oxygen partial pressure above the melt. For copper the two equilibria areFor silver the equilibrium is analogous to the second of the two copper reacti

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1966.tb13163.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY