ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12669.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The system U‐Sb‐O was examined in air up to 1000°C for ternary compounds. The products were characterized by chemical analysis, density determinations, TGA, X‐ray diffraction techniques, and magnetic measurements. The ternary compounds found were USbO5and USb3O10. All cations are pentavalent in these new compounds, which are crystallographically related to α‐UO

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12670.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The optical absorbance of commercially pure thoria single crystals was measured after oxidizing and reducing treatments, irradiation by 18‐MeV protons, 48‐MeV16O ions, and60Co gamma photons, and thermal annealing at temperatures up to 950° C. For unirradiated specimens, absorption bands previously observed at 2.80, 3.03, and 4.03 eV were confirmed, and additional bands were identified at 1.67, 2.04, 2.45, 3.61, and 4.52 eV. Reduction and irradiation enhanced the 3.03 and 3.61 eV bands but diminished the 2.80, 4.03, and 4.52 eV bands. The centers responsible for the two groups of bands are thus presumed to be electron‐type and hole‐type, respectively. Impurity atoms, also, are probably involved in the centers. Ion irradiation produced an intense blue color in the exposed volume of the specimens, and additional absorption bands appeared at 1.49, 1.80, 2.03, and 2.32 eV. The behavior of these bands on annealing and on subsequent low‐exposure gamma irradiation indicated that the corresponding centers are combinations of impurity atoms and oxygen int

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12671.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Density and lattice parameter changes induced by dopants were studied in Czochralski rubies containing from 0.054 to 0.160 wt% Cr2O3, in Czochralski sapphires containing from 0.083 to 0.120 wt% TiO2, and in verneuil crystals grown from powders containing 250 to 1000 ppm Ca, Mg, Si, and V. Densities were determined within at least ∼0.005% using a hydrostatic weighing technique; lattice parameter shifts were measured within a maximum of 0.25% using a step‐scanning goniometer technique. Some crystals which appeared to be clear, transparent, and single‐phase contained fine particles of a second phase. It is concluded that Si4+and Ti4+ions enter solution with the formation of cation vacancies to maintain charge neutrality, that verneuil crystals contain vanadium as V3+, that the solid solubility of Ca2+is low (<340 ppm), and that MgO decomposes under verneuil growth conditions, resulting in formation of a second

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12672.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Oxide crystallite formation and growth from freeze‐dried sulfates were studied for the representative materials Al2O3and Fe2O3. Transmission and scanning electron micrographs showed the formation and growth of chainlike aggregates of crystallites. Aggregation occurred as part of the nucleation and growth of the oxide, and discrete oxide particles were never present. Orientation of the chain aggregates was related to the ice structure formed during freezing. X‐ray line broadening data showed that crystallite size is a function of the 1/5 to 1/7 power of time for isothermal treatments. A qualitative analysis of material transport favored the surface diffusion mechan

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12673.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Glass formation in metal acetate systems was investigated; the tendency for these systems to form glasses is so great that even lithium and lead acetates are readily quenched to glass. Glass formation is favored near eutectic compositions in binary systems. Physical and optical properties of representative glasses are given.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12674.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Certain optical transitions were calculated for the first‐row transition metal ions Ti3+, V3+, Cr3+, Fe2+Co2+, and Ni2+in a silicate matrix. The calculations were performed at 7 inter‐ionic distances for each ion because the metal‐ion‐to‐oxygen interionic distances are unknown; the silicate oxygen charge was varied from 1.00 to 2.00 in each case because the true charge on silicate oxygens is also unknown. Integrals used in the calculations were calculated using Slater and self‐consistent field wave functions, and computer programs were used to evaluate all integrals. Equations were derived for calculating all optical transitions for these ions in octahedral fields; the extension to fields of other symmetry is trivial. Several optical transitions were computed to obtain the calculated orders of magnitude for the optical transition. The results for self‐consistent field wave functions are lower than expected; they indicate that the transition metal ion in glasses is situated in fields near the size of a

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12675.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The kinetics of the reaction of UC2spheres with nitrogen was studied from 1500° to 1700°C. A metallographic method was used to determine the time‐dependent conversion of UC2to U(C,N) and free C. The conversion appeared to be controlled by the diffusion of solid carbon in solution to sites where it could precipitate as free carbon. These sites were the surface of the sphere and particles of free carbon that existed within the original UC2. An increased distribution of these internal sites decreased the distance for carbon diffusion and resulted in an increased rate of reaction. The UC2appeared to undergo a very rapid initial reaction that resulted in the uptake of 1 to 5 at.% nitrogen in the UC2at these temperatu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12676.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The mechanism of formation of iron‐zircon pink and vanadium‐zircon blue stains was studied, primarily by the marker technique. Reaction occurred at the site of the reactant ZrO2. The primary function of the mineralizer in these stains is to react with SiCK and to assist in its transport to the reaction site. Although the basic mechanism of formation of both stains is the same, important differences result from the physical properties of the dopants at reaction temperatu

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12677.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Polycrystalline MgO appears to deform ductilely when it is strained under confining pressures greater than 2 kbars at room temperature. Although the {110}〈110〉 slip systems in MgO do not provide the five independent slip systems required for homogeneous deformation, the lack is apparently met in part by the activity of additional slip systems and in part by microfracture. The strong pressure dependence of the stress‐strain curves probably arises from the pressure sensitivity of microfracture, which becomes less important as the temperature is raised; high‐temperature experiments at 2 and 5 kbars confining pressure show that the pressure dependence virtually disappears at 750°C and that there is a simultaneous trend toward wavy slip. High‐temperature experiments on single crystals oriented for cube slip produced only kinking below 300°C; above 300° there is some cube slip, but it is not clear that this is a major deformation mechanism. The pressure dependence of the fracture and flow stresses is interpreted in terms of recent theories of crack propagation un

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12678.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY