ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12181.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Self‐radiation from α‐decay of244Cm causes lattice swelling, phase transformations, and loss of structure in several Cm compounds. In Cm oxides, the percentage swelling at saturation decreases with decreasing symmetry: Swelling in fluorite (fee) CmO2(∼0.3%) is approximately twice that in beeC‐type Cm2O3; monoclinic Cm2O3does not swell. CmO2swells with time according to Δa/α=3.0×10−3(1–e−1.7×104λt), essentially the same relation as for PuO2and AmO2. The rate of structure loss of Cm oxides decreases with increasing temperature of prior heatings. In CmAlO3the metamict state is produced before swelling reaches saturation. Radiation‐induced transformation at room temperature produces metastable phases that normally exist at higher temperatures, e.g. bccC‐type Cm2O3transforms to hexagonal A‐type Cm2O3, and rhomboh

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12182.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The crystallite growth of rare‐earth oxide powders with particle sizes of 10 to 30 Å obtained by the hydrolytic decomposition of alkoxides was investigated. These powders were compared with commercially available powders with average particle sizes from 1000 Å to 10 μm. Static and dynamic atmosphere tests were made, the latter by continuous tumbling during calcination. Dynamic calcination controlled crystallite growth effectively while maintaining uniform particle size. Typical arithmetic mean particle sizes were 250 Å for powders calcined at 800°C for 24 h with tumbling and ∼400 Å for powders calcined under identical conditions without tumbling. TGA, X‐ray diffraction, and emission spectrographic analyses were used to characterize the powders. Electron microscopy and BET surface area measurements demonstrated the importance of the dynamic calcination method in the growth of primary crystallites into larger particles during the presintering stage of the processing of th

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12183.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Pulse electrical strengths of hot‐pressed MgO containing 0.3 wt% LiF were measured. Strengths as high as 5.9×108V/in. were obtained on samples 99.8% of theoretical density with 1‐to 3‐μm grain size. An increase of either porosity or grain size resulted in a monotonic decrease in strength. Single‐crystal strengths of 4.0×106V/in. were obtained by polishing samples chemically. A simple recessed‐electrode configuration eliminated co

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12184.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The sonic resonance technique was used to determine the elastic moduli of polycrystalline Yb2O3samples of rectangular cross section ranging in pore fraction from 0.058 to 0.27 at temperatures from 25° to 1000°C. The data showed that the Young's and shear moduli are best related to pore fraction by a linear equation and to temperature by the Wachtman equation. The Debye temperature for Yb2O3was calculated from the Young's and shear moduli to be 385

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12185.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Study of the time dependence of physical properties in the transformation range of glass is complicated by the “memory effect” and the inherent nonlinearity which are characteristic of structural relaxation. A multiparameter model of structural relaxation is presented that differs from earlier models in that it takes account of both these effects. This model fits available experimental data well; these data were obtained for the most part by observing the evolution of properties (such as density or refractive index) following a step change in temperature. The present model also permits prediction of the physical properties of glass subjected to arbitrary and more complex temperature‐time histories. It should, therefore, also be useful in the rational design of heat treating processes such as anne

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12186.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

A high density of planar defects, often forming closed figures on {111} planes, was observed in chemically‐vapor‐deposited β‐SiC. The defects were identified as extrinsic stacking faults by electron diffraction contrast an

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12187.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Thermal expansion of Pb3O4was investigated by high‐temperature X‐ray diffraction. The coefficient in thea0direction is 14.6×10−6/°C. Expansion in the c0direction is 32% greater, with a coefficient of 19.3×10−6/°C. Coefficients of expansion are linear from 25° to 490°C and are comparable with those of tetragonal and ort

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12188.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Phase equilibrium relations in the liquidus temperature region of the system MnO‐“FeO”‐ZrO2‐SiO2and of its bounding systems MnO‐ZrO2, MnO‐ZrO2‐SiO2, and MnO‐“FeO”‐ZrO2were determined by the quenching technique. The equilibrations were carried out at sufficiently low O2pressures to keep most of the Mn and Fe in divalent states. The results obtained were combined with literature data for the other bounding binary and ternary systems to present phase diagrams showing liquidus surfaces and interrelations between coexisting liquid and solid‐solution phases. Applications of the data to refracto

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12189.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Unusual deformation phenomena accompanying partial crystallization were observed during heat treatment in the softening temperature range of Li‐Na‐Si glasses. Glassy lumps or protuberances formed at the surfaces of fibers 0.5 mm in diameter; rods and plates showed even greater distortions, their original shapes often becoming unrecognizable. Liquid‐liquid immiscibility accompanying the crystallization of a 0.7Li2O.0.3Na2O.2SiO2glass was believed to follow, rather than precede, crystallization. Explanations of these phenomena are pro

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1971.tb12190.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY