ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13849.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The ternary system Ta‐Mo‐C was investigated by X‐ray, melting point, DTA, and metallographic methods on chemically and thermally characterized specimens; a phase diagram for temperatures from 1500°C through the melting range was established. At high temperatures, the cubic monocarbides, TaC and αMOc1‐x, as well as the hexagonal subcarbides, Ta2C and Mo2C3form continuous series of solid solutions. Below 1960°C, the homogeneity range of the β phase is temperature‐dependent. At 2230°C, the ternary subcarbide solid solution disproportionates into metal and monocarbide alloys. The sub‐lattice order‐disorder transformation temperatures in both subcarbides are lowered by the mutual exchange. The ternary range of the η‐MoC1‐x, phase is very restricted, and the metastable ζ‐Ta‐C phase is stabilized in the ternary. Seven isothermal reactions occur in the system in the range from melting to 1500°C; two further isotherms between 1400° and 1500°C are indicated to result from the order‐disorder transition in Mo2C. Using existing literature data for the thermodynamic properties of the binary carbides, the phase relations in the Ta‐Mo‐C system were thermodynamically analyzed. The calculated equilibria are in good agr

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13850.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Low‐expansion solid solution surface layers formed by reaction of Cr2O3and Al2O3were used to chemically strengthen alumina bodies. The surface layers were formed by packing the samples in Cr2O3powder and heating to high temperatures. Fluorides or chlorides were added to the packing material, leading to substantial additional improvement. The flexural strengths of the control samples were increased by refiring in the presence of the products of decomposition of the fluorides. At high concentrations of fluorides in the packing material, the outside dimensions and the weights of the samples decreased during the treatment

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13851.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Graphite specimens bonded by kaolinite‐illite clay, in which planar orientation of the graphite flakes and clay platelets had been produced by deformation, showed enhanced differential drying shrinkage with increased graphite content. The greater shrinkage was perpendicular to the plane of preferred orientation. Comparable additions of quartz grains to the clay made the drying shrinkage less differential. The volume drying shrinkage was first increased and then decreased by successive additions of graphite. The increase was ascribed to the increasing concentration of water in the clay bond as the clay content diminished. The subsequent decrease appeared because the drying shrinkage of the clay was reduced near the graphite and because the graphite itself did not shrin

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13852.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Thermodynamic properties of liquid mixtures of feldspar and silica were considered in attempting to interpret them in terms of melt structure. Two sources of data were used: the heats of formation and free energies of formation of the crystalline and glassy compounds, and the published phase diagrams. The systems albite‐silica, orthoclase‐silica, and anorthite‐silica were studied, and some data from the system celsian‐silica were included. A model which assumes a random distribution of AlO4tetrahedra and SiO4, tetrahedra is generally applicable to silica‐rich liquid mixtures of albite‐silica and orthoclase‐silica. For mixtures of albite‐silica, it is suggested that minor amounts of polymeric aluminosilicate units are also present. In liquid mixtures of anorthite and silica, however, it is necessary to assume that polymeric units like 4AlO2.3SiO2or 4AlO2.2SiO2, are the dominating feature o

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13853.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

The vapor pressure of hypostoichiometric urania was measured as a function of temperature for a series of compositions. The data were obtained by an entrainment technique in which weight loss of a specimen vaporizing at high temperatures in a stream of carrier gas is followed continuously with a recording thermobalance. Use of suitable atmospheres produced constant vaporizing compositions which vaporized pseudocongruently. Equations obtained for the vapor pressure are:

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13854.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

A quantitative rheological model was developed for predicting the non‐Newtonian flow behavior of aqueous halloysite suspensions. Halloysite clay from the large Utah deposits was used for this investigation because of its unique tubular morphology. The flow behavior of the suspensions was characterized by the semi empirical Ree‐Eyring generalized viscosity equation. The β parameter in the Ree‐Eyring equation, a measure of the relaxation time for the flow process, was very sensitive to variations in the pH and volume fraction solids. When the logarithm of 0 was plotted versus pH (4 to 11) for halloysite suspensions containing 15, 20, and 25 wt% solids, linear plots with increasing slopes were obtained. Attempts were made to show the physical significance of the parameters introduced in the

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13855.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

A simple technique for investigating boundary mobility is outlined and applied to the study of boundary migration in melt‐grown bicrystals of KCl containing pure twist boundaries. An unexpectedly high activation energy, 4 to 6 ev, is found for movement of the twist boundarie

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13856.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Grain boundary energies are computed for twist boundaries in NaCl with the assumption that there is no relaxation of the lattice at the boundary. The energy is 573 ergs/cm2and is independent of angle over the range studied. Comparison is made with recent experimental results for twist boundaries in KCl.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13857.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

A simple, rapid‐quenching device was used to investigate the extent of liquid‐liquid immiscibility in the system BaO‐SiO2. A metastable miscibility gap was found with an upper consolute point at about 10 mole % BaO and 146OOC. Bulk glass samples of different compositions and heat treatments were examined by direct‐transmission electron microscopy to determine the phase separation morphology. At low BaO contents the separation was characterized by spherical barium‐rich particles in a silica‐rich matrix. For compositions near the center of the gap, the structure consisted of two phases continuously interconnected throughout the bulk of the glass. At higher BaO contents, spherical silica‐rich particles were found in a barium‐rich matrix. The dependence of the morphology on quench rate and heat treatment was investigated. Predictions of other authors concerning the occurrence of BaO‐SiO2immiscibility are compared with th

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1968.tb13858.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY