ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14961.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Polycrystalline samples, thin single crystals, and—325 mesh powders of brucite decomposed according to a first‐order rate equation consistent with a random nucleation process in beds of micron‐sized particles formed by disruption during the very early stages of the process and consistent with electron and optical microscope observations. Kinetic data for the decomposition of thick single crystals were more complex but could be fitted to an interface‐model equation which predicts that decomposition will be controlled by the movement of an interface reaction along the basal plane. Physical disruption of these crystals was confined initially to the outer edges of the crystals and proceeded along the basal plane in the form of a contracting disk. Since the decomposition occurs in cracked material and not at a strict interface, the fit of the data to the interface model may be for

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14962.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Three limestone powders, differing only in specific surface area, were agglomerated in a balling drum to form pellets of various sizes. The pellets were tested for dry compressive strength at different rates of deformation. A limiting elastic energy criterion for failure was used to derive the relation (analogous to the classical Hertz relation for strength of an elastic isotropic sphere) between the pellet size, the total deformation, and the load at failure. The surface area of the powder, the porosity of the pellet, and its compressive strength are analytically related; the results are in good agreement with the experimental data.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14963.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The elastic properties and thermal expansion coefficients of two‐phase ceramic bodies were determined in order to study the effect of the difference in thermal expansions of the two phases. Room‐temperature elasticity was determined by a dynamic method. These values were extrapolated to theoretical density to obtain values for the fully dense bodies. Thermal expansion, measured on a precision dilatometer at 25° to 350°C, was independent of porosity. Experimental values of elastic moduli and expansion coefficients were compared with values given by several theories. Where the difference in expansion coefficients was small the experimental and theoretical values of elastic moduli and expansion coefficients were in agreement. Microscopic examination of these bodies did not reveal any internal cracking. When the difference in expansion coefficients became large enough, the experimental data were scattered and not in agreement with theory for either the elastic properties or expansion coefficients. Microscopic observations of these specimens revealed microc

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14964.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

BaTiO3crystals prepared from fused KF contain about 0.1 wt% fluoride ions in the oxygen sites of the lattice which lead to formation of TiF4, HF, and TiF3in addition to the formation of H2O during isothermal hydrogen reduction at high temperatures. All processes influence the number of electrons released by reduction as well as the defect structure of reduced barium titanate.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14965.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Mechanical thinning and fracturing techniques for preparing thin glass samples for direct‐transmission electron microscopy are discussed. A modification of the Doherty and Leombruno procedure for mechanically thinning ceramic materials is described. These techniques make possible more reliable electron microscope studies of fine‐scale submicrostructure in glass systems. Electron microscope observations on fused silica, an alkali borosilicate glass, and some binary silicate glasses are reported and discussed in terms of present understanding of glass struct

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14966.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Liquid immiscibility data in known binary oxide systems are analyzed in relation to three fundamental aspects. Immiscibility in glassforming systems is related to differences in ionic field strengths or electrostatic bond strengths between the network cation with oxygen and the modifier cation with oxygen. If this difference is too small or too large, immiscibility is not present. Analysis also indicates that immiscibility is not to be expected in binary phosphate and vanadia systems. Factors governing the extent of immiscibility are essentially unrelated to its occurrence; in borate and silicate systems, immiscibility is inversely correlated with the number of oxygens per modifier cation in the modifier‐rich liquid. Temperature of the monotectic almost always lies between the melting point of the glass former and the first compound beyond the immiscibility gap. Properties of the monotectic, such as the primary phase under the two liquids and location of the eutectic, are fixed according to whether the monotectic temperature is above or below the melting point of the glass former. Principles of immiscibility are summarize

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14967.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Polarographic techniques using a rotating micro‐electrode are given. Experimental results cover concentrations and valence states of metal oxides in a sodium disilicate solutio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14968.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Conditions for crystallization of calcite from melts in the presence of a vapor or gaseous phase are reviewed to provide possible guidelines for growth of calcite. Phase equilibrium data for the system CaO‐CO2show that to precipitate calcite from molten CaCO3the temperature must be above 1230° C and excess CO2must be present at pressures greater than 39.5 bars. Phase equilibrium data for the system CaO‐CO2‐H2O show that calcite can be precipitated from melts at 650°C in the presence of an aqueous vapor phase at 10 bars or more. Crystallization can be induced either by introducing temperature variations, or by changing the composition of the coexisting aqueous vapor phase under isobaric, isothermal conditions. The system CaO‐MgO‐CO2‐H2O is used to show that doped calcite crystals, CaxR1‐xCO3, could be precipitated, with precisely controlled compositions, from melts in the system CaO‐RO‐CO2‐H2O. Apatite phase relatio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14969.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Density (and some viscosity) data are presented for binary sodium borate melts containing as much as 60 mole % Na2O and for ternary sodium silicoborate melts with B/Si<2.0 between 1000°C and 1300°C. The high‐temperature partial molar volume analysis of the binary sodium borate melts reveals about 50% BO4tetrahedra at the 40 mole % Na2O composition, in agreement with recent NMR estimates for the binary glasses. No “boron anomaly” was found near 18 mole % Na2O at high temperature. The synthetic partial molar volume model that agrees best with experiment for all ternary melts studied involves the presence of some BO4tetrahedra, the percentage of which varies with composition. This ternary model involves a high degree of internal consistency. No tendency toward extensive micro‐immiscibility was observed for ternary melts near the SiO2·

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1967.tb14970.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY