ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12131.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Experimental data on the interfacial reaction between portland cement clinker and molten coal ash at 1400° to 1500°C are consistent with a mechanism involving diffusion in the melt as the rate‐controlling step. The formation and growth of well‐defined zones between the reactants are characteristic of the reaction. Equations were solved for diffusion with two moving interfaces. On the basis of these equations and data from the lime‐alumina‐silica phase equilibrium diagram, the diffusion coefficient for CaO in the interstitial melt in the clinker is about 5±10‐6cm2/s at 1500°. The results imply that the clinkering reaction in the burning of portland cement clinker is also controlled by diffusio

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12132.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Compression creep measurements at constant load on ZrO2‐6 mol% Sc2O3(grain size ∼1 μm), ZrO2‐6 mol% Y2O3(grain size ∼17 μm), and heat‐treated ZrO2‐6 mol% Sc2O3(grain size ∼2 μm) yield activation energies of 89, 86, and 74 kcal/mol, respectively. The creep rates are linearly proportional to the inverse square of the grain size of the material. A stress exponent,n, of 1.5 was found for the scandia‐doped zirconia and two regimes, withn=1 and 6, were found for the yttria‐doped zirconia. These data, supported by metallographic evidence, are interpreted as showing thatn=1 is associated with cation diffusion control of creep,n=6 with local propagation of inter‐crystalline cracks, andn=1.5 wi

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12133.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The diffusion of oxygen in UO2+αwas measured between 600° and 1100°C. Samples with initial O/U values 2.08 and 2.04 were reduced in hydrogen; reduction was monitored continuously by electrical conductivity measurements. The relation between total conductivity and average O/U ratio was derived, and the diffusion coefficients were obtained. The validity of the electrical conductivity vs O/U relation was checked by measuring weight loss during reduction. Diffusion‐controlled kinetics were confirmed by oxygen gradient measurements. The oxygen chemical diffusion coefficient is given byD= 0.5 exp ‐ This equation agrees with previously determined values of the oxygen chemical diffusion coefficient of

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12134.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The subsolidus region of the PbO‐SiO2system was studied by DTA and X‐ray diffraction. X‐ray diffraction analysis showed the presence of five compounds: 4PbO.SiO2, 3PbO·SiO2, 2PbO·SiO2, 3PbO·2SiO2, and PbO·SiO2. The compound 4PbO·SiO2has previously been reported to have three polymorphic forms; there are two polymorphs of 2PbO·SiO2with the inversion at 460°±15°C. The compounds 3PbO·SiO2and 3PbO·2SiO2were unstable above 430°±10° and 585°±15°C, respectively; PbO·SiO2was unstable below 525°±15°C. DTA patterns were determined for glasses of the composition

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12135.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Summary and ConclusionsThermal expansion measurements of composite systems containing hard dispersions embedded in brittle and semibrittle matrices indicate the importance of (1) the magnitude of the stress developed in the matrix and (2) the crack propagation behavior of the matrix. The thermal expansion of these composites can be predicted if the residual stress developed as a result of the difference in the expansions of the components does not exceed a critical value defined by the modified Griffith equation. This critical stress varied considerably with the nature (brittle, semibrittle, or ductile) of the matrix.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12136.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Laboratory simulation of the industrial process of annealing sheet glass has yielded data on the genesis of stresses in initially stress‐free glass. The experimental results differed from expectations based on classical annealing theory in that stresses began to develop in the annealing range even when the glass was being cooled at a constant rate, i.e. even in the absence of any changes of temperature gradients within the glass. Typically, these stresses account for 40% of the total residual stress in glass annealed according to a linear schedule. The remaining 60% are the well‐known thermoelastic stresses that arise later in the annealing process from the decay of temperature gradients in the glass. The stresses observed to arise in glass as it is being cooled at a constant rate are attributed to volume relaxation effects which, in parts of the annealing range, generate stresses rapidly enough that they are not dissipated by stress relaxation. A mathematical model of annealing is proposed that takes account of both stress and structural relaxation. The model fits the experimentally observed evolution of stresses during linear cooling. It also suggests that (with the activation energies of stress and structural relaxation about the same) the actual rate, at any given temperature, of structural relaxation is about 4 times lower than that of stress relaxat

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12137.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The wettability of AlN, TiB2, TiN, and TiC by liquid aluminum was investigated by the sessile drop technique at 2×10‐7torr or less. The contact angle decreased linearly with increasing temperature in all cases. Variation of the contact angle with temperature is correlated with the surface tension of the drop, and the Zisman‐type relation is established. The critical surface tensions (Rγc) of AlN, TiB2, TiN, and TiC are 664, 700, 713, and 725 dynes/cm, respectively. These values are correlated with the melting point of the ceramics. The Zisman relation is discussed and applied to calculation of the work of adhesion. The surface tension of liquid aluminum varies linearly with temperature:γLv(dynes/cm) = 948–0.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12138.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Electron spin resonance studies showed that gamma‐irradiated potassium borate glasses display complex spectra. These were resolved into five overlapping resonances by a thermal bleaching technique. The resonances differ in nature and stability, suggesting that they belong to different paramagnetic centers (I, II, III, IV, and V) induced by irradiation. The relative concentrations of these centers change with K2O concentration; the stability increases in the order V

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12139.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

The dielectric aging phenomenon was observed in tetragonal polycrystalline solid solutions of calcium titanate in barium titanate between 30° and 90°C, and the 90° ferroelectric domain microstructures were analyzed using replica electron microscopy and statistical procedures. The results show a correlation between aging rate and 90° domains that may be satisfactorily interpreted in terms of the internal residual stress relaxation theory of ag

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1970.tb12140.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY