摘要:

The concentration of ionic species in the solution in contact with hydrating tricalcium silicate (C3S) has been studied as a function of time and in the presence of admixtures. The ionic product for calcium hydroxide (CH) was calculated as a function of time and correlated with calorimetric measurements and crystal growth data. The results support the hypothesis that nucleation of CH crystals controls the induction period and that their subsequent growth controls the second heat peak. The influence of admixtures can be predicted from their influence on CH crystal growth. However, solution data indicate that the system cannot properly be compared with the growth of pure CH; the combined role of C‐S‐H and CH must be considered. Some implications for C3S hydration are discus

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14104.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The isotope effect for22Na/24Na diffusion was measured for three 25‐mol% alkali‐silicate glasses. A multiple diffusion mechanism wherein the Na ions diffuse both singly (vacancy mechanism) and in pairs (interstitialcy mechanism) provided the best agreement with the experimental data. According to this tentative model, diffusion by Na ion pairs predominates at low temperatures, and the fraction of Na ions diffusing singly increases with increasing temperature. In the glasses investigated, nearly all of the Na ions diffuse singly in the vicinity of the transformation ra

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14105.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The linear and the crystal‐lattice thermal expansions of monoclinic CaO·Al2O3were determined. The average coefficientαof linear thermal expansion between 22° and 1200°C is 7.7 × 10−6/°C. The crystal lattice expands anisotropically with expansion coefficients along the principal axes of the strain ellipsoid of 9.8, 7.3, and 5.9 × 10−6/°C for the same tempera

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14106.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A numerical analysis of the Crank‐Nicolson type is used to determine the temperature distribution and phase‐boundary position for a slab‐shaped sample that is cooled or heated through a phase transition under the assumption that heat transfer controls the kinetics of the transition, thus the phase boundary remains planar. First‐order and second‐order transitions (Ehrenfest) are considered, as is a mixed transformation with partially first‐order and partially second‐order behavior. Stress and temperature distributions are calculated for each type. Particular interest is attached to the surface stress. Results are presented using the thermal and elastic properties of quartz. The results are interpreted in reference to brittle fracture during cooling. When slow crack growth is possible, it is shown that, for a purely first‐order transformation, the likelihood of fracture decreases as the cooling rate increases; for a second‐order transition, fracture becomes less probable as the cooling rate decreases. For a mixed transition, an optimum cooling rate can minimize the probab

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14107.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Data on the plasticity and creep of poly crystalline LiF and NaCl are presented; much of the data is drawn from the published literature, but new measurements of hardness as a function of temperature for both materials are also included. The data are fitted to rate equations which describe the mechanisms by which the salts deform. The results are then assembled to give deformation‐mechanism maps which show the regime of stress and temperature over which each mechanism is dominan

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14108.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Solutions of ZnCl2were prepared from ZnCl2·nH2O and by reaction of zinc metal with HCl. Specific gravities and pH values were determined as a function of composition. A ternary phase, 4ZnO·ZnCl2·5H2O, was precipitated when the ZnCl2solutions were diluted to a pH of 5.48 ± 0.05. Mixtures of ZnO with ZnCl, and HCI solutions were equilibrated in sealed containers and analyzed by X‐ray diffraction. The resulting phase diagram shows 2 ternary phases, 4ZnO·ZnCl2·5H2O (4·1·5) and ZnO·ZnCl2·2H2O (1.1.2), both of which are soluble to the extent of<1 wt% in ZnCl2solutions. Thermogravimetric data indicate that the 1.1.2 phase loses half the constituent H2O at ∼230°C and the remainder, with ZnCl2, at higher temperatures. The 4.1.5 phase dissociates to ZnO and 1.1.2 at ∼160°C. The system ZnCl2‐H2O is not binary, but is a section through the ternary system ZnO‐HCl‐H2O, with the solubility curve of the 4.1.5 phase intersecting the ZnCl2‐H2O se

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14109.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Crack damage produced by compressive loads in a dense alumina ceramic was studied with a replication technique that recorded damage done to the specimen's surface. The characteristics of the spalling produced in an externally pressurized, tubular specimen were evaluated at twelve stress levels up to failure. The study revealed that crack extension begins at a compressive stress approximately one quarter of that required to cause failure and that the amount of crack damage increases greatly as the failure stress is approached. The nature of the spalled particles and the mechanisms of spalling are discussed. Mechanisms of compressive failure are suggested.

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14110.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Dispersions have been observed in the ac conductivity of 2 single‐crystal ionic conductors, Naβ‐alumina and LiGaO2. The results have been analyzed in the complex modulus formalism,M°, whereM°= (ε°)−1. It is suggested that these dispersions represent conductivity losses and are similar to those observed in glasses. The losses are related to the mechanism of ion migration and may be a characteristic feature of many ionically conducting crystalline

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14111.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The effect of surface finish on the strength‐grain size relation was investigated for dense hot‐pressed SiC. Failure initiated predominantly via the propagation of extrinsic machining‐induced flaws for the range of grain sizes and machining grit sizes studied. These results are consistent with the region of large‐grain‐size flaw control as delineated by Prochazka and Charles. The severity of machining‐induced flaws, relative to the machining grit size, decreased with increasing machining grit size and decreasing SiC

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14112.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The thermal expansion coefficient and aqueous dissolution rate were measured for alkali phosphate glasses containing a third and fourth component. For a given series, both properties increased monotonically as the radii of the alkali ions increased. The observed expansion coefficients were in the range 99 to 286 × 10−7°C−1. A small mixed‐alkali effect was observed for both pro

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1977.tb14113.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY