Materials Literature
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The spectral dependence of the absorption coefficient of silicon for photon energies up to 2.7 eV was determined for several temperatures in the range 298–473 K. The effect of a temperature increase appears as a red shift of the absorption spectrum. The magnitude of the shift is larger than that of the fundamental ene…
El autor expone, en esta primera parte, la cuestión desde el punto de vista del fabricante limitándose a las consecuencias apreciables en las cualidades del hormigón. Trata de responder a dos preguntas: ¿Por qué se debe cambiar el contenido de aluminato tricálcico de un cemento? ¿Qué beneficios, o que perjuicios, prod…
Se puede afirmar que la durabilidad del hormigón está principalmente condicionada a su compacidad y a su aislamiento de los ambientes agresivos. Los agentes destructores endógenos se consideran eliminados cuando el hormigón está preparado correctamente, con materiales durables y técnica perfecta de amasado, colocación…
Las numerosas consultas de constructores que, para amasar sus hormigones, no disponían de agua exenta de impurezas, movieron nuestra curiosidad a ensayar, en la División de Durabilidad del Departamento de Química en el lETcc, la influencia que algunas sales disueltas en el agua de amasado ejercen sobre las propiedades…
Con motivo de una probable normalización de cementos portland con adiciones de finos silícicos, puzolanas y cenizas volantes hasta un 35%, el Laboratorio Central de Puentes y Caminos realizó un estudio para poner de manifiesto, en forma cuantitativa, la influencia de las diversas adiciones sobre las características, n…
El Prof. P. K. Mehta ha puesto de manifiesto que las cenizas de las cascaras del arroz tienen las propiedades de una sílice muy reactiva.
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The carbonation‐reaction kinetics of beta‐dicalcium silicate (2CaO·SiO 2 or β‐C 2 S) and tricalcium silicate (3CaO. SiO 2 or C 3 S) powders were determined as a function of material parameters and reaction conditions and an equation was developed which predicted the degree of reaction. The effect of relative humidity,…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCis-trans photoisomerization of azobenzene. Solvent and triplet donors effectsPietro. Bortolus and Sandra. MontiCite this: J. Phys. Chem. 1979, 83, 6, 648–652Publication Date (Print):March 1, 1979Publication History Published online1 May 2002Published inissue 1 March 1979htt…
A review of the available electrical and structural data on both pure and doped 1T-TaS2 leads us to propose that the nearly commensurate to commensurate transition at 200 K is accompanied by Mott localization in two dimensions. One electron out of 13 in the Ta plane is localized onto the centre of a star of 13 Ta atom…
We consider a system of rodlike molecules interacting with a model pair potential $\ensuremath{\varphi}(\frac{r}{\ensuremath{\sigma}})$, where $r$ is the center-of-mass distance and $\ensuremath{\sigma}$ is an angle-dependent range parameter. It is shown that if the pair correlation function $g$ scales as $g(\frac{r}{…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe difference between metallic and insulating salts of tetracyanoquinodimethone (TCNQ): how to design an organic metalJerry B. TorranceCite this: Acc. Chem. Res. 1979, 12, 3, 79–86Publication Date (Print):March 1, 1979Publication History Published online1 May 2002Published…
Abstract Sandstones and shales of the Wilcox Group (lower Eocene) in southwest Texas were examined by X-ray powder diffraction, electron microprobe, and petrographically to interpret their diagenetic history. Samples analyzed are from depths of 975 to 4650 m, representing a temperature range of 55 degrees C to 210 deg…
A first-principles order-parameter theory of the fluid-solid transition is presented in this paper. The thermodynamic potential $\ensuremath{\Omega}$ of the system is computed as a function of order parameters ${\ensuremath{\lambda}}_{i}(={\ensuremath{\lambda}}_{{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}_{i}})$…
A theory of dislocation-mediated melting in two dimensions is described in detail, with an emphasis on results for triangular lattices on both smooth and periodic substrates. The transition from solid to liquid on a smooth substrate takes place in two steps with increasing temperatures. Dissociation of dislocation pai…
The computational and theoretical studies in the field of homogeneous polycondensation are subjected to a critical analysis on the basis of the universal classification of the kinetic and thermodynamic models used in this field. The limits of the applicability of the models are discussed from the standpoint of the phy…
A review is presented of the theory of optical properties of cholesteric liquid crystals (CLC). The diffraction nature of the unusual optical properties of CLC is exhibited in the simplest and most easily visualizable kinematic approximation of diffraction theory. A quantitative description of the optical properties i…