Materials Literature
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Se trata de exponer, actualizada a la fecha presente, la creciente actividad científico-técnica (así como los resultados de la misma) en el campo de la fisicoquímica y de la tecnología del CEMENTO, llevada a cabo en Iberoamérica desde 1969 por el Departamento de Química y en parte por el de Materiales, y más recientem…
El estudio del efecto de un determinado aditivo sobre la corrosión de las armaduras, o el de un hormigón con fisuras, o sometido a ambientes marinos o, en fin, de cualquier factor o circunstancia calificada como agresiva, suele exigir un laborioso y extenso programa de trabajo que contemple todas las posibilidades por…
En una publicación anterior (1) se estudió el comportamiento de los morteros correspondientes a dos cementos portland, sometidos a la acción del agua de mar, determinando la evolución de las resistencias mecánicas a flexión; la variación de los coeficientes de corrosión (Koch-Steinegger) a 7, 28 y 56 días; la modifica…
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En un artículo anterior (1) se dio cuenta de los trabajos realizados sobre la influencia que ejerce el CO2 puro en las características químicas, físicas y fisicomecánicas de un cemento portland (P-450) fabricado por la industria española, habiendo probado que tanto el cemento anhidro como el hidratado experimentan una…
Graphite readily forms intercalation compounds with both electron donor and electron acceptor molecules in which intercalated molecules are inserted between the planes of the original graphite structure. These intercalation compounds have been used as catalysts and as reagents in a number of reactions and, in addition…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAbsolute quantum yield determination by thermal blooming. FluoresceinJames H. Brannon and Douglas MagdeCite this: J. Phys. Chem. 1978, 82, 6, 705–709Publication Date (Print):March 1, 1978Publication History Published online1 May 2002Published inissue 1 March 1978https://pubs…
A rapid initial brightness slump and occasional subsequent recovery observed for the zinc-doped zinc oxide phosphor undergoing cathodoluminescence is shown to depend on the surface work function. A quantitative model leads to an explanation of the dependence on surface potential in terms of field-aided or retarded sur…
Methods of determining the free volume fraction of polymers at the glass formation temperature and the concept according to which all polymers have a universal free volume fraction at the glass point are considered critically. The concept of iso-free volume in glass formation can be regarded only as a rough approximat…
We shall review the problems arising during the critical analysis (aimed at selecting recommended values) of the thermodynamic constants of the alkaline-earth titanates, zirconates, and hafnates — a very important class of ferroelectric perovskites, widely used in radio electronics. Recommended values of the following…
Studies are reviewed that employ the effect of an anomalously strong shift of the fundamental K-series x-ray lines associated with a change in the number of 4f electrons in a given atom for investigating the phenomenon of variable valency in compounds of the rare-earth elements in general, and the so-called isomorphou…
The thermal conductivity lambda has been measured for solid phases I to IV of NH 4 F, and the authors have found significant similarities with previous measurements of this quantity for H 2 O. This is discussed in relation to the corresponding phase diagrams and crystal structures.
The theoretical and experimental studies on tetrahedrane — a highly strained compound — are surveyed. The bibliography includes 87 references.
A Slater-Koster tight binding fitting scheme is presented for the band structure of the group V 2H layer compounds. This is used to fit to the 'd' and 'p' bands of NbSe 2 and NbS 2 as calculated by the layer method. Details are given of the symmetrisation throughout the hexagonal Brillouin zone. From the fit the densi…
The phase transition temperatures of identically prepared BaTiO 3 polycrystalline materials (ceramics) doped with the iron group elements are investigated. The valence states and 3d electron configurations of the dopants were determined by means of magnetic susceptibility measurements. The structure stabilities depend…
Presents a pulsed NMR study on a single crystal of 2H-NbSe 2 at atmospheric pressure and under hydrostatic pressure of 21 kbar in the temperature range 4.2-273K. Analysis of Knight shift (KS) and nuclear spin-lattice relaxation (NSLR) time data in the normal state are consistent with N(E F )=2.4 states/eV spin and an…
I show that intrinsic plasmons are created in x-ray photoemission experiments on the conduction bands of simple metals. Unlike the core case, the plasmons are produced by many-body effects and are a direct consequence of electron correlation. A theory of the intrinsic plasmon production is given and a calculation of t…
By direct spatial imaging and spectral analysis of recombination luminescence we have observed in silicon (1) the drift of photoproduced excitons from the crystal surface into a strain potential well; (2) ideal-gas behavior of the strain-confined excitons in the well between 25 and 5 K; (3) a real-space condensation n…
The ordering of Fe ions in the layer crystals FexNbS2 (x ≦ 0.67) is studied as a function of composition and temperature. At the compositions x = 0.25 and 0.67 unexpected phases occur at room temperature in slowly cooled specimens. These crystals undergo order-disorder reactions on heating and in some cases the disord…