Tabla de frecuencias y espectros de absorción infrarroja de compuestos relacionados con la química del cemento
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Materials Literature
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Contribución al conocimiento del falso fraguado. Efectos de la langbeinita cálcica producida durante la clinkerización
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Productos formados en un hormigón no reciente
Estudio de un cemento de las ruinas de Teotihuacan
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Corrosión de armaduras galvanizadas y sin proteger embebidas en cemento aluminoso estabilizado
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Grain‐Size Dependence of Fracture Energy in Ceramics: I, Experiment
Evaluation of literature data combined with new experimental measurements shows that crystal structure is a basic factor in the grain‐size dependence of the critical fracture energy of ceramics. Notch beam (NB), double cantilever beam (DCB), and work‐of‐fracture (WOF) tests of materials having a cubic crystal structur…
Quantitative methods for electron microprobe analysis of sodium in natural and synthetic glasses
Two methods have been developed for the microprobe analysis of Sodium in natural and synthetic glasses that exhibit time-dependent element migration during electron bombardment. A cryogenic method is based on the cooling of the sample to -90oC at which temperature sodium diffusion rate from the excitation volume is re…
A Point Defect Model for Anodic Passive Films: II . Chemical Breakdown and Pit Initiation
The point defect model that was previously developed (1) to explain the growth kinetics of a passive film has been extended to account for chemical breakdown. This model provides quantitative explanations of the dependence of breakdown potential on halide concentration, and of the incubation time‐breakdown overpotenti…
A Point Defect Model for Anodic Passive Films: I . Film Growth Kinetics
A model based on the movement of point defects in an electrostatic field is proposed to interpret the growth behavior of a passive film on a metal surface. This model results in a logarithmic growth law. The theoretical equations derived from the model readily account for experimental data for the growth of a passive…
Spin-polarised low-energy electron diffraction
A review is given of elastic spin-polarised low-energy electron diffraction (SPLEED) from crystalline surfaces. For the two relevant spin-dependent interaction mechanisms, spin-orbit coupling, and exchange, dynamical theories are presented with emphasis on symmetry principles, potential models and multiple scattering…
Photocurrent Transient Spectroscopy: Measurement of the Density of Localized States ina-As2Se3
Measurements of transient photoinduced optical absorption in $a$-${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ show that carriers thermalize within a distribution of localized states in the band gap. Photocurrent as well as photoinduced optical absorption transients are explained in a unified way with the multiple-trapping m…
Sodium ion migration in glass on electron beam irradiation
The phenomenon of electromigration of atomic species during AES of glasses is discussed, and the induction time T i , before any migration occurs, is defined theoretically for the two possible directions of migration. Experimental Auger peak shapes are shown to exhibit a growing asymmetry with irradiation time, in suc…
Synthesis and characterization of poly(keto‐amines). 1. Self polycondensation of 4‐aminophenacyl chloride
Abstract Novel poly(keto‐amines), designated as poly(4‐iminophenacyls) are prepared by self polycondensation of 4‐aminophenacyl chloride under different experimental conditions. These polymers are insoluble in common solvents. The number average molecular weights of the polymer samples have been estimated by conductom…
Electron Hopping Conduction in the Soliton Model of Polyacetylene
It is shown that at low temperatures, phonon-assisted electron hopping between soliton bound states may be the dominant conduction process in a lightly doped, one-dimensional Peierls system such as polyacetylene. The presence of disorder, as represented by a spatially random distribution of charged dopant molecules, c…
Correlation between structural defects and optical properties in ion-implanted silicon
Measurements of optical transmission and reflection spectra and Rutherford baokscattering experiments (RBS) are performed to investigate the influence of radiation damage on optical properties of silicon crystals implanted with Ar+-, P+-, and B+-ions at different temperatures (Ti = 77; 300; 500 K). At sufficiently low…
Transport properties of lithium and sodium doped nickel oxide
The electrical resistivity and thermoelectric power of ceramic samples of NiO doped with Li and Na are studied as function of temperature and dopant concentration. The resistivity ∂ is measured in the temperature range 100 to 700 K and thermoelectric power α in the range 100 to 300 K. The results obtained indicate ban…
X-ray temperature study of crystallographic characteristics of Barium Titanate
A precise experimental diffractometric study of unit cell parameters of polycrystalline BaTiO3 in the temperature range from −170 to 220 °C is made, using an X-ray diffraction line refinement computer method. The values of unit cell volume jump, the widths of phase coexistence regions, and the hysteresis characteristi…
Statistical treatment of EPR data: The spectrum of IO2 in KIO2F2 single crystals
The EPR spctrum in γ-irradiated KIO2F2 crystals has been reinvestigated. Originally thought to be due to IO2F−, the spectrum has been reanalyzed and reassigned to the radical IO2. Improved principal values for the g factor and the 127I hyperfine and quadrupole interactions were obtained by the statistical technique of…
The intermolecular arrangement in the plastic crystal (phase Ia) of carbon tetrachloride studied by x-ray diffraction
The x-ray diffraction pattern of the CCl4 plastic crystal (fcc), consisting of halos and a few sharp peaks, was observed by using an energy-dispersive method at −30 °C and the halo pattern was analyzed. The observed intensity was explained by the ’’head–tail head–tail model.’’ This arrangement is consistent with the l…
EPR and a b i n i t i o SCF–MO studies of the Si⋅H–Si system in the E′4 center of α-quartz
The E′4 center in irradiated α-quartz has been studied by single-crystal EPR. The unpaired electron is shared mainly by two silicon ions Si(1, 2) with the larger fraction on Si(2). The spin-Hamiltonian parameter matrices ḡ, Ā1H, Ā29Si(1, 2) at 40 K, as well as Ā29Si(1, 2) at 300 K, are reported. A model of the E4′ cen…