Materials Literature
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The historical heritage of our country is mainly made up of masonry, playing the sandstones an important role. However, because of the effect of environmental conditions and pollution, these materials can loose their cement, and eventually disintegrate. Chemical consolidants can be applied in order to prevent and stop…
A detailed study of the alteration causes in the stone material used in buildings and pavements from the ancient roman town of Baelo Claudia (Cádiz, South Spain) was carried out to establish their degree of conservation. Slabs from the pavement of the Forum showed in general a high and irreversible degree of degradati…
The kinetics of formation of disordered arrays of hemispherically shaped islands of cesium chloride on an oxidized silicon wafer, starting from a deposited thin film of CsCl, has been investigated. The essential process step is the exposure of the CsCl thin film to water vapor. Transport of dissolved material in the a…
Summary Subantarctica is situated between the Antarctic and the Subtropical Convergence and consists of the islands in the southern Atlantic, Indian and Pacific Oceans. Diatoms are an important component of all Subantarctic aquatic, moss and soil habitats. Taxonomic studies reveal a high diversity and species richness…
The spherically averaged structure function $S(|\mathbf{q}|)$ obtained from pulsed neutron powder diffraction contains both elastic and inelastic scattering via an integral over energy. The Fourier transformation of $S(|\mathbf{q}|)$ to real space, as is done in the pair density function (PDF) analysis, regularizes th…
The Mayer diagrammatic expansion for a classical pair-interacting fluid in thermal equilibrium is cast in a form particularly appropriate to high-dimensional space. At asymptotically high dimensionality, the series, when it converges, is dominated by a single term. Focusing upon repulsive interactions, the dominant te…
Abstract Infrared reflectance spectra of Li-, Na-, K-, Rb- and Cs-saturated samples of montmorillonite Zenith-N (Milos, Greece) have been measured in the 400–1300 cm -1 region in an attempt to elucidate the behaviour and migration properties of alkali cations after heating the montmorillonites at 300°C for 24 h. Decon…
Flexible metallic plastic sheets and filmsof two high-strength conducting polymers, polythiophene and poly(p-phenylene), are discussed. The synthetic procedure—electropolymerization in boron trifluoride diethyl etherate solution—is believed to be the key to the exceptional mechanical properties of these materials, whi…
Columnar and highly oriented (100) BaTiO 3 and SrTiO 3 thin films were prepared by a chelate‐type chemical solution deposition (CSD) process by manipulation of film deposition conditions and seeded growth techniques. Randomly oriented columnar films were prepared on platinum‐coated Si substrates by a multilayering pro…
Este trabalho objetivou estudar a relação entre os constituintes mineralógicos da fração argila e o desenvolvimento da micro e macroestrutura de Latossolos do sudeste brasileiro. Para tanto, foram obtidas amostras do horizonte B de sete Latossolos, representativos deste grupamento, ocorrentes nos estados de Minas Gera…
The structure and chemistry of what initially was proposed to be Ti 3 Al 2 N 2 are incorrect. Using high‐resolution transmission electron microscopy, together with chemical analysis, the stoichiometry of this compound is concluded to be Ti 4 AlN 3‐delta (where delta = 0.1). The structure is layered, wherein every four…
Many commercial products change color with a change of temperature. How do they do it? The processes responsible for the two major categories of commercial thermochromic coloring agents are presented, along with a description of applications of thermochromic materials.
The combined effects of hole doping and magnetic dilution on a lamellar Heisenberg antiferromagnet are studied in the framework of the frustration model. Magnetic vacancies are argued to remove some of the frustrating bonds generated by the holes, thus explaining the increase in the temperature and concentration range…
The mechanical resistance of a polyethylene strand subject to tension and the way its properties are affected by the presence of a knot is studied using first-principles molecular dynamics calculations. The distribution of strain energy for the knotted chains has a well-defined shape that is very different from the on…
We have studied the interplay between orbital ordering, Jahn-Teller and ${\mathrm{GdFeO}}_{3}$-type lattice distortions in perovskite-type transition-metal oxides using model Hartree-Fock calculations. It has been found that the covalency between A-site cations and oxygens causes interaction between the Jahn-Teller an…
We performed first-principles relativistic full-potential linearized augmented plane-wave calculations for strained tetragonal ferromagnetic $\mathrm{La}(\mathrm{Ba}){\mathrm{MnO}}_{3}$ with an assumed experimental structure of thin strained tetragonal ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ (LCMO…
Charge-ordered manganites of composition $\rm Pr_{1-x}(Ca_{1-y}Sr_{y})_{x}MnO_3$ exhibit persistent photoconductivity upon exposure to x-rays. This is not always accompanied by a significant increase in the {\it number} of conduction electrons as predicted by conventional models of persistent photoconductivity. An ana…
Transition lines between various phases in the electric-field--temperature phase diagram of 9/65/35 lanthanum-modified lead zirconate titanate ceramics were determined by measurements of the temperature and electric-field-dependent dielectric constant. Above a critical field ${(E}_{C})$ the dc bias electric field indu…
Molecular-dynamics simulations of fracture in systems akin to metallic glasses are observed to undergo embrittlement due to a small change in interatomic potential. This change in fracture toughness, however, is not accompanied by a corresponding change in flow stress. Theories of brittle fracture proposed by Freund a…