Materials Literature
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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…
To investigate new architectures for molecular photonics applications, a shape-persistent cyclic hexameric architecture ( cyclo -Zn 3 Fb 3 U- p/m ) has been prepared that is comprised of three free base (Fb) porphyrins and three zinc porphyrins linked at the meso -positions via diphenylethyne units. The synthesis invo…
The synthesis and characterization of latex particles consisting of a poly(styrene) (PS) core and a shell of linear poly(acrylic acid) (PAA) chains are described. The particles have been synthesized by photoemulsion polymerization of acrylic acid on PS core particles containing a thin shell of the photoinitiator 2-[ p…
Poly(lactic acids) (PLAs) are a family of polyesters available via fermentation from renewable resources and are the subject of considerable recent commercial attention. In this study, the melt rheological properties of a family of poly(lactic acid) stars are investigated and compared to the properties of the linear m…
Based on anionic group theory, a computer-assisted material design system (CAMDS) has been developed. This method has proved to be a highly efficient means of discovering nonlinear optical crystals. In this method, important optical properties of the target compounds (borates, for example), such as the dij coefficient…
Dielectric and piezoelectric properties of BaTiO3 single crystals polarized along the 〈001〉 crystallographic axes were investigated as a function of temperature and dc bias. Electromechanical coupling (k33)∼85% and piezoelectric coefficients (d33)∼500 pC/N, better or comparable to those of lead-based Pb(Zr, Ti)O3 (PZT…
Abstract The strong influence of relatively small amounts of filler particles, such as carbon black, on the mechanical properties of elastomers has been well known for decades and has significantly contributed to increased use of elastomeric materials in many commercial applications. Even though the use of fillers is…
Rietveld refinements using 12 sets of X-ray diffraction powder data from milligram samples of human dental enamel provide detailed information about the structure and composition of enamel apatite. The principal difference in atomic parameters between enamel apatite and Holly Springs hydroxylapatite is in O2, which is…
Many of the MR examinations performed in the world each year are accompanied by administration of one of these frequently used intravenous contrast agents: Magnevist, Omniscan, and ProHance. Accordingly, MR practitioners must understand the basic pharmacokinetics, side effects, and the potential for adverse events for…
Growth in polypropylene usage as a cost effective replacement of engineering polymers polypropylene - structure, properties, applications chemical coupling agents for filled and GR-PP composites stabilization of flame retarded polypropylene effects of processing and microstructuring in recycled polypropylene and its b…
Three different water−alcohol cosolvent systems were used to assemble mesoporous molecular sieve silicas with wormhole framework structures (previously denoted HMS silicas) from an electrically neutral amine surfactant (S°) and a silicon alkoxide precursor (I°). The fundamental particle size and associated textural (i…