Estudio de adhesibilidad entre una aleaci��n de aluminio A319.0 y una camisa de aluminio base Al-Si-Cu-MG. para aplicaciones automotrices

Teis ( Maestro en Ciencias de Ingenier��a Mec��nica con Especialidad en materiales) U.A.N.L.

Efecto de la microestructura y las variables de solidificaci��n sobre el comportamiento a fatiga de alto ciclo en una aleaci��n hipereut��ctica AL-SI-CU-NI.

Tesis (Doctor en Ingenier��a de Materiales) UANL, 2012.

A novel cation induced polymeric chain in Na-8[{Cu(gly)(2)}(2)]{H-2(H2W12O42)}] center dot 24H(2)O: hydrothermal synthesis, spectroscopic characterization and X-ray structure analysis

A novel bis(glycinato) copper(II) paradodecatungstate Na-8[{Cu(gly)(2)}(2)]-{H-2(H2W12O42)}] center dot 24H(2)O (1) has been synthesized under hydrothermal conditions. The crystal structure of 1 reveals an infinite one-dimensional chain along the [100] direction and is built from paradodecatungstate (H2W12O42)(10-) clusters joined through [Cu(gly)(2)] moieties. Parallel chains are interlinked by NaO6 octahedra to generate a two-dimensional network.

Synthesis and X-ray crystal structure of the copper(I) dicarboxylic acid complex [Cu(��1-bdoaH)(PPh3)3] (bdoaH2 = benzene-1,2- dioxyacetic acid)

The copper(II) complex [Cu(bdoa)(H2O)2] (bdoaH2 = benzene-1,2-dioxyacetic acid) reacts with triphenylphosphine (1:4 mol ratio) to give the colourless copper(I) complex [Cu(��1-bdoaH)(PPh3)3] (1) in good yield. The X-ray crystal structure of the complex shows the copper atom at the centre of a distorted tetrahedron, and is ligated by the phosphorus atoms of the three triphenylphosphines and one carboxylate oxygen atom of the bdoaH��� ligand. Significant intermolecular hydrogen-bonding exists between the pendant carboxylate OH function of one molecule and the uncoordinated ���ketonic��� oxygen of a neighbouring molecule. Complex 1 is non-conducting in chloroform but ionizes readily in acetonitrile. The cyclic voltammogram of an acetonitrile solution of 1 shows a single irreversible anodic peak for the oxidation of the PPh3 ligands and the copper(I) centre, and a single irreversible cathodic peak for the reduction of the bdoaH��� ion. IR and mass spectral data for 1 are given.

Facile oxidation of phenylphosphinic acid to phenylphosphonic acid using [Cu2(��-O2CCH3)4(H2O)2]: X-ray crystal structures of monomeric [Cu(PhPO3H)2(C5H5N)4]��2CH3OH and [Cu(PhPO3H)2(C5H5N)4]

Phenylphosphinic acid (HPhPO2H) is oxidized to phenylphosphonic acid (PhPO3H2) at room temperature using a solution of [Cu2(��-O2CCH3)4(H2O)2] in pyridine. The phenylphosphonic acid was recovered as the monomeric copper(II) complex [Cu(PhPO3H)2(C5H5N)4]��H2O (1a), and the reaction thought to proceed via a copper(I) intermediate. Recrystallization of 1a from methanol gave [Cu(PhPO3H)2(C5H5N)4]��2CH3OH (1b). The unsolvated complex [Cu(PhPO3H)2(C5H5N)4] (1c) was prepared by refluxing polymeric [Cu(PhPO3)(H2O)] (2) in pyridine. The X-ray crystal structures of 1b and 1c show that in each of these monomeric complexes the copper(II) ion is ligated by four equatorial pyridine molecules and two axial monoanionic phenylphosphonate groups. A cyclic voltammetric study of 1a revealed a quasi-reversible Cu2+/Cu+ couple with E1/2 = +228 mV (vs Ag/AgCl).

X-ray photoelectron spectroscopy analysis of zirconium nitride-like films prepared on Si(100) substrates by ion beam assisted deposition

Thin zirconium nitride films were prepared on Si(l 00) substrates at room temperature by ion beam assisted deposition with a 2 keV nitrogen ion beam. Arrival rate ratios ARR(N/Zr) used were 0.19, 0.39, 0.92, and 1.86. The chemical composition and bonding structure of the films were analyzed with X-ray photoelectron spectroscopy (XPS). Deconvolution results for Zr 3d, Zr 3p(3/2), N 1s, O 1s, and C 1s XPS spectra indicated self-consistently the presence of metal Zr-0, nitride ZrN, oxide ZrO2, oxymnide Zr2N2O, and carbide ZrC phases, and the amounts of these compounds were influenced by ARR(N/Zr). The chemical composition ratio N/Zr in the film increased with increasing ARR(N/Zr) until ARR(N/Zr) reached 0.92, reflecting the high reactivity of nitrogen in the ion beam, and stayed almost constant for ARR(N/Zr) >= 1, the excess nitrogen being rejected from the growing film. A considerable incorporation of contaminant oxygen and carbon into the depositing film was attributed to the getter effect of zirconium. (C) 2007 Elsevier B.V. All rights reserved.

The role of carbon impurities on the Si(001)-c(4 x 4) surface reconstruction: Theoretical calculations

In this work we employ the state-of-the-art pseudopotential method, within a generalized gradient approximation to the density functional theory, combined with a recently developed method for the calculation of HREELS spectra to study a series of different proposed models for carbon incorporation on the silicon (001) surface. A fully discussion on the geometry, energetics and specially the comparison between experimental and theoretical STM images and electron energy loss spectra indicate that the Si(100)-c(4 x 4) is probably induced by Si-C surface dinners, in agreement with recent experimental findings. (C) 2009 Elsevier B.V. All rights reserved.

Furan interaction with the Si(001)-(2 x 2) surface: structural, energetics, and vibrational spectra from first-principles

In this work we employ the state of the art pseudopotential method, within a generalized gradient approximation to the density functional theory, to investigate the adsorption process of furan on the silicon (001) surface. A direct comparison of different adsorption structures with x-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS), high resolution electron energy loss spectroscopy (HREELS), near edge x-ray absorption fine structure (NEXAFS), and high resolution spectroscopy experimental data allows us to identify the [4 + 2] cycloaddition reaction as the most probable adsorbate. In addition, theoretical scanning tunnelling microscopy (STM) images are presented, with a view to contributing to further experimental investigations.

Photocatalytic decomposition of methylene blue via Fenton mechanisms by silicon wafer doped with Au and Cu: a theoretical and experimental study

In this work, we studied the photocatalytic and the structural aspects of silicon wafers doped with Au and Cu submitted to thermal treatment. The materials were obtained by deposition of metals on Si using the sputtering method followed by fast heating method. The photocatalyst materials were characterized by synchrotron-grazing incidence X-ray fluorescence, ultraviolet-visible spectroscopy, X-ray diffraction, and assays of H(2)O(2) degradation. The doping process decreases the optical band gap of materials and the doping with Au causes structural changes. The best photocatalytic activity was found for thermally treated material doped with Au. Theoretical calculations at density functional theory level are in agreement with the experimental data.

La(2-x)Ce(x)Cu(1-y)Zn(y)O(4) perovskites for high temperature water-gas shift reaction

The performance of La(2-x)Ce(x)Cu(1-y)Zn(y)O(4) perovskites as catalysts for the high temperature water-gas shift reaction (H T-W G S R) was investigated. The catalysts were characterized by EDS, XRD, BET surface area, TPR, and XANES. The results showed that all the perovskites exhibited the La(2)CuO(4) orthorhombic structure, so the Pechini method is suitable for the preparation of pure perovskite. However, the La(1.90)Ce(0.10)CuO(4) perovskite alone, when calcined at 350/700 degrees C, also showed a (La(0.935)Ce(0.065))(2)CuO(4) perovskite with tetragonal structure, which produced a surface area higher than the other perovskites. The perovskites that exhibited the best catalytic performance were those calcined at 350/700 degrees C and, among these, La(1.90)Ce(0.10)CuO(4) was outstanding, probably because of the high surface area associated with the presence of the (La(0.935)Ce(0.065))(2)CuO(4) perovskite with tetragonal structure and orthorhombic La(2)CuO(4) phase.

Estudo da evolu����o estrutural induzida por irradia����o i��nica em multicamadas de Fe/sub 30/Co/sub 70/Cu

Neste trabalho, relata-se o comportamento estrutural de multicamadas de Fe30Co70/Cu, quando submetidas a irradia����es com ��ons de He+ e Kr+ e tratamentos t��rmicos. As multicamadas foram confeccionadas �� temperatura ambiente, numa c��mara de ultra-alto v��cuo por evapora����o alternada de uma liga Fe30Co70 e Cu. As energias das irradia����es foram escolhidas de tal forma que os ��ons atravessassem a multicamada, ficando alojados no substrato de Si. As doses foram calculadas para que os dois tipos de ��ons depositassem a mesma energia total na multicamada. Ap��s a confec����o dos filmes, os mesmos foram submetidos a tratamentos t��rmicos de 10 minutos em temperaturas variando de 350 a 450 oC. Este processo quebra a estrutura de camadas e forma uma liga heterog��nea de gr��os magn��ticos embebidos numa matriz met��lica de Cu. Para investigar a evolu����o das propriedades estruturais das amostras utilizou-se difra����o, refletividade e espectroscopia de absor����o de raios-X. Os resultados da refletividade de raios-X mostraram claramente que uma estrutura de multicamadas �� formada ap��s a evapora����o, fato que �� comprovado pelo pico de Bragg observado nas curvas de refletividade. As irradia����es com He+ e Kr+ n��o destroem a estrutura de multicamadas, ao contr��rio, elas provocam um alisamento de todas as interfaces. Pelas medidas de difra����o de raios-X verificou-se que as irradia����es resultam no aumento de cristalinidade e no crescimento de tamanho dos cristalitos do sistema. A irradia����o com He+ n��o provoca mudan��as significativas na multicamada, mas a irradia����o com Kr+ induz uma transforma����o de fase de bcc para fcc/hcp nas camadas de Fe30Co70. Esta nova fase induzida pela irradia����o com Kr+ �� metaest��vel, pois um simples tratamento t��rmico de 450 oC durante 10 minutos destr��i a nova estrutura fcc/hcp, fazendo com que a liga retorne a estrutura bcc. As medidas de absor����o de raios-X est��o em perfeito acordo com as medidas de difra����o e refletividade, mostrando que as irradia����es promovem uma melhora na ordem cristalogr��fica. De acordo com o que foi observado das medidas, a irradia����o com He+ n��o provoca nenhum efeito significativo na estrutura da liga de FeCo. Contudo, a irradia����o com Kr+ induz uma transforma����o de fase nesta liga de bcc para uma estrutura fcc e/ou hcp. Tal transforma����o �� induzida pela irradia����o com Kr+ porque estes ��ons transferem mais energia, em colis��es nucleares, do que os ��ons de He+. Al��m disso, estes ��ons provocam um grande n��mero de cascatas de colis��es, fazendo com que os ��tomos contidos dentro do volume destas cascatas tornem-se m��veis. Desta forma, os ��tomos de Fe e Co se rearranjam em uma estrutura fcc, que �� imposta pelas camadas de Cu adjacentes. Embora a estrutura fcc seja muito mais prov��vel, tamb��m �� possivel que a estrutura induzida seja hcp.

Paper-based diffusive gradients in thin films technique coupled to energy dispersive X-ray fluorescence spectrometry for the determination of labile Mn, Co, Ni, Cu, Zn and Pb in river water

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Photocatalytic decomposition of methylene blue via Fenton mechanisms by silicon wafer doped with Au and Cu: a theoretical and experimental study

In this work, we studied the photocatalytic and the structural aspects of silicon wafers doped with Au and Cu submitted to thermal treatment. The materials were obtained by deposition of metals on Si using the sputtering method followed by fast heating method. The photocatalyst materials were characterized by synchrotron-grazing incidence X-ray fluorescence, ultraviolet-visible spectroscopy, X-ray diffraction, and assays of H(2)O(2) degradation. The doping process decreases the optical band gap of materials and the doping with Au causes structural changes. The best photocatalytic activity was found for thermally treated material doped with Au. Theoretical calculations at density functional theory level are in agreement with the experimental data.

Adsorption of MX2 (M = Mn, Ni, Cu, Zn, and Cd; X = Cl, Br, and I) and FeCl3 by modified silica surface with imidazolylpropyl group

Silica gel surface modified with imidazolylpropyl group was used to adsorb MX2 (M = Mn, Ni, Cu, Zn, and Cd; X = Cl, Br, and I) and FeCl3 from ethanol and acetone solution. The adsorption capacity and the intensity of the adsorption were determined by using the Langmuir equation. The influences of the solvent, temperature, and degree of functionalization on the adsorption were also studied. The infrared spectra of the functionalized silica were recorded between 1700-1300 cm-1. The bands of the imidazole skeletal vibrations are shifted to higher frequencies upon metal-to-base nitrogen interaction. �� 1985.