Effect of silica coating combined to a MDP-based primer on the resin bond to Y-TZP ceramic

The aim of this study was to evaluate the influence of silica coating and 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer applications upon the bonding durability of a MDP-based resin cement to a yttrium stabilized tetragonal zirconia (Y-TZP) ceramic. Ninety-six Y-TZP tabs were embedded in an acrylic resin (free surface for adhesion: 5 x 5 mm(2)), ground finished and randomly divided into four groups (N = 24) according to the ceramic surface conditioning: (1) cleaning with isopropanol (ALC); (2) ALC + phosphoric acid etching + MDP-based primer application (MDP-primer); (3) silica coating + 3-methacryloyloxypropyl trimethoxysilane (MPS)-based coupling agent application (SiO(2) + MPS-Sil); and (4) SiO(2) + MDP-primer. The MDP-based resin cement was applied on the treated surface using a cylindrical mold (diameter=3 mm). Half of the specimens from each surface conditioning were stored in distilled water (37 C, 24 h) before testing. Another half of the specimens were stored (90 days) and thermo-cycled (12,000x) during this period (90d/TC) before testing. A shear bond strength (SBS) test was performed at a crosshead speed of 0.5 mm/min. Two factors composed the experimental design: ceramic conditioning strategy (in four levels) and storage condition (in two levels), totaling eight groups. After 90d/TC (Tukey; p < 0.05), SiO(2) + MDP-primer (24.40 MPa) promoted the highest SBS. The ALC and MDP-primer groups debonded spontaneously during 90d/TC. Bonding values were higher and more stable in the SiO2 groups. The use of MDP-primer after silica coating increased the bond strength. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part 8: Appl Biomater 95B: 69-74, 2010.

Mixing of superconducting d(x2-y2) state with s-wave states for different filling and temperature

We study the order parameter for mixed-symmetry states involving a major d(x2-y2) state and various minor s-wave states (s, s(xy), and Sx2+y2) for different filling and temperature for mixing angles 0 and pi /2. We employ a two-dimensional tight-binding model incorporating second-neighbor hopping for tetragonal and orthorhombic lattice. There is mixing for the symmetric s state both on tetragonal and orthorhombic lattice. The s(xy) state mixes with the d(x2-y2) state only on orthorhombic lattice. The s(x2+y2) state never mixes with the d(x2-y2) state. The temperature dependence of the order parameters is also studied. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Mixing of d(x)(-y)(2)(2) and d(xy) superconducting states for different filling and temperature

We investigate the solution of the gap equation for mixed order parameter symmetry states as a function of filling using a two-dimensional tight-binding model incorporating second-neighbor hopping for tetragonal and orthorhombic lattice, the principal (major) component of the order parameter is taken to be of the d(x2-y2) type, As suggested in several investigations the minor component of the order parameter is taken to be of the d(xy) type. Both the permissible mixing angles 0 and pi/2 between the two components are considered. As a function of filling pronounced maxima of d(x2-y2) order parameter is accompanied by minima of the d(xy) order parameter. At fixed filling. The temperature dependence of the two components of the order parameter is also studied in all cases. The variation of critical temperature T, with filling is also studied and T-c is found to increase with second-neighbor hopping. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Síntese e caracterização da cerâmica PZT dopada com íons bário

Pós de titanato zirconato de chumbo (PZT) puros e dopados com bário foram obtidos pelo método de precursores poliméricos, conformados uniaxialmente, na forma de cilindros, utilizando 15 MPa, e prensados isostaticamente à 210MPa. Com o objetivo de estudar o comportamento de sinterização os compactos foram divididos em dois lotes. Sendo um sinterizado em um forno acoplado a um dilatômetro até a temperatura de 1300 °C e o outro sinterizado em forno tipo mufla, em sistema fechado, na temperatura de 1100 °C por 4 horas. Verificou-se que a adição do íon bário influencia na cinética de sinterização, na densificação final, na microestrutura e nas propriedades elétricas da cerâmica. A adição de bário aumenta a concentração da fase tetragonal no PZT, em função da substituição do chumbo por bário na rede perovskita. As amostras dopadas com concentrações maiores que 5,0 mol % em bário apresentaram segregação de PbO no contorno de grão, inibindo seu crescimento.

Morphology and Blue Photoluminescence Emission of PbMoO4 Processed in Conventional Hydrothermal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanosized lead lanthanum titanate (PLT) ceramic powders synthesized by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and dielectric characterization of praseodymium-modified lead titanate ceramics synthesized by the OPM route

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of lead zirconate titanate powders obtained by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure of nanoporous zirconia-based powders synthesized by different gel-combustion routes

Zirconia-based ceramics that retain their metastable tetragonal phase at room temperature are widely studied due to their excellent mechanical and electrical properties. When these materials are prepared from precursor nanopowders with high specific surface areas, this phase is retained in dense ceramic bodies. In this work, we present a morphological study of nanocrystalline ZrO2-2.8 mol% Y2O3 powders synthesized by the gel-combustion method, using different organic fuels - alanine, glycine, lysine and citric acid - and calcined at temperatures ranging from 873 to 1173 K. The nanopore structures were investigated by small-angle X-ray scattering. The experimental results indicate that nanopores in samples prepared with alanine, glycine and lysine have an essentially single-mode volume distribution for calcination temperatures up to 1073 K, while those calcined at 1173 K exhibit a more complex and wider volume distribution. The volume-weighted average of the nanopore radii monotonically increases with increasing calcination temperature. The samples prepared with citric acid exhibit a size distribution much wider than the others. The Brunauer-Emmett-Teller technique was used to determine specific surface area and X-ray diffraction, environmental scanning electron microscopy and transmission electron microscopy were also employed for a complete characterization of the samples.

Synthesis, characterization, structural refinement and optical absorption behavior of PbWO(4) powders

The present paper describes the synthesis, characterization, structural refinement and optical absorption behavior of lead tungstate (PbWO(4)) powders obtained by the complex polymerization method heat treated at different temperatures for 2h in air atmosphere. PbWO(4) powders were characterized by X-ray diffraction (XRD), Rietveld refinement, Fourier transform Raman (FT-Raman) spectroscopy and ultraviolet visible (UV-vis) absorption spectroscopy measurements. XRD, Rietveld refinement and FT-Raman revealed that PbWO(4) powders are free of secondary phases and crystallizes in a tetragonal structure. The UV-vis absorption spectroscopy measurements suggest the presence of intermediary energy levels into the band gap of structurally disordered powders. (C) 2008 Elsevier B.V. All rights reserved.

Rietveld analysis of mechanically activated BaCO(3)-TiO(2) system

BaTiO(3) powders were prepared through mechanical activation chemistry and analyzed by Rietveld refinement with X-ray diffraction data. Raw BaCO(3) and TiO(2) powders were dry milled for 5 and 20 h and then calcinated for 2 and 4 h at 800 degrees C. The milling process was found to have broken up the BaCO(3) and TiO(2) crystals into smaller crystals and formed only small amounts ( 1.5 wt%) of BaTiO(3). Subsequence calcinations for 2 and 4 h at 800 degrees C successfully produced large amounts (>97.7 wt%) of BaTiO(3) crystals. The calcination process also generated microstrains and crystallite-size anisotropy in BaTiO(3). An increase in the calcination time from 2 to 4 h increased the BaTiO(3) weight percentage and the crystal lite-shape anisotropy, but decreased the tetragonal distortion anisotropic microstrains in BaTiO(3) crystals. (C) 2008 International Centre for Diffraction Data.

Microwave-hydrothermal synthesis of barium strontium titanate nanoparticles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SnO2 nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A Joint Experimental and Theoretical Study on the Nanomorphology of CaWO4 Crystals

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SrMoO4 powders processed in microwave-hydrothermal: Synthesis, characterization and optical properties

In this work, we report on the synthesis of SrMoO4 powders by co-precipitation method and processed in a microwave-hydrothermal at 413 K for 5 h. These powders were analyzed by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman), ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL). XRD analyses revealed that the SrMoO4 powders are free of secondary phases and crystallize in a tetragonal structure. FT-Raman investigations showed the presence of Raman-active vibration modes correspondent for this molybdate. UV-vis technique was employed to determine the optical band gap of this material. SrMoO4 powders exhibit an intense PL emission at room temperature with maximum peak at 540 nm (green region) when excited by 488 nm wavelength of an argon ion laser. (C) 2007 Elsevier B.V. All rights reserved.