PHYSICAL PROPERTIES of TELLURITE GLASSES PREPARED UNDER DIFFERENT THERMAL HISTORIES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermal and pasting properties of cassava starch-dehydrated orange pulp blends

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Red Mud from Brazil: Thermal Behavior and Physical Properties

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

Thermal, structural and optical properties of new tungsten lead-pyrophosphate glasses

Crystalline lead-pyrophosphate precursor was prepared in aqueous solution from lead nitrate and phosphoric acid and characterized by X-ray diffraction, thermogravimetry and Raman scattering. This crystalline lead-phosphate was then used to prepare glass samples in the binary system Pb(2)P(2)O(7)-WO(3). Dependence of WO(3) content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV-visible and near-infrared absorption and M-Line technique to access refractive index values. Incorporation of WO(3) in the lead-pyrophosphate matrix enhances the glass transition temperature and thermal stability against devitrification, favors formation of P-O-W bonds and WO(6) clusters. In addition, optical properties are strongly modified with a redshift of the optical bandgap with WO(3) incorporation as well as an increase of the refractive index from 1.89 to 2.05 in the visible. (C) 2011 Elsevier B.V. All rights reserved.

Effect of addition of different hydrocolloids on pasting, thermal, and rheological properties of cassava starch

Amidos e gomas são hidrocoloides frequentemente usados em sistemas alimentícios com a finalidade de fornecer textura, umidade e mobilidade de água. A interação amido-goma em sistemas alimentícios pode alterar o inchamento do grânulo de amido e as suas propriedades de gelatinização e reológicas. Neste trabalho, o efeito da adição de goma xantana (GX), carboximetilcelulose sódica (CMC) e carragena (CAR) nas concentrações de 0,15, 0,25, 0,35 e 0,45% (p/v) sobre as propriedades de pasta, térmicas e reológicas do amido de mandioca foi estudado. O Poder de inchamento (PI) e a Microscopia Eletrônica de Varredura (MEV) dos géis de amido também foram avaliados. Os resultados obtidos mostraram que a GX apresentou forte interação com o amido, penetrando entre os grânulos e provocando aumento das viscosidades de pasta, PI, G' e G, e redução da retrogradação do amido; CMCS aumentou as viscosidades de pasta, PI, G' e G das misturas, principalmente em função da sua maior capacidade de reter água, e não por causa da interação com o amido; CAR não modificou qualquer das propriedades do amido, porque não houve nenhuma interação entre essa goma e o amido de mandioca nas concentrações usadas.

Thermal and mechanical properties of PVDF/PANI blends

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

Structural carbon/epoxy prepregs properties comparison by thermal and rheological analyses

Two different carbon/epoxy prepreg materials were characterized and compared using thermal (DSC, TGA, and DMA) and rheological analyses. A prepreg system (carbon fiber preimpregnated with epoxy resin F584) that is currently used in the commercial airplane industry was compared with a prepreg system that is a prospective candidate for the same applications (carbon fiber prepreg/epoxy resin 8552). The differences in the curing kinetics mechanisms of both prepreg systems were identified through the DSC, TGA, DMA, and rheological analyses. Based on these thermal analysis techniques, it was verified that the curing of both epoxy resin systems follow a cure kinetic of n order. Even though their reaction heats were found to be slightly different, the kinetics of these systems were nevertheless very similar. The activation energies for both prepreg systems were determined by DSC analysis, using Arrhenius's method, and were found to be quite similar. DMA measurements of the cured prepregs demonstrated that they exhibited similar degrees of cure and different glass transition temperatures. Furthermore, the use of the rheological analysis revealed small differences in the gel temperatures of the two prepreg systems that were examined.

Thermal-optical properties of Ga : La : S glasses measured by thermal lens technique

In this work the quantitative theoretical treatment for two beam mode mismatched thermal lens spectrometry is applied to investigate the thermo-optical properties of chalcohalide (chalcolgenides and halides mixture) glasses. For the three kinds of glass studied the thermal diffusivity varied between 2.5 and 2.7 x 10(-3) cm(2) s(-1). Using these results and supposing Dulong-Petit specific heats we estimated the thermal conductivity and temperature ratio of optical path length (ds/dT) and temperature coefficient of refractive index (dn/dT). All samples had positive ds/dT(similar to 3.3 x 10(-6) K-1) and negative dn/dT (similar to -26 x 10(-6) K-1). The difference between these parameters and the change of signal are consequences of the expansion coefficient (13 x 10(-6) K-1) and refractive index (n similar to 2.6) of chalcohalides. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Analytic properties of thermal corrected boson propagators

We investigate the analytic properties of finite-temperature self-energies of bosons interacting with fermions at one-loop order. A simple boson-fermion model was chosen due to its interesting features of having two distinct couplings of bosons with fermions. This leads to a quite different analytic behavior of the bosons self-energies as the external momentum K-mu=(k(0),k) approaches zero in the two possible limits. It is shown that the plasmon and Debye masses are consistently obtained at the pole of the corrected propagator even when the self-energy is analytic at the origin in the frequency-momentum space.

Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO4 Crystals and Their Optical Properties

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

Effects of thermal annealing on the semi-insulating properties of radio frequency magnetron sputtering-produced germanate thin films

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural refinement, growth process, photoluminescence and photocatalytic properties of (Ba1-xPr2x/3)WO4 crystals synthesized by the coprecipitation method

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

Structural and electrical properties of strontium barium niobate thin films crystallized by conventional furnace and rapid-thermal annealing process

Strontium barium niobate (SBN) thin films were crystallized by conventional electric furnace annealing and by rapid-thermal annealing (RTA) at different temperatures. The average grain size of films was 70 nm and thickness around 500 nm. Using x-ray diffraction, we identified the presence of polycrystalline SBN phase for films annealed from 500 to 700 °C in both cases. Phases such as SrNb2O6 and BaNb2O6 were predominantly crystallized in films annealed at 500 °C, disappearing at higher temperatures. Dielectric and ferroelectric parameters obtained from films crystallized by conventional furnace and RTA presented essentially the same values.

Effect of thermal treatment under oxygen atmosphere on the superconducting properties of RuSr2GdCu2O8

The discovery of the spatial uniform coexistence of superconductivity and ferromagnetism in rutheno-cuprates, RuSr2GdCu2O8 (Ru-1212), has spurred an extraordinary development in the study of the competition between magnetism and superconductivity. However, several points of their preparation process and characterization that determine their superconductive behavior are still obscure. The improvement of sample preparation conditions involves some thermal treatments in inert atmosphere. The first treatment results in the immediate formation of Sr2GdRuO 6. Using the CuO composition as a precursor, we produced Ru-1212. To turn it metallic and superconductor, besides the previous treatment, a final sinterization is carried out in oxygen flow for several days. Three Ru-1212 samples were produced by varying the last sinterization time (two, four, and six days under oxygen flow). Through measurements of x-ray diffraction, scanning electron microscopy, differential thermal analysis, magnetic susceptibility and mechanical spectroscopy, it was studied the influence of the treatments under oxygen atmosphere on the structural and superconducting properties of the material.

Structural refinement and photoluminescence properties of cube-like (Ca 1-xCu x)TiO 3 crystals synthesized by the microwave-hydrothermal method

In this work, (Ca 1-xCu x)TiO 3 crystals with (x = 0, 0.01 and 0.02), labeled as CTO, CCTO1 and CCTO2, were synthesized by the microwave-hydrothermal method at 140°C for 32 min. XRD patterns (Fig. 1), Rietveld refinement and FT-Raman spectroscopy indicated that these crystals present orthorhombic structure Pbnm. Micro-Raman and XANES spectra suggested that the substitution of Ca by Cu in A-site promoted a displacement of the [TiO6]-[TiO6] clusters adjacent from its symmetric center, which leads distortions on the [CaO 12] clusters neighboring and consequently cause the strains into the CaTiO3 lattice. FE-SEM images showed that these crystals have an irregular shape as cube like probably indicating an Ostwald-ripening and self-assemble as dominant mechanisms to crystals growth. The powders presented an intense PL blue-emission.