Evaluation and Application of TS-FF-AAS System Using Ceramic Tube as Atomization Cell for Tin Determination in Canned Foods

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

Color tunability of intense upconversion emission from Er3+-Yb3+ co-doped SiO2-Ta2O5 glass ceramic planar waveguides

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

Erbium-activated silica-zirconia planar waveguides prepared by sol-gel route

Er(3+) doped (100-x)SiO(2)-xZrO(2) planar waveguides were prepared by the sol-gel route, with x ranging from 10 up to 30 mol%. Multilayer films doped with 0.3 mol% Er(3+) ions were deposited on fused quartz substrates by the dip-coating technique. The thickness and refractive index were measured by m-line spectroscopy at different wavelengths. The fabrication protocol was optimized in order to confine one propagating mode at 1.5 mu m. Photoluminescence in the near and visible region indicated a crystalline local environment for the Er(3+) ion. (c) 2007 Elsevier B.V. All rights reserved.

Upconversion luminescence in Er3+ doped and Er3+/Yb3+ codoped zirconia and hafnia nanocrystals excited at 980 nm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese do anodo cerâmico La1-xSr xCr0,5Mn0,5O3 pela técnica dos precursores poliméricos

Compostos da família La1-xSr xCr0,5Mn0,5O3 são apontados como potenciais anodos cerâmicos de células a combustível de óxidos sólidos. A utilização de anodos cerâmicos tem como objetivo eliminar os problemas de depósito de carbono na superfície do níquel e a baixa resistência a ciclos de redução/oxidação observados no compósito cerâmica-metal à base de zircônia estabilizada e níquel, que é o material anódico mais usado nestas células. Neste estudo são apresentados os resultados da síntese pela técnica dos precursores poliméricos e da caracterização de compostos com x = 0,5, estequiométrico e com 5% de deficiência catiônica no sítio A da estrutura perovskita La1-xSr xCr0,5Mn0,5O3 e (La1-xSr x)0,95Cr0,5Mn0,5O3, respectivamente. Os resultados evidenciam que o composto estudado possui altos valores de condutividade elétrica e baixa reatividade com eletrólitos à base de zircônia.

Mineralogical characterization of clays used in the structural ceramic industry in west of S. Paulo State, Brazil

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

Si3N4 ceramic cutting tool sintered with CeO2 and Al2O3 additives with AlCrN coating

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

Planar and UV written channel optical waveguides prepared with siloxane poly(oxyethylene)-zirconia organic-inorganic hybrids. Structure and optical properties

Organic-inorganic hybrids were prepared using ureapropyltriethoxysilane, methacryloxypropyltrimethoxysilane and acrylic acid modified zirconium(IV) n-propoxide precursors and were characterized by small angle X-ray scattering, X-ray diffraction and photoluminescence spectroscopy. The results indicate an effective interaction between the zirconium-based nanoparticles and the siliceous nanodomains that induces changes in the hybrids' emission features. Planar waveguides were obtained by spin-coating of the prepared sols on sodalime and silica substrates. Refractive index, thickness, number of propagating modes, and attenuation coefficient were measured at 543.5, 632.8 and 1550 nm by the prism coupling technique. The synergism between the two hybrid precursors resulted in monomode planar waveguides with low losses in the infrared ( from 0.6-1.1 dB cm(-1)) which also support a number of propagating modes in the visible ( losses from 0.4-1.5 dB cm(-1)). Channel waveguides were also obtained by UV photopatterning using amplitude or phase masks and propagating modes were observed at 1550 nm.

ac conductivity and conduction mechanism of NaNbO3 semiconductor antiferroelectric ceramic: A relaxational approach at high temperature

The electric properties of the sodium niobate perovskite ceramic were investigated by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz and from room temperature up to 1073 K, in a thermal cycle. Both capacitance and conductivity exhibit an anomaly at around 600 K as a function of the temperature and frequency. The electric conductivity as a function of angular frequency sigma(omega) follows the relation sigma(omega)=Aomega(s). The values of the exponent s lie in the range 0.15less than or equal tosless than or equal to0.44. These results were discussed considering the conduction mechanism as being a type of polaron hopping. (C) 2003 American Institute of Physics.

Mechanochemical synthesis of ceramic powders with perovskite structure

The mechanical activation is one of the most effective method for obtaining highly disperse system due to mechanical action stress fields form in solids during milling procedure. This effect results in changes of free energy, leading to release of heat, formation of a new surface, formation of different crystal lattice defects and initiation of solid-state chemical reaction. The accumulated deformation energy determines irreversible changes of crystal structure and consequently microstructure resulting in the change of their properties. Mechanochemical processing route has been developed recently for the production of intermetallic and alloy compounds. The intrinsic advantage of this process is that the solid-state reaction is activated due to mechanical energy instead of the temperature. It was shown that the chemical reactivity of starting materials could be improved significantly after mechanochemical activation and, subsequently, the calcination temperature was reduced. Besides, it was apparent that the mechanochemical treatment could enhance the reactivity of constituent oxides; however, the sintering process could not be avoided to develop the desired ceramics. A novel mechanochemical technique for synthesis of fine-grained perovskite structured powders has shown that it is possible to form perovskite at room temperature. The effect of milling on the formation of perovskite structure of barium titanate (BT), lead titanate (PT), PZT, PZN, magnesium niobate (PMN) and LM ceramic materials was analyzed. The dielectric properties of sintered ceramics are comparable with those prepared by other methods in the literature. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Comparison of metallic and ceramic tubes as atomization cells for tin determination by TS-FF-AAS

This work describes the development of an analytical procedure for on-line tin determination using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). Two tubes were evaluated as atomization cells: a metallic tube (Ni-Cr, principal components composition: 73.95% Ni and 16.05% Cr) and a ceramic tube (99.8% Al2O3). The use of air as the carrier was made by employing a Rheodyne valve to inject the samples, allowing an analytical frequency of 90 h(-1) and avoiding sample dispersion. The carrier flow rate (air), sample volume injected, and acid concentration (HCl) were evaluated for the optimization of the TS-FF-AAS system. The sensitivity for 50 mL of analytical solution with TS-FF-AAS was 2 and 5 times higher (to metallic and ceramic tube, respectively) than using an acetylene-nitrous oxide flame with pneumatic aspiration (requiring a sample volume of approximately 20 times higher.