Caracterização de superfícies de vidros expostas a vapores de KNO3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades varistoras de sistemas a base de 'SN''OIND.2' dopados con 'ZN''O', 'W''OIND.3', 'NBIND.2''OIND.5', 'ALIND.2''OIND.3', 'CRIND.2''OIND.3', 'MN''OIND.2', 'CO''O', 'CU''O', 'V''CLIND.3'

Pós-graduação em Química - IQ

Sensores eletroquímicos baseados em eletrodos de pasta de carbono modificados pela adição de precursores de silicatos de bário dopados com Európio (III)

Pós-graduação em Química - IBILCE

Caracterização elétrica e microestrutural de cerâmicas varistoras de baixa tensão à base de ('SN IND.1-x''TI IND.x')'O IND.2' e 'SN''O IND.2' dopados com 'CO''O' e 'NB IND.2''O IND.5'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Matrizes semicondutoras GaAs e Sn'X IND. 2' dopado com terras-raras Ce ou Eu: investigação do transporte elétrico

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

Mecanismos de transporte elétrico excitados termicamente em Sn 'O IND. 2' dopado com Ce

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Cerâmica condutora à base de 'SN''O IND.2' obtida pelo método dos precursores poliméricos e sinterização por micro-ondas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigação de contatos elétricos e propriedades de filmes finos de SnO2 dopados com os íons terras raras Eu3+ e Ce3+

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da segregação de dopantes no contorno de grão e sua influência nas propriedades elétricas de cerâmicas à base de 'SN''O IND.2'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos fotocrômico e termocrômico em ormosils dopados com azobenzenos

The sol-gel process and the wide variety of alkoxides commercially available have facilitated the processing of various Organic-Inorganic Hybrid Materials. In general, the hybrids are excellents matrix to incorporate organic or inorganic dopants that presents photochromic, thermochromic, and halochromic effects and in some cases photorefractive effects. The GPTS-TEOS hybrid matrix when deposited in the form of film is very resistant, adherent, has excellent transparency in visible region and allows to be doped with various azo-dye and metal salts of unusual oxidation states. One of the main characteristics of the azo-dyes when immersed in some hybrid matrix , is the capacity to isomerizes through group Azo (-N = N-) would can be commutated between the Cis (Z) and Trans (E) configurations by means of light or heat. Our goal was through the sol-gel process to prepare hybrid films of GPTS-TEOS doped with azo-dyes Methyl Red and Disperse Red 1, and characterize them optically. The characterizations are performed using techniques of UV / Vis spectroscopy, to identify changes in the absorption band of azo-dyes in the presence of optical pumping, (photochromic effects), in function of temperature (thermochromic effect). These properties are of wide scientific and technological interest because they will contribute to the confection Smart Windows (windows sensible to light), temperature sensors monitored optically and also in the recording of amplitude and phase diffraction gratings

Preparação e caracterização óptica de filmes híbridos dopados com o azocorante Disperse Red 1

The Sol-gel process has facilitated the processing of Organic-Inorganic Hybrid Materials with several scientific applications and technologies. The hybrid combine the advantages of the Sol-gel process with specific characteristics of organic polymers, allowing processing of thin films without fractures or fissures. The incorporation of azo dyes in polymer matrices has been widely used in the investigation of optical properties. The azo dye Disperse Red (DR1) presents optical alterations when exposed to visible or ultraviolet light. The alterations occur due to transitions of their isomers, trans and cis, caused by photoisomerization, due to electronic transitions of azo group (-N=N-), presenting photochromic and/or photorefractive effects. The hybrid system used in this work is the precursor 3- Glycidoxypropyl-Trimethoxi-silane (GPTS), the Tetraethylorthosilicate (TEOS) and DR1 as a dopant. The characterizations were performed using absorption spectroscopy UV-Vis which allowed the identification of the absorption bands and its variations when the samples were treated thermally and/or illuminated by ultraviolet light

Preparação e caracterização óptica de filmes de ORMOSIL obtidos via processo sol-gel dopados com azocorantes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Técnica de bombeio e prova para medidas de absorção de estado excitado e de emissão estimulada, em materiais sólidos dopados com íons terras raras

Rare earth ion doped solid state materials are the most important active media of near-infrared and visible lasers and other photonic devices. In these ions, the occurrence of Excited State Absorptions (ESA), from long lived electronic levels, is commonplace. Since ESA can deeply affect the efficiencies of the rare earth emissions, evaluation of these transitions cross sections is of greatest importance in predicting the potential applications of a given material. In this paper a detailed description of the pump-probe technique for ESA measurements is presented, with a review of several examples of applications in Nd3+, Tm3+ and Er3+ doped materials.

Ethanol electrooxidation on Pt-Sn and Pt-Sn-W bulk alloys

Ethanol oxidation has been studied on Pt-Sn and Pt-Sn-W electrodes prepared in an arc-melting furnace. Different electrochemical techniques like cyclic voltammetry and chronoamperometry were used to evaluate the catalytic activity of these materials. The electro-oxidation process was also investigated by in situ infrared reflectance spectroscopy in order to determine adsorbed intermediates and reaction products. Experimental results indicated that Pt-Sn and Pt-Sn-W alloys are able to oxidize ethanol mainly to acetaldehyde and acetic acid. Adsorbed CO was also detected, demonstrating the viability of splitting the C-C bond in the ethanol molecule during the oxidation process. The adsorbed CO was further oxidized to CO2.This reaction product was clearly detected by SNIFTIRS. Pt-Sn-W catalyst showed a better electrochemical performance than Pt-Sn that, in it turn, is better than Pt-alone.

Possible evidence of asymmetry in SN 2007rt, a type IIn supernova

An optical photometric and spectroscopic analysis of the slowly-evolving type IIn SN 2007rt is presented, covering a duration of 481 days after discovery. Its earliest spectrum, taken approximately 100 days after the explosion epoch, indicates the presence of a dense circumstellar medium, with which the supernova ejecta is interacting. This is supported by the slowly-evolving light curve. A notable feature in the spectrum of SN 2007rt is the presence of a broad He I 5875 line, not usually detected in type IIn supernovae. This may imply that the progenitor star has a high He/H ratio, having shed a significant portion of its hydrogen shell via mass-loss. An intermediate resolution spectrum reveals a narrow H(alpha) P-Cygni profile, the absorption component of which has a width of 128 km s (1). This slow velocity suggests that the progenitor of SN 2007rt recently underwent mass-loss with wind speeds comparable to the lower limits of those detected in luminous blue variables. Asymmetries in the line profiles of H and He at early phases bears some resemblance to double-peaked features observed in a number of Ib/c spectra. These asymmetries may be indicative of an asymmetric or bipolar outflow or alternatively dust formation in the fast expanding ejecta. In addition, the late time spectrum, at over 240 days post-explosion, shows clear evidence for the presence of newly formed dust.