Silica Gels
Mostrando 1-12 de 23 artigos, teses e dissertações.
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1. NIR Luminescence from Sol-Gel Er3+ Doped SiO2:GeO2 Transparent Gels, Nanostructured Powders and Thin Films for Photonic Applications
Samples of (1 – x)SiO2:xGeO2 compositions, containing x = 10 and 20, and doped with Er3+, were prepared by a simple sol-gel route. Homogeneous and transparent gels were synthesized and xerogels were obtained by gel annealing from 700 ºC to 1100 ºC. Films exhibiting high transmittance in the visible and near infrared were deposited by spin-coating techniq
J. Braz. Chem. Soc.. Publicado em: 2015-12
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2. Oxido misto de SiO2/SnO2,SiO2/SnO2/Fosfato : propriedades e aplicações / The SiO2/SnO2, SiO2/SnO2/fosfato mixed oxide : properties and applications
The present work describes the preparation of SiO2/SnO2 mixed oxide obtained by the sol-gel processing method with Sn compositions (in wt %) of 4, 13 and 18%. The high specific surface and the presence of Lewis and Brfnsted acid sites, constitutes an interesting substrate for preparing new classes of chemically modified electrodes. In a specific application,
Publicado em: 2005
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3. Evaluation of the Influence of Microwaves in the Structure of Silica Gels
In this work we studied the influence of microwaves in the pore structure of silica gels obtained via sol-gel polymerization process. We analised the feasibility of replacing conventional heating by microwave heating during drying. Structural parameters such as specific volume of pores (Vp), specific surface area (Sp), average pore size (r p) and the bulk an
Materials Research. Publicado em: 2002-10
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4. Synthesis of Titania-Silica Materials by Sol-Gel
In this work TiO2-SiO2 glasses containing as much as 20 mol % of TiO2 were prepared via sol-gel process using titanium and silicon alkoxides, in the presence of chlorine, in the form of titanium tetrachloride or HCl. The gels were heat-treated until 800 °C. X-ray diffraction and Fourier transform infrared spectroscopy were used to understand the structural
Materials Research. Publicado em: 2002-10
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5. Preparation of silica by sol-gel method using formamide
In this work we obtained microporous and mesoporous silica gels by sol-gel processing. Tetraethylortosilicate (TEOS) was used as precursor. Nitric acid and hydrofluoric acid were used as catalysts. In order to study the affect of formamide as drying additive, we used a molar ratio alkoxide/formamide of 1/1. The performance of formamide in obtaining crack-fre
Materials Research. Publicado em: 2001-07
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6. Structural evolution of silica sols modified with formamide
In this work we investigated the influence of formamide on the acid-catalyzed sol-gel process by Fourier transform infrared spectroscopy (FTIR). Three silica sols were studied: Sol catalyzed with nitric acid without formamide, sol catalyzed with nitric acid containing formamide and sol catalyzed with a mixture of nitric acid and hydrofluoric acid and modifie
Materials Research. Publicado em: 2001-07
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7. Caracterização de geis tixotropicos utilizados em telecomunicações
This work is enclosed in a project of development of national technology in Telecommunications with participation of UNICAMP and TELEBRÁS Research and Development Center. Today, a number of the materials used in optical cables are imported, without a specific knowledge of their behavior in the Brazilian climate conditions. The gels used for cable filling ar
Publicado em: 1992
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8. Obtenção e caracterização de (hidr)oxidos de ferro
Magnetite was produced by heating iron (III) hydroxoacetate (lHA) under nitrogen. By varying the conditions of lHA preparations (acetate concentration in solids, starting reagents and association with other metaIs) and its heating temperature, materiaIs of different properties were prepared. Iron (III) hydroxoacetate gels were obtained through hydrogenolysis
Publicado em: 1991
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9. Sois, geis e vidros de sílica obtidos pelo processo sol-gel / Sílica Sols, gels and glasses made by sol-gel process
Estudos sistemáticos utilizando a técnica de SAXS foram realizados no síncrotom do LURE (Orsay) com feixe intenso de geometria pontua:, para descrever a cinética e as estruturas obtidas durante as etapas de transformação sol ->gel úmido ->gel seco ->vidros de sílica . As análises foram feitas em termos de uma lei de potência I = q-? cujo expoente e
Publicado em: 1987
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10. Simplified Method for the Preparation of Silica Gels
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11. PREPARATION OF CLEAR SILICA GELS THAT CAN BE STREAKED
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12. The Use of Silica Gels for the Cultivation of Halophilic Organisms