Preparation of ceramic membranes from surface modified tin oxide nanoparticles

The preparation of crack-free SnO2 supported membranes requires the development of new strategies of synthesis capable to allow controlled changes of surface chemistry and to improve the processability of supported layers. In this way, the controlled modification of the SnO2 nanoparticle surface by adding capping molecules like Tiron(R) ((OH)(2)C6H2(SO3Na)(2)) during the sol-gel process was studied, aiming to obtain high performance membranes. Colloidal suspensions were prepared by hydrolyzing SnCl4.5H(2)O aqueous solution with NH4OH in presence of Tiron(R). The effect of the amount of Tiro(R) (from I to 20 wt.%) on the structural features of nanoparticles, powder redispersability and particle-solution interface properties was investigated by X-ray powder diffraction (XRPD), extended X-ray absorption fine structure (EXAFS), quasi-elastic light scattering and electrophoretic mobility measurements. XRPD and EXAFS results showed that the addition of Tiron(R) up to 20 wt.% to colloidal suspensions does not affect the crystallite size of SnO2 primary particles, determined around 2-3 nm. This value is comparable to the hydrodynamic size measured after redispersion of powder prepared with amount of Tiro(R) higher than 7.5 wt.%, indicating the absence of condensation reactions between primary particles after the initial precipitation step. As a consequence the powder with amount of Tiron(R) > 7.5 wt.%, can be fully redispersed in aqueous solution at pH greater than or equal to I I until a nanoparticle concentration of 6 vol.%. The electrophoresis measurements showed a decrease of the isoelectric point by increasing the amount of grafted Tiron(R) at the SnO2 nanoparticle surface, resulting in negatively charged particle-solution interface in all the studied pH range (2-11). These features govern the gelation process favoring the preparation of crack-free SnO2 supported membranes. The control exercised by Tiron(R) modifying agent in the aggregation process allows the fine-tuning of the porosity, from 0.124 to 0.065 cm(3) g(-1), and mean pore size, from 6.4 to 1.9 nm, as the amount of grafted molecules increases from 0 to 10 wt.%. In consequence, the membrane cut-off determined by filtration of polyethylene glycol standard solutions can be screened from 1500 to 3500 g mol(-1). (C) 2002 Elsevier B.V. B.V. All rights reserved.

Tin oxide nanoparticle formation using a surface modifying agent

This work presents results concerning the preparation of redispersible tin oxide nanoparticles achieved by using Tiron molecule ((OH)(2)C(6)H(2) (SO(3)Na)(2)) as surface modifying agent. The adsorption isotherm measurements show that an amount of 10 wt.% of Tiron is need to recover the SnO(2) nanoparticles surface with a monolayer. These nanoparticles can be easily redispersed in tetramethyl ammonium hydroxide at pH greater than or equal to11 until a powder concentration of 12 vol.% of tin. Under these conditions, hydrodynamic particle size is about 7 nm and increases until 52 nm at pH 6 due to the aggregation phenomenon. The time evolution of the viscoelastic properties indicates that the suspensions at pH 12.5, containing 12 vol.% tin oxide and 10 wt.% of surface modifier are kinetically stable. After thermal treatment at different temperature the powder characterisation evidences that the presence of Tiron monolayer at the nanoparticles surface increases the thermal stability of the porous texture and prevent the micropore size growth. This set of results contributes to satisfy the demand for more controlled synthesis of nanoparticles with high thermal stability as required for fabrication of ultrafiltration ceramic membranes. (C) 2004 Elsevier Ltd. All rights reserved.

A Educação secundária no interior paulista: estudo histórico sobre o ginásio estadual de Matão (1940-1965)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cadernos íntimos diários publicados: um estudo das práticas da escrita de diários, no âmbito das práticas sociais disseminadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Um estudo das práticas de escrita de mulheres (escritoras ou não)

Pós-graduação em Educação - IBRC

A escritura da voz: uma experiência na prática de leitura/escuta de As aventuras de Pinóquio, de Collodi, no ensino fundamental

Pós-graduação em Educação - IBRC

Matemática no ensino primário: duas paisagens, uma história, muitas interrogações

Pós-graduação em Educação Matemática - IGCE

Da leitura no impresso à leitura na tela: novas veredas para a formação do leitor na escola

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A implantação da reforma do ensino de 1º e 2º graus no estado de São Paulo nas páginas da imprensa (1971-1982)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Escravo, africano, negro e afrodescendente: a representação do negro no contexto pós-abolição e o mercado de materiais didáticos (1997-2012)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A representação do homem político no principado romano: uma leitura das cartas de Plínio, o Jovem (96 a 113 d.C)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A configuração do habitus professoral para o aluno-mestre: a escola normal secundária de São Carlos (1911-1929)

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

Agente mediador da circulação de saberes pedagógicos: o bibliotecário da Escola Normal Paulista

Pós-graduação em Educação - FFC

Saudade (1919-2002): a contribuição de Thales Castanho de Andrade para o campo da leitura escolar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A Revista de Educação (1921-1923), o nacionalismo e a reforma de 1920: a formação de professores em São Paulo

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