Página 1 dos resultados de 9459 itens digitais encontrados em 0.012 segundos
Resultados filtrados por Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG)

Nanoesferas magnéticas: estudo do sistema maghemita/sílica; Magnetic nanospheres: study of the maghemita, silica, stober

Caiado, Kely Lopes
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG)
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
37.018538%
In this work, we synthesized core/shell magnetic composite type consisting of maghemite nanoparticles covered with a coating layer of amino-functionalized silica. The experimental procedure was based on four steps: i) synthesis of magnetite nanoparticles and subsequent oxidation to maghemite, ii) preparation of aqueous colloidal dispersions (ferrofluids), from maghemite nanoparticles with modal diameter of 8.4 nm or 7.2 nm functionalized with citrate ion, iii) preparation of silica magnetic nanospheres (NMS) by the modified Stöber method using different amounts of ferrofluids and tetraethoxysilane (TEOS), and iv) functionalization of silica nanospheres with amino groups using aminopropyltrimethoxysilane (APTS). Sample characteristics of NMS were determined from the iron content measurements, from high-resolution transmission electron microscopy (HRTEM) and from vibrating sample magnetometry (VSM) and they were evaluated on the basis of the synthetic parameters employed, these being the content of magnetic material (nFe/nTEOS = 0.05, nFe/nTEOS = 0.01 e nFe/nTEOS = 0.002) and the type of used ferrofluid; a freshly prepared ferrofluid or an aged ferrofluid. The study of ferrofluids by static magnetic birefringence (SMB) showed that both had aggregates of magnetic nanoparticles...