Formation of colloidal silica particles from alkoxides

Bailey, Joseph K.; Mecartney, Martha L.

doi:10.1016/0166-6622(92)80081-c

Cited by 136 publications

(125 citation statements)

References 10 publications

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“…Harris (3) assumed that the nucleation rate was proportional to the experimentally mea-(as in acid), the batch Stöber process analyzed by a wide variety of techniques ( 29 Si-NMR, conductivity, Raman spec-sured rate of TEOS consumption, and he avoided the use of solvation repulsion in the aggregation kernel. Although the troscopy, pH monitoring, gas chromatography, 1 H-NMR, 13 C-NMR, and molybdate analysis), shows the unhydrolyzed treatments of Bogush and Zukoski (2) and of Harris (3) differ somewhat on these points, both treatments success-TEOS as the predominant species in solution (1,3,(8)(9)(10)(11)(12). Only the singly hydrolyzed monomer (Si (OEt) 3 (OH)) is fully predicted the average size and size distribution over the limited composition range of Stöber synthesis.…”

Section: Introductionmentioning

confidence: 94%

Assessing Extreme Models of the Stöber Synthesis Using Transients under a Range of Initial Composition

Lee

Look

Harris

et al. 1997

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 94%

Assessing Extreme Models of the Stöber Synthesis Using Transients under a Range of Initial Composition

Lee

Look

Harris

et al. 1997

Journal of Colloid and Interface Science

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“…For this purpose various techniques, such as nuclear magnetic resonance 17 , conductimetry 18 , Raman scattering 19 , dynamic light scattering 20 , transmission electron microscopy 21 and smallangle X-ray scattering 22 were applied to investigate both the chemistry and the physical properties of the particles, but more noticeably the dynamics of growth 23 . Despite these intensive investigations, a clear and complete picture for the formation of uniform silica particles has not yet emerged.…”

Section: Introductionmentioning

confidence: 99%

Core-and-shell nature of Stöber silica particles

Leite

Souza

Galembeck

2001

J. Braz. Chem. Soc.

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Duas amostras diferentes de partículas monodispersas de sílica de Stöber foram examinadas por microscopia eletrônica de transmissão analítica, utilizando-se diferentes tipos de imagens: campo-claro, campo escuro, imagens espectrais e mapas de distribuição elementar. As partículas (141 e 36 nm de diâmetro efetivo) contêm domínios de relação elementar O/Si e, portanto, de grau de hidratação muito variável, que coexistem com partículas medindo poucos nanômetros de diâmetro e com relação O/Si elevada, que aparecem dispersas no fundo das imagens. As imagens de campo claro e de perda de energia revelam que as partículas maiores possuem uma morfologia do tipo caroço-casca e as cascas das partículas possuem uma quantidade maior de domínios com razão O/Si maior, comparada com o interior da partícula, o que é atribuído ao acúmulo de domínios mais hidratados na casca, e também à presença de compostos de carbono, contaminantes da sílica. Por outro lado, as partículas menores (diâmetro efetivo = 36 nm) não são esféricas nem têm morfologia caroço-casca, embora também sejam formadas por domínios de composições químicas muito diferentes. Os vários mecanismos de formação de partículas apresentados na literatura são discutidos, considerando-se estes novos resultados.Two different samples of monodisperse Stöber silica particles were examined in the analytical transmission electron microscope, using different imaging modes: bright-field, dark-field, energyloss and elemental distribution maps. The particles (effective diameters = 141 and 36 nm) are formed by domains of variable O/Si ratio, which is consistent with a variable degree of hydration, and they coexist with particles with a high O/Si ratio measuring a few nanometers only, which appear dispersed in the picture background. Bright-field and energy-loss images of the larger particles show a core-and-shell morphology, and the shells have a higher amount of high-O/Si domains as well as contaminating carbon compounds. On the other hand, the smaller particles (effective diameter = 36 nm) are also formed by distinct domains, but their morphology is neither spherical or core-and-shell. The mechanisms for particle formation presented in the literature are discussed, considering the present findings.Keywords: colloidal silica, transmission electron microscopy, energy-filtered imaging, silica particle microchemistry J. Braz. Chem. Soc., Vol. 12, No. 4, 519-525, 2001. Printed in Brazil ©2001 Soc. Bras. Química 0103 -5053 $6.00+0.00 IntroductionUniform fine particles are interesting as model systems in the study of adsorption and catalysis, as well as in the study of size-dependent solid state properties such as quantum confinement 1 and superplasticity 2,3 . There have been significant achievements concerning the preparation of uniform colloid dispersions, both inorganic 4 and organic 5 . However, uniformity has often been considered only in relationship to particle size and shape, and little information is currently available concerning the uniformity of chemical composition of particl...

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“…The nuclei grow up to primary particles with a size of about 20 to 40 nm [3]. During the precipitation process, new nuclei are permanently formed [4] due to the continuous supply of reactants. With the growing number of particles, the critical coagulation concentration is exceeded and, thus, an aggregation process is initialized.…”

Section: Materials and Analytical Methodsmentioning

confidence: 99%

Effect of Important Precipitation Process Parameters on the Redispersion Process and the Micromechanical Properties of Precipitated Silica

et al. 2009

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In the past, the importance of the industrial mass production of high-quality products and specialty chemicals by precipitation increased rapidly. In the industry, usually larger aggregates are produced and in order to produce colloidal systems with the desired properties, a more or less intense dispersion of the precipitated particles is necessary. The micromechanical properties such as the maximum indentation force, the plastic and elastic deformation energy, and the strength can give information on the product and the efficiency of the dispersion process. Generally, the temperature, as one of the most important parameters of the semibatch precipitation process of silica, was varied in order to change the structure, the primary particle size, the aggregate size, and the primary particle interactions in the aggregates. Dispersion of the precipitated silica in a stirred media mill and a dissolver show that the higher the precipitation temperature, the higher is the product fineness and, thus, the smaller is the strength of the aggregates. The reason for this effect is the increase of the primary particle size and the decrease of the solid bonds with increasing precipitation temperature. Because of higher stress intensities, the product fineness in a stirred media mill is considerably higher than in the dissolver. In principal, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with decreasing particle strength and maximum indentation force. Besides the maximum indentation force, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with increasing quotient of plastic and elastic deformation energy.

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Formation of colloidal silica particles from alkoxides

Cited by 136 publications

References 10 publications

Assessing Extreme Models of the Stöber Synthesis Using Transients under a Range of Initial Composition

Assessing Extreme Models of the Stöber Synthesis Using Transients under a Range of Initial Composition

Core-and-shell nature of Stöber silica particles

Effect of Important Precipitation Process Parameters on the Redispersion Process and the Micromechanical Properties of Precipitated Silica

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