Preparation Of Silica Particles Research Articles

Monodispersed, Micron-Sized Supermicroporous Silica Particles by Cetyltrimethylammonium Bromide-Mediated Preparation.

In this study, we present a novel modified Stöber method utilizing cetyltrimethylammonium bromide (CTAB) as a mediator for the preparation of monodispersed, micron-sized supermicroporous silica particles. Observed results show prepared silica particles ranging in size from 0.64 to 1.36 μm with an increase in CTAB concentration from 1.0 to 5.0 mM. The particles exhibited low polydispersity (<5%), a high Brunauer-Emmett-Teller surface area (570 to 1064 m2/g), and pore volumes ranging from 0.22 to 0.39 cm3/g. The pore size, determined using the Barrett-Joyner-Halenda method from the adsorption branches of the isotherms, was approximately 1.9 nm, specifically 1.83, 1.85, and 1.90 nm, as the CTAB concentration increased from 1.0 to 2.5 and 5.0 mM, respectively. The resulting particles displayed a narrow distribution of pore diameters. In addition, to obtain an in-depth understanding of the role of CTAB on the preparation of silica particles, a possible mechanism is also investigated using conductivity, dynamic light scattering (DLS), zeta potential, FT-IR spectra, and transmission electron microscopy. Our findings demonstrate that CTAB plays multiple roles in the hydrolysis/condensation of TEOS (tetraethyl orthosilicate) and subsequent nucleation and growth of silica particles. CTAB acts as a template for superporosity, a stabilizer for colloids, and an accelerator for nucleation and growth, leading to formation of monodispersed micrometer silica particles. Further characterization through FT-IR and 29Si solid NMR spectra revealed that the micron silica particles were obtained with inhomogeneity in the condensation degree, allowing for selective etching through hot incubation to form micron-sized hollow silica spheres.

Morphology-controlled silicon oxide particles produced by red wiggler worms

The preparation of silica particles by vermicomposting has gained increasing attention for use as an inventive alternative to conventional methods. The silica oxides obtained can be used in a number of technological applications. As of yet, these particles cannot be used efficiently because of the lack of research into the relationship between the bioprocess and the shape and size of the particles. The aim of this study is to synthesize silica particles by red wiggler worms using three different grasses: Equisetum hyemale, Zea mays nixtamalized, and Otatea ramirezii and to characterize the obtained particles. However, it is unclear whether the use of diverse systems causes changes in the morphology of the final product. We found that silica particles can be produced by the three studied systems. Furthermore, each system showed a different polymorphism. We demonstrated that the new materials are mesoporous with a low surface area (9–22m2g−1), but each have one specific crystal arrangement. The silicas were characterized by several techniques, namely Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic-force microscopy (AFM), scanning electron microscopy (SEM), dynamic light scattering (DLS), and Brunauer–Emmett–Teller (BET) analysis.

Influence of catalyst and solvent on the preparation of silica particles with mesoporous shell

Silica spheres with sub-micrometer sized mesoporous shell structure were prepared. Effect of different catalyst and solvent on the synthesis of silica particles with mesoporous shell is studied. Depending on its constituents the particle properties are changed. The synthesized materials were characterized by different physicochemical methods such as X-ray diffraction, scanning electron micrograph, transmission electron micrograph, thermogravimetry/differential thermal analysis, nitrogen adsorption and Fourier transform infrared spectroscopy. The analysis reveals that the synthesized materials are having mesoporous shell structure. The mesoporosity increases with catalyst size maybe due to incorporation of more octadecyltrimethoxy silane in shell followed by the elimination of organics on calcinations.

Preparation of Silica Particles in Emulsion Systems

Highly dispersed silicas were obtained in the process of precipitation from sodium metasilicate solution, using hydrochloric acid in the emulsion medium. Optimum emulsion composition and optimum parameters of silica precipitation were defined. Physicochemical and structural properties of the obtained products were evaluated. Studies were also performed on morphology, dispersion and surface character of highly dispersed substances. The particles obtained manifested strictly defined hydrophilic/hydrophobic properties. They should find broad application in several branches of industry.

Preparation of silica particles by sol-gel process in reverse suspension

Sol-gel process of silicon alkoxide was performed in reverse suspension to limit the sites of hydrolysis and dehydration-condensation of alkoxide to the inside of the dispersed droplets and to prepare silica particles of tens μm in diameter. Acetic acid aqueous solution was used as a dispersed phase, and hexane as a continuous phase. The dispersed phase was poured into the continuous phase, in which silicon alkoxide has dissolved, with stirring to form a reverse suspension. Silica particles of 67 μm in mean diameter were obtained by calcining the gel particles produced. Effects of pH of the dispersed phase and concentration of dispersion stabiliser on the characteristics of the silica particles were discussed. The formation mechanism of the gel particle was inferred with applying Jander's model, which is often used to analyse solid phase reaction of particles.

Mechanisms of Silica and Titania Colloidal Particle Formation from Metal Alkoxides

ABSTRACTControl of the preparation of monodisperse particles for green body formation can be achieved by understanding the growth mechanism. Growth processes for colloidal silica and titania were followed by cryo-TEM, which allows direct observation of the particles in the liquid state. Structural development was tracked by quenching samples at successive reaction times. The preparation of silica particles involved the formation of ramified species which subsequently collapsed after reaching a certain size. In the titania system, initially small dense nuclei are observed which eventually form uniformly textured homogeneous particles.