Papers by Keyword: Sol-Gel Reaction

Abstract: Macroporous Ca₁₂Al₁₄O₃₃ (C12A7) mayenite monoliths have been successfully prepared via a sol-gel process in the presence of propylene oxide (PO) and poly (ethyleneoxide) (PEO). Gelation of CaO-Al₂O₃ binary system with nitrates salts as additional precursors is accelerated by PO as an acid scavenger, while PEO works as a phase separation inducer to mediate the phase separation of the system. Appropriate PO and PEO amounts allow the formation of monolithic xerogel with interconnected macropores and co-continuous skeletons. The resultant dried gels are amorphous and the single crystalline phase Ca₁₂Al₁₄O₃₃ mayenite forms after heat-treatment at 1100 °C in air, while the macrostructure is preserved with a porosity as high as 78% and smoother and denser skeletons.

Abstract: We first synthesized gadolinium oxide (Gd2O3) by a modified “polyol” strategy and then embedded it into mesoporous silica by a simple self-assembly sol-gel reaction. Scanning electron microscope (SEM) results show that the samples have good sphericity and good dispersibility. The structure of mesoporous silica was characterized by transmission electron microscopy (TEM) and small-angle X-ray diffraction (SAXRD). Results show that the mesoporous structure has not been destroyed after gadolinium oxide imbedding. The ratio of gadolinium and silica was determined by the mean of energy dispersive spectroscopy (EDS).

Abstract: In this study, we attempt to investigate the effect of silica size on the thermal, mechanical and biodegradable properties of polylactide/amino-silica (PLA/SiO2) composite material, by preparing the PLA/ SiO2 hybrids containing different size of silica particle through twin-screw extruder. First of all, we prepared amino-functionalized silica particles through performing the conventional base-catalyzed sol-gel reaction of methyltrimethoxysilane (MTMS) and 3-aminopropyltrimethoxysilane (APTMS). The average diameter of silica particle employed in hybrids was 150 nm (S-silica) and 1μm (B-silica), respectively. Systematically comparative studies on the thermal properties and mechanical strength of hybrids containing two different sizes of SiO2 particles materials were carried out on a basis of studies of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It should be noted that the mechanical strength of hybrids containing smaller size of silica particles was found to reveal significant improvement in storage modulus as compared to its corresponding counterpart based on the DMA investigation. Moreover, the thermal stability of hybrids containing smaller size of silica particles was found to reveal slight improvement in glass transition temperature as compared to its corresponding counterpart based on the DSC investigation. Eventually, the as-prepared hybrids were found to exhibit almost similar degradation behavior to that of neat PLA.

Abstract: Three kinds of colloidal silica (CS)/silane sol solutions were synthesized in variation with parameters such as different acidity and reaction time. Sol solutions were prepared from HSA CS/ methyltrimethoxysilane (MTMS), LS CS/MTMS and LS CS/MTMS/γ -Glycidoxypropyltri methoxysilane (ES) solutions. In order to understand their physical and chemical properties, sol-gel coating films were fabricated on glass. Coating films on glass, obtained from LS/MTMS sol, had high contact angle, also, much enhanced flat surface in the case of LS/MTMS sol was observed in comparison with HSA/ MTMS sol. From all sol-gel solutions, seasoning effect of for enhancing properties of sol-gel coating layer on glass was observed while such sol-gel solutions were left for 7days. In initial stage of sol-gel reaction, all most of sol solutions used in this work seem to be unstable, formation of coating films was a little hazy and rough. However, improved coating films as observed in 4days later. LS/MTMS/ES sol solutions were synthesized with ES, adding to LS/MTMS sol. Contact angle of LS/MTMS/ES sol-gel coating films decreased, since ES played a role in forming hydrophilic hydroxyl sol. The elastic portion of coating films prepared from LS/MTMS/ES sol increased with addition of ES, but thermal stability decreased a little.