نتایج جستجو برای: silica heterogeneous nanocomposite
تعداد نتایج: 175123 فیلتر نتایج به سال:
knoevenagel condensation between barbituric acid and aldehyde was investigated in the presence of sulfonic acid functionalized nanoporous silica (sba-pr-so3h) and resulted in the formation of arylidene and bis-arylidene barbiturates. excellent yields and short reaction times are related to the high efficiency of sba-pr-so3h that the reactions take place easily in its nano-pores. sba-pr-so3h as ...
One way to thermal stability and ablation improving of polyurethane elastomers with approach of solid propellant rocket insulation, is use of fillers such as silica particles with property of high ablation. In this study, it was paid to prepare polyurethane-silica composites (16,25 and 38% by weight) and polyurethane-silica nanocomposites (10, 16 and 25% by weight) and then interaction, morphol...
Polymer aerogels are a promising, non-brittle alternative to silica aerogel, but limited by their very poor high-temperature stability. Polyimide is widely known for its high heat-resistance, however, degree of volume shrinkage common polyimide after exposure temperatures above 200 °C. Here, we present the aerogel-in-aerogel composites that comprise aerogel grains with nanoparticulate microstru...
a new one-pot, efficient three-component condensation of dimedone, urazole and aromatic aldehydes in the presence of silica supported sodium hydrogen sulfate as an effective heterogeneous catalyst for the synthesis of novel triazolo[1,2-a]indazole-1,3,8-trione derivatives under solvent-free conditions is described.
A series of Fe3O4 supported on mesoporous FDU-12 silica systems were prepared by the hydrothermal conditions. The surface properties of the functionalized catalyst were analyzed by a series of characterization techniques like FTIR, XRD, N2 adsorption–desorption and TEM. XRD and adsorption–desorption analysis shows that the mesostructure of FDU silica remains intact after Fe3O4 modifications, wh...
The protons on a silica or alu mina su rface can be replaced by manganese( III) porphyrin ca tions, Mn(TPP +). Manganesc(III) porphyrin supported on silica and alumina can activate dioxygen in the presence of additional NaBH4 o r [NBu41rBH41 as an electron source and styrene, affording I-phenyl ethanol and acetophenone in a 4:1 ratio. When oxidation was applied in a mixture of benzene/eth...
silica-bonded n-propyldiethylenetriamine sulfamic acid (sbpdsa) was found as an efficient solid acid for the synthesis of coumarins. coumarin derivatives were obtained via the pechmann condensation reaction of phenols and β-keto-esters at 80 oc under solvent-free conditions. also, biscoumarins were obtained via the condensation of aldehydes and 4-hydroxycoumarin in water at reflux conditions. t...
A self-assembly process for the preparation of functional mesoscopically ordered semiconducting polymer–silica nanocomposite thin films is reported. The nanocomposites are prepared by introducing pre-synthesized semiconducting polymers into a tetrahydrofuran (THF)–water homogeneous sol solution containing silica precursor species and a surface-active agent. Depending on the concentration of the...
In this study, silica nanoparticles were used as support to prepare a new heterogeneous catalyst system for application in organic reactions. The reaction of silica nanoparticles with sodium 2-bromoethane-1-sulfonate resulted in the connection of a sulfonic acid group on the surface of silica nanoparticles (NSESA). The synthetic catalyst system was characterized using different microscopic and ...
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