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921.
Four different silica-based urea-formaldehyde (UF/SiO2) composite materials were prepared by various sol-gel synthetic procedures to yield an interpenetrating (IPN-UF/SiO2), a micro-size UF resin encapsulated inside silica shell (Encap-UF/SiO2), a micro-size silica encapsulated inside UF shell (Encap-SiO2/UF), and a blend mixture (Blend-UF/SiO2) hybrid systems. The thermal properties of the obtained organic-inorganic hybrid composite materials were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The structure and morphology of the obtained systems were investigated by infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Their surface porosity and acidity were evaluated from the nitrogen adsorption isotherm and the pH of the corresponding 10% aqueous suspension, respectively. All the results provided evidence for the formation of different hybrid systems with different surface, structural and morphological characteristics. 相似文献
922.
Oxidative deprotection of a variety of trimethylsilyl ethers were performed by Fe(NO3)3.9H2O in the presence of H3PMo12O40.xH2O as catalyst at room temperature in good to high yields under solvent‐free conditions. 相似文献
923.
924.
Tungstophosphoric acid catalyzed rapid and good yielding reactions of α,β-unsaturated aldehydes with arenethiols to give the corresponding 4-thioaryl-1,2,3,4-tetrahydro-1-benzothiopyrans (thiochromans) under solvent-free and room temperature conditions. 相似文献
925.
The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped with 1,2-diacylhydrazines to yield highly functionalized pyrazoles in good yields. 相似文献
926.
In this paper the analytical equation of state (EoS) proposed by Ihm‐Song‐Mason was applied to calculate molar volume of mixtures of carbon dioxide with nitrogen and methane. The pair interaction potential has been used to evaluate the second virial coefficients and the ISM EoS parameters (i.e. α and b). The calculated values of the aforesaid quantities were applied to predict the molar volumes for mixtures of carbon dioxide with nitrogen and methane. Agreement with experiment was excellent for both mixtures. 相似文献
927.
We prove that smooth maps are dense in the sense of biting convergence in W
1, 1(M, N) when M and Nare compact Riemannian manifolds and N is closed. 相似文献
928.
JPC – Journal of Planar Chromatography – Modern TLC - Thin-layer chromatography of ten metal ions has been performed on pure soil layers; the mobile phases were aqueous organic and... 相似文献
929.
The purpose of this paper is to develop a fast and sensitive spectrophotometric method for the simultaneous determination of zinc(II), manganese(II) and iron(II) in pharmaceutical preparations. The method presented in this work is based on the well-known reaction of these ions with 4-(pyridylazo)resorcinol (PAR)1. The application of quantitative chemometric methods, particularly PLS to multivariate chemical data is becoming more widespread owing to the availability of digitized spectroscop… 相似文献
930.