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1.
Kedong Xia Shuoshuo Yu Yunling Li Huijuan Han Lingyao Duan Zhenyu Hou Xiao Liu 《Journal of the European Ceramic Society》2021,41(4):2375-2385
In this study, C/SiOC and C/SiO2 composites were prepared by using carbonaceous microspheres with different surface functional groups. Carbonaceous microspheres based on hydrothermal reaction of glucose contains hydroxyl group, while the surface carboxyl group increases after NaOH etching. The hydroxyl group increases the oxygen-enriched structural units of SiOC ceramics, and the C spheres are closely enwrapped in SiOC matrix after pyrolysis at 900 °C. However, the interfacial reaction of surface carboxyl with Si–OH results in the formation of cristobalite SiO2, and C spheres are not only encased inside the SiOC matrix, but also dispersed outside of SiOC ceramics. After removal of C via calcination at 500 °C for 5 h, C/SiOC and C/SiO2 composites are transformed into amorphous SiO2 and cristobalite SiO2, respectively. The thermogravimetric analysis indicates the oxidation resistance of SiOC is superior to that of C and SiO2. 相似文献
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In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
4.
Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material. 相似文献
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HDPE/PS/HDPE-g-PS合金的相容性和力学性能研究 总被引:1,自引:0,他引:1
用自制接枝共聚物GR-Ⅰ、GR-Ⅱ相容剂研究其对HDPE/PS共混物相容性和力学性能的影响。通过SEM、DMA、DSC和力学性能测试表征,表明在HDPE/PS共混中加入这些相容剂其相容性和力学性能有一定提高 相似文献
8.
A new and efficient method for preparation of optically active poly(styrene–divinylbenzene) copolymers (PS-DVB) is presented here. This is carried out by Friedel–Crafts acylation reaction of chiral N-phthaloyl
-leucine acid chloride with PS-DVB beads in the presence of aluminum chloride as Lewis acid catalyst and 1,2-dichloroethane as the solvent at ambient temperature. Reagents’ amounts and reaction conditions are mentioned and four samples with different amounts of functionality have been prepared. Final products were characterized by FT-IR and elemental analysis. The results obtained confirm that the above modification in preparation of chiral supported PS-DVB has been achieved well and in moderate yield. 相似文献
9.
A new class of bifunctional periodic mesoporous organosilicas (PMOs) composed of organosilicate building blocks with two different silicon sites have been synthesized from the single‐source bifunctional organosilica precursors tris(triethoxysilylethyl)ethoxysilane and bis(triethoxysilylethyl)diethoxysilane, respectively denoted MT3‐PMO and DT2‐PMO. The synthesis of these PMOs is achieved by the co‐assembly of a triblock‐copolymer Pluronic P123 template with the bifunctional organosilica precursor under acid‐catalyzed and inorganic‐salt‐assisted conditions. After template removal through solvent extraction, the MT3‐PMO and DT2‐PMO so obtained show well‐ordered mesopores and display large pore diameters (6–7 nm) and pore volumes (0.6–0.8 cm3 g–1) with a narrow pore‐size distribution and high surface areas (700–800 m3 g–1). 相似文献
10.
The bulk copolymerization of styrene–acrylonitrile monomers using styrene‐N+–montmorillonite complex as a comonomer in the polymerization was studied. The X‐ray diffraction (XRD) analysis showed that part of the styrene‐N+–montmorillonite complex remained non‐dispersed (immiscible) and the copolymer was excluded from the interlayer of the immiscible part of the clay. The successive chemical extraction process revealed that a reasonable amount of the styrene–acrylonitrile copolymer was directly attached to the styrene‐N+–montmorillonite complex and enveloped the clay. Highly exfoliated clay lamella and nanospheres (3–5 nm) were observed by transmission electron microscopy (TEM). The montmorillonite clay assume two different morphologies, immiscible and exfoliated, on the basis of the XRD and TEM data. A simple method of calculation of the ratio of the exfoliated/immiscible amounts of the clay indicated that the amount of the styrene‐N+–montmorillonite complex exfoliated into separate lamella was 40 % (w/w) of the amount of the clay samples containing 2 % of the (styrene‐N+–montmorillonite complex) clay. This amount of exfoliated clay decreases with the increase of the concentration of the clay. The presence of the styrene‐N+–montmorillonite clay in the copolymerization reaction had a minor effect on both the copolymer composition and the molecular weight. Modification of the clay with the derivatized styrene monomer can achieve a nanocomposite using a percentage no more than 4 % (w/w) of complex in the copolymer. Copyright © 2004 Society of Chemical Industry 相似文献