Fabrication of SiO2-ZrO2 composite fiber mats via electrospinning

(1 − x)SiO₂-(x)ZrO₂ (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite fibers having a tetragonal crystalline ZrO₂ were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and crystallization of ZrO₂ in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did not depend on the sintering temperature.     

Organic–silicate hybrid catalysts based on various defined structures for Knoevenagel condensation

Two types of organic–inorganic hybrid base catalysts are prepared. Organic-functionalized molecular sieves (OFMSs), particularly “amine-immobilized porous silicates”, are designed based on common idea to immobilize catalytic active sites on silicate surface. Silicate–organic composite materials (SOCMs), such as “ordered porous silicate–quaternary ammonium composite materials”, are the precursors of ordered porous silicates obtained during the synthesis. Both the OFMS and the SOCM are used as the catalysts for Knoevenagel condensation. Among the OFMSs, there is clear tendency that the use of molecular sieve with larger pore volume and/or surface area gives the product in higher yield. Aminopropylsilyl (AP)-functionalized mesoporous silicates such as AP-MCM-41 gives the product in high yield under mild conditions. No loss of activity is observed after repeated use for three times. The SOCMs are also active for the same reaction. The precursors of the mesoporous silicates are more active than those of microporous silicates. This material can be repeatedly used without significant loss of activity. High activity is not due to the leached species. The active sites of the SOCM catalysts are considered to be SiO⁻ moieties located on the pore-mouth. Activity of the SOCM increases when the reaction is carried out without solvent, whereas decrease in activity of the OFMS is observed in the solvent-free system.     

柔性成膜剂和附加剪切场对GF/PP结构与性能的影响

利用自制的可控剪切应力场装置,连接在熔融挤出机料筒末端,使复合材料熔体在成型过程中,受到可控的附加剪切应力场作用,试验成膜剂和附加剪切场对玻纤增强PP复合材料界面结构与性能的作用。结果表明:在成型加工过程中,附加剪切场会改变GF/PP复合材料界面结构,其变化程度与玻纤处理工艺有关,柔性成膜剂有稳定复合材料界面结构和提高GF/PP复合材料力学强度的作用;在所用3种成膜剂中,POE效果最佳,PUR其次,K树脂较差。     

Electrodeposition of silver from nitrate solution: Part II. Mechanism of the effect of phosphate ions

The mechanism of compact Ag-film formation by electrolysis from nitrate solution with addition of small amounts of phosphate ions is elucidated. It is shown that the phosphate ions exert their effect by lowering the exchange current density. Consequently, the radii of nucleation exclusion zones also diminishes, thus producing conditions stimulating electrodeposition of continuous thin Ag-film.     

Relationship Between Interfacial Water Layer Adhesion Loss of Silicon/Glass Fiber-Epoxy Systems: A Quantitative Study

Water at the polymer/substrate interface is often the major cause of adhesion loss in coatings, adhesives, and fiber-reinforced polymer composites. This study critically assesses the relationship between the interfacial water layer and the adhesion loss in epoxy/siliceous substrate systems. Both untreated and silane-treated Si substrates and untreated and silane-treated E-glass fibers were used. Thickness of the interfacial water layer was measured on epoxy/Si systems by Fourier transform infrared-multiple total internal reflection (FTIR-MTIR) spectroscopy. Adhesion loss of epoxy/Si systems and epoxy/E-glass fiber composites was measured by peel adhesion and short-beam shear tests, respectively. Little water accumulation at the epoxy/Si substrate interface was observed for silane-treated Si substrates, but about 10 monolayers of water accumulated at the interface between the epoxy and the untreated Si substrate following 100 h of exposure at 24 °C. More than 70% of the initial epoxy/untreated Si system peel strength was lost within 75 h of exposure, compared with 20% loss after 600 h for the silane-treated Si samples. Shear strength loss in composites made with untreated E-glass fiber was nearly twice that of composites fabricated with silane-treated fiber after 6 months of immersion in 60 °C water. Further, the silane-treated composites remained transparent, but the untreated fiber composites became opaque after water exposure. Evidence from FTIR-MTIR spectroscopy, adhesion loss, and visual observation strongly indicated that a water layer at the polymer/substrate interface is mostly responsible for the adhesion loss of epoxy/untreated siliceous substrate systems and epoxy/untreated glass fiber composites and that FTIR-MTIR is a viable technique to reliably and conveniently assess the adhesion loss attributable to water sorption at the interface.     

Impact of “Super Acid” like filler on the properties of a PEGDME/LiClO4 system

Composite polymer electrolyte based on a new class of filler added to a PEGDME/LiClO₄ model system has been investigated. “Ceramic super acids” used consist of grafted SO₄²⁻ groups on Al₂O₃ particles surface obtained by calcinations route. Conductivity, DSC and FT-IR measurements performed on such composite electrolytes, when compared to the model PEGDME/LiClO₄ electrolyte, showed only slight improvement of their inner characteristics. In contrary, Li/Li symmetric cells study, by means of impedance spectroscopy, has presented a spectacular decrease of the interfacial resistance compare to the model electrolyte. This result opens a new pathway of investigation to master the lithium metal/polymer electrolyte interface.     

Hydrogen evolution in alkaline solution on electrolytic nickel-cobalt and nickel-iron deposited with different bath compositions and current densities

Nickel-cobalt and nickel-iron electrodeposits were characterized as hydrogen electrodes in alkaline water electrolysis (6 mol/L KOH, 25°C). The nickel-based codeposits were fabricated with different bath compositions and at different current densities. The hydrogen evolution in water electrolysis on the nickel-based codeposits was apparently enhanced as compared with that on nickel. The improvement of the electrocatalytic behaviour of the hydrogen electrodes is attributed to their composition and an increase of their active surface, which are dependent on the electrodeposition conditions.     

EVA／EPDM／PVC三元聚合物合金软质泡沫体的制备及其在复合衬垫中的应用

采用物理共混以及化学交联模压发泡成型工艺制备聚乙烯－醋酸乙烯酯（ＥＶＡ）／乙丙橡胶（ＥＰＤＭ）／聚氯乙烯（ＰＶＣ）三元聚合物合金软泡沫体，并制成贴布复合衬垫。讨论了该体系的相容性，动态共交联与发泡的适配，以及贴布复合，造型等问题，结果表明，该衬垫可完合替代国外同类先进产品。     

PS／炭黑复合材料导电性能的研究

本文通过炭黑（简称ＣＢ）用量、加工工艺、温度对ＰＳ／ＣＢ复合材料导电性能影响的探讨、复合导电材料亚微观结构的观察，研究了ＰＳ／ＣＢ复合材料的导电性能。结果表明，随着ＣＢ含量的增加，材料的电阻率呈非线性下降，当ＣＢ的质量分数在１０％～４０％的范围内时，电阻率下降明显，在此含量范围以后，体积电阻率变化不大；材料的导电性能与加工工艺有关，溶剂法的导电性能比混炼法好；电阻率随温度的升高均有上升的趋势。由复合材料的亚微观结构表明，随着ＣＢ含量的增加，ＣＢ由分散的单个颗粒逐渐连结在一起，最后与ＰＳ形成了一种相互交错式的结构