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51.
Synthetic process to control the total size and component distribution of multilayer magnetic composite particles 总被引:5,自引:0,他引:5
A new synthetic process to prepare composite particles with multilayers, comprised of usual polymer latices, ultra-fine magnetic particles, and a polystyrene layer was examined under various solution conditions.First, the synthetic conditions of heterocoagulates, consisted of polystyrene latices (2a=180900 nm) and NiO·ZnO·Fe2O3 particles (2a=20 nm), were investigated as a function of medium pH, particle concentration, and particle size ratio, based on the concept of the heterocoagulation theory as applied by Harding et al. Regular heterocoagulates were generated under suitable medium and mixing conditions, and that their total size can be controlled by selecting the size of the original polymer latices used as the core.Second, the best encapsulation condition of the heterocoagulates via emulsion polymerization with polystyrene monomer was surveyed. The encapsulation of the heterocoagulates was greatly promoted by pretreatment with oleate molecules, although there is no tendency for the encapsulation when the surfactant-free bare heterocoagulates are used as the core. 相似文献
52.
The electrochemistry of monoclinic and tetragonal vanadium-doped zirconias (VZrO2), prepared from gel precursors with vanadium loadings ranging from 0.5 to 15 mol%, has been studied using abrasive-conditioned
graphite/polyester composite electrodes immersed in aqueous HCl and HClO4 solutions. Isolated vanadium centers form a solid solution in the zirconia lattice with a solubility limit close to 5 mol%.
Above 5 mol%, finely dispersed V2O5 is formed. Vanadium centers located at the boundary sites of the zirconia lattice display successive one-electron transfer
processes near to +0.25 and +0.10 V vs. SCE, whereas finely dispersed V2O5 yields three successive reduction processes at +0.46, +0.30, and +0.16 V vs. SCE. Electrochemical data indicate the presence
of both V5+ and V4+ centers in the lattice of monoclinic and tetragonal zirconias, the V5+/V4+ ratio decreasing as the vanadium loading increases.
Electronic Publication 相似文献
53.
Manuel Cano Beatriz Palenzuela J. Luis Ávila Rafael Rodríguez‐Amaro 《Electroanalysis》2007,19(9):973-977
A PVC/TTF‐TCNQ composite electrode has been employed as detector in a flow injection system. The proposed method allows the simultaneous detection of ascorbic acid (AA) and uric acid (UA) in mixtures by using a FIA system in a simple manner, without pre‐treatment or modified electrode. This method is based on the amperometric determination of (a) ascorbic acid at 0.15 V and (b) both analytes at 0.35 V, being the response linear in the range 1×10?2–4×10?4 M for both analytes with detection limits (S/N=3) of 1.2×10?4 M and 8.1×10?5 M for AA and UA, respectively. 相似文献
54.
Based on the sol-gel technique using butyl titanate as oxide precursor, the regenerated SF (silk fibroin)/nano-TiO2 composite films were synthesized. Different amounts of butyl titanate to SF were used to verify this effect on the characteristics of the formed materials. Samples were characterized by thermogravimetric analysis, X-ray diffractometry, UV, AFM and FT-IR spectroscopy.The experimental results reveal that, compared to the pure silk fibroin films, the mechanical strength of these regenerated SF/nano-TiO2 composite films were increased and the dissolubility in water of SF/nano-TiO2 composite films in aqueous solution were decreased. The diameter of nano-TiO2 particle films was about 80nm through UV and AFM. The nano-TiO2 particles were well dispersed in the regenerated silk fibroin. It was found that the crystal structures of the composite films were transited from typical Silk Ⅰ to typical Silk Ⅱ by the XRD and FTIR. Furthermore, the crystallinity of the composite films was obviously improved. Through the TGA, it was demonstrated that the heat transition temperature of composite films was also enhanced. 相似文献
55.
56.
Mustafa Yavuz 《高分子科学》2007,(4):347-355
Electrorheological (ER) properties of polyaniline (PAni), pumice and polyaniline/pumice composites (PAPC) were investigated. Polyaniline and PAni/pumice composite were prepared by oxidative polymerization. PAni/pumice particlesbased ER suspensions were prepared in silicone oil (SO), and their ER behavior was investigated as a function of shear rate, electric field strength, concentration and temperature. Sedimentation stabilities of suspensions were determined. It has been found that ER activity of all the suspensions increases with increasing electric field strength, concentration and decreasing shear rate. It has shown that the suspensions have a typical shear thinning non-Newtonian viscoelastic behavior. Yield stress of composite suspensions increased linearly with increasing applied electric field strength and with concentrations of the particles. The effect of high temperature on ER activity of purrfice/silicone oil systems was also investigated. 相似文献
57.
TiO_2/PVDF复合中空纤维膜的制备和表征 总被引:15,自引:0,他引:15
采用相转化法制备了二氧化钛 (TiO2 ) 聚偏氟乙烯 (PVDF)复合中空纤维膜 .应用牛血清白蛋白截留实验、扫描电子显微镜、热重分析、X射线衍射分别对复合膜的分离性能、微观结构、热稳定性和晶相组成进行了分析 .结果表明复合膜的性能与纯PVDF膜的相比有显著的改善 ,其中对牛血清白蛋白的截留率从 3 2 7%提高到 86 6 7% ,单根纤维的断裂应力从 3 35MPa提高到 4 70MPa ,提高了 4 0 3% .氮气吸附实验测定的孔径分布进一步表明复合膜的孔径分布变窄 ,孔径变小 . 相似文献
58.
BAO Ren-lie KONG Zu-ping GU Min YUE Bin WENG Lin-hong HE He-yong 《高等学校化学研究》2006,22(6):679-683
IntroductionSynthesis of natural minerals is helpful for tracingthe geological origin of mineral formation and forverifying the quality of minerals. The investigations onthe conditions for mineral formation, such as pressure,temperature, and starting mate… 相似文献
59.
Gino Bontempelli Nicola Comisso Rosanna Toniolo Gilberto Schiavon 《Electroanalysis》1997,9(6):433-443
Electroanalytical sensors, suitable for the analysis and monitoring of electroactive analytes present in gaseous phase or low-conductive liquid media, and based on electrodes in close contact with perfluorinated ion-exchange polymers are reviewed. The basic operative mechanism of these sensors, in which ion-exchange polymers act as solid polymer electrolytes (SPE's), is thoroughly discussed, while stressing the fundamental reasons why their behavior differs from that of conventional membrane electrodes. The procedures for preparing composite working electrodes by coating one side of ion-exchange membranes with stable porous films of conductive materials are described, along with the most common strategies followed to assemble this type of sensors. Useful examples of measurements in electrolyte-free media of inorganic and organic electroactive species of interest mainly for environmental analysis are given. Future prospects for the development of these sensors are also discussed. 相似文献
60.
Polypyrrole composite cation- and anion-exchange membranes (CEM and AEM), in which polypyrrole (PPY) coated on one surface of the membrane as a thin layer, were prepared by chemical polymerization of pyrrole in the presence of high oxidant concentration (Na2S2O8). Existence of polypyrrole layer on the both types of ion-exchange membranes were confirmed by recording their coating density, SEM images and conductivity. These membranes were extensively characterized by recording their properties such as water uptake, ion-exchange capacity, contact angle, permselectivity and membrane conductivity as a function of polymerization time such as. It was observed that due to coating of PPY for 2 h, membrane permselectivity of CEM for NaCl (0.907) was reduced to 0.873, while it was increased from 0.747 to 0.889 in the case of AEM. Similar behaviors were also obtained for bi-valent electrolytes. Electrodialysis experiments were also conducted with polypyrrole composite ion-exchange membranes using mixed electrolytic systems. Relative dialytic rates for NaCl with respect to other bi-valent electrolyte were varied in between 5 and 8 (depending on bi-valent electrolyte), which suggested the feasible and efficient separation of mono-valent from bi-valent electrolyte. Slower electro-migration of bi-valent electrolyte (CaCl2, MgCl2 and CuCl2) in comparison to NaCl was explained on the basis of synergetic effect of sieving of bulkier bi-valent cations by tight and rigid polypyrrole layer and the difference in electrostatic and hydrophobic–hydrophilic repulsion force between bi-valent cations and mono-valent cation. It was concluded that these composite membranes are suitable for the efficient separation of same type of charged ions by electro-driven separation techniques. 相似文献