Advanced Materials Research Vol. 549

Abstract: A new biodegradable copolymer of cellulose diacetate and poly(p-dioxanone) (PPDO) was prepared through a couple-grafting procedure. PPDO was functionalized with the isocyanate group, and then PPDO terminated with the isocyanate group was enabled to react with the hydroxyl groups of cellulose diacetate. The length of PPDO graft chains can be controlled easily by using the prepolymers of PPDO with different molecular weights. The resulting products were thoroughly characterized with FT-IR, ¹H-NMR. The mechanical properties of the copolymers were affected greatly by the length of PPDO segment.

Abstract: In this paper, parallel flaw precipitation method has been employed to fabricate nanostructured Co₃O₄ with the assistance of different surfactants. It is found that the surface parameters, SEM image and photocatalytic performance of Co₃O₄ have a strong dependence on the type of surfactants. The prepared photocatalysts Co₃O₄ were characterized by BET, XRD and SEM. The results show that Co3O4 prepared with the assistance of sodium dodecylbenzenesulfonate exhibits the best photocatalytic activity among the experimented compositions. The surface parameters and SEM all play an important role in promotion of photocatalytic activity of Co₃O₄ prepared.

Abstract: High quality zinc blende ZnSe nanocrystals were successfully synthesized using an environmentally friendierly phosphine-free method. Using pre-synthesized ZnSe nanocrystals as core to dope Cu²⁺ ions, we obtained ZnSe:Cu/ZnSe and ZnSe:Cu/ZnSe/ZnS core/shell nanocrystals. Absorption spectruscopy, photoluminescence (PL) spectruscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to characterize the structures and properties of as-synthesized three kinds of nanocrystals. The results demonstrated that nanocrystals had well dispersion and narrow size-distributions, and the PL emission peak of as-synthesized ZnSe:Cu/ZnSe/ZnS core/shell nanocrystals could be easily tuned from 480 nm to 520 nm by using different sized ZnSe cores.

Abstract: Aqueous polyurethane (APU) dispersions with improved hydrophilicity were presented and characterized. In order to make APU products more competitive, anionic diols and dimethylopropanic acid (DMPA) were introduced into the macromoleculars of APU. The particle sizes of the APU dispersions have been reduced from 0.7~3μm to 0.05~0.6μm, and the storage stability has been prolonged from 6 months to 12 months. It is efficient to prepare the self-emulsifiable APU dispersions by applying anionic polyester diols and using triethanolamine (TEOA) as a neutralization agent.

Abstract: Alloy 600 was studied from three aspects including corrosion behaviour experiment in high temperature, metallurgy element dissolving experiment and water chemistry optimization analysis. Experimental results showed that there was not obvious corrosion velocity for Alloy 600 in local concentrated NaOH solution; high ratio of iron dissolving concentration was found after high P,T experiment, which indicated that Alloy 600 experienced de-alloy corrosion in localized concentrated environment.

Abstract: Immersion precipitation is one of the commonly used methods in preparing polyvinylidene fluoride membrane (PVDF) membrane. Using this method, the membrane structure is easily controlled and the operation is very simple. This paper summarized the mechanism and preparation methods of PVDF as well as researching the effects of membrane-forming factors such as ingredient of solvents and non-solvents, temperature and additives etc. on the structure and function of PVDF membrane. Applying modification on PVDF membrane can improve its hydrophilicity and anti-fouling properties, of which blending modification is expected to be a hotspot of study in future. Adding catalytic agent into PVDF can generate catalytic membrane, which offers a researching direction for preparing multi-functional PVDF membrane. Finally, brief comments are made on the improvement of membrane pore structure and problem of singleness of blending materials.

Abstract: Liquid-liquid equilibria for the three kinds of the ternary systems acetone + ammonium, sodium or potassium citrate + water have been determined at T= (273.15, 283.15, and 298.15) K. Binodal curves, tie-lines, and integrated phase diagrams for the ternary systems are given. The data of the experimental bimodal curve are described with a four-parameter equation. The result also shows the temperature has little influence on the liquid-liquid equilibrium within the investigated range. The tie-line data calculated according to the bimodal data fitting equation and the lever arm rule were satisfactorily described by using the Othmer-Tobias and Bancroft equations, and the result conform the reliability of the calculation method and corresponding tie-line data.

Abstract: Nano-TiO₂ co-doped with lanthanum and iron photocatalyst powders were prepared with the sol-gel method and supercritical fluid drying(SCFD). The XRD、particle size distribution technique、TEM were used to characterize the hyperfine TiO₂ particles.The TiO₂ co-doped with different mass percentage of La³⁺ and Fe³⁺ were compared with pure TiO₂ when being used as photocatalyst in degradation of methyl orange.The best catalytic activity was observed by TiO2 co-doped with 0.02%La-0.05%Fe(mol).Photocatalytic efficiency of the TiO2 co-doped with 0.02%La and 0.05%Fe is 1.625 times the pure TiO₂.

Abstract: The tradition energy dispersion model can not match the experiment results of the AlGaN/GaN superlattice with strong polarization effect. Thus we propose a new dispersion model from the improved tight binding method. In this model, the couple of wavefunctions from more potential wells are considered. To a AlGaN/GaN superlattice with 1.5nm well length, 1nm barrier length and 25% Al content, the calculation result shows that the improved model are much more precise than the tradition model. This improved dispersion model can be used in the study of the nonlinear transport of AlGaN/GaN superlattice.