Sep 2008, Volume 2 Issue 3

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  • WANG Jixiao, LIU Rui, ZHANG Xiaoyan, ZHOU Zhibin, WANG Zhi, WANG Shichang
    A facile route to prepare Fe3O4/polypyrrole (PPY) core-shell magnetic nanoparticles was developed. Fe3O4 nanoparticles were first prepared by a chemical co-precipitation method, and then Fe3O4/PPY core-shell magnetic composite nanoparticles were prepared by in-situ polymerization of pyrrole in the presence of Fe3O4 nanoparticles. The obtained nanoparticles were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and laser particle size analyzer. The images indicate that the size of Fe3O4 particles is about 10 nanometers, and the particles are completely covered by PPY. The Fe3O4/PPY core-shell magnetic composite nanoparticles are about 100 nanometers and there are several Fe3O4 particles in one composite nanoparticle. The yield of the composite nanoparticles was about 50%. The sedimentation behavior of Fe3O4/PPY core-shell magnetic nanoparticles in electrolyte and soluble polymer solutions was characterized. The experimental results indicate that the sedimentation of particles can be controlled by adjusting electrolyte concentration, solvable polymers and by applying a foreign field. This result is useful in preparing gradient materials and improving the stability of suspensions.
  • QI Dongming, YANG Lei, WU Minghua, LIN Heming, NITTA Kohhei
    A novel phenolic rigid organic filler (KT) was melt-mixed with an isotactic polypropylene (iPP) to prepare a series of PP/KT composites, with or without maleic anhydride grafted polypropylene (MAPP) as compatilizer. The evolution of filler morphology during melt-mixing and melt-pressure processes was monitored by scanning electron microscope (SEM) and polarized optical microscope (POM). The influences of shear force, pressure time, filler content and MAPP concentration on the final filler dispersion were studied. We found that this rigid organic filler readily melted and dispersed homogenously into the iPP matrix through a fission-fusion process during the melt-mixing process. Thus a balanced dispersion, which was closely related to shear force and MAPP concentration, can be achieved. During the melt-pressure process, parts of the filler particles combined gradually through a coalescence process. However, the incorporation of MAPP can effectively inhibit the tendency to coalesce and refine the filler particles sizes into nanoscale. Thus, a series of PP/KT composites with controllable filler particles size and narrow size distribution can be obtained just by adjusting process conditions and MAPP concentration. In addition, due to the in-situ formation mechanism, the filler phase possessed a typical solid true-spherical shape.
  • ZHANG Liping, ZHU Yi, NI Caihua
    Thermosensitive core-shell particles were synthesized through graft copolymerization of N-isopropylacrylamide with [ 3-(methacryloxy) propyl]trimethoxysilane (MPT) coupled on the surface of ultrafine silica beads. The copolymerization was carried out using polyvinyl alcohol as a surfactant, water and cyclohexanol as mixed solvent, and 2,2′-azobis(isobutyronitrile) as an initiator. The effect of surfactant concentration and the composition of the mixed solvent on the graft rate were investigated. The structure of modified silica was confirmed by infrared spectra. Differential scanning calorimetry (DSC) has revealed the thermosensitivity of the particles. The thermosensitive particles were used as packing materials of high performance liquid chromatography (HPLC) columns for separating naphthalene derivatives. Satisfactory separation was obtained by controlling the temperature of the column. In contrast, the packing material of silica-MPT has no such separation efficiency due to the lack of thermosensitivity. The effect of the composition of the mobile phase on the separating efficiency was also investigated. The temperature-controlled separation was effective only when the water content was higher than 90% (v/v) in the water-methanol mobile phase. The mechanism for the temperature-controlled separation is attributed to a polarity change of poly(N-isopropylacrylamide) which undergoes volume phase transition on the silica surface as the temperature increases.
  • WU Yusong, LI Jiang, PAN Yubai, LIU Wenbin, AN Liqiong, WANG Shiwei, GUO Jingkun
    High-quality neodymium-doped yttrium aluminum garnet (Nd:YAG) transparent ceramic (4.0 mole percent) was fabricated by a solid-state reaction method and vacuum sintering. The microstructure, optical transmittance, spectral properties and laser performance were investigated. The average grain size of the sample is about 10 ?m. The transmittance of a 2.8-mm thick sample reaches 79.5% at the laser wavelength of 1064 nm. The highest absorption peak is centered at 807 nm and the absorption coefficient is 13.9 cm-1. The absorption coefficient at the laser wavelength is 0.2 cm-1. The main emission peak is at 1064 nm and the fluorescence lifetime is 102 ?s. A laser diode (808 nm) whose maximum output is about 1000 mW was used as a pump source and an end-pumped laser experiment was performed. The 1064 nm-CW-laser output was obtained and the threshold is 733 mW. With 998 mW of maximum absorbed pump power, a laser output of 17 mW is obtained with a slope efficiency of 6.1%.
  • ZHU Dongmei, WANG Fei, GAO Cuiling, XU Zheng
    This paper reports an easy and effective way to fabricate polystyrene/poly (N-isopropylacrylamide) (PS/PNIPAM) core-shell particles and PNIPAM hollow spheres. The main point of the method is to take advantage of the hydrophobic interaction between initiator and PS particles. The hydrophobic azodiisobutyronitriles automatically concentrate around the PS particles and initiate polymerization of N-isopropylacrylamide (NIPAM) and the crosslinker methylene bisacrylamide (MBA), which dissolve in the aqueous phase, at the surface of the PS nanoparticles. Then, PNIPAM adheres to the PS particles to form a core-shell structure as a result of their hydrophobic interaction. This interaction is due to the unique property of PNIPAM, namely, its ability to transition from hydrophilic to hydrophobic when the temperature rises to 32°C. Furthermore, the hollow PNIPAM spheres were obtained by etching the PS core with chloroform.
  • SUN Mingliang, WANG Li, XIA Yangjun, DU Bin, LIU Ransheng, CAO Yong
    A series of narrow band-gap conjugated copolymers (PFO-DDQ) derived from 9,9-dioctylfluorene (DOF) and 2,3-dimethyl-5,8-dithien-2-yl-quinoxalines (DDQ) is prepared by the palladium-catalyzed Suzuki coupling reaction with the molar feed ratio of DDQ at around 1%, 5%, 15%, 30% and 50%, respectively. The obtained polymers are readily soluble in common organic solvents. The solutions and the thin solid films of the copolymers absorb light from 300–590 nm with two absorbance peaks at around 380 and 490 nm. The intensity of 490 nm peak increases with the increasing DDQ content in the polymers. Efficient energy transfer due to exciton trapping on narrow-band-gap DDQ sites has been observed. The PL emission consists exclusively of DDQ unit emission at around 591–643 nm depending on the DDQ content in solid film. The EL emission peaks are red-shifted from 580 nm for PFO-DDQ1 to 635 nm for PFO-DDQ50. The highest external quantum efficiency achieved with the device configuration ITO/PEDOT/PVK/PFO-DDQ15/Ba/Al is 1.33% with a luminous efficiency 1.54 cd/A. Bulk heterojunction photovoltaic cells fabricated from composite films of PFO-DDQ30 copolymer and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as electron donor and electron acceptor, respectively in device configuration: ITO/PEDOT:PSS/PFO-DDQ30:PCBM/PFPNBr/Al shows power conversion efficiencies of 1.18% with open-circuit voltage (Voc) of 0.90 V and short-circuit current density (Jsc) of 2.66 mA/cm2 under an AM1.5 solar simulator (100 mW/cm2). The photocurrent response wavelengths of the PVCs based on PFO-DDQ30/PCBM blends covers 300–700 nm. This indicates that these kinds of low band-gap polymers are promising candidates for polymeric solar cells and red light-emitting diodes.
  • WANG Shoulian, HE Jie, ZENG Yu, YAN Bin, WANG Yinghan
    The polymer stabilized liquid crystal (PSLC) film is a relatively novel electro-optical material, which is generally obtained by dissolving a small amount of a bifunctional photoreactive monomer in a low molecular mass liquid crystal. In this paper, the PSLC films were prepared with photoreactive biphenyl methacrylate monomers by photopolymerization induced phase separation. The effects of liquid crystal concentration, curing time, monomer structures and alignment layer on the electro-optical properties of PSLC films were investigated. The results show that the transmittance in the OFF state (TOFF) increased with the liquid crystal concentration, but the driving voltage decreased. TOFF was also influenced by the curing time. Furthermore, when polyimide was used as alignment layer, the films prepared from the bifunctional monomer shows a higher TOFF, while those from the single functional monomer exhibited a deformed electro-optical curve due to the unsteady polymer networks.
  • YU Moxin, LI Zhong, XI Hongxia, XIA Qibin, WANG Shuwen
    In this work, the effect of the textural property of activated carbons on desorption activation energy and adsorption capacity for benzothiophene (BT) was investigated. BET surface areas and the textural parameters of three kinds of the activated carbons, namely SY-6, SY-13 and SY-19, were measured with an ASAP 2010 instrument. The desorption activation energies of BT on the activated carbons were determined by temperature-programmed desorption (TPD). Static adsorption experiments were carried out to determine the isotherms of BT on the activated carbons. The influence of the textural property of the activated carbons on desorption activation energy and the adsorption capacity for BT was discussed. Results showed that the BET surface areas of the activated carbons, SY-6, SY-13 and SY-19 were 1106, 1070 and 689 m2g-1, respectively, and their average pore diameters were 1.96, 2.58 and 2.16 nm, respectively. The TPD results indicated that the desorption activation energy of BT on the activated carbons, SY-6, SY-19 and SY-13 were 58.84, 53.02 and 42.57 KJ/mol, respectively. The isotherms showed that the amount of BT adsorbed on the activated carbons followed the order of SY-6 > SY-19 > SY-13. The smaller the average pore diameter of the activated carbon, the stronger its adsorption for BT and the higher the activation energy required for BT desorption on its surface. The Freundlich adsorption isotherm model can be properly used to formulate the adsorption behavior of BT on the activated carbons.
  • ZHANG Xiujuan, XU Yuanze, YI Xiaosu
    The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature (UCST) or lower critical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window. We found that the phase separation time/temperature relationship follows the simple Arrhenius equation. The cure-induced phase separation activation energy Ea(ps) generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time. We also found that Ea(ps) is insensitive to TP content, TP molecular weight and curing rate, but it changes with the cure reaction kinetics and the chemical environment of the systems. With the established phase separation time-temperature dependence relation, we can easily establish the whole cure time-temperature transformation (TTT) diagram with morphology information which is a useful map for the TP/TS composites processing industry.
  • LI Xinyang, FAN Pengwei, TUO Xinlin, WANG Xiaogong
    Acidized single-wall carbon nanotubes (SWNTs) were fabricated into multilayers with a hyperbranched azobenzene-containing polymeric diazonium salt (PDAS) using the layer-by-layer adsorption technique. The fabrication process, multilayer thickness variation, multilayer surface morphology and the interaction between SWNTs and PDAS were monitored by UV-Vis absorption spectroscopy, optical ellipsometry, Atomic Force Microscopy, Scanning Electron Microscopy and Raman spectroscopy. Moreover, the nanomechanical properties of the multilayer films were measured by nanoindentation. All results show that SWNTs and PDAS can be fabricated into multilayers based on the cooperation of electrostatic absorption and chemical cross-linkage between SWNTs and PDAS. Further, this cooperation endows the SWNT/PDAS multilayer films with outstanding nanomechanical properties. The hardness and modulus are about 2.0GPa and 10.0GPa, respectively. Finally, the SWNT/PDAS multilayer film can be peeled off to be a free-standing film.
  • JIANG Lizhong, WU Dezhen, LUO Ning, WU Zhanpeng, MOU Nanxiang
    Polyimide/silica/silver hybrid films were prepared by the sol-gel method combined with in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the migration and aggregation of silver particles to the surface of hybrid films were investigated. The hybrid films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of the polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing silica content, more and more silver particles were kept in the hybrid films instead of being migrated onto the surface of the hybrid films and the reflections of hybrid films decreased gradually.
  • YANG Zehui, OU Encai, WANG Yunan, PENG Li, WANG Jiaqiang, YIN Lihui
    Transition metal M (M = Mn, Fe, Co, Ni, Cu, and Zn) doped mesoporous titania with a crystalline framework was employed as catalysts for the oxidation of p-bromotoluene (PBT) to p-bromobenzaldehyde (BBD) in acetic acid using aqueous hydrogen peroxide as oxidant. It was found that mesoporous TiO2 doped with those metals (Fe, Co and Ni) whose atomic radii are relatively smaller exhibited higher conversion rate of PBT. Among these catalysts, the Co/meso-TiO2 exhibited high substrate conversion and good product (p-bromobenzaldehyde) selectivity plus it can be reused once with almost the same activity. The effect of different Ti/Co (molar) ratio on the activities of Co/meso-TiO2 was also investigated.
  • BAI Shu, REN Mengyuan, WANG Lele, SUN Yan
    The regioselective acylation of pyridoxine catalyzed by immobilized lipase (Candida Antarctica) in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) has been investigated, and compared with that in acetonitrile (ACN). The acetylation of pyridoxine using acetic anhydride in [BMIM]PF6 gave comparable conversion of pyridoxine to 5-monoacetyl pyridoxine with considerably higher regioselectivity (93%–95%) than that in ACN (70%–73%). Among the tested parameters, water activity (aw) and temperature have profound effects on the reaction performances in either [BMIM]PF6 or ACN. For the reaction in [BMIM]PF6, higher temperature (50°C–55°C) and lower aw (<0.01) are preferable conditions to obtain better conversion and regioselectivity. Mass transfer limitation and intrinsic kinetic from the ionic nature of ionic liquids (ILs) may account for a different rate-temperature profile and a lower velocity at lower temperature in [BMIM]PF6-mediated reaction. Moreover, consecutive batch reactions for enzyme reuse also show that lipase exhibited a much higher thermal stability and better reusability in [BMIM]PF6 than in ACN, which represents another advantage of ILs as an alternative to traditional solvents beyond green technology.
  • QIAN Qinghua, HU Yuyan, WEN Gaofei, FENG Xin, LU Xiao-hua
    A new smooth potassium dititanate film was prepared by sol-gel method and characterized by thermogravimetry (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible diffuse reflectance and Raman spectroscopy. The gaseous photocatalytic activity of smooth K2Ti2O5 films was studied using contact angle analysis from the photocatalytic decomposition of octadecyltrichlorosilane (OTS) based self-assembled monolayers (SAMs) formed on K2Ti2O5 films. The photocurrent response of the film was determined by an electrochemical method. It was shown that the films were smooth, compact, and transparent when formed on glass. Compared with TiO2 film, the K2Ti2O5 film showed wide absorption in the ultraviolet and visible region. It was found that the monolayers on K2Ti2O5 decomposed much faster than those on TiO2 under UV irradiation of 254 nm in air. The film also exhibited a stronger photoresponse and a more stable anodic photocurrent. The K2Ti2O5 film efficiently decomposes the alkylsiloxane monolayers under UV irradiation in air and it was found to be a good photocatalyst for gaseous organic pollutant treatment.
  • ZHOU Jun, CHU Wei, ZHANG Hui, XU Huiyuan, ZHANG Tao
    The effect of Fe content on FeMn/MgO catalysts for light alkenes synthesis through CO hydrogenation was investigated. Catalysts were prepared by a conventional co-impregnation method, characterized using BET, X-ray powder diffraction (XRD) and Temperature-programmed reduction (H2-TPR) techniques. High activity was obtained over the catalyst with 9 wt-% Fe content, over which CO conversion and the selectivity of C2=–C4= reached 91.36% and 58.48%, respectively. With the increase of Fe content, both the conversion and the selectivity were improved within a certain range and then decreased. The results show that the surface area of the catalyst played an important role in the catalytic reaction. With the increase of Fe loading, the interaction action between Fe and Mn was enhanced and FeMn solid solution was formed.
  • ZHANG Dongxiang, XUE Min, XU Hang, XU Wenguo, TARASOV V
    Ultra-fine zinc oxalate powders were prepared through a precipitation stripping method with bis(2-ethylhexyl) phosphate (HDEHP) diluted by tetrachloride carbon as the extractant, and oxalic acid ethanol aqueous solution as the re-extractant and precipitator. Zinc oxide powders were obtained by decomposing zinc oxalate powders at 450°C. The prepared zinc oxide powders were characterized by transmission electron microscope (TEM), Scanning electron microscope (SEM), Thermogravimetric analysis (TG), X-ray diffraction (XRD) and Fourier transmission infrared (FT-IR) spectrum. The photocatalytic performance of methylene blue by zinc oxide was studied based on the Langmuir model and Photo-Layer model. The results show that some zinc oxide powders were micro-multipore materials with hexagonal crystal. The particle size was around 32 nm. The photocatalytic process was the control step in the chemical reaction. The photo catalytic process followed pseudo-first order kinetics and •OH concentration inside the photo-layer in different reaction condition were calculated according to the Photo-Layer model.
  • SHEN Boxiong, LIU Ting, SHI Zhanliang, SHI Jianwei, YANG Tingting, ZHAO Ning
    MnOx-CeOx/ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH3 at 80°C–150°C. The catalyst was characterized by N2-BET, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The fraction of the mesopore and the oxygen functional groups on the surface of activated carbon fiber (ACF) increased after the treatment with nitric acid, which was favorable to improve the catalytic activities of MnOx-CeOx/ACFN. The experimental results show that the conversion of NO is nearly 100% in the range 100°C–150°C under the optimal preparation conditions of MnOx-CeOx/ACFN. In addition, the effects of a series of performance parameters, including initial NH3 concentration, NO concentration and O2 concentration, on the conversion of NO were studied.
  • ZHAO Qian, WANG Shirong, LI Xianggao, HE Lili
    Six bisazo compounds were synthesized by coupling 2-(4′-aminophenyl)-6-aminobenzoxazole as diazo component with N-phenyl-N′-(2-hydroxy-3-naphthoyl)urea derivatives, and characterized by ultraviolet and visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). Using these bisazo compounds as charge generation materials and CT-191(2-methyl-4-(N,N-dibenzyl)aminobenzoaldehyde-1,1-diphenylhydrazone) as charge transportation material, organic photoconductive devices were prepared. The result from photoconductivity measurement of the devices shows that the bisazo compound from N-(2-methylphenyl)-N′-(2-hydroxy-3-naphthoyl)urea has the best xerographic performance, V0 = 600 V, VR = 30 V, Rd = 15 Vs-1, E1/2 = 3.5 lxs.
  • CHENG Yongxi, LI Hongtao, WANG Li, LÜ Shuxiang
    The preparation of hydrogen peroxide from anthrahydroquinone by reactive extraction was investigated. The integration process of oxidation of anthrahydroquinone by air and extraction of hydrogen peroxide from the organic phase with water was carried out in a sieve plate column under pressure. The conversion of anthrahydroquinone increased with increasing pressure resulting in an increase of hydrogen peroxide concentration in the aqueous phase. However, no change in extraction efficiency of hydrogen peroxide was observed. A mathematical model for gas-liquid-liquid reactive extraction was established. In the model, the effects of pressure and gas superficial velocity on reaction were considered. With increasing gas superficial velocity, the conversion of anthrahydroquinone increased, and the fraction of hydrogen peroxide extracted reached a plateau with a maximum of 72.94%. However, both the conversion of anthrahydroquinone and the fraction of hydrogen peroxide extracted decreased with increasing organic phase superficial velocity.
  • ZHAO Yongzhi, JIANG Maoqiang, CHENG Yi
    In order to simulate gas-solids flows with complex geometry, the boundary element method was incorporated into the implementation of a combined model of computational fluid dynamics and discrete element method. The resulting method was employed to simulate hydrodynamics in a fluidized bed with immersed tubes. The transient simulation results showed particle and bubble dynamics. The bubble coalescence and break-up behavior when passing the immersed tubes was successfully predicted. The gas-solid flow pattern in the fluidized bed is changed greatly because of the immersed tubes. As particles and gas are come in contact with the immersed tubes, the gas bubbles will be deformed. The collisions between particles and tubes will make the tubes surrounded by air pockets most of the time and this is unfavorable for the heat transfer between particles and tubes.
  • QIAO Congzhen, CAI Yonghong, GUO Quanhui
    The introduction of ionic liquids to alkylation process gives a choice for “green production” in the petrochemical and detergent industry. A lot of papers and patents have been published using chloroaluminate ionic liquid as a novel catalyst for alkylation with high reactivity and easy separation from reactants. These included the acidity, characterization, determination and catalysis technologies in batch and continuous operation mode for different scales. According to published data and several results of pilot alkylation,including the authors’ experience,the prospect of chloroaluminate ionic liquids for commercials was also discussed. It has been pointed out that there still are many difficulties and challenges to be overcome for commercial application of the ionic liquid catalyst.