Gas-phase hydroxylation of benzene over H–Ga-FER zeolite

The direct hydroxylation of benzene with N₂O is studied using H–Ga-FER zeolite as catalyst. The H–Ga-FER zeolite was synthesized by using the hydrothermal synthesis route. Pyrrolidine was used as a template. The catalyst was characterized by using XRD and NMR techniques. The gas-phase hydroxylation reaction was carried out using nitrous oxide gas as an oxidant. The reaction was thoroughly studied by changing different parameters like temperature, time, reactant mole ratio and contact time (WHSV). It was observed that by using H–Ga-FER, phenol was formed with 100% selectivity. The deactivation is faster in case of H–Ga-FER as compared with Al-FER and Fe-FER. This revised version was published online in July 2006 with corrections to the Cover Date.     

Catalytic effect of nickel under carbonization of polyimide films

In attempt to produce graphite films with high crystallinity by heat-treatment at temperatures lower than 3000 °C, the catalytic effect of nickel was investigated for carbonization of polyimide films prepared by mixing polyamic acid with nickel particles. The three-layered polyimide film was prepared to obtain graphite films with thickness beyond 100 μm. The middle layer composed of polyimide with nickel particles. The thickness of each layer was 50 μm and the film thickness became 150 μm. The carbonization was done at ca. 1600 °C for 5 h. The morphology of the carbonized films was observed by scanning electron microscopy. The graphitization degree was investigated on the basis of X-ray diffraction intensity distribution from the (0 0 2) plane. The analysis was done in terms of the comparison between the experimental and theoretical diffraction intensity curves. The theoretical calculation was carried out by using a concept for the para-crystalline theory proposed by Hoseman and Bagchi from the viewpoint of the lattice fluctuation of the c-axis.     

Preparation and Characterization of C10–C14 Alkyl Cellulose Ester Sulfate Surfactant

The aim of this work is to synthesize surfactants based on cellulose with different molecular weights. Raw cotton cellulose was tailored into cellulose segments with different molecular weights by a hydrothermal process, then the average degree of polymerization (DP) was determined by viscosimetry and the molecular weight distribution was estimated by gel permeation chromatography. The C₁₀–C₁₄ alkyl cellulose ester sulfate surfactants were prepared by hydrophilic sulfonation and hydrophobic esterification. The surface tension of the surfactants solution was obtained by the Wilhelmy plate method. Results showed that the cellulose segments presented a broader distribution compared with the raw material. The critical micelle concentration (CMC) value decreased from 1.08 to 0.86 wt% as the hydrophobic chain length was increased from 10 to 14. The CMC values of cellulose surfactants with C₁₄-acyl chloride hydrophobization decreased from 1.32 to 0.86 wt% as the DP was decreased from 2,700 to 296.     

Preparation of ultra high molecular weight polyethylene with MgCl<Subscript>2</Subscript>/TiCl<Subscript>4</Subscript> catalyst: effect of internal and external donor on molecular weight and molecular weight distribution

Ultra high molecular weight polyethylene (UHMWPE) was prepared by using MgCl₂-supported TiCl₄ catalyst in conjunction with triethylaluminium (TEA) cocatalyst. The effects of internal and external donor on polydispersity index (PDI) of UHMWPE were investigated. The catalyst activity with various kinds of internal donor decreased in the following order: none > succinate > phthalate > diether, while the catalyst activity was less influenced by the structure of external donor. The PDI of UHMWPE was examined by using gel permeation chromatography (GPC) analysis and/or rheometry measurements. The PDI obtained by rheometer was matched with the results obtained by GPC within an error of max. 20%. The highest molecular weight and PDI of UHMWPE were obtained by the catalyst of succinate as internal donor. It was also observed that the molecular weight and PDI of UHMWPE were less affected by the introduction of external donor.     

Photoelectrocatalytic degradation of rhodamine B using Ti/TiO2 electrode prepared by laser calcination method

The method of Ti/TiO₂ photoelectrode prepared by using laser calcination method instead of oven calcination process was introduced. The prepared TiO₂ film was observed with AFM and XRD. Photoelectrocatalytic degradation of rhodamine B (RB) using this electrode was investigated, and anodic potential and pH were optimized. The laser power applied in this electrode preparation was also discussed, and it indicated that TiO₂ particle prepared with high laser power was crystallized adequately and the photoelectrocatalytic ability was satisfactory. RB degradation was investigated under different conditions, and it showed that photoelectrocatalytic degradation could achieve efficient and complete mineralization of organic pollutant. The photoelectrocatalytic oxidation using the Ti/TiO₂ electrode calcinated by laser was compared with that of the electrode calcinated by furnace, and it showed that the reaction rate of RB degradation using the electrode by laser was faster than that by furnace. Additionally, electrochemical impedance spectroscopy (EIS) was performed at the two different photoelectrodes, which verified the higher photocatalytic activity of the laser-treated electrode further.     

Porous scaffold prepared from α′L-Dicalcium silicate doped with phosphorus for bone grafts

α′_L-Dicalcium silicate ceramic doped with phosphorus in subsystem Ca₂SiO₄?7CaO·P₂O₅·2SiO₂ was used as a template to prepare a porous scaffold by the burnout technique using cellulose as porogen. A phase composition study of the ceramics prepared after porogen removal was performed by XRD and SEM-WDS in contrast to the base material. An analysis of the inter- and intraparticle pores network was run by mercury porosimetry. Density was measured by helium pycnometry. The scaffold's porosity was measured using Archimedes’ method by immersion in mercury. The in vitro behavior in SBF of the monophasic scaffold was analyzed by SEM-WDS, FTIR-ATR and TEM for several time periods. The processing technique allowed scaffolds to be easily and cheaply obtained with porosities of up to 81% by combining macro- and microporosity. The specific area effectively increased which, together with the good bioactivity rate obtained, make this material a promising candidate for bone grafts in tissue engineering.     

Study on the graphite nanosheets/resin shielding coatings

Shielding coatings based on graphite nanosheets were prepared by compounding method. The surface morphology of the graphite nanosheets and conductive coatings was examined by scanning electron microscopy. The surface resistivity of the coatings was greatly declined by incorporating the graphite nanosheets. The electromagnetic interference shielding effectiveness (SE) from 0.3 MHz to 1.5 GHz was also studied, and found that the SE of the coatings was consistent with its conductivity. The best sample was shown to exhibit up to 38 dB of SE at 1.5 GHz (with a thickness of 400 μm). The main shielding mechanism of the system was reflection and multiple reflections.     

The Improvement of Electrical Property of Multiwalled Carbon Nanotubes with Plasma Modification and Chemical Oxidation in the Polymer Matrix

We prepared a series of multiwalled carbon nanotube/polymer nanocomposites with two types of tube. One was plasma-modified with maleic anhydride and the other was modified with acid and the same plasma treatment. The morphology of the modified multiwalled carbon nanotube was observed by transmission and scanning electron microscopy. The surface structure was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The optimum conductivity of multiwalled carbon nanotube/polymer nanocomposites with specific ratios was of the order of 10⁻³ S/cm for a total MWCNT content of 2.0 and 2.5 wt%.     

Synthesis and characterization of poly (amide-imide-imide)s based on diacids with bulky m-chloro phenyl moiety and rigid pyridine moiety

A series of novel aromatic diamines containing kinked m-chloro phenyl moiety was synthesized by the reaction of m-chloro benzaldehyde with 2,6-dimethyl aniline. The tetraimide diacid was synthesized by using the prepared diamine with benzophenone tetracarboxylic acid dianhydride (BPTDA) and p-amino benzoic acid. The polymers were prepared by treating the tetraimide diacid with different aromatic diamines. The structures of the monomers and polymers were identified by ¹H-NMR, FTIR,¹³C-NMR and elemental analysis. The polymers showed excellent thermal stability, solubility and mechanical properties. Their structure–property relationship was studied by comparing these m-chloro polymers with polymers containing rigid Pyridine moiety.     

Enhanced photoluminescence property and mechanism of Eu3+‐doped tellurite glasses by the silver and gold nanoparticles

In this work, the silver or gold nanoparticle single‐existing and co‐existing tellurite glasses doped with Eu³⁺ were prepared, and the influence of gold or silver nanoparticles on the photoluminescence of tellurite glasses doped with Eu³⁺ were investigated. The photoluminescence of tellurite glasses doped with Eu³⁺ was enhanced by the surface plasmon absorption of gold or silver nanoparticles, and the maximum luminescence enhancement factors caused by the silver and gold nanoparticles are 4.8 and 3.5 factors, respectively. The differentiation of luminescence enhancement mechanisms caused by the gold or silver nanoparticles was demonstrated. The enhanced luminescence mechanism of the Au nanoparticle single‐existing tellurite glasses doped with Eu³⁺ was from the increasing of radiative decays rate caused by the Au nanoparticles. The excitation field enhancement caused by the Ag nanoparticles was responsible for the luminescence enhancement of the Ag single‐existing tellurite glasses doped with Eu³⁺. About 4.2‐factor luminescence enhancement was observed in the Ag and Au nanoparticle co‐existing tellurite glasses doped with Eu³⁺, which is attributed to the increasing of radiative decays rate and excitation field enhancement caused by the Au and Ag nanoparticles.     

Preparation of carbon fiber/Mg-doped nano-hydroxyapatite composites under low temperature by pressureless sintering

In order to protect carbon fibers (CF) from oxidation damage during sintering process, rod-like Mg-doped nano-hydroxyapatite (Mg-nHA) with an increased thermal decomposition temperature and reduced sintering temperature was synthesized by hydrothermal method. The synthesized bone-like Mg-nHA with similar composition and morphology to bone apatite was used as the matrix to prepare CF reinforced Mg-nHA composites (CF/Mg-nHA) at a low temperature of 700 °C by pressureless sintering. The increase of temperature slightly influenced the growth of Mg-nHA prepared by hydrothermal method from 160 °C to 200 °C. The Mg-nHA were short and rod-like in structure with a length of approximate 100 nm. When doping 1% magnesium, the decomposition temperature of Mg-nHA increased by 100 °C compared with that of nHA. This can protect CF from oxidation damage which is often encountered when sintering CF reinforced hydroxyapatite composites at high temperature and enhance reinforcing effects of CF. The bending strength of CF/Mg-nHA with 1 wt% CF was 8.51 MPa, which increased by 19.5% compared with Mg-nHA. Alternatively, the rod-like Mg-nHA was prepared on the surface of CF by electrochemical deposition and Mg-nHA coated CF was used to reinforce Mg-nHA, the coefficient of thermal expansion mismatch between CF and HA matrix could be mitigated. The compressive strength of Mg-nHA coated CF reinforced Mg-nHA (CF/Mg-nHA/Mg-nHA) composites with 0.5% CF sintered at 800 °C were 41.3 ± 1.56 MPa, which was attributed to the improved strengthening effect of CF and the good interface between CF and Mg-nHA matrix.     

Waterborne polyurethane-acrylic copolymers crosslinked core–shell nanoparticles for humidity-sensitive coatings

A novel crosslinked core–shell emulsion of waterborne polyurethane-acrylic copolymers (PUA) was successfully synthesized by emulsion polymerization. The average particle size of the PUA particle was approximately 130 nm and its core–shell morphology was proved with transmission electron microscopy (TEM) and dynamic light scattering (DLS), whose structure was also confirmed by FT-IR and TGA. PUA was applied to prepare the humidity controlling coatings (PUA-C) by compositing with pigments and porous fillers. The structure and properties of humidity controlling coatings were investigated, with particular attention to the effects of the humidity controlling. The surface morphology of the PUA-C was observed by scanning electron microscope (SEM). The humidity controlling coatings showed excellent properties of humidity sensitivity and humidity retention.     

Synthesis and characterization of tetrafluorophenyl phosphonic acid functionalized polyacrylates as potential proton conducting materials in fuel cells

Novel acrylate polymers functionalized with tetrafluorophenyl phosphonic acid groups were prepared by free radical polymerization of phosphonic ester acrylate monomers. Liberation of the free acid functions was realized by ester cleavage with Me₃SiBr and the subsequent hydrolysis with methanol. The obtained polymers were analyzed by NMR and IR spectroscopy. The ion exchange capacity of the phosphonic acid functionalized methacrylate polymer was determined to 2.8 mmol/g by titration with 0.1 M NaOH. The proton conductivity under anhydrous conditions was determined to 6.84 × 10⁻⁶ Scm⁻¹ at 120°C by electrochemical impedance spectroscopy.     

New polymer syntheses. V. Synthesis,characterization, and morphology of new conjugated polymers,copolymers, and terpolymers containing piperidone moiety in main chain

A new interesting category of polyconjugated polymer, poly(3,5‐benzylidene)isopropylpiperidone, was obtained by condensation of isopropylpiperidone with terephthalaldehyde. Copolymerization and terpolymerization with cyclopentanone and/or cyclohexanone were also carried out. The model compound was prepared by the condensation of 2 mol benzaldehyde with isopropylpiperidone; the structure was elucidated by IR, ¹H‐NMR spectra, and elemental analyses. The polymers, copolymers, and terpolymers were characterized by elemental analyses, IR, ¹H‐NMR spectra, UV and visible spectra, viscometry, and X‐ray analysis. The thermal behavior of the synthesized polymers was evaluated by TGA and DSC analyses and correlated with their structures. The morphology of terpolymer IV was examined by a scanning electron microscope. Electrical conductivities in the 10⁻⁹–10⁻¹¹ Ω⁻¹ cm⁻¹ range were observed: doping with iodine showed a small increase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2369–2377, 1999     

党参多糖的提取及其对活性氧自由基的清除作用

中药党参经热水提取 ,乙醇沉淀得粗品党参多糖 ,Zn SO4 法去蛋白 ,再经 Polyerde吸附 ,60°C热水脱附 ,乙醇沉淀 ,真空干燥得纯品党参多糖。实验测定了党参多糖对 O-·2 和 OH· 的抑制作用 ,结果表明党参多糖对O-·2 和 OH· 均有良好的清除能力     

Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method

A discrete element method (DEM)-computational fluid dynamics (CFD) two-way coupling method was employed to simulate the hydrodynamics in a two-dimensional spouted bed with draft plates. The motion of particles was modeled by the DEM and the gas flow was modeled by the Navier-Stokes equation. The interactions between gas and particles were considered using a twoway coupling method. The motion of particles in the spouted bed with complex geometry was solved by combining DEM and boundary element method (BEM). The minimal spouted velocity was obtained by the BEMDEM-CFD simulation and the variation of the flow pattern in the bed with different superficial gas velocity was studied. The relationship between the pressure drop of the spouted bed and the superficial gas velocity was achieved from the simulations. The radial profile of the averaged vertical velocities of particles and the profile of the averaged void fraction in the spout and the annulus were statistically analyzed. The flow characteristics of the gas-solid system in the two-dimensional spouted bed were clearly described by the simulation results. __________ Translated from Chemical Engineering (China), 2007, 35(6): 24–28 [译自: 化学工程]     

Curing of epoxy resins with citric acid–piperazine salt

Citric acid–piperazine salt was prepared with a molar ratio of acid–piperazine of 2.9. The salt was characterized by thermal calorimetry, ¹³C NMR and IR spectroscopy. The piperazine content in the salt was 52%. A typical formulation was achieved by mixing the salt with the diglycidyl ether of bisphenol A (DGEBA). The heat of reaction was measured by a calorimeter and the evaluated peak resulted from the simultaneous endothermic salt decomposition and exothermic network formation. The heat of reaction value was −ΔH = 18kJ/eq. for the stoichiometric ratio, and the glass transition temperature, T_g, was 95°C. The heat of reaction evolved and the T_g value of piperazine–epoxy were determined for comparison with the salt–epoxy system.     

Synthesis of polyhydrazones by diazo coupling reaction of bisacetoacetamides with diazonium salts

Summary Hydrazone polymers were prepared by the diazo coupling reaction of bisacetoacetamides with diazonium salts under mild basic conditions. Bisacetoacetamides 1 and 2 having two 1,3-diketo groups were prepared by the reaction of aromatic diamines with diketene. Diazonium salts 3–5 were prepared by the reaction of aromatic diamines with nitrous acid in an aqueous HCl. A diazonium salt was isolated in a stable form after exchanging chloride with fluoroborate. The resulting polymer structure was determined by spectroscopic methods to be mainly polyhydrazone. The hydrazone unit was found stabilized by the intramolecular hydrogen bonding. The polymer obtained from 2 and 5 was soluble in organic solvents and showed the UV maximum peak at 376 nm in dimethyl sulfoxide. Received: 2 February 2001/Accepted: 13 March 2001     

Preparation of PVDF/PVP core–shell nanofibers mats via homogeneous electrospinning

The polyvinylpyrrolidone (PVP)/poly(vinylidene fluoride) (PVDF) core–shell nanofiber mats with superhydrophobic surface have been prepared via electrospinning its homogeneous blending solutions, and the formation of the core–shell structure was achieved by the thermal induced phase separation assisted with the low surface tension of PVDF. The electrospinnability of the blending solutions was also investigated by varying the blending ratio of the PVP and PVDF, and it enhanced with the increase of PVP content. SEM and TEM results showed that the fibers size was varied in the range of 100 nm–600 nm with smooth surface and core–shell structure. The composition of the shell layer was determined by the XPS analysis, and further confirmed by water contact angle (WCA) testing. As the fraction of PVDF exceeding PVP in the electrospinning solutions, the nanofiber mats showed superhydrophobic property with the WCA above 120°. It indicated that the PVDF was concentrated in the shell layer of the fibers. X-Ray diffraction (XRD) and attenuated total reflection infrared spectroscopy (ATR-IR) analysis indicated that the PVDF was aggregated with the β-phase crystallite as dominant crystallite. The nanofiber mats with the gas breathability and watertightness ability due to the porous structure and superhydrophobic would be potential applied in wound healing.