Search

Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate (TEOS) in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nafion membrane and the thermo stability of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. Furthermore, the tensile strength of Nafion/Silicon oxide composite membrane is similar to that of the Nafion membrane. The proton conductivity of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. When the Nafion/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC, a higher current density value (1 000 mA/cm2 at 0.38 V) than that of the Nafion1135 membrane (100 mA/cm2 at 0.04 V) was obtained at 110 °C.

A new composite bipolar plate was fabricated by compression molding technique using polyvinylidene fluoride (PVDF) as binder and titanium silicon carbide (Ti 3 SiC 2 ) as conductive filler. The effects of Ti 3 SiC 2 content, the particle size of Ti 3 SiC 2 , the mould pressure and mould pressing time on the electrical conductivity and the flexural strength of the conductive composite are discussed. The electrical conductivity and flexural strength of the composite bipolar plate with 80 wt.% Ti 3 SiC 2 content, prepared with a mould pressure of 10 MPa for 10 min, was 28.83 S cm −1 and 24.92 MPa, respectively, and can be improved by optimizing the Ti 3 SiC 2 content and Ti 3 SiC 2 particle size. The electrical conductivity of the composite can also be improved by improving the mould pressure and prolonging the mould pressing time.

Aluminate cement/graphite conductive composite bipolar plates were prepared by mould pressing at room temperature. The effects of the graphite content, the mould pressing pressure and mould pressing time on the electrical conductivity and the flexural strength of composite are discussed. The electrical conductivity and the flexural strength of the composite bipolar plates with 60 wt.% graphite content, prepared with a mould pressing pressure of 5 MPa for 10 min, is >100 S cm −1 and 20 MPa, respectively and can be improved by optimizing the mould pressing conditions, especially mould pressing time. The water content of the composite bipolar plate with different graphite contents was also investigated. The water content of the composite bipolar plate is about 6 wt.% with a graphite content of 60 wt.%. This composite bipolar plate contains capillary pores and has hydrophilicity, which is different from other composite bipolar plates. Therefore, it possesses an inner humidifying function and can use the water produced at the cathode for humidifying the proton exchange membrane during the operation of a PEMFC. In addition, the H 2 permeability of the composite bipolar plate is low.

A group of liquid catalysts composed of nicotinic amide functioning on the anode of DMFC were investigated at a Pt electrode, which were nicotinic amide, nicotinamide adenine dinucleotide (NAD+) and its phosphate (NAD(P)+). The kinetics of methanol anode oxidation in the three reaction systems was compared by measuring potentiodynamic current-potential curves and AC impedances. The experimental results show that the dynamic behavior of methanol oxidation at a Pt electrode has been changed with adding the three substances. The influence of temperature on the catalysis of these coenzymes and nicotinic amide was discussed by comparing the AC impedances spectra of methanol oxidation at different temperatures.

Sodium silicate/graphite conductive composites are prepared by mold pressing at room temperature. The effects of graphite content, size of graphite particles, mold pressing pressure, and mold pressing time on the electrical conductivity of composites are discussed. The density and the water content are composites with different graphite content and are also investigated. The optimized preparation conditions are determined. The results show that the electrical conductivity, the density, and the water content of sodium silicate/graphite composite bipolar plate for proton exchange membrane fuel cell (PEMFC) is >100 s/cm, 1.8g/cm3, and 9 wt%, respectively. The density of this composite bipolar plate material is smaller than that of another bipolar plate. This composite bipolar plate material contains gel capillary pores and has sufficient hydrophilicity, which can humidify the proton exchange membrane during the operating process of PEMFC.

This paper deals with the crystallization of MgO during sintering of Si3N4-MgO-CeO2 ceramics. At the initial stage of sintering (1450–1550°C), MgO-CeO2 reacts with free silica to form sufficient liquid phase to densify Si3N4 into nearly full density ceramics; at final stage (1600–1800°C), the crystallization of MgO reduces the amount of glassy phase which is harmful to the high-temperature properties. MgO-CeO2 is found to be an excellent sintering aid for Si3N4.

Several methods of manufacturing γ-aluminium oxynitride spinel (ALON) powder are discussed in this paper. In the carbothermal reduction process, ALON is an intermediate compound, and powders with a high ALON content may be produced in flowing nitrogen below 1650 °C if process parameters are carefully controlled. In addition, ALON may be produced when Al2O3/C mixtures are heated in a coke powder bed above 1650 °C. In the reaction sintering process, ALON is unlikely to form below 1600 °C in a flowing nitrogen atmosphere or in a coke powder bed, owing to the instability of ALON and the fact that the solid–solid reaction does not readily occur unless additives, e.g. MgO, MgAl2O4, are employed.

The PAn-PEO-PAn triblock copolymer with the PEG chain length of 400 was synthesized by chemical oxidation copolymerization of aniline and α, ω-bis(p-aminophenyl) poly(ethylene glycol) and characterized by FT-IR and TEM. The experimental results show that the copolymer particles are of a typical core-shell structure after the self-assembly process in water. Its conductivity is much lower than that of the pure PAn. The suspension containing 20 vol% PAn-PEO-PAn triblock copolymer in silicone oil exhibits a typical electrorheological (ER) effect in DC electric field, while it shows a lower leakage current density than that of the pure PAn-based ER fluids. Therefore, the PEO shell hinders the electric hop among PANI chains and decreases the current density of ER fluids in an external electric field, at the same time the interface polarity imprones the ER effects.

Nafion modified Pt nano-particles with size about 4nm were synthesized. The modified particles were absorbed on the surface of carbon nanotubes and used as electro- catalysts for proton exchange membrane fuel cell. Due to the plentiful proton channels provided by the modifying Nafion ionomers, the single fuel cell with the modified Pt catalyst has a promised performance. The output was 0.282W/cm^2 with Pt loading of 0.1 mg/cm^2, better than that of unmodified one, which was 0.273W/cm^2 with Pt loading of 0.11mg/cm^2.

Ammonium metatungstate and cobalt nitrate were mixed at the molecular level in distilled water and then spray-decomposed to CoWO4/WO3 nanocomposite powder. The particle morphology, crystalline size, forming course, chemical composition and phase structure of the powder were studied by SEM, TEM, DTA-TG, IR and XRD, respectively. Results show that the powder is homogeneous, spherical and nano-aggregated.

The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer (XRD), scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP) etc. The experimental results indicate that hydration products of the materials are entringites (AFt), aluminium hydroxide and CSH (I) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of cement grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration reaction was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates AFt, CSH (I) and aluminium hydroxide gel fill in pores. The expansibility of AFt makes the porosity of MDF cement lower (less than 1 percent) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

The nanocomposite films were prepared by direct intercalation of poly(ethylene oxide) and PEO into MoO3 xerogel via sol-gel route. The electrochromic behavior and the chemical conditions of Li+ ions were investigated by cyclic voltammograms, UV-visible spectral transmittance and XPS. The results show that the cycling efficiency and the reversibility of insertion/extraction of Li+ ions in (PEO)1MoO3·nH2O nanocomposite film were improved. The intercalation of PEO into MoO3 xerogel modulated the wavelength range of electrochromism and enhanced the electrochromic efficiency. Two different chemical conditions of Li+ ions existing in the interlayer and interstitial positions of MoO3 lattice were observed in MoO3 xerogel and (PEO)1MoO3·nH2O nanocomposite films.

A new method is introduced to study the action between biomaterials and organism. By using an LKB-2277 bioactivity monitor and ampoule method, the fundamental thermogenesis curves of the metabolic process of pk-15 and the toxic effect of three kinds of selenomorpholine compounds on it were studied at 37°C. From the thermogenesis curves, the heat released by pk-15 metabolism was calculated. The results show that the selenium compounds all have toxic action on the metabolism process of pk-15 at the range of experimental concentrations. The sequence of the toxic action of selenium compounds is: Na2SeO3>β-(N-selenomorpholine)-ethyl phenylketone hydrochloride>selenomorpholine.

Composite particles consisting of polyaniline (PAn) core and barium titanate (BaTiO3) layer shell were synthesized. The PAn-BaTiO3 composites particles were characterized with TEM and XRD. The dielectric behavior of particles was tested and the electrorheological (ER) behavior of the suspensions of PAn/BaTiO3 particles in chlorinated paraffin oil with a 20 vol% was investigated under DC electric field. The results show that the ER effect of composite particle is far stronger than that of pure polyaniline and barium titanate which were synthesized by the same method. pH and thickness of BaTiO3 have an important influence on the ER effects.

Various silicon nitride materials have been prepared by pressureless sintering using MgO/CeO 2 as sintering aids. The weight fractions of MgO+CeO 2 added were 2, 4, 6, 8, 10, 12, and 14%, respectively, corresponding to MgO/CeO 2 weight ratio of 1/1, and constant 10 wt.% of MgO+CeO 2 were added in the ratios 0/10, 2/8, 4/6, 5/5, 6/4, 8/2, and 10/0, respectively. The densification effect of the combination of MgO with CeO 2 is much better than either MgO or CeO 2 alone. The optimum MgO/CeO 2 weight ratio is 1/1 and the optimum MgO+CeO 2 concentration is 8–10 wt.%, resulting in a relative density of 98.5% and a bending strength of 948 MPa for the pressureless sintered Si 3 N 4 –MgO–CeO 2 ceramics.