Advanced Materials Research Vols. 347-353

Abstract: Natural gas (methane is the primary constituent) adsorbed on nanoporous materials is a promising alternative to compressed natural gas as a cleaning fuel. To understand the transport of methane confined in a nanoscale pore is useful for developing and optimizing some related industry processes. Equilibrium molecular simulation were carried out to study the transport behaviors of methane confined in two types silica pores, a cristobalite silica pore and an amorphous silica pore. Many factors, such as temperatures, densities of methane and surface structures of pore, which could affect the transport of methane, were examined in simulations. Simulations calculated the diffusion coefficients of methane at different densities and temperatures. The detailed microscopic structures of pores have a great correlation with the diffusion behaviors of methane. The diffusion coefficients of methane increased with increasing temperature, but decreased with the increase of density.

Abstract: Ocean wave power is emerging as a particularly attractive form of renewable energy. Dielectric Electric Active Polymers (DEAP) have has been used to transform electrical to mechani¬cal energy in an actuator mode. However it has few applications in a generator mode. This paper introduces a new concept of “New Renewable Energy” and presents a prototype of DEAP ocean wave powered generator, which has been developed at Knowledge Discovery Laboratory (KDL), Norwegian University of Science and Technology (NTNU). The DEAP prototype could be easily extended to other applications such as human-power generator, conventional power generators, and wind power applications.

Abstract: Olivine LiFe1−xMnxPO4/C composites were prepared by high temperature solid phase method using MnO2, NH4H2PO4, Li2CO3, FeC2O4•2H2O, glucose as the starting materials. XRD, SEM and constant-current charging/discharging tests were used to study the structure and electrochemical properties of the material. The result showed that when x=0.2 the material exhibited the optimal electrochemical performance, with a higher specific energy of 484.94 Wh/kg.

Abstract: The spinel nano-Li4Ti5O12 was prepared by hydrothermal reaction method. The crystal structure, morphology and charge/discharge capacities were characterized by powder X-ray diffraction and Scanning electron microscopy and program-controlled tester respectively. It showed that lithium titanate synthesized by the direct hydrothermal method has a uniform particle size distribution of about 100nm in cubic shape. Investigated the influence of different carbon sources on the structure and electrochemical properties. It was found that the discharge capacities could reach 172.2, 159.8, 156.2 and 148.3mAh/g at 0.2C, 1C, 2C and 5C rates, respectively.

Abstract: LiFePO4/C composite cathode material prepared by carbothermal reduction method was coated by metal oxide MnO2, Al2O3, CuO, respectively, by a chemical precipitation method. The effects of metal oxide coating on the structure and electrochemical performance of LiFePO4/C composites were systematically investigated. The structure and morphology of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the electrochemical properties were evaluated by constant-current charge/discharge cycling tests. It is found that the coating of metal oxide could greatly improve its high-rate dischargeability and cycling performance. The LiFePO4/C cathode material coated by MnO2 exhibits a specific discharge capacity of 118.5 mAh/g at 3C rate, much higher than the uncoated sample (95.1 mAh/g), with a capacity degradation rate of only 6.3 % after 250 cycles at 3C rate.

Abstract: Cobblestone-like CoSb3 nanoparticle films have been achieved via a catalyst-free vapor transport growth technique. The thermoelectric properties of the nanoparticle films were measured from room temperature to around 500 oC. The resultant CoSb3 nanoparticle films show high electrical conductivities due to clean particle surfaces. A maximum power factor reaches 1.848×10−4 W/mK2 at 440 oC. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.

Abstract: Commercial activated carbon was modified by surface treatment using nitric acid, The modified carbons were characterized by X-ray photoelectron spectroscopy (XPS). The resultant carbon electrode-based electric double-layer capacitors (EDLCs) were assembled with 1 mol/L (NH₄)₂SO₄ as the electrolyte. The influence of introduced functional groups, such as hydroxyl and carbonyl, on the performance of EDLCs was studied by Constant current charge-discharge. These functional groups significantly improved the wettability of AC. As a result, the specific capacitance of the carbon modified with 40wt.%HNO₃ achieved a specific capacitance of 223.45 F/g at a current density of 5mA/cm², which is 100.9% higher than that of original AC.

Abstract: A facile solid state method based chemical grinding method was applied to prepare high rate LiFePO₄. SEM test results showed that the prepared LiFePO₄ (CG-LiFePO₄) is more fine and uniform than that of the crude LiFePO₄ (C-LiFePO₄) prepared by conventional solid state reaction method. Electrochemical measurement results indicated that CG-LiFePO₄ exhibited much better high-rate characteristic than crude one which delivered a stable discharge capacity of 140 mAhg ^-1, 126 mAhg ^-1 at 0.5C rate and 2C rate respectively.

Abstract: In this paper, synthesis of RuO₂ with uniform nanosized sphere-like morphologies by ultrasonic precipitation using ammonia is presented. The structures, properties and electrocatalytic performance of materials were characterized by XRD, FE-SEM, CV and polarization curve. FE-SEM photographs showed that the sample prepared by ultrasonic precipitation has a relatively narrow size distribution compared with the sample prepared by conventional precipitation with magnetic stirring. The CV and polarization curve for OER (oxygen evolution reaction) confirmed that electrochemical active surface area and OER activity of sample by ultrasonic precipitation are higher than that of sample by conventional precipitation under magnetic stirring.

Abstract: Diamond film can be used as optical window materials, mask materials and coating materials of optical device and solar cells. Diamond films with different thickness were prepared by HFCVD method. Raman scattering measurement, SEM and AFM show a good diamond character. Optical parameters in infrared region, such as refractive index (n) and extinction coefficient (k) of diamond films with different thickness were determined by spectroscopic ellipsometry method with a proper fitting model.