Advanced Materials Research Vols. 774-776

Abstract: We optimized the CH₄ and H₂ gas flow rate of chemical vapor deposition (CVD) graphene growth and obtained larger area, fewer-layered graphene grown on Cu foils. After transfering to SiO₂ substrate by PMMA more than 3 times to repair the defect of monolayer graphene film, we synthesized large area, transparent and continuous graphene film. The morphology and structure were characterized by SEM and Raman spectroscopy. Analysis of electrical properties and optical properties show that we obtained low resistance and high transparency of ~90%, which could be used on photoelectric device as solar cell and acceptable for replacing commercial ITO electrodes.

Abstract: Graphene as high capacity anode materials for rechargeable lithium ion batteries (LIBs) have been studied extensively with the aim of enhancing lithium ion and electron transport, lowering the stress caused by their volume changes during the charge/discharge processes of electrodes in LIBs. As we know, graphite is a practical anode material used for LIBs, because of its capability for reversible lithium ion intercalation in the layered crystals, and the structural similarities of graphene to graphite may provide another type of intercalation anode compound. In this work, the anode electrodes of LIBs include graphene nanosheet (GNS) and graphene nanosheet + carbon nanotubes (GNS+CNT). GNS was prepared through the thermal exfoliation of oxided graphite (OGS), which was synthesized by a modified Hummers method. The specific capacity of GNS was found to be 280 mAh/g after 200 cycles at 1C, and this was increased up to 320 mAh/g by the incorporation of macromolecules of CNT to the GNS.

Abstract: In this work, nanoAlumina particles (nanoAl₂O₃) have been synthesized via solid state reaction. Effect of quantity of surfactant on particle size has been investigated. nanoAl₂O₃ was modified using chloroform as solvent and fatty acid as modifier at room temperature. The advantage of this modification is that it can be proceed at room temperature and it can reduce energy consumption. The products were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Abstract: The gas-liquid reaction method was used to prepare the nanoparticle iron-nitride magneto-rheological fluid (MRF), the experiment study of magnetic characteristic and rheologic characteristic of the MRF has been done. The magnetic saturation of iron-nitride MRF prepared is higher than the pure iron MRF, and the sedimentation stability of the iron-nitride MRF is very good, the yield stress of iron-nitride magneto-rheological fluid prepared reached 26KPa at 0.8 Tesla additional magnetic density.

Abstract: Two dimensional carbon/carbon composites (2D C/C) were prepared by the low temperature-heat molding technique with PAN based carbon fabric as reinforcement and pre-oxidation mesophase pitch as matrix precursors. The effect of pre-oxidation for mesophase pitch on microstructure and flexural strength of 2D C/C composites has been evaluated using polarized light optical microscope, scanning electron microscope and three-point bending tests. As pre-oxidation temperature rising, the softening point of mesophase pitch increases, oxygen-containing functional groups increases as well, QI (quinoline insoluble) content increases significantly. The flexural strength dependence of pre-oxidation temperature has been studied and correlated with microstructure of 2D C/C composites. Results show that flexural strength increase when the pre-oxidation temperature rising, and meet its peak at 140°C, reached 44.7514MPa.

Abstract: The aim of this paper is to contrast the effect of the microwave heating and traditional heating leaching vanadium from stone coal with sulfuric acid solution, contrast the leaching rate of vanadium, kinetics of leaching vanadium and the phase change s of slag. The experiment results show that the leaching rate and leaching velocity of vanadium with microwave heating was higher greatly than traditional heating, the kinetics of leaching vanadium with two heating methods was similar and accords with unreacted core contraction model with have solid product layer model, the illite in the stone coal was decomposed with microwave heating, but the traditional heating could not decomposed.

Abstract: Acid stability of Bacillus licheniformis alpha amylase (BLA) was improved by error-prone polymerase chain reaction. The mutated BLA gene was expressed in Escherichia coli. An acid stability double mutant (K344R/H405R in BLA) was isolated. Two single mutants K344R and H405R were obtained by the way of site-directed mutagenesis. The enzymes (BLA) of the three mutants were isolated and characterized. Kinetic studies showed that the k_cat/K_m values of the mutants K344R, H405R, and K344R/H405R under pH 4.5 were about 8-, 11.5-, and 17.7-times higher than that of the wild type enzyme. As revealed by the structure models of the wild-type and mutant enzymes, the amino acids substituted of R344 and R405 in the BLA contribute to its acid stability.

Abstract: Usually, the screw is placed in rotary kiln for calcination of selenium dioxide, so that the materials can be evenly conveyed in the rotary kiln. Through the software of Solid Edge, the geometric model could be established. The materials in the cylinder were regarded as the discrete particles. Then geometric model was imported into the EDEM and the particles movement simulation has been done. Without considering the floating of the screw in the cylinder, linear rotation speed of the cylinder and screw could be set. Through the simulation and analysis, the relative particles movement charts can be obtained. It provides certain reference value to the rotary kiln designing and the research of particles' axial movement in rotary kiln.

Abstract: The particle size and morphology have a strong influence on the electrochemical performance of FeS₂ electrodes. In this paper, a simple one-pot solvothermal method is reported for the synthesis of macroporous pyrite nanotubes for the first time. The phase composition, morphology and structure of the as-obtained products were studied by the energy dispersive spectroscopy (EDS), scanning electron microscopy, (high-resolution) transmission electron microscopy, X-ray diffraction. The electrochemical properties of the FeS₂ samples were also investigated. The results demonstrated that the macroporous pyrite nanotubes delivered a higher initial discharge capacity of 925.2 mAh g^-1 and had good capacity retention.

Abstract: Iron ore with high hydroxyl content such as goethit is widely spread in Indonesia. Such iron ore is not used as feed in ironmaking industry. However due to limitation of primary iron ore reserve such material is an option to substitute the conventional iron ore. Unfortunately the characteristic of iron ore with high hydroxyl content is totally different to conventional iron ore. Such iron ore contains hydroxyl part that can be released at high temperature. This research uses composite pellet which is mixture of iron ore and coal. The iron ore contains goethite which is one of iron phase. The composition of two materials is fixed 1 to 3 molar for iron total to fixed carbon. The mixture is formed a pelet before dried. The small part of dry pellet is analysed using STA with 0.6667 °K/s. The reduction is characterised based on thermogravimetry graphs. The research found that the reduction of iron ore occurs in some stages. First stage correspond to dehydroxylation at around 300 °C and second stage corresponds to reduction of iron ore at around 625 °C and 825 °C or 880 °C. The composite lost of 4.64 % and 2.85 % of weight. The hydroxylation is followed by reduction. Hydroxylation transforms goethite to hematite with lost of water. While the reduction transforms hematite to magnetite and magnetite to Fe.