Advanced Materials Research Vols. 724-725

Abstract: Magnesium-based hydrogen storage materials were prepared by reactive milling of magnesium under hydrogen atmosphere with crystallitic carbon, prepared from anthracite coal, as milling aid. The XRD analysis shows that in the presence of 30 wt.% of crystallitic carbon, the Mg easily hydrided into β-MgH₂ of crystal grain size 29.7 nm and a small amount of γ-MgH₂ after 3 h of milling under 1 MPa H₂. The enthalpy and entropy changes of the hydrogen desorption reaction are 42.7 kJ/mol and 80.7 J/mol K, respectively, calculated by the vant Hoff equation from the p-C-T data in 300-380°C.

Abstract: The low temperature performance of LiFePO₄/Li cells based on lithium oxalyldifluoroborate (LiODFB) with fluoroethylene carbonate (FEC) as addictive have been investigated. The result of ionic conductivity test shows that the use of 5% FEC can improve the conductivity of both LiPF₆ and LiODFB electrolytes at low temperature. The electrochemical measurements of the cells show that the use of FEC can effectively improve the discharge capacity and has better kinetics characteristics and low temperature performance. The LiODFB cell with FEC also exhibits excellent cycling retention of 88.8% after 50 cycles at-20°C.

Abstract: The electric resistivity, Seebeck coefficients and power factors of Y_1-xEu_xBaCo₄O_7+δ (x = 0.0, 0.05, 0.1, 0.2) ceramics were investigated from 400K to 1000K. The results show that the presence of Eu decreases electrical resistivity, and has little effect on Seebeck coefficients of the samples. The activation energy of conductivity is calculated by the Arrhenius plots in the semiconductive region. According to power factors, the optimum Eu substitution amount is x = 0.1, which results in a higher power factor of 67.5 μWm^-1K^-2 at 1000K, 30% higher than unmodified sample YBaCo₄O_7+δ.

Abstract: The crystal structure of magnesium hydride affects the properties of magnesium for hydrogen storage. The crystal phase and dehydriding temperature of magnesium hydride from magnesium by high-energy ball milling under hydrogen atmosphere with anthracite carbon, which was prepared from anthracite coal by demineralization and carbonization, as milling aid was investigated. The HRTEM observation and XRD characterization showed that the Mg hydrided into nanocrystalline β-MgH₂ of tetrahedral crystal structure and γ-MgH₂ of orthorhombic crystal structure during milling under 1 MPa of hydrogen, and the γ-MgH₂ increased with the extension of milling time. The DSC analysis showed that the endothermic peak of γ-MgH₂ was 53 °C lower than that of β-MgH₂ in the material from 10 h of milling.

Abstract: Carbon-coated ZnFe₂O₄ lithium anode with nanosize has been successfully synthesized by a one-pot green-chemical hydrothermal reaction with glucose as carbon source. An analysis of electrochemical performance showed that the prepared carbon-coated ZnFe₂O₄ anode exhibited high capacity retention. The initial charge-discharge specific capacity was approximately 1388 mAhg^-1 and 1008 mAhg^-1, respectively. And a reversible specific capacity could be maintained about 700 mAhg^-1 after 100 cycles at a constant current density of 100 mAg^-1, indicating good cycle ability compared with majority reported literatures. The excellent electrochemical performance was related to the carbon coating and nanoparticles, with which the electric conductivity of the material increased and the volume expansion and pulverization of the particles became increasingly reduced.

Abstract: Applying thermogravimetry coupled with mass spectrometry, a pyrolysis analysis of a long flame coal from Chinese Hami was carried out. The results show: In the temperature range between 400°C and 600°C, the degradation of the carbonaceous matrix and the evolution of relatively high molecular weight species result in the abundant release of CH₄, C₃H₆, C₆H₆, C₇H₈, C₈H₁₀ and otherwise gas in the coal sample. The weight loss between 400°C and 600°C occupies a main proportion in the total weight loss. In the temperature range between 600°C and 900°C, the condensation of the aromatic ring and the decomposition of mineral matter result in the abundant release of H₂, CO₂, C₆H₆ and otherwise gas.

Abstract: Applying X-ray diffraction, an analysis of crystallite structure on the coal samples from Hami, including raw coal and coals heated respectively at 200°C, 250°C and 300°C, was carried out. The results show: The intensity of the 002 diffraction peak increases, the γ diffraction peak of the coals decreases, the 100 diffraction peak appears and its intensity increases, the size of the crystallite, the stacking height of the aromatic layer and the condensation degree of the aromatic rings increase, and the proportion of the non-crystallite decreases in coal samples, with the temperature increasing at below 300°C.

Abstract: In this study, coal samples of experimental come from the raw coal of Wangfenggang and Qidong. Sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), water-reducing admixture NF and Tween-80 are choosed as surfactants. The influence factors on wettability of coal dust were characterized by contact angle meter, fourier transform infrared spectroscopy (FTIR) and surface tension experiment. The research shows that the effect of solution on wettability of coal dust is mainly depended on the surface structure of coal dust, type and concentration of solution.

Abstract: In this study, the trench oil was processed by the technology of polyol pre-esterification and the bio-diesel was prepared using basic ionic liquid 1-methyl-3-butyl-imidazole hydroxide as a catalyst. The amount of ionic liquids, alcohol and oil molar ratio, reaction temperature and reaction time were investigated on the transesterification reaction. The results showed that the bio-diesel prepared conditions by trench oil are as follows: alcohol and oil molar ratio of 8:1, reaction temperature 70°C, reaction time 110min and the amount of catalyst for the quality of raw materials 3.0% oil. Under these conditions, fatty acid methyl ester was 95.7% conversion rate.

Abstract: The consist property analysis of Daqing and Nile-Oman high wax crude oil and Liaohe super-viscous crude oil was carried on in the paper. The result showed the key factor of high wax crude oil pour point increasing lies in the wax crystal forming and growing and agglomerating at low temperature. The reason of high viscosity of Liaohe super-viscous crude oil has correlation to the high nitrogen polar group weight. The polar groups can form hydrogen bond to make adhesion stronger. At the same time, the crude oil flowing was restrained by increase the macromolecule connection agglomeration in crude oil. The analysis of resin wax ratio of crude oil showed the better viscosity decline effect was appeared only in the condition of resin wax ratio was appropriate.