Advanced Materials Research Vols. 1070-1072

Abstract: We investigate electronic transport properties of molecular device models constructed by a dipyrimidinyl–dimethyl molecule embedding in a carbon chain, which are then coupled to the gold electrodes through thiol or isocyanide group. Using the density functional theory combined with the nonequilibrium Green’s function method, negative differential resistance behaviors are observed in such molecular junctions. Most importantly, system with the isocyanide group can achieve a larger negative differential resistance at lower bias voltage (0.1V).

Abstract: A novel two-dimensional carbon nanomaterials was prepared through a facile hydrothermal method, using glucose as the carbon precursor and sodium borohydride as the structure directing agent. The application of as-obtained carbon nanomaterials after annealing in inert atmosphere as the anode of lithium ion batteries (LIBs) was explored. The results demonstrate the carbon nanomaterials can exhibit more excellent lithium storage properties with high capacity and superior rate properties than the graphite as a kind of common anode materials.

Abstract: SrFe_0.9Al_0.1O_3-δ (SFA) powder was mixed with a different mass content of SDC 10, 20 and 30 wt.% to form SFA-SDC composite cathodes subsequently investigated as potential IT-SOFC cathodes on LSGM electrolytes. No obvious reaction products between SDC (or LSGM) and SFA occur under test for the cathode of SOFCs. As SOFC cathodes, the area-specific resistances of the SFA-SDC cathodes on the LSGM electrolyte with SDC 10, 20 and 30 wt.% at 800 oC are 0.089, 0.068 and 0.087 Ω cm², respectively. The peak power density of the SFA-SDC20 on a 300 μm-thick LSGM electrolyte reach 512 mW cm⁻² at 800 °C.

Abstract: As a fascinating two-dimensional nanomaterial, graphene is attractive for electrocatalytical application in direct methanol fuel cells due to its unique structure and outstanding physical properties. Graphene and its derivatives have been widely used as a support material to improve electrocatalytical activity of catalyst particles for methanol and ethanol oxidations. In this review, discussion is focused on the graphene supported monometallic and bimetallic nanocrystals hybrid materials for electrocatalysts. Additionally, the nitrogen-doped graphene utilized for promising support material in electrocatalysts was also mentioned. We believe that the article will be useful to researchers interested in graphene-based catalyst and related materials for direct methanol fuel cells and provide the present status of the subject.

Abstract: The static crucible method was employed to effects of different additions and coal mixing ratios on burning rate. The optimal amount was 4% and mixing ratio was Semicoke-Jincheng coal=7:3. XRD and TGA techniques were used to characterize combustion process. The combustion-supporting mechanism was that Mn⁷⁺(CO^-)₇ weakens the bridged bond binding force among carbon structure units and changes lattice structure. Heat storage preparation time is shortened which accelerates pulverized coal combustion.

Abstract: The desulfurization process of high-sulfur coal in Weibei was studied by flotation pretreatment and microwave combined with ultrasonic wave and oxidants. Through the single factor experiment which took Chenghe coal as the sample, the optimum conditions of this process had been concluded as follows: microwave power was 250 W, microwave time was 15 min, ultrasonic temperature was 60 °C, ultrasonic time was 30 min, coal slurry concentration was 0.083 g/ml, coal particle size was less than 0.074 mm, the dosage of agents was 8 mL/g, the radio of acetic acid and hydrogen peroxide was 1:3. After fractional release pretreatment, the sulfur reduction of Chenghe coal could reached to 53.10%. As to Hancheng coal, the value was 46.41%. By analyzing XRD and XPS spectra, it showed that most inorganic sulfur were removed by flotation pretreatment, and under the function of microwave combined with ultrasonic wave and oxidants, a part of organic sulfur was removed, such as mercaptan, sulfoxide and thiophene. However, as for sulfone, the removal effect was not obvious. The results proved that the experimental method could remove most of inorganic sulfur and part of the organic sulfur and significantly reduce the coal ash.

Abstract: The reason why the failure protective properties of the oxide layer of T91 high temperature superheater tube were analyzed in this study. The microstructure of the oxide layer of T91 high temperature superheater tube was observed by scanning electron microscope (SEM) and the morphological features of it was also analyzed. The concentrations of alloy elements in the section of internal tube were quantitatively analyzed using Energy Dispersive System (EDS). The results showed that the oxide layer of T91 tube can be divided into three layers: inner layer, middle layer and outer layer. The inner layer was formed by chromium rich oxide with compact structure. The middle layer was made up by porous oxide with loose structure. The outer layer was identified as Fe₂O₃. When the content of dissolved oxygen in steam was excessive, the apparent peeling marks will be appeared in the oxide layer of T91 high temperature superheater tube and the distribution of alloy elements in the oxide layer will present obvious proliferation, migration and enrichment phenomenon. Two different mechanisms (steam oxidation mechanism and oxygen oxidation mechanism) will exercise different influences on the structure and protective properties of the oxide layer: when steam contained dissolved oxygen, the oxide layer will be peroxidated by steam and the structure of oxide layer will be broken; When the tube was over-temperature operating, the oxide layer will be oxidated by oxygen.

Abstract: A numerical study was conducted to understand the flame characteristics of ethylene under O₂/CO₂ atmosphere by detailed chemical kinetic models. Special interest is focused on the effects of CO₂ on flame propagation velocity and ignition delay. A modified reaction mechanism was established, and the ability of the reaction scheme was evaluated through comparison with well-defined laboratory data in the literature. A key result of the study is that the flame temperature and flame speed are significantly reduced because of the chemical and thermal effects of CO₂. The most important reactions as well as the dominant reaction steps under both O₂/CO₂ atmosphere and air atmospheres were also studied. It can be concluded that although the main reaction paths of fuel oxidation under both atmospheres are quite similar, the most important elementary reactions are different from each other. Besides, the same reactions assume great importance for ignition under air atmosphere become less qualified under O₂/CO₂ atmosphere.

Abstract: This template analyzed the refrigerator condenser copper tube TP2 corrosion failure reason and compared the corrosion resistant performance of copper tube TP2, brass tube HSn70-1 and Cu-Ni tube B10. Copper tube corrosion is mainly caused by high concentrations of chloride, dirt and water scouring accelerated the corrosion process. The corrosion resistant performance of three copper tube is close to and unsuitable for the cooling water of the high salt content. A better corrosion resistance of stainless steel tube should be used as the replacement and needs to keep the purity of the heat exchange tube. For cooling water which easily causes fouling, the inside tubes should be smooth.

Abstract: PANI coating was electrochemically synthesized by cyclic voltammetry (CV) method on the surface of 316L stainless steel plate. The surface morphology of PANI coating was observed by scanning electron microscopy. The effect of oxygen gas on corrosion behavior of PANI coating in PEMFC environment was investigated. The corrosion performance of the coating was evaluated by potential-time curve and polarization curve as well as electrochemical impedance spectroscopy in a bath containing 1M H₂SO₄ and 2ppM NaF, and the air with a flow rate of 10 ml/min was piped into the testing corrosion cell to simulate the positive cathode condition of PEMFC at 70°C. The potential-time curves illustrated that oxygen gas resulted in the potential decline towards negative direction. Polarization curves showed that corrosion potential of the sample with O₂ was lower than that of the sample without O₂, and the corrosion current density was higher than that of the sample without O₂. EIS results indicated that the Nyquist plots were constitute of a capacitive impedance arc and a incline line, and the oxygen gas reduced the anti-corrosion performance of the PANI coating.