In situ high-temperature scanning tunneling microscopy study of bilayer graphene growth on 6H-SiC(0001)

Using in situ high-temperature (1395 K), ultra-high vacuum, scanning tunneling microscopy (STM), we investigated the growth of bilayer graphene on 6H-SiC(0001). From the STM images, we measured areal coverages of SiC and graphene as a function of annealing time and found that graphene grows at the expense of SiC. Graphene domains were observed to grow, at comparable rates, at (I) graphene-free SiC step edges, (II) graphene-SiC interfaces, and (III) the existing graphene domain edges. Based upon our results, we suggest that the rate-limiting step controlling bilayer graphene growth is the desorption of Si from the substrate.     

制备方法对石墨烯电化学性能的影响

石墨烯处于当今电化学纳米材料研究的前沿,因制备方法多种多样,得到的石墨烯材料性能也存在相当大差异。综述了通过目前流行的制备方法获得的石墨烯的电化学性能研究成果,分析了制备方法间、制备条件间的不同对石墨烯电化学性能的影响。     

Determination of dopamine via amino-p-cyclodextrin/graphene/ferrocene composite film modified glassy carbon electrodes

利用制备的氨基-β-环糊精-石墨烯-二茂铁（β-CD-NH2/GNs/Fc）复合膜修饰电极,研究了多巴胺（DA）的电化学行为。结果表明,该复合膜修饰电极在pH值=7.00的磷酸盐缓冲溶液（PBS）中对DA有良好的电催化性能,DA的氧化峰电流在0.1～100μmol/L浓度范围内呈良好的线性关系,检出限为8.5×10-8mol/L。结果表明该修饰电极具有较高的检测灵敏度,可用于实际样品的检测。     

Application of Multi-walled Carbon Nanotubes/Nafion Composite Film in Electrochemical Determination of Pb2+

In this work, insoluble multi-walled carbon nanotubes (MWNTs) was dispersed into ethanol in the presence of 1% Nafion, resulting in a stable and well-distributed MWNTs/Nafion suspension characterized by TEM and particle size analyzer. After evaporation of ethanol, a uniform MWNTs/Nafion composite film-coated glassy carbon electrode (GCE) was prepared and then characterized with SEM. Furthermore, the electrochemical behavior of Pb²⁺ at the unmodified GCE, Nafion film-modified GCE and MWNTs/Nafion film-modified GCE was investigated. It was found that the reduction peak potential shifts positively and peak current remarkably increases at the MWNTs/Nafion film-modified GCE, suggesting that MWMTs/Nafion film-modified GCE exhibits catalytic ability to electrochemical reduction of Pb²⁺. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of Pb²⁺. Finally, the MWMTs/Nafion film-modified GCE was successfully used to detect Pb²⁺ in a water sample.     

Thermo-mechanical properties of Indian and other granites

The knowledge of thermo-mechanical and transport properties of granites is required to understand and model a number of processes in the earth crust such as folding, geothermal activity, magmatic intrusions, plate tectonics and nuclear waste disposal. Authors have studied various thermo-mechanical properties of Indian granite (IG) at high temperatures in the range of 30–160 °C, keeping in view the highest temperatures expected in underground nuclear waste repositories. These properties are Young's modulus, uniaxial compressive strength, tensile strength, Poisson's ratio, coefficient of linear thermal expansion, creep behaviour and the development of micro-crack on heating using scanning electron microscope (SEM). In addition, a literature survey was carried out to collect data on the properties of granites at high temperatures including first five properties mentioned above for IG and some other properties such as viscosity, permeability, melting point, specific heat, thermal conductivity and thermal diffusivity. The information gathered in this paper would be useful in thermo-mechanical characterisation of granites for modelling of several geological phenomena.     

炉渣中氧离子迁移的电化学模型

对渣相中氧离子迁移的电化学进行研究，提出具有电化学特征的渣相氧离子流动力学模型，此模型能较为全面地解释各种反应现象，实验数据与模型计算的对比，证明所提出的反应机制的正确性。     

Ambipolar and multi‐electrochromic polyimides based on N,N‐di(4‐aminophenyl)‐N′,N′‐diphenyl‐4,4′‐oxydianiline

A series of novel aromatic polyimides were synthesized from N,N‐di(4‐aminophenyl)‐N′,N′‐diphenyl‐4,4′‐oxydianiline and aromatic tetracarboxylic dianhydrides through a conventional two‐step procedure. Most of the polyimides exhibited reasonable solubility in organic solvents and could afford robust films via solution casting. The polyimides exhibited high thermal stability, with glass transition temperatures in the range 227–273 °C and 10% weight‐loss temperatures in excess of 550 °C. All the polyimide films showed ambipolar redox and multi‐electrochromic behaviors. They exhibited two reversible oxidation redox couples at 0.94–0.98 and 1.09–1.12 V versus Ag/AgCl in acetonitrile solution. A coupling reaction between the radical cations of the pendent triphenylamine units occurred during the oxidative process forming a tetraphenylbenzidine structure which resulted in an additional redox state and color change. © 2014 Society of Chemical Industry     

Mechanochemical Synthesis and Electrochemical Properties of LiMn2O4

Spinel LiMn₂O₄ as a cathode material for lithium secondary batteries has been synthesized by a mechanochemical process, and its electrochemical properties have been characterized. Highly disordered nanocrystalline LiMn₂O₄ powders have been prepared by the mechanochemical processing of Li₂O and MnO₂ powder mixtures for 24 h. Electrochemical characterization of mechanochemically processed powder has shown that the intercalation of Li⁺ takes place with an initial capacity of 167 mA·h/g in the 2.5–4.3 V range and has better capacity retention as compared to the well-ordered crystalline LiMn₂O₄ powders. The better capacity retention of the mechanochemically processed LiMn₂O₄ powder may be attributed to the highly disordered structure that could accommodate the Jahn–Teller distortion of the spinel structure during Li⁺ intercalation around the 3 V region.     

氧化亚铁硫杆菌浸矿体系中黄铁矿的电化学行为(英文)

运用循环伏安、稳态极化扫描和交流阻抗等电化学测试方法,研究黄铁矿在氧化亚铁硫杆菌浸矿体系和无菌酸性体系下的电化学氧化机理。结果表明,在无菌和A.ferrooxidans菌存在的条件下,黄铁矿的氧化反应分为两步:第一步是黄铁矿氧化生成元素S;第二步是元素S被氧化生成SO42-。加入A.ferrooxidans后黄铁矿的氧化机理没有发生改变,但是氧化速度加快。随着黄铁矿与A.ferrooxidans作用时间的延长,极化电流密度增加,黄铁矿表面钝化膜溶解的点蚀电位降低。在细菌存在的条件下,电极的阻抗值下降,表明微生物的存在加速了黄铁矿电极的腐蚀作用,有利于黄铁矿的氧化溶解。     

Ablation behavior and mechanism of SiC/Zr–Si–C multilayer coating for PIP-C/SiC composites under oxyacetylene torch flame

To improve the ablation resistance of PIP-C/SiC composites, SiC/Zr–Si–C multilayer coating was prepared by chemical vapor deposition (CVD) using methyltrichlorosilane (MTS) and hydrogen as the precursors and molten salt reaction using KCl–NaCl, sponge Zr and K₂ZrF₆, then the ablation capability of the coated composites was tested under oxyacetylene torch flame. The linear and mass ablation rates were much lower than those of uncoated samples. The linear and mass ablation rates of the three coating coated samples reached 0.0452 mm/s and 0.031 g/s, decreased by 27.3% and 27.1%, respectively. Moreover, the linear and mass ablation rates of the five coating coated samples reached 0.0255 mm/s and 0.0274 g/s, decreased by 59.0% and 35.5%. The gases released during ablation could take away a lot of heat, which was also helpful to the protection of the composites.