互通多孔碳/二氧化锰纳米复合材料的原位水热合成及电化学性能

以互通多孔碳（IPC）为载体，水热条件下在碳表面原位反应生成纳米结构的二氧化锰（MnO₂），制备互通多孔碳/二氧化锰纳米（IPC/MnO₂）复合电极材料. 采用扫描电镜（SEM），透射电镜（TEM），X射线衍射（XRD），热重分析（TGA）对其结构进行表征；采用循环伏安法、恒流充放电和交流阻抗对其电化学性能进行研究. 结果表明：生成的MnO₂均匀地负载在碳的表面，形成多层次结构，并且随着温度的升高IPC表面负载的MnO₂由纳米颗粒变为纳米片状结构；MnO₂纳米片具有典型的K-Birnessite 型晶体结构；复合物中MnO₂的含量约为34%（w）. 在100 ℃制备的IPC/MnO₂复合材料在三电极系统中最高比电容达到了411 F·g^-1；随着反应温度的升高,比容量先增长后基本保持不变. 以IPC/MnO₂为正极，活性炭（AC）为负极，1 mol·L^-1 Na₂SO₄溶液为电解液组装成IPC/MnO₂//AC 混合超级电容器，发现IPC/MnO₂电极的电容器其电位窗口从1 V扩展到1.8 V，容量可达86F·g^-1，且表现出良好的电容特性和大电流放电性能.     

Novel Gel—like Process for Synthesizing Submicron LiaNi0.8Co0.2O2 Powders Used in Lithium Ion Batteries

A novel gel-like process has been developed for synthesizing LiaNi0.8Co0.2O2 powders,using citric acid as a chelating agent. This process improves the homogeneity of constituent cation and enhances their reactivity in the obtained precursor. The results of electrochemical test demonstrated that these materials exhibited excellent electrochemical properties. Its initial capacity reached 181.6 mAh/g and reversible efficiency at the first cycle is about 88.6%.     

Electrochemical characterization of solid materials in volume range I. Chemical effects on the matrix-phase separation

The electrochemical phase isolation (EPI) is described as a preparation method for determining specific precipitations in solid materials in microamounts and microdimensions. Fundamental criteria are examined as a function of the main parameter (polarization current) on the system Fe₃C in a Fe-matrix. The influence of the electrolyte composition on the electrochemical behaviour of the matrix, on the one hand, and of the phase, on the other hand, are investigated and utilized.     

二芳基乙烯类光致变色材料的合成概述

由于具有多种潜在的应用价值, 光致变色化合物作为高级功能材料的研究在国内外广受关注. 在众多的有机光致变色化合物中, 二芳基乙烯特别是二噻吩乙烯, 由于其具有良好的热稳定性和优良的耐疲劳度而成为这类化合物的杰出代表. 近年来, 有关二芳基乙烯类光致变色化合物的各种合成及性能方面的报道已涉及到信息存储、分子开关、逻辑电路、液晶显示、磁性材料等众多领域. 主要是从有机合成的角度, 对这类材料的合成进行了较为全面的概括, 对各种合成方法分别加以介绍和分析, 对其发展趋势予以探索和展望.     

Selenium in electrolytic manganese as a reference material for the quality control of aluminium melts

Electrolytic manganese is an important alloying element for aluminium and steel melts. It is mainly added to melts of aluminium in the holding furnace as tablets or minitablets (compressed compacts of manganese and aluminium powders). Selenium derivates are usually added during the production of electrolytic manganese, so some selenium is present in the alloys produced when electrolytic manganese is added to the aluminium furnace. Since the selenium contents of many alloys are of concern from health and environmental perspectives, their values should be provided. In this work, a laboratory reference material (LRM) based on electrolytic manganese was produced to assure our routine quality control method, where selenium is analysed by hydride generation followed by optical emission spectrometry with inductively coupled plasma (HG–ICP–OES). Therefore, the present paper describes in detail the preparation procedure for and the results from homogeneity and stability studies performed on electrolytic manganese LRM. For this purpose, a commercial electrolytic manganese lot was selected and the main factors involved in the preparation of the material (pretreatment step, homogenization, bottling and storage) were carefully studied and established in order to guarantee the long-term stability of the LRM. The results obtained showed that the LRM developed was a fit-for-purpose material for the quality control of the routine analysis of selenium.     

Effects of Total Thermal Balance on the Thermal Energy Absorbed or Released by a High-Temperature Phase Change Material

Front tracking and enthalpy methods used to study phase change processes are based on a local thermal energy balance at the liquid–solid interface where mass accommodation methods are also used to account for the density change during the phase transition. Recently, it has been shown that a local thermal balance at the interface does not reproduce the thermodynamic equilibrium in adiabatic systems. Total thermal balance through the entire liquid–solid system can predict the correct thermodynamic equilibrium values of melted (solidified) mass, system size, and interface position. In this work, total thermal balance is applied to systems with isothermal–adiabatic boundary conditions to estimate the sensible and latent heat stored (released) by KNO3 and KNO3/NaNO3 salts which are used as high-temperature phase change materials. Relative percent differences between the solutions obtained with a local thermal balance at the interface and a total thermal balance for the thermal energy absorbed or released by high-temperature phase change materials are obtained. According to the total thermal balance proposed, a correction to the liquid–solid interface dynamics is introduced, which accounts for an extra amount of energy absorbed or released during the phase transition. It is shown that melting or solidification rates are modified by using a total thermal balance through the entire system. Finally, the numerical and semi-analytical methods illustrate that volume changes and the fraction of melted (solidified) solid (liquid) estimated through a local thermal balance at the interface are not invariant in adiabatic systems. The invariance of numerical and semi-analytical solutions in adiabatic systems is significantly improved through the proposed model.     

聚1-氨基蒽醌在二次锂电池正极材料中的应用

采用化学方法合成聚1-氨基蒽醌并用于二次锂电池正极材料,通过红外光谱、扫描电镜、粒度测试、循环伏安以及充放电测试等方法对材料的官能团结构、微观形貌、颗粒大小以及电化学性能等进行了研究与分析.实验表明,与金属锂组成二次锂电池后,聚1-氨基蒽醌达到了218.3 mAh•g－1的首次放电容量,经过25次循环后仍可保持较高的充放电效率.由于材料具有较高的能量密度且不含对环境有污染的元素S,因此是二次锂电池非常有希望的正极材料.     

有机元素微量分析标准物质——茴香酸的研制

茴香酸的分子式为C_8H_8O_3,碳含量63.15%、氢含量5.30%、氧含量31.55%、甲氧基含量20.40%。该标样与日本元素分析恳谈会委员会、英国化学协会微量化学委员会所公布的微量化学标样之一——香草醛一样,都具有相同的碳、氢、氧和甲氧基含量,美国国家标准局(NBS)发行SRM142茴香酸作为微量分析中甲氧基的分析标样。     

Mechanical properties decay and morphological behaviour of biodegradable films for agricultural mulching in real scale experiment

The use of plastic materials in agriculture causes the serious drawback of huge quantities of waste. The introduction of biodegradable materials, which can be disposed directly into the soil, can be one possible solution to this problem. Biodegradable materials are actually innovative materials; therefore, their physical properties must be evaluated in relation to their functionality during the use in field. In the present research results of experimental tests carried out on biodegradable films used in strawberries protected cultivation are presented. The decay of some relevant physical parameters of biodegradable films during the cultivation period was monitored by laboratory tests (SEM analysis, mechanical tensile tests and infrared reflectance spectroscopy). Infrared spectroscopy clearly indicated that the mechanical degradation starts from the starch component of the material. Tensile tests showed that the value of elongation at break of biodegradable materials decreased in some cases by 300% after 10 days of field application.     

Ground-state energy of a quantum chain with competing interactions

We show rigorously that the ground state of a quantum chain with competing ferromagnetic nearest and antiferromagnetic next nearest interactions undergoes a transition from ferromagnetic to helical type, in the isotropic case, for a certain value of the relevant ratio of coupling constants. Boundaries of the phase diagram are also determined in the anisotropic case. The stability of a special quantum state (corresponding to a classical modulated phase of =/3) is analyzed by an extension of Holstein-Primakoff arguments, along a line of constant ratio of couplings, showing in particular a sequence of (instability) gaps. Finally, a natural adaptation of a variational wave function due to Huse and Elser is used to study several portions of the phase diagram, with very good agreement with previous theoretical results.