Preparation and characterization of partially substituted LiMyMn2−yO4 (M=Ni, Co, Fe) spinel cathodes for Li-ion batteries

The electrochemical and thermal behaviors of the spinels-LiMn₂O₄, LiCo_1/6Mn_11/6O₄, LiFe_1/6Mn_11/6O₄, and LiNi_1/6Mn_11/6O₄ were studied using electrochemical and thermochemical techniques. The electrochemical techniques included cyclic voltammetry, charge-discharge cycling of 2016 coin cells and diffusion coefficient measurements using Galvanostatic Intermittent Titration Technique. Better capacity retention was observed for the substituted spinels (0.11% loss per cycle for LiCo_1/6Mn_11/6O₄; 0.3% loss per cycle for LiFe_1/6Mn_11/6O₄; and 0.2% loss per cycle for LiNi_1/6Mn_11/6O₄) than for the lithium manganese dioxide spinel (1.6% loss per cycle for first ten cycles, 0.9% loss per cycle for 33 cycles) during 33 cycles. The Differential Scanning Calorimetry results showed that the cobalt substituted spinel has better thermal stability than the lithium manganese oxide and other substituted spinels.     

Living polymerization of several substituted acetylenes by CpMoCl4-based catalysts

[(o-Trifluoromethyl)phenyl]acetylene polymerized in a living fashion in the presence of CpMoCl₄-cocatalyst-EtOH catalysts (Cp: cyclopentadienyl; cocatalyst: EtMgBr, Et₃Al, n-BuLi). The CpMoCl₄-EtMgBr-EtOH (1:2:2) catalyst was particularly effective, with which the M_w/M_n of the formed polymer and the initiation efficiency, [P^∗]/[Cat], were 1.06 and 7.6%, respectively. Further, [P^∗]/[Cat] increased up to 10-13% at low temperatures (e.g. 0 °C) of catalyst aging and monomer addition. [(o-Trimethylsilyl)phenyl]acetylene also provided polymer having narrow molecular weight distributions with CpMoCl₄-EtMgBr-EtOH (1:2:2). CpMoCl₄ was more stable to air and moisture than MoOCl₄ owing to the steric and electronic effects of the Cp ligand, while the activity of the CpMoCl₄-based catalysts were lower than that of the MoOCl₄-based counterparts.     

Dense La0.9Sr0.1Ga0.8Mg0.2O2.85 electrolyte for IT-SOFC's: Sintering study and electrochemical characterization

This paper presents the sintering behaviour of a La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 coral-like microstructure powder. This is prepared by a successive freeze-drying and self-ignition process followed by calcination at 1200 °C during 1 h. This synthesis method gives great uniformity of the powder and allows shaping into compacts without requiring a grinding step. The grain size distribution (between 0.5 and 4 μm) favours a good sintering behaviour: open porosity disappear at 1400 °C and relative densities over 99% can be achieved after 6 h at 1450 °C. The same powder can also be sintered into a thin disc of ∼100 μm thickness. The characterization of the dense material by impedance spectroscopy shows that the activation energies below and above 600 °C are 1.0 eV and 0.7 eV, respectively. The conductivity at 800 °C is ∼0.11 S cm⁻¹. Special attention is devoted to the temperature range between 200 °C and 400 °C, where the intragrain and intergrain contributions can be distinguished. The analysis of the parameters describing the intragrain constant phase element in the equivalent circuit suggests that, above 325 °C, the system evolves from a distribution of relaxation time to only one relaxation time. The analysis of the data by the complexes permittivity show that ionic oxide conduction mechanism would occur in two steps. In the first, an oxygen vacancy would be released and, in the second, the migration of the ionic oxide would take place in the material.     

聚苯乙烯负载茂钛族催化剂的合成及制备反应过程的研究

采用悬浮法和溶液法将带有不饱和双键的金属茂钛族化合物与苯乙烯、二乙烯基进行共聚,分别合成了以聚苯乙烯为载体的键联型负载茂钛族催化剂。茂锆化合物比藏钛化合物容易与苯乙烯、二乙烯基苯共聚。同时,对加入金属茂钛族化合物的苯乙烯自由基聚合动力学用重量分析法进行了详细地研究,结果表明茂金属化合物不仅对ＡＩＢＮ的分解反应有促进作用,而且对苯乙烯自由基聚合的链反式反应也有催化作用,茂钛化合物的催化作用比茂锆化合     

取代苯氧乙酸二乙氨基乙醇酯的合成、表征及生物活性

以取代苯酚为原料亲核取代制得取代苯氧乙酸,采用硅胶负载四氯化锡为催化剂,二甲苯为溶剂,与二乙氨基乙醇发生酯化反应合成了6个苯氧乙酸二乙氨基乙醇酯衍生物。利用IR、1HNMR、13CNMR和MS对其结构进行了表征。初步的活性测试表明:与2,4-D(2,4-二氯苯氧乙酸)相比,大多数目标化合物均可促进玉米幼苗生长,提高玉米幼苗的硝酸还原酶活性,其中2-溴苯氧乙酸二乙氨基乙酯的处理质量浓度为20 mg/L时玉米幼苗硝酸还原酶活性最高。     

ENZYMATIC PROCESSING OF CRUDE XYLOOLIGOMER SOLUTIONS OBTAINED BY AUTOHYDROLYSIS OF EUCALYPTUS WOOD

ABSTRACT

Liquors from the aqueous processing of Eucalyptus wood, containing soluble xylan-degradation products (mainly substituted xylooligomers) were subjected to the action of commercial enzyme complexes (Celluclast, Bioxilanasa-AXC, Econase^R HC 400, Cellulase T 4 and Hemicellulase 90) containing endo-xylanase, xylobiase and acetyl-xylan-esterase activities to assess their suitability to obtain either xylose-containing solutions (useful as fermentation media) or low-DP xylooligosaccharides (useful as food additives). Under selected conditions, the Celluclast, Bioxilanasa-AXC, Econase^R HC 400 and Cellulase T 4 complexes were able to convert into xylose up to 90% of the substituted xylooligosaccharides present in the autohydrolysis liquors. The enzyme Hemicellulase 90 allowed the conversion of up to 67% of the initial substituted xylooligosaccharides into low-DP oligosaccharides. The most remarkable finding was that a significant concentration of DP2 oligomers (that could be incorporated into functional foods as prebiotic ingredients) was achieved at a short reaction time.     

基于自然原子轨道电荷的取代苯甲酸pK_a值预测

采用密度泛函理论(DFT)和B3LYP/3-21+G(d)基组,优化了21种单取代苯甲酸分子结构,发现羧基上氧原子的自然原子轨道电荷(NBO-O)值与其实验pKa值之间存在良好的线性关系(R=-0.973 6),比其原子核静电势电荷(ESP-O)值拟合的要好。计算了20种典型未知pKa值的单和多取代苯甲酸化合物的NBO参数,代入拟合出的优势线性参数方程,发现其预测值与流行软件ACD Lab 6.0预测得到的单和多取代苯甲酸的pKa值非常接近,最大偏差ΔpKa小于±0.03,且新方法可以估测到pKa值小数点后3位数。     

A new cleaning methodology for efficient Au-SAM removal

The desorption of a self-assembled monolayer (SAM) of 11-amino-1-undecanethiol (AUT) formed on an Au polycrystalline electrode was investigated with the purpose of establishing the most efficient method for SAM removal prior to electrode re-use. The cleanliness of the surface was evaluated by assessing the characteristics (and their reproducibility) of a newly prepared SAM (on a freshly cleaned electrode) in the presence of Ru(NH₃)₆^3+/2+ probe species. The simple flame annealing of the modified electrodes showed poor reproducibility. Later, cleaning treatments based on previous reports about the electrochemical desorption of SAMs, were investigated in NaOH, HClO₄, and KCl solutions. The anodic removal in alkaline and chloride solutions was not efficient enough due to the effect of the Au surface oxidation and dissolution. The commonly used reductive desorption in alkaline solution did also not offer a high efficiency (in contrast with the behavior described in those reports) probably due to the low stability of the thiolate molecules at high-pH values. In addition, such procedures did not provide a way to visualize the evolution of the process. The oxidative desorption in perchloric acid showed a higher efficiency at each single desorption cycle, and allowed to monitor the extension of the removal by comparing the cyclic voltammograms obtained in that medium with the expected fingerprint for the bare Au. However the voltammetric characterization of new AUT films, prepared on such electrochemically treated surfaces by re-incubation in the AUT solution, showed that the conditions of substrate cleanliness and smoothness necessaries to reproduce a close-packed and compact AUT monolayer were not reached. A new cleaning strategy based on the coupled use of oxidative removal in HClO₄ 0.1 M and flame annealing showed to be efficient and reproducible, providing the proper substrate precursors for the formation of highly ordered AUT films. The results also showed that the methodology works well in the removal of other SAMs like the one formed by the neutral 1-dodecanethiol (1-DT).     

利用直井产能计算分支水平井产能的方法

本文计算方法可用于油藏多分支水平井开发的早期评价。     

Benzophenone-1,3-dioxane as a free radial initiator for photopolymerization

Benzophenone-1,3-dioxane (BP-DO), a hydrogen abstraction type photoinitiator for free radical polymerization, is synthesized and characterized. Its capability for acting as an initiator for the polymerization of methyl methacrylate (MMA), styrene (St) and multifunctional monomers is examined. The relative photopolymerization efficiencies of BP-DO, benzophenone (BP), and BP/ethyl-4-dimethylaminobenzoate (EDAB) are compared. The amounts of leachable photoinitiator are determined through the extraction experiments. In contrast to BP-based photoinitiators, BP-DO does not require an additional hydrogen donor for the initiation; it could be a substitute for the conventional initiator systems of BP and BP/EDAB.