Characterizing herring bone structures in carbon nanofibers using selected area electron diffraction and dark field transmission electron microscopy

The use of selected area electron diffraction and centered dark field imaging using a transmission electron microscope is demonstrated for studying the herringbone structure of carbon nanofibers (CNFs). The experimental method is described and illustrated with CNFs that were grown via a chemical vapor deposition method with a nickel catalyst. It is demonstrated that this method gives the angle of the herringbone with great accuracy and gives insight into the uniformity of graphitic elements in the herringbone structure. It was found that the Ni catalyst could be removed from the fiber-tips by treatment in HNO₃, without affecting the carbon structure. These electron microscopy results were confirmed by XRD. The parameters that can be determined by application of this characterization method are expected to be useful to study and optimize growth conditions for carbon nanofibers grown by chemical vapor deposition.     

铸铝合金在有机羧酸体系中电化学陶瓷成膜

利用电化学沉积陶瓷膜（EDCF）技术将铸铝ZL108合金置于有机羧酸复合体系，制得了具有较高硬度和良好外观的灰色类陶瓷膜。详细研究了各工艺参数对膜层性能的影响，结果表明，有机羧酸是主要成膜物质；金属硫酸盐是阳极反应的活化剂，但浓度过高会加快膜层溶解；方波脉冲电源有利于生成厚膜；峰值电流密度越大，成膜时间越短，但过大会使膜层减薄；溶液pH值、搅拌等对成膜过程有一定影响。     

Surface disposition and stability of pest-interactive,trichome-exuded diterpenes and sucrose esters of tobacco

The precise physical location of trichome-exudate biochemicals on the plant surface is undoubtedly important in plant-pest interactions, perhaps particularly those involving fungal and bacterial pathogens that invade the plant through the epidermal layer. The chemical stability of exuded compounds is also important in this regard. Here we have studied these two aspects of trichome biology using the highly exuded tobacco line,Nicotiana tabacum, T.I. 1068. Particularly under high relative humidity growth conditions, sucrose esters (SE) were found to migrate from the exudate droplet around the gland down the trichome stalk to the epidermal cells below. Six days after labeling leaf midveins on plants grown in a high humidity environment, 29 and 71% of label found in SE were recovered with trichome glands and below gland regions, respectively. Corresponding disposition in the moderate humidity environment was 40 and 60%, respectively. Migration of less polar duvatrienediols (DVT) was less marked. Staining of SE with rhodamine B showed the occurrence of more extensive and physically different migration in the high humidity versus moderate humidity case. Both SE and DVT were stable between six and 18 days postlabeling, the period encompassing the time of maximum exudate formation through the beginning of tissue senescence. Our results suggest that even under conditions that avoid mechanical disturbance of tissue, SE and DVT are chemically stable, at least until senescence, and appear to migrate from the gland region to the epidermal surface, apparently according to their relative polarity.     

Direct methanol alkaline fuel cells with catalysed anion exchange membrane electrodes

Membrane electrodes prepared by chemical deposition of platinum directly onto the anion exchange membrane electrolyte were tested in direct methanol alkaline fuel cells. Data on the cell voltage against current density performance and anode potentials are reported. The relatively low fuel cell performance was probably due to the low active surface area of Pt deposits on the membrane comparing to other membrane electrode assembly (MEA) fabrication methods. However, the catalysed membrane electrode showed good performance for oxygen reduction. A reduction in cell internal resistance was also obtained for the catalysed membrane electrode. By combining the catalysed membrane electrodes with a catalysed mesh, maximum current density of 98 mA cm^–2 and peak power density of 18 mW cm^–2 were achieved.     

Effect of adding nickel to iron-alumina catalysts on the morphology of as-grown carbon nanotubes

The synthesis of carbon nanotubes (CNTs) from ethylene decomposition by Fe/Al₂O₃ and Fe/Ni/Al₂O₃ catalysts (Fe:Ni=10:1) is studied. A small amount of nickel introduced into the catalyst can significantly increase the yield of CNTs, but the nanotubes change from straight tubes with concentric parallel carbon sheets to helical tubes of the fish-bone type. Raman characterization of CNTs prepared at 823 and 1023 K and CNTs annealed at 2473 K shows that CNTs deposited on the Fe/Ni/Al₂O₃ catalyst have poor crystallinity, as compared with that on the Fe/Al₂O₃ catalyst. These differences are explained by a mechanism of formation of helical tubes of the fish bone type that takes into consideration the differences in the chemical nature of the catalyst with and without nickel.     

Synthesis of nanodispersed oxides of vanadium, titanium, molybdenum, and tungsten on mesoporous silica using atomic layer deposition

The advantages of the atomic layer deposition (ALD) method for preparation of tungsten, vanadium, titanium, and molybdenum oxide catalyst supported on mesoporous silica are discussed, with emphasis on the importance of synthesis conditions on dispersion, structure and activity of the resulting materials. A suite of complementary techniques such as DRS-UV/Vis, BET, ¹H-NMR, XRD, and TEM were used to study the structural properties of the supported metal oxides, and probe reactions such as 2-butanol dehydration and ethanol partial oxidation were used to demonstrate the potential advantages of the ALD-prepared catalysts. Specifically, highly dispersed oxides of titanium, molybdenum, and tungsten oxide on mesoporous silica were synthesized using the ALD method. It is also demonstrated that attainment of high dispersions of vanadium oxide on mesoporous silica requires the presence of at least a single layer of titanium oxide due to the well-known poor interaction between vanadia and silica. The highly dispersed catalysts prepared here by ALD methods exhibited superior catalytic performance relative to those prepared using conventional incipient wetness impregnation.     

Adsorption of mercaptopropionic acid onto Au(1 1 1): Part II. Effect on copper electrodeposition

Copper deposition in the presence of an organic additive (3-mercaptopropionic acid, MPA) was studied by cyclic voltammetry and in situ scanning tunneling microscopy (STM) and the results are compared to those for additive-free solutions. It is shown that underpotential deposition (upd) of copper onto a fully MPA-covered electrode produces a defect-rich substrate, but the defects are blocked by the dense organic film for bulk deposition, resulting in a low number of nuclei. A grain-refining effect of MPA, however, was found, when Cu deposition was initiated shortly after addition of MPA to the solution, i.e., for a low-coverage MPA adlayer.     

Controllable fabrication of SnO2-coated multiwalled carbon nanotubes by chemical vapor deposition

A simple and efficient approach for coating multiwalled carbon nanotubes (MWCNTs) with size-controllable SnO₂ nanoparticles by chemical vapor deposition has been developed using tin hydride (SnH₄) gas as the source of SnO₂ at 550 °C. The size and coverage of SnO₂ nanoparticles can be adjusted by simply controlling the deposition time and the flow rate of the SnH₄/N₂ mixture gas during the CVD procedure. In addition, by using the MWCNTs as a sacrificial template, a kind of one-dimensional chain-like SnO₂ nanostructure has been synthesized by increasing the deposition temperature to 730 °C. This technique may provide a good way to produce tunable SnO₂-MWCNT composites.     

考虑大气沉降的湖库分区动态水环境容量精细解析

针对面源污染为主的湖库型流域,为建立水质目标管理与污染总量控制之间更精准的响应关系,借鉴日最大负荷总量模式,基于物质量平衡原理提出考虑径流丰枯变化、不均匀混合、大气沉降等影响因素的湖库分区动态水环境容量精细解析方法,包括污染混合区设置、代表水文系列确定、逐日分区水量水质计算。以沙河水库为例,分别以全湖Ⅱ类、主湖Ⅱ类作为水质管理目标,采用2010—2015年代表水文系列对总氮动态水环境容量进行精细解析。结果表明：全湖Ⅱ类、主湖Ⅱ类水质管理目标下沙河水库总氮水环境容量的多年均值分别为36.7 t和99.43 t,若不考虑湖滨混合区,全湖Ⅱ类水质目标下总氮的年水环境容量计算值偏大66.43%;实施水质目标管理的水域面积越大,大气沉降对水环境容量的影响越大;径流年际及年内丰枯变化对水环境容量的影响显著;各分区总氮控制总量占全流域总量的比例与面积比基本一致。湖库分区动态水环境容量精细解析可量化不同因素对水环境容量计算结果的影响,科学解析面源输入型湖库水环境容量的时空结构特征,实现水质目标管理与污染总量分区管控的有机联动,更好地支撑流域水环境的精细化管理。     

基于AERF模型的油井结蜡预测

油井结蜡是一种在开发以及开采油田时对油井正常产出造成了负面影响的现象,该现象会引起油流通道堵塞,导致油井开采过程中出油量降低.对油井结蜡状况做出智能预警,完成油井设备提前修复,对油田提高产能效率、降低维护成本及智能化管理有非常关键的价值.为了解决油井正常数据和结蜡数据严重不平衡问题,本文引入了自适应合成抽样法(ADASYN)和最近邻规则欠抽样法(ENN)两种非均衡样本处理方法,分别对类别为结蜡的样本和非结蜡的样本进行处理,最终使用随机森林算法对新构成的数据集训练,构造出AERF智能模型来预测油井结蜡.实验结果表明,提出的AERF模型在油井的结蜡数据集中预测效果更佳,明显地提高了预测精度.