TURNING-POINT CONVERGENCE-ZONES IN THE DEEP SEA WITH NEGATIVE VELOCITY GRADIENT

An experimental result of the convergence-zone in the deep sea is presented.The result showsthat under the condition of negative velocity gradient the turning-point convergence-zones can beformed by the sounds reflected back from the sea bottom.For the source-and receiver-depth of100 m and the frequency of 200 Hz,the gains of the first three convergence-zones are about 14 dB.Calculated gain and positions of the convergence-zones are consistent with experiment.     

V2O3纳米粉末的固相反应合成(英)

Vanadium sesquioxide (V₂O₃) nanopowder was successfully prepared by the solid phase reaction of the mixture of vanadyl hydroxide (VO(OH)₂) and ammonium chloride (NH₄Cl) at 500 ℃. The as-obtained samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). V₂O₃ nanoparticles were well dispersed and displayed sphere-like particles with diameters in the range of 30～50 nm.     

库仑分析技术及其应用

库仑分析以它特有的优点,已经发展成为电化学分析中的一个重要分支,广泛地应用于冶金、地质、环保、医学及化工生产中,而且已经出现了许多专著和评论,详尽地讨论了它的理论和实践的各个方面。这方面的研究仍在不断深入。例如新的终点指示方法的研究,电生滴定剂的途径,小电解池的设计及化学条件的改进和应用范围的扩大,均使库仑分析方法不断衍生一些新的技术,这些新技术具有更好的灵敏度、准确度和更快的分析速度。本文拟就库仑分析的一些新技术作一简单介绍。本文公式中所列均为通用符号。1.亚化学计量库仑法(A SubstoichiometricCoulometric Method of Analysis)除了惯常的库仑分析方法以外,这是使用最广的一种库仑分析法。该法由Атасян于1968年提出,是一种电流扰动技术。该法是将被测定离子的一小部分借恒电流沉积在固体或液体电极上,然后反向恒电流溶解之,在溶解过程中,记录工作电极电势对时间     

计时库仑法研究——报导1用计时库仑法测定钌

钌的价态、存在形式较复杂,给电分析测定带来许多困难,库仑分析虽有一些报导,但不够理想,计时库仑法具有恒电势库仑法的优点,又省时间。本文研究了在1NH_2SO_4底液中,将不同价态的钌用硼氢化钠还原为三价,于+0.85V(对饱和甘汞电极),在铂网电极上计时氧化为四价,10~(-3)～10～(-6)M的钌,固定时间20.0秒,所得电量与浓度间线性关系良好。对10~(-6)M的钌的测定结果误差在10％以下,多数贵金属和某些贱金属不干扰测定。样品     

ZrO_2酸碱性质的TPD表征Ⅰ.单组分吸附研究

以NH3、吡啶、Et3N、CO2和苯酚为探针，用TPD－MS方法对ZrO2催化剂的酸碱性质进行了表征．ZrO2上碱性探针（NH3、吡啶和Et3N）的脱附温度远低于在强酸性SiO2－Al2O3上；而酸性探针CO2的脱附温度远低于在强碱性MgO上的结果．为ZrO2的弱酸弱碱性质提供了证明．NH3吸附IR结果表明ZrO2表面配位不饱合Zr4＋为酸（Lewis酸）中心．NH3、吡啶和Et3N与这些酸中心作用的方式和能量分布相似．NH3和CO2的TPD谱图均存在三个脱附峰，且相应脱附峰的温度范围相近．表明ZrO2的酸中心和碱中心具有匹配相当的酸、碱强度，ZrO2为典型的酸－碱双功能催化剂，在苯酚的TPD过程中，ZrO2的特征表现为对苯酚的强吸附和对苯酚分解的高活性．文中结合IR结果，对与NH3和CO2的脱附相联系的表面吸附物种分别进行了讨论．     

Study of the Electroless Silver Seed Formation on Silicon Surface

The silver seed on silicon was prepared through aqueous I-IF and AgNO3 solution at room temperature. In order to explore the formation process of silver seed on silicon, the methods of open circuit potential with time （OCP-t）, anodic stripping sweep voltammetry （ASV） and scanning tunneling microscope （STM） were used in this work. The procedure of silver nucleus growing into large particles was explained by electro-negativity. The growth mechanism of silver seed on silicon has been presented： at first, the silver monolayer and multilayer firstly grows onto silicon without fully covering the surface at the expense of silicon etching due to the silver seed attracting the electron from silicon, after that, the monolayer coalesces together, forming continuous grain film with some silver atoms diffusing into the silicon and the multilayer still grows thick simultaneously.     

亚钛还原-电生钒(V)库仑滴定铀

库仑滴定法测铀,有很多方法,但因铁及其他变价元素的干扰和灵敏度不高而受到限制。Goldbeck用亚铁还原六价铀为四价,过量亚铁用硝酸除去,得到的U~(4+)再电生V~(5+)库仓滴定之,最低测定了80毫克铀。我们在重复该工作时发现,由于亚铁还原铀产生的大量铁盐控制了溶液的电位,使滴定的突跃范围大大缩小、因而无法再提高灵敏度;同时,亚铁对少量UO_2~(2+)的还原,以及用硝酸除去过量亚铁均不十分可靠,因而准确度也比较差。容量法的工作表明,亚钛还原铀(Ⅵ),再用钒酸盐滴定比亚铁还原法优越。     

人造卫星固体润滑轴承的性能试验结果

一、前言 为了防止超高真空宇宙环境中造成润滑油蒸汽成分的污染,人们正在研究和利用固体润滑剂。 以1981年2月11日发射的Ⅳ型技术试验卫星(ETS—Ⅳ)为例,其搭载试验设备——扫描型地球传感器(HOST)的旋转机构采用的就是固体润滑。这种地球传感器虽然是作为三轴姿态控制用姿态检测装置研制的,但考虑到是在自旋卫星上进行搭载,故将其旋转头的功能按照旋转的和不旋转的两     

碳糊电极萃取溶出伏安行为及电化学测定维生素E

提出了一种利用碳糊电极测定维生素E的方法。用硝酸作氧化剂,将非电活性的维生素E转化为具有电活性的醌型化合物 生育酚红,研究了生育酚红在特制碳糊电极上的萃取伏安行为和电极反应机理。在1.2mol·L-1HNO3 89%的乙醇介质中,维生素E在电极上开路吸附、萃取预富集后,进行阳极溶出伏安测定,维生素E在3.00×10-5～9.88×10-4mol·L-1范围内峰电流与浓度呈线性关系,检出限为6×10-6mol·L-1,将此法应用于维生素E药品的分析中。     

Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (/-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be