Investigation of the composition and properties of catalytic layers prepared by the ion beam-assisted deposition of tin and platinum on carbon supports

Catalytic layers are prepared by the vacuum ion-beam-assisted deposition of tin and platinum onto carbon-based AVCarb® Carbon Fiber Paper P50 and Toray Carbon Fiber Paper TGP-H-060 T supports to produce electrocatalysts for direct methanol and ethanol fuel cells with a polymer-membrane electrolyte. The layers are formed in the mode of ion-assisted deposition, wherein ions of the deposited metal are used as ions assisting deposition. Metal deposition is performed from a neutral vapor fraction, while mixing of the deposited layer with the substrate by accelerated ions of the same metal is carried out from the vacuum arc discharge plasma of a pulsed electric arc ion source. The morphology and composition of the layers is studied using scanning electron microscopy, electron probe microanalysis, X-ray fluorescence analysis, and Rutherford backscattering spectrometry. It is demonstrated by means of voltammetric measurements that the resulting electrocatalysts exhibit activity in the oxidation of methanol and ethanol.     

含氘电极真空弧等离子体空间分布特性诊断研究

真空弧放电等离子体含有多种离子成分,并且各离子在空间上具有不同的分布规律.本文针对金属氘化物电极真空弧离子源,搭建了一台紧凑型磁分析装置,用来研究放电等离子体中氘离子与金属离子的空间分布.当离子源弧流为100 A左右时,该装置能有效地传输引出束流,并且具有较好的二次电子抑制效果,可准确获得各离子流强.利用该装置测量并获得了氘化钛含氘电极真空弧放电等离子体内氘离子和钛离子空间分布规律,结果表明:径向上,氘离子和钛离子都呈高斯分布,但氘离子分布均匀,而钛离子相对集中在轴线附近,导致轴线附近氘离子比例最低;轴向上,所有离子数量都以自然指数函数减少,而且相对幅度接近,所以氘离子比例几乎不变.本文研究结果不仅有助于理解真空弧放电等离子体膨胀过程,还可以指导金属氘化物电极真空弧离子源及其引出设计.     

Surface composition and surface energy of Teflon treated by metal plasma immersion ion implantation

Plasma immersion ion implantation using a metal vacuum vapor arc (MEVVA) or cathodic arc source was used to modify the fluorine-based polymer, Teflon. Several transition metal ions such as Co, Ni, Cu were introduced into plasma and implanted into the Teflon surface. The chemical composition of the modified surface was determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The metals were found to be distributed several nanometers from the surface and XPS results showed the formation of metallic carbides and fluorides on the surface. Contact angle measurement results demonstrate the favorable change in the wettability from being hydrophobic to hydrophilic. Our study shows that the increase of the surface energy is due to the change of the surface interaction properties after metal plasma implantation.     

Charge state and residence time of metal ions generated from amicrosecond vacuum arc

Metal ions generated from a microsecond vacuum arc were measured using a time-of-flight (TOF) method. A point-plane vacuum gap was fired by an impulse voltage to generate metal ions. The risetime and time constant for the decay of the arc current were 0.1 and 4.5 μs, respectively. TOF ion currents were measured for variable ion extraction times after the arc ignition. At a lead cathode, Pb⁺ and Pb ⁺⁺ ions were detected for ion extraction times less than 45 μs. The average charge-state fractions of the Pb⁺ and Pb ⁺⁺ ions were 91 and 9%, respectively. At a copper cathode, Cu ⁺, Cu⁺⁺, and Cu⁺⁺⁺ ions were detected for ion-extraction times less than 12.5 μs, and the average charge-state fractions were 42, 41, and 17%, respectively. The residence times of the generated lead and copper ions were also discussed     

Evolution of Copper Vapor from the Cathode of a Diffuse Vacuum Arc

The metal-vapor evolution from the cathode of a diffuse vacuum arc is described by a model that starts from the expression for the collisionless expansion into vacuum of atoms originating from an instantaneous point source. The velocity distribution is assumed to be Maxwellian at the moment the atoms are released from the source. By convolution with the vapor generation rate, which is given by an effective erosion rate and the waveform of the arc current, this expression is generalized to yield the atomic density at an arbitrary distance from a point source which emits atoms for a finite period. The result is integrated over the cathode surface which is treated as an extended homogeneous source of vapor. The copper-vapor density was calculated for a vacuum arc driven by a sinusoidal 50-Hz current half-cycle of 500 A rms, for the center of the contact gap. With a vapor temperature of 2000 K and an effective copper-vapor erosion rate of 3 ?/C, the model well describes the measured decay of the copper-vapor density from about 5 × 1017 m-3 at 300 ?s before current-zero to 5 × 1014 m-3 at 400 ?s after current-zero. Comparison with calculations based on the assumption that metal vapor is generated predominantly by molten droplets evaporating in flight indicates that before current-zero the contribution of the droplets to the vapor density is negligibly small, while after current-zero both vapor generation mechanisms produce vapor at the same order of magnitude.     

The use of vacuum arc discharge as a load for XPG-1 high-current generator

It was attempted to use the vacuum arc discharge as a load of a high-current generator. The idea is as follows: metal vapor is injected using the vacuum arc discharge into a microgap of a load unit of the current generator. When the generator current flows over metal vapor, such a load begins to compress as in the classical Z pinch. During compression, Rayleigh—Taylor instabilities develop, which results in the formation of waists and hot spots. The hot spot radiation power can exceed the radiation power in the case of the X pinch used as a load by a factor of 1.5–2. The signal amplitude spread is significantly smaller than that when using the X pinch. The spectrum and sizes of the hot spot can be varied by selecting the mass and type of metal injected into the discharge region.     

Vacuum arc ion charge-state distributions

Vacuum arc ion charge-state spectra have been measured for a wide range of metallic cathode materials. The charge-state distributions were measured using a time-of-flight diagnostic to monitor the energetic ion beam produced by a metal vapor vacuum arc ion source. Data were obtained for 48 metallic cathode elements: Li, C, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn Fe, Co, Ni, Cu, Zn, Ge, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er Yb, Hf, Ta, W, Ir, Pt, Au Pb, Bi, Th, and U. The arc was operated in a pulsed mode with pulse length 0.25 ms: arc current was 100 A throughout. The measured distributions are cataloged and compared with earlier results. Some observations about the performance of the various elements as suitable vacuum arc cathode materials are also presented     

C+离子注入Si单晶形成SiC埋层中Si2p的特征能量损失谱

利用metal vapor vacuum arc离子源产生的C⁺离子，注入单晶Si衬底，得到了SiC埋层.利用X射线光电子能谱，研究了SiC埋层中Si2p的特征能量损失谱.结果表明：Si2p的特征能量损失谱依赖于SiC埋层中C原子的浓度分布，并且与SiC埋层的有序度对应. 关键词：     

Time-of-flight mass spectrometry studies of an ion beam generated by the titan source

The TITAN source generates wide-aperture beams of gas and metal ions of different materials. This is achieved because of two types of cold-cathode arc discharges, which operate simultaneously in the discharge system of the source. For metal ions to be obtained, use is made of the vacuum arc initiated between an ion-forming cathode and a hollow anode. To produce gas ions, a constricted low-pressure arc discharge is initiated with the same hollow anode. The constitution of ion beams generated by the TITAN source has been investigated using a homemade time-of-flight spectrometer. This paper describes the design of the latter and the principle of its operation, and discusses the physical peculiarities of the spectrometer operation, which affect the ion beam constitution. Institute of High Current Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 21–28, February, 2000.     

离子注入层的X射线光电子能谱分析

采用金属蒸汽真空弧（MEVVA）离子源发出的强束流脉冲钨离子,对H13钢进行了离子注入表面改性研究,借助X射线光电子能谱（XPS）考察了注入表面层中钨,氧,铁的化学状态,研究发现,钨离子注入层中钨元素以替位钨和三氧化钨形式存在,铁元素以金属铁和三氧化二铁形式出现,而且各价态元素的原子比随深度而变化。     

(Si,Er)双注入热氧化硅的光致发光

采用强流金属蒸汽真空弧（MEVVA）离子源注入机，先将Si大束流注入热氧化SiO2/单晶硅，直接形成镶嵌在SiO2中的纳米晶Si，再小束流注入Er。Er离子在掺杂层中的浓度可达10^21cm^-3量级，大大地提高了作为孤立发光中心的Er^3 浓度。在77K和室温下，观察到了Er^3 的1.54цm特征发射。     

Estimation of Post-Arc Neutral Vapor Density in the Gap Volume Generated by Evaporating Macroparticles in a Diffuse Vacuum Arc

This paper presents a mathematical model of calculations of the density of atoms evaporated from macroparticles in a diffuse vacuum arc. The influence of the initial temperature, diameter, and average velocity of the droplets, as well as the kind of the cathode metal on vapor density in the volume surrounding the electrodes was investigated. Both the initial density and the decay of vapor density were calculated for Cu and Cd electrodes following the extinction of the arc. The calculated densities constitute the basis for evaluating the influence of evaporating droplets on the development of electrical breakdown in a vacuum gap after arcing.     

Vacuum Arc Anode Phenomena

This paper presents a brief review of anode phenomena in vacuum arcs. It discusses in succession the transition of the arc into the anode spot mode; the temperature of the anode before, during, and after formation of an anode spot; and anode ions. Characteristically the anode spot has a temperature of the order of the atmospheric boiling point of the anode material and is a copious source of vapor and energetic ions. The dominant mechanism controlling the transition of the vacuum arc into the anode spot mode appears to depend upon the electrode geometry, the electrode material, and the current waveform of the particular vacuum arc being considered. Either magnetic constriction in the gap plasma or gross anode melting can trigger the transition, indeed a combination of the two is a common cause of anode spot formation.     

Influence of the anode material on an argon arc

The interaction between the arc and the anode was experimentally studied by means of a transferred arc burning in argon with copper, iron, or steel anodes. Depending on the rate of anode cooling, a stable plasma was obtained just above the anode, established either in pure argon (strong cooling) or in a mixture of argon with metal vapor. Temperature and metal concentration fields were deduced from spectroscopic measurements. Two important results were reached: the arc radius near the anode depends on the nature of the electrode, even without anode erosion; and the presence of metal vapor leads to a cooling of the plasma. The same arc configurations were theoretically simulated by a two-dimensional model. The comparison between experimental and numerical results allows a large proportion of the observed phenomena to be interpreted, in spite of partial discrepancies between predicted and measured values. The dimension of the arc root at the anode depends on the thermal conductivity of the solid metal, whereas the cooling effect due to metal vapor in the plasma is explained by the increases of electrical conductivity and of radiative losses in the presence of the vapor     

Au纳米颗粒和CdTe量子点复合体系发光增强和猝灭效应

利用金属蒸发真空多弧离子源注入机, 将Au离子注入到高纯石英玻璃来制备镶嵌有Au 纳米颗粒的衬底材料, 随后将化学方法合成的CdTe量子点旋涂在玻璃衬底上制备了Au纳米颗粒和CdTe量子点复合体系. 通过对镶嵌有Au纳米颗粒的衬底进行热退火处理来控制Au纳米颗粒的生长和分布, 系统研究了Au纳米颗粒的局域表面等离子体共振对CdTe量子点光致发光性能的影响. 利用光学吸收谱、原子力显微镜、透射电子显微镜和光致发光谱对样品进行了表征和测试. 光致发光谱表明, Au纳米颗粒的局域表面等离子体对CdTe量子点的发光有增强效应也有猝灭效应. 深入分析了Au纳米颗粒和CdTe量子点之间的相互作用过程, 提出了关于Au-CdTe 纳米复合体系中CdTe 发光增强和猝灭的新机理. 该实验结果为利用金属纳米颗粒表面等离子体技术制备高发光性能的光电子器件提供了较好的参考.     

The High Current Metal Vapor Arc Column between Separating Electrodes

We observed metal vapor arcs between separating electrodes in a demountable vacuum chamber using high speed photography. The peak values of the ac arc current half-wave ranged from 5 kA to 67 kA. Determination of the arc appearance as functions of arc current and electrode gap revealed that the arc can assume various types of columnar forms when the current at the instant of electrode separation exceeds 7 kA. The duration of the columnar arcing forms is influenced by axial magnetic fields differently for different field strengths. The graphical representation of the results allows prediction of the most probable arc appearance for a given set of operating parameters. A qualitative explanation of the various arc appearances on the basis of balances between magnetic and kinetic pressures is provided.     

铒掺杂富硅热化SiO2／Si发光薄膜的显微结构

利用金属蒸气真空弧(MEVVA)离子源将稀土元素Er离子掺杂到富硅热氧化SiO2/Si薄膜中.卢瑟福背散射(RBS)和X-射线电子能谱仪(XPS)分析表明,Er浓度可达原子百分数(x)～10,即Er的原子体浓度为～1021·     

离子束合成钇硅化物的结构及红外谱特征

将稀土金属钇离子注入到n型单晶Si(111)中制备出钇硅化物埋层.利用x射线衍射、卢瑟福背散射和傅里叶红外吸收谱测量分析了样品的结构、原子的埋层分布和振动模式.结果表明，Y离子在注入过程中已与基底中的Si原子形成了YSi2结构相.真空下的红外光辐照处理促使YSi2择优取向生长，埋层中Si与Y的平均原子浓度比由24下降为20，与六方YSi2的化学计量比一致.还给出了钇硅化物的特征红外吸收谱.     

Charge-state distribution of ions in a vacuum arc discharge plasma in a high magnetic field

It is shown that the fraction of multiply charged metal ions generated in a vacuum arc discharge plasma grows substantially in a high magnetic field. This effect was observed for more than 30 different cathode materials. A relation is established between growth of the mean charge of the ions and increases in the burning voltage of the arc. It is demonstrated that the burning voltage of the vacuum arc can be ultimately increased to 160 V. Zh. Tekh. Fiz. 68, 39–43 (May 1998)     

用掩蔽注入法研究钛注入H13钢的耐磨性

采用由金属蒸汽真空弧离子源引出的强束流钛、碳离子对H13钢进行表面改性研究.钛和碳离子注入剂量分别为3×1017和1×1017cm-2,引出电压分别为48和30kV，平均束流密度分别为47和20μA·cm-2.为了保持相同的摩擦磨损实验条件，注 入过程中采用掩蔽注入技术.摩擦磨损实验结果表明，钛离子注入H13钢提高了其耐磨性，并大幅度降低其摩擦系数.利用卢瑟福背散射谱测量了离子注入表面的成分，并采用逐层递推 法得出了钛在H13钢中的浓度深度分布，借助掠面x射线衍射考察了注入表面的相结构. 关键词： 钛离子注入 金属蒸汽真空弧 卢瑟福背散射 掠面x射线衍射