Size-dependent dissociation of small cobalt clusters on ultrathin NaCl films

Mass-selected anionic cobalt clusters of two different sizes (Co2 and Co13) were deposited onto ultrathin NaC1 films grown on an Au(111) substrate.Using scanning tunneling microscopy experiments and density functional theory simulations,we show that the deposited Co2 cluster dissociates and that the resulting Co atoms dope the NaCl surface by substituting Na ions.In contrast,the larger Co13 cluster does not dissociate and remains stable on top of the NaC1 film.The sizedependent fragmentation of clusters is an important aspect in the understanding of the chemical interaction between size-selected small aggregates of atoms and supporting surfaces.     

NaCl溶液中Zn－Al－Cd合金的接触腐蚀研究

研究了作为牺牲阳极材料的Ｚｎ－Ａｌ－Ｃｄ合金在ＮａＣｌ溶液中与Ａ３钢、３０２不锈钢和纯铜偶接时的接触腐蚀行为，探讨了溶液中Ｃｌ－浓度变化，以及电偶对中阴极金属材料和阴阳极面积比Ａｃ／Ａａ不同时对电偶电流密度ｊＺｎｇ和电偶电势Ｅｇ的影响。结果表明，电偶对中阴极金属材料不同，ｊＺｎｇ随Ｃｌ－浓度增大有不同的变化趋势；ｊＺｎｇ与Ａｃ／Ａａ成正比关系；Ｃｌ－浓度变化对Ｅｇ的影响较大，而大多数浓度下阴极金属材料和阴阳极面积比不同对Ｅｇ的影响较小     

Scattering efficiency of aggregated clusters of spheres: dependence on configuration and composition

We study the orientation average scattering cross section of various isolated aggregates of identical spherical particles as functions of their size, optical properties, and spatial configurations. Two kinds of aggregates are studied: latex particles in water and rutile titanium dioxide pigments in a polymeric resin, with size parameters varying from 0.6 to 2.3. Calculations are performed by using a recursive centered T-matrix algorithm solution of the multiple scattering equation that we previously developed [J. Quant. Spectrosc. Radiat. Transfer 79-80, 533 (2003)]. We show that for a specific size of the constituent spheres, their respective couplings apparently vanish, regardless of the aggregate configuration, and that the scattering cross section of the entire cluster behaves as if its constituents were isolated. We found that the particular radius for which this phenomenon occurs is a function of the relative refractive index of the system. We also study the correlations between the strength of the coupling among the constituent spheres, and the pseudofractal dimension of the aggregate as it varies from 1 to 30.     

Effect of growth conditions on the Al composition and quality of AlGaN film

Effects of growth conditions on Al composition and quality of Al_xGa_1−xN epilayer grown by low-pressure matelorganic vapor phase epitaxy (MOVPE) have been investigated. The dependences of Al composition, growth rate and quality on the NH₃ flow rate, TMAl flow rate and growth temperature were studied. The Al composition and quality of Al_xGa_1−xN film depend not only on the TMAl flow rate, but also on the NH₃ flow rate and on the growth temperature. The Al composition of Al_xGa_1−xN film becomes saturated when the gas-phase composition TMAl/(TMAl + TMGa) increases to 0.4, while quality of Al_xGa_1−xN film becomes much worse. The Al composition of Al_xGa_1−xN film increases with increase in the NH₃ flow rate. The quality of Al_xGa_1−xN epilayer is improved when the growth temperature increases. Possible Al incorporation mechanism is discussed.     

Corrosion inhibition of Al–bronze in acidified 4% NaCl solution

The synergistic effect between either benzotriazole (BTA) or thiourea (TU) and iodide ion are used to retard the dissolution of Al–bronze alloy in deaerated solution of acidified 4% NaCl of pH 1.8–2 at 60 °C; this is shown by the weight loss and polarization techniques. Iodide ion alone has no effect on the dissolution of the alloy but addition of 100 p.p.m. KI to 300 p.p.m. of both BTA and TU improved the inhibition efficiency to 92% and 78.8%, respectively, and also decreased the anodic current density in both media. This revised version was published online in November 2006 with corrections to the Cover Date.     

Growth and optical properties of Ag clusters deposited on poly(ethylene terephthalate)

The growth and concomitant evolution of the optical properties of Ag nano-clusters deposited on biaxially extruded poly(ethylene terephthalate) films is studied by reflectance difference spectroscopy. It is demonstrated by low energy ion scattering and simulated optical spectra that the clusters form a two-dimensional layer buried beneath the surface of the substrate. The experimental spectra are described by simulations in which different configurations of the host such as anisotropy, amorphization, and dilution are considered in an effective medium approach. The contribution of the anisotropic substrate is used to explain the resulting line shapes. We also discuss the role of the rate of change of the filling fraction with Ag coverage in the evolution of the spectra and the detection of the onset of coalescence by optical means.     

Study of Al alloy corrosion in neutral NaCl by the pitting scan technique

The corrosion behavior of commercial Al alloys was studied in neutral 0.6 mol L⁻¹ NaCl by using single-cycle polarization. Qualitative interpretation of pitting scans in both deaerated and naturally aerated NaCl solution, with the aid of corrosion morphology characterization, allowed for inference of the features of localized corrosion as a function of Al substrate nature. Electrochemical characteristic parameters such as pitting (E_pit), repassivation or protection (E_prot) potentials and pit transition potential (E_ptp) were determined. The validity of the difference ΔE = |E_pit − E_prot| as criterion for susceptibility to localized corrosion of aluminium alloys is discussed.     

Growth of CNTs on Fe-Si catalyst prepared on Si and Al coated Si substrates

In this paper we report the effect of Al interlayers on the growth characteristics of carbon nanotubes (CNTs) using as-deposited and plasma etched Fe-Si catalyst films as the catalysts. Al interlayers having various thicknesses ranging from 2 to 42?nm were deposited on Si substrates prior to the deposition of Fe-Si catalysts. It was found that the Al interlayer diffuses into the Fe-Si catalyst during the plasma etching prior to the CNT growth, leading to the swelling and amorphization of the catalyst. This allows enhanced carbon diffusion in the catalyst and therefore a faster growth rate of the resulting CNTs. It was also found that use of an Al interlayer having a thickness of ～3 ± 1?nm is most effective. Due to the effectiveness of this, the normally required catalyst etching is no longer needed for the growth of CNTs.     

Self-catalytic growth and characterization of AlGaN nanostructures with high Al composition

Journal of Materials Science: Materials in Electronics - AlGaN ternary alloy nanostructures have emerged as an important building block for optoelectronic devices and exhibit broad application...     

Al和Li对镁基体氧化膜成分及厚度影响

合金元素对氧化膜性能影响很大。分别恒流氧化了纯镁、AZ91HP和Mg-Li合金并测量了氧化膜成分及厚度。EDX分析表明，在Mg—Li合金上形成的氧化膜P含量最高（39．39％），AZ91HP上最低（35．88％）；膜厚测量结果为Al和Li分别使氧化膜厚度稍微减少和大大增加。Al和Li元素对氧化膜性能影响可以用Mg^2＋、Al^3＋和Li^＋移动速度不同以及MgO、Al2O3和Li2O的PBR（Pilling—Bedweorth ratio）值不同来解释。     

Controlled growth and optical properties of Al3+ doped ZnO nanodisks and nanorod clusters

Products consisted of Al-doped ZnO nanodisks and ZnO nanorod clusters were synthesized by chemical co-deposition process. The nanodisks with large polar surface are about 1–2 µm in diameter and 20 nm in thickness. The ZnO nanorods have an average diameter of 40 nm. The content of ZnO nanodisks can be adjusted by Al³⁺ content. The growth mechanism of the ZnO nanodisks is also discussed. Room temperature photoluminescence (PL) measurements show that photoluminescence peaks of the products decrease with the increase of Al content.     

基于AlN基板的不同Al组分的AlGaN材料生长

采用脉冲法生长了200nm厚的AlN薄膜,其XRD摇摆曲线的半高宽为130aresec,表面粗糙度为2.021nm.以此AIN层为基板生长了不同Al组分的AlGaN薄膜,高分辨率XRD测试发现,随Al组分的增加,AlN基板层对AlGaN薄膜施加的压应力增大,同时,AlGaN薄膜在生长合并过程中产生的张应力也增大.在Al组分为0.67时,发现这两种应力处于一种平衡的状态,此时的AlGaN薄膜有最优的结晶质量.     

Gibbs energy calculation of liquid Zr–Al–Ni and Zr–Al–Cu–Ni alloys with clusters

The Gibbs energies of liquid Zr–Al–Ni and Zr–Al–Ni–Cu alloys with multi-clusters are calculated based on the statistical mechanism in this paper. The results show that the quantity of clusters depends mainly on the temperature and the concentration of the melt. It increases gradually with the decrease of temperature or with the increase of x _Ni in liquid (Zr₈₀Al₂₀)_1−x Ni _x alloys; the quantity of Zr₂Ni clusters reaches its maximum of 0.061 mole at x _Ni = 0.336. In (Zr₈₀Al₂₀)_1−x Ni _x liquid alloy the existence of clusters causes the falling of the Gibbs energy. The Gibbs energy drops about 4000 J/mol at x _Ni = 0.35 if the effect of cluster of Zr₂Ni is considered or about 8000 J/mol at x _Ni = 0.40 if both of clusters of Zr₂Ni and ZrNi are taken into account.     

Theoretical study on the structure and stability of aluminum hydride (Al n H3n ) clusters

Density functional theory (DFT) calculations have been carried out to study the linear polymeric Al _n H_3n (n = 1–12) clusters and cage Al _n H_3n (n = 6, 8, 10, and 12) clusters. In particular, a stable cage-chain (Al₁₂H₃₆) _m (m = 2, 3) structure has been predicted for the first time, with the basic unit, cage Al₁₂H₃₆ structure connected by double hydrogen-bridged bonds (i.e., Al–2H–Al). The stability of these clusters has been confirmed by the large binding energies and substantial energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and the cage-chain structure is more stable than the corresponding chain and cage forms. Furthermore, with the cluster size increasing, the aluminum hydride clusters tend to exist with the cage structure compared with the chain structure, even though the formation of the chain structure is much easier than others. Also, the heats of formation for some clusters have been calculated by the atomization reaction method based on the results from DFT calculations, and it is revealed that the cage and cage-chain clusters can store more energy and, especially the latter, is more promising as a kind of energetic material.     

Corrosion behavior of Al, Sc-co-doped ZnO thin films in 3.5% NaCl solution

The corrosion behavior of Al, Sc-co-doped zinc oxide films (with Sc-dopant varying in 0, 0.01, 0.13, 0.24 and 1.07 wt.% Sc) in 3.5% NaCl solution has been investigated. It was compared to that of the commercial indium tin oxide (ITO) thin film. The films were prepared by sputtering on the ZnO (4 N) target with RF and on the targets of Al (4 N), Al-0.4 wt.% Sc, Al-0.8 wt.% Sc, Al-1.7 wt.% Sc alloy and pure Sc with DC. The electrochemical studies revealed that the corrosion resistance of the films increases in the order AZO < Sc-doped AZO < ITO < annealed AZO (at 300 °C for 1 h). The AZO doped with higher Sc-content is more resistant to corrosion. Examining the surface morphology through atomic force microscope (AFM) and scanning electron microscope (SEM), the film, which is more susceptible to corrosion depicted a rougher surface. The electrical resistivity of the films maintained almost unchanged in 120-h test. However, the optical transmittance varied with the concentration of Sc-dopant in the films. The higher Sc-dopant in the film the more stable it is to maintain higher transmittance. Higher corrosion resistance for the Sc-doped AZO in comparison with the monotonic AZO is attributed to a release of lattice strain by the Sc (III)-dopant which its size is similar to Zn (II). The most corrosion-resistant specimen (i.e., Sc-doped AZO annealed at 300 °C for 1 h) is considered to have the complete release of the lattice strain.     

纳米铝铅合金的生长与形貌研究

依据Miedema理论设计合金均值混合成分,采用磁控溅射法制备合金。SEM和HRTEM结果表明合金是由5纳米左右的颗粒组成,并且颗粒分布均匀。正混合焓合金出现非晶可能是因为界面处的应力变形造成的。