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1.
Th. Seyller K.V. Emtsev F. Speck A. Tadich J.D. Riley O. Rader A.M. Shikin 《Surface science》2006,600(18):3906-3911
Photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy were used to investigate the electronic and structural properties of graphite layers grown by solid state graphitization of SiC(0 0 0 1) surfaces. The process leads to well-ordered graphite layers which are rotated against the substrate lattice by 30°. On on-axis 6H-SiC(0 0 0 1) substrates we observe graphitic layers with up to several 100 nm wide terraces. ARUPS spectra of the graphite layers grown on on-axis 6H-SiC(0 0 0 1) surfaces are indicative of a well-developed band structure. For the graphite/n-type 6H-SiC(0 0 0 1) layer system we observe a Schottky barrier height of ?B,n = 0.3 ± 0.1 eV. ARUPS spectra of graphite layers grown on 8° off-axis oriented 4H-SiC(0 0 0 1) show unique replicas which are explained by a carpet-like growth mode combined with a step bunching of the substrate. 相似文献
2.
The electrochemical oxidation of 1, 3-benzenedithiol was investigated in a 0. 100 mol/L tetrabutylammonium perchlorate/acetonitrile electrolyte. The electrochemical techniques used were potential sweep, bulk electrolysis, rotating disc and the potential step method. The combination of the techniques yielded the number of electrons transferred per molecule, the reaction order, the transfer coefficient, the diffusion coefficient and concentration of dithiol anions, the standard heterogeneous rate constant as well as the formal potential and equilibrium constant of the preceeding dissociation reaction. This paper also illustrates the methods for studying the electrode kinetics of reactions which (a) involve a chemical reaction preceeding the electron-transfer process, (b) have insoluble polymer products, and (c) are totally irreversible. 相似文献
3.
The kinetics of reactions occurring at the gas-exposed surfaces of charged mixed ionic electronic conductors (MIECs) are examined
from theoretical first principles. Analysis based on the classical electrochemical potential-transition state theory model
reveals that the nature of the reactions is electrochemical in general. However, the influence of the surface potential on
the reaction rate is opposite for adsorption and incorporation reactions. Two-dimensional finite volume models of an MIEC
as working electrode in a half-cell configuration are presented. The results for a simple, two-step reduction process show
that the effect of the surface potential on the rate of reactions is minimal for incorporation-limited reactions but more
influential for adsorption-limited reactions.
An erratum to this article is available at . 相似文献
4.
A simple method of determining ultra-trace Au in natural water was presented by using graphite furnace atomic absorption spectrophotometry (GFAAS) after in situ enrichment with thiol cotton fiber (TCF). The sample solution was adjusted to pH 1.5-2.0 with HCl, then the water sample was passed through a column packed with 0.10-0.20 g TCF and the flow rate was controlled at 20-40 ml min−1. The effects of interferences, such as complexing and oxidizing agents and other elements adsorbed on TCF were overcome by chemical treatments prior to the desorption of Au. The adsorbed Au was adsorbed with 2.0 ml hot acid, then it was extracted with 1.00 ml methyl isobutylketone (MIBK). For a 5 l water sample, the detection limit of Au is 0.02 ng l−1. The relative standard deviation (R.S.D.) for the determination of 1.44 ng l−1 Au was 9.4%.The method was applied to determine ultra-trace Au both in suspended phase and soluble phase in natural water, the concentrations of total Au in natural water samples range from 0.51 to 67.82 ng l−1. The recovery of added 0.50-6.00 ng l−1 Au was 80-95%. The method is useful in prospecting for Au deposits by means of hydrogeochemical methods. The enrichment is carried out in the field, and then the determination of Au is completed later in the laboratory. 相似文献
5.
元素在石墨炉内石墨探针表面上的原子化机理研究:Ⅶ.锗的原子化机理 总被引:2,自引:0,他引:2
本文应用X-射线衍射,X-射线光电子能谱,俄歇电子能谱和其它一些实验,考察石墨炉升温过程中氟化锗,锗酸钠在石墨探针表面上的形态变化,阐明了它们的原子化机理:GeF2与Na2GeO3首先分解为GeO2,GeO2还原为GeO,后者在>2400K热分解产生自由态的锗原子,GeF2和Na2GeO3的原子化均源于GeO(g)的气相分解。原子化的升温过程中,在1400-2400K GeF2和Na2GeO3都产 相似文献
6.
7.
Due to the discovery of Au as a catalyst for low temperature CO oxidation, the adsorption of CO on Au surfaces has attracted a lot of attention recently. On stepped and rough single crystal surfaces as well as on deposited particles two characteristic desorption states above 100 K have been observed via TPD. We have studied Au deposits on graphite in order to elucidate the nature of these desorption peaks in more detail. For this purpose, Au was deposited at 100 K and 300 K on HOPG as a weakly interacting support. In analogy to other supports, we obtain two desorption states (∼140 K and ∼170 K) whose relative intensities depend strongly on the deposition temperature with the high temperature peak being much more pronounced for the 100 K deposits. After annealing to 600 K, both states drastically lose intensity. XP spectra, on the other hand, show virtually no decrease of the Au 4f intensity as would be expected for desorption or significant changes of the particle morphologies. We conclude that both desorption peaks are defect-related and connected with under-coordinated Au atoms that are lost for the most part upon annealing. These sites could be located at the perimeter of dendritic islands or on small, defect-rich particles in addition to larger particles not adsorbing CO at 100 K. Preliminary STM results are in favour of the second interpretation. 相似文献
8.
陈隆懋 《光谱学与光谱分析》1997,17(4):73-76
本文对国产WLY100型顺序扫描ICP光谱仪在设计中对单色仪,高频发生器,扫描机构,测光系统,短紫外光域的测量,恒温,气流控制与软件编制等方案的选择作了详尽的阐述,稳妥的方案使研制工作顺利进行,保证整机一次成功。 相似文献
9.
An exact method based on Green's equation is used to find the diffusion-controlled faradaic current for certain electrode geometries that incorporate edges and vertices. Thereby the magnitudes of the time-independent current density associated with angled electrode/electrode and electrode/insulator junctions are calculated. As well, the square-root-of-time-dependent currents associated with vertices, receive attention. These terms extend to longer times, the Cottrell formulation appropriate for short times. Though most of the problems solved here have been tackled previously, the novel Green function approach is shown to be straightforward and intuitive. 相似文献
10.
强酸性条件下 ,钯 (Ⅱ )与 5 [( 5 氯 2 吡啶 )偶氮 ] 2 ,4 二氨基甲苯 ( 5 Cl PADAT)生成紫红色螯合物 ,该螯合物可与十二烷基苯磺酸钠 (SDBS)生成离子缔合物 ,离子缔合物经 0 .3μm孔径的硝化纤维微孔滤膜富集后 ,于小体积 ( 0 .5mL)的浓硫酸中溶膜 ,用石墨炉原子吸收法 (GFAAS)测定 ,富集倍数可达 2 0 0倍 ,钯含量在 4.69× 1 0 - 1 2 ~ 7.0 9× 1 0 - 9mol/L范围内线性良好 ,检出限为 1 .78×1 0 - 1 2 mol/L。方法用于海水中痕量钯的测定。 相似文献