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排序方式: 共有202条查询结果,搜索用时 31 毫秒
1.
M. D. Warren 《国际流体数值方法杂志》1983,3(3):217-225
This paper derives the convection–diffusion-reaction equation governing the reaction between the dissolved oxygen in sea-water and the steel walls of a pulsating crack. By the neglect of the diffusion term it is shown that an exact solution of the convection-reaction equation can be obtained. A numerical method for the solution of the complete convection–diffusion-reaction equation is derived by the use of finite differences. The numerical computation of the initial transient and the final periodic steady-state values is also discussed. 相似文献
2.
The stability of spontaneous thin layers and thin layers formed upon cathodical polarization of Ti in KOH solutions have been
studied by potentiostatic and ellipsometric methods. At open circuit potential (OCP) the strongly adherent films, whose thickness
depends on the concentration of the KOH solution, were formed. During the cathodic polarization the transformation of these
films to weakly adsorbed precipitated layers on the electrode surface was observed. Comparing the theoretically computed curves
with the experimental Ψ vs Δ loci measured ellipsometrically, the complex indices of refraction and the thickness of the generated films, from 3.6
to 60 nm in 1 M KOH and from 36 to 105 nm in 5 M KOH (adherent to the electrode surface), were determined. At OCP the rate
of film growth increases with increasing the concentration of KOH solution. Cathodic polarizations change the chemical composition
and retard the rate of film growth. Based on the ellipsometric and electrochemical data the chemical compositions of the formed
films consisted of TiO2, Ti2O3, TiO2·H2O, Ti(OH)3 and TiOOH·nH2O. 相似文献
3.
Hemispherical ultramicroelectrodes (2.5–12.5 μm in radius) fabricated from silver or amalgamated copper, gold or platinum were used in the cathodic stripping of various anions. A comparison is presented between the results obtained using electrodes of a conventional size at slow sweep rates (ca. 100 mV s?1) and those obtained using ultramicroelectrodes under fast linear-sweep conditions (ca. 700 V s?1). Problems in maintaining reproducible electrode surfaces under various experimental conditions are discussed. In addition, the benefit of using electrodes of microscopic dimensions is illustrated by their utilization in the analysis of very small volumes of analyte that result from a solvent back-extraction process. 相似文献
4.
Cathodic reduction of -azidocinnamic ester under aprotic conditions on Hg, Pt, or graphite electrodes can be directed to high yields of N,N-diacylated dehydroaminoacid derivates (f.i. addition of acetic anhydride) or to almost quantitative yields of -aminocinnamic ester in very pure form by careful addition of H+-donors. The dehydroamino compounds in turn can be further reduced to the corresponding saturated compounds by following H+-addition and changed electrolysis potential. Almost no dimerization occurs. 相似文献
5.
Boron-doped diamond (BDD) electrodes were used to investigate the possibility of detecting aniline by linear-sweep cathodic stripping voltammetry. It was found that the dimeric species (p-aminodiphenylamine and benzidine) formed by anodic oxidation of aniline during the accumulation period are involved in electrochemically reversible redox processes and, in acidic media, the shape of the stripping voltammetric response is suitable for aniline detection in the micromolar concentration range. The low background current of conductive diamond is an advantage compared to other electrode materials and allows a detection limit of 1 μM. Weak adsorption properties and the extreme electrochemical stability are additional advantages of BDD and it was found that, even after long-time measurements, the electrode surface can regain its initial activity by an anodic polarization in the potential region of water decomposition. 相似文献
6.
7.
A sensitive voltammetric method is presented for the determination of tract levels of Mn (II) using carbon film electrodes fabricated from carbon resistors of 2 Ω. Determination of manganese was made by square wave cathodic stripping voltammetry (CSV), with deposition of manganese as manganese dioxide. Chronoamperometric experiments were made to study MnO2 nucleation and growth. As a result, it was found to be necessary to perform electrode conditioning at a more positive potential to initiate MnO2 nucleation. Under optimised conditions the detection limit obtained was 4 nM and the relative standard deviation for eight measurements of 0.22 nM was 5.3%. Interferences from various metal ions on the response CSV of Mn(II) were investigated, namely Cd(II), Ni(II), Cu(II), Cr(VI), Pb(II), Zn(II) and Fe(II). Application to environmental samples was demonstrated. 相似文献
8.
9.
本文用热处理法成功地制备了性能稳定的Eastman-Kodak AQ/GC修饰电极,对Fe~(3+)/Fe~(2+)及其络合阳离子在该电极上的行为进行了研究。表明AQ膜对Fe~(3+)和Fe~(2+)具有相近的交换能力,可用于Fe~(3+)或Fe~(2+)及其总量的阴极溶出伏安法测定。线性范围分别为2.0×10~(-7)~2.2×10~(-5)mol/L(Fe~(3+))和5.0×10~(-7)~2.0×10~(-5)mol/L(Fe~(2+)),检出限为1.0×10~(-7)mol/L(Fe~(3+))。文中对电极反应和再生进行了探讨。 相似文献
10.
A method was developed to determine the biocide pyrithione in natural waters. The method is based on cathodic stripping voltammetry (CSV) in the presence of Triton-X-100, which is used to separate the peak from interfering thiol compounds. Optimised conditions include a Triton-X-100 concentration of 4 ppm and a pH adjusted to 9 using ammonia buffer. The adsorption potential for pyrithione was −0.10 V and the peak occurred at −0.2 to −0.3 V. Detection was by differential-pulse CSV. The detection limit in UV-digested seawater was 1.5 nM for a deposition time of 60 s. In principle, this limit of detection could be lowered by extending the adsorption time, but in practice this may not be possible due to interferences by other organic compounds (surfactants and thiol compounds) in natural waters. 相似文献