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  • 1
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 774 (1995), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 26 (1996), S. 1037-1043 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanically polished zirconium electrodes were potentiodynamically polarized in phosphate buffer solutions of various pH values and in 0.5 lvl NaOH. The results show that the shape of the I-E curves is independent of the solution pH. At relatively low scan rates, oxygen gas evolution was observed. The oxide film thickness was calculated from the values of the charge consumed in the anodic process assuming 100% current efficiency for oxide formation below oxygen evolution (lower values for the current efficiency are assumed for potentials above oxygen evolution). Capacitance measurements, together with the calculated oxide thickness, were used to estimate values for the dielectric constant of the oxide. Two different values of the dielectric constant were obtained for the oxides formed in the range of potential below and above oxygen evolution. Also, higher dielectric constant values were obtained with increasing solution pH. Anion incorporation was assumed to increase the conductivity of the oxide films and, hence, decrease the dielectric constant. A two-layer structure is proposed for the anodically formed oxide on zirconium in aqueous solutions; an anion-free layer near the metal and an outer layer containing the incorporated anions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 13 (1982), S. 376-385 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Passivation of commercial grade tin (99.5%) was studied in 0.1 M KCl, KBr and KI solutions using the potentiodynamic technique involving cathodic and anodic polarization at various scan rates. While low scan rates (0.1 mV/sec) lead to the complete deterioration of the anode in chloride solutions, higher scan rates of 1 and 5 mV/sec lead to the appearance of two anodic peaks. These peaks disappear at still higher rates (10 mV/sec). In bromide solutions, two anodic peaks appear with scan rates of 1 and 5 mV/sec, and only one peak is observed with 50 mV/sec. A white precipitate is formed in both chloride and bromide solutions during anodic scanning. No gas evolution (O2, Cl2 or Br2) could be detected up to anode potentials of 3-4 V (SCE). At scan rates of 1 mV/sec and higher values, pitting does not occur, and thick anode films are formed. The film is gray in chloride solutions, and yellowish gray in bromide solutions. Values of the corrosion potential Ecor are recorded for the forward and reverse scanning. The corrosion cd Icor is calculated both by the Tafel extrapolation procedure and by the linear polarization technique. The latter gives more accurate results. In Cl- and Br- solutions, the first anodic peak associated with passivation is more anodic than the equilibrium potentials for the tin/tin oxides or hydroxides. Passivation is explained as a result of the formation of the sparingly soluble salts Sn(OH)Cl, Sn(OH)Br which appear both in the precipitate and in the anode film. The passivating films are constituted at least partially of these basic salts, and contain a proportion of the oxides and hydroxides of Sn. From the effect of scan rates on the characteristics of the anodic peaks, it appears that the formation of thick anode films is governed by the diffusion kinetics for porous films. Of the three possibilities considered as explanations for the second anodic peak (oxidation of impurities, oxidation of halides to oxyacids, and structural changes in the film) the latter appears to be the most probable one.Thick anodic films are not formed in iodide solutions (scan rates 1, 5, 10 mV/sec), and the anode surface remains very bright. Dense evolution of I2 occurs during anodic polarization, and apart from I2 which dissolves in solution, the latter remains clear. Only one peak is observed in the forward anodic scanning. The polarization resistance technique gives Icor = 0. Thermodynamic calculations show that I3-, HIO, IO-, HIO3, IO3-, HIO4, and IO4- occur in 0.1 M KI solutions at potentials less anodic than the potential of the anodic peak (1.32 to 1.37 V, vs SCE). This peak potential is more anodic than the quilibrium potential for I2 evolution.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 13 (1982), S. 305-309 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The linear polarization method of corrosion rate determination has been investigated on the basis of the equation of Stern and Geary. It has been demonstrated that use of an average value for the parameter B does not lead to accurate results. A procedure has been suggested for rapid monitoring and more accurate measurements of corrosion rates, and this is based on the calculation of B from independent measurements of the electrode-kinetic parameters of the corrosion system under investigation. Values of B have been calculated for a wide range of Tafel slopes for the case when both cathodic and anodic partial reactions are controlled by charge transfer. Using the correct value of B, potential/corrosion current density curves are constructed for various polarizing current densities. It has been shown that these calibration curves are very helpful in the rapid monitoring of corrosion rate using the linear polarization method at constant current density with a three-electrode arrangement.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 17 (1986), S. 174-183 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Growth of thin transparent anode films on Sn in neutral media has been studied by measuring galvanostatic anodic charging curves in phosphate buffer, 0.1M KCl and 0.1M Na2SO4 solutions (pH 6.6-6.7) at low current densities. The experimental technique is essentially the same as that used in previous investigations on valve metals. Although the rise in the anode potential of Sn does not exceed 2.0 V, the shape of the anodic charging curve is identical to that observed on valve metals: being thus composed of a linear and a non-linear region. Application of the kinetics of galvanostatic anodization to the results on Sn show that: (i) the oxide formation rate is linearly related to the ionic current density i by a double logarithmic plot, (ii) the reciprocal capacity is linearly related to log i, and (iii) the Tafel behaviour is exhibited at constant charge. These relations indicate that the anode film growth occurs by an activation-controlled ion conduction under the influence of the electric field across the film phase according to an exponential law. Treatment of the results allows the estimation of some kinetic parameters of film growth, e.g.: (i) the constants a and b of the empirical relation between oxide formation rate and i, (ii) the constants A and B of the exponential law, (iii) the electric field which is of the order of 106 V/cm in phosphate, and 107 V/cm in both chloride and sulphate solutions, and (iv) the effective activation distance for the ionic jump over the energy barrier associated with cation transport within the film, whereupon relative (and not absolute) values can only be obtained. Comparison between the present results and previous ones (also on Sn) taken by potentiodynamic technique shows that while diffusion kinetics play an important role in the formation of thick anode films by the potentiodynamic technique, activation-controlled kinetics explain the present results on the galvanostatic formation of thin transparent anode films.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 19 (1988), S. 294-301 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Some ESCA measurements have been carried out on the anode film formed on BDH Sn foil by the potentiodynamic technique up to 2.5 V (SCE) in (i) phosphate buffer, pH 6.7, (ii) 0.1 M KCl, 0.1 M Na2SO4, pH 6.6, in order to identify the elements, and possibly also some compounds, present in the film. The results in phosphte buffer indicate the presence of: (i) Sn(II) and Sn(IV) oxides and hydroxides, (ii) tin phosphate species probably (HPO4)2-, (H2PO4)-, and insoluble phosphate complexes and (iii) evidence is given for the formation of soluble Sn species containing OH or phosphates before the beginning of passivity. The results in chloride solutions indicate the presence in the anode film of Sn, O and Cl in various states of combination such as: (i) Sn(II) and Sn(IV) species (oxides, chlorides and some hydroxides, (ii)) adsorbed oxygen and water, and (iii) basic or oxysalts or complexes involving Sn, O, Cl, and K. The results in Na2SO4 solutions indicate the presence in the film of Sn, O, S, and Na in the form of: (i) Sn(II) and Sn(IV) oxides and hydroxides, (ii) Na2SO4, other un- identified S species, and possibly also traces of PbS (from traces of Pb present in the Sn foil), (iii) adsorbed oxygen and water, and (iv) basic or oxysalts or complexes involving Sn, Na, O, sulphate and other unidentified S species.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 22 (1991), S. 390-395 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The kinetics of HER on Ti electrodes in H2SO4 of various concentrations in the pH range of 0.24-1.88 was studied. Cathodic Tafel lines were measured potentiodynamically at a scan rate 1.0 mVs-1 within the H2 evolution potential range. Linear parallel Tafel lines of a slope of 152 mVdecade-1 were obtained. A value of 0.73 was calculated for the reaction order wrt aH+ using the exchange cd, i0 Tafel lines measured on oxide covered electrodes showed three deviations from linearity. An attempt was made to explain the deviations in terms of hydride formation and chemical oxide dissolution. Tafel slopes of 152 mVdecade-1 were also observed for the HER on oxide-covered electrodes. The nature and composition of the oxide did not depend on the electrolyte in which the oxides were formed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 309-315 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Experimental Factors Affecting Oxide GrowthResults of galvanostatic anodization of various metals with varying valve-metal behaviour including Nb, Ta, Zr, Ti, Al, W, Te, Sb, and Bi are compiled and compared with respect to the effect of various experimental factors such as surface pretreatment, stirring, solution composition, temperature of the bath, on the efficiency of oxide growth relative to that for other anodic processes. It is concluded that all of the above factors play an important role in the anodization of the non-typical valve metals, particularly Sb, Bi and W. Typical anodic charging curves associated with the process of oxide growth are given for several valve metals. Experimental data relevant to the phenomena of oxide breakdown are recorded and compared. The results indicate that the mechanism of breakdown varies for the same metal with variations in the experimental conditions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 12 (1981), S. 421-431 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A comprehensive presentation of the theory of galvanostatic anodization has been given in order to enable interpretation and prediction of the anodization behaviour of barrier layers during technical work on various value metals. The following parameters have been considered, and the relations between them have been established: (i)oxide formation rate,(ii)reciprocal capacity,(iii)electric field strength,(iv)pre-polarization oxide thickness,(v)interfacial potentials,(vi)the height and width of energy barrier for ion transport in the oxide phase,(vi)the oxide growth rate as derived from the dependence of cd on time under constant potential, and(vii)capacity.Furthermore, it has been demonstrated that potentiostatic curves can be derived from galvanostatic results, and the derived curves are similar to those directly measured by the potentiostatic technique. The theory has been satisfactorily applied to the experimental results based on the anodic charging curves and other complementary measurements on a large number of valve metals including Nb, Ta, Zr, Ti, Al, W, Te, Sb, and Bi.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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