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634
Wear-accelerated corrosion of passive metals in tribocorrosion systems
- J. Electrochem. Soc
"... A model is presented which describes the effect of mechanical and materials parameters on the wear-assisted corro-sion rate of passive metals under sliding wear conditions. The model is based on a consideration of contact between the sliding surfaces at multiple asperities and it takes into account ..."
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A model is presented which describes the effect of mechanical and materials parameters on the wear-assisted corro-sion rate of passive metals under sliding wear conditions. The model is based on a consideration of contact between the sliding surfaces at multiple asperities and it takes into account the passivation behavior of the metal. Wear experiments were carried out in a reciprocating pin-on-plate tribometer permitting the control of mechanical and electrochemical con-ditions. An alumina pin was rubbed on nickel, chromium, stainless steel, and titanium alloy plates, in sulfuric acid or sodium sulfate solution. The relative importance of mechanical and electrochemical metal removal was evaluated while applying an anodic potential. Additional experiments were performed under cathodic polarization. The results show that the proposed model can describe correctly the effect on dissolution rate of different mechanical parameters such as applied normal force, stroke length, frequency, and sliding speed. Qualitative agreement was observed with the predict-ed effect of the materials parameters hardness and passivation charge, but uncertainties concerning the real value of pas-sivation charge and, in some cases, wear of the alumina pin limit the predictive capability of the model when comparing different materials. The experimental results obtained in this study demonstrate that to understand the mutual interac-tions between mechanical and electrochemical parameters affecting wear-accelerated corrosion it is necessary to look at the tribocorrosion system as a whole.
Solid-state detectors for the potentiometric determination of gaseous oxides
- I. Measurement in air, J. Electrochem. Soc
, 1977
"... This paper suggests that the potentiometric detection of sulfur oxides in air is feasible with solid-sulfate lectrolytes, and presents experimental results on the electrode Pt, SO2, O2/SO4 =. Several experimental parameters, namely, Ps02, temperature, and flow raSe, are studied with concentration ce ..."
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This paper suggests that the potentiometric detection of sulfur oxides in air is feasible with solid-sulfate lectrolytes, and presents experimental results on the electrode Pt, SO2, O2/SO4 =. Several experimental parameters, namely, Ps02, temperature, and flow raSe, are studied with concentration cells using potassium sulfate, as the electrolyte. A solid reference lectrode based on an Ag/Ag + electrochemical couple is also studied as a replacement for the gas reference electrode. The autaors conclude that rapid conversion of several gaseous ulfur compounds, namely, H2S, CHsSH, etc., into oxides occurs under the cell operating conditions, and that rapid equil ibrium is reached between SO2, SOs, and 02 at the electrode. Prel iminary results of tests using solid elec-trolytes to detect other gaseous oxides in air are also given for the Pt, COs, O~ICOs =, and Pt, NO2, O2/NO3- systems. Success with solid-state oxygen detectors based on stabilized zirconia in the ppm concentration range has
For a review and references
- Reports
, 1987
"... Locally stabilized P1-nonconforming quadrilateral and hexahedral finite element methods for the Stokes equations. (English summary) J. Comput. Appl. Math. 236 (2011), no. 5, 714–727. In this paper a local-pressure projection stabilization method is applied to P1-P1 nonconforming quads and hexahedral ..."
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Locally stabilized P1-nonconforming quadrilateral and hexahedral finite element methods for the Stokes equations. (English summary) J. Comput. Appl. Math. 236 (2011), no. 5, 714–727. In this paper a local-pressure projection stabilization method is applied to P1-P1 nonconforming quads and hexahedral finite element pairs approximating velocity and pressure in the Stokes equations. A consistent derivation of the stabilized method is provided along with a priori error estimates. Several numerical tests are presented to illustrate the stability and convergence properties predicted by the theoretical results.
The Kinetics of Oxygen Reduction in Molten Phosphoric Acid at High Temperatures
"... The so lub i l i ty and d i f fus iv i ty of oxygen in concent ra ted (98%) phosphor ic acid, and the k inet ics of its reduct ion on p la t inum wi th in the 25~176 temperature in terva l have been invest igated ut i l iz ing glass insu la ted Pt mic roe lec t rodes wi th radi i of 12.7 and 250 ~m. ..."
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The so lub i l i ty and d i f fus iv i ty of oxygen in concent ra ted (98%) phosphor ic acid, and the k inet ics of its reduct ion on p la t inum wi th in the 25~176 temperature in terva l have been invest igated ut i l iz ing glass insu la ted Pt mic roe lec t rodes wi th radi i of 12.7 and 250 ~m. The entha lpy of solut ion of oxygen in phosphor ic acid was found to be 2.2-+ 0.3 kcal mol- ', and the ent ropy of solut ion is- 12.6-+ 0.8 cal K- ' mol-'. Fundamenta l ent ropy calculat ions indicate that the large negat ive ent ropy change upon solut ion is due to the loss of three degrees of f reedom in t rans lat ion (free t rans lat ion becoming hind-ered) and two degrees of f reedom in rotat ion (only l ibrat ion occurs in solution). A hydrogen bonded mode l for the state of oxygen in phosphor ic acid is found to be cons is tent with the exper imenta l values obta ined for entha lpy of solution, en-t ropy of solution, and heat of act ivat ion for diffusion, 5.9-+ 0.4 kcal mol- '. The e lectrochemical t ransfer coeff icient for the oxygen reduct ion react ion was found to remain constant wi th temperature, at 0.63 +- 0.05. The exchange cur rent dens i ty at 25 ~ in 98 % H3PO4 is 8 x 10-I2A cm-2, increas ing wi th temperature wi th an apparent heat of act ivat ion of 17.3 kcal mol- '. The growing interest in pract ica l fuel cel ls leads to the need to invest igate the k inet ics of react ions under condi-t ions re levant to the i r funct ion. Of these react ions, the. most impor tant is certa in ly that of oxygen reduct ion. In
Potentiostatic high over potential studies of copper deposition from electroless copper solutions
- J. Electrochem. Soc
, 1985
"... The mechan ism of electroless meta l depos i t ion has! been studied so far f rom two aspects: e lectrochemical nd wA structural. First, some mechanis t ic aspects of charge 2.4 t ransfer processes in electroless meta l depos i t ion were 2.2 studied by t rans ient and quasi-steady-state e lectroch ..."
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The mechan ism of electroless meta l depos i t ion has! been studied so far f rom two aspects: e lectrochemical nd wA structural. First, some mechanis t ic aspects of charge 2.4 t ransfer processes in electroless meta l depos i t ion were 2.2 studied by t rans ient and quasi-steady-state e lectrochem-ical techn iques (1-6); second, the mechan is t i c aspects of 2.0 latt ice format ion processes were studied by scann ing and t ransmiss ion electron microscopy (7-9). One unso lved 1.8 prob lem is a correlation between the e lectrochemica l and structural k inet ic parameters. 1.6 The purpose of th is s tudy is to in i t iate work on the elu-c idat ion of the above unso lved correlat ion problem. For 1.4 these studies, we have chosen the potent iostat ic rans ient method (10-13). 1.2 In this communicat ion, we report potent iostat ic
Electrochemistry of conductive polymers VII, Autocatalytic rate constant for polyaniline growth, Synth. Met
, 1989
"... The earlier stage of the polymerization reaction of polyaniline has been studied employing in situ spectroelectro-chemical techniques. The r sults indicate that the nitrene cation appears to be a key intermediate species, which leads to all three possible dimers including a head-to-tail dimer (N-phe ..."
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The earlier stage of the polymerization reaction of polyaniline has been studied employing in situ spectroelectro-chemical techniques. The r sults indicate that the nitrene cation appears to be a key intermediate species, which leads to all three possible dimers including a head-to-tail dimer (N-phenyl-p-phenylenediamine), a tail-to-tail dimer (benzidine), and a head-to-head dimer (hydrazobenzene). The oxidized forms of these dimers were all shown to be capable of growing polyaniline in the presence of aniline, even though aniline was not oxidized. The cyclic voltammetric peaks observed ur-ing the PA synthesis in the middle potential regions were shown to arise from the redox reactions of these dimers, oligo-mers, and degradation products of polyaniline including quinoneimines and p-benzoquinone. Polyaniline (PA) has received a great deal of interest as one of the conductive polymers due to its straightforward methods of preparation and the stability of its conductive form in air (1-18). PA can be prepared chemically (2, 4) or electrochemically (1, 3, 7-18) in aqueous or nonaqueous media. Only those prepared in acidic aqueous media have a conductive form. Its applications as energy storage media (2-4) and as electrochromic devices (10, 11) have been discussed. Despite much work on PA preparation methods and its various properties, its growth mechanisms in the earlier phase of the polymerization reaction still remains unclear. Recently, Stilwell and Park have reported the autocataly-tic nature of the polymerization reaction and its related ki-netic data (16). From the extensive studies, a conclusion is reached that the PA growth reaction competes with degra-dation reaction paths (16, 19). The rate of autocatalytic re-action has also been determined employing normal pulse voltammetric techniques (18). In the early studies by Mohilner et al. (1) and Bacon and Adams (20), it was shown that the formation of a radical cation upon oxidation of aniline is the rate-limiting step. The radical cation thus formed leads to dimerization prod-ucts such as benzidine and p-aminodiphenylamine
The Application of Linear Sweep Voltammetry to a Rotating Disk Electrode for the Reversible Deposition of an Insoluble Species
- J. Electrochem. Soc
, 1980
"... A Nernst diffusion model was employed to obtain an analytical expression for the transient current response of a reversible deposition reaction with in-soluble product occurring on a rotating disk electrode under l inear potential sweep conditions. The results indicated that for low sweep rates the ..."
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A Nernst diffusion model was employed to obtain an analytical expression for the transient current response of a reversible deposition reaction with in-soluble product occurring on a rotating disk electrode under l inear potential sweep conditions. The results indicated that for low sweep rates the current increases monotonically with ime. However, at high sweep rates a maximum value for the current density at finite values of time is predicted. The peak current density normalized with respect to the diffusion l imiting current density was found to be a l inear function of the square root of a dimensionless sweep rate. Furthermore, in this region the response of a rotating disk elec-trode is the same as that in a stagnant system. An experimental investigation based on the reversible deposition of silver showed good agreement with the theoretical predictions. Linear sweep voltammetry (LSV) in stagnant sys-tems has developed into a useful analytical technique
Electrochemical Oxidation of Adenine - Reaction Products and
, 1968
"... The electrochemical oxidation of adenine (6-aminopurine), which gives a single well-defined voltammetric wave at the pyrolytic graphite electrode (PGE), was investigated by macroscale controlled electrode potential at the PGE in aqueous 1M acetic acid solution (pH 2.3) with exhaustive isolation, ide ..."
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The electrochemical oxidation of adenine (6-aminopurine), which gives a single well-defined voltammetric wave at the pyrolytic graphite electrode (PGE), was investigated by macroscale controlled electrode potential at the PGE in aqueous 1M acetic acid solution (pH 2.3) with exhaustive isolation, identification, and determination of reaction products and intermediates. The electrochemical oxidation of adenine appears to follow initially the same path as the enzymatic oxidation, but further oxidation and fragmentation of the purine ring system occur. Thus, adenine is oxidized in a process in-volving a total of 6 electrons per adenine molecule to give as the pr imary product a dicarbonium ion intermediate, which, being unstable, undergoes a further series of reactions: (a) electrochemical oxidation to parabanic acid (some of which is further hydrolyzed to oxaluric acid), urea, carbon dioxide, and ammonia; (b) electrochemical reduction to give ult imately 4-aminopur-puric acid, carbon dioxide, and ammonia; and (c) hydrolysis to allantoin,
Conductometric Sensor for Detection of Elemental Mercury Vapor
- ECS Trans. 2008
"... Several organic and inorganic materials have been tested for possible incorporation into a sensing array in order to add elemental mercury vapor to the suite of chemical species detected. Materials have included gold films, treated gold films, polymer-carbon composite films, gold-polymer-carbon comp ..."
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Several organic and inorganic materials have been tested for possible incorporation into a sensing array in order to add elemental mercury vapor to the suite of chemical species detected. Materials have included gold films, treated gold films, polymer-carbon composite films, gold-polymer-carbon composite films and palladium chloride sintered films.
Concentration, solubility, and equilibrium distribution coefficient of nitrogen and oxygen in semiconductor silicon
- J. Electrochem. Soc
, 1973
"... The concentration of nitrogen and oxygen in semiconductor silicon and their solubilities in silicon at its melting point have been measured by charged particle activation analysis and infrared spectrophotometry. It has been found that: (i) commercial semiconductor silicon contains less than 1 • 1015 ..."
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The concentration of nitrogen and oxygen in semiconductor silicon and their solubilities in silicon at its melting point have been measured by charged particle activation analysis and infrared spectrophotometry. It has been found that: (i) commercial semiconductor silicon contains less than 1 • 1015 atoms/ cm 3 of nitrogen in the un-ionized state; (ii) the solubility in solid silicon is 4.5 • 1.0 X 10 i5 atoms/cm 3 for nitrogen and 2.75 + _ 0.15 X l0 is atoms/cm ~ for oxygen; and (iii) the solubility in liquid silicon is about 6 X l0 is atoms/cm 3 for nitrogen and 2.20 __. 0.15 • l0 is atoms/cma for oxygen. Thus, the equi-l ibr ium distribution coefficient has been determined to be about 7 X 10-4 for nitrogen and 1.25 + _ 0.17 for oxygen. The solubilities of the two elements are compared with those of other elements, especially carbon, and are discussed thermochemically. After maximum purification of any semiconductor material or metal, carbon, nitrogen, or oxygen almost
