bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable Emittance Electrochemical Devices for Spacecraft Application based on Ionic Liquids Coupled with Conducting Polymers
Authors: Chandrasekhar Prasanna , Zay Brian , Barbolt Scott , Werner Robert , Birur Gajanana , Paris Anthony
Published: August 2009

Variable emittance (ε) is a property useful for external thermal control in future micro- (< 20 kg) spacecraft; current methods, used in large spacecraft, do not work. This contribution describes fabrication, function, performance of thin-film variable emittance electrochromic devices fabricated using an ionic liquid as electrolyte and conducting polymer (CP) as active electrochromic. The spacecraft skins are thin (< 0.5 mm), flexible, lightweight, inexpensive and variable-area. A thin surface film further functions to lower the solar absorptance (α(s), to protect from overheating) and protect from space atomic-O/far-UV. The ionic liquid imparts unique durability to space conditions. Data presented show tailorable ε variations from 0.19 to 0.90, α(s) < 0.3, and nearly indefinite cyclability. Extended thermal vacuum studies (continuous cycling over months under space conditions --- 10-6 Torr vacuum, far-UV) and other studies show excellent durability and resistance to solar wind and atomic-O. Electrochemical properties of the devices are described in detail.
Ionic Liquid Polyoxometalates as Light Emitting Materials
Authors: Ortiz-Acosta Denisse , Purdy Geraldine M. , Scott Brian L. , Bennett Bryan , Muenchausen Ross E. , McKigney Edward A. , Gilbertson Robert , Del Sesto Rico E.
Published: August 2009

The low melting point, negligible vapor pressure, good solubility, and thermal and chemical stability make ionic liquids useful materials for a wide variety of applications. Polyoxometalates are early transition metal oxygen clusters that can be synthesized in many different sizes and with a variety of heterometals. The most attractive feature of POMs is that their physical properties, in particular electrical, magnetic, and optical properties, can be easily modified following known procedures. POM ionic liquids can be obtained by selecting the appropriate cation. Different alkyl ammonium and alkyl phosphonium salts are being used to produce new POM ionic liquids together with organic or inorganic luminescent centers to design light emitting materials. Ammonium and phosphonium cations with activated, polymerizable groups are being used to further polymerize the ionic liquid into transparent, solid materials with high metal densities.
Investigation of the PEO-[C2mim]CF3SO3-LiCF3SO3 Ternary System
Authors: Burba Christopher M.
Published: August 2009

Polymer electrolytes containing ionic liquids have tremendous potential for use in lithium batteries. In this report, the local structure of one family of ionic liquid-based polymer electrolytes (PEO complexed with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, [C2mim]CF3SO3, and lithium trifluoromethanesulfonate, LiCF3SO3) is correlated to trends in the conductivities and thermal properties of the materials. Attention is focused on portions of the ternary phase diagram containing {greater than or equal to}50wt.% PEO. Samples rich in the ionic liquid deliver the highest conductivities, and DSC measurements clearly demonstrate the presence of crystalline PEO, crystalline P(EO)3LiCF3SO3, and [C2mim]CF3SO3-rich domains. Raman spectroscopy is used to estimate the speciation of the CF3SO3- anions in the polymer electrolytes. Samples containing large amounts of LiCF3SO3 are dominated by ion-paired and aggregated CF3SO3- anions, whereas polymer electrolytes containing high fractions of [C2mim]CF3SO3 have an abundance of ion-paired and "free" anions. Implications of the CF3SO3 ion speciation in terms of the total ionic conductivity are discussed.
Low Temperature Operation of the Cell Na/β"-Alumina/S(IV) in AlCl3-NaCl Melt
Authors: Dunstan T Don J. , Caja Josip
Published: August 2009

The cell Na/β"-alumina/S(IV) in AlCl3-NaCl melt had been operated almost exclusively in the temperature range 180o to 250oC. Lower temperature operation was explored using the acidic region of the AlCl3-NaCl phase equilibrium, which has a eutectic at 108oC, and the first step in the S(IV) discharge process (OCV > 4.2 V). When the commonly used low surface area current collector was used in the cathode, cell operation below 150oC led to only partial utilization of cell capacity. However, using a cathode constructed with a high surface area current collector (RVC) and operated exclusively in acidic melts, the cell was cycled down to 120oC. It was operated with essentially full capacity and produced ≈100% coulombic efficiency. Energy efficiency at 120o was 87%. Cell operation at and below 115oC led to incomplete and irreproducible discharges. Low temperature operation of this cell can minimize or eliminate corrosion of cathode seal components and extend cell life-time. Because of these favorable properties this cell can find applications in energy storage as well as in downhole oilfield tools.
Solid State Electro-Reduction in Liquid Salts
Authors: Chen George Z.
Published: August 2009

The manuscript provides an overview of the recent work from the author and co-workers in electro-reduction of solid metal compounds, mostly oxides, to the respective metals and alloys in various liquid salts.
Optimization of the FFC Cambridge Process for NiTi Production
Authors: Jackson Benjamin K. , Jackson Martin , Dye David , Inman Douglas , Dashwood Richard
Published: August 2009

The FFC Cambridge process is ideal for NiTi production, as it avoids the Ni segregation associated with pyrometallurgical routes to manufacture NiTi, and is able to produce a homogenous low-oxygen product. The process involves the direct electrodeoxidation of NiTiO3 (first stable oxide to form upon mixing and sintering of NiO and TiO2) to NiTi in a molten CaCl2 salt bath. This work builds on previous literature that has elucidated the reduction pathway by investigating the effect of reduction temperature and current collector material on the microstructure of the final reduction product. It was found that the use of a Ni current collector caused Ni-enrichment at the surface of the product, stabilizing the high temperature B2 cubic form to room temperature. Ni-rich phases Ni4Ti3 and Ni3Ti were observed after 24h reductions. The former is favoured at higher reduction temperatures, and the latter at lower temperatures. Mechanisms for formation are proposed.
Influence of Bath Composition on Ti Electrolysis in CaF2-CaO-TiO2 Melt
Authors: Takenaka Toshihide , Sugawara Mitsuru , Matsuo Hidetaka , Matsuyama Akihiro , Kawakami Masahiro
Published: August 2009

Ti electrolysis by using a DC-ESR unit was performed in a CaF2-CaO-TiO2 bath, and the influence of the bath composition was discussed. Ti metal in liquid was electrodeposited though some impurity elements were contained. The cathodic current efficiency strongly depended on the bath composition, and reached about 25% in the bath where the molar ratio of CaO to TiO2 was 1.5. The consumed electric power was also affected by the bath composition so that the close relationship between the cathodic current efficiency and the electric power was seen. The influence of the bath composition was considered due to the change in the species in the bath, and Ca3Ti2O7 seemed suitable for Ti deposition.
Titanium Production from Oxycarbide Anodes
Authors: Kjos Ole S. , Haarberg Geir Martin , Martinez Ana Maria
Published: August 2009

The aim of this work is to investigate the new possibilities for electrochemical titanium production as a way of reducing the production costs of the primary metal. The oxycarbide process is a process which involves electrodeposition of Ti at a cathode substrate, and using anodes of a TiC-TiO solid solution made from TiO2 and C. It looks promising, with cheap raw materials, and with a simpler production route than today's process.
Electrolytic Reduction of Solid SiO2 in Molten CaCl2 for the Production of Solar-grade Silicon
Authors: Nohira Toshiyuki , Kani Naoya , Tsuda Tetsuya , Hagiwara Rika
Published: August 2009

The direct electrolytic reduction of solid SiO2 has been investigated in molten CaCl2 at 1123 K aiming at the production of solar grade Si. The target impurity levels for Si in the present study were calculated from the acceptable impurity levels for SOG-Si and the segregation coefficients for the impurity elements. New types of SiO2 contacting electrodes, in which SiO2 directly contacts with only Si, were devised to reduce metal contaminations in the produced Si. By using the new SiO2 contacting electrodes and a quartz vessel, most of the metal impurities were significantly reduced to be below the target levels. When NH4OH/H2O2/H2O, HCl/H2O2/H2O and HF/H2O2/H2O were used as a cleaning solution, remaining CaCl2 and some metal impurities in the produced Si were removed effectively. A basket type electrode was also tested for the reduction of granular SiO2.
Production of Tantalum Fine Powder by Reduction of Tantalum Chloride with Zinc
Authors: Hoshino Yosuke , Takeda Osamu , Hoshi Masayoshi , Sato Yuzuru
Published: August 2009

Reduction of tantalum chloride (TaCl5) with metallic zinc (Zn) was studied by means of injecting TaCl5 into NaCl-LiCl or LiCl-KCl molten salts together with the carrier gas (Ar) through the injection tube. Experiments were carried out in the temperature range of 673-973K. As the reaction and deposition was limited in the molten salts as a reaction medium, recovery of the product was easier compared with the past study in which gas phase was used as a reaction medium. Tantalum fine powder with primary particle smaller than 1μm was obtained in any condition. Also the particle was much sintered compared with those from the gas phase reaction.
Direct Reduction of Liquid V2O5 in Molten CaCl2
Authors: Oka Yuichi , Suzuki Ryosuke O.
Published: August 2009

An alternative process of the reduction of V2O5 was studied. It consists of thermochemical and electrochemical reactions in molten CaCl2 + CaO. V2O5 is thermochemically reduced by Ca. The by-product CaO is electrolyzed. Liquid V2O5 was reduced to vanadium metal through intermediate CaV2O4, and oxygen concentration was 1860ppm at minimum. By deoxidation of the sample with a smaller specific surface area, the lowest oxygen concentration, 460ppm, could be achieved. A major component of ejected gas from the anode was CO2 at the initial stage and CO at the later stage. O2 gas was not detected because its concentration was lower than detection limit.
The Role of Chromium in the Hot Corrosion of Metals
Authors: Rapp Robert A. , Otsuka Nobuo
Published: August 2009

The accelerated oxidation of metals and alloys by a thin surface film of fused salt is controlled by the local salt (acid-base) chemistry and oxidizing potential at the salt/scale interface, as can be monitored using ec surface probes. The solubility of chromium oxide in fused sodium sulfate as a function of melt chemistry at 1200K is accurately known, with chromate ions as the dominant solute at high oxygen activities, but chromite ions dominate at low oxygen activities. Since the chromia solubility increases with increasing oxygen activity, solid chromia is not expected to precipitate out in the salt film during hot corrosion. Serving as a strong acid solute, the formation of chromite or chromate anions can serve as a buffer for the melt chemistry at the scale/salt interface. Chromite ions would be formed using the oxide ions released by less acidic oxides, e.g. CoO, NiO, FeO, etc., thereby preventing the shift toward high local basicity, sulfide formation, and oxide dissolution/reprecipitation. Furthermore, chromate ions can precipitate back onto reducing sites (scale grain boundaries and flaws) on the alloy surface to block its contact with the salt.
A Comparison of the Behavior in Molten Sulfate of Oxidized and Carburized Type 304 Austenitic Steel over 2000 Hours and the Quantitative Analysis of Corrosion Products in the Melt by a Novel Treatment of Their Absorption Spectra
Authors: Griffiths Trevor R. , Phillips Nicolas
Published: August 2009

Our aim was to compare and quantify thin film hot corrosion by sulfate at 650{degree sign}C on oxidised and carburised type 304 austenitic steel. A new approach for a novel new technique for the analysis of the thin film deposits is reported. Salt samples were typically few hundred milligrams and made up to 10 ml in acid solution. Accurate Beer-Lambert analyses are not normally possible when the solution contains elemental concentrations of Fe, Cr and Ni below 1 g.dm-3. An accurate fibre optic spectrometer recorded absorption spectra digitally. Absorbance values were low but, on amplifying, the charge transfer edge of Fe(III) showed the presence of overlapping bands characteristic of Cr(III) and Ni(II). By a series of mathematical smoothing and derivative analysis procedures and band "stripping" it was possible to obtain reliably the known individual transition metal spectra plus their concentrations. Carburised specimens were attacked approximately twice as fast as pre-oxidised specimens.
A Study of Uranium(V) Species in Alkali Chloride Melts
Authors: Volkovich Vladimir A. , Aleksandrov Denis E. , Vasin Boris D. , Khabibullin Timur K. , Polovov Ilya B. , Griffiths Trevor R.
Published: August 2009

Reactions leading to the formation of uranyl(V) species in fused alkali chlorides were studied. The reactions investigated include thermal decomposition of uranyl(VI) chloride in alkali chloride melts, electrochemical and chemical reduction of UO22+ ions in LiCl, 3LiCl-2KCl, NaCl-KCl and NaCl-2CsCl melts at 550-850 oC. Elemental tellurium, palladium, silver, molybdenum, niobium and zirconium were tested as the reducing agents. The outcome of the reaction depends on the electrochemical properties of the reductant.
Electrochemical and Spectroscopic Properties of Tellurium in Fused Alkali Chlorides
Authors: Volkovich Vladimir A. , Kabaev Georgii K. , Polovov Ilya B. , Vasin Boris D. , Griffiths Trevor R.
Published: August 2009

The electrochemical and spectroscopic properties of tellurium were studied between 823 and 1123 K in alkali chloride melts based on 3LiCl-2KCl, NaCl-2CaCl and NaCl-KCl mixtures using potentiometry, cyclic voltammetry, anodic and cathodic polarization and absorption spectroscopy. Tellurium electrode potential values were measured at Te concentrations between 0.0006 and 0.008 mole fraction. Only Te(II) ions are present in chloride melts in the equilibrium with tellurium. Reactions of Te and Ag2Te with Cl2 and HCl were studied spectroscopically in NaCl-2CsCl melt at 823 K.
Levitation / CO2 Laser Melting and Glass Formation in MgO Rich Mixtures with SiO2: Raman Spectra and Structure
Authors: Kalampounias Angelos , Nasikas Nectarios , Papatheodorou George N.
Published: August 2009

Container-less levitation techniques and CO2 laser heating were used to melt SiO2-MgO mixtures and prepare a series of glasses with compositions from enstatite MgSiO3 to forsterite Mg2SiO4 in intervals of ~0.02 mol% SiO2. Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged SiO4 tetrahedral (Qi, species analysis), undoubtedly shows that bridging oxygens are present in all glass studied even in the limit of the forsterite composition. The Boson peak frequency is invariant and the vibrational modes of the Qi species do not reflect any abrupt structural changes with composition. It is suggested that the forsterite forms an ionic-like glass arising from a very fragile liquid.
Corrosion of Constructive Materials in Niobium-containing Melts
Authors: Abramov Alexander V. , Polovov Ilya B. , Volkovich Vladimir A. , Rebrin Oleg I. , Griffiths Trevor R.
Published: August 2009

The corrosion resistance of nickel, molybdenum and two types of stainless steel (12H18N10T (analog of AISI321) and AISI316L) were investigated in molten salt media. Corrosion tests were carried out in NaCl-KCl equimolar mixture and niobium-containing mixture NaCl-KCl-NbCln employing gravimetric analysis, metallography, potentiometry, polarization and voltametry. It was shown that molybdenum metal is most stable material both in pure alkali chloride and in niobium-containing electrolytes. The corrosion processes of studied materials under inert atmosphere have electrochemical nature.
Standard Rate Constants of Charge Transfer for the Nb(V)/Nb(IV) Redox Couple in CsCl-K2NbF7 Melt
Authors: Popova Anna , Kuznetsov Sergey A.
Published: August 2009

The electrochemical behavior of the Nb(V)/Nb(IV) redox couple in in the CsCl-K2NbF7 melt was studied at 973-1123 K by cyclic voltammetry. The standard rate constants of charge transfer (ks) on platinum and glassy carbon electrodes for Nb(V)/Nb(IV) redox couple were calculated on the basis of cyclic voltammetry data. It was found that ks increased with increasing temperature and values of ks obtained at platinum electrode were higher than at a glassy carbon electrode. The values of constants testify that the redox process proceeds quasi-reversibly, mostly under diffusion control.
Potentiodynamic Polarization of Platinum and Aluminum in AlCl3-[P14,6,6,6]Cl Melts
Authors: Vaughan James , Dreisinger David
Published: August 2009

Ionic liquids (ILs) are being considered for a wide range of applications including as a medium for the electrowinning and refining of reactive metals such as aluminium. The electrochemical characteristics of the aluminum chloride - trihexyl(tetradecyl) phosphonium chloride (AlCl3-[P14,6,6,6]Cl) system are explored in this paper. Cyclic voltammograms using a platinum working electrode are presented over a wide range of AlCl3 concentrations (XAlCl3 = 0, 0.3, 0.5, 0.6, 0.67 mole fraction). The potentiodynamic polarization of aluminum were measured in the XAlCl3 = 0.67 melt at 323, 355, 375, 402 and 423 K. The [P14,6,6,6]Cl used was of commercial purity; one of the main impurities is HCl. The presence of HCl in the melt detracts from the current efficiency of aluminum electrodeposition.
Application of the Electrochemical Quartz Crystal Microbalance for the Investigation of Metal Depositions from Ionic Liquids
Authors: Ispas Adriana , Bund Andreas , Endres Frank
Published: August 2009

Electrochemical quartz crystal microbalance was successfully applied to study the deposition of Ta from ionic liquids and for estimating the activation energy of viscosity of the 1-butyl- 1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [P1,4]TFSA ionic liquid. It could be shown that Ta electrodeposition occurs in several steps and that the deposited species were not always elemental Ta. Higher temperatures favoured the deposition process of pure Ta. Furthermore, the cation of the ionic liquid could influence the deposition process.
EQCM Measurement of Ag(I) / Ag Reaction in an Imide-type Room-temperature Ionic Liquid
Authors: Serizawa Nobuyuki , Katayama Y. , Miura Takashi
Published: August 2009

Ag deposition was investigated using separately-excited (passive technique) EQCM in a room-temperature ionic liquid. The mass changes during silver deposition and dissolution were observed with the current efficiencies of nearly 100 % during potential sweep, constant potential step, and constant current step experiments. The product of the viscosity and density of the electrolyte near the electrode, ηρ, can be estimated by the resonance resistance, which can be monitored simultaneously with the resonance frequency. The change in the ηρ value during Ag deposition was consistent with the simulation results of the concentration profile of Ag(I) near the electrode. During outer-sphere electron transfer reaction between Fc+ and Fc, no significant change in the mass and the ηρ value was observed.
Electrochemical Production of Sm-Co Thin Film in Molten LiCl-KCl System
Authors: Takeda Osamu , Ideno Takashi , Nakamura Eiji , Sato Yuzuru
Published: August 2009

Production of Sm-Co thin film by using molten salt electrolysis was investigated in order to reveal the factors dominating film formation in this study. Basic electrochemical behavior of Sm ion in molten LiCl-KCl was analyzed by using inert W electrode. The behavior of Sm ion on Co electrode was also analyzed compared with that on W electrode. Based on those fundamental investigations, Sm-Co thin film was produced by using molten salt electrolysis, and its structure was analyzed. As a result, redox reaction of Sm3+/Sm2+ and reduction of Li+ was observed on W electrode. Formation of intermetallic compound of Sm and Co as well as the redox reaction and the reduction was observed when Co electrode was used. Sm-Co thin film (SmCo2) was successfully obtained by using the molten salt electrolysis.
Influence of Some Factors upon Electrodeposition of Liquid Li and Mg
Authors: Takenaka Toshihide , Shigeta Kouji , Masuhama Hiroshi , Kubota Kazushi
Published: August 2009

Change in the morphology of electrodeposited Mg with codeposition of La has been investigated in a MgCl2-NaCl-CaCl2 bath containing LaCl3. The morphology of Mg electrodeposit remarkably changed with the codeposition of a small amount of La, and the electrochemical behaviors were influenced consequently. These results suggested the possibility that the efficiency of electrolysis could be improved by the codeposition. In this study, metal fog formation of Li has been also studied in a LiCl-KCl bath with reference to the formation in pure LiCl melt or in equi-molar NaCl-KCl melt. The results suggested that the mechanism of the metal fog formation in the Li electrolysis and the Na electrolysis was different. Bassed on the consideration of the formation mechanism, the ways to control the metal fog formation were discussed.
Electrodeposition of Aluminum from Ionic Liquids
Authors: Yosimura Kouichi , Miyahara Keita , Matsunaga Morio
Published: August 2009

Electrodeposition of aluminum was studied in three hydrophobic ionic liquids, trimethylhexylammonium bis(trifluoromethylsulfonyl)imide (TMHA-TFSI), trimethylpropylammonium bis(trifluoromethyl -sulfonyl)imide (TMPA-TFSI), 1-n-butyl-N-methylpyrrolidinium bis (trifluoromethylsulfonyl)imide (BMP-TFSI). Bright deposits were obtained only in the BMP-TFSI melt containing AlCl3 with low current densities, while gray deposits were obtained from the TMPA-TFSI melt. In the BMP-TFSI melts, the deposits became black and less adhesive with an increase in current density. The current efficiency for the aluminum deposition was quite high in the BMP-TFSI melt, and the thick deposits such as 20μm could be obtained. The effects of the aluminum chloride concentration were also examined.
Study of Processes of Pt, Pd, Rh Electrodeposition as Powders or Coatings from Low-Temperature Carbamide, Acetamide, Imidazol-Based Melts
Authors: Savchuk Anastasiya V. , Tumanova Nelly , Kochetova Svetlana
Published: August 2009

It has been shown that low-temperature melts : carbamide-NH4Cl (1200 C), acetamide- NH4Cl (800 C), carbamide-imidazole- NH4Cl (700C) and thiocarbamide- NH4Cl (1600 C) can be used to study the electrochemical behaviour of noble metals (Pt, Pd, Rh). The mechanism and kinetics of electrode processes have been determined, passivation of electrodes and complex formation of metal ions with melt constituents have been established. Methods for the electrodeposition of metals as powders and coatings, macro - and nanostructure have been developed.
Cu-Sn Alloy Metallization of Polymer through Reduction-Diffusion Method Using Ionic Liquid Bath at Medium-Low Temperature
Authors: Ito Akira , Murase Kuniaki , Ichii Takashi , Sugimura Hiroyuki
Published: August 2009

Cu-Sn alloy metallization of a non-conductive epoxy substrate was demonstrated through successive electrochemical processes: (i) conventional electroless Cu deposition on the substrate and (ii) electrochemical alloying of the resulting Cu layer with Sn through a reduction-diffusion method using an ionic liquid bath at 150 åC. The resultant Cu-Sn alloy layer, composed of Cu6Sn5 and/or Cu3Sn intermetallic phases, was compact, smooth, and adhesive. Dependence of the intermetallic phases on applied potential and alloying time was also examined to discuss the alloy formation mechanism, demonstrating that Cu-Sn alloy layers composed of desired phases could easily be prepared by controlling these parameters.
Effect of Electrolyte Composition and Anode Material on Current Efficiency for NF3 Formation in Electrolytic Synthesis using Diamond Anode
Authors: Nishida Akira , Kobayashi Atsushi , Omori Hiroyuki , Inaba Minoru , Uno Masaharu , Nishiki Yoshinori , Furuta Tsuneto , Tasaka Akimasa
Published: August 2009

The current efficiency for NF3 formation was investigated using Boron-Doped Diamond (BDD) anode in NH4F·nHF melts. It depended on both the current density and the NH4F-concentration. The best current efficiency was obtained at 40 mA/cm2 and the NH4F-concentration of 33.3 mol% (the NH4F·2HF melt), and its value was 72.4%.
Molecular Electrochemistry and Redox Catalysis in Ionic Liquids
Authors: Barhdadi Rachid , Comminges Clement , Doherty Andrew P. , Marley Eunan , Troupel Michel , Pentlavalli Sreekanth
Published: August 2009

The reductive electrochemistry of substituted benzophenones in [Bmpy][NTf2] and [Bmim][NTf2] ionic liquids is presented where electrochemistry in [Bmpy] medium results in reversible formation of the radical anion and the dianion species indicating that neither protonation nor ion pairing occurs; whereas in [Bmim], its protic nature results in radical anion protonation leading to an ECE or a DISP1 post electron transfer process and thus irreversibility. The mediated oxidation of alcohols by TEMPO is also presented along with a mechanism / kinetic model involving a rate-controlling pre-equilibrium process which generated the electroactive alcoholate species. The ability of electrochemistry to inform us about the physiochemical nature of ionic liquids, as well as ionic liquids' ability to facilitate and enable electrochemistry, is also discussed.
Electrochemical Behavior of Copper(I) Oxide in Urea-Choline Chloride Room-Temperature Melts
Authors: Tsuda Tetsuya , Boyd Laura , Kuwabata Susumu , Hussey Charles L.
Published: August 2009

The physicochemical properties of urea-salt based melts such as the 66.7-33.3 mol % mixture of urea and choline chloride are com-parable to those of many room-temperature ionic liquids. Copper (I) oxide dissolves in this melt to form complex ions. The standard heterogeneous rate constants and transfer coefficients for the Cu(I)/Cu(II) and Cu(I)/Cu(0) electrode reactions were determined in this melt at both glassy carbon and platinum electrodes by using cyclic and rotating disk electrode voltammetric methods. The elec-trodeposition of copper was investigated on glassy carbon by using chronoamperometry. Comparison of the dimensionless data with the corresponding theoretical models for three-dimensional nuclea-tion indicated that the copper nucleation process was intermediate between the limiting cases for instantaneous and progressive nuc-leation. This suggests that nucleation of copper on glassy carbon proceeded at a finite number of active sites.
Electrochemical Studies of the Fries Rearrangement in Ionic Liquids
Authors: Cheek Graham T.
Published: August 2009

The Fries rearrangement of phenyl benzoate has been studied in the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI BF4). Addition of the proton acid triflic acid was found to shift the reduction potential of phenyl benzoate from -2.0V to -1.1V vs Ag/AgCl, implying protonation of phenyl benzoate by triflic acid. After 1 day, however, the phenyl benzoate reduction potential shifted back to its original value, suggesting that triflic acid slowly reacts with the ionic liquid.
Electrical Double Layer Structure at Bi(111)|1-ethyl-3-methyl-imidazolium Tetrafluoroborate Interface
Authors: Siinor Liis , Lust Karmen , Lust Enn
Published: August 2009

The electrical double layer structure at Bi(111)|1-ethyl-3methyl-imidazolium tetrafluoroborate interface has been studied using cyclic voltammetry and electrochemical impedance. The nearly capacitive behavior has been established in the electrode potential region -0.9 < E < -0.5 V (vs. Ag|AgCl in aq. 4M KCl), where the fractional exponent of the constant phase element exceeds 0.96. Outside this potential region the adsorption of ions with the partial charge transfer takes place. The faradic process is possible at E <= -1.1V. The high-frequency compact layer capacitance depends weakly on potential and has minimum value near zero charge potential (-0.65 V).
Electrochemical Behavior of Ferrocenylthiol / Alkanethiol Binary SAM in Ionic Liquids
Authors: Sun Qing-Wei , Murase Kuniaki , Ichii Takashi , Sugimura Hiroyuki
Published: August 2009

The redox behavior of the binary self-assembled monolayers (SAMs) of 11-ferrocenyl-1-undecanethiol and 1-undecanthiol on gold substrate was investigated in an ionic liquid (IL), trimethyl-n-hexylammonium bis[(trifluoromethyl)sulfonyl]amide (TMHA-Tf2N) and HClO4 aqueous solution. It was found that the total amount of charge for the redox of ferrocenyl groups in the ionic liquid is about 70% of that in the HClO4 solution, indicating that less number of ferrocenyl groups are involved in the redox in the ionic liquid. A set of impedance measurements indicated that the electron transfer rate between the SAMs and the substrate is lower in the ionic liquid than that in aqueous solution, suggesting a slow and incomplete reconstruction of TMHA-Tf2N ions at the SAMs/ionic liquid surface.
Electrochemical Behaviour of Depolarized Reducing Gas Anodes in Molten Salts
Authors: Xiao Saijun , Mokkelbost Tommy , Haarberg Geir Martin , Ratvik Arne Petter , Kvello Jannicke Hatlo , Osen K. S. , Zhu Hongmin
Published: August 2009

Preliminary experiments were carried out to test the use of CH4 (g) for depolarizing of NiFe2O4 based anodes during electrolysis in molten CaCl2-NaCl (60-40 mol%) containing dissolved CaO. Electrochemical studies of the cathodic reduction of dissolved silver ions were done by using cyclic voltammetry.
Electrochemical Deposition of Metallic Nanowires as a Scanning Probe Tip
Authors: Motoyama Munekazu , Dasgupta Neil P. , Prinz F B.
Published: August 2009

This paper describes Ni electrodeposition for producing metallic nanowires as a nanoprobe tip. A polycarbonate porous membrane was used as a template for the growth of nanowires on a Si AFM probe tip. A focused ion beam (FIB) was used to deposit a thin Pt layer as the cathode with a controlled small area on the tip apex and the underlying membrane surface. The produced nanowire-AFM probe showed compatibility with a conventional AFM system. We also demonstrated deposition of Al2O3 by atomic layer deposition (ALD) into the template with the aim of decreasing the nanowire diameters.
Measurement of the SiCl4 Diffusion Coefficient in a Room-Temperature Ionic Liquid by an Optical Moiré-Pattern Technique
Authors: Nishimura Yusaku , Nishida Tetsuo , Fukunaka Yasuhiro , Miranda Caetano R. , Nohira Toshiyuki , Hagiwara Rika
Published: August 2009

The diffusion coefficient of SiCl4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl)imide was estimated by means of an optical moiré-pattern technique. It revealed that the diffusion coefficient varies with concentration from 0.79 × 10−6 cm2 s−1 at 0.1 mol L−1 to 1.05 × 10−6 cm2 s−1 at 0.4 mol L−1 at 298 K. This technique is superior to any other methods to measure the diffusion coefficient especially in the following point. The conventional electrochemical methods such as chronopotentiometry and chronoamperometry yield just a single effective diffusivity over the similar concentration range. On the other hand, the moiré-pattern method is so powerful that just one experiment is adequate to estimate the concentration-dependent diffusivity because the local diffusivities at the points with different concentrations can be measured at once.
Correspondence between Experiment and Theory of Bulk Electrocrystallisation at Solid Electrodes in Aqueous Electrolyte
Authors: Andersen Jens E.
Published: August 2009

A model of electrodeposition and electrodissolution at electrode surfaces in aqueous solution is presented. The description is based on the assumption that redox reaction of water is the more important process controlling the electrode kinetics. Chronoamperometric measurements and experiments of cyclic voltammetry indicate that the current fundamentally is proportional to inverse time. It was proposed that redox-active species different from water never touch the surface but they predominantly interact with surface-active hydrogen or oxygen formed at the surface by redox processes of water. An excellent correspondence was found between the number of ideal-gas molecules in a monolayer at the electrode surface and the charge required, as to dissolve one monolayer of electrodeposited metal. The linear relation between standard enthalphy of metal-oxide formation and standard-reduction potential shows that metal oxide formation at the electrode corresponds to oxidation of a metal in an atmosphere of oxygen.
One-Step Through-Mask Electrodeposition of a Porous Structure Composed of Manganese Oxide Nanosheets
Authors: Nakayama Masaharu , Fukuda Masaki
Published: August 2009

Potentiostatic electrolysis of a mixed aqueous solution of Bu4NBr (Bu = C4H9) and MnSO4 at +1.0 V (vs Ag/AgCl) on Pt electrode resulted in the oxidation of Br- and Mn2+ ions, which was followed by the deposition of insulating crystals of bromide salt of Bu4N+ and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals with water left a well-dispersed porous texture composed of manganese oxide nanosheets.
The Effect of Substrate Shape and Temperature on the Liquid Cluster Deposition using Molecular Dynamic Simulation
Authors: Go Sun-Mi , Jeong Heung-Cheol , Shibahara Masahiko , Choi Gyungmim , Kim Duckjool
Published: August 2009

Molecular dynamic simulations have been carried out to understand the effect of the shape of nano-structure substrate on the liquid cluster wettability at various temperature conditions. The Lennard-Jones potential was applied to mono-atomic molecules of argon as the liquid cluster and platinum as the nano-structure substrate. The shape of nano-structure substrate and the change of substrate temperature have a great effect on the accumulation ratio which is defined as the ratio of the height to the width of the accumulated liquid cluster. The formation change of substrate roughness affected to the behavior and wettability of liquid cluster. The substrate roughness and substrate temperature seem to have effect on the accumulation ratio. Liquid cluster well accumulated at the width of nano-structure substrate wider than narrow. The accumulation ratio decreased when temperature of nano-structure substrate increased. This paper could have better coating process by using high substrate temperature and substrate roughness.
Immobilization of Cationic Porphyrin between Multilayers of Manganese Oxide during Their Electrochemical Assembly
Authors: Hoyashita Ryo , Nakayama Masaharu
Published: August 2009

Potentiostatic electrolysis of a mixed aqueous solution of MnSO4 and cationic porphyrin at +1.0 V (vs Ag/AgCl) on a Pt electrode resulted in the deposition of layered manganese oxide. Porphyrin molecules are intercalated between Mn oxide layers as a cation form, resulting in a stacking with a repeating periodicity of 0.82 nm.
Formation and Reaction of Pyridinethiolate Self-Assembled Monolayers on Au/Si Surface in Aromatic and Aliphatic Ionic Liquids Studied by SEIRAS
Authors: Nishiyama Katsuhiko , Seriu Hiroshi , Taniguchi Isao
Published: August 2009

Ionic liquids (ILs), which are liquid at room temperature and consisted from only ions, are widely studied for their application to capacitors, solvents for fuel cells, and sensors due to their chemical or physical properties. it is very important to clear the structure and surface properties at interfaces. In particular, adsorption of ILs on a bare or modified electrode surface or m plays an important role for their functions. In this study, we report effect of electrode potential on adsorption of IL molecules and formation processes of self-assembled monolayer of aromatic thiols in aromatic and aliphatic ILs by surface enhanced infrared spectroscopy (SEIRAS).
Structural Change in 4-Pyridineethanethiolate Self-Assembled Monolayers on Au(111) Induced by Protonation of Pyridine Ring in Electrolyte Solutions
Authors: Nishiyama Katsuhiko , Tsuchiyama Masashi , Seriu Hiroshi , Yoshimoto Soichiro , Taniguchi Isao
Published: August 2009

Self-assembled monolayers (SAMs) of 4-pyridineethanethiol (4-PyEtS) formed on a Au surface was investigated by cyclic voltammetry (CV), surface enhanced infrared spectroscopy (SEIRAS), and in situ scanning tunneling microscopy (STM). On the basis of reductive desorption for 4-PyEtS on Au(111), the peak potential was observed at -0.86 V vs. Ag/AgCl (sat. KCl). The surface excess was calculated to be 5.4 × 10-10 mol cm-2 from the CV. High-resolution STM images revealed that p(5 × √3 R−30å) lattice including two molecules was found in 0.1 M NaClO4, whereas the 4-PyEtS-SAMs formed p(10 × √3 R−30å) lattice constituted from four molecules in 0.05 M HClO4. By the analysis of SEIRA spectra, the b axis of pyridine ring of 4-PyEtS-SAMs formed on an evaporated Au film electrode in 0.1 M NaClO4 was tilted to the electrode. In contrast, that in 0.1 M HCl was parallel to the surface.
Supramolecular Nanostructure of Porphyrin Diacid on Sulfate/Bisulfate Adlayer Formed on Au(111)
Authors: Yoshimoto Soichiro , Sawaguchi Takahiro
Published: August 2009

Cationic tetraphenyl porphyrin with two carboxyphenyl moieties in cis-position (cis-H4DCPP2+) was investigated to control the structure of the two-dimensional supramolecular assembly in 0.05 M H2SO4. In situ scanning tunneling microscopy (STM) images revealed the formation of supramolecularly organized nanostructures of cis-H4DCPP2+ such as dimer, trimer, and tetramer on the (√3 × √7) sulfate/bisulfate (SO42-/HSO4-) adlayer, suggesting the importance of both electrostatic interaction between cationic porphyrin core and SO42-/HSO4- adlayer and the hydrogen bond formation between carboxyl groups of the nearest neighbor cationic porphyrins. In contrast, when 0.1 M HClO4 was used as an electrolyte solution, only a disordered array was observed. The results indicate that the (√3 × √7) SO42-/HSO4- adlayer formed on Au(111) plays a significant role as a template in the control of electrostatically assembled cis-H4DCPP2+.
Molecular Simulation Approach to the Effects of Additives in Electrodeposition Process
Authors: Nishimura Shuichi , Kaneko Yutaka , Hiwatari Yasuaki , Ohara Katsuhiko , Asa Fujio
Published: August 2009

The leveling effect of additives in electrodeposition has been studied using a simplified model for inhibitors by the combined method of molecular dynamics and Monte Carlo simulations. The additive molecule is assumed to be a spherical particle which has an action range around its center in which the metal deposition is inhibited. The interaction between the additives and the electrode is modeled by a simple Lennard-Jones potential. The dependence of the leveling efficiency on the action range and the interaction energy has been studied by a series of simulations of filling grooves. It is shown that high throwing power is obtained for the additives with large interaction energy with the electrode.
Depositing Mechanism of Metal Oxide Thin Film in the Liquid Phase Deposition Process
Authors: Mizuhata Minoru , Saito Yasuhito , Takagi Mariko , Deki Shigehito
Published: August 2009

The equilibrium reaction of fluorosilicate ion (SiF62-) in the LPD method was investigated by the measurement of UV and IR spectroscopies, Raman spectroscopy. These measurements were carried out by adding the F- scavenger such as H3BO3 and Al metal which shifts the equilibrium reaction. Also, the concentration of Si dissolving species was measured after addition of fine alpha-Al2O3 powder. These species were estimated to be involved in the LPD process as intermediates and important for controlling the deposition process of metal oxide.
Simplified Electrochemical Engineering Modelling of the Species Concentration Profiles at an Electrode
Authors: Mandin Philippe P. , Cense Jean-Michel , Fukunaka Yasuhiro , Alkire Richard C.
Published: August 2009

Electrochemical processes such as electrodeposition and two-phase electrolysis involves numerous transport and reactivity coupled phenomena. Concerning the associated reactive problem which involves numerous kinetic constants, not always all identified, the mathematical problem is stiff. The present paper shortly presents the idea developped in more extended papers of species profiles calculation under the partial local thermodynamical equilibrium. Strategy and algorithms are given here with the use of the zinc oxide deposition process example.
Understanding Metal Dusting Mechanisms
Authors: Young David , Zhang Jianqiang
Published: August 2009

Examination of iron dusting shows that cementite forms as a layer on the surface and as particles in the overlying coke deposit. On this basis, the mechanism of cementite disintegration is deduced to be one of internal graphite nucleation and growth within the scale. Cementite formation on iron is suppressed by alloying with germanium. Nonetheless, dusting occurs via the direct growth of graphite into the metal, producing nanoparticles of ferrite. This process is faster than dusting via cementite formation and disintegration. Austenitic materials cannot form cementite, and dust via formation of graphite at external surfaces and interior grain boundaries. The coke deposit consists of carbon nanotubes with austenite particles at their tips, or graphite particles encapsulating austenite. TEM studies demonstrate the inward growth of graphite within the metal interior. It is therefore concluded that the mechanism of nickel dusting is one of graphite nucleation and growth within the near surface metal. Alloying copper with nickel strongly represses graphite formation, thereby reducing greatly the overall dusting rate.
Metal Dusting Resistant Alumina Forming Coatings for Syngas Production
Authors: Chun Charlie , Ramanarayanan Trikur
Published: August 2009

Metal dusting corrosion of NiCrAl(Y)-based alumina forming coatings has been simulated in carbon-supersaturated environments (CO-H2) at 650{degree sign}C. Atmospheric plasma spray (APS) and powder plasma welding (PPW) methods have been employed to deposit alumina forming coatings on Inconel 601 substrate alloy surfaces. Since most currently available high temperature alloys are prone to metal dusting, understanding and thereby controlling metal dusting corrosion is key to many operations and developments related to syngas production. The focus of this research is to evaluate the performance of alumina forming coatings under laboratory conditions. In addition to the effect of coating chemistry and microstructure (based on method of application) on the corrosion process, the mechanistic aspects of metal dusting are discussed with particular attention to the stages of microstructure evolution as degradation proceeds.
High-Temperature Corrosion of Austenitic Stainless Steels under CH4-Steam Reforming Atmosphere
Authors: Nanko Makoto , Matsumoto Takumi
Published: August 2009

In this study, corrosion of austenitic stainless steels under CH4-stream reforming atmosphere was investigated at 800ºC. Two kinds of austenitic stainless steels, type 304 (18Cr-8Ni) and 310 (25Cr-20Ni) were exposed into CH4-steam gas mixture before reforming reaction and mainly H2-CO gas mixture after the reforming reaction. Protective Cr2O3 scale was developed on type 304 under the reformed gas and 310 under the both gas mixtures. Corrosion of type 304 under the steam-CH4 gas mixture developed thick duplex scale consisting of Fe2O3/Fe3O4 outer scale and inner scale consisting of (Fe,Cr)3O4 and Cr2O3, which is similar with that formed by steam oxidation. The corrosion rate of type 304 under the reformed gas is also comparable with steam oxidation. Any carburization was not observed in all of the experiments.
Corrosion Behavior of NiAl(1-x)Hfx (x=0...0.2) Alloys in Chlorine Based High Temperature Environments
Authors: Masset Patrick J. , Texier Damien , Schütze Michael
Published: August 2009

Five compositions of (Ni0.5Al0.5)(1-x)Hfx (x=0...0.2) alloys were prepared by centrifugal casting in an inductive furnace. The cast alloys exhibits 3 phases: β-NiAl, NiAlHf (Laves) and Ni2AlHf (Heussler). Their CTEs were found to vary linearly with the hafnium content. Hafnium can be used to adjust the CTE to the substrate CTE. At the same time the prepared alloys are corrosion resistant in chlorine based high temperature environments. For hafnium contents higher than 10 at.%t, it was shown that hafnium addition improves the Cl2 corrosion resistance compared to binary NiAl alloys.
Monitoring of Degradation Process of Alloys and Al Diffusion Coatings under Molten Sulfate Film by Electrochemical Impedance Measurements
Authors: Take Seisho , Suda Yuki , Shirai Takashi , Hasegawa Masato , Itoi Yasuhiko
Published: August 2009

The hot corrosion behaviors of several alloys and Al diffusion coatings were evaluated by electrochemical impedance technique under molten sulfate film with a special designed electrochemical cell. It was found that corrosion resistance of alloys changed greatly with the changing of atmosphere. For alloys, the atmosphere has much greater effect on corrosion behavior under molten salt film than in bulk molten salt. Meanwhile, Atmosphere did not have significant effect on corrosion behavior of Al diffusion coatings probably due to the instant formation of protective aluminum oxide film under any atmosphere tested. More information about changes in aluminum oxide film properties was also obtained by impedance monitoring. Electrochemical technique was proved to be very useful for the evaluation of hot corrosion resistance of both alloys and protective coatings under molten salt film condition.
Oxidation of Ferritic Steels Subjected to Simulated SOFC Interconnect Environments
Authors: Gannon Paul , White Preston
Published: August 2009

Ferritic stainless steel (FSS) 441 with CoMnO coatings were subjected to solid oxide fuel cell interconnect exposures (800{degree sign}C air and dual atmospheres (air/H2)). Oxidation behavior was observed using complimentary analytical techniques. Significant differences in oxidation behavior were observed in samples exposed to dual atmosphere conditions compared with air-only exposures, indicating rapid transport of hydrogen through FSS 441 and its influence on air side corrosion. Observations and interpretations are presented and discussed in context of developing inexpensive and durable SOFC interconnects.
High Temperature Oxidation Behavior of Stainless Steel 441 in Dual Atmosphere - Effects of Flow Rate and Humidity
Authors: Zhao Yu , Fergus Jeffery
Published: August 2009

The effects of flow rate and humidity on the high temperature oxidation behavior of stainless steel 441 in dual atmospheres (wet Ar-5vol% H2│dry or wet air) at 800ºC for 200 hours were investigated. All the oxide scales were composed mainly of a surface (Mn, Cr, Fe)3O4 spinel layer and a Cr2O3 sublayer. The higher flow rate of Ar-5vol%H2 resulted in thicker oxide scales and the formation of Fe2O3 nodules on the air side of sample exposed to a dual atmosphere. In addition, particles with high concentrations of Ti and Nb were found near some of the Fe2O3 nodules. The microstructure of the oxide scales formed in moist air was more compact than that formed in dry air.