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Shunsuke Yagi - One of the best experts on this subject based on the ideXlab platform.

  • local Ph control by electrolysis for zno epitaxial deposition on a pt cathode
    Electrochimica Acta, 2012
    Co-Authors: Shunsuke Yagi, Yusuke Kondo, Yuichi Satake, Atsushi Ashida, Norifumi Fujimura
    Abstract:

    Abstract The epitaxial deposition of an oxide semiconductor ZnO thin film was demonstrated on a Pt(1 1 1)/sapPhire(0 0 0 1) cathode by local Ph control in the vicinity of the cathode. The local Ph near the cathode was increased by the selective reduction of NO 3 − ions, resulting in the deposition of a ZnO thin film only on the cathode surface by hydrolysis. The Ph distribution near the cathode during electrolysis was calculated using a 1-dimensional discrete model, which is simple but concise and beneficial to expeditiously estimate an appropriate deposition condition in combination with the obtained potential-Ph Diagram of a Zn–H 2 O system. An investigation undertaken using a quartz crystal microbalance revealed that ZnO started to deposit immediately after the application of electrical current at 100 μA cm −2 , and that it grew linearly to ca  . 350 nm over 5000 s, suggesting that the film thickness can be easily controlled by electrolysis time.

  • potential Ph Diagrams for oxidation state control of nanoparticles synthesized via chemical reduction
    2011
    Co-Authors: Shunsuke Yagi
    Abstract:

    In the past, many synthesis methods of nanoparticles have been reported, but the synthesis processes have not been well discussed from the viewpoint of thermodynamics. In this chapter, a general concept using potential-Ph Diagrams is described for oxidation-state control of nanoparticles synthesized via chemical reduction (also called electroless deposition or liquid-Phase reduction). By comparing kinetically determined mixed potential measured in reaction solution and thermodynamically drawn potential Diagrams, e.g., potential–Ph Diagram, it is possible to know “what chemical species is stable in the reaction solution?.” It is predicted from potential-Ph Diagrams that nanoparticles in different oxidation states can be selectively synthesized by controlling the mixed potential. This concept is verified by selectively synthesizing Cu and Cu2O nanoparticles from CuO aqueous suspension via chemical reduction using the concept as an example. The advantage of this chemical reduction method is that abundant nanoparticles can be obtained for a short time by a simple operation. An extremely small activity of Cu2+ aquo ion is achieved by using insoluble CuO powder as a Cu(II) ionic source, which is a key for the synthesis of nanosized particles. The dependency of mixed potential on Ph and temperature is discussed in the verification process. This chapter is written based on the result of the authors’ paper (Yagi et al., 2009) with further detailed information on practical thermodynamic calculation and drawing procedure of potential-Ph Diagrams.

  • oxidation state control of nanoparticles synthesized via chemical reduction using potential Diagrams
    Journal of The Electrochemical Society, 2009
    Co-Authors: Shunsuke Yagi, Hidetaka Nakanishi, Tetsu Ichitsubo, Eiichiro Matsubara
    Abstract:

    A general concept for oxidation-state control of nanoparticles synthesized via chemical reduction has been developed. By comparing kinetically determined mixed potential measured in reaction solution and thermodynamically drawn potential Diagrams, e.g., potential-Ph Diagram, it is possible to know "what chemical species is stable in the reaction solution?." It is predicted from potential Diagrams that nanoparticles in different oxidation states can be selectively synthesized by controlling mixed potential. This concept is verified by selectively synthesizing Cu and Cu 2 O nanoparticles from CuO aqueous suspension via chemical reduction using the concept as an example. The dependency of mixed potential on Ph and temperature is discussed in detail for the selective synthesis of nanoparticles.

T R Mankhand - One of the best experts on this subject based on the ideXlab platform.

  • recovery of valuable metals from cathodic active material of spent lithium ion batteries leaching and kinetic aspects
    Waste Management, 2015
    Co-Authors: Pratima Meshram, B D Pandey, T R Mankhand
    Abstract:

    This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1M H2SO4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh-Ph Diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD Phase identification and the SEM-EDS studies.

  • recovery of valuable metals from cathodic active material of spent lithium ion batteries leaching and kinetic aspects
    Waste Management, 2015
    Co-Authors: Pratima Meshram, B D Pandey, T R Mankhand
    Abstract:

    Abstract This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1 M H 2 SO 4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh–Ph Diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD Phase identification and the SEM-EDS studies.

Pratima Meshram - One of the best experts on this subject based on the ideXlab platform.

  • recovery of valuable metals from cathodic active material of spent lithium ion batteries leaching and kinetic aspects
    Waste Management, 2015
    Co-Authors: Pratima Meshram, B D Pandey, T R Mankhand
    Abstract:

    This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1M H2SO4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh-Ph Diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD Phase identification and the SEM-EDS studies.

  • recovery of valuable metals from cathodic active material of spent lithium ion batteries leaching and kinetic aspects
    Waste Management, 2015
    Co-Authors: Pratima Meshram, B D Pandey, T R Mankhand
    Abstract:

    Abstract This work is focussed on the processing of cathodic active material of spent lithium ion batteries (LIBs) to ensure resource recovery and minimize environmental degradation. The sulfuric acid leaching of metals was carried out for the recovery of all the valuable metals including nickel and manganese along with the frequently targeted metals like lithium and cobalt. The process parameters such as acid concentration, pulp density, time and temperature for the leaching of metals from the cathode powder containing 35.8% Co, 6.5% Li, 11.6% Mn and 10.06% Ni, were optimized. Results show the optimized leach recovery of 93.4% Li, 66.2% Co, 96.3% Ni and 50.2% Mn when the material was leached in 1 M H 2 SO 4 at 368 K and 50 g/L pulp density for 240 min. The need of a reductant for improved recovery of cobalt and manganese has been explained by the thermodynamic analysis (Eh–Ph Diagram) for these metals. Leaching of the valuable metals was found to follow the logarithmic rate law controlled by surface layer diffusion of the lixiviant reacting with the particles. The mode of leaching of the metals from the spent LIBs was further examined by chemical analysis of the samples at various stage of processing which was further corroborated by characterizing the untreated sample and the leach residues by XRD Phase identification and the SEM-EDS studies.

Eiichiro Matsubara - One of the best experts on this subject based on the ideXlab platform.

  • oxidation state control of nanoparticles synthesized via chemical reduction using potential Diagrams
    Journal of The Electrochemical Society, 2009
    Co-Authors: Shunsuke Yagi, Hidetaka Nakanishi, Tetsu Ichitsubo, Eiichiro Matsubara
    Abstract:

    A general concept for oxidation-state control of nanoparticles synthesized via chemical reduction has been developed. By comparing kinetically determined mixed potential measured in reaction solution and thermodynamically drawn potential Diagrams, e.g., potential-Ph Diagram, it is possible to know "what chemical species is stable in the reaction solution?." It is predicted from potential Diagrams that nanoparticles in different oxidation states can be selectively synthesized by controlling mixed potential. This concept is verified by selectively synthesizing Cu and Cu 2 O nanoparticles from CuO aqueous suspension via chemical reduction using the concept as an example. The dependency of mixed potential on Ph and temperature is discussed in detail for the selective synthesis of nanoparticles.

Toshiaki Kodama - One of the best experts on this subject based on the ideXlab platform.

  • clarification of chemical state for alloying elements in iron rust using a binary Phase potential Ph Diagram and Physical analyses
    Corrosion Science, 2003
    Co-Authors: T. Nishimura, Toshiaki Kodama
    Abstract:

    A binary-Phase potential–Ph Diagram has been investigated to evaluate the chemical stability of various kinds of double oxide rusts (Fe–X) to get a principle for alloy design enhancing the corrosion resistance of steels. It was found that there are the following types of alloying elements enhancing the corrosion resistance of steels in the rust: (1) iron substitution type (Ni), (2) oxide formation type (Al), (3) metallic type (Ru), and (4) oxygen-acid salt type (WO4). X-ray Photoelectron spectroscopy and transmission electron microscopy analyses have been conducted on the rust formed on the low alloy steel in a saline environment. The analytical results were discussed using potential–Ph Diagrams. The iron substitution type and the oxide formation type elements make spinel double oxides with iron. In the corrosion tests, steels added with Ni or Al had high corrosion resistance. Thus it is possible to obtain high corrosion resistance by the creation of spinel double oxide such as Fe2NiO4 and FeAl2O4 in an inner layer. On the other hand it was found that the metallic type and the oxygen-acid salt type elements were not contained into the iron rust. In particular the oxygen-acid salt elements were excluded from the iron rust and concentrated into the defects of the rust. It is suggested that insoluble salts like FeWO4 are formed on the base metal in the defects to act as an anodic inhibitor. Thus, the addition of a small quantity of W gives high corrosion resistance. The penetration of Cl ions can be prevented by the spinel double oxide in an inner layer and the oxygen-acid salt in the defects. In this way, the high corrosion resistance by the addition of these elements can be understood from the potential–Ph Diagram and the Physical analyses.

  • role of nitrogen on the corrosion behavior of austenitic stainless steels
    Corrosion Science, 2002
    Co-Authors: Haruo Baba, Toshiaki Kodama, Yasuyuki Katada
    Abstract:

    Abstract The role of nitrogen in the mechanisms of localized corrosion resistance and repassivation were electrochemically investigated using a nitrogen-bearing austenitic stainless (SUS316L) steel in 0.1 and 0.5 M Na 2 SO 4 solutions and a 3.5% NaCl solution. Almost 100% of the nitrogen compounds dissolved into the bulk solution after crevice corrosion were transformed into NH 3 . That is, the mole amount of ammonia in the solution was approximately equivalent to the mole amount of nitrogen dissolved in the steel. This suggests that NH 4 + consuming H + in the pit controlled the local decrease of Ph and promoted the repassivation. NO 3 –N and NO 2 –N were not detected by chemical analyses in the high potential and thermodynamically stable zone as NO 3 − in the potential–Ph Diagram. The repassivation in nitrogen-bearing SUS316L steel in a 0.1 M Na 2 SO 4 solution was studied using the scratching electrode technique, which measured the partially destroyed passivation films on the steel. This technique showed that nitrogen dissolved in the steel has a strong repassivation capacity.