Aqueous Processing of Materials Laboratory
 
 

Electrochemical processing of functional thin-layered materials using aqueous media

 
 

Our laboratory was inaugurated in 1994 during the reorganization of Department of Materials Science and Engineering. The forerunner of our laboratory was the Electrometallurgy Division of Department of Metallurgy, where we were working on hydrometallurgy, e.g. aqueous thermodynamics, electrowinning, leaching and extraction. In addition to some hydrometallurgical processes, our group is currently interested in the study of electrochemical growth of thin film materials.

 
 
Go to Lab. Page for detail.
 
     
  Academic staff  
 
     
  photo : Uda Tetsuya
Professor : Uda, Tetsuya
 
Research Topics
Current focus is technology and science for intermideate temperature fuel cell which can be operated from 200 C to 500C. Especially, my strong interest is electrochemistry and thermochemistry of fuel cell using solid phosphate and proton conducting oxide as electrolyte.
 
Contact / Office
Room 618, School of Engineering Science Bldg, Yoshida Campus
TEL +81-75-753-5439 / FAX +81-75-753-5284
uda.tetsuya.5e@kyoto-u.ac.jp
     
 
     
 
     
  Photo: Toyoura
Associate Professor Toyoura, Kazuaki
 
Research Topics
・ Development of analysis method on atomic diffusion and ionic conduction in solids
・ Systematic analyses on various proton- conducting oxides
・ Development of first-principles analysis method on surface defect chemistry
 
Contact / Office
Room 630, School of Engineering Science Bldg, Yoshida Campus
TEL +81-75-753-3551 / FAX +81-75-753-5284
toyoura.kazuaki.5r@kyoto-u.ac.jp
     
 
     
 
     
 
Assistant Professor : Hatada, Naoyuki
 
Research Topics
Development of new inorganic electrolytes and electrodes for high-performance fuel cells, and relevant materials processing techniques.
 
Contact / Office
Room 618, School of Engineering Science Bldg, Yoshida Campus
TEL +81-75-753-5445 / FAX +81-75-753-5284
hatada.naoyuki.8u@kyoto-u.ac.jp
     
 
     
 
     
 
Program-Specific Associate Professor :
Han, Donglin
 
Research Topics
Development of intermediate temperature fuel cells, especially protonic conductive ceramic fuel cells (PCFC). Current interest is focused on revealing foundamental properties of proton conductors, such as acceptor-doped barium zirconate, by electrochemical methods and structure analysis.
 
Contact / Office
Room 618, School of Engineering Science Bldg, Yoshida Campus
TEL +81-75-753-5445 / FAX +81-75-753-5284
han.donglin.8n@kyoto-u.ac.jp
     
 
     
     
  Research Topics
     
 
( Index )
Electrodeposition of semiconductors
Electrochemical alloy formation for corrosion-resistant coatings
Composite electrodeposition using nonaqueous and aqueous media
Electrodeposition of metals and alloys from novel ionic liquids
 
     
     
 

Electrodeposition of semiconductors

 
 

Some compound semiconductors are promising materials for the next generation of solar cell devices. Thin layered CdTe has been well-investigated, since the band gap (1.45 eV) is suitable for energy conversion from sunlight to electricity, and has already been produced commercially by an electrodeposition technique using acidic baths, the drawback of which is the low solubility of Te(IV) ions.

To resolve the problem, we have been developing a novel ammoniacal basic bath containing >10 mol dm-3 of Te(IV) ions. Studies are presently directed towards

a) understanding the mechanism of photo-assisted electrodeposition of CdTe
b) investigation of electrical and structural properties of resulting CdTe, and
c) production and characterization of CdS | CdTe solar cell.

 
 
image : Schematic view of CdS | CdTe solar cell
Figure 1   Schematic view of CdS | CdTe solar cell
 
photo : CdTe layer electrodeposited from basic bath   Figure 2
CdTe layer electrodeposited from basic bath
 
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Electrochemical alloy formation for corrosion-resistant coatings

 
 

Ni-Mo alloy plating has been investigated as an alternative to hard chromium coating. Electrodeposition of Ni-Mo alloy is categorized as “induced codeposition,” where molybdenum, which cannot be electrodeposited as an elemental form from aqueous media, is codeposited as an alloy with iron-group hyper-transition metals, i.e. Ni, Co, Fe. Although the mechanism for induced deposition has been a subject of scientific interest, most reports to date deduced the mechanism based on the behavior of alloy deposition or on the characteristics of resulting deposits. There has been no attention to the relationship between the dissolving regime of metal ions in the electroplating bath and alloy deposition behaviors, since electroplating baths, which contains not only metal ions but also complexing agents and some additives, are usually too concentrated and complicated to analyze.

For acidic Ni-Mo plating baths, we determined the distribution of complexed metal ions by factor analysis of a set of their visible absorption and Raman spectra. Here, we have concluded that the domination of 1:1 complexes of Ni(II) and Mo(VI) with citrate is important for alloy deposition.

We are also working on
a) a new alloy formation technique on steel surface by pulse electrolysis and
b) a fast Zn-Cr electrodeposition onto steel at high current densities.

 
 
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Composite electrodeposition using nonaqueous and aqueous media

 
 

Electrochemical formation of aluminium coating is usually conducted using organic solvents and inorganic AlCl3-based molten salts. However, the flammability of organic solvents and the high vapor pressure of AlCl3 are drawbacks of these media.

As an alternative, we selected an AlCl3/dimethylsulfone (DMSO2) molten mixture for the electrodeposition of Al. Such a nonaqueous bath is suitable for composite electroplating of metals with hydrophilic inorganic particles, since agglomeration of the particles sometimes takes place in aqueous electrolytes. Using the AlCl3/DMSO2 bath, we succeeded in obtaining agglomerate-free composite coating of Al with micrometer and nanometer-sized SiO2, SiC, Al2O3, TiB2, and BN particles. Composite electrodeposition using aqueous media is also under investigation.

 
 
photo : SEM micrograph of Al/SiO2 composite coating   Figure 3
SEM micrograph of Al/SiO2 composite coating
 
 
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Electrodeposition of metals and alloys from novel ionic liquids

 
 

Room temperature molten salts, or ionic liquids, are promising solvents for “green chemistry,” owing to their nonflammable and nonvolatile nature. Although electrodeposition of Al and Al-alloys using ionic liquids is well-investigated, hygroscopic chloroaluminate-based liquids employed here are difficult to handle.

To avoid hygroscopicity, ionic liquids comprising fluoroanions have been developed. We are investigating electrodeposition and fundamental electrochemical behaviors of metals in a novel series of hydrophobic ionic liquids synthesized by a combination of aliphatic ammonium cations and amide anion.

It was found that Cu, Ni, Zn, and Mg can be electrodeposited from trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf2N) liquid, which has a wide electrochemical window of 5.6 V.

 
     
 
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