Journal of MMIJ

Special Edition for Advanced Materials; Recent Developments in Environmental and Energy Materials

Published: May 01, 2012 Updated: May 01, 2012

Displaying 1-6 of 6 articles

Volume 125 (2009) Issue 6_7 Pages 369-374 Published: May 01, 2012
Physical Chemistry of Aqueous Processing on Material Surface
Yasuhiro AWAKURA

M. Pourbaix in Belgium proposed the Eh—pH diagram to examine the thermodynamic aspects of corrosion in 1940s. Thereafter, this potential—phase diagram was applied to the fields of, hydrometallurgy and fused salt chemistry as well as analytical chemistry, and it has been extended to the systems containing complex formation or sulfide formation reactions. It is because the diagram is quite useful to understand the thermodynamic aspects of reactions involved in the various processes from a bird’s eye view. In this paper, I briefly reviewed the applications of the diagram by exemplifying the electroless plating of nickel, the formation of ZnO thin films and the electrodeposition of CdTe films to contribute to understanding aqueous processing of material surfaces.
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Volume 125 (2009) Issue 6_7 Pages 375-380 Published: May 01, 2012
Thermodynamic Analysis for Vapour Epitaxial Growth of III-V Solid Solution Semiconductors
Katsunori YAMAGUCHI

The group III-V compound semiconductors and their solid solutions are important materials used in high speed electronic and optical electronic devices. Crystal growth of these semiconductor materials involves processes between the solid and liquid phases or solid and gas phase at near equilibrium conditions. Therefore, knowledge of thermodynamic and thermochemical properties for the semiconductor systems is important for providing optimum conditions in the analysis of processes for the crystal growth. In this report, some thermodynamic and thermochemical data such as heat capacity, standard entropy, heat and free energy of formation of compounds and heat of mixing of solid solutions on calorimetry are summarized. Base on these data, the vapor epitaxial growth of the III-V solid solution crystal are analyzed thermodynamically. The calculated compositions of the alloys have been compared with experiment, showing remarkably good agreement.
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Volume 125 (2009) Issue 6_7 Pages 381-388 Published: May 01, 2012
Feature and Importance of Solution Processings for Ceramics
Masahiro YOSHIMURA

Based upon thermodynamic considerations for various materials processing, solution processings appear to be the most energetically (environmentally) benign techniques. Various solution procesings for ceramics are critically reviewed with emphasis on their merits and demerits. Existing confusions and contradictions are pointed out in the definitions and concepts of various methods: i.e. precipitation, colloid, sol-gel, polymer-gel, complexed-gel (polymerized complex), soft process (soft solution process) and/or more widely, solution deposition, chemical solution deposition, bio-mimetic, bio-inspired, ink-jet, spray, etc. In particular, for ceramic films and patterns, the conventional methods where firing is essential after coating of powders from their suspensions or their solution precursors might be rather close to solid (powder) processes. This is especially true when significant chemical reactions are not involved during the coating processes, thus most reactions such as pyrolysis, compound formation (synthesis), crystallization, consolidation, substrate adhesion, etc., occur in the solid states by heat. In those solid state processes using firing of powders after shape-forming, the cracking/peeling of the film and/or the bulk is serious problems because volume shrinkage during firing is inevitable for packed powders. Those shrinkages practically limit the application of those powder processes.
In order to overcome those limitations, alternative methods where chemical reactions at the interface between a solution and a substrate solid and/or a reactant are described here as typical Soft Processing Methods. They may lower the difficulties in powder processes by forming shaped materials in a single step at lower temperatures. In addition to the production of nano-crystals such as SrTiO₃, Zr_0.6Ce_0.4O₂, etc., direct fabrication of LiCoO₂ and PbS films in solutions at room temperature to 150°C without post firing are described. “Direct Patterning of Ceramics” using ink-jet reaction or ink-jet deposition method has also been proposed.
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Volume 125 (2009) Issue 6_7 Pages 389-394 Published: May 01, 2012
Proton Transport Properties in Single Crystal of α-Alumina
Yuji OKUYAMA, Noriaki KURITA, Norihiko FUKATSU

The proton transport properties of a single crystal of acceptor (Mg, Ca, Sr, Ba) doped α-alumina was surveyed by reviewing our recent works. Here, the dissolution mechanism of hydrogen, the site of proton in the crystal, the value of conductivity, the mobility, and the concentration of defect for α-alumina are discussed. It was clarified that proton is incorporated into acceptor-doped α-alumina and it become the dominant charge carrier under the reducing atmosphere containing hydrogen at 1073-1673 K. Although the proton conductivity was very low, the transport number of proton for α-alumina was larger than the other defect structure-type proton conducting oxide at high temperature region.
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Volume 125 (2009) Issue 6_7 Pages 395-398 Published: May 01, 2012
Diffusivity of Oxide Ion in LaGaO₃ Perovskite Oxide
Tatsumi ISHIHARA

Oxygen diffusivity in perovskite oxide was introduced based on oxygen tracer diffusion constant. The high oxide ion conductivity in LaGaO₃ based oxide was explained by high mobility of vacancy. Although electrical conductivity increased with increasing dopant amount, mobility of vacancy estimated by oxygen self diffusion decreases with increasing dopant amount, which could be explained by the formation of dopant and vacancy cluster. Difference in oxygen diffusion in fluoride and perovskite oxide was also introduced.
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Volume 125 (2009) Issue 6_7 Pages 399-405 Published: May 01, 2012
Preparation of Fine Metal Powders in Aqueous Process and Morphology Control
Ryoichi ICHINO, Masazumi OKIDO

Metal powders were prepared by precursor—thermal decomposition method and chemical reduction method in aqueous solutions. In precursor—thermal decomposition method, the morphology and size of nickel powder were controlled via the thermal decomposition of nickel oxalate powder, that was prepared by mixing a solution containing oxalic acid ion with some kinds of nickel sources such as nickel ion, ammoniacal nickel complex ion, and nickel hydroxide. Needle-like nickel oxalate powder with high aspect ratio, [Ni(NH₃)₂]C₂O₄ 2H₂O, was synthesized by using ammoniacal nickel complex ion, and rectangular parallelepiped shape of nickel oxalate powder, NiC₂O₄ 2H₂O, was by nickel hydroxide. As for the chemical reduction method in aqueous solution, ascorbic acid (vitamin C) at pH 3 reacts with copper ion as a reducing agent, and copper metal particle in size of 100 nm was obtained. Under the condition of pH > 3, reduction property is weakened, and precipitates consisted of copper powder with cuprous oxide. Ti³⁺ ion (Ti₂(SO₄)₃ solution) also has a reducing property for copper ion and acts as a new reducing agent in liquid phase reduction process.
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