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Currently, several metals are commercially recycled from by-products and wastes by metallurgical processing. However, the metallurgical process has each characteristic, which causes limitation for resource recovery. The combinations of elements in secondary resources, such as by-products and wastes, are often different from those in natural resources. There are even combinations that are not present in natural resources. Conventional metallurgical processes have been optimized for economical and efficient extraction of desired elements only from large amount of ores under constant grade. Therefore, in order to extract metals from secondary resources by the conventional metallurgical process, it is necessary to estimate the recoverability of the constituent elements by taking into account their chemical properties well in advance. In particular, analysis for combination of elements is significantly important. In this study, we developed the evaluation method of metal resources recoverability based on thermodynamic analysis, and made clear the element distribution among gas, slag and metal phases during metal recovery based on thermodynamic analysis. In an application of the method shows that Cu, and precious metals (Ag, Au, Pt, Pd) present in mobile phones can be recovered as metals in the pyrometallurgy process of Cu in a converter. Other elements distributed in the slag phase are difficult to recover. The result of our analysis reflects the trends observed in the distribution of metals in copper metallurgy, thereby indicating the validity of our proposed evaluation method.

Currently, several metals are commercially recycled from by-products and wastes by metallurgical processing. However, the metallurgical process has each characteristic, which causes limitation for resource recovery. The combinations of elements in secondary resources, such as by-products and wastes, are often different from those in natural resources. There are even combinations that are not present in natural resources. Conventional metallurgical processes have been optimized for economical and efficient extraction of desired elements only from large amount of ores under constant grade. Therefore, in order to extract metals from secondary resources by the conventional metallurgical process, it is necessary to estimate the recoverability of the constituent elements by taking into account their chemical properties well in advance. In particular, analysis for combination of elements is significantly important. In this study, we developed the evaluation method of metal resources recyclability based on thermodynamic analysis, and made clear the element distribution among gas, slag and metal phases during metal recovery based on thermodynamic analysis. In an application of the method shows that Cu, and precious metals (Ag, Au, Pt, Pd) present in mobile phones can be recovered as metals in the pyrometallurgy process of Cu in a converter, while Pb and Zn can be recovered as vapor. Other elements distributed in the slag phase are difficult to recover. The result of our analysis reflects the trends observed in the distribution of metals in copper metallurgy, thereby indicating the validity of our proposed evaluation method.

Relation between the activity coefficient expressed by Darken's quadratic formalism and the excess Gibbs energy change of mixing described by Redlich-Kister type polynomial was discussed in Si deoxidation of Ni alloy. The activity coefficients of Si and O in metal expressed by quadratic formalism have been converted into formula using interaction parameters Ω i-j under the condition where concentration of Si and O are dilute. Numerical analysis on Si deoxidation of molten Ni and Ni-Cu alloy has been carried out. It has been found to be outstanding in the agreement of equilibrium Si and O contents in molten Ni and Ni-Cu alloy analyzed in the present work with the experimental results. The deoxidation equilibrium of not only pure metal but also alloy can be analyzed numerically using the formula determined in the present work.

Activities of the constituents in an alloy proposed for the Pb-free solder, Sn-Mg-Zn, were studied experimentally using a mass spectrom- eter. The ion current ratios of Mg to Zn were measured in the temperature range 700-800 K. From the experimental results and the assessed thermodynamic properties of molten Sn-Mg, Sn-Zn, and Mg-Zn binary alloys, the excess Gibbs free energy of liquid Sn-Mg-Zn ternary alloy was determined. Also, phase diagram of Sn-Mg-Zn ternary system was determined. The increase of demand for smaller and lighter portable electronic devices has made interconnecting densities and packaging technologies more important. Soldering material widely used is Sn-Pb alloy, which have low melting point and excellent electrical, strength properties and wettability. However, Pb is one of the toxic elements, which is undesir- able due to environmental and safety reasons, thus Pb-free alternative alloy is preferred for a new soldering material. Sn- Zn based alloys were viewed as very promising cadidates 1) among many potential substitutes, and Sn-Zn alloy has been already used as a soldering alloy in limited proposes. Addi- tion of Mg to Sn-Zn alloy decreases the melting point of the alloy, hence Sn-Mg-Zn alloy is expected to be suitable for replacing Sn-Pb solder alloy. In order to design new Pb-free soldering materials, precise understanding of thermodynamic properties and phase diagrams for alloy systems are crucial. The thermodynamic properties of Sn-Mg, 2-7) Sn-Zn, 8-11) and Mg-Zn 12-18) binary systems have been researched by many researchers. Also, the phase diagrams of these binary systems 19-21) were assessed using CALPHAD approach. 22) However, the thermodynamic properties of liquid phases de- termined experimentally do not accord with that obtained by phase diagram assessment, in general. This discrepancy arises because the thermodynamic properties of liquid phases were not considered properly during the phase diagram as- sessment. It is important to assess the phase diagram by con- sidering the activity of constituents in liquid phase. Also, accurate information for thermodynamic properties of liquid phases is indispensable for compatible phase diagram assess- ment. Hence, in the present work, the activities of the con- stituents in Sn-Mg-Zn alloy were measured. In the present work, the ion current ratios of Mg to Zn were measured for Sn-Mg-Zn alloy by mass spectrometry. The mass spectrometry method was selected because vapor pres- sure of Mg and Zn were relatively high, and accurate mea- surement could be expected. Moreover, the activities of all

Metallic impurities such as Al, Ca, Mg, Ti, and Fe in Si deteriorate solar cell efficiency to a large extent. To discuss the possibility and efficiency of impurity elimination process, the evaluation of their thermodynamic properties in molten Si are crucial. In the present work, the self-interaction parameters of Al, Ca, and Mg and interaction parameters between Ca-M (M: Al, Ti, Fe) in molten Si at 1723 K were investigated by applying a chemical equilibration technique for Si based alloys with Pb. The activity coefficients of Al and Ca in molten Si at 1723-1823 K were also determined by the Knudsen effusion method.