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New types of monoazacryptands were prepared and their complexation properties towards alkali metal cations were examined using the solvent extraction method, UV spectroscopy, X-ray crystal analysis, and liquid membrane transport. A lipophilic macrobicyclic polyether consisting of two 18-crown-6 rings and one 20-crown-6 ring was found to be a highly selective potassium ion carrier through a bulk liquid membrane by pH control.

In this paper, we deal with the phenomenon of melting at the point of contact between dissimilar metals by Joule heating. A heat conduction model for this dissimilar metal wire system is considered and the current required to sever the wire system by Joule heating is determined. The position at which the wire system severs depends on the ratio of the lengths of the two wires. Whereas this dependency is discontinuous, the current required to sever the wire is found to be continuous with respect to the ratio of the wire lengths, and the behaviors of the position and the current for severing the wire system are found to be classified into three regions. Based on these findings, a parameter that governs the melting phenomenon at the micrometer level for different ratios of wire lengths is proposed. Attempts were made to weld 25 μm thick Cu and Al wires of various lengths together by Joule heating. Moreover, the conditions for stably welding dissimilar metal wires together can be found quantitatively using the parameter proposed in this paper. It is noted that the welding condition described by the proposed parameter is independent with respect to the ratio of the lengths of the two wires in the respective regions.

In this paper we report on the Joule heat welding of dissimilar metal microwires. The current required for successful welding was investigated. Various combinations of 25 µm diameter Cu, Au and Al microwires were welded together using this technique. The welded dissimilar metal wire systems were then cut by supplying a higher current, and it was found that the position at which the wires cut was not at the midpoint, i.e., the position of the weld, of the wire system. This is because the temperature distributions formed in the dissimilar metal systems were asymmetrical. The positions at which the wires cut were in good agreement with those predicted by a heat conduction model. The lower limit for successful welding of the dissimilar metal microwire system was found to be determined by the lower of the two currents required to cut microwires of the individual materials.

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