森田 昇

© 2018 Elsevier B.V. The additive voltage application provides silver nanowires in silver-doped glass prepared by electric field-assisted solid-state ion exchange. We experimentally investigate the growth behavior of silver nanowires in a glass substrate. It was found that silver nucleation was initiated at the silver-doped surface contacted with the cathode, and the precipitates dendritically developed toward the doped/un-doped interface as the time of voltage application was increased. After the precipitates reached the interface, the growth direction changed and extended along the interface. Transmission electron microscopy (TEM) observation suggested that the precipitation did not arise from the aggregation or growth of nanoparticles formed in the silver doping process. The experimental results, where the precipitation occurred just below the contacted cathode and was independent of cathode material, indicated that the precipitation resulted from the electrochemical interaction between doped silver ions and supplied electrons. From these findings, we are able to control the silver nucleation area by the arrangement of the cathode configuration.

? 2018 Japan Society for Precision Engineering. All rights reserved. A desktop friction stir spot welding (FSSW) system was designed and developed for the micro joining application. This system consisted of a high-speed air spindle, a PC-controlled translation stage, and a force sensor-integrated sample holder. The probe-less tools with taper-shaped head were prepared for the joining experiment. The developed system enabled the lap joints between copper (thickness: 0.1 mm) and aluminum (0.2 mm) sheets. In optimum conditions, the well-stirred zone, which exhibited laminated structure of thin copper and aluminum layers was observed at the joint interface. In this area, the formation of intermetallic compound was not observed. In addition, the fluctuation of tool load in the penetrating operation was measured. The tool load exponentially increased as the tool penetration, and rapidly turned downward even though the tool was continuously penetrated. The turning point in tool load curve implied the material softening and plastic flow initiation. Therefore, the force curve measured during tool penetration will be used as an estimation criterion for the joint quality formed by FSSW.

© 2018 Elsevier Inc. Solid-state ion exchange with an applied voltage enables metal doping of alkali-silicate glass surfaces. When the silver is used as the doping agent, application of a reverse voltage produces a silver layer buried in the glass substrate. The silver layer consists of a network of silver nanowires that have high electrical conductivity. In this work, we experimented with forming fine electrical paths in a glass substrate using silver nano-ink, an organic solvent containing dispersed silver nanoparticles printed on the glass surface, as the silver ion source. As a result, silver precipitation line of fine width/pitch (89/16.8 μm on average) were formed by sequentially applying forward and reverse voltages. We carried out a two-dimensional numerical analysis of the ionic diffusion behavior under an electric field to calculate the minimum line interval that would prevent two adjacent lines from overlapping. In this method, the buried silver layer is, in principle, connected to the glass surface via some precipitations, and we found an arrangement for the cathodes that confines the connection paths to the designed areas.