Papers by Author: Taro Sumitomo

Abstract: Thin film solar cells are expected to play a key role in the next generation of photovoltaic devices, due to low costs and manufacturing advantages. Their functionality would be increased further if thin film solar panels were able to be machined efficiently without affecting the integrity of the nanoscale component layers. In this work, we investigated the effects of grinding and polishing processes on the integrity of solar panels. With the limited selection of grinding wheels and abrasive sizes, surface roughness and chipping were in the order of micrometers, while the use of diamond film polishing resulted in roughness in the order of nanometers with minimal damage to the layers.

Abstract: A nano-laminar glass/metal composite was fabricated. Glass flake powder coated with silver was used as the raw material, and was sintered by hotpressing. Samples fabricated in the optimum condition had a dense, laminar microstructure originating from the aligned flake powder. The result of a three-point bending test for the samples suggested that the alignment of the powder was essential for fracture behavior: When the powder was aligned in advance during the green sample fabrication, the sample fractured stably after the maximum load, while the samples fabricated by simple hotpressing of the powder without pre-alignment fractured unstably. Work of fracture of the sample in which the powder was well aligned was measured with chevron notched specimens; a significantly high value of about 300J/mm2 was obtained.

Abstract: Nacre is a natural composite material making up the inner structure of mollusk shells. It has been of great interest in materials research due to its mechanical properties far exceeding that of its individual components: well ordered plates of aragonite (a CaCO3 polymorph) within an organic polymer matrix. Generally the aragonite plates had been treated as single crystals and mechanical behavior explained as the result of micro-scale mechanisms between plates and matrix. However, recent work has shown that the plates themselves are made up of smaller nano-scale structures, which are also thought to contribute to the bulk properties. In this work, transmission electron microscopy (TEM) was used to observe the nano-scale structure of nacre from abalone. “Nanograins” of aragonite surrounded by organic material was observed, showing composite structure within aragonite plates.