Papers by Author: Noboru Yoshikawa

Abstract: Microwave heating was discovered more than 60 years ago. And nowadays, it became popular for the use as domestic ovens. Microwave has also been utilized for the industrial processes, such as drying and roasting. On the other hand, there have been many applications of microwave, being investigated for materials' processing and environmental technologies. They are attempted to take advantage of some specific characteristics in microwave heating, which differs from that of the conventional one. Rapid heating, internal heating, selective heating are the features to be taken into consideration. Moreover, so-called "non-thermal effect" is the additional feature in which researchers are particularly interested. In this article, it is intended to describe fundamental aspects in microwave heating and introduce some selected topics of research projects performed in our research group. They include researches on fabrication of some functional materials and on handling industrial wastes etc. In this article, it is also intended to interpret the phenomena observed in these applications from the fundamental view points of electromagnetic wave interaction with materials.

Abstract: In this study, porous SiO₂·RO/stainless steel composite body was prepared through the polyurethane sponge replica method. Porous samples obtained through sintering consist of well dispersed and distributed stainless steel particles within the glass matrix. Such microstructure is desired for the purpose as a soot particulate filters (DPF) utilizing microwave rapid and selective heating characteristic, especially during the cold start phase of an engine. Results of microwave heating ability and diesel soot regeneration tests shows that, the fabricated porous composite material is proven to be reliable for rapidly microwave assisted regeneration. Both the regeneration temperature and O₂ composition in the supplied gas played an important role in the regeneration process.

Abstract: . It is known that bulk metallic samples reflect microwaves (MWs) while metallic powdered samples can absorb such radiation and be heated efficiently. The present paper shows a direct evidence of penetration of MW radiation into and through a layer of metallic powder and contains theoretical explanation of such behavior.

Abstract: In this study, microwave (MW) heating of Fe powder in the separated electric (E-) and magnetic (H-) fields was performed first, and the heating behaviors on the field dependence were investigated. It was shown that they are heated better in H- field than in E- field. The MW heating mechanism of metals were briefly discussed. MW heating of soda-lime glass alone was not easy, however addition of iron powder enhanced the heating, depending on the volume fraction of the powder. Occurrence of deformation and melting of the glass spheres was observed. This technique is applicable to fabrication of glass-metal composites and vitrification of waste matters. MW heating of Ni-based metal glass was attempted with no external pressure and in an inert atmosphere, it was also shown that heating was better accomplished in H- field. Weakly sintered body was possibly obtained with retention of the amorphous phase.