Kuniyoshi Ishii

Unlubricated friction and wear behaviour of zirconia ceramics

Abstract In this work, friction and wear properties of 12Cc-TZP/10 mol.% Al2O3 and 12Cc-TZP ceramics against bearing steel were investigated by block-on-ring tribometer at room temperature. Based on the examination of wear track by X-ray diffraction, scanning electron microscopy with an energy-dispersive X-ray (EDAX) attachment, the texture formation on the wear surface of Ce-TZP is reported and the mechanisms involved are discussed.

Reduction of haematite to magnetite induced by hydrogen ion implantation

Microstructural changes induced by hydrogen ion implantation in haematite () have been investigated by transmission electron microscopy. It has been found that the hydrogen ion implantation causes the haematite magnetite () reduction at room temperature. From electron diffraction patterns after the hydrogen implantation, the following orientation relationship was found to exist between haematite and magnetite: . Since these results agree with those in previous studies, microstructural changes during the reduction were obtained by using the implantation technique. The reduction mechanism of magnetite from haematite is discussed in terms of the experimental results on crystallographic relationships.

Factors on the Measurement of Effective Thermal Diffusivity of Molten Slag Using Double Hot Thermocouple Technique

The molten slags that are used not only in the continuous caster but also in every metal industry play an important role and affect the quality of products. The authors initially developed the double hot thermocouple technique (DHTT) for in situ observation of mold slag crystallization. In this study, the DHTT was further developed to allow the measurement of the overall thermal diffusivity of molten slag applying the principle of the laser flash method. The affecting factors (finite pulse time, shape of pulse and heat loss from sample surface) on the measurement of thermal diffusivity using the DHTT were discussed theoretically using both the analytical and the numerical methods. New relationship between the thermal diffusivity a and the time at half-maximum temperature to 5 was obtained as follows: α(×10 4 m 2 /s) = 0.000707(t 0.5 /t p ) -1.8946 The thermal diffusivity obtained from the experimental half-maximum time t 0.5 /t p (t p is the time of peak on the heat pulse) was in good agreement with the one from literature.

In situ observation of transformation in α-Fe2O3 under hydrogen implantation

An in situ observation of the α-Fe2O3-to-Fe3O4 transformation has been performed using a dual-ion-beam accelerator interfaced with a transmission electron microscope (TEM). During the hydrogen-ion implantation of α-Fe2O3, transformation into the new phase (γ-Fe2O3 or Fe3O4) was observed. It was also found that the orientation relationship between α-Fe2O3 and the new phase (γ-Fe2O3 or Fe3O4) satisfies the Shoji–Nishiyama relationship, in agreement with previous experiments. It was also found that the nearest interatomic distance does not vary by the implantation until the re-stacked phase appears, although when the re-stacked phase is formed, the lattice expansion is observed in the transformed (re-stacked) phase. Judging from these results, we have concluded that the α-Fe2O3 to Fe3O4 transformation is induced during the hydrogen ion implantation of α-Fe2O3.

Liquid-state semiconductor p-n junction at 903K

A liquid-state semiconductor p-n junction has been fabricated by applying the liquid phase separation of the monotectic Sb-Sb2S3 system at 903K. Electrical conduction types of liquid semiconductor of Sb–S alloy and S2S3-x consisting of the immiscible system are found to be p and n types, respectively, from measured absolute Seebeck coefficients. The p-n junction was formed by the liquid Sb–-S alloy and Sb2S3−x; this is confirmed from the asymmetric current-voltage characteristics or its behavior is rectified. The formation of the liquid-state p-n junction in liquid semiconductors has great prospects in the next-generation direct thermal-to-electrical energy conversion materials.

Rupture Phenomena of Molten Na2O·2SiO2 Thin Films

A thin film drawn-out technique was developed to investigate the rupture mechanism of molten sodium silicate thin films. The rupture length of molten sodium silicate films was measured as a function of temperature and the drawn-out rate. It was found that the rupture thickness, T, was dependent on the drawn-out rate, v, at high drawn out rate, being proportional to the 2/3rd of v, i.e., T oc (v)2/3At low drawn-out rate the rupture thickness was found to be independent from v below a critical value vc. It was concluded that the rupture at high drawn-out rate was controlled by the external drawn-out rate of the molten slag and the constant rupture thickness at the low drawn-out rate might be determined by the Plateau border suction flow.