Papers by Author: Tsuneo Suzuki

Abstract: Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was achieved in polyepoxide-based nanohybrid films. A homogeneous suspension of pre-polymer of polyepoxide and OxNDs was cast onto a polyamide-spacer and subjected to an electric field in order to induce relocation and stretched-assembles of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, and aligned vertical to the film surfaces. Nanohybrid films with assemblies of LAOxNDs led to a significant enhancement in thermal conductivity while maintained the electrical insulation property of the polyepoxide. Mechanisms for the formation and structural variation of LAOxNDs in the matrix are elaborated regarding the improvement in physical properties. The present ambient-oxidation process and field-induced application are simple, but effective in enhancing the thermal properties of the polymer-based hybrids, and hence, promising for applications in the semiconductor industry, such as thermal interface materials.

Abstract: Cr-Me-N-O (Me; Ni, Cu and Mg) thin films have been designed and successfully prepared by the pulsed laser deposition (PLD) method. It was found that Me, which form the monoxide MeO, are effective for hardening the Cr(N,O) thin films.

Abstract: Chromium oxynitride (Cr(N,O)) thin film have been successfully prepared by using pulsed laser deposition. The composition of the thin film was determined to be Cr0.50N0.23O0.28 by Ruthreford backscattering spectroscopy (RBS). The structural analysis was carried out by using X-ray diffraction (XRD), and out-of-plane and in-plane measurements were used to clarify the axial ratio (c/a) of the Cr(N,O) phase. The lattice constants of a and c axes in the Cr(N,O) phase were found to be 0.414 and 0.419 nm, respectively. From these results, the cubic to tetragonal phase change by substitution of the oxygen atoms for nitrogen atoms was confirmed for the crystal Cr(N,O) compounds.

Abstract: Nitriding of titanium was achieved in a vacuum of ~2×10-2 Pa by applying intense pulsed ion beam (IPIB) irradiation. Various phases including ‘pure’ nitrides (e.g. Ti2N, TiN) as well as carbonitrides (e.g. TiC0.3N0.7) were found on the IPIB-irradiated surfaces that depended on the ion beam intensity, shot number, and sample position with respect to the ion beam axis. It was found that the nitrides were preferably produced at moderate beam intensity by which the nitriding depth increased greatly with multi-shot irradiation. No or less nitrides were produced under irradiation of very high intensity or less number of shots. It is demonstrated that the IPIB nitriding process is very efficient even in vacuum where the residual N2 can readily react with melted Ti surfaces under IPIB irradiation. The origin of incorporated C in the nitrides is mainly attributed to the anode material of ion diode used in the IPIB apparatus.

Abstract: A pulsed wire discharge (PWD) apparatus for mass production of nanosized powders was developed. The apparatus had a wire feeder, and could prepare 1.5 g of Cu powder in 200 sec. The mean surface diameter of Cu powder was 86 nm. The particle size distribution of the powder prepared by 100 discharges was increased than that by one discharge. In addition, the median diameter of the powder after the 100 discharges was larger than that by one discharge. A part of the nanosized powders in production chamber of the apparatus would be grown by the deposition of plasma or vapor formed by the next discharge.

Abstract: Chromium magnesium oxynitride ((Cr,Mg)(N,O)) thin films have been prepared by pulsed laser deposition (PLD) method with changing the surface area ratio of Mg target (SR) from 0 to 100 %. As a result of the analysis by energy dispersive X-ray spectroscopy (EDX), it was found that magnesium content in the total metallic elements (Cr1-x, Mgx) are controlled by changing SR from 0 to 100 % to be the x ranging from 0 to 1.0. Since the crystal structure of main phase in all thin films was found to be NaCl type, the XRD results showed that the thin films were mainly consisted of (Cr,Mg)(N,O). The hardness of (Cr,Mg)(N,O) thin films were increased almost linearly up to SR = 50 %, above which it decreases rapidly. The maximum Vickers hardness (HV) of 3600 was obtained for the thin film which was prepared by SR = 50 %, and the minimum HV of 1650 was obtained for the thin film which was prepared by SR = 100 %.

Abstract: We have attempted phase identification of carbon nanosized powders prepared by pulsed wire discharge (PWD) to clarify the cooling process of PWD plasma. To prepare the carbon nanosized powders, carbon fibers were discharged in nitrogen gas at 26 – 101 kPa by PWD. Volume fractions of phases in the carbon nanosized powders were analyzed by thermogravimetric analysis and powder X-ray diffraction. The volume fraction of amorphous carbon, which must be formed by quenching of carbon plasma, was increased with increasing nitrogen gas pressure. This result suggested that the cooling rate of PWD plasma increased with increasing ambient gas pressure.