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1

Fabrication of nanoparticles by electric discharge plasma in liquid

Yatsu S, Takahashi H., Sasaki H., Sakaguchi N, Ohkubo K, Muramoto T., Watanabe S.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 2

425--429

EN

The electric plasma discharge method involves the application of a voltage between a cathode and anode in a conductive electrolytic solution to create a discharge plasma at the cathode. When certain material is used as the cathode, small droplets are emitted with the plasma discharge, and the melted droplets are rapidly cooled in the solution to form nanoscale particles of the material. In this work, nanoparticles of Al, Au, Si, and various alloys of between 100 nm and less than 10 nm in size were produced and characterized. Characterization of Si nanoparticles is especially important because their use in lithium batteries greatly influences battery performance. It was found by high resolution electron microscopy and microstructural surface analysis that oxidation layers of a few nm in thickness were formed on the surface of the Si nanoparticles.

PL

W metodzie wyładowań elektrycznych w cieczy pod wpływem przyłożonej różnicy potencjałów pomiędzy anodą i katodą zanurzonymi w elektrolicie dochodzi do wyładowania plazmy na katodzie. Gdy zastosuje się materiał jako katodę, podczas wyładowania plazmy tworzą się małe krople ciekłego materiału, które gwałtownie krzepną w elektrolicie. W ten sposób wytwarzane są cząstki nanometrycznej wielkości. Przy użyciu tej metody możliwe jest wytwarzanie nanocząstek różnych materiałów. Wytworzone nanometryczne cząstki Al, Au, Si oraz stopów miały wymiary od 100 nm do poniżej 10 nm. W szczególności nanocząstki Si stosowane do wytwarzania baterii litowych znacząco wpływają na wydajność baterii, z tego tez powodu bardzo ważne jest scharakteryzowanie tych cząstek. Obserwacje przy użyciu wysokorozdzielczej transmisyjnej mikroskopii elektronowej i analiza mikrostruktury nanocząstek Si wskazują, że na powierzchni cząstek znajduje się warstwa tlenków o grubości kilku nm.

2

Naturally occurring radionuclides and rare earth elements in weathered Japanese soil samples

Sahoo S., Hosoda M., Prasad G., Takahashi H., Sorimachi A., Ishikawa T., Tokonami S., Uchida S.

Acta Geophysica

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2013

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Vol. 61, no. 4

876--885

EN

The activity concentrations of 226Ra and 228Ac in weathered Japanese soils from two selected prefectures have been measured using a γ-ray spectroscopy system with high purity germanium detector. The uranium, thorium, and rare earth elements (REEs) concentrations were determined from the same soil samples using inductively coupled plasma mass spectrometry (ICP-MS). For example, granitic rocks contain higher amounts of U, Th, and light REEs compared to other igneous rocks such as basalt and andesites. Therefore, it is necessary to understand the interaction between REEs and nature of soils since soils are complex heterogeneous mixture of organic and inorganic solids, water, and gases. In this paper, we will discuss about distribution pattern of 238U and 232Th along with REEs in soil samples of weathered acid rock (granite) collected from two prefectures of Japan: Hiroshima and Miyagi.

3

Characterization of microstructure of Cr/CrN/Cr/Cr(N,C) coating deposited with pulsed laser deposition (PLD) technique.

Morgiel J., Major L., Takahashi H., Shibayama T., Foord D., Lackner J.M.

Archives of Materials Science

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2005

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Vol. 26, nr 1-2

111-117

EN

The Cr/CrN/Cr/Cr(N,C) coating on stainless steel substrate was obtained using Pulse Laser Deposition (PLD). The transmission electron microscopy (TEM) observations showed that the coating consist of four main layers of 225/341/75/416 nm, of which the first one is divided into three sub-layers. The second and fourth layer were built of columnar grains, while all the others showed an amorphous like contrast. Local chemical analysis performed using X-ray energy dispersive spectroscopy system (EDS) confirmed a high content of nitrogen and carbon in CrN and Cr(N,C) respectively and pointed toward a raised level of oxygen in all layers. These measurements also indicated the existence of strong Cr gradient in the buffer layer. The atomic resolution observations (HREM) helped to assess the maximum size of columnar grains below 20 nm. The same type of observations performed on Cr buffer and the intermediate layer proved to contain Cr nano-crystallites. Additionally, the density of nano-crystallites was found to change in between buffer sub-layers.

4

The friction and wear characteristics and the deformation of bronze powder-filled PEEK/PTFE blends in oscillating motion

Takahashi H., Saito A.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, Spec. is

433-439

EN

A study was made on polymer based composite materials, which are usable without lubrication as sliding members of oscillating motion components which are difficult to lubricate with oil. In this study, polyetheretherketone (PEEK) was used as a matrix, was blend with polytetrafluoroethylene (PTFE) which is a friction-reducing material. Friction and wear characteristics of each specimen in oscillating motion and continuous rotation were studied. As a result, the wear of pure PEEK in oscillating motion was about 20 times that in continuous rotation, but the wear of PTFE blended PEEK in oscillating motion was improved about 3 times that in continuous rotation. And the wear of PTFE blended specimens reduced to about 1/50 that of pure PEEK in oscillating motion and about 1/2 in continuous rotation. When PTFE blended PEEK was filled with bronze particles, wear was even further reduced in oscillating motion and also in continuous rotation. Coefficient of friction of pure PEEK in oscillating motion was greater than that in continuous rotation. When PEEK was blended with PTFE, coefficients of friction were reduced to such an extent as to eliminate differences in friction characteristics according to the direction of motion. Further, pv limits of pure PEEK in oscillating motion were extremely small compared to those in continuous rotation. When PEEK was blended with PTFE, pv limits were improved in oscillating motion and also in continuous rotation.