Publications by authors named "Heishichiro Takahashi"

7 Publications

  • Page 1 of 1

Solution-Plasma-Mediated Synthesis of Si Nanoparticles for Anode Material of Lithium-Ion Batteries.

Nanomaterials (Basel) 2018 Apr 27;8(5). Epub 2018 Apr 27.

Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kitaku, Sapporo 060-8628, Japan.

Silicon anodes have attracted considerable attention for their use in lithium-ion batteries because of their extremely high theoretical capacity; however, they are prone to extensive volume expansion during lithiation, which causes disintegration and poor cycling stability. In this article, we use two approaches to address this issue, by reducing the size of the Si particles to nanoscale and incorporating them into a carbon composite to help modulate the volume expansion problems. We improve our previous work on the solution-plasma-mediated synthesis of Si nanoparticles (NPs) by adjusting the electrolyte medium to mild buffer solutions rather than strong acids, successfully generating Si-NPs with <10 nm diameters. We then combined these Si-NPs with carbon using MgO-template-assisted sol-gel combustion synthesis, which afforded porous carbon composite materials. Among the preparations, the composite material obtained from the LiCl 0.2 M + H₃BO₃ 0.15 M solution-based Si-NPs exhibited a high reversible capacity of 537 mAh/g after 30 discharge/charge cycles at a current rate of 0.5 A/g. We attribute this increased reversible capacity to the decreased particle size of the Si-NPs. These results clearly show the applicability of this facile and environmentally friendly solution-plasma technique for producing Si-NPs as an anode material for lithium-ion batteries.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano8050286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5977300PMC
April 2018

Novel metal allergy patch test using metal nanoballs.

J Nanobiotechnology 2014 Dec 3;12:51. Epub 2014 Dec 3.

Department of Dentistry, Oral and Maxillofacial Surgery, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan.

Background: Patch tests are often used in the clinical diagnosis of metal allergies. In currently available patch tests, high concentrations of metal salt solutions are used. However, diagnosis accuracy can be influenced not only by acute skin reactions to high concentrations of metal salt, but also by skin reactions to other components present in the patch or to pH changes. In this study, we developed Ni nanoparticles (termed "nanoballs") for use in patch-test solutions.

Findings: Highly soluble, spherical Ni nanoballs were prepared using plasma electrolysis. The Ni released from the nanoballs permeated through a dialysis membrane, and the nanoball-containing solution's pH was maintained constant. Ni ions were released slowly at low concentrations in a time-dependent manner, which contrasted the rapid release observed in the case of a commercial patch test. Consequently, in the new test system, reactions caused by high concentrations of metal salts were avoided.

Conclusions: By exploiting the high specific surface area of Ni nanoballs, we obtained an effective dissolution of Ni ions that triggered Ni allergy in the absence of direct contact between the nanoballs and mouse skin. This novel patch system can be applied to other metals and alloys for diagnosing various types of metal-induced contact dermatitis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12951-014-0051-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260209PMC
December 2014

Control of the collagen fibril diameter in the equine superficial digital flexor tendon in horses by decorin.

J Vet Med Sci 2005 Sep;67(9):855-60

Department of Veterinary Anatomy, School of Veterinary Medicine, Rakuno Gakuen University, Hokkaido, Japan.

The distribution pattern of collagen fibril diameter in the equine superficial digital flexor tendon (SDFT) is known to differ in central and peripheral areas of some regions. This study reports the essence of collagen fibril differences among different regions of the equine SDFT by transmission electron microscopic (TEM) and high-voltage electron microscopic observations and biochemical analysis. The distribution of large collagen fibrils increased but the density of collagen fibrils decreased from the proximal metacarpal region to the distal metacarpal region. Large collagen fibrils with an irregular cross-sectional profile were found more frequently in the middle metacarpal region than in other regions. Three-dimensional reconstruction of images of irregularly shaped collagen fibrils revealed that these fibrils are formed through fusion of small collagen fibrils with large ones. The amount of decorin, which reportedly inhibits the lateral fusion of collagen fibrils, decreased in the direction of the distal metacarpal region. On the other hand, the size of decorin gradually increased in the direction of the distal metacarpal region. These results suggest that regional differences in collagen fibril distribution and density of collagen fibrils in the SDFT are due, at least in part, to fusion of collagen fibrils and the concomitant regional differences in the amount and size of decorin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1292/jvms.67.855DOI Listing
September 2005

Nano-scale phase transformation in Ti-implanted austenitic 301 stainless steel.

J Electron Microsc (Tokyo) 2003 ;52(5):449-53

Center for Advanced Research of Energy Technology, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, Japan.

Phase-transformation behaviours were investigated for austenitic 301 stainless steel during implantation at room temperature with 300 keV Ti ions to fluences of 8 x 10(19) to approximately 3 x 10(21) ions m(-2) by means of transmission electron microscopy. The cross-sectional specimen was prepared using a focused ion beam. Plan observation of the implanted specimen showed that phase transformation from gamma-phase to alpha-phase was induced by implantation to a fluence of 3 x 10(20) Ti ions m(-2). The nucleation of the irradiation (implantation)-induced phase increased with the increase of the dose. The orientation relationship between the gamma matrix and the induced alpha martensitic phase was identified as (011)alpha//(111)gamma and [11-1]alpha//[10-1], close to the Kurdjumov-Sachs relationship. Cross-sectional observation after implantation to a fluence of 5 x 10(20) ions m(-2) showed that phase transformation mostly nucleated near the surface and occurred in the higher the concentration gradient of the implanted ion, i.e. a higher stress concentration takes place and this stress introduced by the implanted ions acts as a driving force for the transformation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jmicro/52.5.449DOI Listing
January 2004

Creep deformation of grain boundary in a highly crystalline SiC fibre.

J Electron Microsc (Tokyo) 2003 ;52(1):75-8

Center for Advanced Research of Energy Technology, Hokkaido University, Sapporo 060-8628, Japan.

Silicon carbide (SiC) matrix composites reinforced by SiC fibres (SiC/SiC composites) are currently being considered as alternative materials in high Ni alloys for high-temperature applications, such as aerospace components, gas-turbine energy-conversion systems and nuclear fusion reactors, because of their high specific strength and fracture toughness at elevated temperatures compared with monolithic SiC ceramics. It is important to evaluate the creep properties of SiC fibres under tensile loading in order to determine their usefulness as structural components. However, it would be hard to evaluate creep properties by monoaxial tensile properties when we have little knowledge on the microstructure of crept specimens, especially at the grain boundary. Recently, a simple fibre bend stress relaxation (BSR) test was introduced by Morscher and DiCarlo to address this problem. Interpretation of the fracture mechanism at the grain boundary is also essential to allow improvement of the mechanical properties. In this paper, effects of stress applied by BSR test on microstructural evolution in advanced SiC fibres, such as Tyranno-SA including small amounts of Al, are described and discussed along with the results of microstructure analysis on an atomic scale by using advanced microscopy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jmicro/52.1.75DOI Listing
June 2003

Radiation-induced segregation and precipitation behaviours around cascade clusters under electron irradiation.

J Electron Microsc (Tokyo) 2003 ;52(1):63-8

Center for Advanced Research of Energy Technology, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo 060-8628, Japan.

We have investigated the formation of cascade clusters and structural changes in them by means of electron irradiation following ion irradiation in an austenitic stainless steel. Almost all of the cascade clusters, which were introduced by the ion irradiation, grew to form interstitial-type dislocation loops or vacancy-type stacking fault tetrahedra after electron irradiation at 623 K, whereas a few of the dot-type clusters remained in the matrix. It was possible to recognize the concentration of Ni and Si by radiation-induced segregation around the dot-type clusters. After electron irradiation at 773 K, we found that some cascade clusters became precipitates (delta-Ni2Si) due to radiation-induced precipitation. This suggests that the cascade clusters could directly become precipitation sites during irradiation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jmicro/52.1.63DOI Listing
June 2003

Preparation of novel silica-cadmium sulfide composite nanoparticles having adjustable void space by size-selective photoetching.

J Am Chem Soc 2003 Jan;125(2):316-7

Catalysis Research Center, Graduate School of Environmental Earth Science and Center for Advanced Research of Energy Technology, Hokkaido University, Sapporo 060-0811, Japan.

The size-selective photoetching technique was used to control the size of a CdS nanoparticle inside a silica shell. With monochromatic light irradiation, the diffuse reflectance spectra of silica-coated CdS nanoparticles were blue-shifted, and the size of the resulting CdS nanoparticles incorporated in the silica shells was adjustable by varying the wavelength of irradiated light. TEM observation revealed that the original CdS nanoparticle seemed to be in close contact with the amorphous silica shell to leave almost no clearance, while the monochromatic light irradiation caused the decrease in the size of CdS particles, resulting in the formation of a void space between the photoetched CdS core particle and the silica shell. The average void spaces available in the shells were calculated to be ca. 1.4 and 2.4 nm with the irradiation at 514 and 458 nm, respectively. These results indicated that the size-selective photoetching technique enables the regulation of void space formed in the core-shell structure by choosing the wavelength of irradiation light.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja0278133DOI Listing
January 2003