Biomedical subjects
Publications and source records attributed to Keiji Kurashima.
Nanofibrous platinum sheets with a thickness of one to a few tens of nanometres were prepared over the submicron pores of polymer substrates by using long and rigid cadmium hydroxide nanostrands as templates, and these free-standing sheets gave metallic conductivity that varied greatly with the thickness.
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The basic structure of alpha-LiFeO2, lithium iron oxide, is a cubic NaCl-type structure with a lattice constant of 0.42 nm; some short-range ordering characterized by octahedral clusters exists. The local structure of the short-range ordering was investigated by transmission electron microscopy and electron diffraction. A new short-range ordering structure was found in local areas. The local structure has a cubic lattice with a doubled lattice constant. The occupation factors of cations on Wyckoff sites 4(a) and 4(b) are different from those on 24(d) sites, but the stoichiometric composition in cubic clusters is the same as the macroscopic composition. The number of pairs in which iron cations exist in nearest-neighbor sites and next nearest-neighbor sites is reduced in the structure. This means that a magnetic interaction between the iron cations is reduced by cation ordering even without spin ordering at room temperature.
Cadmium hydroxide nanostrands with a diameter of 1.9 nm were spontaneously formed by raising the pH of a dilute Cd(NO3)2 solution. The length reaches a few micrometers and the aspect ratio exceeds 1000. The crystallographic structure was successfully elucidated by high-resolution electron microscopy. The surface of the nanostrands was remarkably positively charged and adsorbed an astonishing number of negatively charged dye molecules.
An energy-filtering transmission electron microscope with 300 kV acceleration voltage was developed and the spatial resolution of elemental distribution images was improved. Observing oxygen monolayers in Al(11)O(3)N(9), it was shown that the actual resolution attained is up to 0.5 nm. Surface plasmon loss images of silver particles were taken with a resolution of better than 0.4 nm. Furthermore, the sensitivity is sufficiently high to distinguish indium content differences of 2.5 atomic percent in In(x)Al(1-x)As. This performance is good enough to analyze elemental distribution with atomic-level resolution. Furthermore, since analysis with the energy-filtering microscope is easy and practical, nanoanalysis may come into wide use not only in academic fields but also in industry.
B/N-doped multiwalled C nanotubes were electrically probed by means of a tungsten needle attached to a piezo-driven stage of a high-resolution transmission electron microscope holder. Two-terminal transport measurements were performed in a 'W needle-nanotube-ground' circuit. The I-V curves were recorded in situ while viewing the nanotubes in the imaging mode of the microscope. This allows us to trace nanotube array morphological changes under applied voltage (up to 50 V). Specific manipulation with nanotube assemblies was found to be possible under applied electrical field: attachment of a tiny nanotube bundle to the W needle and extraction of a given nanotube fragment from an entangled complex bunch were achieved. The electrically-probed B/N-doped C nanotubes exhibited alternating B-rich and C-rich B-C-N domains within tubular layers, as revealed by elemental mapping during energy-filtered TEM (Omega filter). At room temperature the nanostructures displayed resistivity (rho) of approximately 1.8 x 10(-5) omegam and linear I-V curves. The key role of a given contact between the probing needle and a nanotube during electrical measurements was particularly verified.
A novel precursor, a mixture of B2O2 and Mg which is generated in situ by reacting B and MgO at 1300 degrees C, can be used to effectively synthesize bulk amounts of pure BN nanotubes with Mg evaporated from the final product; transmission electron microscope observation for the synthesized BN nanotubes indicates that defects present strongly depend on the tube diameter.