Yoshio Adachi

Effect of Carbon Coating on Electrochemical Performance of Treated Natural Graphite as Lithium‐Ion Battery Anode Material

Carbon-coated natural graphite has been prepared by thermal vapor decomposition treatment of natural graphite at 1,000 C. Natural graphite coated with carbon showed much better electrochemical performance as an anode material in both propylene carbonate-based and ethylene carbonate-based electrolytes than bare natural graphite. The effect of carbon coating on the electrochemical performance was investigated by solid-state {sup 7}Li-NMR in conjunction with standard electrochemical techniques.

Oxidative degradation of carbon blacks with nitric acid II. Formation of water-soluble polynuclear aromatic compounds

Abstract Furnace black and acetylene black were oxidized with concentrated nitric acid at 100xa0°C for prolonged periods. The oxidized carbon black was dissolved/dispersed into alkaline solution and was size-fractionated into six fractions by ultrafiltration. The yields of the fractions revealed that oxidized furnace black contains oxygenated polynuclear aromatic compounds with a variety of molecular sizes, but oxidized acetylene black consists of only a great quantity of the largest size fraction, probably carbon black particles, and a scarce amount of the smallest size fraction. With oxidized furnace black, elemental compositions of all fractions except the largest molecular-size fraction were independent of the period of oxidation, suggesting that each fraction possesses a similar molecular structure. Noncarbon constituents such as oxygen and hydrogen increased with decreasing molecular size. The mean molecular weights of fractions were estimated to be in a range from ca. 400 to 1200 and more on the basis of elemental and functional group analyses. 13C-NMR and IR analysis showed that the molecules of fractions comprise phenolic, carboxylic, nitro, perhaps quinonic carbonyl groups, and aromatic carbons, but no aliphatic carbons. Ultraviolet and visible spectra of fractions denoted that absorption at higher wavelengths increased with increasing the molecular weights, indicating extension in the conjugated aromatic ring system. On the basis of the experimental results molecular structure models for the fractions were proposed.

Water-Resistant Surface-Coating on Europium-Doped Strontium Aluminate Nanoparticles

The surface modification reaction was applied to the spherical nanoparticles of an elasticoluminescent material, europium-doped strontium aluminate, to improve the water-resistant property. The superior resistibility of the resulting material against water treatment was proved by scanning electron microscopy, photoluminescence, X-ray diffraction, and Fourier transform infrared measurements. Structure and property of the coating layer was also studied by solid state 31 P magic angle spinning nuclear magnetron resonance, atomic emission spectrometry, and zeta potential measurements.

Processing and Properties of SrAl2O4 : Eu Nanoparticles Prepared via Polymer-Coated Precursor

This paper reports a modified reverse micelles process for preparing nanoparticles of europium-doped strontium aluminate, a typical elastico-luminescent material. A polymeric matrix was coated on the surface of the precursor formed in the reverse micelles. The polymeric matrix is considered to prevent particle agglomeration by forming a carbon layer while the precursor is heat-treated. Consequently, the luminescent nanoparticles were obtained after removing the carbon layer and forming luminescent centers in a reducing atmosphere. The processing and properties of the luminescent nanoparticles are discussed.

Visualization of active crack on bridge in use by mechanoluminescent sensor

Innovative mechanoluminescent (ML) particles emit light repeatedly in response to small stresses applied, such as deformation, friction, or impact. When dispersedly coated on a structure, each particle acts as a sensitive mechanical sensor, while the 2-dimentional emission pattern of the whole assembly reflects well the dynamical stress distribution inside the structure and mechanical information around crack and defect. Thus, we have applied the remarkable strong points of ML sensing technique to a bridge in use as a real social structure for the first time. For the first ML monitoring test at bridge, we selected a relatively old bridge (established in 1954, 3-span continuous T-type RC bridge, length 24.4 m, width: 7.89 m). The ML sheet type sensors were put around the central area (700×400 mm) of the main girder, and ML images originated from dynamic load application via general traffic vehicles had recorded by using lab-made CCD camera under roughly dark condition. As the result, we successfully detected intense ML patterns not only along visible crack but also at round soundless part on the girder at a glance with responding ML intensity reflecting the crack mouth opening displacement (CMOD) of visible crack and invisible progressing microcrack.

Enhancement of Mechanoluminescence from ZnS:Mn,Te by Wet Process

We successfully synthesized the novel mechanoluminescent material ZnS:Mn,Te with a wurtzite structure by controlling the pH of the solution used in the wet process. This material showed a distinct red mechanoluminescence (ML) with an increased intensity, being one order of magnitude higher than that of the sample prepared using a solid-state reaction. This marked increase in ML intensity was realized by eliminating ZnO and MnO impurities.

Real-time detection of axial force for reliable tightening control

We developed a novel technique for bolt tightening control by utilizing SrAl2O4:Eu (SAOE) paint film to detect axial force generated during bolt tightening. Conventionally, torque method is prevalently used for bolt tightening control. The major problem of this method which indirectly controls the axial force in bolted joints is that only a small proportion of the torque actually contributes to the bolt extension. It is the axial force due to such an extension that fastens the bolted joints. Therefore, it is urgently necessary to directly measure the axial force in order to realize a smart tightening control. Considering the extension of bolt during tightening can induce elastico-luminescence of SAOE if it is painted on the bolt or washer, we have painted SAOE/polymer film on the washer and consequently measured elastico-luminescence of SAOE film while tightening the bolt under various conditions. In the present work, we also demonstrated the correlation between the elastico-luminescence intensity and tightening conditions including tightening speed and strain as well as axial force.

Elastico-Luminescent Nanoparticles Prepared via Polymer-Coated Precursor Formed in Reverse Micelles

Europium-doped strontium aluminate is a famous green phosphor that can give luminescence under a mechanical stress that is named elastico-luminescence. This paper reports a modified reverse micelles process for preparing the europium-doped strontium aluminate nanoparticles. A polymeric matrix was coated on the surface of the precursor formed in the reverse micelles. The polymeric matrix is considered to prevent the particle agglomeration by forming a carbon layer while the precursor was heat-treated. Consequently, the luminescent nanoparticles were achieved after removing the carbon layer and forming the luminescent center under a reducing atmosphere. The processing and properties of the luminescent nanoparticles were discussed in this paper.

Mechanoluminescence Studies upon Single Nanoparticles by AFM-photomeasurement System

We successfully measured the mechanoluminesence (ML) from a single ML nanoparticle at the first time. In order to measure the weak light emission from a single nanoparticle induced by applying a micro force, we developed an AFM-based new apparatus with a photomultiplier. Interestingly, the emission (ML) intensity from a nanoparticle was approximately proportional to the load, the phenomena is similar to the macroscopic ML emission properties.