Papers by Author: Sakae Tanemura

Abstract: Grafting methacryloxypropyltrimethoxysilane (MPS) onto the surface of silica nanoparticles is the most common approach in surface chemical modification. Traditionally, ethanol or toluene was used as solvent in the grafting process. However, using ethanol as solvent brought about poor grafting result and toluene being regulated was also not an ideal grafting solvent. In order to overcome these disadvantages, we widen the grafting solvents and a novel solvent of xylene was utilized to prepare MPS grafting silica cryogels in this study. The hydrolysis of MPS was in the mixture of methanol and water using diluted hydrochloric acid solution as a catalyst. Both original and MPS-grafted samples were characterized by fourier transform infrared spectrometer (FTIR), thermogravimetric analysis (TG) and other methods. The results showed that xylene is an effective solvent in the process of grafting and the MPS was chemically bonded onto the surfaces of nano-silica particles.

Abstract: A compact angle-resolved secondary ion mass spectrometer (AR-SIMS) with a special geometrical configuration, composing of a differentially pumped micro-beam ion-gun, a tiltable sample stage and a time-of-flight (TOF) mass spectrometer was applied to measure angular distribution (AD) of secondary ions ejected from VN by oblique 3 keV Ar+ sputtering at room temperature. AD of V+ was almost identical with that of N+, strongly suggesting that Gibbsian segregation did not take place during sputtering. Since the angular dependence of VN+/V+ and V2 +/V+ intensity ratios was independent of that of N+ and V+ intensities, VN+ and V2 + dimer ions were generated via the “as such” direct emission process.

Abstract: Toward the tailored growth of carbon nanotubes (CNTs), CNT growth using hydrocarbon ion beams at the ion energy of 150 eV and the ion current densities of 10 ∼ 165 μA/cm2 was challenged at various growth temperatures. Fibrous protrusions with an amorphous nature grew at a low ion current density, whereas highly crystallized multi-wall CNTs were synthesized at high ion current densities. The higher the growth temperature and the ion current density, the smaller the CNT diameter. Similar to the conventional PECVD-grown CNTs, they grew via the so-called “tip-growth mode.”

Abstract: Photochromic material Ag-TiO2 thin films are fabricated on quartz substrate by dual -target helicon magnetron sputtering. The phototchromic behavior is investigated for the sample loaded with 90% Ag. Spheres, ellipsoids and polyhedra shape of Ag particles with wide range size (5∼100 nm) are dispersed in the TiO2 amorphous matrix observed by transmission electron microscopy. The spectral hole burned by the irradiation of laser at the wavelength 532 nm can be explained by a particle-plasmon-assisted electron transfer from Ag nanoparticles to TiO2 and subsequent trapping by adsorbed molecular oxygen. Moreover, the mechanism of the slow recovery after photochromism is suggested as a slow thermal release of electrons from oxygen trapping centers and subsequent capture into the Ag nanoparticles.

Abstract: Transparent indium-doped ZnO (IZO) films with low In content (<6at%) were fabricated through radio-frequency (rf) helicon magnetron sputtering. Formation of In-Zn-O solid solution was confirmed by X-ray diffraction (XRD) patterns. Incorporation of indium into ZnO films enhances the optical transmission in the visible wavelength. The optical band-gaps slightly increase from 3.25eV (ZnO) to 3.28eV (In0.04Zn0.96O) and to 3.30eV (In0.06Zn0.94O) due to Burstain-Moss effect. The Urbach tail parameter E0, which is believed to be a function of structural disorder, increases from 79meV (ZnO), to 146meV (In0.04Zn0.96O), and to 173meV (In0.06Zn0.94O), which is consistent with increase of Full-Width Half-Maximum (FWHM) in corresponding XRD patterns. Decreasing in crystal quality with increasing indium concentration is also confirmed by photoluminescence spectra.

Abstract: RF (Resorcinol-Formaldehyde) aerogels and carbon aerogels were prepared through the sol-gel method following the routes of polymerization, gelation, supercritical drying and pyrolysis processes. The influence of fabrication parameters on the textural structure of the samples, e.g., specific surface area, pore size, and pore size distribution, etc., were systematically investigated. With a decrease in the R/F molar ratio, or an increase in the catalyst content within a limited range, the porosity of the nanostructure materials increases. The optimal temperature of pyrolysis for RF aerogel was investigated by TGA (Thermogravimetric Analysis).

Abstract: The photocatalytic effects of 4 samples, which TiO2 layer uniformly coated on Al fiber, are evaluated by NOx removal. An anatase TiO2 coating with good crystal quality and high Ti content exhibits the best photocatalytic effect on NOx removal. It is coincidence with the results of XRD, XPS results for 4 samples. The photocatalytic ability is enhanced by the introduction of H2O2 due to the formation of large amount OH radicals.

Abstract: We have prepared titania aerogel (=AG) embedded by NiB nano-clusters by sol-gel method, immersion of the prepared wet gel into the NiB dispersed solution, and the subsequent super critical drying (=SCD). The AG was characterized by X-ray diffraction (XRD), a transmission electron microscopy (TEM), and a fourier transform infrared spectrophotometer (FT-IR). XRD and selected area electron diffraction (SAED) patterns assured the formation of TiO2 anatase phase. TEM observation reveled the composition of TiO2 crystallites with about 4 nm in size. Catalyst performance for the ground sample was confirmed by chemical reaction of oxidation of benzene at low temperature, and the difference in catalyst performance between TiO2 AGs with and without the embedded NiB nano-clusters has been examined.