Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: Y. Fukuda x
Clear All Modify Search

Abstract  

Effects of metal surfaces, such as aluminium, silver and gold, on the melting behavior and thermal polymerization of long-chain diynoic acids having a diacetylene group at different positions were investigated by thermal analyses using DSC, TG and other methods. The surface effects of metals were significant in the order of Ag, Al and Au. These effects are attributable to the anchoring of carboxyl group on the surface by chemisorption, which leads to unfavorable condition for polymerization of heptadeca-2,4-diynoic acid. In the case of tricosa-10,12-diynoic acid, containing a flexible methylene chain, inserted between COOH and C≡C−C≡C groups, the anchoring of COOH on the metal surface causes rather favorable effect on the polymerization.

Restricted access

Abstract  

Nondestructive activation analysis by proton beam bombardment has been applied to cobalt specimens. Thick target yields were measured on 18 elements for the purpose of quantitative analysis. In order to detect precisely the radionuclides with different half-lives, gamma-ray spectrometry was repeated three times after different cooling times of 1, 15 and 250 hrs from the finish of bombardment for 1 hrby 10.4 MeV proton beam. It was found that Ti, Cr, Fe, Ni, Cu, Zn, Ga, Ge, As, Se, Zr, Nb, Mo, Cd, Sn, Sb, and Te of the order of ppm or less could be detected accurately. Using the proton activation analysis developed, the purification effects of anion exchange, electrolytic extraction, and floating zone-refining have been examined. It was confirmed that the concentrations of the impurity elements contained in the starting material decreased stepwise upon the application of each purification method.

Restricted access

Summary  

Atmospheric concentrations, dry and total depositions of7Be and210Pb were analyzed at Kumamoto, Japan from December 2001 to November 2003. Meteorologically derived change of air masses in Kumamoto resulted in lower atmospheric concentrations in summer than other seasons. The deposition of7Be and210Pb was large in winter and spring, however, the values of precipitation-normalized deposition indicated a clearer peak in winter than in spring, though the stratosphere-troposphere exchange supplies7Be at mid latitude in spring. The deposition velocity suggested that the wet deposition process functioned almost equally for both nuclides but the dry deposition process was much effective for210Pb.

Restricted access

Abstract  

A highly sensitive determination of fluorine in standard rocks by photon activation using the19F(,n)18F reaction combined with pyrohydrolysis for the separation of18F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and18F is also produced from Na via23Na(,n)18F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF3 precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.

Restricted access

Abstract

Fluorous multi-phase bromination reaction of alkenes could be successfully transformed to a continuous microflow system in which a fluorous polyether, Galden® HT135, is employed as a recyclable molecular bromine support. This microflow bromination of alkenes could be carried out without any temperature control or an inert gas atmosphere. The circulatory continuous microflow reaction system for bromination of cyclohexene was created which gave 8.3 g (85%) of dibromocyclohexane after continuous operation for 6 h.

Restricted access

Abstract  

Instrumental neutron activation analysis was applied to the determination of trace impurity elements in a silicon single crystal. Impurity concentrations in polysilicon melt were compared with those in a single crystal. Impurity concentrations in artificial quartz were also compared with those in natural quartz. Segregation coefficients in Au, Ir and Sb were determined at different concentrations. The segregation coefficient of an element in a silicon single crystal is constant over a critical concentration, it becomes larger gradually under the critical one, and at last it becomes larger than 1.

Restricted access

Abstract  

Neutron activation analysis was applied to the determination of trace impurity elements in a silicon ingot. Detection limits of 36 elements were calculated semi — empirically and compared with minimum concentrations detected in a silicon single crystal. The sources of the impurities were estimated from element concentrations detected in polycrystalline silicon and a quartz crucible. Segregation coefficients were determined from the concentration curves in a single crystal and discussed by comparing with reported values.

Restricted access