摘要 :
We synthesize Y_3Al_5O_(12): Ce~(3+) (YAG:Ce~(3+)) nanoparticles in the presence of citric acid by glycothermal method. Fourier transform infrared absorption spectroscopy measurement indicates that the intensity of the peak corres...
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We synthesize Y_3Al_5O_(12): Ce~(3+) (YAG:Ce~(3+)) nanoparticles in the presence of citric acid by glycothermal method. Fourier transform infrared absorption spectroscopy measurement indicates that the intensity of the peak corresponding to carboxyl groups coordinating to the nanoparticles increases with increasing amount of citric acid. At the same time, the primary particle diameter decreases from 10.2 to 4.0 nm. In addition, the internal quantum efficiency of the photoluminescence (PL) due to the 4f-5d transition of Ce~(3+) increases from 22.0% to 40.1% with increasing amount of citric acid. Two kinds of PL decay lifetimes, 16-26 and 72-112 ns, are detected for YAG:Ce~(3+) nanoparticles, whereas the micron sized YAG:Ce~(3+) bulk shows the lifetime of 57 ns. We discuss these phenomena from the aspects of the coordination of citric acid and the incorporation of Ce~(3+) ions into the nanoparticles.
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Unlike the impedance plane analysis form of common eddy current testing (ECT), the remote field eddy current (RFEC) technique is a through-transmission effect that reduces problems such as lift-off normally associated with ECT. In...
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Unlike the impedance plane analysis form of common eddy current testing (ECT), the remote field eddy current (RFEC) technique is a through-transmission effect that reduces problems such as lift-off normally associated with ECT. In the inspection of steam generator (SG) tubes, the real issue is to detect the minute cracks growing up from the outside. However, using ECT, it is considered infeasible to accurately find them from the inside because of the limitations of penetration of eddy currents. This paper describes a finite-element approach to the solution of time-harmonic electromagnetic fields for the RFEC technique based on a magnetic vector potential and an electric scalar potential.
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Plasma-source ion implantation (PSII) is successfully employed without an external radio frequency plasma source to form a thin amorphous carbon layer on the surface of polyethylene terepthalate (PET) film by applying pulsed high ...
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Plasma-source ion implantation (PSII) is successfully employed without an external radio frequency plasma source to form a thin amorphous carbon layer on the surface of polyethylene terepthalate (PET) film by applying pulsed high negative voltage (～10μs pulse width, 300-900 pulses/s, -10 kV) to a sample immersed in C_2H_2 gas with and without Ar. This pulsed voltage condition is found to itself generate a plasma surrounding the substrate and PET film to form a thin carbon layer. The oxygen barrier characteristics of the PET were improved remarkably by this PSII processing, and laser Raman, X-ray photoelectron and Fourier-transform infrared spectroscopy spectra revealed that the thin amorphous carbon layer was found to consist primarily of graphite crystal with the characteristics of diamond-like carbon. The ratio of sp~2 (graphite) to sp~3 (diamond) populations was found to vary according to the gas pressure of C_2H_2 and the addition of Ar, which affects on the oxygen barrier characteristics.
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摘要 :
The characteristics of amorphous carbon films deposited on polyethylene terepthalate (PET) film by plasma-source ion implantation (PSII) using C_2H_2 and CH_4 gases are examined. PSII is performed using a pulsed, high negative bia...
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The characteristics of amorphous carbon films deposited on polyethylene terepthalate (PET) film by plasma-source ion implantation (PSII) using C_2H_2 and CH_4 gases are examined. PSII is performed using a pulsed, high negative bias (～9 kV, ～ 10μs pulse width, 300 pulses/s) to form the self-excited discharge for processing. The use of CH_4 at lower gas pressure modified the PET film by direct implantation of carbon atoms to form a mixing layer with high C-H bond density, in contrast to formation using C_2H_2 which forms a surface coating of amorphous carbon. At higher gas pressure, CH_4 was found also to produce a surface layer of amorphous carbon. The films produced using CH_4 were found to consist primarily of hydrogenated graphite crystal with C-H, C-H_2 and C-H_3 components. The oxygen transmission rates (OTR) of PET treated with CH_4 were reduced by a factor of 50-70 from that of untreated PET at a carbon film thickness of only ～50 nm, however the transmission rate reduction per unit thickness of film was lower than for films formed using C_2H_2. The surface modification with CH_4 is a viable alternative method for reducing the OTR. The relationships between the gas conditions and the properties of the carbon films are discussed.
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A comprehensive study of the adiabatic temperature change ΔT_(ad) in the vicinity of a first-order magneto-structural phase transition has been carried out on a Ni_(2.19)Mn_(0.81)Ga Heusler alloy. It was found that the directly m...
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A comprehensive study of the adiabatic temperature change ΔT_(ad) in the vicinity of a first-order magneto-structural phase transition has been carried out on a Ni_(2.19)Mn_(0.81)Ga Heusler alloy. It was found that the directly measured ΔT_(ad)～1 K is of order of magnitude smaller than that expected from reported in the literature isothermal magnetic entropy change and specific-heat data. A new feature of the adiabatic temperature change in materials with giant magnetocaloric effect, specifically an irreversible character of ΔT_(ad) when the sample is subjected to repeatable action of magnetic field at a constant temperature, has been observed. This effect has been attributed to the irreversible magnetic-field-induced structural transformation. It has been shown that the small value of ΔT_(ad) in Ni_(2.19)Mn_(0.81)Ga is not due to the kinetics of the transformation but originates from other factors which are intrinsic to first-order magnetic phase transitions. Relevance of these factors to other giant magnetocaloric materials has been outlined.
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摘要 :
The electroforming and the resistance-switching behaviors in magnetite, Fe_3O_4, by the application of an appropriate electric field are demonstrated on a lateral device with multiple electrodes. By means of this device, both the ...
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The electroforming and the resistance-switching behaviors in magnetite, Fe_3O_4, by the application of an appropriate electric field are demonstrated on a lateral device with multiple electrodes. By means of this device, both the location and the nature of the change in Fe_3O_4 are specified from the electrical measurements and Raman spectroscopy. The switching phenomenon is caused in maghemite, γ-Fe_2O_3, which is formed by oxidation of Fe_3O_4, near an interface of an anode. The authors argue that the switching motion is originated in a redox reaction between the Fe_3O_4 and γ-Fe_2O_3.
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