[en] The effect of the addition of a d-rich transition metal Re to Mo on the bcc to hcp phase transformation at high pressures is investigated using Mo-Re alloys with 5, 11, 18, and 26 at. pct Re, fabricated by arc melting. The alloys were cold rolled to a 50-micron-thick foil for studies of transformations under high pressure in a diamond anvil cell. The energy dispersive X-ray diffraction pattern (recorded at Corness High-Energy Synchrotron Source) at the lowest pressure of 0.9 GPa showed that the Mo-26Re was single phase bcc. Typically 15 diffraction peaks of the bcc phase were observed to 70 keV at each pressure, and these peaks were followed to the highest applied pressure of 64 GPa. No discontinuity in the spacing and no new diffracton peaks were observed to 64 GPa, implying that the bcc phase is stable. Theoretical estimates of the transition pressure indicate that studies employing pressures up to several megabars are needed on this alloy to observe the bcc-hcp boundary. 16 refs

[en] Abnormal grain growth (AGG) occurs when SnO₂ thin films are deposited by conventional thermal CVD at 475 deg. C, and high-resolution transmission electron microscopy shows some of the interfaces to be atomically faceted. However, when deposited at 525 deg. C normal grain growth (NGG) occurs with all the interfaces smoothly curved and atomically rough. This correlation between interface structure and grain growth behavior is consistent with that observed previously in bulk materials. For the application of SnO₂ thin films in sensors and transparent electrodes, 525 deg. C, which is just above the faceting transition temperature, was found to be the optimum deposition temperature due to its small grain size and high surface to volume ratio

[en] We systematically synthesized self-aggregated iron nanoparticles in the perfluorinated sulfo-cation membrane (MF-4SK) by ion-exchange method. Our experimental results show that iron nanoparticles in MF-4SK exhibit superparamagnetic properties above the blocking temperature. Field-cooled and zero-field-cooled magnetization data show the blocking temperature, T_B congruent with 120 K for the iron concentration of 5x10¹⁹ atoms per 1 g of polymer film at 500 Oe applied field. This result is well matched with the calculation based on the temperature dependence of the coercivity, which shows T_B congruent with 110 K, with the zero temperature coercivity (H_C0) congruent with 420 Oe. The radius of the typical iron particle is determined to be ∼2 nm from transmission electron microscopy (TEM), showing good agreement with the value acquired by Langevin function fit. These experimental evidences suggest that iron nanoparticles in the polymer film obey a single-domain theory

[en] ⁷Li(p,n), ⁹Be(d,n) reactions can be good neutron sources for interstitial or intracavity treatment of solid tumors. Dosimetry simulations and heat transfer calculations indicate that dose rate must be limited by heat removal from the target. A tube-in-tube prototype has been constructed. The target will be placed at the bottom of the inner tube. The accelerator beam hits the target through the inner tube, generating neutrons. Cooling water runs between the tubes to carry away the heat generated in the target. The outer tube diameter is 6 mm. The inner tube diameter is 3 mm. The length of insertion is 10 cm allowing for interstitial or intracavity irradiation. Experiments are being performed to verify the heat removal from the target using a tandem electrostatic accelerator beam as the heat source with the neutron producing target absent

[en] Plasma-nitrided SiO₂ thin film has been analyzed by synchrotron-radiation-based x-ray absorption and photoelectron spectroscopies (XAS and XPS). High-resolution N 1s XAS and N 1s, O 1s, and Si 2p XPS spectral changes were obtained for different annealing temperatures. N 1s XPS and XAS spectra show that at room temperature, besides the main species of N[Si(O-)_3-x]₃, there exist free moleculelike N₂ and HN[Si(O-)₃]₂, H₂NSi(O-)₃, and N-Si₂O species with surface contaminants. The spectral intensities of the N₂ and the HN[Si(O-)₃]₂, H₂NSi(O-)₃, and N-Si₂O species decrease as the annealing temperature increases, and finally the nitrogen exists dominantly in the form of N[Si(O)₃]₃ species above 820 K, indicating out-diffusion of molecular N₂ and structural reconstruction to form a stable structure upon annealing. The Si 2p and O 1s XPS spectra show that Si^>4+ 2p peak and O 1s peak appear at 103.7 and 534.0 eV, respectively, which are higher binding energies than those of thermally grown oxynitride films with lower coverage on silicon. Upon annealing the sample, these peaks shift towards lower binding energy; ∼0.3 eV for Si^>4+ and 0.4 eV for O 1s. The causes of the peaks appearance at relatively higher binding energy and the peak shift upon annealing are discussed

[en] In order to research the AC loss characteristics of a multi-layered conductor and a shield in a high temperature superconductor (HTS) cable, we prepared two short cable samples, which are the same as the 22.9 kV/50 MVA HTS-cable installed at Gochang test yard of Korea Electric Power Corporation, and attached voltage-leads to both the conductor and the shield. To investigate the effect of transport period on their AC losses, we also applied current with the same magnitude and opposite direction to the conductor and the shield from a few cycles to several minutes. The tests show that the AC loss measured from the lead attached to the shield (shield-lead) is constant regardless of transport period. But the measured loss from the lead attached to the conductor (conductor-lead) is greatly dependent on transport period. It seems to be caused by difficulty in heat transfer to the surrounding coolant due to thick insulator around the conductor. As transport period becomes longer, the conductor's temperature rises and thus the AC loss measured from the conductor-lead increases. In addition, the measured loss from the conductor-lead is 1.5 times larger than that from the shield-lead, particularly for the transport period of a few cycles.

[en] The chemical distributions and electronic structures of Ge_1-xT_x (T=Cr, Fe) diluted ferromagnetic semiconductors have been investigated by employing scanning photoelectron microscopy (SPEM), x-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). The SPEM images and PES spectra of Ge_1-xT_x show the stripe-shaped regions due to the inhomogeneous concentration distributions of T ions. T 2p XAS spectra indicate that T ions are mainly in the divalent states, and that they do not form pure metal clusters. This study reveals that Ge_1-xT_x crystals are chemically phase-separated, suggesting that the observed ferromagnetic ordering in Ge_1-xT_x arises from the magnetic properties of the T-rich Ge_1-xT_x phases

[en] Total electron yield (TEY) measurement was applied to the scanning photoelectron microscopy (SPEM). The resultant image showed the thickness variation of a zinc overlayer deposited on an iron substrate with 18 nm nominal thickness. The contrast and signal-to-noise ratio of the image were much higher than those of the images obtained by the conventional SPEM. When the order-sorting aperture (OSA) located between the Fresnel zone plate and the sample was biased to +80 V relative to the sample, the contrast of the image was further improved. It also made it possible to perform microscopic X-ray absorption spectroscopy in TEY mode by preventing the unwanted photoelectrons emitted from the OSA, which can cause false TEY, from reaching the sample. Oxidized areas of the iron substrate under the thick zinc overlayer were clearly identified

[en] The energy calibration and the measurement of spectral resolving power (E/E-utri) of the monochromator are important, especially in near-edge x-ray absorption fine structure (NEXAFS) and x-ray photoemission spectroscopy (XPS) application. For the soft x-ray beam lines covering 100 - 1000 eV photon energy range, the best way of these is to use a gas cell and an XPS setup with a well-defined work function and a cooling system. Typically, the N 1s → π* absorption spectrum has been used as a reference for energy calibration and the visibility of the spectrum has been a good measure of the monochromator energy resolution. However, the gas cell is rather inconvenient in case of frequent uses, because it needs a dedicated experimental setup. In this manuscript, we introduce a solid sample that can be used for the energy calibration and for the measurement of spectral resolving power (RP) of the monochromator. The sample is a plasma nitrided SiON. The N 1s absorption spectrum of the sample at room temperature shows a spectral feature of nitrogen in free molecular state. The spectral resolving power that can be measured with this sample is as high as 3,000. The accuracy of energy calibration obtained with this sample is 130 meV at the photon energy of 400 eV. This sample is stable in air when stored at room temperature, except some contaminations on the surface; the absorption spectrum shows almost the same spectral feature after 6 months of air storage. We believe this sample can be usefully used in calibrating the photon energy and measuring the energy resolution of the monochromator for the soft x-ray beam lines which may not require higher spectral resolving power than 3,000

[en] Two voltage-leads (inner-lead, outer-lead) were soldered to the wires in each layer. Voltage-lead (total-lead) was soldered to the inner layer and arranged on the surface of the outer layer. The loss from the total-lead significantly differs from the sum of the wire losses. In order to investigate the AC loss of the multilayer conductor in a high temperature superconductor cable, a voltage-lead was generally attached to the outermost layer of the conductor. But the conductor's AC loss has not been completely cleared due to the various contact positions and arrangements of the voltage-lead. In this paper, we prepared a semi-triple layer conductor consisting of an inner layer and an outer layer with double layer structure. To measure the AC loss of the conductor, two voltage-leads (inner-lead, outer-lead) were soldered to the wires in each layer and arranged along their surfaces, as well as another voltage-lead (total-lead) was soldered to the inner layer and arranged on the surface of the outer layer. The results show that the AC losses for each layer measured from the inner-lead and the outer-lead, respectively, are identical to the sum of the wire losses. The AC losses in the semi-triple layer conductor measured from the total-lead and the outer-lead are identical for the uniform layer current density, and similar to the sum of the wire losses in both layers. However, the losses measured for the non-uniform layer current density from three voltage-leads are unequal to each other, and the loss from the total-lead significantly differs from the sum of the wire losses.