Migration study of iodine in Beishan granite by a column method

The fate and migration behavior of radionuclides in environment are influenced by a series of physical and chemical processes such as advection, hydrodynamic dispersion (including mechanical dispersion and molecular diffusion), retention, chemical reaction and so on. In this study, the migration of ¹²⁵I^? in Beishan granite and the potential retention of iodine by silver halide additives were investigated by a pulse injection column method. All breakthrough curves were analyzed according to the analytical solution of transport equation and the dispersion coefficient (D), and first-order sorption constant (k) were obtained. For conservative nuclide, the dispersion behavior is only related to the dispersion medium. Silver halides were proved having sorption ability for ¹²⁵I^? in the order of AgCl > AgBr > AgI. The transport of iodine in the crushed granite column can be adequately described by the advection–dispersion equation with a first-order, irreversible sorption term. The pulse injection column method can be used as a fast method to evaluate the sorption or retention ability of solid phase.     

Study of the electrocaloric effect in ferroelectric liquid crystals

ABSTRACT

Electrocaloric effect (ECE) in two ferroelectric liquid crystalline (FLC) materials has been evaluated by mean of two indirect characterization methods: the photopyroelectric (PPE) technique and the polarization current reversal one. The obtained results show a good correspondence of the adiabatic temperature change associated with the ECE evaluated from both methods. This validates the possibility to use the PPE technique to investigate the ECE in FLCs. This study also demonstrates that FLCs can be used as electrocaloric material. More particularly, it shows that as for their solid homologous, liquid crystals displays more pronounced ECE in the vicinity of a first order transition than that measured near to second-order one.     

Etching Characteristics and Mechanisms of Mo and Al2O3 Thin Films in O2/Cl2/Ar Inductively Coupled Plasmas: Effect of Gas Mixing Ratios

An investigation of etching behaviors for Mo and Al₂O₃ thin films in O₂/Cl₂/Ar inductively coupled plasmas at constant gas pressure (6 mTorr), input power (700 W) and bias power (200 W) was carried out. It was found that an increase in Ar mixing ratio for Cl₂/Ar plasma results in non-monotonic etching rates with the maximums of 160 nm/min at 60 % Ar for Mo and 27 nm/min at 20 % Ar for Al₂O₃. The addition of O₂ in the Cl₂/Ar plasma causes the non-monotonic Mo etching rate (max. 320 nm/min at 40–45 % O₂) while the Al₂O₃ etching rate decreases monotonically. The model-based analysis of etching kinetics allows one to relate the non-monotonic etching rates in Cl₂/Ar plasma to the change in the etching regime from the ion-flux-limited mode (at low Ar mixing ratios) to the neutral-flux-limited mode (for high Ar mixing ratios). In the Cl₂/O₂/Ar plasma, the non-monotonic Mo etching rate is probably due to the change in reaction probability.     

Electrical properties of La0.6Ca0.4MnO3–Bi3.4Nd0.6Ti3O12 thin films derived by a sol–gel process

Magnetoelectric (ME) xLa_0.6Ca_0.4MnO₃–(1 ? x)Bi_3.4Nd_0.6Ti₃O₁₂ (LCMO–BNT) composite thin films have been prepared by a sol–gel process and spin-coating technique. The effects of LCMO content on the microstructure, leakage current density, ferroelectric properties, fatigue endurance and ME voltage coefficient of LCMO–BNT thin films derived by sol–gel method were studied. It was found that the composite thin films have better fatigue endurance properties and lower leakage current densities compared with pure BNT thin films, as well as large ME voltage coefficients.     

Development of Plasma Window for gas charge stripper at RIKEN RIBF

A differential pumping system with a Plasma Window (PW) has been developed for an application to a window-less He gas charge stripper. A PW with Southern Methodist University design was newly fabricated and tested off-line for evaluation of differential pumping efficiency. Switching gases for plasma seed from Ar to He was tested. It was found that the PW reduced the pressure at the first differential pumping section to 1/13 for Ar and to 1/17 for He, comparing with differential pumping without PW. At the second pumping section, the pressures were drastically reduced to 1/160 and to 1/4,520 for Ar and He, respectively. These pressure reduction factors indicate that one differentially pumped stage could be removed from a conventional differential pumping system.     

Characterization of long-term dose stability of N-isopropylacrylamide polymer gel dosimetry

In this study, the detailed characteristics, including spatial uniformity, dose distributions, inter-batch variability, reproducibility, and long-term temporal stability, of N-isopropylacrylamide (NIPAM) polymer gel dosimeter were investigated. A commercial 10x fast optical computed tomography scanner (OCTOPUS^TM-10×, MGS Research, Inc., Madison, CT, USA) was used to measure NIPAM polymer gel dosimeter. A cylindrical NIPAM gel phantom that measured 10 cm × 10 cm was irradiated via a single-field treatment plan with a field size of 4 cm × 4 cm. The maximum standard deviation of spatial uniformity for NIPAM gel was less than 0.29 %. The average standard deviation among the three batches of gel dosimeters was less than 1 %. The gamma pass rate could reach as high as 96.76 % when a 3 % dose difference and a 3 mm dose-to-agreement criteria were used. The long-term measurement of irradiated NIPAM gel dosimeter indicated that the dose maps attained a gradually stable value 15 h post-irradiation and remained stable until 72 h post-irradiation. The gamma pass rate could achieve a maximum value between 24 and 72 h post-irradiation. The edge enhancement effect that occurred around the irradiated region was observed 72 h post-irradiation. Thus, the results from this study suggest that NIPAM gel dosimeter should be measured approximately 24 h post-irradiation to reduce the occurrence of the edge enhancement effect.     

Development and validation of a sensitive thermal desorption–gas chromatography–mass spectrometry (TD-GC-MS) method for the determination of phosgene in air samples

A new rapid, sensitive and reliable method was developed for the determination of phosgene in air samples using thermal desorption (TD) followed by gas chromatography–mass spectrometry (GC-MS). The method is based on a fast (10 min) active sampling of only 1 L of air onto a Tenax® GR tube doped with 0.5 mL of derivatizing mixture containing dimercaptotoluene and triethylamine in hexane solution. Validation of the TD-GC-MS method showed a low limit of detection (40 ppbv), acceptable repeatability, intermediate fidelity (relative standard deviation within 12 %) and excellent accuracy (>95 %). Linearity was demonstrated for two concentration ranges (0.04 to 2.5 ppmv and 2.5 to 10 ppmv) owing to variation of derivatization recovery between low and high concentration levels. Due to its simple on-site implementation and its close similarity with recommended operating procedure (ROP) for chemical warfare agents vapour sampling, the method is particularly useful in the process of verification of the Chemical Weapons Convention.

Syngas production by biogas reforming over the Co-based multicomponent catalysts

The new multicomponent Co-based catalysts with additives of group 8 metal and rare earth elements and supported on alumina have been tested in the dry and steam conversion of a model biogas. The processes were carried out in a flow quartz reactor under the following conditions: atmospheric pressure, a gas hourly space velocity of 1000 h^?1 and temperatures of 300–800°C. The catalysts were characterised using electron microscopy, BET and X-ray analysis. The methane is almost completely converted in the dry reforming of biogas at T≤800°C. Synthesis gas with a ratio of H₂/CO>1.0 is a main product of biogas reforming over the multicomponent catalysts studied. Adding steam in a feed composition increases both the methane conversion and the hydrogen yield at lower temperatures. Almost complete methane conversion occurs at T<750°C in the steam reforming of biogas. The catalysts are highly effective and exhibit stable activity throughout 100 h of continuous testing.      

Spatially‐resolved and polarized Raman scattering from a single Si nanowire

We report spatially‐resolved and polarized Raman scattering results from a single Si nanowire (NW). Transmission electron microscope images show that the surface morphology of the Si NW varies from smooth to rough along the long axis. As the NW grows, the smooth surface becomes rough because of Au diffusion to the surface, resulting in the formation of facets and stacking faults. Spatially‐resolved Raman spectra along the NW long axis reveal variations in tensile strain related to the morphological changes in NW surface. The tensile strain in the top segment of the NW with a smooth surface is greater than that in the bottom segment with a rough surface. Despite the formation of facets and stacking faults, polarized Raman scattering results both from the top and bottom segments of the NW are consistent with the Raman polarization selection rules expected for a cubic crystal. Copyright © 2015 John Wiley & Sons, Ltd.