Capacitively coupled octafluorocyclobutane (C4F8) plasma was used to synthesize fluorocarbon films on low-density polyethylene, which was surface-crosslinked by treatment with inductively coupled Ar ...plasma. The dependence of the thickness, surface morphology, and chemical characteristics of the fluorocarbon films on the plasma power was studied under different plasma conditions. Significantly lower deposition rates were obtained under the sole effect of uncharged particles (shielded plasma conditions). Microscale and nanoscale film growth characteristics were examined at different levels of energy/monomer mass. A significant increase in hydrophobicity was observed under shielded plasma conditions as a result of the higher fluorine concentrations of the deposited films. The film chemical structures were interpreted in terms of the degree of crosslinking. Increasing the exposure of polyethylene to the shielded plasma conditions resulted in the formation of fluorocarbon films with hybrid chemical structures consisting of a crosslinked interfacial layer covalently bonded to the polymer substrate and a hydrophobic compliant surface layer rich in CF2 groups. The results of this study illustrate the potential of shielded plasma treatment to tailor the chemical structure of thin fluorocarbon films.
Detailed neutron scattering measurements of YBa2Cu3O6.95 found that the resonance peak and incommensurate magnetic scattering induced by superconductivity represent the same physical phenomenon: two ...dispersive branches that converge near 41 meV and the in-plane wave vector q(AF)=(pi/a,pi/a) to form the resonance peak. One branch has a circular symmetry around q(AF) and quadratic downward dispersion from approximately 41 meV to the spin gap of 33+/-1 meV. The other, of lower intensity, disperses from approximately 41 meV to at least 55 meV. Our results exclude a quartet of vertical incommensurate rods in q-omega space expected from spin waves produced by dynamical charge stripes as an origin of the observed incommensurate scattering in optimally doped YBCO.
In this paper, we present an innovative CH4, δ13CH4, and C2H6 instrument based on cavity ring-down spectroscopy (CRDS). The design and performance of the analyzer is presented in detail. The ...instrument is capable of precision of less than 1 ‰ onδ13CH4 with 1 in. of averaging and about 0.1 ‰ in an hour. Using this instrument, we present a comprehensive approach to atmospheric methane emissions attribution. Field measurements were performed in the Uintah Basin (Utah, USA) in the winter of 2013, using a mobile lab equipped with the CRDS analyzer, a high-accuracy GPS, a sonic anemometer, and an onboard gas storage and playback system. With a small population and almost no other sources of methane and ethane other than oil and gas extraction activities, the Uintah Basin represents an ideal location to investigate and validate new measurement methods of atmospheric methane and ethane. We present the results of measurements of the individual fugitive emissions from 23 natural gas wells and six oil wells in the region. The δ13CH4 and C2H6 signatures that we observe are consistent with the signatures of the gases found in the wells. Furthermore, regional measurements of the atmospheric CH4,δ13CH4, and C2H6 signatures throughout the basin have been made, using continuous sampling into a 450 m long tube and laboratory reanalysis with the CRDS instrument. These measurements suggest that 85±7 % of the total emissions in the basin are from natural gas production.
We developed a very simple and new joint technique for coated conductors that could achieve a very low resistance less than 0.02μΩ across the joint with an area of 2×20mm2 without any degradation of ...Ic. It is a diffusion joint using the Ag stabilizing layer of YBCO coated conductors. Two tapes were stuck with Ag stabilizing layer in contact in a face to face manner and were pressed uniaxially during a heat treatment from 500°C to room temperature in a pure oxygen atmosphere. The relationship between the joint pressure, the joint structure and Ic were studied.
We performed optical spectroscopy on a thin film of FeSe, in which orbital ordering shows up in the orthorhombic phase below Ts. The optical conductivity spectrum for FeSe exhibits no gap feature in ...the orbitally ordered state, in contrast to those for iron pnictides showing the gap opening in the magnetostructurally ordered phase. Instead, we observed a gradual suppression of the coherent carrier density with temperature. This highlights a peculiar metallic state in FeSe that the Fermi surfaces are gradually modified below Ts. We also found an anomalous behavior of the optical phonon mode, indicating the intimate connection between the orbital and lattice degrees of freedom. The result implies the orbital origin of the structural transition.
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