Gravitational level effects o optical properties of electrodeposited ZnO nanowire arrays

The coupling phenomena between the interfacial reaction rate and the microstructural/morphological variation rate must be reasonably well controlled to fabricate nano/meso- structural devices in a large scale. Otherwise, the physical property uniformity inside the device is not guaranteed to lose its superiority in the market. Free standing ZnO nanowire array was successfully synthesized on ITO/FTO substrate by template-free method in Zn(NO3)2 aqueous solutions. Two types of electrode configurations were employed in order to quantitatively examine the effect of gravitational strength on electrodeposited ZnO nanowire array: (a) a horizontal cathode surface facing downward over an anode (C/A) and (b) an anode over a cathode (A/C). The former configuration may simulate the microgravitational environment, because macroscopic natural convection is not induced. PL of ZnO nanowire array was measured. More uniform nanowires are synthesized in C/A configuration than in A/C. Seeding ZnO nanoparticles on ITO/FTO substrate can control the diameter as well as the orientation. Please click Additional Files below to see the full abstract

Shear Layer Generation in Yield Behavior of Gels

The shear layer generation at the yield point and its recovery process are observed by the twin-drive rheometer. When the stress-ramp test or the shear rate-ramp test is applied to the colloidal gels, the stresses acting on the plates show different values under certain conditions. The bottom plate is used as a driving side, and the stress is controlled. Additionally, the upper plate side is a fixed side. The stress acting on the upper plate increases with the bottom plate, but at the occurrence of the yield behavior the different curve from the bottom plate is suddenly revealed. The stress acting on the upper plate becomes low, and the difference between the two stresses increases with an increasing stress or shear rate. This means that the shear stress is not constant over the gap, and a shear layer is generated. In the case of a small stress-ramp rate, the stress on the upper plate becomes the bottom value from the bottom plate stress at the yield point, but it returns to the same curve a few seconds later. The two layers of the shear layer generated at the yield point are adhered by the structure recovery, and the shear layer then disappeared

Stoner gap in the superconducting ferromagnet UGe2

We report the temperature ($T$) dependence of ferromagnetic Bragg peak intensities and dc magnetization of the superconducting ferromagnet UGe2 under pressure ($P$). We have found that the low-$T$ behavior of the uniform magnetization can be explained by a conventional Stoner model. A functional analysis of the data produces the following results: The ferromagnetic state below a critical pressure can be understood as the perfectly polarized state, in which heavy quasiparticles occupy only majority spin bands. A Stoner gap $\Delta(P)$ decreases monotonically with increasing pressure and increases linearly with magnetic field. We show that the present analysis based on the Stoner model is justified by a consistency check, i.e., comparison of density of states at the Fermi energy deduced from the analysis with observed electronic specific heat coeffieients. We also argue the influence of the ferromagnetism on the superconductivity.Comment: 5 pages, 4 figures. to be published in Phys. Rev.

Processing conditions for (Nd, Eu, Gd)-Ba-Cu-O ternary bulk superconductors

Abstract(Nd, Eu, Gd)-Ba-Cu-O ternary bulk superconductors have high potential for practical applications since they exhibit very high critical current densities and thus high field trapping capabilities. (Nd, Eu, Gd)-Ba-Cu-O superconductors are synthesized in a reduced oxygen atmosphere, which requires a control of oxygen partial pressure and needs a special device for hot seeding. In the present study, for simplicity, we employed Ar gas flow into the furnace to control oxygen partial pressure instead of flowing oxygen-controlled gas. Hence, it was necessary to modify the melt processing conditions to produce a single domain. Through the optimization of seeding temperature and cooling rate, we obtained the processing conditions, in which a single domain bulk (Nd, Eu, Gd)-Ba-Cu-O of 20mm diameter could be synthesized

Electrodeposition of Metals in Microgravity Conditions

Metal electrodeposition may introduce various morphological variations depending on the electrolytic conditions including cell configurations. For liquid electrolytes, a precise study of these deposits may be complicated by convective motion due to buoyancy. Zero-gravity (0-G) condition provided by drop shaft or parabolic flight gives a straightforward mean to avoid this effect: we present here 0-G electrodeposition experiments, which we compare to ground experiments (1-G). Two electrochemical systems were studied by laser interferometry, allowing to measure the concentration variations in the electrolyte: copper deposition from copper sulfate aqueous solution and lithium deposition from an ionic liquid containing LiTFSI. For copper, concentration variations were in good agreement with theory. For lithium, an apparent induction time was observed for the concentration evolution at 1-G: due to this induction time and to the low diffusion coefficient in ionic liquid, the concentration variations were hardly measurable in the parabolic flight 0-G periods of 20 seconds