Structural evolutions of tungsten oxide(WO3) samples on different substrates are studied using Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy. The WO3 samples are prepared using hot-filament CVD techniques. The focus of the study is on the evolutions of nano structures at different stages following deposition time. The experimental measurements reveal evolutions of the surface structures from uniform film to fractal-like structures, and eventually to nano particles, and crystalline structures from mono (0 1 0) crystalline thin film to polycrystalline thick film developments. The effect of high temperature on the nanostructured WO3 is also investigated. Well-aligned nanoscale WO3 rod arrays are obtained at a substrate temperature of up to 1400 °C. Further increasing the substrate temperature yields microscale crystalline WO3 particles.
One-dimensional carbon nanostructures were synthesized at ambient pressure on molybdenum substrates using the pulsed laser deposition techniques. Scanning electron microscopy images revealed the evolutions of the nanostructures for different substrate temperatures, but otherwise identical growth conditions. Transmission electron microscopy images showed that the obtained carbon nanorods were about 20 nm in diameter and 1 µm in length. The crystallographic structures, chemical compositions and bond structures of the carbon materials were investigated using x-ray diffraction, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and Raman scattering spectroscopy, respectively.The electron field emission behaviours of the carbon nanostructures were considerably improved with the increase in substrate temperature. The rod-shaped nanostructures synthesized at 600 °C geometrically increase the effective emission sites, which consequently leads to a high value of field enhancement factor.
A parametric study on the energy transfer of the solar wind across the magnetopause entering the magnetosphere is conducted using a global magnetohydrodynamic numerical simulation. The characteristics of the mechanical and electromagnetic energy distribution under the dawn–dusk interplanetary magnetic fields (IMFs) are investigated by analyzing magnetic reconnection and viscous effect, and compared with the radial and north–south IMFs. It is shown that (1) the interactions at the magnetopause and the transfer of energy across this boundary move in relation to the IMF orientation. (2) For the duskward IMF, the mechanical energy flow clearly enters the equatorial and low-latitude regions on the dayside, and the electromagnetic energy flow has a small inflow on the equatorial and low latitudes of the dayside. A significant energy inflow appears on the dawn side in the northern hemisphere and the dusk side in the southern hemisphere near the polar cusp. (3) The energy distribution characteristics across the magnetopause under dawn–dusk IMFs are mirror symmetric about the $$Y=0$$ Y = 0 plane. (4) For a magnetic field of 5 nT, the electromagnetic energy input under the dawn–dusk IMFs is twice as large as the mechanical energy and the electromagnetic energy under the radial IMF, which is five times as large as the electromagnetic energy during the pure northward IMF, but only half as large as the electromagnetic energy under the pure southward IMF. The mechanical energy input under dawn–dusk IMFs has the same magnitude as that under radial and north–south IMFs. The magnitude of the energy transfer rate for the dawn IMF and dusk IMF (about 3.5%) is between 1.71% for the northward IMF and 4.95% for the southward IMF, but higher than 2.22% for the radial IMF. The Akasofu-type energy-coupling formula, $$\varepsilon$$ ε , underestimates the energy input from the solar wind under $$B_{y}$$ B y dominated IMF.
One-dimensional tilted carbon nanorod arrays were synthesized on molybdenum substrates by using the catalyst-assisted oblique angle deposition technique. The structures of the one-dimensional tilted carbon nanorods evolve with substrate temperatures, but otherwise identical growth conditions. The crystallographic structures, chemical compositions and bond structures of the tilted carbon nanorods were investigated by using x-ray diffraction, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and Raman scattering spectroscopy. The cross-sectional SEM image showed that multilayered tilted carbon nanorods were also obtained. The electron field emission (FE) behaviours of the obtained one-dimensional carbon tilted nanorod arrays were greatly improved with the increase in substrate temperature. Meanwhile, the sample with multiple layers of carbon tilted nanorods exhibits better FE behaviours than those with single layer.
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