纳米尺寸的ZnO晶体高压相变的拉曼散射研究(英文)

Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The…     

Effects of Ti content on the optical and structural properties of the Ti-doped ZnO nanoparticles

This study investigates the effect of Ti content on the optical and structural properties of the Ti-doped ZnO (Ti_xZn_1?xO) nanoparticles by x-ray diffraction, scanning electron microscopy, photoluminescence and Raman scattering measurements. A dependence of luminescent properties and crystal structure upon Ti content has been found. The band-edge-luminescence (BEL) intensity of Ti_0.10Zn_0.90O at room temperature was nearly 1.7 times higher than that of ZnO. The enhanced BEL intensity is attributed to a decrease in the oxygen-vacancy density. However, the lower BEL intensity of Ti_0.15Zn_0.85O than Ti_0.10Zn_0.90O is attributed to an increase in the probability of nonradiative recombination. In addition, the intensity of the x-ray diffraction peaks remarkably decreases with increasing Ti content, suggesting weakened crystallinity.     

Active dielectric metasurface based on phase‐change medium

We propose all‐dielectric metasurfaces that can be actively re‐configured using the phase‐change material Ge₂Sb₂Te₅ (GST) alloy. With selectively controlled phase transitions on the composing GST elements, metasurfaces can be tailored to exhibit varied functionalities. Using phase‐change GST rod as the basic building block, we have modelled metamolecules with tunable optical response when phase change occurs on select constituent GST rods. Tunable gradient metasurfaces can be realized with variable supercell period consisting of different patterns of the GST rods in their amorphous and crystalline states. Simulation results indicate a range of functions can be delivered, including multilevel signal modulating, near‐field coupling of GST rods, and anomalous reflection angle controlling. This work opens up a new space in exploring active meta‐devices with broader applications that cannot be achieved in their passive counterparts with permanent properties once fabricated.

     

Self-assembled structures of 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol in hydrophobic polymer matrices prepared using different heat treatments

Journal of Nanoparticle Research - Ni-doped (CeO2?δ )–YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been...     

Search for color singlet technicolor particles in p&pmacr; collisions at radicals = 1.8 TeV

We search for color singlet technirho and technipion production in p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded with the Collider Detector at Fermilab. These exotic technimesons are present in a model of walking technicolor. The signatures studied are lepton plus two jets plus E(T) and multijet final states. No excess of events is seen in either final state. We set an upper limit on the technirho production cross section and exclude a region in the technipion mass versus technirho mass plane.     

Diffractive dijets with a leading antiproton in &pmacr;p collisions at sqrt

We report results from a study of events with a leading antiproton of beam momentum fraction 0.9057 GeV. Using the dijet events, we evaluate the diffractive structure function of the antiproton and compare it with expectations based on results obtained in diffractive deep inelastic scattering experiments at the DESY ep collider HERA.     

Phthalocyanines bearing bulky cycloalkylmethyl substituents on non-peripheral sites

Octasubstituted phthalocyanines bearing bulky (cyclopentyl)methyl- and (cyclohexyl)methyl-substituents in non-peripheral positions are prepared and characterised. The synthesis of the precursor phthalonitriles is achieved through nickel-catalysed cross-coupling employing alkylzinc reagents. In the case of the (cyclopentyl)methyl derivative the formal precursor is 5-hexenyl bromide which yields the cyclised material exclusively on formation of the zinc reagent and subsequent cross-coupling.     

Fabrication and transformation of dense SnO2 via laser ablation condensation

Dense SnO₂ nanocondensates with fluorite-type-related structures have been synthesized via severe heating-cooling under energetic Nd-YAG laser pulse irradiation of the Sn target in oxygen ambient. Transmission electron microscopic observations indicated that the fluorite type transformed in a martensitic manner into a baddeleyite-type structure with accompanied dislocations, twinning, commensurate shearing and shape change. The Pa3¯-modified fluorite-type structure was hardly observed possibly due to its transformation into α-PbO₂ type and then rutile-type structures in the dynamic process.     

Two-phase flow pressure change subject to sudden contraction in small rectangular channels

This study investigates the pressure change and flow pattern subject to the influence of sudden contractions. The air and water mixture flows from small rectangular channels (2 × 4, 2 × 6, 4 × 4 and 4 × 6 mm, respectively) into a 2 mm diameter tube. The total mass flux (G) ranges from 100 to 700 kg/m² s with gas quality (x) being varied from 0.001 to 0.8. In general the contraction pressure change increases with the rise of mass flux, and gas quality but an unique deflection of contraction pressure change pertaining to liquid vena contracta at a very low gas quality is encountered at a very low gas quality in the 4 ± 6 mm test section. For a low gas quality, elongated bubble prevails after the contraction, yet the size of elongated bubbles is reduced when the aspect ratio is increased. Comparisons amid the pressure change data of this study and available literature data with the predictions of existing model/correlations indicate that none of them can accurately predict the data. It is found that the influence of surface tension and outlet tube size, or equivalently the Bond number plays a major role for the departure of various models/correlations. Among the models/correlations being examined, the homogeneous model shows a little better than the others. Hence by taking account the influences of gas quality, Bond number, Weber number and area contraction ratio into the homogeneous model, a modified homogeneous correlation is proposed that considerably improves the predictive ability over existing correlations with a mean deviation of 30% to all the data.