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Adhesion of Single-walled Carbon Nanotube Thin Films with Different Materials
摘要： Single-walled carbon nanotubes (SWCNTs) possess extraordinary physical and chemical properties. Thin films of randomly oriented SWCNTs have great potential in many opto-electro-mechanical applications. However, good adhesion of SWCNT films with a substrate material is pivotal for their practical use. Here, for the first time we systematically investigate the adhesion properties of SWCNT thin films with commonly used substrates such as glass (SiO2), indium tin oxide (ITO), crystalline silicon (C-Si), amorphous silicon (a-Si:H), zirconium oxide (ZrO2), platinum (Pt), polydimethylsiloxane (PDMS), and SWCNTs for self-adhesion using atomic force microscopy. By comparing the results obtained in air and inert Ar atmospheres we observed a great contribution of the surface state of the materials on their adhesion properties. We found that the SWCNT thin films have higher adhesion in an inert atmosphere. The adhesion in the air can be greatly improved by a fluorination process. Experimental and theoretical analyses suggest that adhesion depends on the atmospheric conditions and surface functionalization.
关键词： adhesion energy,inert atmosphere,Single-walled carbon nanotubes,fluorination,ambient conditions,thin films
更新于2025-09-12 10:27:22
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Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets
摘要： A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (? ≤ 10 μm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 μm < ? < 8 μm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 μm < ? < 80 μm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.
关键词： optical levitation,optical traps,photochemical reactions in Earth’s atmosphere,atmospheric aerosols,laser tweezers Raman spectroscopy (LTRS)
更新于2025-09-12 10:27:22
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Enhancement in photovoltaic properties of bismuth ferrite/zinc oxide heterostructure solar cell device with graphene/indium tin oxide hybrid electrodes
摘要： Integrating of ferroelectric thin films with two-dimensional materials may provide a novel and unique characteristics in the field of optoelectronics due to the coupling of their distinctive intrinsic features. A heterostructure (bismuth ferrite/zinc oxide) device is fabricated with different types of the electrode to enhance the power conversion efficiency (PCE). A single-phase multiferroic BFO thin film is grown by atomic layer deposition (ALD) method and annealed in different environments such as helium, nitrogen, and oxygen. We investigated the effect of annealing parameters and different types of electrodes on solar cell applications. We observed that the leakage current 10 orders of magnitude was reduced by decreasing in the dielectric loss. Further, the power conversion efficiency (PCE) is improved from 4.1% to 7.4% with a hybrid transparent electrode (graphene/indium tin oxide). The value of PCE is further increased at a low temperature. So, the improvement in the key parameter of bismuth ferrite thin-film evidently highlights the importance of annealing atmosphere and graphene as an electrode in BFO thin film applications in optoelectronics.
关键词： Power conversion efficiency,Transparent electrode,Annealing atmosphere,Atomic layer deposition,Graphene,Leakage current
更新于2025-09-12 10:27:22
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Construction of high <i>T</i> <sub/>c</sub> BiScO <sub/>3</sub> -BiFeO <sub/>3</sub> -PbTiO <sub/>3</sub> and its enhanced piezoelectric properties by sintering in oxygen atmosphere
摘要： The high-temperature piezoelectric ceramics 0.36[(1 ? x)BiScO3-xBiFeO3]-0.64PbTiO3 was constructed by introducing BiFeO3 with a high Curie temperature (Tc ～ 830 °C) in the 0.36BiScO3-0.64PbTiO3 binary system. In terms of microstructure, low-melting BiFeO3 plays a role as a sintering aid, lowering the sintering temperature of the ceramic and signi?cantly increasing the grain size. At the same time, the crystal structure shifts from the initial morphotropic phase boundary to the tetragonal phase side, and the Tc increased gradually with increasing BiFeO3 content. Under the conventional air atmosphere sintering conditions, the Tc of the sample with x = 0.3 can reach ～500 °C, and the piezoelectric constant d33 is 125 pC/N. Compared with that, the d33 of the same composition sample sintered in an oxygen atmosphere is increased to 165 pC/N, which is mainly due to the decrease in the content of oxygen vacancies that helps to increase poling electrical ?eld. Moreover, the oxygen-sintered specimen exhibits an excellent thermal stability in a wide temperature range from room temperature to 450 °C, indicating that it is a promising candidate for ultra-high-temperature piezoelectric devices applications.
关键词： high-temperature piezoelectric ceramics,thermal stability,BiScO3-BiFeO3-PbTiO3,sintering in oxygen atmosphere,piezoelectric properties
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Synthetic aperture radar observations of interannual ocean-atmosphere coupling over the Somali Current
摘要： The covariability of wind stress and sea surface temperature is observed at high resolution over the Western Arabian Sea. Synthetic aperture radar data were acquired over the Somali Current in 2016 and 2017 during the summer monsoon season. The Somali Current, the Southern Gyre and the Great Whirl were all observed at the time of these acquisitions. Wind stress curl derived from the synthetic aperture radar data show the effects of the cold upwelled coastal water and the Somali Current on the wind stress. Significant organized large eddies are also observed east of the Somali Current.
关键词： ocean-atmosphere coupling,wind stress,synthetic aperture radar
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Assimilation of Insar Propagation Delay Maps in High-Resolution Numerical Weather Model: Imaging of Water Vapor Structures in Atmosphere
摘要： In this work we present a methodology to estimate the 3D distribution of water vapor in atmosphere based on the use of SAR interferometry (InSAR) and Sentinel-1 data. Maps of propagation delay in atmosphere are assimilated in a high resolution Numerical Weather Model to enhance the forecast of atmosphere parameters. These are used to compute the atmosphere refractivity. Furthermore, 3D maps of hydrometers in atmosphere are derived after the assimilation of InSAR data. Both refractivity and hydrometeors maps are used to map 3D Water vapor patterns in atmosphere. Examples of InSAR signatures of water vapor in atmosphere are shown. We show how the 3D maps liquid refractivity and hydrometeors can be a useful tool to map moisture in atmosphere in case of convective phenomena in atmosphere.
关键词： Atmosphere propagation delay,Water Vapor,Sentinel-1,SAR interferometry,Numerical Weather Model
更新于2025-09-10 09:29:36
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Second-order statistical properties of a J0-correlated Schell-model beam in a turbulent atmosphere
摘要： We derive the analytical expressions for the second-order moments of the Wigner distribution function of a J0-correlated Schell-model (JCSM) beam propagating in a turbulent atmosphere. With the help of the second-order moments, we explore the second-order statistical properties (i.e., the M2-factor, the effective radius of curvature and the Rayleigh range) of a JCSM beam propagating in a turbulent atmosphere for different turbulence parameters and beam parameters. It is found that the statistical properties of the JCSM beam are closely related to the initial beam parameters and turbulence parameters, and we can mitigate the negative effect of the turbulence by choosing suitable initial beam parameters. Our results will be useful for long distance free-space optical communications.
关键词： J0-correlated Schell-model beam,Propagation,Turbulent atmosphere
更新于2025-09-10 09:29:36
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Ammonia in Jupiter’s Atmosphere: Spatial and Temporal Variations of the NH3 Absorption Bands at 645 and 787 Nm
摘要： Based on the material of long-term spectrophotometric observations of Jupiter, we studied the weak absorption bands of ammonia at 645 and 878 nm, whose behavior had previously been little studied. A clearly expressed depression of ammonia absorption in the 787-nm band was found in the Northern Equatorial Belt (NEB) of Jupiter. In the Great Red Spot, this band also exhibits substantial weakening. The position of the depression in the NEB is similar to that of the enhanced brightness temperature detected in the observations of the millimeter-wave radio emission, which is considered to be a result of the reduced ammonia content in this belt. At the same time, the weakening of the 787-nm band in the Red Spot is most likely caused by the enhanced bulk density of clouds, which influences the formation of absorption bands in the multiple scattering by cloud particles. The brightness temperature in the Red Spot is relatively low, as seen from observations in the radio and thermal IR ranges. We studied the spatial and temporal variations of the 645- and 787-nm bands in five belts of Jupiter: the Equatorial Zone (EZ), both Equatorial Belts (SEB and NEB), and both Tropical Zones (STZ and NTZ). The observations covered the time interval from 2005 to 2015, i.e., almost a complete orbital period of Jupiter. These observations confirmed the systematic character of the depression of the 787-nm band in the NEB and the difference in the latitudinal variations of the 645- and 787-nm bands. The latter can be related to features of the vertical distribution of the cloud density, which has a different influence on bands of different intensity.
关键词： spectrophotometry,molecular absorption,atmosphere,thermal radiation,clouds,ammonia,Great Red Spot,Jupiter
更新于2025-09-10 09:29:36
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Convective gravity wave propagation and breaking in the stratosphere: comparison between WRF model simulations and lidar data
摘要： In this work we perform numerical simulations of convective gravity waves (GWs), using the WRF (Weather Research and Forecasting) model. We ?rst run an idealized, simpli?ed and highly resolved simulation with model top at 80 km. Below 60 km of altitude, a vertical grid spacing smaller than 1 km is supposed to reliably resolve the effects of GW breaking. An eastward linear wind shear interacts with the GW ?eld generated by a single convective thunderstorm. After 70 min of integration time, averaging within a radius of 300 km from the storm centre, results show that wave breaking in the upper stratosphere is largely dominated by saturation effects, driving an average drag force up to ?41 m s?1 day?1. In the lower stratosphere, mean wave drag is positive and equal to 4.4 m s?1 day?1. In a second step, realistic WRF simulations are compared with lidar measurements from the NDACC network (Network for the Detection of Atmospheric Composition Changes) of gravity wave potential energy (Ep) over OHP (Haute-Provence Observatory, southern France). Using a vertical grid spacing smaller than 1 km below 50 km of altitude, WRF seems to reliably reproduce the effect of GW dynamics and capture qualitative aspects of wave momentum and energy propagation and transfer to background mean ?ow. Averaging within a radius of 120 km from the storm centre, the resulting drag force for the study case (2 h storm) is negative in the higher (?1 m s?1 day?1) and positive in the lower stratosphere (0.23 m s?1 day?1). Vertical structures of simulated potential energy pro?les are found to be in good agreement with those measured by lidar. Ep is mostly conserved with altitude in August while, in October, Ep decreases in the upper stratosphere to grow again in the lower mesosphere. On the other hand, the magnitude of simulated wave energy is clearly underestimated with respect to lidar data by about 3–4 times.
关键词： atmospheric,waves and tides,dynamics,middle atmosphere dynamics,Meteorology,mesoscale meteorology
更新于2025-09-10 09:29:36
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Broadband LWIR and MWIR absorber by trapezoid multilayered grating and SiO2 hybrid structures
摘要： A broadband metamaterial absorber with high absorption simultaneously in mid-wave infrared (MWIR) and long-wave infrared (LWIR) was proposed. In the MWIR, the absorption higher than 0.8 is from 4 to 6.3 μm, while the absorption in the LWIR is from 8.7 and 9.6 μm. The absorber is insensitive to the incident angle. The broadband absorption in the MWIR is due to the slow-light effect of the trapezoid multilayered grating structure. And the broadband absorption in the LWIR is due to the phonon polariton resonant of trapezoid SiO2 layer. In the broadband high absorption region, the atmosphere is transparent, which may greatly promote the practical application of the absorber in double-color IR imaging, detecting, infrared stealth and thermal emitting.
关键词： Metamaterial,Transparent atmosphere window,Broadband absorber,Slow-light effect,Phonon polariton resonant
更新于2025-09-10 09:29:36