查看更多>>摘要：Morphology and chemical composition of the CH3NH3PbI3 films on bare glass and indium tin oxide (ITO) are investigated. The film on bare glass is smoother with a narrow grain size distribution, while the one on ITO is rougher with a large grain size distribution. Energy-dispersive X-ray and X-ray photoelectron spectra reveal that there is a superstoichiometric ratio of CH3NH3+ cations in the upper part of the CH3NH3PbI3 film deposited on ITO. Such a chemical composition segregation originates from the higher affinity of PbI2 to ITO. It is demonstrated that the CH3NH3+ cations can migrate to cathode under applied positive bias, which forms an ionic conductivity and increases the current of the device. Thus the device is in a high conductivity state. A large number of CH3NH3+ cations accumulated near the cathode forms a build-in electric field with a direction opposite to the external field. This restricts further migration of the CH3NH3+ cations and the device turns to a low conductivity state. The migration and accumulation of the CH3NH3+ cations manipulate the device to switch between the high and low conductivity states, endowing the device working as a memristor.
查看更多>>摘要：As the carrier behavior is crucial to the photoelectric conversion process, the charge-carrier engineering could provide feasible strategy for high-performance photodetector (PD). Herein, self-powered ultraviolet PDs were constructed on VOx/Ga2O3 (VGO) heterojunctions by adopting the solution processed VOx films as hole transport layer (HTL). Treated with different annealing ambients, the HTL demonstrated changeable conductivities due to the regulated crystallinities, phase structures and chemical valences, which further exerted influences on the VGO PDs inducing controllable photodetection properties. With effective hole transportation, low valence band barrier and large built-in field, the modulated VGO PDs achieved enhanced self-powered photodetection performance with photo-to-dark current ratio of 1.08 × 108, on/off ratio of 1.23 × 106, rejection ration (R245/R400) of 3.12 × 104, responsivity of 28.9 mA/W and detectivity of 1.13 × 1014 Jones as well as rise/decay time of 57/74 ms. In consideration of the carrier-transport problems are commonly ubiquitous and particularly vital, our proposed HTL engineering method could open the high-performance route for self-powered ultraviolet PDs.
查看更多>>摘要：The study of corrosion on aluminum alloys exposed to alternative fuels, such as ethanol, or bioethanol has been studied and presented in the literature by different researchers. Among signal processing methods reported in the literature can be found the statistical method (SM), the Fast Fourier Transform (FFT), and the Wavelet transform. In the present research, we focused on the corrosion analysis in aluminum proposing an alternative signal processing method (the Stockwell Transform (ST)) and using ethanol-gasoline blends. In this analysis, the metallic material used was aluminum alloy 6061-T6 (Al6061-T6). And the signal processing is carried out by the ST and Shannon energy (SSE) methods. The results showed an average corrosion rate of 3.25 × 10?7mm∕year and 3.81 × 10?4mm∕year in the Al6061-T6 exposed to E0 and E100, respectively. Highlighting that E10 and E20 produced lower corrosion effects, and E60, E80, and E100 caused the highest corrosion levels.
查看更多>>摘要：Recently, perovskite-type oxides have been reported to have outstanding gas sensing performance. However, facile synthesis of uniform materials with controllable morphologies and low limit of detection are still great challenges. In this paper, the synthesis of Ln[Fe(CN)6] (Ln[dbnd]La, Nd, Sm) with novel morphologies was achieved by introducing polyvinyl pyrrolidone (PVP) in dilute water/alcohol solutions to induce and regulate crystal growth using a co-precipitation method at room temperature. Then, the oxygen-vacancy rich LnFeO3 materials were obtained by high-temperature annealing. Among them, LaFeO3-based sensor has a low detection limit of 1 ppm n-propanol with a gas-sensing response of 2.5 at a relatively low operating temperature of 120 °C. In addition, by analyzing the influence of Ln3+ on the morphology and crystal structure of LnFeO3, the reasons for the better gas-sensing performance of LaFeO3-based sensor compared with that of the sensors based on NdFeO3 and SmFeO3 are expounded. This simple method of preparing porous LnFeO3 can be extended to the preparation of other ABO3-type gas-sensing materials using in trace detection.
查看更多>>摘要：The combination of Surface Plasmon Resonance (SPR) effect with hetero-p-n structure has shown promising benefits to photocatalytic activity of catalysts. In this study, Au nanoparticles doped p-n hetero-structured Co3O4/Bi2MoO6 composites were synthesized and subjected to photocatalytic and photocurrent tests using visible light irradiation. The synthesized Au/Co3O4/Bi2MoO6 efficiently removed 97.2% of Methyl orange within 60 min, showing very good photocatalytic stability through leaching test. Colorless pollutant phenol degradation test verified the excellent photocatalytic activity of Au/Co3O4/Bi2MoO6. Possible influential factors such as electron transition, charge transfer, energy band gap, DOS, polarizability, SPR effect, oxygen vacancies and anisotropy permittivity were investigated through DFT, XPS, EPR, Z-scan, UV–visible spectra, ellipsometer spectroscopy and Mott-Schottky analysis. A reasonable degradation mechanism and possible pathway for Methyl orange were proposed based on the experimental results and DFT calculations. The doped Co3O4 provided active 3d electrons transition and charge transfer which increased carriers’ concentration and reduced the energy band gap, while the Au SPR enhanced internal polarization and strengthened the built-in electric field, yielding strong driving force for photo-generated electrons-holes pairs separation and consumption. In addition, magnetic Co3O4 endowed sample with room-temperature ferromagnetism which was obviously strengthened by Au NPs. The magnetism of sample was beneficial for separation and recovery in photocatalytic practical applications.
查看更多>>摘要：Sol–gel approach was employed for synthesis of nickel aluminate (NiAl2O4, NA), and silver doped nickel aluminate (Ag-NiAl2O4, AgNA) nanomaterials. The ultra-sonication approach was employed to synthesize their composite with graphitic carbon nitride (Ag-NiAl2O4@g-C3N4, AgNA@gCN) for degradation of organic effluents such as methylene blue (MB), crystal violet (CV), and benzoic acid (BA) photocatalytically. The synthesized photocatalysts were characterized by various techniques like X-rays diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and UV–visible spectroscopy. XRD confirmed the formation of doped and un-doped NiAl2O4. The crystallite size of as-prepared nanomaterials was found out less than 13 nm. FT-IR technique was used for functional groups detection present in synthesized photocatalysts. The surface morphology of fabricated nanomaterials was investigated via SEM. The thermal stability of prepared samples was investigated via TGA. Optical analysis was carried out by UV-Visible spectrophotometer. NA and AgNA exhibited the bandgap energy of 3.50 eV, and 2.88 eV respectively. The photocatalytic efficiency of fabricated samples was analyzed under solar light. AgNA@gCN exhibited 85.26% degradation of MB, 83.87% of CV, and 68.46% of BA under sunlight. The overall removal (%adsorption + % degradation) of MB, CV, and BA by AgNA@gCN were 99.67%, 98.54%, and 76.91% respectively. The scavenging experiment was also performed to find out the most photoactive species involve in the degradation of organic effluent photocatalytically. Hydroxyl radicals are the mainly photoactive species responsible for the photocatalytic experiment.
查看更多>>摘要：The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.
查看更多>>摘要：Avoiding the weak interface bonding of multi-walled carbon nanotubes MWCNT with Sn-Ag-Cu solder matrix is vital to produce high performance large scale Sn-Ag-Cu solder alloys. In this work, Sn-1.0Ag-0.7Cu (SAC107) composite solders were developed by incorporating MWCNT in SAC107 alloy with Ni and Te. The results indicate that the MWCNTs and Cu can be instantaneously adsorbed at the surface-active of Te atoms to in situ compose the core multi-shell (Te/C/Cu/C) polygonal particles, linking MWCNT with SAC solder matrix. The polygonal particles are well dispersed through the Cu6Sn5, Ag3Sn, β-Sn, SnTe and (Cu,Ni)6Sn5 IMC precipitates. These structural variations produce a combination of increased creep resistance 15 times and enlarged creep life time (14 times) than that of plain SAC107 alloy. Although Ni and Te additions decreased the creep resistance of SAC, the SAC-Ni-Te-MWCNT composite alloy exhibits significant change in dislocation creep resistance with creep stress exponent of ~ 6.6 at 25 °C: the creep threshold stress is decreased by 58.8% (5 MPa) in SAC-Ni-Te alloy, while increased by 17.6% (1.5 MPa) in SAC-Ni-Te-MWCNT composite alloy owing to the presence of polygonal particles.
查看更多>>摘要：In order to enhance the guidance force, adding the high-temperature superconducting (HTS) bulks and permanent magnets in lateral direction is the simplest way especially in curve negotiation situations. However, as the core component of maglev system, permanent magnet guideway (PMG) consists of a huge amount of NdFeB magnets along the operation line. Hence, it means a huge construction cost to add the magnets in lateral direction. To help solving this issue, this paper discusses a PMG improvement methodology based on the widely-used two-pole Halbach PMG. This proposed novel PMG can enhance the guidance force by only adding air intervals between neighbor magnets and the flux-concentration irons and raising the onboard HTS bulks’ width accordingly. Firstly, a 2D electromagnetic theoretical model of the HTS bulk-PMG maglev system was built in the COMSOL Multiphysics. Then, under the different external magnetic fields of the PMGs with different air intervals, levitation and guidance performances of the typical onboard HTS bulk array at typical working conditions were discussed. The results showed that, with the suitable HTS bulks’ width, the guidance force can increase with the intervals increasing in a range. And the HTS maglev system adopting this idea can achieve a guidance force growth of about 41%. This PMG idea is appropriate for curve negotiation situations because of its higher ratio of the guidance force to the levitation force, without changing the basic magnetic circuit and the magnet block number of the previous linear PMG.
查看更多>>摘要：In this work, europium, ytterbium, and lithium doped fluoroperovskite type-KMgF3 (KMgF3:Eu,Yb,Li) was synthesized using the sol-gel method. The structural and luminescence properties of KMgF3:Eu,Yb,Li compound were investigated by radioluminescence, thermoluminescence (TL), and optically stimulated luminescence (OSL) methods. Different contents of the alkali metal lithium (Li) co-dopant have been studied regarding the influence on the structure and luminescence properties. The structures of the samples were studied using the x-ray diffraction (XRD) method. We found cubic-KMgF3 (Parascandolaite) and tetragonal-MgF2 phases for all produced samples. Additional Eu, Yb doping, and Li co-doping resulted in the formation of hexagonal-Li2O2 and cubic-MgO phases while reducing the MgF2 phase in KMgF3 dispersions that were confirmed with XRD and Rietveld refinement analyses. Moreover, the lattice parameters of KMgF3 were calculated for the undoped and Li co-doped samples. Scanning electron microscope images revealed increased crystalline formations with increasing Li concentration in the structure. Fourier transform infrared spectroscopy indicated a reduction of Mg-F bands for all samples due to Mg+2 ion substitutions with Eu, Yb doping, and Li co-doping. It was observed that the intensity of the TL peaks in the TL glow curves appeared as the Li concentration increased without shifting the peak positions as a function of temperature. The OSL curves of KMgF3:Eu,Yb,Li decayed slowly and the luminescence intensity reached a maximum with 15 mol% Li content. The obtained results tend to suggest that the investigated Eu- and Yb-doped and Li co-doped parascandolaite polycrystals exhibit promising luminescent properties and could be considered as appropriate candidates for various technological applications including radiation dosimetry.
NSTL
Elsevier