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Study of thermal conductivity of synthesized Al2O3-water nanofluid by pulsed laser ablation in liquid
摘要： In the present study, Aluminum oxide (Al2O3) nanoparticles dispersed water based nanofluids were prepared via laser ablation in liquid method. Al2O3 nanoparticles were synthesized in deionized water using a nanosecond Nd-YAG pulsed laser operating at 1064 nm. The structural, optical and morphological characterizations of the produced nanofluids were performed. Thermal properties of the prepared samples were evaluated through thermal conductivity measurements which were carried out at various nanoparticles concentration and at temperatures ranging from 25 °C to 45 °C. Morphological analysis by transmission electron microscopy revealed spherically shaped Al2O3 nanoparticles with an average size of 9 nm. Moreover, the results indicated that the thermal conductivity of Al2O3-water nanofluid was improved as compared to the pure water. The increase in temperature and nanoparticles concentration leads to higher thermal conductivity of nanofluids. It was found that the thermal conductivity enhancement was around 8.6% at nanoparticles volume fraction of 0.7 vol.% and temperature of 45°C. This work proved the possibilities of fabricating Al2O3-water nanofluid with enhanced thermal conductivity via laser ablation in liquid medium without the use of hazardous chemicals and vacuum conditions. Therefore, the synthesized nanofluids have great potential to be applied in medium temperature applications.
关键词： thermal conductivity,nanofluids,temperature,Al2O3 nanoparticles,laser ablation
更新于2025-09-23 15:19:57
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Electrical Properties of Pure NiO and NiO:Ag Thin Films Prepared by Pulsed Laser Deposition
摘要： The electrical properties of pure NiO and NiO:Ag films which are deposited on glass substrate with various dopant concentrations (1wt%, 2wt%, 3wt% and 4wt%) at room temperature and 450 °C annealing temperature will be presented. Further, the structural properties were investigated by X-ray diffraction and the surface morphology of the deposited samples was examined by SEM. The results of the Hall effect showed that all the films were p-type. Hall mobility decreases while both carrier concentration and conductivity increase with the increasing of annealing temperatures and doping percentage, Thus, the behavior of semiconductor, and also the DC conductivity from which the activation energy decreases with the doping concentration increase and transport mechanism of the charge carriers can be estimated.
关键词： Hall effect,Electrical conductivity,NiO:Ag thin films,Pulsed laser deposition
更新于2025-09-23 15:19:57
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Ionic conductivity enhancement of a??soggy sanda?? electrolytes with AlOOH nanofibers for dye-sensitized solar cells
摘要： As one of the main components, inorganic nanofillers have important effect on the performance of “soggy sand” electrolytes. In this study, we first incorporate AlOOH nanofibers into ionic liquid electrolytes to enhance the mechanical property and ionic conductivity of the electrolytes. The AlOOH nanofiber has high aspect ratio coupled with favorable surface properties such as rich hydroxyl groups, which facilitate to interact with cations of ionic liquids, promote salt dissociation, and form stable gels by self-assembly. In addition, the nanofiber fillers with high aspect ratio can form ion-conducting network channels and longer-range continuous ion transport pathways. The enhancing ionic conductivity of “soggy sand” electrolytes and performance of DSSCs due to addition of AlOOH nanofibers are systematically investigated by various techniques. The highest ionic conductivity of “soggy sand” electrolyte reaches 3.69 mS cm?1 at room temperature, which is 4 times than that of the pristine ionic liquid electrolyte. The effective solidification by AlOOH nanofibers provides substantial improvements in stability. The “soggy sand” electrolytes with AlOOH nanofibers can significantly improve the performance of devices by accelerating charge transport, reducing electron recombination and increasing charge collection efficiency. The DSSC with AlOOH nanofibers in electrolyte yields a high efficiency up to 7.89%, which is 29% higher than that of the reference device.
关键词： Nanofiber,Dye-sensitized solar cell,Ionic liquid,“Soggy sand” electrolyte,Ionic conductivity
更新于2025-09-23 15:19:57
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Formation of flexible nano-organic films of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine for promising optoelectronic applications
摘要： Porphyrin compounds are novel nonlinear materials that are being used in a wide range of optoelectronic applications. In this article, a film of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TTBTP) was produced by a thermal evaporation technique. IR analysis confirmed that this method is an excellent method to obtain unassociated TTBTP films. The surface topography of the TTBTP was characterized by large spherical granules with a mean diameter of 50 nm. Also, using X-ray diffraction analysis, the size of the crystallite was estimated to be 18.20 nm. Moreover, optical absorption analysis showed that TTBTP films have indirect transition energy with two energy gaps of 1.80 ? 0.03 and 2.95 ? 0.03 eV. The electrical analysis showed that TTBTP film is a semiconductor material with two conduction mechanisms. These two mechanisms are extrinsic and intrinsic conductions with activation energies of 0.057 ? 0.006 eV and 0.556 ? 0.060 eV, respectively.
关键词： Optical properties,IR analysis,Electrical conductivity,Porphyrin,Organic film
更新于2025-09-23 15:19:57
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Anomalous Fano Resonance in Double Quantum Dot System Coupled to Superconductor
摘要： We analyze the influence of a local pairing on the quantum interference in nanoscopic systems. As a model system we choose the double quantum dot coupled to one metallic and one superconducting electrode in the T-shape geometry. The analysis is particularly valuable for systems containing coupled objects with considerably different broadening of energy levels. In such systems, the scattering of itinerant electrons on a discrete (or narrow) energy level gives rise to the Fano-type interference. Systems with induced superconducting order, along well understood fano resonances, exhibit also another features on the opposite side of the Fermi level. The lineshape of these resonances differs significantly from their reflection on the opposite side of the Fermi level, and their origin was not fully understood. Here, considering the spin-polarized tunneling model, we explain a microscopic mechanism of a formation of these resonances and discuss the nature of their uncommon lineshapes. We show that the anomalous Fano profiles originate solely from the pairing of nonscattered electrons with scattered ones. We investigate also the interplay of each type of resonances with the Kondo physics and discuss the resonant features in differential conductivity.
关键词： Kondo physics,Fano-type interference,quantum interference,spin-polarized tunneling model,differential conductivity,double quantum dot,superconducting electrode,nanoscopic systems
更新于2025-09-23 15:19:57
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Coupled Electrical Conduction in Coordination Polymers: From Electrons/Ions to Mixed Charge Carriers
摘要： The coupled transport of ions and electrons is of great potential for next-generation sensors, energy storage and conversion devices, optoelectronics, etc. Coordination polymers (CPs) intrinsically have both transport pathways for electrons and ions, however, the practical conductivities are usually low. In recent years, significant advances have been made in electronic or ionic conductive coordination polymers, which also results in progress in mixed ionic-electronic conductive coordination polymers. Here we start from electronic and ionic conductive CPs to mixed ionic-electronic conductive CPs. Recent advances in the design of mixed ionic-electronic conductive CPs are summarized. In addition, devices based on mixed conduction are selected.
关键词： metal-organic frameworks,coordination polymers,ionic,conductivity,electronic
更新于2025-09-23 15:19:57
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Rapid growth of large area graphene on glass from olive oil by laser irradiation
摘要： Although homogeneous, high quality graphene can be fabricated on a Cu or Ni sheet using the traditional chemical vapour deposition method at high temperatures (over 1000°C) and specific atmospheric conditions, their transfer to another substrate is difficult. In this paper a novel method of rapidly (i.e. 3–6 s of laser irradiation) producing a large area (>3 cm2) graphene film from olive oil on a glass surface (pre-coated with a 5–28 nm thick Ni film) with defocused, large area continuous laser irradiation is described. The turbostratic graphene film (6 layers) grown in such a way has shown high electrical conductivity (sheet resistance of around 20 ? sq?1) and an optical transmittance of 40–50%. With femtosecond laser patterning, 70% optical transparency was demonstrated. Continuous large area graphene was formed at relatively lower temperatures (<250°C) and without the need for specific atmospheric conditions. The basic process characteristics and mechanisms involved are discussed.
关键词： graphene,electrical conductivity,transparent,low temperature,olive oil,laser
更新于2025-09-23 15:19:57
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Epitaxial growth and electrical performance of graphene/3Ca??SiC films by laser CVD
摘要： High electrical conductivity graphene/epitaxial-3CeSiC (G/epi-3CeSiC) composite films have the potential to the applications such as micro-electro-mechanical systems, distributed Bragg reflectors, solar cells, and photocatalysis in harsh environments. In this study, G/epi-3CeSiC composite films were prepared through laser chemical vapor deposition (LCVD) using hexametyldisilane (HMDS) as a safe single precursor. The electrical conductivity (s) of the composite films reached 2.23 (cid:1) 104 S/m, which is 2.2 times of the highest s reported for G/epi-3CeSiC composite. The deposition rate (Rdep) of the composite film with the highest s is 8.2 times of that of the G/epi-3CeSiC with the highest s ever reported. s of the pure epitaxial 3CeSiC film is only 81.2 S/m, which is the lowest value reported to date of 3CeSiC prepared through CVD using HMDS as a single precursor. Elimination of carbon is beneficial for increasing the breakdown field intensity and decreasing the leakage current of heterojunction when epitaxial 3CeSiC is used as semiconductor material.
关键词： Electrical conductivity,Deposition rate,Laser CVD,Graphene/SiC film,Epitaxial
更新于2025-09-23 15:19:57
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Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells
摘要： We show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface due to the influence of hole-transport materials. For hole-transport-layer-free PSCs, high-frequency capacitance can be considered as the geometric capacitance for calculating the dielectric constant of the perovskite layer. We further show that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer.
关键词： Halide perovskite solar cells,Dielectric constant,Hole-transport layer,Capacitance-based techniques,Ionic conductivity
更新于2025-09-23 15:19:57
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Influence of 1-methyl-3-propylimidazolium iodide ionic liquid on the performance of dye-sensitized solar cell using hexanoyl chitosan/poly(vinyl chloride) based polymer electrolyte
摘要： Polymer electrolytes based on hexanoyl chitosan/poly(vinyl chloride) (PVC) were prepared by employing sodium iodide (NaI) as the doping salt and 1-methyl-3-propylimidazolium iodide (MPImI) as the ionic liquid. The concentration of MPImI was varied from 2 to 10 wt.% while the amount of polymer and salt were kept constant. The effect of MPImI on the crystallinity, structural and conductivity properties of hexanoyl chitosan/PVC-NaI have been investigated. XRD results show that MPImI disrupts the crystallinity of polymer matrix while FTIR results show the existence of interactions among components in hexanoyl chitosan/PVC-NaI-MPImI. Polymer electrolyte without MPImI shows the highest conductivity of 1.5 × 10?5 S cm?1 at 303 K. Upon incorporation of MPImI, increment in conductivity can be observed. The hexanoyl chitosan/PVC-NaI-MPImI electrolytes were assembled into dye-sensitized solar cells (DSSCs) and the dependence of DSSCs performance on MPImI concentration has been investigated. DSSC with 8 wt.% of MPImI shows the energy conversion efficiency, η of 4.55 % with short circuit current density, Jsc of 10.34 mA cm?2 and open circuit voltage, Voc of 0.74 V.
关键词： PVC,Conductivity,Polymer electrolyte,Dye-sensitized solar cells,Hexanoyl chitosan
更新于2025-09-23 15:19:57