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Electrical and Mechanical Properties of CeO2-Based Thin-Film Coatings Obtained by Electrophoretic Deposition
摘要： Nanometer Ce0.8(Sm0.75Sr0.20Ba0.05)0.2O2 – δ powder with mean nanoparticle size of 15 nm has been obtained by laser evaporation of a solid-phase target followed by condensation. The nanopowder has been used to prepare suspensions for electrophoretic deposition in a mixed isopropanol : acetyl acetone = 50 : 50 vol % disperse medium offering the unique property of self-stabilization. Optimal conditions for electrophoretic deposition have been found, and uniform thin-film electrolytic coatings have been formed on a La2NiO4 cathodic carrier substrate (12–15% porosity). It has been shown that the resulting electrolyte offers a high adhesivity and has, after sintering at 1400°C, a compact granular structure with grains from 1 to 8 μ m in size. The conductivity of the 2-μ m-thick electrolyte equals 0.1 S/cm at 650°C.
关键词： solid oxide fuel cells,nanopowder,electrophoretic deposition,conductivity,CeO2-based thin-film coatings
更新于2025-09-09 09:28:46
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Effect of lack of oxygen on optical and electrical properties of RF magnetron sputtering deposited CuFeO2?x thin films
摘要： Delafossite CuFeO2?x thin ?lms were fabricated on quartz substrate using radio-frequency sputtering deposition under low O2 ?ow ratios from 9% to 0% at room temperature. The as-deposited ?lms were in amorphous phase and crystallized into rhombohedral 3R (R3m) delafossite structure after post annealing at 900?C for 2 h in ?owing N2 atmosphere. SEM images showed that the ?lms were composed of nano-sized crystallized grains, thin ?lm composed of smoother surface and higher oxygen content was obtained under higher oxygen percentage in sputtering gas. The optical transmission spectra of these ?lms were studied in the wavelength range 200–1500 nm and the results revealed a narrowing trend of direct bandgap from 3.09 eV to 2.98 eV with the decrease of oxygen ?ow ratio during deposition. All of the post-annealed CuFeO2?x thin ?lms exhibited p-type conductivity and linear ohmic contact feature with Cu electrodes. The carrier concentration of thin ?lms increased from 2.8 × 1017 cm?3 to 9.2 × 1019 cm?3 whereas the carrier mobility decreased from 9.74 cm2 ·V?1 ·s?1 to 0.035 cm2 ·V?1 ·s?1 as the oxygen ?ow ratio reduced from 9% to 0%. The ability of controlling compound com- position enables tuning of carrier concentration and mobility in CuFeO2?x and o?ering essential technical basis in engineering photoelectronic devices.
关键词： CuFeO2?x,p-type conductivity,optoelectronic properties
更新于2025-09-09 09:28:46
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Free-Space Materials Characterization by Reflection and Transmission Measurements using Frequency-by-Frequency and Multi-Frequency Algorithms
摘要： The knowledge of the electromagnetic constitutive properties of materials is crucial in many applications. Free-space methods are widely used for this purpose, despite their inherent practical difficulties. This paper describes an affordable free-space experimental setup for the characterization of flat samples in 1–6 GHz in a non-anechoic environment. The extracted properties are obtained from the calibrated Scattering Parameters, using a frequency-by-frequency solution or a multi-frequency reconstruction. For the first, we describe how the Time-Domain Gating can be implemented and used for filtering the signals. For the latter, a weighting factor is introduced to balance the reflection and transmission data, allowing one to have a more favorable configuration. The different role of transmission and reflection measurements on the achievable results is analyzed with regard to experimental uncertainties and different noise scenarios. Results from the two strategies are analyzed and compared. Good agreement between simulation, measurement and literature is obtained. According to the reported results for dielectric materials, there is no need of filtering the data by a Time-Domain Gating in case of the multi-frequency approach. Experimental results for Polymethylmethacrylate (PMMA) and Polytetrafluorethylene (PTFE) samples validate both the setup and the processing.
关键词： free-space method,permeability,conductivity,non-destructive testing,extraction algorithms,permittivity,time-domain gating,free-space calibration,scattering parameters,material characterization
更新于2025-09-09 09:28:46
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Enhanced thermal conductivity of MoS2/InSe-nanoparticles/MoS2 hybrid sandwich structure
摘要： MoS2 based hybrid structures have much attention due to their novel structures and potential applications in diverse areas, such as solar energy conversion, thermoelectric power generation and photo-transistors. In the present work, we have fabricated a novel sandwich structure of MoS2/InSe-nano-particles (NPs)/MoS2 layers on SiO2/Si substrate by a combination of chemical vapor deposition and physical vapor deposition methods. The morphology of these structures was also studied using scanning electron microscopy. In addition, we have also explored the thermal properties of these hybrid sandwich structures using temperature and power-dependent Raman spectroscopy. For MoS2/InSe-NPs/MoS2 sample, the first-order temperature coefficients of E1 2g and A1g modes were found to be (cid:1)0.01722 (cid:1)1/K, respectively, which are significantly large compared to MoS2 layers without InSe- and (cid:1)0.01575 cm NPs (i.e. MoS2/MoS2 sample). Further, the thermal conductivity of MoS2/InSe-NPs/MoS2 and MoS2/MoS2 samples on SiO2/Si substrate was extracted as ~102.3 and ~81.7 W/m-K, respectively. This work suggests an effective way to form a novel 2D-MoS2 based sandwich structure with semiconductor/metal-NPs; opening up a new scenario to understand the electronic structure of the hybrid structure, and the local strain introduced by NPs. Electron-phonon interactions at an interface can have significant effects on electrical/thermal transport through the optoelectronic devices.
关键词： Hybrid sandwich structure,Thermal conductivity,Raman spectroscopy,Tensile-strain
更新于2025-09-09 09:28:46
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Structural, Infrared, Magnetic, and Electrical Properties of Ni0.6Cd0.2Cu0.2Fe2O4 Ferrites Synthesized Using Sol-Gel Method Under Different Sintering Temperatures
摘要： Ni0.6Cd0.2Cu0.2Fe2O4 ferrites were synthesized using sol-gel method under different sintering temperatures. XRD patterns with the Rietveld refinement indicate that samples crystallize in the cubic spinel structure. The increase of sintering temperature leads successively to the increase of lattice constant, average crystallite size, intensities of absorption bands, magnetization, and electrical conductivity of the prepared ferrites. Dielectric constants decrease with frequency and their behaviors have been investigated using the interfacial polarization theory predicted by Maxwell. The modulus analysis shows the presence of electrical relaxation phenomenon and non-Debye nature for the samples. An appropriate electrical equivalent circuit was used to analyze the Nyquist plots, and the results show that the conduction mechanism of the synthesized ferrites is mainly due to the grain boundary contribution.
关键词： Ferrites,conductivity,Rietveld refinement,Sol-gel method,Infrared properties,Dielectric properties
更新于2025-09-09 09:28:46
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Thermal conductivity of TiO<sub>2</sub> nanotube: A molecular dynamics study
摘要： The thermal conductivity of anatase TiO2 nanotubes was investigated using equilibrium molecular dynamics simulations based on Green-Kubo formalism. The calculated thermal conductivity of ~8.16 W/K ? m for anatase crystal at room temperature agrees well with experimental value of ~8.5 W/K?m, demonstrating that the method used in our calculation can provide a good description for the thermal transport of TiO2. The dependence of the thermal conductivity of TiO2 nanotubes with temperature, tube size and chirality were studied in detail. The relationship between the thermal conductivity and the vibrational density-of-states of the nanotubes was also investigated.
关键词： Molecular dynamics simulations,Thermal conductivity,Nanotube structure
更新于2025-09-09 09:28:46
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Electrical Conductivity Modulation of Crosslinked Composite Nanofibers Based on PEO and PEDOT:PSS
摘要： The aim of this work is to investigate the development of nano?ber mats, based on intrinsically conductive polymers (ICPs), which show simultaneously a high electrical conductivity and mandatory insoluble water properties. In particular, the nano?bers, thanks to their properties such as high surface area, porosity, and their ability to o?er a preferential pathway for electron ?ow, play a crucial role to improve the essential characteristics ensured by ICPs. The nano?ber mats are obtained by electrospinning process, starting from a polymeric solution made of polyethylene oxide (PEO) and poly(styrene sulfonate) (PEDOT:PSS). PEO is selected not only as a dopant to increase the electrical/ionic conductivity, as deeply reported in the literature, but also to ensure the proper stability of the polymeric jet, to collect a dried nano?ber mat. Moreover, in the present work, two di?erent treatments are proposed in order to induce crosslinking between PEO chains and PEDOT:PSS, made insoluble into water which is the ?nal sample. The ?rst process is based on a heating treatment, conducted at 130°C under nitrogen atmosphere for 6 h, named the annealing treatment. The second treatment is provided by UV irradiation that is e?ective to induce a ?nal crosslinking, when a photoinitiator, such as benzophenone, is added. Furthermore, we demonstrate that both crosslinking treatments can be used to verify the preservation of nanostructures and their good electrical conductivity after water treatment (i.e., water resistance). In particular, we con?rm that the crosslinking method with UV irradiation results to being more e?ective than the standard annealing treatment. Indeed, we demonstrate that the processing time, required to obtain the ?nal crosslinked nano?ber mats with a high electrical conductance, results to being smaller than the one needed during the heating treatment.
关键词： PEO,PEDOT:PSS,intrinsically conductive polymers,electrical conductivity,nano?ber mats,water resistance,electrospinning,crosslinking
更新于2025-09-09 09:28:46
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Branched Side Chains Govern Counterion Position and Doping Mechanism in Conjugated Polythiophenes
摘要： Predicting the interactions between a semi-conducting polymer and dopant is not straightforward due to the intrinsic structural and energetic disorder in polymeric systems. Although the driving force for e?cient charge transfer depends on a favorable o?set between the electron donor and acceptor, we demonstrate that the e?cacy of doping also relies on structural constraints of incorporating a dopant molecule into the semiconducting polymer ?lm. Here, we report the evolution in spectroscopic and electrical properties of a model conjugated polymer upon exposure to two dopant types: one that directly oxidizes the polymeric backbone and one that protonates the polymer backbone. Through vapor phase in?ltration, the common charge transfer dopant, F4-TCNQ, forms a charge transfer complex (CTC) with the polymer poly(3-(2′-ethyl)hexylthiophene) (P3EHT), a conjugated polymer with the same backbone as the well-characterized polymer P3HT, resulting in a maximum electrical conductivity of 3 × 10?5 S cm?1. We postulate that the branched side chains of P3EHT force F4-TCNQ to reside between the π-faces of the crystallites, resulting in partial charge transfer between the donor and the acceptor. Conversely, protonation of the polymeric backbone using the strong acid, HTFSI, increases the electrical conductivity of P3EHT to a maximum of 4 × 10?3 S cm?1, 2 orders of magnitude higher than when a charge transfer dopant is used. The ability for the backbone of P3EHT to be protonated by an acid dopant, but not oxidized directly by F4-TCNQ, suggests that steric hindrance plays a signi?cant role in the degree of charge transfer between dopant and polymer, even when the driving force for charge transfer is su?cient.
关键词： semiconducting polymer,electrical conductivity,steric hindrance,dopant,charge transfer
更新于2025-09-09 09:28:46
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Preparation of High Performance Conductive Polyaniline Magnetite (PANI/Fe3O4) Nanocomposites by Sol-Gel Method
摘要： The conductivities of polyaniline magnetite (PANI/Fe3O4) nanocomposites prepared by sol-gel method were measured by standard van der Pauw DC 4-point probe method. PANI/Fe3O4 conductivity was measured as a function of wt % (5, 10, 15, 20 and 25 wt %) of Fe3O4 nanoparticles. It was observed that the conductivity of polyaniline containing certain percentage of Fe3O4 nanoparticles is slightly lower than the bulk PANI nanotubes and drastically decreases with increase of wt % Fe3O4 nanoparticles. The high conductivities of PANI/Fe3O4 nanocomposites was observed due to high concentration of dopant (oxidants) used in the polymerization process and the optimization of these composites allows this being use as a parameter for the production of nanofibers. Fourier transform infrared spectra, field emission scanning electron microscope, X-ray diffraction and ultraviolet-visible absorption spectra are used to characterize the phase structure, morphologies and functional group of the PANI/Fe3O4 composites samples. Fourier transform infrared analysis indicates the presence of PANI containing Fe3O4 nanoparticles and the field emission scanning electron microscope (FESEM) results has proven that the formation of nanofibers in the PANI/Fe3O4 nanocomposites. The crystalline phase of PANI/Fe3O4 nanocomposites studied by X-ray diffraction indicated that the Fe3O4 nanoparticles was present in the PANI matrices.
关键词： Polyaniline,Fe3O4 nanoparticles,FESEM,Conductivity,Composites
更新于2025-09-09 09:28:46
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Strain engineering for thermal conductivity of diamond nanothread forests
摘要： Thermal properties of the diamond nanothread (DNT) forest array are studied using non-equilibrium molecular dynamics simulations. We find a strong anisotropic thermal property in this structure, i.e. the thermal conductivity in thread direction is over 300 times of that in the perpendicular direction. When subject to external strain, the thermal conductivity of the DNT forest decreases with increasing compressive/tensile strain in the thread direction, while thermal conductivity increases exponentially with increasing compressive strain in the perpendicular direction. The increase in thermal conductivity is attributed to the enhanced interactions among DNTs induced by compression. These results are explained by phonon spectra and structural deformation. Our findings show that diamond nanothread forest has a great potential application in the super-capacitors.
关键词： Anisotropy,Diamond nanothread,Thermal conductivity,Molecular dynamics
更新于2025-09-09 09:28:46