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Design of Thermophysical Properties Test System by Laser Point Heat Source Method
摘要： Laser is widely used in material thermophysical properties testing because of its good test accuracy and test efficiency. However, due to the high market price of laser flash devices, their promotion space is limited. Based on the unsteady heat transfer model of a laser point heat source, the enantiomorphous heat source theory was introduced to modify the influence of an adiabatic boundary on the temperature rise of a measuring point. The thermal conductivity and thermal diffusivity of isotropic materials were calculated by numerical analysis combined with computer programming. A thermophysical property test system was developed, and the thermophysical properties of blast furnace firebrick, marble, and diatomite brick were studied. The results showed that the maximum repeatable accuracy error was 4.75%, and the maximum relative deviation from the reference value was 2.04%. The effective test range of the device was that the thermal conductivity was less than 3 W∕(m ? K). Compared with the laser flash method, the device does not require high test-time accuracy and data collection instantaneity in terms of test principles. Therefore, the device can use a general-level laser generator, temperature sensor, timer, data collector, and so on, and the hardware cost is greatly reduced.
关键词： thermophysical properties,thermal diffusivity,test system,thermal conductivity,laser point heat source
更新于2025-09-23 15:19:57
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The Conductivity of the Monolayer of DNA a?? Quantum Dot Complexes in the Presence of Intercalating Charged Ligands
摘要： The resistance of a monolayer of complexes of the double-stranded DNA with quantum dots were computed. It was shown that with the non-competitive DNA hybridization and in the presence of monovalent positively charged ligands in the solution, a decrease in resistance occurs as compared to that for uncharged ligands. It is shown that the charged ligands enhance the sensitivity of the DNA chips as compared to the uncharged ones.
关键词： DNA,biosensor,intercalator,conductivity
更新于2025-09-23 15:19:57
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Multi-time scale coordinated scheduling for the combined system of wind power, photovoltaic, thermal generator, hydro pumped storage and batteries
摘要： The phenomenon of soil salinization in semi-arid regions is getting amplified and accentuated by both anthropogenic practices and climate change. Land salinization mapping and monitoring using conventional strategies are insufficient and difficult. Our work aims to study the potential of synthetic aperture radar (SAR) for mapping and monitoring of the spatio-temporal dynamics of soil salinity using interferometry. Our contribution in this paper consists of a statistical relationship that we establish between field salinity measurement and InSAR coherence based on an empirical analysis. For experimental validation, two sites were selected: 1) the region of Mahdia (central Tunisia) and 2) the plain of Tadla (central Morocco). Both sites underwent three ground campaigns simultaneously with three Radarsat-2 SAR image acquisitions. The results show that it is possible to estimate the temporal change in soil electrical conductivity (EC) from SAR images through the InSAR technique. It has been shown that the radar signal is more sensitive to soil salinity in HH polarization using a small incidence angle. However, for the HV polarization, a large angle of incidence is more suitable. This is, under considering the minimal influence of roughness and moisture surfaces, for a given InSAR coherence.
关键词： interferometric synthetic aperture radar (InSAR) coherence,polarimetric synthetic aperture radar (SAR),soil salinity,Electrical conductivity (EC)
更新于2025-09-23 15:19:57
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Laser-engineered heavy hydrocarbons: Old materials with new opportunities
摘要： Polycyclic heavy hydrocarbons (HHs) such as coal, tar, and pitch are a family of materials with extremely rich and complex chemistry, representing a massive opportunity for their use in a range of potential applications. The present work shows that optimal selection of initial HHs based on molecular constituents is essential in tuning the material for a particular and targeted electronic application. Combining the selection of feedstock chemistry (H:C and aromatic content) and controlling variable laser treatment parameters (laser power, speed, and focus) lead to full control over the H:C ratio, sp2 concentration, and degree of graphitic stacking order of the products. The broad intertunability of these factors results from a wide distribution of carbon material crystallinity from amorphous to highly graphitic and a broad distribution of electrical conductivity up to 103 S/m.
关键词： heavy hydrocarbons,graphitization,conductivity,electronic applications,laser ablation
更新于2025-09-23 15:19:57
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Spectroscopic and Electrical Properties of Ag2S/PVA Nanocomposite Films for Visible-Light Optoelectronic Devices
摘要： Polymer nanocomposites are potential materials in the industrial sector and in our daily life due to their diverse properties and applications. Throughout the present study, solution casting technique has been used to prepare polyvinyl alcohol (PVA) filled with different weight (wt.) ratios percentages (%) (0, 0.01, 0.1, 1.0 and 10.0 wt%) of silver sulfide nanoparticles (Ag2S NPs). The concentration dependence of spectroscopic and electrical behaviors based on PVA polymer dispersed with Ag2S has been investigated. The prepared films with the variation of loading filler concentrations from 0 to 10 wt% have been characterized by different spectroscopic techniques. Fourier transform infrared (FTIR) analysis confirmed the successful incorporation of Ag2S nanoparticles in the PVA matrix by studying the changes of the characterizing bands which reveal the interaction within the composite structure. Whilst photoluminescence (PL) spectra of the Ag2S/PVA nanocomposite films showed an interesting peak covering the entire range of interest for visible light optoelectronic devices at a very low concentration of the loading filler of Ag2S. The electrical properties of the plain and Ag2S NPs doped PVA nanocomposites have been studied using DC electrical conductivity (σDC) measurements performed over a temperature (T) range from 298 to 373 K. The study demonstrates the increase of the DC electrical conductivity with increasing filler content of Ag2S by three orders of magnitude. DC conductivity also showed temperature dependent behavior where the conductivity enhanced by five orders of magnitude when temperature increased up to 373 K. These novel results present Ag2S/PVA nanocomposites as a promising material in optoelectronics applications.
关键词： DC conductivity,FTIR spectroscopy,Ag2S,PVA nanocomposites,Photoluminescence,Optoelectronic devices
更新于2025-09-23 15:19:57
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Strongly Enhanced Berry Dipole at Topological Phase Transitions in BiTeI
摘要： Transitions between topologically distinct electronic states have been predicted in different classes of materials and observed in some. A major goal is the identification of measurable properties that directly expose the topological nature of such transitions. Here, we focus on the giant Rashba material bismuth tellurium iodine which exhibits a pressure-driven phase transition between topological and trivial insulators in three dimensions. We demonstrate that this transition, which proceeds through an intermediate Weyl semimetallic state, is accompanied by a giant enhancement of the Berry curvature dipole which can be probed in transport and optoelectronic experiments. From first-principles calculations, we show that the Berry dipole—a vector along the polar axis of this material—has opposite orientations in the trivial and topological insulating phases and peaks at the insulator-to-Weyl critical points, at which the nonlinear Hall conductivity can increase by over 2 orders of magnitude.
关键词： Berry curvature dipole,Weyl semimetallic state,BiTeI,nonlinear Hall conductivity,topological phase transitions
更新于2025-09-23 15:19:57
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Remarkable Oxygen-Evolution Activity of Ca2-xSrxFe2O6-δ
摘要： The unprecedented catalytic activity of an iron-based oxygen-deficient perovskite for oxygen-evolution reaction (OER) is reported, given the need for catalysts based on earth-abundant elements. In addition, systematic trends in oxygen-evolution activity as a function of composition, defect-order and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca2Fe2O6-δ < CaSrFe2O6-δ < Sr2Fe2O6-δ. The latter material, which has the highest electrical conductivity and a unique type of defect-order, exhibits the best OER activity. In conventional experiments using glassy carbon electrode, this compound shows superior OER activity compared to the current state of the art catalysts, Ba0.5Sr0.5Co0.8Fe0.2O3?δ and RuO2. It also offers an additional advantage, namely high intrinsic electrical conductivity, which allows Sr2Fe2O6-δ to act as a catalyst without the need for glassy carbon electrode or carbon powder, that are frequently used for enhancing the charge transport in OER catalysts. Indeed, pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.
关键词： oxygen-evolution reaction,perovskite phases,iron,defect-order,electrical conductivity
更新于2025-09-23 15:19:57
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On the Theoretical and Experimental Control of Defect Chemistry, Electrical and Photoelectrochemical Properties of Hematite Nanostructures
摘要： Hematite (α-Fe2O3) is regarded as one of the most promising cost-effective and stable anode materials in photoelectrochemical applications, and its performance, like other transition metal oxides, depends strongly on its electrical and defect properties. In this work, the electrical and thermo-mechanical properties of undoped and Sn-doped α-Fe2O3 nanoscale powders were characterized in-situ under controlled temperatures (T = 250 to 400oC) and atmospheres (pO2 = 10-4 to 1 atm O2) to investigate their transport and defect properties. Frequency-dependent complex impedance spectra show that interfacial resistance between particles is negligible in comparison with particle resistance. Detailed defect models predicting the dependence of electron, hole, iron and oxygen vacancy concentrations on temperature and oxygen partial pressures for undoped and doped α-Fe2O3 were derived. Using these defect equilibria models, the operative defect regimes were established and the bandgap energy of undoped α-Fe2O3 and oxidation enthalpy of Sn-doped α-Fe2O3 were obtained from the analysis of the temperature and pO2 dependence of the electrical conductivity. Based on these results, we are able to explain the surprisingly weak impact of donor doping on the electrical conductivity of α-Fe2O3. Furthermore, experimental means based on the results of this study are given for successfully tuning hematite to enhance its photocatalytic activity for the water oxidation reaction.
关键词： dilatometry,α-Fe2O3,defect chemistry,photoelectrochemistry,electrical conductivity
更新于2025-09-23 15:19:57
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Mercaptopropyltriethoxysilane (MPTES) Concentration Effect on Selectivity and Electrical Response of Nanostructure
摘要： The surface modification by on Mercaptopropyltriethoxysilane (MPTES) done to enhance electrical behavior of nano-IDE -based sensor, silicon based active area was coated with MPTES. The electrical properties of modified nano-IDE were tested using impedance analyser by observing the changes in impedance with the frequencies There was increase as the concentration of the MPTES increase from 1 to 5%. The electrical conductivity increases as mobility increase with the surface attenuation by the MPTES. This increase in concertation observed increase of the electrical conductivity with carrier mobility increment, this indicate decrease of the Si–arsenic bond length, which caused the bandgap to be shortened, likewise, The device behaviour to surface modification was capacitive reactive in natured.
关键词： impedance analyser,nano-IDE,electrical conductivity,Mercaptopropyltriethoxysilane (MPTES),surface modification
更新于2025-09-23 15:19:57
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Theoretical and experimental studies on DC conductivity and temperature-dependent AC conductivity of poly(butyl methacrylate)/Nd-TiO <sub/>2</sub> nanocomposites
摘要： Electrically conductive nanocomposite system based on poly(butyl methacrylate) (PBMA) with different contents of neodymium-doped titanium dioxide (Nd-TiO2) was prepared by in situ free radical polymerization method. The effect of Nd-TiO2 on the morphology and structural properties of the composites was carried out by scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). The temperature-dependent AC conductivity and DC electrical conductivity of PBMA/Nd-TiO2 nanocomposites were studied with respect to the different volume fraction of Nd-TiO2 nanoparticles. SEM and XRD patterns revealed the uniform dispersion and structural regularity of nanoparticles in the polymer matrix. The AC conductivity of PBMA and its composites were found to be increased with an increase in temperatures and frequencies. The activation energy and exponential factor were analyzed from AC conductivity and both results indicate the hopping conduction mechanism present in PBMA/Nd-TiO2 nanocomposite, which is responsible for the variation of conductivity with temperature also. The DC conductivity of nanocomposites was higher than pure PBMA and the conductivity increases with increase in the concentration of Nd-TiO2 nanoparticles. Experimental and theoretical investigations based on McCullough, Bueche, Scarisbrick, and Mamunya modeling were carried out to observe the DC conductivity differences induced by the addition of Nd-TiO2 nanoparticles in PBMA matrix. Among the various modeling studied here, Mamunya model shows better agreement with the experimental conductivity.
关键词： Poly(n-butyl methacrylate),DC conductivity,conductivity modeling,temperature-dependent AC conductivity
更新于2025-09-19 17:15:36