- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Lattice thermal conduction in suspended molybdenum disulfide monolayers with defects
摘要： In this study, we investigated the effect of lattice defects comprising vacancies and boundaries on the lattice thermal conductivity (LTC), k p, of suspended molybdenum disulfide monolayers (MLs) over a wide temperature range (1 < T < 500 K). By using the phonon Boltzmann formalism, the acoustic phonons were considered to be scattered by the sample and grain boundaries, isotopic impurities, vacancies, and other phonons via Umklapp and normal (N-) processes. k p was evaluated using a modified Callaway model by considering the in-plane longitudinal acoustic and transverse acoustic phonons, and out-of-plane flexural acoustic phonon modes. We demonstrated the need to include the often neglected non-resistive N-processes when evaluating the LTC. Numerical calculations of the temperature dependence of the LTC for crystalline and polycrystalline MoS2 MLs showed the dominance of sample-dependent scattering mechanisms at low temperatures (T < 100 K) and of phonon-phonon scattering at higher temperatures, where the N-processes played an important role. The effects of vacancies and boundaries were to alter the behavior and suppress the magnitude of the LTC. The suppression due to vacancies was greater in crystalline MLs with specular surfaces and in polycrystalline MLs with larger grain sizes. The calculations compared well with recent thermal conductivity data obtained for polycrystalline samples. The need for further investigations is suggested.
关键词： MoS2 monolayer,grain boundary scattering,vacancy scattering,lattice thermal conductivity,N-process
更新于2025-09-23 15:23:52
-
Electronic mobility and crystal structures of 2,5-dimethylanilinium triiodide and tin-based organic-inorganic hybrid compounds
摘要： We synthesize single crystals of a new 2,5-dimethylanilinium tin iodide organic-inorganic hybrid compound and 2,5-dimethylanilinium triiodide. Single-crystal X-ray diffraction reveals that the hybrid grows as a unique rhombohedral structure consisting of one-dimensional chains of SnI6-octahedra that share corners and edges to build up a ribbon along the [111] direction. Notably, we find that hypophosphorous acid, H3PO2, is of central importance to the formation of this hybrid. In the absence of H3PO2, we synthesize 2,5-dimethylanilinium triiodide from the same starting compounds. We investigate the synthesis routes that drive the growth of these two compounds with distinct crystal structures, appearance and properties. Pulse-radiolysis time-resolved microwave conductivity measurements and density functional theory calculations reveal that both compounds have low charge carrier mobilities and very long lifetimes, consistent with their one-dimensional structural characteristics. Our findings give a better understanding of the relation between synthesis, crystal structures and charge carrier mobilities.
关键词： Tin iodide,Single-crystal XRD,Organic-organic hybrids,Microwave conductivity,Hypophosphorous acid,Triiodide
更新于2025-09-23 15:23:52
-
Structural, optical, electrical and thermal characteristics of La{CS(NH2)2CO(NH2)2}Cl3 : A novel hybrid complex for optoelectronic applications
摘要： A hybrid complex of lanthanum chloride with urea and thiourea is crystallized at room temperature by conventional solution method. The structural investigations by single crystal X-ray diffraction confirmed the orthorhombic system with cell dimensions a = 7.676 ?, b = 8.564 ?, c = 5.498 ?, α = β = γ = 90°. The optical studies by UV–VIS absorption spectroscopy shows the complex exhibits transmittance about 96%. The complex is characterized as the wide band gap crystals with value greater than 4 eV. The dielectric properties were studied in frequency range 10 kHz–1 MHz in temperature range 303–453 K. The ac conductivity was found to obey the universal power law and suggests the correlated barrier hoping mechanism dominating the conduction process. The thermal stability and the decomposition mechanism were confirmed by thermo gravimetric and differential thermo analytical (TG/DTA) techniques.
关键词： Dielectric analysis,ac conductivity,Hybrid complex,X-ray diffraction,UV–Vis spectrum
更新于2025-09-23 15:23:52
-
Effects of carbon nanotube thermal conductivity on optoacoustic transducer performance
摘要： CNT-PDMS composite is regarded as a promising candidate for optoacoustic transducer application. However, the relationship between the CNT thermal conductivity and optoacoustic transducer performance is still unde?ned. To explore this relationship, four types of CNTs with different diameters and lengths were employed to successfully fabricate four types of optoacoustic transducers. The thermal properties of CNTs were analyzed and discussed in this paper; the laser-generated ultrasound and optoacoustic conversion ef?ciency of the transducers were experimentally and theoretically investigated. Results of comparison revealed the CNT with a diameter and length of 8 nm and 10e30 mm, respectively, to have the highest thermal conductivity. With this type of CNT/PDMS composite, the optoacoustic conversion ef?ciency reached as high as 9.59 (cid:1) 10-3. Overall, the results demonstrate that higher CNT thermal conductivity corresponds to better optoacoustic transducer performance.
关键词： Laser-generated ultrasound,Thermal conductivity,Optoacoustic transducer,Optoacoustic conversion ef?ciency,CNT
更新于2025-09-23 15:23:52
-
Comparative research on two surface conductivity models for the scattering of electromagnetic wave by the charged sphere
摘要： The surface conductivity model plays an important role in solving the electromagnetic scattering of microwave by the charged particle. We compared two models that can be used in the scattering of electromagnetic wave by the charged spherical particle. The results show that the extinction efficiency and the scattering efficiency calculated through these two models are much different in some cases, and which also affect by the particle size, refractive index, and its charged quantity. However, when the size parameter of particle is larger enough, the results from these two models became consistent with each other.
关键词： Charged spheres,Surface conductivity,Size parameters,Mie scattering,Scattering and extinction
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE International Meeting for Future of Electron Devices, Kansai (IMFEDK) - Kyoto, Japan (2018.6.21-2018.6.22)] 2018 IEEE International Meeting for Future of Electron Devices, Kansai (IMFEDK) - Thermoelectric Conversion Devise Using Ga-Sn-O Thin Film Prepared by Mist CVD Method
摘要： We proposed a GTO thin film thermoelectric conversion devise by the mist CVD method. The thermoelectric conversion devise with the best performance had a Seebeck coefficient of -193[μV/K], a conductivity of 6.35[S/cm], and a PF of 0.0179[mW/mK2].
关键词： Ga-Sn-O,Seebeck coefficient,conductivity,mist CVD,power factor
更新于2025-09-23 15:23:52
-
Changes in the IR Spectra of Drinking Water, Melt Water from Snow, and Heavy Water Irradiated by a Nanosecond Electron Beam
摘要： The absorption spectra of drinking water, melt water from snow, and heavy water are studied during irradiation by a nanosecond electron beam. With repeated irradiation of water, a change in the absorption spectrum of the substance was observed. The analysis of water absorption spectra in the IR region shows differences between the absorption spectra of irradiated and nonirradiated water.
关键词： water conductivity,water absorption spectrum in the infrared region,nanosecond electron beam
更新于2025-09-23 15:23:52
-
Crystal growth, structural and electrical properties of (Cu1-Ag )7GeS5I superionic solid solutions
摘要： Single crystals of (Cu1-хAgx)7GeS5I solid solutions were grown by vertical zone crystallization method. XRD studies have shown that they crystallize in face-centered cubic lattice of the argyrodite structure (space group F m4 3 , Z = 4). Structural studies were performed on the basis of original structure model by means of Rietveld re?nement method. Electrical measurements were carried out in the temperature interval 300–360 K and in the range of frequencies 10 Hz–10 GHz. Temperature and frequency dependences of electrical conductivity were analyzed. In?uence of cation substitution on the electrical conductivity as well as relationship between structural and electrical properties of (Cu1-хAgx)7GeS5I solid solutions were studied.
关键词： Arrhenius law,XRD studies,Superionic conductor,Impedance spectroscopy,Electrical conductivity
更新于2025-09-23 15:23:52
-
Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties
摘要： The structure and conductivity of the new Li- and Mg-codoped bismuth niobates Bi1.5Mg1?xLixNb1.5O7?δ (0 ≤ x ≤ 0.50) with the pyrochlore structure have been investigated. The samples were synthesized by the method of organic-inorganic precursors combustion. A structural characterization was performed using 7Li nuclear magnetic resonance (NMR) spectroscopy in combination with the ?tting of X-ray di?raction patterns. The Li+ cations dynamics were studied by temperature-dependent 7Li NMR lineshape analysis. The measurements have shown that the Li+ cations are distributed in one of two possible sublattices in the structure and are not mobile up to 120 °C. According to the results of structural analysis of the Bi1.5Mg1?xLixNb1.5O7?δ (x = 0.25; 0.50) pyrochlores the lithium atoms are distributed in the bismuth sites. The electrical properties were investigated by impedance spectroscopy method in the air, oxygen and “wet” atmospheres in the 25–750 °C temperature range. The activation energy value of dc conductivity is about 1.2–1.3 eV for the all samples and corresponds to the ionic (oxygen) conductivity at T > 400 °C. Electronic (p-type) conductivity was determined at T < 360 °C. 1H MAS NMR data and the results of the comparison of the conductivity of Li- and Mg-codoped bismuth niobates in dry and “wet” atmospheres point to the proton conductivity up to 500 °C. The dielectric permittivity ε′ values increase with lithium content from 86 (x = 0) to 143 (x = 0.5) at the same dielectric loss tanδ = 0.002 (1 MHz, 25 °C), TCC values vary from ?590 to ?530 ppm/°C in the 25–280 °C temperature range.
关键词： Conductivity,Dielectric properties,Pyrochlore,Dopant distribution,NMR spectroscopy,Bismuth niobate
更新于2025-09-23 15:23:52
-
Amorphous silicon and silicates-stabilized ZrO2 hollow fiber with low thermal conductivity and high phase stability derived from a cogon template
摘要： ZrO2 ?bers are used as refractory materials owing to their excellent thermal resistance and thermal stability. Natural cogon ?ber is a type of hollow Gramineae ?ber, and usually contains a small amount of amorphous silicon and silicates, such as SiO2, MgSiO3, CaSiO4, and Al2SiO5, which can e?ectively avoid the phase transition of ZrO2. In this study, hollow ZrO2 ?bers with remarkable thermal insulation and phase stability were synthesized using a cogon ?ber template. The results showed that the ?nal ZrO2 ?bers successfully inherited the hollow structure and amorphous substance from the cogon template. The hollow structure of the biomorphic ZrO2 ?ber helped prevent heat ?ow more e?ciently compared to solid ?bers and reduced the thermal conductivity to a signi?cant extent. In addition, the amorphous silicon and silicates played an important role in the phase stability of tetragonal ZrO2; the transformation from the tetragonal to monoclinic phase was avoided at room temperature and in humid environment.
关键词： Thermal conductivity,Amorphous silicon and silicates,Cogon ?bers,Phase stability,ZrO2 hollow ?bers
更新于2025-09-23 15:23:52