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Temperature and pressure induced Raman studies of C 60 oxide
摘要： We present temperature, laser power, and pressure dependent Raman spectral analysis of C60 oxide (C60O) thin films prepared by the photolysis method. The first order temperature, laser power, and pressure coefficients of the Raman frequencies are evaluated and are utilized for evaluating the thermal conductivity of C60O. Its thermal conductivity is found to be 0.7 W m-1 K-1 which is marginally higher than that of bulk C60. Raman frequencies corresponding to C–O and C–C bonds blue-shift with a decrease in temperature which is attributed to the thermal contraction of C60O molecules. The density functional measurements have been performed to optimize C60O structure. The contraction in the C–O bond length has been corroborated with the experimental Raman shifts at different temperatures and is used to evaluate the linear expansion coefficient of C60O. Pressure induced compression and polymerization of C60O clusters are also illustrated. This study highlights the interplay between thermal and mechanical transformations in the C60O cluster which may regulate its thermoelectric properties by tuning the intermolecular interactions.
关键词： pressure dependence,thermoelectric properties,Raman spectroscopy,thermal conductivity,C60 oxide,laser power dependence,temperature dependence
更新于2025-09-09 09:28:46
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-derived materials
摘要： Symmetry and dimensionality are essential factors defining lattice dynamics and conductivity (κ). Here, we critically examine these via ab initio Boltzmann transport applied to single chain and bulk electride Ba3N and Ba3NX (X = Sb,Bi). Chiral phonons in one-dimensional chains obey new symmetry-based scattering rules that limit thermal resistance. Weak chain coupling breaks these in the bulk, giving lower κ and large κ anisotropy. Curiously, intercalation of large X atoms binds chains more strongly, reducing the volume, yet gives lower κ and transforms the electronic behavior. Insights developed here can be more generally applied to other materials and provide avenues for predictive materials design.
关键词： symmetry,lattice dynamics,Ba3NX,dimensionality,thermal conductivity,Ba3N,chiral phonons,electride
更新于2025-09-09 09:28:46
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Lattice Thermal Conductivity Calculation of Sb2Te3 using Molecular Dynamics Simulations
摘要： We study lattice thermal conductivity of Sb2Te3 using molecular dynamics simulations. The interatomic potentials are fitted to reproduce total energy and elastic constants, and phonon properties calculated using the potentials are in reasonable agreement with first-principles calculations and experimental data. Our calculated lattice thermal conductivities of Sb2Te3 decrease with temperature from 150 K to 500 K. The in-plane lattice thermal conductivity of Sb2Te3 is higher than cross-plane lattice thermal conductivity of Sb2Te3, as in the case of Bi2Te3, which is consistent with the anisotropy of the elastic constants.
关键词： Thermal conductivity,Interatomic potential,Molecular dynamics,Sb2Te3
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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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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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
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Thermal conductivity of silicon nanomaterials measured using the photoacoustic technique in a piezoelectric configuration
摘要： In this study, we investigated the thermal transport in porous silicon nanostructures and silicon nanowires fabricated by electrochemical and metal-assisted chemical etching processes, respectively. In particular, the thermal conductivity values for the silicon-based nanomaterials were estimated based on photoacoustic measurements obtained from piezoelectric recordings. The amplitude–frequency and phase–frequency dependencies of the photoacoustic responses of the nanostructured silicon samples were obtained, and simulated successfully with a theoretical model. Correlations were established between the thermal conductivities and etching parameters.
关键词： Silicon nanomaterial,Piezoelectric recording,Thermal conductivity,Photoacoustic technique
更新于2025-09-09 09:28:46
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Direct probing of cross-plane thermal properties of ALD Al <sub/>2</sub> O <sub/>3</sub> /ZnO superlattice films with improved figure of merit and their cross-plane thermoelectric generating performance
摘要： There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, has not been performed from these semiconducting superlattice films, because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present technique using a structure of sandwiched superlattice films between two embedded heaters as heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al2O3/ZnO superlattice films, prepared by atomic layer deposition (ALD) method. Used in combination with the promising cross-plane four-point-probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al2O3/ZnO superlattice films in the temperature range from 80 to 500 K. Our experimental methodology and the obtaining results represent a significant advancement in the understating of phonon and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.
关键词： Thermal conductivity,Cross-plane thermoelectric properties,Seebeck coefficient,Phonon transport,Superlattice films,3-omega measurement,Phonon scattering
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Preparation and Characterization of Epoxy and Hollow Ceramic Spheres Composites
摘要： High crash strength and high thermal conductivity hollow ceramic sphere with external diameters between 250 and 420 micrometers were produced by firing green bodies prepared in a fluidized reactor at room temperature. Then these spheres were bonded together by epoxy resin to produce composites with very high filler concentration but light weight. The dielectric, thermal and mechanical properties of the composites were investigated. Because the component in the raw materials of hollow ceramic spheres is varied, the corresponding composites have tunable permittivity and dielectric loss. In the composites, hollow ceramic spheres are nearly close packed, which can be observed by optical microscope. The novel close packed structure of these spheres endows the composites with highly efficient pathways for heat dissipation and reliable framework of bearing compressive loading. The surfaces of the spheres were modified by 1wt. % silane coupling agent, KH-560, before combining with epoxy resin in order to improve their chemical compatibility with epoxy resin. With TGA results, we can see that the epoxy resin in the composites has a low percentage of mass ratios and thus plays a role as binder to combine neighboring hollow ceramic spheres together. The results demonstrate improvement of dielectric and thermal conducting properties of epoxy resin, and feasibility of extending its working ranges in both compression strength and temperature as a multifunctional material in insulating area.
关键词： Compressive strength,Thermal conductivity,Composites,Ceramic spheres
更新于2025-09-09 09:28:46
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Thermal and electrical conductivity enhancement of solar glycol-water mixture containing MWCNTs
摘要： In this investigation, the authors describe the thermal conductivity, and electrical conductivity of solar glycol - water (50:50) mixture with MWCNTs. Gum Arabic was used as the surfactant to prepare a stable nanofluid suspension. The MWCNTs are dispersing with different volume concentrations of 0.2%, 0.4% and 0.6% prepared via a typical two-step methodology. The colloidal stability assessments were conducted through UV-vis spectrometer, zeta potential analyser, scanning electron microscopy analysis and pH metre. The maximum augmentation of thermal conductivity attained is (cid:1)21.46% at a loading of 0.6 vol.% of MWCNTs in SG - water mixture at 50(cid:3)C. However, the electrical conductivity of the prepared nanofluid linearly enhanced with increasing temperature. The electrical conductivity enhancements of (cid:1)62.19% at a loading of 0.6 vol.% of MWCNTs in SG – water mixture at 50?C. Results confirm that the SG-Water and MWCNTs based nanofluids can be used as a right replacement for the conventional liquids in various heat transfer applications.
关键词： Solar glycol,Thermal conductivity,Multiwalled carbon nanotubes,pH,Electrical conductivity
更新于2025-09-04 15:30:14