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The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) foam has become a potential soft robotic gripper-based material that can provide a better grasping force and handling objects due to its ability in varying stiffness in correspond to applied magnetic fields. However, MR foams are facing degradation issue that may reduce the storage modulus when often exposed to thermal exposure from the operating system of a device. Therefore, this study focuses on improving the storage modulus and simultaneously enhancing the thermal properties of MR foam. Hence, silica nanoparticles were introduced as an additive to achieve the improvement target. MR foams were embedded with different concentrations of silica nanoparticles from 0 to 5 wt.%, and the corresponding rheological properties was examined under different temperature conditions from 25 °C to 65 °C. The results revealed that increasing temperatures have reduced the storage modulus of MR foams, however, the embedded silica has countered the drawbacks by strengthening the interfacial interactions between CIP-polyurethane foam matrix. In addition, the morphological characteristics of MR foams also showed less debris or peel-off PU foam with silica nanoparticles. Besides, the silica nanoparticles have delayed the thermal degradation of MR foam for approximately 30 °C. [ABSTRACT FROM AUTHOR]

Platinum-carbon (PtC) composite nanowires were fabricated using focused electron beam induced deposition and postprocessed, and their performance as a nanoscale resistive thermal device (RTD) was evaluated. Nanowires were free-standing and deposited on a dedicated substrate to eliminate the influence of the substrate itself and of the halo effect on the results. The PtC free-standing nanowires were postprocessed to lower their electrical resistance using electron beam irradiation and thermal annealing using Joule heat both separately and combined. Postprocessed PtC free-standing nanowires were characterized to evaluate their noise figure (NF) and thermal coefficients at the temperature range from 30 K to 80 °C. The thermal sensitivity of RTD was lowered with the reduced resistance but simultaneously the NF improved, especially with electron-beam irradiation. The temperature measurement resolution achievable with the PtC free-standing nanowires was 0.1 K in 1 kHz bandwidth. [ABSTRACT FROM AUTHOR]

Melt treatment is well known to have an important influence on the properties of metallic glasses (MGs). However, for the MGs quenched from different melt temperatures with a quartz tube, the underlying physical origin responsible for the variation of properties remains poorly understood. In the present work, we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins. Specifically, we quenched the melt at different temperatures ranging from 1.1 T l to 1.5 T l (T l is the liquidus temperature) to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating. We found that glass transition temperature, T g, increases by as much as 36 K, and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5 T l. The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys. The incorporated oxygen and silicon can both enhance the interactions between atoms, which renders the cooperative rearrangements of atoms difficult, and thus enhances the kinetic stability of the MGs. [ABSTRACT FROM AUTHOR]

Objective. Thermal property (TP) maps of human tissues are useful for tumor treatment and diagnosis. In particular, the blood perfusion rate is significantly different for tumors and healthy tissues. Noninvasive techniques that reconstruct TPs from the temperature measured via magnetic resonance imaging (MRI) by solving an inverse bioheat transfer problem have been developed. A few conventional methods can reconstruct spatially varying TP distributions, but they have several limitations. First, most methods require the numerical Laplacian computation of the temperature, and hence they are sensitive to noise. In addition, some methods require the division of a region of interest (ROI) into sub-regions with homogeneous TPs using prior anatomical information, and they assume an unmeasurable initial temperature distribution. We propose a novel robust reconstruction method without the division of an ROI or the assumption of an initial temperature distribution. Approach. The proposed method estimates blood perfusion rate maps from relative temperature changes. This method avoids the computation of the Laplacian by using integral representations of the Helmholtz decomposition of the heat flux. Main Result. We compare the reconstruction results of the conventional and proposed methods using numerical simulations. The results indicate the robustness of the proposed method. Significance. This study suggests the feasibility of thermal property mapping with MRI using the robust proposed method. [ABSTRACT FROM AUTHOR]

Conventional techniques of measuring thermal transport properties may be unreliable or unwieldy when applied to nanostructures. However, a simple, all-electrical technique is available for all samples featuring high-aspect-ratio: the 3 ω method. Nonetheless, its usual formulation relies on simple analytical results which may break down in real experimental conditions. In this work we clarify these limits and quantify them via adimensional numbers and present a more accurate, numerical solution to the 3 ω problem based on the Finite Element Method (FEM). Finally, we present a comparison of the two methods on experimental datasets from InAsSb nanostructures with different thermal transport properties, to stress the crucial need of a FEM counterpart to 3 ω measurements in nanostructures with low thermal conductivity. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the neutrino-driven winds that emerge in 12 unprecedentedly long-duration 3D core-collapse supernova simulations done using the code F ornax. The 12 models cover progenitors with zero-age main-sequence mass between 9 and 60 solar masses. In all our models, we see transonic outflows that are at least 2 times as fast as the surrounding ejecta and that originate generically from a proto−neutron star surface atmosphere that is turbulent and rotating. We find that winds are common features of 3D simulations, even if there is anisotropic early infall. We find that the basic dynamical properties of 3D winds behave qualitatively similarly to those inferred in the past using simpler 1D models, but that the shape of the emergent wind can be deformed, very aspherical, and channeled by its environment. The thermal properties of winds for less massive progenitors very approximately recapitulate the 1D stationary solutions, while for more massive progenitors they deviate significantly owing to aspherical accretion. The Y e temporal evolution in winds is stochastic, and there can be some neutron-rich phases. Though no strong r -process is seen in any model, a weak r -process can be produced, and isotopes up to 90Zr are synthesized in some models. Finally, we find that there is at most a few percent of a solar mass in the integrated wind component, while the energy carried by the wind itself can be as much as 10%–20% of the total explosion energy. [ABSTRACT FROM AUTHOR]

The properties of optical coatings play an important role in precision experiments. Gravitational-wave detectors not only require the highest quality coatings but also ones with relatively large diameters. Coatings made with amorphous material can be scaled up easily but for now exhibit relatively high thermal noise characteristics. Crystalline coatings show great promise in terms of their thermal noise properties but cannot easily scale up to the needed sizes. In this paper we explore the possibility of a piecewise coating that includes both amorphous and crystalline material. Specifically, we estimate the scattering losses of such a piecewise coating as a function of the mismatch in the interface between the two coatings. The calculation should be taken as a lower limit to the total losses, as other surface imperfections will play an important role in the final result, but are not considered here. Finally, we present a measurement of the scattering losses from a piecewise coating, to showcase the challenges of realizing such a design. [ABSTRACT FROM AUTHOR]

It is well known that the laser diode performance will inevitably deteriorate when the device is heated. It has been a difficult issue to solve to date. In this letter, we are reporting a new solution to improve high-temperature performance of the laser diodes. The device uses a kind of directly-coupled well-wire hybrid quantum confinement (HQC) structure of the active medium based on the InGaAs–GaAs–GaAsP material system. This special HQC structure is constructed based on the strain-driven indium (In)-segregation effect and the growth orientation-dependent on-GaAs multi-atomic step effect. The measurement and analysis for the HQC laser sample show that the carrier leakage loss, the Auger recombination and gain-peak shifting due to heating are reduced in the HQC structure. It therefore increases the optical gain for lasing at high temperature. The power conversion efficiency is enhanced by >57% and the threshold carrier density drops by >24% at T ⩾ 360 K, in comparison to the traditional quantum-well laser performance. A higher characteristic temperature of 240 K is obtained as well. It implies the better thermal stability of the HQC laser structure. These achievements show a significant prospect for developing high thermo-optic performance of laser diodes. [ABSTRACT FROM AUTHOR]

Micro/nano electronic devices heat dissipation depends heavily on the thermal interface materials (TIMs). Despite notable progress, it is hard to efficaciously enhance the thermal properties of the hybrid TIMs with high-load additives due to an absence of effective heat transfer routes. Herein, the low content of three-dimensional (3D) graphene with interconnected networks is adopted as the additive to improve the thermal properties of epoxy composite TIMs. The thermal diffusivity and thermal conductivity of the as-prepared hybrids were dramatically improved by constructing thermal conduction networks after adding 3D graphene as fillers. The 3D graphene/epoxy hybrid's optimal thermal characteristics were observed at 1.5 wt% of 3D graphene content, corresponding to a maximum enhancement of 683%. Besides, heat transfer experiments were further performed to determine the superb heat dissipation potential of the 3D graphene/epoxy hybrids. Moreover, the 3D graphene/epoxy composite TIM was also applied to high-power LED to improve heat dissipation. It effectively reduced the maximum temperature from 79.8 °C to 74.3 °C. These results are beneficial for the better cooling performance of electronic devices and provide useful guidelines for advancing the next-generation TIMs. [ABSTRACT FROM AUTHOR]

Short Sansevieria cylindrica fibre/polylactic acid composites (SCFP) were fabricated using a twin screw extruder followed by the hot press technique, with variations in fibre loadings of 10 wt%, 20 wt%, 30 wt% and 40 wt%. The thermal properties of SCFP were assessed through dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Notably, the samples loaded with 40 wt% of fibre exhibited an increased storage modulus. In terms of loss modulus, the fibre-loaded samples displayed high values, indicating more heat is released during DMA experiment. Interestingly, the composite trend did not solely rely on increasing fibre loading, highlighting the intricate interplay between reinforcement and matrix crucial for determining viscoelastic properties across various temperatures. The TGA results revealed a decrease in inflection temperature with increasing fibre loadings, accompanied by a proportional rise in residues. The DSC thermograms indicated minimal differences in T _g , T _cc , and T _m values among composites with varying fibre loadings. However, neat PLA showed slightly higher values than the composites. On the other hand, reinforcing SCF into the PLA matrix promoted the crystallization of PLA by 1%–3% with the maximum degree of crystallinity of 25.4% obtained for 30 wt% of SCFP.

The investigation of thermal transport is crucial to the thermal management of modern electronic devices. To obtain the thermal conductivity through solution of the Boltzmann transport equation, calculation of the anharmonic interatomic force constants has a high computational cost based on the current method of single-point density functional theory force calculation. The recent suggested machine learning interatomic potentials (MLIPs) method can avoid these huge computational demands. In this work, we study the thermal conductivity of two-dimensional MoS2-like hexagonal boron dichalcogenides (H-B2 VI 2; VI = S, Se, Te) with a combination of MLIPs and the phonon Boltzmann transport equation. The room-temperature thermal conductivity of H-B2S2 can reach up to 336 W⋅m−1⋅K−1, obviously larger than that of H-B2Se2 and H-B2Te2. This is mainly due to the difference in phonon group velocity. By substituting the different chalcogen elements in the second sublayer, H-B2 VIVI ′ have lower thermal conductivity than H-B2 VI 2. The room-temperature thermal conductivity of B2STe is only 11% of that of H-B2S2. This can be explained by comparing phonon group velocity and phonon relaxation time. The MLIP method is proved to be an efficient method for studying the thermal conductivity of materials, and H-B2S2-based nanodevices have excellent thermal conduction. [ABSTRACT FROM AUTHOR]

In the last two decades, magnetic, thermodynamic properties and bipartite thermal entanglement in diamond spin clusters and chains have been studied. Such spin structures are presented in various compounds. The ions of Cu2+ in the natural mineral azurite are arranged in a diamond spin chain. There are no studies of the entanglement behaviour during the quantum evolution of such systems. Herein, we consider the evolution of entanglement in the diamond spin-1/2 cluster. This cluster consists of two central spins described by the anisotropic Heisenberg model, which interact with two side spins via Ising interaction. The influence of the interaction coupling with side spins on the entanglement of central spins is investigated. It is shown that choosing the value of this coupling allows us to control the behaviour of entanglement between central spins. As a result, we find conditions for achieving the maximal values of entanglement. In addition, the entanglement behaviour between the side spins, central and side spins, and between a certain spin and the rest of the system is studied. In these cases, the conditions for achieving maximal entanglement are also obtained. [ABSTRACT FROM AUTHOR]

This paper reports an enhancement of the nonlinear conductivity, thermal and mechanical properties of micro-silicon carbide/silicone elastomer (m-SiC/SE) composites by adding nano-aluminum nitride (n-AlN) for power module encapsulation applications. The electrical properties (such as nonlinear conductivity characteristics and transient permittivity obtained from polarization current, and trap distributions obtained from thermally stimulated depolarization current) and material properties (including thermo-gravimetric analysis, coefficient of thermal expansion (CTE), and thermal conductivity, tensile strength, strain at break and Young’s modulus) of the pure SE, m-SiC/SE microcomposites, m-SiC/n-AlN/SE hybrid composites are investigated. The effect of the m-SiC fillers and n-AlN fillers on physicochemical properties of the SE matrix is analyzed by FT-IR spectroscopy and crosslinking degree. The measured nonlinear conductivity and transient permittivity are used for electric field simulation under DC stationary and square voltages. It is found that the addition of n-AlN fillers in the SE hybrid composite improves the nonlinear conductivity characteristics and mitigates the electric field under DC stationary and square voltages, compared to the SE microcomposite. Furthermore, the m-SiC/n-AlN/SE hybrid composite has a higher thermal degradation temperature, thermal conductivity, tensile strength, Young’s modulus, and crosslinking degree than the SE microcomposite, whereas their CTE and strain at break are lower. It is elucidated that the m-SiC/n-AlN/SE hybrid composite with enhanced nonlinear conductivity and material properties is a promising packaging material for high-voltage power modules. [ABSTRACT FROM AUTHOR]

Thermal conductivity of porous graphene can be affected by defect concentration, nanopore shape and distribution, and it is hard to clarify the effects due to the correlation of those factors. In this work, molecular dynamics simulation is used to compare the thermal conductivity of graphene with three shapes of regularly arranged nanopores. The results prove the dominant role of defect concentration under certain circumstances in reducing thermal conductivity, while the coupling effect of nanopore shape should be noticed. When the atoms at the local phonon scattering area around each nanopore are properly removed, the abnormal increment of thermal conductivity can be detected with the increase of defect concentration. Heat flux vector angles can effectively characterize the local phonon scattering area, which can be used to describe the effect of nanopore shape. The coupling effect of defect concentration and pore shape with similar heat flux path is clarified according to this process. By adjusting vertex angle of triangle defect, there is a balanced state of the effect factors between the variation of defect concentration and the same phonon scattering area. It provides a possible way to describe the weighing factors of the coupling effect. The results suggest a feasible approach to optimize and regulate thermal properties of porous graphene in nanodevice. [ABSTRACT FROM AUTHOR]

Recognizing high performance thermoelectric (TE) ceramics is challenging due to high thermal conductivity and interdependent electrical and thermal transport properties. Herein we report the strategy of isovalent Al substitution in LaCoO3, which resulted in the enhancement of electrical conductivity by band engineering and increased charge carrier mobility via effective mass and Fermi energy optimization. The Al substitution in LaCoO3 not only enhances the electrical transport properties but also decrease the lattice thermal conductivity through enhanced phonon scattering originated from the lattice strain induced by huge mass fluctuation of Co and substituted Al atom. The results indicate that the electrical conductivity increase with increasing the Al substitution and the maximum value of 642 S cmâˆ'1 was observed at 753 K and the maximum power factor (73.3 µ W mâˆ'1Kâˆ'2) was achieved at 703 K for the sample LaCo0.97Al0.03O3. The Al-substitution enhanced the charge carrier mobility from 0.21 cm2 Vâˆ'1 sâˆ'1 to 51.6 cm2 Vâˆ'1 sâˆ'1 by decreasing the effective mass from 28.76*me to 12.76*me. The decreased carrier concentration with Al substitution is due to the upward shift of Fermi energy towards the conduction band. The lowest thermal conductivity value (0.87 W mâˆ'1Kâˆ'1) was obtained at 303 K for the sample LaCo0.95Al0.05O3. The lattice thermal conductivity of LaCo0.95Al0.05O3 (1.259 W mâˆ'1Kâˆ'1) was reduced about 48% when compared with pure LaCoO3 (2.437 W mâˆ'1Kâˆ'1) at 753 K. The present work reveals the importance of decoupling the electrical and thermal transport properties in achieving high performance TE ceramics. [ABSTRACT FROM AUTHOR]

Copper (Cu) coatings with a high surface area have attracted significant attention for functional devices due to their high thermal and electrical properties. Pulse-reverse current (PRC) electrodeposition has been introduced to fabricate Cu coatings for a long history, but compared to the individual anodic step, little attention has been paid to the synergistic effects of anodic and cathodic steps. The new parameter “artificial exchange current density” (jA) has been demonstrated to quantify the effects of anodic and cathodic currents on the morphology in our previous work. Herein, a key metric−the relative current amplitude−that is positively correlated with jA, is used to further clarify the role of jA in the electrodeposition process. We fabricate Cu coatings with welldispersed pyramid-like structures and find the relative current amplitude dominates the formation of a larger raised structure at the initial nucleation stage. Moreover, it is speculated that the anodic current can dissolve high-energy planes and achieve a highly (111)-oriented texture. Afterward, screw dislocation drives the spiral growth of grains, resulting in pyramid-like structures. This study not only enriches our understanding of the artificial exchange current density in PRC electrodeposition but also guides us to achieve Cu coatings with high surface area. [ABSTRACT FROM AUTHOR]

A carbon nanosphere nanofluid (CNS-nanofluid) was successfully prepared through the non-covalent modification of carbon nanosphere (CNS) with the specific ionic liquid (i.e. [M2070][VBS]) at first. The resulting CNS-nanofluid is a homogeneous and stable fluid with liquid-like behaviour at room temperature, and which shows better dispersion stability in its good solvents and improved processability than the pristine CNS. Subsequently, this CNS-nanofluid was used as a kind of novel functional filler and incorporated into epoxy matrix to prepare the CNS-nanofluid filled epoxy composites (CNS-nanofluid/EP composites). The toughness and thermal properties of those CNS-nanofluid/EP composites were carefully characterized and analysed. And it was found that this CNS-nanofluid could respectively improve the impact toughness and glass transition temperature of the CNS-nanofluid/EP composites to 19.8 kJ mâˆ'2 and 122.5 °C at the optimum amount, demonstrating that this CNS-nanofluid is a kind of promising functional filler to achieve robust epoxy composites, and thus opening up new possibilities with great significance for epoxy composites in high-performance applications. [ABSTRACT FROM AUTHOR]

Diamond due to its outstanding optical, electrical, mechanical and thermal properties finds an important place in electronic, opto-electronic and quantum technologies. Recent progresses showing superconductivity in diamond by boron doping has opened up many avenues including its applications in SQUID devices especially with polycrystalline diamond films. Granular boron doped diamond films find applications in quantum inductance devices where high surface inductance is required. Particularly important are the defect centers in diamond like nitrogen-vacancy (N-V), silicon vacancy (SiV) and other color centers which are ideal candidates for next generation quantum hardware systems. For efficient device applications, an indispensable need remains for a substitutional donor in diamond lattice that yields a lower thermal activation energy at room temperature. In this review, a comprehensive summary of research and the technological challenges has been reported including some of the results on nitrogen doping in polycrystalline diamond to understand the transport phenomenon emphasizing on its possible future applications. [ABSTRACT FROM AUTHOR]

With its excellent mechanical and thermal properties, bilayer graphane is a promising material for realizing future nanoelectromechanical systems. In this study, we focus on the auxetic behavior of bilayer graphane under external loading along various directions through atomistic simulations. We numerically and theoretically reveal the mechanism of the auxeticity in terms of intrinsic interactions between carbon atoms by constructing bilayer graphane. Given that the origin of the auxeticity is intrinsic rather than extrinsic, the work provides a novel technique to control the dimensions of nanoscale bilayer graphane by simply changing the external conditions without the requirement of complex structural design of the material. [ABSTRACT FROM AUTHOR]

Motivated by recent progress in the two-dimensional (2D) materials of group VI elements and their experimental fabrication, we have investigated the stability, optoelectronic and thermal properties of Janus α -Te2S monolayer using first-principles calculations. The phonon dispersion and MD simulations confirm its dynamical and thermal stability. The moderate band gap (∼1.5 eV), ultrahigh carrier mobility (∼103 cm2 Vâˆ'1 sâˆ'1), small exciton binding energy (0.26 eV), broad optical absorption range and charge carrier separation ability due to potential difference (Î" V  = 1.07 eV) on two surfaces of Janus α -Te2S monolayer makes it a promising candidate for solar energy conversion. We propose various type-II heterostructures consisting of Janus α -Te2S and other transition metal dichalcogenides for solar cell applications. The calculated power conversion efficiencies of the proposed heterostructures, i.e. α -Te2S/T-PdS2, α -Te2S/BP and α -Te2S/H-MoS2 are ∼21%, ∼19% and 18%, respectively. Also, the ultralow value of lattice thermal conductivity (1.16 W mâˆ'1 Kâˆ'1) of Janus α -Te2S makes it a promising material for the fabrication of next-generation thermal energy conversion devices. [ABSTRACT FROM AUTHOR]

Sr _1-x Gd _x TiO _3 (0.00 ≤ x ≤ 0.11) ceramics by the addition of Gd ^3+ on A-sites, were processed and fabricated through the conventional sintering method and optimised the sintering temperature at 1390 °C–1470 °C for 2 h. The experimentation shows that all ceramics are possessed by cubic structure, in which the increment of Gd ^3+ content, in terms of x, decreases the lattice parameters of the ceramics, as well as affects the grain size. Comparing the results to pure SrTiO _3 (STO) compounds, the addition of Gd ^3+ lowers the mass loss, increased the conductivity as well as permittivity by decreasing the dielectric losses at lower frequencies. The x = 0.03 and 0.01 evidenced the maximum Seeback Coefficient, ∼281 μ V K ^−1 at ∼370 K confirming the higher carrier concentration. Also, the magnetic properties as a function of Gd ^3+ ions doped with STO showed gradual improvement, showing maximum saturation with the maximum concentration of x.

The current study aims in enhancing the impact properties of polypropylene/basalt fiber composite reinforced with different wt% of ethylene propylene diene monomer (EPDM) elastomer to identify the optimum wt% of EPDM at which a balance in strength and toughness can be obtained. According to a dynamic mechanical study, the composite’s viscoelastic behaviour and damping properties improved as the EPDM weight percentage increased in comparison to virgin polypropylene. Scanning and transmission electron microscopy were utilized to see the composite’s fragmented surface. Finally, it was concluded that the presence of a renewable basalt fiber helped in obtaining stability between the strength and toughness of polypropylene-toughened composites. Finally for up to 20 wt% EPDM there was a balance in the composite stiffness and strength.

Polyvinyl chloride (PVC) hybrid film containing cerium, tin and folic acid modified nano titanium dioxide is a new functional material with good compatibility, light resistance and heat resistance. In this work, the PVC hybrid film was prepared by replacing cerium with lanthanum. The hybrid film was characterized by thermogravimetric infrared spectroscopy, dynamic mechanical analysis, atomic force microscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, tensile strength and thermal aging. The results show that the initial thermal stability of the hybrid film containing lanthanum is slightly higher than that of the control sample (conversion α < 1.9%). For the same gaseous component plasticizer, the peak intensity of the ester based infrared characteristic group is higher than that of the hybrid film containing lanthanum, indicating that the intermolecular force between lanthanum and plasticizer is greater than that of cerium. In the range of 350 °C–575 °C and the wave number range of 2850–3100 cm ^−1 , the peak height of the lanthanum containing film is significantly higher than that of the control sample, which may be due to the difference of the outer layer electrons. The peak intensity of O and C atoms on the surface of the hybrid film containing lanthanum is significantly lower than that of the control sample, indicating that the surface relative concentration of lanthanum atoms is lower than that of cerium atoms. The surface roughness RMS of the hybrid film containing lanthanum is significantly lower than that of the organic tin film, which is the result of the attraction between folic acid modified TiO _2 , lanthanum and tin and the carbon chlorine bond in PVC. It has the function of a potential ultrafiltration membrane. In addition, the hybrid film containing 1phr lanthanum shows good energy storage modulus and low temperature resistance. The prepared hybrid film shows the characteristics of a potential multi-functional material.

The unique combination of excellent mechanical and functional properties makes graphene an ideal component for high-performance ‘smart’ composites, which are sensitive to thermal, optical, electrical and mechanical excitations, hence being potential in application of a range of sensors. It has confirmed that the addition of graphene into metal matrix can significantly enhance the mechanical property and deliver surprising functional properties. Thus, graphene reinforced metal matrix composites (GMMCs) have long been regarded as potential prospects of nanotechnology applications. Recently, researchers mainly focused on: (i) solving the interfacial issues and realizing controllable alignment of graphene in metal matrix to achieve optimal performance; (ii) reasonable designing of the microstructures basing on usage requirement and then fabricating via efficient technique. Thus, it is necessary to figure out key roles of microstructure in fabrication process, mechanical and multi-functional properties. This review consists of four parts: (i) fabrication process. The fabrication processes are firstly divided into three kinds basing on the different bonding nature between graphene and metal matrix. (ii) Mechanical property. The microstructural characteristics of metal matrix accompanying by the incorporation of graphene and their vital effects on mechanical properties of GMMCs are systematically summarized. (iii) Functional property. The crucial effects of microstructure on electrical and thermal properties are summarized. (iv) Prospect applications and future challenges. Application and challenges basing on the research status are discussed to provide useful directions for future exploration in related fields. All these four parts are discussed with a focus on key role of microstructure characteristics, which is instructive for the microstructures design and fabrication process optimization during academic researches and potential commercial applications. [ABSTRACT FROM AUTHOR]

We investigate the impact of cosmic filaments on the gas accretion rate, , of dark matter halos in filaments, based on cosmological hydrodynamic simulation. We find that for halos less massive than 1012.0M⊙, of halos residing in prominent filaments (with width Dfil > 3 Mpc h−1) is lower than halos residing in tenuous filaments (Dfil < 3 Mpc h−1) by 20%–30% at z = 0.5 and by a factor of 2–3 at z = 0. However, depends weakly on the physical distance between halo center and the spine of filaments from high redshift to z = 0 and only shows a clear difference between the inner and outer regions in prominent filaments at z = 0. We further probe the thermal properties of gas in prominent and tenuous filaments, which appear in relatively highly and intermediate overdense regions, respectively. The gas in prominent filaments is hotter. Around 26%, 38%, and 45% of gases in prominent filaments are hotter than 106 K at z = 1.0, 0.5, and 0.0, respectively. The corresponding fractions in tenuous filaments are merely ∼6%, 9%, and 11%. The suppressed gas accretion rate for low-mass halos in prominent filaments at z ≲ 0.5 may result from the hotter ambient gas, which could provide a physical processing mechanism to cut down the supply of gas to halos before they enter clusters. This process partially meets the need of the preheating mechanism implemented in some semianalytical models of galaxy formation but works only for ∼20% of halos at z < 1. [ABSTRACT FROM AUTHOR]

We report the transport properties of a topological insulator candidate, LiMgBi. The electric resistivity of the title compound exhibits a metal-to-semiconductor-like transition at around 160 K and tends to saturation below 50 K. At low temperatures, the magnetoresistance is up to ∼260 % at 9 T and a clear weak antilocalization effect is observed in the low magnetic-field region. The Hall measurement reveals that LiMgBi is a multiband system, where hole-type carriers (n h ∼ 1018 cmâˆ'3) play a major role in the transport process. Remarkably, LiMgBi possess a large Seebeck coefficient ∼440 ÎĽV/K) and a moderate thermal conductivity at room temperature, which indicate that LiMgBi is a promising candidate in thermoelectric applications. [ABSTRACT FROM AUTHOR]

Double-sided thin-film resistance temperature detector (RTD) heat flux gauges (HFGs) are commonly used to characterize heat transfer rates in high-heat flux environments with complex flow features. These gauges comprise two thin-film RTDs on opposing sides of a dielectric. To deduce accurate heat flux, the RTDs must be properly calibrated and the material properties of the dielectric must be characterized. This study presents a complete gauge characterization method for sensors of this type by applying standard calibration procedures with specially-designed RTDs capable of utilizing the 3-omega method. The 3-omega method quantifies the thermal conductivity and thermal product of a material by measuring the response of a specially designed heater/thermometer deposited on the substrate. This study shows the 3-omega method enables RTD calibrations and thermal property determination over a range of temperatures for individual gauges, reducing the uncertainty in calculated heat flux. Although the method is quite general, this study utilized platinum RTDs with a polyimide dielectric, which is common in turbomachinery applications. The thermal properties obtained through this method agree with previous characterization efforts; however, discrete characterization of seven gauges shows that gauge-to-gauge variation in the dielectric could influence measured heat flux by as much as 30%. This study also builds the framework to characterize the thermal conductivity of the adhesive layer beneath the gauge which is necessary to mount the sensors to the test article. Although often uncharacterized, the adhesive thermal conductivity has a significant impact on matching experimental measurements to simulations. Additionally, this study found that if the thermal conductivity of the dielectric is constant (an assumption that holds for the present study), an in-situ RTD calibration can be performed. In-situ RTD calibration and traditional method RTD calibration agreed to within 0.1%. Overall, this work has practical implications in obtaining high quality measurements from HFGs of this type. [ABSTRACT FROM AUTHOR]

Of late, atomically thin two-dimensional zinc-sulfide (2D-ZnS) shows great potential for advanced nanodevices and as a substitute to graphene and transition metal di-chalcogenides owing to its exceptional optical and electronic properties. However, the functional performance of nanodevices significantly depends on the effective heat management of the system. In this paper, we explored the thermal transport properties of 2D-ZnS through molecular dynamics simulations. The impact of length, temperature, and vacancy defects on the thermal properties of 2D-ZnS are systematically investigated. We found that the thermal conductivity (TC) rises monotonically with increasing sheet length, and the bulk TC of ∼30.67 W mK−1 is explored for an infinite length ZnS. Beyond room temperature (300 K), the TC differs from the usual 1/T rule and displays an abnormal, slowly declining behavior. The point vacancy (PV) shows the largest decrease in TC compared to the bi vacancy (BV) defects. We calculated phonon modes for various lengths, temperatures, and vacancies to elucidate the TC variation. Conversely, quantum corrections are used to avoid phonon modes' icing effects on the TC at low temperatures. The obtained phonon density of states (PDOS) shows a softening and shrinking nature with increasing temperature, which is responsible for the anomaly in the TC at high temperatures. Owing to the increase of vacancy concentration, the PDOS peaks exhibit a decrease for both types of defects. Moreover, the variation of the specific heat capacity and entropy with BV and PV signify our findings of 2D-ZnS TC at diverse concentrations along with the different forms of vacancies. The results elucidated in this study will be a guide for efficient heat management of ZnS-based optoelectronic and nano-electronic devices. [ABSTRACT FROM AUTHOR]

Strong interfacial bonding is the basic requirement for metal-graphene composites for higher thermo-mechanical properties. In the present work, a novel metal tantalum is introduced in the metal-graphene composites prepared by (ball-milling + molecular level mixing) followed by hot press sintering. SEM, transmission electron microscopy and high transmission electron microscopy are observed to check the interface area which shows the presence of tantalum carbide on the interface area which is formed during the sintering process. The formation of the carbide element significantly enhances the mechanical properties of composites. The addition of a very low amount of 0.1 vol% of rGO give the very high yield strength 200 MPa and ultimate tensile strength value 375 MPa with the good agreement of ductility, Vickers hardness 95 HV and bending strength 617 MPa which are much higher than unreinforced copper–tantalum composites and even from pure copper. The anisotropic thermal conductivity values are also significantly improving due to the better interfacial bonding and the ratio was 5 which is just 1.01 for pure copper. The formation of carbide elements and extraordinary high mechanical values with good ductility and anisotropic thermal conductivity ratio can lead to these materials used in thermal packaging systems and the electronic industry. [ABSTRACT FROM AUTHOR]

Cryogenic ultra-stable Fabry–Perot cavity is one of the most promising reference cavities for laser stabilization. Here we investigate the thermal property of a hydroxide catalysis bonded silicon–sapphire hybrid cavity for 1064 nm laser stabilization. The zero-thermal expansion temperature is measured to be 15.0 ± 0.1 K, with a slope calculated to be 3 × 10−10 K−2. A simulation model with a few micrometer thick silicon oxidation layer reproduces well the experimental results. The investigations on the thermal property of the hydroxide catalysis bonded components are important for the noise evaluation and optimization. This work would be valuable for the advanced cryogenic optics, and would be interested for researchers working on cryogenic ultra-stable lasers and cryogenic gravitational wave detectors. [ABSTRACT FROM AUTHOR]

Two different integration technologies of GaN-on-diamond are explored, direct growth of polycrystalline diamond (PCD) on GaN (sample A) and deposition of GaN on PCD (sample B). The reversed evolution of PCD grain structure is assumed for each technology, resulting in an increasing/decreasing tendency of thermal conductivity with growth thickness. Simulation of AlGaN/GaN high electron mobility transistors on PCD substrate with capped diamond is made considering anisotropic and inhomogeneous thermal conductivities of GaN and PCD, different combinations of thermal boundary resistance (TBR) values at the top diamond/GaN and bottom GaN/PCD substrate are investigated. The results show that the effect of top TBR is limited and increasing the bottom TBR from 6.5 to 100 m2K GW−1 results in a temperature rise of 80.8 °C for sample A and 85.3 °C for sample B at power dissipation of 10 W mm−1. Enlarging the thickness of capped diamond helps to reduce the junction temperature, which is more effective at small top TBR under constant bottom TBR and at large bottom TBR with fixed top TBR. In addition, increasing gate pitch is a promising solution to reduce junction temperature and a weak dependence of junction temperature on gate width is revealed. [ABSTRACT FROM AUTHOR]

In this paper, the structural stability, electronic, optical, mechanical, and thermal properties of diphenylacetylene-based graphyne (DPAG) nanosheet are investigated using first-principle calculations based on density functional theory (DFT). The absolute value of the calculated cohesive energy reveals that DPAG nanosheet is a structurally stable two-dimensional material. Also, in the results of phononic dispersion curves, the absence of imaginary frequencies confirms the dynamic stability of this novel material. In addition, the theoretical electronic band structure and density of states reveal the semiconducting nature of DPAG nanosheet. The optical analysis shows that the first absorption peaks of the imaginary and real parts of dielectric constants along the in-plane and out-of-plane polarizations of DPAG monolayer occur in the visible range of the electromagnetic spectrum. On the other hand, the DPAG nanosheet exhibits orthotropic elastic behavior with four independent constants comparable with the data of similar materials available in the literature. Moreover, DFT calculations of the lattice thermal conductivity of DPAG reveals an anomalously very low thermal conductivity of this nanosheet showing its perfect thermal non-conductivity. Our results provide deep insights into the potential applications of DPAG nanosheet for the design of new optoelectronic/nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Details of an experimental set-up and an evaluation method for determining temperature dependent thermal conductivities from one-dimensional steady-state temperature distributions are presented. The method is validated by obtaining continuous values for the thermal conductivities of pure Ni in the temperature range between 440 K and 740 K, brass (Cu-30Zn) in the temperature range between 350 K and 650 K and a titanium aluminide (TiAl-TNM) in the temperature range between 400 K and 700 K. The results are in agreement with available literature data. The reported scatter in the literature on conductivities is caused by microstructural or/and compositional differences, which highlights the necessity for swift and accurate experimental determination of thermal properties. For this, the proposed temperature gradient evaluation method is especially suited as it allows the direct determination of thermal properties within large temperature intervals using only a single experimental run. The experimental effort for a comprehensive study of a material is thus drastically reduced as compared to the conventional method of determining thermal conductivity from measured thermal diffusivities and heat capacities. The experimental set-up additionally allows the independent determination of thermal diffusivity as function of temperature. No prior knowledge of any material properties of a given sample is necessary. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) is a strongly correlated material, and it has become known due to its sharp metal-insulator transition (MIT) near room temperature. Understanding the thermal properties and their change across MIT of VO2 thin film is important for the applications of this material in various devices. Here, the changes in thermal conductivity of epitaxial and polycrystalline VO2 thin film across MIT are probed by the time-domain thermoreflectance (TDTR) method. The measurements are performed in a direct way devoid of deposition of any metal thermoreflectance layer on the VO2 film to attenuate the impact from extra thermal interfaces. It is demonstrated that the method is feasible for the VO2 films with thickness values larger than 100 nm and beyond the phase transition region. The observed reasonable thermal conductivity change rates across MIT of VO2 thin films with different crystal qualities are found to be correlated with the electrical conductivity change rate, which is different from the reported behavior of single crystal VO2 nanowires. The recovery of the relationship between thermal conductivity and electrical conductivity in VO2 film may be attributed to the increasing elastic electron scattering weight, caused by the defects in the film. This work demonstrates the possibility and limitation of investigating the thermal properties of VO2 thin films by the TDTR method without depositing any metal thermoreflectance layer. [ABSTRACT FROM AUTHOR]

Ab initio calculations of mechanic, electronic and thermodynamic properties for the perovskite Dy2Bi2Fe4O12 oxide compound are reported. The mechanical analysis showed that the material presents elastic anisotropy, with Poisson and Pugh ratios typical of a ductile material, which is due to the possibility of shear between structural cells. The band structure calculations were carried out through first principles calculations, using the formalism of the Functional Density Theory and the Flat Wave and Pseudopotential method through the VASP code. The exchange and correlation energy was described by the Generalized Gradient Approximation, including spin polarization and the Hubbard's potential correction due to the presence of Fe-3d orbitals. The semiconductor behaviour of the material was established since a band gap of 1.76 eV was obtained. The material evidenced a ductile mechanical nature due to the tendency to respond to shear stresses and a hardness value that is consistent with reports made for other perovskite-type materials. The dependence of specific heat with respect to temperature and pressure, thus such as the coefficient of thermal expansion, the Debye temperature and the Grüneisen parameter, were calculated from the equation of state, using the quasi-harmonic Debye model. Changes in temperature and pressure modify the vibrations in the interatomic bonds, directly affecting the thermodynamic properties of the material. The theoretical results obtained are comparable with the experimental values obtained in the literature for this material reported as a ferromagnetic semiconductor. [ABSTRACT FROM AUTHOR]

Unlike tremendous works on the electronic structures of tetradymite compounds, studies of their thermal properties are relatively rare. Here, first-principles calculations and Boltzmann theory are combined to investigate the phonon transport of such kind of layered materials. Using four binary tetradymites as prototypical examples, it is interesting to find that the weak van der Waals (vdW) interactions play an important role in determining their lattice thermal conductivities, which are obviously higher than those without the consideration of vdW, especially for the out-of-plane direction. In principle, such enhanced phonon transport can be attributed to the decreased interlayer spacing caused by the presence of vdW, which effectively reduces the strong anharmonicity of the systems. Indeed, we observe relatively smaller Grüneisen parameter together with larger phonon group velocity and relaxation time. Our theoretical work demonstrates the vital importance of the seemingly weak vdW forces in predicting the phonon transport properties of various layered structures. [ABSTRACT FROM AUTHOR]

Layered two-dimensional (2D) materials such as MoS2 have attracted much attention for nano- and opto-electronics. Recently, intercalation (e.g. of ions, atoms, or molecules) has emerged as an effective technique to modulate material properties of such layered 2D films reversibly. We probe both the electrical and thermal properties of Li-intercalated bilayer MoS2 nanosheets by combining electrical measurements and Raman spectroscopy. We demonstrate reversible modulation of carrier density over more than two orders of magnitude (from 0.8 × 1012 to 1.5 × 1014 cm−2), and we simultaneously obtain the thermal boundary conductance between the bilayer and its supporting SiO2 substrate for an intercalated system for the first time. This thermal coupling can be reversibly modulated by nearly a factor of eight, from 14 ± 4.0 MW m−2 K−1 before intercalation to 1.8 ± 0.9 MW m−2 K−1 when the MoS2 is fully lithiated. These results reveal electrochemical intercalation as a reversible tool to modulate and control both electrical and thermal properties of 2D layers. [ABSTRACT FROM AUTHOR]

A nanostructured n-type Bi2Te2.7Se0.3 (BTS) alloy with a unique microstructure was prepared using a facile melting-rotation-quenching process followed by ball-milling and uniaxial hot-press sintering at 623 K. Anisotropy in the resulting microstructure showed anisotropic electrical and thermal transport properties in two directions normal to the pressing axis. The texture of the nanostructured BTS alloy was analyzed by x-ray diffraction and scanning electron microscopy. Based on the geometric phase analysis of a high resolution transmission electron microscopy images, abundant dislocations, high grain boundary density, and oxide impurity were identified, which act as phonon scattering centers. Higher anisotropy in thermal conductivity combined with oxide impurity resulted in an ultra-low phonon thermal conductivity of ∼0.305 W mK−1 at 423 K in the nanostructured n-type BTS in the direction parallel to the pressing axis. Laser power- and temperature-dependent Raman spectra analyses provided a deeper insight into the anisotropy in thermal transport properties. Optimum power factor and low thermal conductivity, due to the combination of grain alignment and oxide impurity, resulted in a dimensionless figure of merit (zT) value of ∼0.75 at 423 K. In comparison, the high and opposite temperature dependences of electrical conductivity and thermal conductivity led to a better average zT value of ∼0.68 and a thermoelectric energy conversion efficiency percentage of ∼4.4% in the operating temperature range (300–423 K) in the direction parallel to the pressing axis. [ABSTRACT FROM AUTHOR]

We experimentally investigate effects of W6+ occupying the sites of Sc3+ in the unit cell of Sc2W3O12 (Sc8W12O48) on the structure, vibration and thermal expansion. The composition and structure of the doped sample (Sc6W2)W12O48 ± δ (with two W6+ occupying two sites of Sc3+ in the unit cell of Sc8W12O48) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W6+ occupying even Sc3+ in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc2W3O12, and with even W occupying even positions of Sc in the unit cell and constituting the WO6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc2W3O12. The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K. [ABSTRACT FROM AUTHOR]

It was experimentally found that silica and gold particles can modify the combustion properties of nanothermites but the exact role of the thermal properties of these additives on the propagating combustion front relative to other potential contributions remains unknown. Gold and silica particles of different sizes and volume loadings were added into aluminum/copper oxide thermites. Their effects on the flame front dynamics were investigated experimentally using microscopic dynamic imaging techniques and theoretically via a reaction model coupling mass and heat diffusion processes. A detailed theoretical analysis of the local temperature and thermal gradients at the vicinity of these two additives shows that highly conductive inclusions do not accelerate the combustion front while poor conductive inclusions result in the distortion of the flame front (corrugation), and therefore produce high thermal gradients (up to 1010 K.m−1) at the inclusion/host material interface. This results in an overall slowing down of the combustion front. These theoretical findings contradict the experimental observations in which a net increase of the flame front velocity was found when Au and SiO2 particles are added into the thermite. This leads to the conclusion that the faster burn rate observed experimentally cannot be fully associated with thermal effects only, but rather on chemical (catalytic) and/or mechanical mechanisms: formation of highly-stressed zones around the inclusion promoting the reactant mixing. One additional experiment in which physical SiO2 particles were replaced by voids (filled with Ar during experiment) to cancel the potential mechanical effects while preserving the thermal inhomogeneity in the thermite structure confirms the hypothesis that instead of pure thermal conduction, it is the mechanical mechanisms that dominate the propagation velocity in our specific Al/CuO multilayered films. [ABSTRACT FROM AUTHOR]

The thermal properties of individual single-walled carbon nanotubes (SWCNTs) have been well documented in the literature following decades of intensive study. However, when SWCNTs form a macroscale assembly, the thermal transport in these complex structures usually not only depends on the properties of the individual tubes, but also is affected and sometimes dominated by inner structural details, e.g. bundles and junctions. In this work, we first performed an experimental measurement of the thermal conductivities of individual SWCNT bundles of different sizes using a suspended micro-thermometer. The results, together with the data that we obtained from a previous work, give a complete experimental understanding of the effect of bundling on the thermal conductivity of SWCNTs. With these quantitative understandings, we propose a phenomenological model to describe the thermal transport in two-dimensional (2D) SWCNT films. The term 'line density' is defined to describe the effective thermal transport channels in this complex 2D network. Along with experimentally obtained geometric statistics and film transparency, the thermal conductance of SWCNTs is estimated, and the effects of bundle length, diameter, and contact conductance are systematically discussed. Finally, we extend this model to explain thermal transport in 2D networks of one-dimensional van der Waals heterostructures, which are coaxial hetero-nanotubes we recently synthesized using SWCNTs as the template. This extended model suggests that the contribution of boron nitride nanotubes (BNNTs) to the overall performance of a SWCNT–BNNT heterostructured film depends on the transparency of the original SWCNT film. The increase in the thermal conductance of a highly transparent film is estimated to be larger than that of a less transparent film, which shows a good agreement with our experimental observations and proves the validity of the proposed phenomenological model. [ABSTRACT FROM AUTHOR]

Over the past decade, two-dimensional semiconductors (2DSCs) have aroused wide interest due to their extraordinary electronic, magnetic, optical, mechanical, and thermal properties, which hold potential in electronic, optoelectronic, thermoelectric applications, and so forth. The field-effect transistor (FET), a semiconductor gated with at least three terminals, is pervasively exploited as the device geometry for these applications. For lack of effective and stable substitutional doping techniques, direct metal contact is often used in 2DSC FETs to inject carriers. A Schottky barrier (SB) generally exists in the metal–2DSC junction, which significantly affects and even dominates the performance of most 2DSC FETs. Therefore, low SB or Ohmic contact is highly preferred for approaching the intrinsic characteristics of the 2DSC channel. In this review, we systematically introduce the recent progress made in theoretical prediction of the SB height (SBH) in the 2DSC FETs and the efforts made both in theory and experiments to achieve low SB contacts. From the comparison between the theoretical and experimentally observed SBHs, the emerging first-principles quantum transport simulation turns out to be the most powerful theoretical tool to calculate the SBH of a 2DSC FET. Finally, we conclude this review from the viewpoints of state-of-the-art electrode designs for 2DSC FETs. [ABSTRACT FROM AUTHOR]

The anisotropic heat transfer properties of two-dimensional materials play an important role in controlled heat transfer and intelligent heat management. At present, there are many references on anisotropic heat transfer of two-dimensional materials, but less systematic review of their development status, problems, and future directions. In this paper, intrinsic anisotropic heat transfer of two-dimensional materials, influencing factors and control means are introduced. The preparation methods of thin film with two-dimensional material and the influence factors of macroscopic anisotropic thermal properties are summarized. The technology of two-dimensional material oriented arrangement in matrix and the influence factors of macroscopic anisotropic thermal properties of the composite are outlined. [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotubes (MWCNTs) are attractive materials for realizing sensors, owing to their high aspect ratio associated with excellent mechanical, electronic, and thermal properties. Moreover, their sensing properties can be tuned by introducing functional groups on their framework and adjusting the processing conditions. In this paper, we investigate the potential of functionalized CNTs for humidity and temperature sensing by optimization of the functionalization, the processing conditions and the printing conditions. The morphology of the differently functionalized MWCNTs is investigated by infrared spectroscopy (IR), scanning electron microscopy, thermogravimetry (TG) and TG-coupled mass-spectrometric studies. Using the functionalized MWCNTs, films were fabricated with different numbers of layers (4, 6, 8, 10 layers) via inkjet printing on a flexible polyimide substrate containing an interdigital microelectrode. The influence of hydrothermal effects was investigated. The sensitivity to humidity is higher for films prepared with MWCNTs functionalized with a high sonication amplitude and a bigger number of layers due to enhancements of hydrophilicity and water mobility. A higher sensitivity to temperature is achieved by a low sonication amplitude and a small number of layers. For the encapsulation of the temperature sensor against humidity, a Bectron layer is proposed, which reduces also the hysteresis effect. This study demonstrates the efficiency of carboxylic functionalized MWCNTs deposit by inkjet printing for realization of sensitive and cost-effective humidity and temperature sensors. It provides a real example for the interesting contribution of functionalization procedures to the sensing properties of MWCNTs films. [ABSTRACT FROM AUTHOR]

The thermal properties are one of the key parameters to control phase purity and microstructure of polycrystalline materials. The melting point of the iron-based BaFe2As2 superconductor (Ba122), which foresees high-field applications, remains controversial. In this work, thermogravimetry-differential scanning calorimetry measurements (TG-DSC) of undoped and Co-doped Ba122 were carried out. Mixtures of elemental metals and pre-reacted Ba122 powders were prepared to investigate the thermal responses during in situ and ex situ synthesis routes, respectively. In addition, the phases and microstructures of the quenched samples were evaluated to elucidate the observed exothermic/endothermic peaks. Our results suggest that the melting point of Ba122 is ∼1300 °C. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are very interesting latent heat storage systems used for various thermal energy storage applications, such as in energy-conserving buildings. Both organic compounds (such as paraffins) and inorganic compounds (such as hydrated salts) were tested in this field. Since they are often heterogeneous materials because of additives, the study of their thermal properties is now addressed from the conventional calorimetry to new methods based on more significant samples to better describe the heterogeneous structure, such as the T-history method. It requires a simple and inexpensive unit, but this equipment is not commercially available and must be set up in a laboratory. Consequently, this method does not have a standard configuration and it is continuously improving. One of the critical units of the T-history-based equipment is the cooling chamber and its operating conditions, whose choice influences the results. In this work, three different cooling chambers were used in the analysis of the thermal properties of hexadecane and Glauber's salt-based PCMs in order to verify the reliability and reproducibility of each system. [ABSTRACT FROM AUTHOR]

The transition from the diffuse warm neutral medium (WNM) to the dense cold neutral medium (CNM) is what set the initial conditions to the formation of molecular clouds. The properties of the turbulent cascade in the WNM, essential to describe this radiative condensation process, have remained elusive in part due to the difficulty in mapping out the structure and kinematics of each H i thermal phase. Here we present an analysis of a 21 cm hyper-spectral data cube from the GHIGLS H i survey where the contribution of the WNM is extracted using ROHSA , a Gaussian decomposition tool that includes spatial regularization. The distance and volume of the WNM emission is estimated using 3D dust extinction map information. The thermal and turbulent contributions to the Doppler line width of the WNM were disentangled using two techniques, one based on the statistical properties of the column density and centroid velocity fields, and the other on the relative motions of CNM structures as a probe of turbulent motions. We found that the volume of WNM sampled here (5.2 × 105 pc3), located at the outer edge of the Local Bubble, shows thermal properties in accordance with expected values for heating and cooling processes typical of the solar neighborhood: Pth/kB = (4.4 ± 2.6) × 103 K cm−3, n = 0.74 ± 0.41 cm−3, and Tk = (6.0 ± 1.3) × 103 K. The WNM has the properties of sub/trans-sonic turbulence, with a turbulent Mach number at the largest scale probed here (l = 130 pc) of , a density contrast of , and velocity and density power spectra compatible with k−11/3. The low Mach number of the WNM provides dynamical conditions that allow the condensation mode of thermal instability to grow freely and form CNM structures, as predicted by theory. [ABSTRACT FROM AUTHOR]

High thermal conductivity is an important parameter for nitride-based power electronic and deep-UV light emitters. Especially in the latter case short period superlattices and multicomponent alloys are used and the knowledge of the thermal properties of the binary compounds is sufficient. In-plane and cross-plane thermal conductivity of AlGaN/GaN superlattices were measured by differential two-wire 3ω method in the temperature range from 147 to 325 K. Samples were grown by metalorganic vapor phase epitaxy; the structure quality and accuracy of superlattice structures preparation were verified by means of HRXRD and transmission electron microscopy. It was observed, that value of thermal conductivities decrease with decreasing period thickness, while temperature dependencies differ from each other—in-plane thermal conductivity decreases, and cross-plane—increases with increasing temperature. Callaway method was used for thermal conductivity calculation; dependence of boundary scattering rate on the phonon wavelength was taken into account. Minimum thermal conductivity was added to calculated values to include the influence of high frequency acoustic phonons and optical phonons on the heat transport. Calculations are in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Currently, it is still unclear how and to what extent a change in temperature impacts the relative contributions of coherent and incoherent phonons to thermal transport in superlattices. Some seemingly conflicting computational and experimental observations of the temperature dependence of lattice thermal conductivity make the coherent–incoherent thermal transport behaviors in superlattices even more elusive. In this work, we demonstrate that incoherent phonon contribution to thermal transport in superlattices increases as the temperature increases due to elevated inelastic interfacial transmission. On the other hand, the coherent phonon contribution decreases at higher temperatures due to elevated anharmonic scattering. The competition between these two conflicting mechanisms can lead to different trends of lattice thermal conductivity as temperature increases, i.e. increasing, decreasing, or non-monotonic. Finally, we demonstrate that the neural network-based machine learning model can well capture the coherent–incoherent transition of lattice thermal transport in the superlattice, which can greatly aid the understanding and optimization of thermal transport properties of superlattices. [ABSTRACT FROM AUTHOR]