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In the context of ecological sustainability, this study focuses on the effect of variables of pasture fibers on the thermal properties of slag bricks made from a green recyclable material. This experiment uses slag as the binder, sand as the aggregate, and pasture fiber as an additive. The experimental variables include the additive content ratio of the pasture fiber, the size of the pasture fiber, and the type of pasture fiber. Significance analysis of the experimental results of the thermal performance tests is carried out using Minitab 18.1.0 software, and the optimal ratios for the thermal performance of the composite samples are derived from the response optimizer and conformity analysis. The results of the experiment's test analysis using Minitab 18 software indicate that, with an increase in pasture fiber content, the thermal performance of the composite samples initially decreases before increasing. Additionally, the lower the thermal conductivity of the composite sample, the lower the apparent density and the higher the porosity. Incorporating pasture fibers into slag bricks, as revealed in this study, reduces the waste of pasture resources in pastoral areas and promotes the development of sustainable building materials with favorable thermal properties. [ABSTRACT FROM AUTHOR]

The thermophysical properties of molten salts promising for the nuclear industry are crucial, but the available data are limited and contradictory. The thermal diffusivity of the molten mixtures (NaF-KF)eut–UF4 containing 30, 40, and 50 mol % UF4 was measured by the laser flash method. The thermal diffusivity was found to be almost independent of temperature in the range of about 100° (1070 K–1170 K), which makes it possible to extrapolate values to low or high temperatures. The thermal conductivity of the molten mixtures (NaF-KF)eut–UF4 was calculated using the thermal diffusivity, density, and heat capacity data. Density was estimated using the molar volume of the molten binary systems NaF-UF4 and KF-UF4. The heat capacity of the ternary system NaF-KF-UF4 was evaluated based on the heat capacity of individual salts, taking into account the additivity law. The thermal conductivity of the molten mixtures 0.7(NaF-KF)eut–0.3UF4, 0.6(NaF-KF)eut–0.4UF4, and 0.5(NaF-KF)eut–0.5UF4 changes slightly with the UF4 content and temperature; for example, at 1123 K it is 0.48, 0.45, and 0.45 W·m−1·K−1, respectively. The thermal diffusivity of the pure molten UF4 was estimated using three independent approaches: the concentration, the temperature, and the volume dependences of the thermal diffusivity. The estimated value of the thermal diffusivity for the molten UF4 was about 0.12 × 10–6 ± 0.05 × 10–6 m2·s−1. [ABSTRACT FROM AUTHOR]

The thermophysical properties of molten salts promising for the nuclear industry are crucial, but the available data are limited and contradictory. The thermal diffusivity of the molten mixtures (NaF-KF)eut–UF4 containing 30, 40, and 50 mol % UF4 was measured by the laser flash method. The thermal diffusivity was found to be almost independent of temperature in the range of about 100° (1070 K–1170 K), which makes it possible to extrapolate values to low or high temperatures. The thermal conductivity of the molten mixtures (NaF-KF)eut–UF4 was calculated using the thermal diffusivity, density, and heat capacity data. Density was estimated using the molar volume of the molten binary systems NaF-UF4 and KF-UF4. The heat capacity of the ternary system NaF-KF-UF4 was evaluated based on the heat capacity of individual salts, taking into account the additivity law. The thermal conductivity of the molten mixtures 0.7(NaF-KF)eut–0.3UF4, 0.6(NaF-KF)eut–0.4UF4, and 0.5(NaF-KF)eut–0.5UF4 changes slightly with the UF4 content and temperature; for example, at 1123 K it is 0.48, 0.45, and 0.45 W·m−1·K−1, respectively. The thermal diffusivity of the pure molten UF4 was estimated using three independent approaches: the concentration, the temperature, and the volume dependences of the thermal diffusivity. The estimated value of the thermal diffusivity for the molten UF4 was about 0.12 × 10–6 ± 0.05 × 10–6 m2·s−1. [ABSTRACT FROM AUTHOR]

AbstractFunctionalization of graphene nanosheet (GNS) is found to be useful for improving the thermal property of materials. However, the mechanism responsible for the enhancement is still open. In this article, molecular dynamic simulation is adopted to investigate the effects of four functionalized groups, including -COOH, -NH2, -OH, and -CH3, on the adsorption and thermal properties of GNS/paraffin (PA) composites. The results show that it forms a spherical structure after GNS absorbs in PA. The loading rate of the systems follows the order: GNS-COOH/PA > GNS-NH2/PA > GNS-OH/PA > GNS-CH3/PA > GNS/PA, which is determined by the adsorption free energy. Due to the functionalization, the latent heats of the composites undergo a significant change and the thermal conductivities are significantly enhanced. GNS-OH/PA exhibits the most substantial improvement with the latent heat increasing by 11.2% and the thermal conductivity increasing by 107.4% compared to GNS/PA. The study demonstrates the potential of these composites for energy storage applications, highlighting the improved performance through functionalization. [ABSTRACT FROM AUTHOR]

Pr doped La 2 Zr 2 O 7 (LPZ) TBCs have been deposited by electron beam physical vapor deposition. This work concentrates on the thermophysical properties and microstructure evolution of LPZ/YSZ duplex TBCs before and after thermal cyclic so as to probe into the merit and the application feasibility. The thermal expansion, thermal conductivity and phase structure have been measured and analyzed in comparison to other classical TBCs materials. Typical feathery microstructure and intra-columnar gaps did not provide desired thermal cyclic counts for LPZ/YSZ TBCs. Two principal categories of degradation mechanism limited the cyclic lifetime. The first principal degradation mode is the pulverization of LPZ after thermal cyclic due to the Pr rare earth elements modification in lanthanum Zirconates. Pr instability created the pulverization degradation mode instead of spalling. The second degradation mode is the cracks extension paralleled to interface inside TGO due to the brittle spinel generated by excessive oxidation. This study of thermal properties and degradation mechanism might offer thought and inspiration for other advanced TBCs. [ABSTRACT FROM AUTHOR]

By applying the high-entropy strategy, one can develop stable mixed oxide by populating a single sublattice with many distinct cations. Two kinds of rare-earth high-entropy hexaaluminates (La 1/5 Nd 1/5 Sm 1/5 Eu 1/5 Gd 1/5)MAl 11 O 19 (M = Mg and Zn) were successfully synthesized, and their mechanical and thermal properties were analyzed. We highlight that the Zn-containing sample displays a significant increase in fracture toughness (2.48 MPa m1/2) and a decrease in thermal conductivity (1500 °C, 1.2 W m−1 K−1) as compared to the Mg-containing sample. The diffusion of fine grains in platelet-like grains observed only in the Zn-containing sample is considered to be responsible for its outstanding mechanical properties. This work demonstrates the excellent thermal-mechanical properties of the Zn-containing sample and indicates the promising use of high-entropy hexaaluminate in the aerospace field acting as thermal barrier coating materials. [ABSTRACT FROM AUTHOR]

In this study, the thermal characterisation of natural rock samples from Zimbabwe for low‐temperature industrial thermal energy storage (TES) applications was carried out. Thermal stability, specific heat capacity, thermal diffusivity, thermal conductivity and density were determined. Variations in these parameters were evaluated and their impact on thermal storage performance was analysed. Basalt and dolerite samples from different locations were found to have average specific heat capacities of 826 and 853 J/kg K, respectively, at room temperature. Insignificant variations were observed with differences of 3.4% for basalt and 1.7% for dolerite samples. Also, negligible differences of 0.3% and 0.7% in densities for rocks of the same type but of different origins were obtained for basalt and dolerite samples, respectively. However, significant variations in thermal diffusivity of all the igneous and metamorphic samples were observed with quartzite rock exhibiting the highest value of 2.1 × 10−6 m2/s, while the values for the other samples range from 0.9 × 10−6 to 1.6 × 10−6 m2/s. This implies that the thermal efficiency of sensible TES systems that use different or the same rock types from different locations can be significantly high to be overlooked. Thermo‐gravimetric analysis results revealed that the rock samples studied have good thermal stability for low‐temperature heat storage applications. [ABSTRACT FROM AUTHOR]

The use of iron waste in concrete is now of considerable importance, mainly because of the benefits for the environment and for improving the strength of concrete. The increased and unused of this industrial byproducts represents a challenge for the environment and human health. This article experimentally explores the influence of utilizing iron powder waste and iron fibers in concrete in order to enhance the thermophysical properties of concrete and reduce the environmental impact resulting from iron waste. The aim of this work is to study the thermophysical properties (thermal conductivity, volumetric heat capacity, thermal diffusivity and thermal effusivity) of concrete with waste iron powder and iron fibers for application in building construction. The iron powder waste was added to the concrete with different percentages of 0%, 5%, 15%, 20% and 25% respectively as a partial replacement of sand. The iron fibers were added with mix proportions including 1.0%, 1.5%, 2.0% and 2.5% by volume of concrete, and in two different arrangements, uniform and random. The thermal conductivity and the volumetric heat capacity of these samples were measured experimentally in the dry state at ambient temperature (20 °C), and at 28 days of age. The effect of the integration of iron powder and fiber on thermal properties was analysed. [ABSTRACT FROM AUTHOR]

In the realm of thermal interface materials (TIMs), high thermal conductivity and low density are key for effective thermal management and are particularly vital due to the growing compactness and lightweight nature of electronic devices. Efficient directional arrangement is a key control strategy to significantly improve thermal conductivity and comprehensive properties of thermal interface materials. In the present work, drawing inspiration from natural leaf and branch structures, a simple-to-implement approach for fabricating oriented thermal conductivity composites is introduced. Utilizing carbon fibers (CFs), known for their ultra-high thermal conductivity, as branches, this design ensures robust thermal conduction channels. Concurrently, boron nitride (BN) platelets, characterized by their substantial in-plane thermal conductivity, act as leaves. These components not only support the branches but also serve as junctions in the thermal conduction network. Remarkably, the composite achieves a thermal conductivity of 11.08 W/(m·K) with just an 11.1 wt% CF content and a 1.86 g/cm3 density. This study expands the methodologies for achieving highly oriented configurations of fibrous and flake materials, which provides a new design idea for preparing high-thermal conductivity and low-density thermal interface materials. [ABSTRACT FROM AUTHOR]

Building materials are responsible for significant CO2 emissions and energy consumption, both during production and operational phases. Earth as a building material offers a valuable alternative to conventional materials, as it naturally provides high hygrothermal comfort and air quality even with passive conditioning systems. However, disadvantages related to high density, conductivity, and wall thickness prevent its effective inclusion in the mainstream. This research explores enhancing the thermophysical properties of compressed earth blocks (CEBs) by using locally sourced natural materials. The study is framed in the Portuguese context and the natural materials involved are wheat straw (WS) as a by-product of wheat harvesting, cork granules (CGs) from bottle caps, and ground olive stone (GOSs) residues from olive oil production. Blocks were produced with different mixtures of these materials and the thermal response was examined in a hot box apparatus. Best results include a 20 and 26% reduction in thermal conductivity for mixtures with 5v.% CG and 10v.% GOS, respectively, and an associated reduction in bulk density of 3.8 and 5.4%. The proposed approach therefore proves to be effective in improving the key thermophysical characteristics of CEBs. The article includes a comparative analysis of the experimental data from this study with those from the literature. The study contributes to the growing knowledge of sustainable materials, providing insights for researchers and practitioners looking for innovative solutions for low-carbon and energy-efficient materials. [ABSTRACT FROM AUTHOR]

The article describes the achievement and values of the mechanical and thermal characteristics of composite materials with sludge matrix and the insertion of agricultural waste, focusing on the compressive strength and thermal conductivity coefficient. These two characteristics are essential for civil engineering applications. The compressive strength and thermal conductivity coefficient depend significantly on the insertion concentration in the composite material: the compression strength decreases, and the thermal conductivity coefficient increases as the insertion concentration increases. For mud matrix composites and seed husk insert, the compressive strength varies between 0.375 MPa and 2.292 MPa. In the case of sawdust insert, the compressive strength varies between 0.149 MPa and 2.292MPa. These values indicate that composite materials are at the lower limit of strength of building materials, but have good insulating properties due to the low coefficient of thermal conductivity. These features recommend using them for supporting walls in light, floor-free buildings, and for partitions with good thermal insulation properties. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) using phase change materials (PCMs) is one of the potential solutions for stockpiling thermal energy and utilizing it for different applications, which results in effective energy usage. The main drawback of organic PCMs in practical applications is poor heat transfer due to low thermal conductivity (TC). Therefore, investigations into nano-enhanced PCMs are being explored to improve their thermophysical properties. In this work, the various thermophysical characteristics of nano-enhanced lauryl alcohol as a PCM were investigated using carbon-based and metallic nanoparticles. The results indicated that the addition of nanoparticles improved its thermal properties and affected other physical properties, such as viscosity. The latent heat was degraded with the addition of nanoparticles. The results revealed that by adding MWCNTs and CuO nanoparticles, a maximum of 82.6% and 49.6% improvement in TC was achieved, respectively. The maximum drop in latent heat during melting and freezing for the PCM with MWCNTs was about 10.1% and 9.3%, respectively, whereas for the PCM with CuO, they were about 11% and 10.3%, respectively. The lowest supercooling for the PCM with MWCNTs and CuO nanoparticles was 8.6 and 8.3 °C, respectively. The present work confirms that nano-enhanced PCMs can be a potential material for storing thermal energy for various applications. [ABSTRACT FROM AUTHOR]

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The fight against climate change has delineated new objectives, among which one of the most crucial is the replacement of high-energy-intensity materials in the construction sector with more sustainable and thermally efficient alternatives to reduce indirect emissions. Consequently, the thermal properties of materials assume fundamental importance. In this regard, the large-scale use of earth represents a promising option, not only due to its widespread availability but especially for its minimal embodied energy. However, to enhance its durability, it is necessary to stabilize the mixtures of raw materials. This study analyzes experimental systems based on earth stabilized with bio-based polymers to evaluate their thermal properties and how these vary depending on the selected mix-design. The experimental measurements showed thermal properties comparable to conventional materials. As expected, thermal conductivity increases when porosity decreases. The minimum value is equal to 0.216 W/m·K vs. a porosity of 43.5%, while the maximum is 0.507 W/m·K vs. a porosity of 33.2%. However, the data obtained for individual systems may vary depending on the topological characteristics, which were analyzed through a model for granular materials. The modeling suggests correlations between microstructures and thermal behaviour, which can be useful to develop tools for the mix-design procedure. [ABSTRACT FROM AUTHOR]

The thermodynamic and kinetic simulations based on the re-assessment of the thermodynamic and kinetic database of the Ni-Ti-Cu system were employed to predict the phenomena of mechanical alloying, spark plasma sintering and thermal properties of the intriguing Ni-Ti-Cu system. Thermodynamic calculations are presented for the stable and unstable phases of NiTiCu materials and support a correlation with the evolving microstructure during the technological process. Also, the thermal conductivity, the thermal diffusivity and the specific heat of spark plasma sintered and aged Cu-alloyed NiTi-based shape memory alloys (NiTiCu) with two compositions, Ni45Ti50Cu5 and Ni40Ti50Cu10, are evaluated and the influence of mechanical alloying and precipitates on thermal properties is discussed. Measurements of these thermal properties were carried out from 25 °C up to 175 °C using the laser flash method, as well as differential scanning calorimetry. The thermal hysteresis of the 20 mm diameter samples was between 8.8 and 24.5 °C. The observed T0 temperatures from DSC experimental transformation features are in reasonable accordance with the thermodynamic predictions. The determined k values are between 20.04 and 26.87 W/m K and in agreement with the literature results. Moreover, this paper can provide some suggestions for the preparation of NiTiCu shape memory alloys and their applications. [ABSTRACT FROM AUTHOR]

The current paper has the objective of exploring the thermophysical properties (TPPs) of single walled carbon nanotube (SWCNT) nanofluids (NFs) for heat transfer applications. The effect of dispersing the nanotubes in conventional heat transfer fluids (HTFs) has been investigated. Carbon nanotubes (CNTs) have exceptionally high thermal conductivities. Using the effective medium theory, density, specific heat, thermal conductivity, and viscosity has been evaluated as functions of volume fractions. The base fluids considered in this work are water, ethylene glycol, engine oil, and kerosene oil as these are the commonly used HTFs for industrial applications. Theoretical predictions from this study show an increase in density, thermal conductivity, and viscosity with volume fraction while there is a decrease in specific heat with volume fraction. The effect of the aspect ratio (AR) of CNTs on the thermal conductivity of NF is also investigated. For low volume fractions of SWCNT, the thermal conductivity has been found to increase with AR. Further, this study has been extended for a real‐world application of heat transfer using SWCNT. In this paper, a numerical investigation of heat transfer in a square enclosure with differentially heated vertical walls, filled with SWCNT‐water NF under natural convection is carried out. Due to low concentrations of SWCNT in water, single phase flow is assumed. Velocity and temperature distributions are obtained as solutions to the energy and Navier–Stoke's equations. A comparison of the temperature and velocity profile has been represented by simulating the system over a range of Rayleigh numbers. [ABSTRACT FROM AUTHOR]

Heat transport in two dimensions is fundamentally different from that in three dimensions. As a consequence, the thermal properties of 2D materials are of great interest, from both scientific and application points of view. However, few techniques are available for the accurate determination of these properties in ultrathin suspended membranes. Here, we present an optomechanical methodology for extracting the thermal expansion coefficient, specific heat, and thermal conductivity of ultrathin membranes made of 2H-TaS2, FePS3, polycrystalline silicon, MoS2, and WSe2. The obtained thermal properties are in good agreement with the values reported in the literature for the same materials. Our work provides an optomechanical method for determining the thermal properties of ultrathin suspended membranes, which are difficult to measure otherwise. It provides a route toward improving our understanding of heat transport in the 2D limit and facilitates engineering of 2D structures with a dedicated thermal performance. [ABSTRACT FROM AUTHOR]

Deep coaxial borehole heat exchanger (DCBHE) is a promising kind of ground heat exchanger for geothermal exploitation. In this study, effects of stratified ground thermophysical properties (GTP) are considered, and then an improved semi-analytical heat transfer model is developed and validated to analyze the DCBHE performance. Then, influences of stratified GTP on the DCBHE performance are investigated. Finally, thermal response test (TRT) of DCBHE with stratified GTP is simulated by a numerical model, and by using the simulated TRT data, the improved model is combined with a parameter estimation method to identify the effective values of GTP, which are compared with actual values. The results show that stratified ground thermal conductivities have an important influence on the DCBHE performance, and that stratified volumetric heat capacities of ground have a small influence on the DCBHE performance. The DCBHE performances based on the effective values and actual values of GTP match well with each other for different cases and geothermal gradients, indicating that for stratified thermal conductivities or volumetric heat capacities of ground, the effective GTP are reliable and can be used for accurately predicting the DCBHE performance. [ABSTRACT FROM AUTHOR]

Since the fusing process in electrophotography has a significant impact not only on printing quality but also on machine internal temperature and toner blocking on outlet tray, accurate paper temperature prediction for various types of papers is essential, especially in the production printing. To develop the thermophysical model of fusing process to predict the paper temperature after the fusing process, thermal properties such as thermal conductivity, specific heat, and thermal contact resistance of several types of papers are necessary. However, paper is composed of complex fiber, surface coating, filler, and moisture, making it difficult to measure thermophysical properties of paper accurately. This work developed a machine learning (ML) model that can predict the thermophysical properties of paper based on a conventionally used 1D thermal network model of the fusing process and experiment results. The thermophysical properties of each paper obtained by ML and the thermophysical properties obtained by the conventional method were input to the thermal network model to predict the paper temperature after the fusing process and compared with the measured paper temperatures of the experiment. The results showed that the paper temperature was predicted with higher accuracy by using thermophysical properties obtained by ML than that by the conventional method. Although the method for predicting paper temperature by using only ML had been proposed, it had the disadvantage of requiring a large number of training experiments. In contrast, this method trained under the conditions of one fusing temperature and two printing speeds, and was able to predict under five fusing temperatures and four printing speeds. [ABSTRACT FROM AUTHOR]

This article proposes a modeling method for C/C-ZrC composite materials. According to the superposition of Gaussian random field, the original gray model is obtained, and the threshold segmentation method is used to generate the C-ZrC inclusion model. Finally, the fiber structure is added to construct the microstructure of the three-phase plain weave composite. The reconstructed inclusions can meet the randomness of the shape and have a uniform distribution. Using an algorithm based on asymptotic homogenization and finite element method, the equivalent thermal conductivity prediction of the microstructure finite element model was carried out, and the influence of component volume fraction on material thermal properties was explored. The sensitivity of model parameters was studied, including the size, mesh sensitivity, Gaussian complexity, and correlation length of the RVE model, and the optimal calculation model was selected. The results indicate that the volume fraction of the inclusion phase has a significant impact on the equivalent thermal conductivity of the material. As the volume fraction of carbon fiber and ZrC increases, the equivalent thermal conductivity tensor gradually decreases. This model can be used to explore the impact of material microstructure on the results, and numerical simulations have studied the relationship between structure and performance, providing the possibility of designing microstructure based on performance. [ABSTRACT FROM AUTHOR]

Using thermal storage materials with excellent thermal properties in the energy utilization system enables efficient use of renewable energy sources. Organic phase change materials (PCMs) have the advantages of high heat storage density, no corrosion, and low cost, but low thermal conductivity and insufficient heat transfer capacity have always been the bottlenecks in their application. In this paper, melamine foam@ reduction graphene oxide (MF@rGO) and carbon foam@ reduction graphene oxide (CF@rGO) composite foams with double carbon networks were prepared by self-assembly method and further employed in 1-octadecinal (OD) PCMs. The microstructure, chemical composition, phase change behavior, thermal conductivity, and photothermal conversion performance of MF@rGO/OD and CF@rGO/OD were studied in detail using SEM, FTIR, Raman DSC, and LFA. The melting and solidification enthalpies of CF@rGO/OD composite PCMs were 208.3 J/g and 191.4 J/g, respectively, its thermal conductivity increased to 1.54 W/m·K, which is 6.42 times that of pure OD. The porous structure and high thermal conductivity of the double carbon network substantially enhance the efficiency of energy storage and release in composite PCMs. CF@rGO/OD composite PCMs have excellent heat storage performance and heat transfer capacity, and a wide range of application prospects in the fields of low-temperature solar heat storage, precision instrument temperature control, and intelligent buildings. [ABSTRACT FROM AUTHOR]

In Part 1 of this study, we investigated the macrokinetic parameters and phase formation mechanism in the combustion front of Zr–Nb–B mixtures. In the second part, we produced consolidated samples of solid solutions NbB 2 -(0.100%)ZrB 2 by hot pressing the combustion-derived powders at 1900 °C. By measuring the crystallographic parameters, mechanical and thermophysical properties of the produced bulk samples, we obtained valuable insights into the behavior of the solid solutions. Our results pave the way for the application-specific fine-tuning of the mechanical properties and thermal conductivity of diboride solid solutions in the Zr–Nb–B system for ultra-high temperature applications. Our findings have significant implications for the development of advanced materials with outstanding performance in extreme environments. [ABSTRACT FROM AUTHOR]

Hypereutectic Al-x(1.75Fe-1.25Ni) (x=1,2,4,6) alloys were designed and prepared by gravity casting in the present study. Both the microstructure and the thermophysical properties were investigated. The microstructure was significantly transformed from the eutectic phases to the coarse primary phases with the increase in alloying elements. The result of thermal analysis indicated that the solidification behaviors were modified by the increase in alloying elements, which was ascribed to the generation of different phases. The thermal conductivity and thermal expansion properties were also related to the alloy composition. From the variation in the ratio of thermal conductivity/electrical conductivity, it could be inferred the effective medium of heat conduction was changing, which decreased thermal conductivity due to the introduced defects that hindered the transport of electrons and low efficiency heat conducting medium of intermetallic. Meantime, the formation of bulk intermetallic with low thermal expansion coefficient and large volume fractions reduced effectively the thermal expansion of the alloy. The mathematical model was presented to quantify the influence of alloy content on thermophysical properties. [ABSTRACT FROM AUTHOR]

This article presents three photothermal methods dedicated to the measurement of the thermal properties of chalcogenide alloys, used as a central element in the new generations of non-volatile memory. These materials have two phases, amorphous and crystalline, possessing a sharp contrast in their electrical and thermal properties. In the crystalline phase, the properties also change very significantly with temperature. The control of the temperature of the samples, the choice of transducers, and the time or frequency characteristic values of the photothermal excitation are thoroughly discussed. Each photothermal technique is described from the experimental point of view as well as from the inverse method, performed to identify the parameters of interest. The identified thermal properties mainly concern the thermal conductivity and the thermal resistance at the interfaces between the phase-change materials and the materials in contact as encountered in the production of the microelectronic memory device. Assessing various photothermal techniques, the study suggests that pulsed photothermal radiometry is the most effective method for sensitive high-temperature measurements of thermal properties of the phase-change materials. [ABSTRACT FROM AUTHOR]

Thermal properties of rocks are of great importance not only for geothermal projects. The focus of petrophysical data presented here is laid mainly on volcanic rocks. Thermal properties include not only thermal conductivity but also heat production and heat capacity. A full range of dataset and analysis out of it is presented here. The target of this study is to deliver new insights in the thermal properties of volcanic rocks of Austria. The focus is laid on thermal conductivity—understanding of influencing factors and correlations with other properties, like compressional wave velocity, electrical resistivity or radiogenic heat production. Therefore, a set of data from various volcanic rocks of Austria is presented, analysed in detail and new correlations are presented. The correlations can be further applied on logging data to derive thermal properties in the field. These improved correlations and further interpretations can help in planning geothermal projects and can improve the output of simulations because of the better input data. [ABSTRACT FROM AUTHOR]

This research paper focuses on investigating the thermal conductivity behavior of polymer matrix composite materials, specifically those composed of PSU and BaTiO3, both experimentally and numerically. The thermal conductivity of composites has been studied using a variety of theoretical and semi-empirical methods. However, in cases where the filler concentration is minimal, these models provide a superior estimate. To numerically resolve the thermal heat transfer for an elementary cell, the finite element method is employed in this study. The impact of contact resistance, barium titanate percentage, and quenching temperature on the composite's effective thermal conductivity and dynamic behavior is given consideration. The results demonstrate that the suggested numerical model is in good agreement with experimental measurements as well as Hatta–Taya and Hashin–Shtrikman's analytical models. The results provide significant insight into the thermal conductivity behavior of composites, which can inform the development of more effective thermal management solutions for composite materials. Effective thermal management is critical for the successful application of polymer matrix composite materials in various engineering applications. Thermal conductivity is a key factor in thermal management and is influenced by factors such as the concentration of filler particles, their shape, size, and distribution, and the matrix material's properties. [ABSTRACT FROM AUTHOR]

This paper presents research on the thermophysical properties of an LNG-conveying corrugated cryogenic hose during the precooling process. A numerical model consisting of the turbulent model with enhanced wall treatment and the Volume of Fluid method is established to simulate the cryogenic multiphase flow, along with the energy equation to capture the thermal conduction and convection process. In addition to the analysis of physical phenomena under a specific precooling working condition, parametric studies on the effects of inlet LNG velocity and initial hose temperature on the cooling rate, boiling regime, and structural temperature gradients are carried out. The simulations successfully capture boiling regime transition and discover its significance on the cooling rate. Correlations of structural temperature gradient with the assessed parameters are identified. The findings of this work serve to enhance understanding of the corrugated hose precooling thermophysics in order to guide safer and more efficient industrial operations. [ABSTRACT FROM AUTHOR]

Five kinds of multi-component entropy-stabilized oxide ceramics were prepared by a solid-state reaction method for thermal barrier coatings, namely La0.125Y0.125Yb0.125Gd0.125Zr0.5O1.75 (LaYYbGdZr), Y0.125Yb0.125Gd0.125Ta0.125Zr0.5O1.875 (YYbGdTaZr), La0.1Y0.1Yb0.1Gd0.1Ta0.1Zr0.5O1.85 (LaYYbGdTaZr), Y0.125Yb0.125Gd0.125Ta0.125Hf0.25Zr0.25O1.875 (YYbGdTaHfZr), and La0.1Y0.1Yb0.1Gd0.1Ta0.1Hf0.25Zr0.25O1.85 (LaYYbGdTaHfZr). Many properties of the materials were studied, such as their microscopic morphology, crystal structure, thermophysical properties, and ablation resistance. The results show that the oxide ceramics synthesized in this paper have a uniform single-phase defect fluorite structure, and can still maintain this structure after high-temperature treatment at 1500 °C. The YYbGdTaHfZr coatings had the lowest thermal conductivity (0.61~0.89 W·m–1·K–1), which was much lower than that of YSZ. The ceramic blocks also exhibited excellent thermal expansion properties. The thermal expansion coefficient of LaYYbGdTaZr could reach 11.09 × 10−6 K−1 (1400 °C), which was slightly higher than that of 8YSZ (11.0 × 10−6 K−1). The antioxidant ablation results proved that the YYbGdTaHfZr coating showed the best heat-insulating property. All the results showed that the YYbGdTaHfZr coating is a promising thermal barrier coating. [ABSTRACT FROM AUTHOR]

h-BN is a two-dimensional ceramic material with a lamellar structure, known for its typical orientation characteristics on mechanical and thermal properties. By optimizing the size and arrangement of h-BN grains in the matrix, the anisotropic characteristics of h-BN ceramics can be fully utilized to obtain ceramic materials with high thermal conductivity or high strength. In order to study the effect of grain orientation distribution on the mechanical and thermal properties of materials, the index of orientation distribution (IOP) was used to quantitatively characterize the orientation degree of h-BN grains and analyzed the effect of h-BN grain size on material properties. The results show when the initial h-BN size is 13.50 μm, the ceramic has the highest orientation degree/-507, and the mechanical and thermal properties show obvious anisotropy. While the related properties of BN-YAG ceramics varies significantly with the decrease of initial h-BN grain size. [ABSTRACT FROM AUTHOR]

Thermoelectric conversion may take a significant share in future energy technologies. Oxide‐based thermoelectric composite ceramics attract attention for promising routes for control of electrical and thermal conductivity for enhanced thermoelectric performance. However, the variability of the composite properties responsible for the thermoelectric performance, despite nominally identical preparation routes, is significant, and this cannot be explained without detailed studies of thermal transport at the local scale. Scanning thermal microscopy (SThM) is a scanning probe microscopy method providing access to local thermal properties of materials down to length scales below 100 nm. To date, realistic quantitative SThM is shown mostly for topographically very smooth materials. Here, methods for SThM imaging of bulk ceramic samples with relatively rough surfaces are demonstrated. "Jumping mode" SThM (JM‐SThM), which serves to preserve the probe integrity while imaging rough surfaces, is developed and applied. Experiments with real thermoelectric ceramics show that the JM‐SThM can be used for meaningful quantitative imaging. Quantitative imaging is performed with the help of calibrated finite‐elements model of the SThM probe. The modeling reveals non‐negligible effects associated with the distributed nature of the resistive SThM probes used; corrections need to be made depending on probe‐sample contact thermal resistance and probe current frequency. [ABSTRACT FROM AUTHOR]

InI single crystals are a promising room temperature detector material for X-rays and γ-rays. To improve crystal growth of the material by simulations, knowledge of thermophysical properties is essential, and since InI is orthorhombic, the anisotropy has to be taken into account. The temperature-dependent thermophysical properties have been measured for InI, including the anisotropic thermal expansion, specific heat, and the thermal diffusivity in the b direction. The anisotropic thermal expansion coefficients, determined by X-ray diffraction, were α11 = 1.03 × 10–5 K−1, α22 = 3.77 × 10–5 K−1, and α33 = 6.26 × 10–5 K−1. The specific heat, measured by DSC, was 0.226 J·g−1·K−1 at 335 K, with a temperature dependence of 9.582 × 10–5 J·g−1·K−2. In the course of the X-ray diffraction and DSC measurements, it could also be shown that supposed phase changes, reported in older literature, are actually not phase changes but oxidation effects. The thermal diffusivity in the b direction, measured by the Xenon Flash method, was 0.288 × 10–6 m2·s−1 at RT, decreasing to 0.253 × 10–6 m2·s−1 at 450 K. In addition, the volume increase upon melting and the thermal expansion of the melt have been determined. [ABSTRACT FROM AUTHOR]

The surrounding (backfill) materials around the underground power cable systems are essential for dissipating the heat away from it, during the exertion phases. The heat dissipation restrains the thermal instability and risk of progressive drying of the backfill materials, thus reducing the thermal stress on the power cable. Thermal instability indicates the reduction in thermal properties (conductivity or diffusivity) due to the migration of moisture because of heat accumulation. Thus, the backfill materials should have adequate thermal properties and water retention capacity to transfer the heat from the heat source to the surrounding area with minimal moisture migration. The bentonite has high water retention capacity, but low thermal conductivity, whereas sand/fly ash exhibits low water retention and has higher thermal conductivity than bentonite. The addition of bentonite promotes the water holding capacity and thermophysical properties of sand and fly ash. Therefore, this study presents the thermal properties of backfill materials, bentonite–fly ash (B–F) and bentonite–sand (B–S), at varying weight-percent of sand and fly ash with bentonite. Various compositions of the mixtures were compacted to varying dry densities, and water contents and thermal properties variation of backfill materials were measured using a dual thermal needle probe 'KD2 Pro' at room temperature. The study deals with the systematic evaluation of the volumetric specific heat capacity, thermal conductivity, and diffusivity of backfill materials against varying dry density and water content. The threshold water content (TWC) has been determined from the thermal diffusivity–water content variation curve, and it has correlated with plastic limit (PL) and optimum moisture content (OMC). Thereafter, the efficacies of two thermal conductivity prediction models have also been evaluated statistically with respect to experimental results. [ABSTRACT FROM AUTHOR]

The absorption of heat by rocks is accompanied by an increase in the kinetic energy of molecules and atoms and is recorded by a change in rock temperature. The thermal properties of rocks characterize the ability to transfer and absorb heat and change their size when the temperature rises. The main thermal properties of rocks are thermal conductivity, heat capacity, linear thermal expansion, and thermal volumetric expansion. In this paper, the influence of temperature effects on the thermal properties of reservoirs – the coefficient of temperature conductivity, specific heat capacity, and thermal conductivity is studied using the samples of oilsaturated reservoirs from the good number 19Bp of the Upper Uplift of Sotnikovsky deposit. The dependence of the thermal properties of the core material on temperature was revealed using a number of laboratory experiments. The results of these studies contribute to improving the reliability of data on the relationship of thermal properties with other physical properties of oilsaturated reservoirs and can be used to improve the efficiency of the development of fields of superviscous oil. [ABSTRACT FROM AUTHOR]

Feijoa has a high nutraceutical and agro-industrial potential, an attractive opportunity for Colombia to enter new markets with innovative products. However, there is little knowledge about its behavior and requirements for its proper industrial processing. The studies of thermophysical and sorption properties are fundamental for analyzing and optimizing the different unit operations, evaluation, and product quality control. This study aimed to determine and mathematically model the physical, thermal, and water desorption properties of feijoa pulp in the physiological ripening stage. The desorption isotherms were determined using the gravimetric method, based on saturated salts’ solutions to create atmospheres of controlled relative humidity (RH, %), in this case, at temperatures (T) of 8°C, 23°C, and 38°C and water activities (aw) between 0.07 and 0.98. From the isotherms model that best fits the experimental data, the isosteric heat of sorption (Qs), differential entropy (ΔSdiff), and Gibbs free energy (ΔG) were calculated. The density (ρ), thermal conductivity (k), and specific heat capacity (cp) properties were determined and modeled at different moisture contents (H: 75%, 80%, 85%, and 90%) in the temperature range (T) 20 to 80°C, using the pycnometer method, concentric cylinder method, and differential scanning spectrophotometry (DSC), respectively. The desorption isotherms of the feijoa pulp were type III with equilibrium moisture contents (Xe) between 0.1246 and 5.5135 kg/kg (dry basis, d.b.), a monolayer moisture content of 0.2 kg/kg (d.b.); and spontaneity of the sorption phenomenon. Both cp and k depended more on H than on T; while ρ showed an equal relationship with both factors; these behaviors are characteristic of high humidity foods. The mathematical models obtained in this study are a valuable contribution for the food industry for an effective agro-industrialization, use, and added value of feijoa pulp through the design, control, and optimization of processes and equipment that involve the transfer of heat and matter.

Minimal processing consists in eliminating inedible parts of agricultural products, through cutting, reducing them to smaller portions, ready for immediate consumption or subsequent preparation. Despite the practicality, this resource is responsible for the first physical alterations in the tissues of food, contributing to its perishability. However, cooling of minimally processed products increases their shelf life. Designing refrigerators and calculating the costs of cooling require that the thermophysical properties of the product be known, making it possible to describe its cooling kinetics. The objective of this study was to present a methodology that includes experimental data and two computer programs for determining these properties referring to cylindrical pieces of cassava. A solver with the solution of the two‐dimensional diffusion equation was created for the direct problem, assuming the boundary condition of the third kind. For the inverse problem, an experimental data set of temperature in the center of the cassava pieces during cooling, the solver, and LS Optimizer software were used. The values obtained for thermophysical properties were consistent with those reported in the literature, while the cooling simulation was consistent with the experimental data, with χ2 = 1.7588 and R2 = 0.9992. Practical Applications: The main contribution of this article is to present a methodology to determine thermophysical properties of agricultural products, including the uncertainties of these properties, during their cooling. This is a transient process, involving an interval of temperatures, and not one constant temperature, within which thermal properties are usually determined. With the information obtained for the thermal properties of cassava pieces, one can design an efficient refrigerator for the product and reliably calculate the cost for cooling the product during its minimal processing. [ABSTRACT FROM AUTHOR]

Chloride molten salts have become a potential heat storage material for the design of a new generation of concentrating solar power (CSP) (>700 °C) due to its abundant reserves and low cost. The difficulty of measuring the high-temperature thermal properties of chlorides can be effectively solved by using molecular dynamics simulation. However, it is challenging to get the thermophysical properties of multi-component molten salts containing CaCl2 due to the lack of Born–Mayer–Huggins (BMH) potential parameters of CaCl2. Through comparative analysis of the structure and thermal properties of CaCl2, including density and thermal conductivity, a set of Born–Mayer–Huggins (BMH) potential parameters of CaCl2 named SP2 is determined in this study. The density, specific heat capacity, and thermal conductivity of nine eutectic molten salts are simulated, including NaCl-CaCl2, KCl-CaCl2, NaCl-CaCl2-MgCl2, and NaCl-CaCl2-KCl, and the simulation results are found to be in good agreement with the experimental results. It is also found that the SP2 parameters are able to predict the thermal properties and structure of molten multicomponent chlorides including calcium. [ABSTRACT FROM AUTHOR]

In this paper, the procedure of finding the coefficients of an equation to describe the thermal conductivity of refrigerants low in global warming potential (GWP) is transformed into a multi-objective optimization problem by constructing a multi-objective mathematical model based on the Pareto approach. For the first time, the NSGAII algorithm was used to describe a thermophysical property such as thermal conductivity. The algorithm was applied to improve the performance of existing equations. Two objective functions were optimized by using the NSGAII algorithm. The average absolute relative deviation was minimized, while the coefficient of determination was maximized. After the minimization process, the optimal solution located on the Pareto frontier was chosen through a comparative analysis between ten selection methods available in the literature. The procedure generated a new set of coefficients of the studied equation that decreased its average absolute relative deviation by 0.24%, resulting in better performance over the entire database and for fluids with a high number of points. Finally, the system model was compared with existing literature models to evaluate its suitability for predicting the thermal conductivity of low-GWP refrigerants. [ABSTRACT FROM AUTHOR]

Ionanofluids (INF) are combinations of ionic liquid (IL) and nanoparticles (NP) with superior thermophysical properties. In the present study, measurement of thermophysical profile of IL, 1-ethyl-3-methylimidazolium chloride ([EMiM]Cl) in which Al2O3 NPs are dispersed were undertaken in the temperature range of 303.15–333.15 K. INFs were prepared by dispersing Al2O3 NPs in different mass concentrations of 0.5, 1.0, 2.5, 5.0, and 10%. The results showed that specific heat and thermal conductivity increase with both concentration and temperature. In contrast, the viscosity and density increase with concentration and decrease with temperature rise. The maximum INF thermal conductivity and viscosity enhancements were 21.9% and 77.6% for a mass concentration of 10% compared to IL at 333.15 K and 303.15 K. Electrical conductivity decreases with NP addition and increases linearly with an increment in temperature. Based on the measured results, a correlation for the specific heat, thermal conductivity, and viscosity of INF was proposed. Further, the heat transfer performance of studied INF is theoretically estimated based on the experimental thermophysical properties. Finally, for high-temperature applications methylimidazolium chloride-based INFs can be used as an efficient candidate as primary heat transfer fluid. [ABSTRACT FROM AUTHOR]

In this study, the temperature dependence of the carbon/polyamide 410 composite's heat capacity, thermal expansion, density, and thermal conductivity was investigated. The results demonstrated that the specific heat capacity of the C/PA410 composite increases with temperature, with major transitions observed at the glass transition (Tg) and melting (Tm) temperatures. Due to the presence of fibers, the CTE values in the fiber direction of C/PA410 specimens were one order of magnitude smaller than in the transverse direction. The density measurements reveal that as temperature rises, volume increases, causing density to decrease. The heat diffusivity of the C/PA410 composite was measured using the laser flash technique, which was then used to calculate thermal conductivity. The results show that the average thermal conductivity in the fiber direction increases linearly with temperature, while in the transverse direction it increases linearly with temperature up to 50 °C and then becomes constant between 50 °C and 100 °C. [ABSTRACT FROM AUTHOR]

A novel, high‐entropy, perovskite‐structured, solid solution La(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic was successfully synthesized via high‐temperature solid‐state reaction. The crystal structure, microstructure, infrared emissivity, and thermophysical properties were investigated. The experimental results indicated that La(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 exhibited an infrared emissivity as high as.92 in the near‐infrared region of.76–2.50 μm. The thermal conductivity was 1.38–1.72 W m−1 K−1 in the temperature range of 25–1200°C. [ABSTRACT FROM AUTHOR]

In recent years, the interest with niobium alloys has been increasingly focusing on high-stress applications. This work shows the study of Cu-25wt.%Fe-25 wt.%Nb composite sintered by spark plasma at 700, 750, and 800 °C, under constant uniaxial pressure of 35 MPa for 3 min, evaluated for use as bushings. The scanning electron microscopy results showed regions rich in Nb and α-Fe embedded in a γ-Cu matrix, forming a solid solution of Fe-Nb suggesting the occurrence of a sintering process by Cu liquid phase and precipitation of an ε-phase Fe2Nb Laves. The relative density, mechanical and thermophysical properties were also evaluated. The alloy sintered at 800 °C showed hardness around 81 HB, low porosity, low porosity, yield strength 168 ± 4 MPa, modulus of elasticity 47 ± 4 GPa, and relative density 7.9% higher than the alloy prepared at 700 °C. The values of thermal conductivity obtained were above 70 Wm−1K−1, superior to SAE 65, indicating a possible material for application on bushings. [ABSTRACT FROM AUTHOR]

Aiming at the development of thermal environmental barrier coatings (TEBCs) material, the factor of grain size is introduced into the high-entropy rare-earth disilicate for the first time. The (Yb 0.2 Tm 0.2 Lu 0.2 Sc 0.2 Er 0.2) 2 Si 2 O 7 with smaller grain size was prepared by one-step pressureless sintering method. Results of thermal conductivity and coefficient of thermal expansion (CTE) reveal that thermal conductivity of (Yb 0.2 Tm 0.2 Lu 0.2 Sc 0.2 Er 0.2) 2 Si 2 O 7 bulk material is lower than that all existing EBCs and even most TBCs and potential TEBCs material, which is 0.686 W m−1 °C−1 at 1300 °C. Excellent thermophysical properties indicate that designed (Yb 0.2 Tm 0.2 Lu 0.2 Sc 0.2 Er 0.2) 2 Si 2 O 7 with small grain size can be used as a promising TEBCs material. • It is the first time to introduce the grain size into the thermal conductivity of high-entropy rare earth silicate materials. • The prepared (Yb 0.2 Tm 0.2 Lu 0.2 Sc 0.2 Er 0.2) 2 Si 2 O 7 has very low thermal conductivity than all existing EBCs materials. • (Yb 0.2 Tm 0.2 Lu 0.2 Sc 0.2 Er 0.2) 2 Si 2 O 7 with small grain size has excellent thermophysical properties and is a candidate for TEBCs. [ABSTRACT FROM AUTHOR]

Molten salt is widely utilized as high-temperature heat transfer and storage medium. Firstly, the molecular dynamics and potential function of molten salt is summarized and analyzed in this work. Buckingham potential is more suitable for nitrate and fluoride molten salts, while BMH potential is better suited for carbonate and chloride molten salts. Secondly, the transport and thermophysical properties of molten salt and molten salt nanofluids are analyzed and summarized. The increase of Li + concentration leads to higher specific heat capacity and thermal conductivity, and it increases simulation error. Increasing K + concentration reduces specific heat capacity error but increases calculation error for other thermal properties. Carbonate simulations exhibit relatively small errors with good agreement with experimental data. Adding nanoparticles to molten salt is an effective method to enhance molten salt thermal physical performance. Future research directions in the field of molecular dynamics of molten salt encompass investigating the impact of nanofluids on molecular dynamics, mitigating simulation errors, exploring corrosion characteristics through molecular dynamics simulations. Large-sized interface model and long-term scale are more effective for joint experimental and theoretical results according to the machine learning accelerated molecular dynamics research. More combinatorial properties such as corrosion characteristics can be explored through molecular dynamics simulations, providing a new basis for molten salt application. • Molecular dynamic studies on thermal physical properties of molten salt and its nanofluids are summarized and analyzed. • The molecular dynamics potential function and transport properties of molten salt are analyzed. • The machine learning coupled with molecular dynamics could provide strategies for further optimizing molten salt thermal properties. [ABSTRACT FROM AUTHOR]

Molten salt phase change materials (MSPCMs) provide strong support for the long-term and stable operation of new energy systems. This study focuses on LiNO 3 (high latent heat, low melting temperature), NaNO 3 (an important component in solar salts), and binary eutectic nitrate (LiNaNO 3). The aim is to explore eutectic nitrate that matches lower working temperature requirements by eutectic reaction. The other aim is to enhance the specific heat and thermal conductivity of nitrates by adding nanoparticles (NPs) with different microstructures. The NPs include multi-walled carbon nanotubes (MWCNT), graphene nanoplatelets (GNP), AlN, BN, and SiC. The distribution patterns of nitrate molecules near NPs were investigated under the influence of interaction strength through molecular dynamics. The enhancement of thermal transport is decided by phonon vibrations, interface thermal resistance, and heat pathway. NPs can significantly weaken the melting enthalpy and limit the enhancement of thermal conductivity by disrupting the eutectic microstructure of LiNaNO 3 , which is different from the mechanism of NPs' action on unitary nitrates. MWCNTs exhibit the most significant enhancement in thermal conductivity and specific heat of nitrates, which is due to the diffusion of nitrate molecules in the MWCNT. The in-plane phonon vibrations of GNP contribute slightly to the thermal transport in the vertical plane direction, resulting in limited enhancement of thermal transport. Therefore, we propose principles for selecting NPs doped into eutectic salts, which should ensure that the interaction strength between NPs and both unitary nitrates is similar or that their microscopic structure can maintain the integrity of the eutectic structure. [Display omitted] • The thermal conductivity and specific heat of nitrates were experimentally enhanced with maximum rate of 237.72 %, 95.67 %. • NPs weaken the melting enthalpy of LiNO 3 and NaNO 3 by binding them on the surfaces of NPs. • For LiNaNO 3 , the disruption of eutectic structure by NP will weaken enthalpy and limit enhancement on thermal conductivity. • The diffusion of nitrate molecules inside the structure of MWCNT leads to diverse impact on thermal properties of nitrates. • A principle for selecting NPs doped into eutectic salts is proposed to more effectively enhance heat storage efficiency. [ABSTRACT FROM AUTHOR]

Phonons and related processes govern the thermal properties of materials. They can be excited externally using light, heat, mechanical energy, etc. This article aims to elucidate the methodology used in studying thermal properties, specifically employing temperature-dependent Raman spectroscopy. However, unique challenges arise when applying these techniques to low-dimensional materials. We summarize theoretical and experimental studies highlighting the significance of phonon hydrodynamics—a phenomenon typically observed only at low temperatures in bulk materials, but now found at room temperature in 2D materials like graphene. This discovery calls for caution when utilizing temperature-dependent Raman spectroscopy-based techniques, such as the optothermal Raman method, which has been extensively employed to experimentally determine the thermal conductivity of graphene. Moreover, temperature-dependent Raman spectroscopy remains a valuable tool for investigating phonon anharmonicity, a key factor governing phonon transport and decay processes in a wide array of emerging 2D materials and their heterostructures. • Phonons and related processes govern the thermal properties of materials. • Thermal conduction in graphene, carbon nanotubes and related materials are reviewed. • The methodology for studying thermal properties, specifically employing temperature-dependent Raman spectroscopy is reviewed for graphene and emerging 2D materials. [ABSTRACT FROM AUTHOR]

Resin-reinforced Ag sintering materials represent a promising solution for die-attach applications in high-power devices requiring enhanced reliability and heat dissipation. However, the presence of resin and intricate microstructure poses challenges to its thermal performance, and improvement strategies remain unclear. This work utilizes 3D FIB-SEM nanotomography to reconstruct the microstructure of this material under various process conditions. The analysis reveals that, even with an Ag volume fraction as low as 47.3%, Ag particles form a robust 3D network. Geometric tortuosity quantifies the effect of different sintering conditions on the Ag particle network in all spatial directions. Effective thermal conductivity is simulated based on realistic microstructure models. Results show a significant negative correlation between tortuosity and effective thermal conductivity. Increasing sintering temperature in Model B notably reduces tortuosity and enhances effective thermal conductivity. Sensitivity analysis underscores the dominant role of Ag volume fraction in regulating effective thermal conductivity. Finally, transient thermal impedance measurement of this material as a thin die-attach layer in actual high-power devices demonstrated its application potential. This article strives to explore the relationship between process, microstructure, and thermal properties of this material to provide a reference for further development. • 3D FIB-SEM nanotomography meticulously reconstructed and distinguished the microstructure under different process conditions. • Effective thermal conductivity is simulated from a realistic microstructure model using a high-performance cluster. • Tortuosities intuitively reflects the influence of process conditions on the microstructure and thermal properties. • Sensitivity analysis shows the dominant role of Ag volume fraction on the effective thermal conductivity. [ABSTRACT FROM AUTHOR]

With the widespread utilization of transparent conductive oxides (TCO) in various electronic devices, it is beneficial to revisit the fundamentals of heat conduction to formulate a comprehensive physical understanding for thermal properties of TCOs with the aim of improving the thermal design of electronic devices. For degenerate polycrystalline TCO films, both free electrons and phonons act as heat carriers, where free electron contribution can be calculated based on the Wiedemann-Franz law.Interestingly, the phonon thermal conductivity remains almost constant for degenerated polycrystalline TCO films with different dopant concentrations, suggesting the existence of dopant-induced minimum phonon thermal conductivity. For degenerate amorphous TCO film, free electrons act as heat carriers along the conduction path formed by the orbital overlap of cations, which also obey the Wiedemann-Franz law. Moreover, the atomic vibration contribution to thermal conductivity almost keeps unchanged for amorphous TCO films deposited under different conditions, indicating the existence of a minimum thermal conductivity caused by the scattering of vibrational mode due to structural randomness appeared in the bond angle. We anticipate that these fundamental understanding can provide a guide for the discovery of TCO materials with optimized thermal properties. [ABSTRACT FROM AUTHOR]

In the development for advanced nuclear fuels for LWRs, the focus has traditionally centered on a limited array of materials like doped-UO 2 , UN, and U 3 Si 2 , leaving the vast majority of potential uranium compounds unexplored. To expand the search and expedite the discovery of advanced LWR fuels, we developed a machine learning (ML) classification model dedicated to identifying uranium compounds with excellent thermal conductivity. However, the model's predictive accuracy and the feasibility of such an ML-assisted approach to advanced nuclear fuel discovery have yet to be empirically validated. Therefore, this study examines the thermal properties of two uranium compounds, UFe 3 B 2 and USiNi, that are predicted to outperform UO 2 at high temperatures. Our findings confirm that the model precisely predicted the thermal conductivities of both compounds, thereby adding credibility to its reliability. However, the experimental process unveiled several challenges, such as the fabrication of single-phase USiNi and microcrack-free UFe 3 B 2 samples, which our ML model, focused primarily on thermal conductivity, could not anticipate. These challenges underscore the need for a more comprehensive ML framework that considers the intricacies of sample fabrication. This advancement is crucial for the more efficient development of practical, accident-tolerant, advanced LWR fuels. • Validated ML model's predictions for uranium compounds' thermal conductivity. • First report of UFe 3 B 2 and USiNi thermophysical and mechanical properties. • Identified unforeseen experimental challenges beyond ML prediction. • Emphasized need for comprehensive ML framework for advanced nuclear fuel development. [ABSTRACT FROM AUTHOR]

Nanofluids are identified as advanced working fluids in the solar energy conversion field with superior heat transfer characteristics. This research work introduces carbon-based diamond nanomaterial and Therminol®55 oil-based nanofluids for implementation in a concentrated photovoltaic/thermal (CPV/T) solar collector. This study focuses on the experimental formulation, characterization of properties, and performance evaluation of the nanofluid-based CPV/T system. Thermo-physical (thermal conductivity, viscosity, and rheology), optical (UV-vis and FT-IR), and stability (Zeta potential) properties of the formulated nanofluids are characterized at 0.001–0.1 wt.% concentrations of dispersed particles using experimental assessment. The maximum photo-thermal energy conversion efficiency of the base fluid is improved by 120.80% at 0.1 wt.%. The thermal conductivity of pure oil is increased by adding the nanomaterial. The highest enhancement of 73.39% is observed for the TH-55/DP nanofluid. Furthermore, dynamic viscosity decreased dramatically across the temperature range studied (20–100 °C), and the nanofluid exhibited dominant Newtonian flow behavior, with viscosity remaining nearly constant up to a shear rate of 100 s−1. Numerical simulations of the nanofluid-operated CPV/T collector have disclosed substantial improvements. At a concentrated solar irradiance of 5000 W/m2 and an optimal flow rate of 3 L/min, the highest thermal and electrical energy conversion efficiency enhancements are found to be 11 and 1.8%, respectively. [ABSTRACT FROM AUTHOR]