Search

Investigating how the thermal transport properties of iron change under extremely high pressure and temperature conditions, such as those found in the Earth's core, is a major experimental challenge. Over the past decade, there has been a great deal of discussion and debate surrounding the thermal conductivity of the iron-based Earth's core and its thermal evolution. One reason for this may be the variability in the experimentally obtained thermal conductivity of iron at high pressures and temperatures. In this study, we present the experimental results of measuring the thermal conductivity of hexagonal-closed-pack (hcp) iron over a wide pressure-temperature range up to 176 GPa and 2900 K using the pulsed light heating thermoreflectance technique in a laser-heated diamond anvil cell. Our findings indicate that the temperature derivative of the thermal conductivity of hcp iron undergoes a change from negative to positive above 74 GPa, potentially making hcp iron highly conductive at conditions similar to those observed in the Earth's core. This observation represents a notable example of a phenomenon where pressure appears to influence the sign of the temperature derivative of the thermal conductivity of an isostructural metal. [ABSTRACT FROM AUTHOR]

Improvement of thermal conductivity of polymer present a key to realizing efficient thermal transport used for various applications remains a long-standing challenge. In fact, we investigate the effect of TBPO-capped CdSe nanoparticles concentration on Thermal properties in Poly (3-hexylthiophene) (P3HT) thin films. We employed photothermal deflection technique PTD for thermal conductivity and diffusivity determination. Thermal conductivity and diffusivity were determined by fitting theoretical amplitude and phase of PTD signal to the experimental ones. We remark that thermal diffusivity D decreased for 3.52– 0.23 m2/s as function of CdSe nanoparticles concentration (NPs) in P3HT. However, thermal conductivity K increases for 1.78– 3.18 W/m.K as respect of CdSe nanoparticles concentration in P3HT. High thermal conductivity and lower thermal diffusivity are obtained for 40% TBPO-capped CdSe concentration in P3HT sample. [ABSTRACT FROM AUTHOR]

The increasing demand for high-performance materials has led to the development of natural fiber composites as an alternative to synthetic fiber composites. However, the low thermal conductivity of natural fibers limits their use in advanced applications. In this study, we have developed polyaniline-coated natural fiber composites to enhance their thermal properties. The methodology of this study involves the preparation of natural fiber composites using polyaniline-coated natural fibers as a reinforcement and a bio-based resin as a matrix. The composites were then coated with polyaniline, which was synthesized through chemical oxidation of aniline monomer. The coated composites were characterized using various analytical techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to evaluate their structural, morphological, and thermal properties. The materials used in this study were natural fibers, bio-based resin, aniline monomer, ammonium persulfate, and hydrochloric acid. The gap identification of this study is the low thermal conductivity of natural fiber composites, which limits their application in advanced fields such as aerospace, automotive, and electronics. The problem identification is the lack of a cost-effective and eco-friendly method to enhance the thermal properties of natural fiber composites. The results of this study showed that the polyaniline-coated natural fiber composites exhibited enhanced thermal conductivity compared to the uncoated composites. The improvement in the properties of the composites was attributed to the high conductivity of polyaniline and its ability to form a continuous conductive network throughout the composite matrix. The development of polyaniline-coated natural fiber composites provides a cost-effective and eco-friendly approach to enhance the thermal properties of natural fiber composites. This approach has the potential to expand the use of natural fiber composites in advanced applications, leading to a sustainable and greener future. [ABSTRACT FROM AUTHOR]

This work explored whether partial cellulose bioconversion with fungal mycelium can improve the properties of cellulose fibre-based materials. We demonstrate an efficient approach for producing cellulose-mycelium composites utilizing several cellulosic matrices and show that these materials can match fossil-derived polymeric foams on water contact angle, compression strength, thermal conductivity, and exhibit selective antimicrobial properties. Fossil-based polymeric foams commonly used for these applications are highly carbon positive, persist in soils and water, and are challenging to recycle. Bio-based alternatives to synthetic polymers could reduce GHG emissions, store carbon, and decrease plastic pollution. We explored several fungal species for the biofabrication of three kinds of cellulosic-mycelium composites and characterized the resulting materials for density, microstructure, compression strength, thermal conductivity, water contact angle, and antimicrobial properties. Foamed mycelium-cellulose samples had low densities (0.058 – 0.077 g/cm3), low thermal conductivity (0.03 – 0.06 W/m∙K at + 10 °C), and high water contact angle (118 – 140°). The recovery from compression of all samples was not affected by the mycelium addition and varied between 70 and 85%. In addition, an antiviral property against active MS-2 viruses was observed. These findings show that the biofabrication process using mycelium can provide water repellency and antiviral properties to cellulose foam materials while retaining their low density and good thermal insulation properties. [ABSTRACT FROM AUTHOR]

In this study, a technique to estimate the thermal properties of a suspended copper wire using the 3ω method was proposed and its operation was demonstrated. This approach used a digital multimeter with a large measurement buffer to implement a procedure in which an appropriate window function and a discrete Fourier transform (DFT) were applied. This significantly reduces the noise level to a few nV, especially in the lower-frequency regions (less than 1 Hz), even if a longer measurement time is required. The third-harmonic voltage signal containing the thermal properties information for the 3ω method was clearly observed with a high signal-to-noise (S/N) ratio, and the thermal conductivity and diffusivity were estimated from 60 K to 300 K from the current frequency dependence of the third-harmonic voltage. The thermal conductivities of the copper wire were determined to be 423.0 and 385.9 W/mK at 100 and 300 K, respectively. Specific heat was calculated from thermal conductivity and diffusivity, and the Debye temperature was estimated to be 346 K from the temperature dependence of the specific heat. These values were in good agreement with previous research. Measurement of thermal properties using a digital lock-in amplifier with identical configuration resulted in overestimation of thermal conductivity in entire temperature regions owing to a low S/N ratio throughout the analysis of the DFT. The technique based on DFT with a window function is therefore more reliable for detecting the third-harmonic voltage in the low-frequency region of less than 1 Hz because it obtains a high S/N ratio. [ABSTRACT FROM AUTHOR]

The thermal and nonlinear optical (NLO) properties of alizaringelb R solution are investigated experimentally and numerically. The thermal conductivity, K, of alizaringelb R solution is calculated by constructing a device and found to decrease with the increase in absolute temperature. The change in refractive index, Δ n, of alizaringleb R solution and its nonlinear index of refraction (NLIR), n2, are estimated via diffraction patterns (DPs) under irradiation with a 473 nm cw laser beam. As high as 4.73 × 10–3 and 4.81 × 10–11 m2/W of Δ n and n2 are determined. The collapse of DPs phenomenon through the deformation of the resulted DPs seen to occur. The resulted DPs are numerically calculated via the use of a mathematical model that is solved using the diffraction integral. [ABSTRACT FROM AUTHOR]

Ternary half-Heusler (HH) alloys are under intense investigations recently towards achieving high thermoelectric (TE) figure-of-merit (ZT). Of particular interest is the ZrNiPb-based HH alloy, where an optimal value of ZT ~ 0.7 at 773 K has been achieved by co-doping Sn and Bi at Pb site. In this work, we identify an excellent ZT of 1.3 in ZrNi1+xPb0.38Sn0.6Bi0.02 (x = 0.03, at 773 K) composite alloy. This is achieved by synergistic modulation of electronic as well as thermal properties via introduction of minor phase of full-Heusler (FH) in the HH matrix through compositional tuning approach. These Ni-rich ZrNi1+xPb0.38Sn0.6Bi0.02 (0 ≤ x ≤ 0.07) alloys were synthesized via energy efficient and time-curbed techniques that involved Arc melting followed by consolidation via spark plasma sintering. These alloys were characterized by XRD and SEM, which show formation of nanocomposites comprising of HH matrix phase and FH secondary minor phases. Enhancement in ZT is mainly attributed to a synchronized increase in power factor (~42%) and ~25% decrease in its thermal conductivity. Here, TE compatibility factor (S) was also calculated for all samples. The value of |S| ~ 2.7 V−1 (at 773 K) is observed for x = 0.03, which is ~17% higher than bare HH composition (x = 0.0). The theoretically calculated TE device efficiency of best-performing sample ZrNi1.03Pb0.38Sn0.6Bi0.02 is estimated to be η ~ 13.6%. Our results imply that deliberately controlled fine tuning in compositions of HH compounds through compositional tuning approach would lead to novel off-stoichiometric HH phases with enhanced ZT value for efficient TE device fabrication. [ABSTRACT FROM AUTHOR]

Thermal conductivity of moulding sands is very poorly known. In addition, the study of thermal conductivity variation of moulding sand as a function of its properties is a crucial step in the prediction of moulding defects. So, this study investigates the effects of moisture content, compactibility and permeability of green sand on its thermal conductivity variation, with a specific focus on the combination of bentonite, sand and water for thermal characterization of the transient hot-bridge (THB) method. Three levels of active clay content were selected: 8.1%, 8.98% and 10.03%. For each level of active clay, different mixes were made by varying the amount of added water. Compactibility, permeability and thermal conductivity tests were carried out for each combination of active clay and moisture contents. The experimental results show that thermal conductivity increases with water content and compactibility for different active clay contents, whereas thermal conductivity decreases with permeability, and this variation is highly significant especially for 8.07% of active clay content. [ABSTRACT FROM AUTHOR]

In this paper, a novel composite phase change material (CPCM) is prepared with inorganic PCM through impregnation and dispersion method which can be used for thermal management applications. Inorganic PCMs have high latent heat and good thermal conductivity and are non-flammable, but there exist leakage (shape stability) and corrosion problems. To overcome these issues, a porous structured material is impregnated with the inorganic PCM (disodium hydrogen orthophosphate dodecahydrate). The CPCM is prepared by loading various wt% of expanded graphite and boron nitride nanoparticles with the PCM, and characterization is performed to find the thermal properties and stability. The findings from FTIR and XRD analyses validate both the chemical compatibility and crystalline nature of the samples. DSC thermographs reveal the CPCM5 sample has a latent heat value of 168.05 J/g during the heating process, an encapsulation efficiency of 78.8% and a thermal conductivity of 4.69 W/mK. The thermal stability and resistance to corrosion of the composite samples are also enhanced. The best composite PCM sample is then selected, and subsequently, the thermal performance of the heat sink is experimentally investigated. The thermal performance of rectangular cavity heat sink filled with CPCM5 is the highest for various power sources and temperatures with a maximum enhancement ratio of 6.57. [ABSTRACT FROM AUTHOR]

The advancement of implantable biomedical devices (IMDs) hinges on the development of biocompatible solid-state electrolytes with outstanding electrochemical performance, safety, and reliability for flexible solid-state supercapacitors. This study focuses on the development of gel polymer electrolytes (GPEs) using polyvinyl alcohol (PVA) and potassium chloride (KCl). The GPEs obtained were subjected to comprehensive characterization using a diverse range of techniques to evaluate their spectral features, morphological properties, thermal and mechanical performance, biocompatibility, ionic conductivity, and cyclic stability. What distinguishes our research is its comprehensive exploration of the profound impact of varying PVA molecular weights and PVA/KCl weight ratios on the ionic conductivity and thermal characteristics of these gels. Notably, we observed a decrease in ionic conductivity with increasing PVA molecular weight, whereas an increase in salt concentration under the same molecular weight led to higher ionic conductivity. In particular, the optimal gel electrolyte with a molecular weight (Mw) of 195,000 g/mol and a PVA/KCl weight ratio of 1/2 demonstrated a promising ionic conductivity of 3.48 ± 0.25 mS/cm. Even after 5000 cycles, it retained 88% of its initial specific capacitance. Our findings reveal that the GPEs exhibit remarkable mechanical robustness alongside unparalleled ionic conductivity, characterized by minimal interfacial resistance. Moreover, these gel electrolytes exhibit remarkable biocompatibility, evident in a cell viability test where 72.3% of cells remained unaffected after a 72-h exposure to PVA/KCl. These findings present a promising avenue towards the fabrication of stable and high-performance biocompatible gel polymer electrolytes which can be used in solid-state supercapacitors, thereby laying the foundation for their integration into flexible, safer, and wearable bio-electronics. [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]

Context: Traditional conductive adhesives based on epoxy resin system often encounter problems such as high brittleness and low heat resistance. Therefore, it is particularly important to improve the thermal and mechanical properties of the conductive adhesive. In this study, the effects of SWCNT-Ag and SWCNT fillers on the thermal properties of DGEBA/DETA/Ag conductive adhesive system were studied by using molecular dynamics to construct different cross-linking models. The final results show that the addition of SWCNT and SWCNT-Ag can significantly improve the thermal properties of the conductive adhesive. However, the nanosilver particles on the surface of SWCNT-Ag act as a bridge for the connection between SWCNT and Ag in the conductive adhesive. Therefore, SWCNT-Ag has a more positive impact on the thermal properties of DGEBA/DETA/Ag conductive adhesive system. Methods: In this paper, the influence of SWCNT-Ag on the thermal properties of traditional DGEBA/DETA/Ag conductive adhesive system was studied by using Materials Studio software. The volume shrinkage, glass transition temperature, thermal expansion coefficient, and thermal conductivity of the material were calculated based on COMPASS force field. The thermal conductivity is calculated by using reverse non-equilibrium molecular dynamics method. Finally, it is found that SWCNT-Ag has a positive effect on the thermal properties of the conductive adhesive system by comparing several groups of calculation data. [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]

Apparent thermal conductivity of soil (λ) as a function of soil water content (θ), i.e., λ(θ) is needed to determine the heat flow in soil. The function of λ(θ) can be used in heat and water flow models for simplicity. The objective of this study was to develop a sigmoidal model based on logistic equation for entire range of soil water contents and a wide range of soil textures that can be used in simulation of heat and water flow in respected modes. Further, performance of the developed sigmoidal model along with two other models in literature was evaluated. In the proposed sigmoidal model, the constants of this model are estimated based on empirical multivariate equations by using soil sand content and bulk density. The sigmoidal model was validated with good accuracy for a wide range of soil textures, as the relationship between the measured and predicted λ showed slope and intercept values of nearly 1.0 and 0.0, respectively. Comparison of the results obtained by sigmoidal model with those obtained from Johansen and Lu et al. models indicated that, the sigmoidal model was superior to the other two models in prediction of λ for a wide range of soil textures and soil water contents. Furthermore, comparison with a recently proposed model by Xiong et al. indicated that our sigmoidal model is superior. Therefore, our developed sigmoidal model can be used in heat and water flow models to predict the soil temperature and heat flow. [ABSTRACT FROM AUTHOR]

γ-GeSe is a newly identified polymorph among group-IV monochalcogenides, characterized by a distinctive interatomic bonding configuration. Despite its promising applications in electrical and thermal domains, the experimental verification of its mechanical and thermal properties remains unreported. Here, we experimentally characterize the in-plane Young's modulus (E) and thermal conductivity () of γ-GeSe. The mechanical vibrational modes of freestanding γ-GeSe flakes are measured using optical interferometry. Nano-indentation via atomic force microscopy is also conducted to induce mechanical deformation and to extract the E. Comparison with finite-element simulations reveals that the E is 97.3 7.5 GPa as determined by optical interferometry and 109.4 13.5 GPa as established through the nano-indentation method. Additionally, optothermal Raman spectroscopy reveals that γ-GeSe has a lattice thermal conductivity of 2.3 0.4 Wm−1K−1 and a total thermal conductivity of 7.5 0.4 Wm−1K−1 in the in-plane direction at room temperature. The notably high ratio in γ-GeSe, compared to other layered materials, underscores its distinctive structural and dynamic characteristics. [ABSTRACT FROM AUTHOR]

SiO2f/SiO2 composites were prepared by compression molding and sintering using short-cut quartz fibers as reinforcement. The effects of fiber volume fraction (15%∼35%) on bulk density, apparent porosity, and mechanical and thermal properties of the composites were investigated. The results indicated that the samples with 25% fiber volume fraction had the best comprehensive performance, with an apparent porosity and compressive strength of 36% and 46.3 MPa, respectively. The flexural strength of the samples was 13.9 MPa, which represented a 90% increase compared to the samples without fibers. It was attributed to the occurrence of fiber debonding and fiber pull-out in the porous matrix. Meanwhile, the residual strength ratio of the samples after 20 thermal shocks was 74.8%. In addition, the average coefficient of thermal expansion was 0.95 × 10− 6/℃ at 300 ℃∼700 ℃ and the thermal conductivity was 0.388 W·m− 1·K− 1 at 800 °C. This approach can satisfy the requirements of low cost, fast preparation of SiO2f/SiO2 composites, which offers the prospect of its application in the integration of load-bearing and thermal insulation. [ABSTRACT FROM AUTHOR]

This study presents the preliminary outcomes of a methodology for the physical and mechanical characterization of various chestnut elements in different states of preservation. Strategizing conservation and retrofit interventions for timber is necessary, and to do this, it is necessary to establish an estimation of physical (transmissivity, thermal conductivity, humidity level, etc.) and mechanical properties (density, compressive or bending strength, etc.). This essential information is typically associated with timber defects, but there are lack of correlations. The primary objective is to establish correlations between thermal and density properties with the aim of preserving original assets. The investigation delves into the relationship between timber density and thermal properties through experimental non-destructive testing (NDT). Two NDTs were employed with the aim of correlating: penetrometric testing and active thermography investigations. The parametric study on the excitation period yielded valuable insights into the temporal dynamics of heat transfer within the timber, underscoring the significance of selecting appropriate excitation periods to capture precise thermal properties. Tabular data on relative humidity for salified, dried, and new samples provided a quantitative backdrop to these observations, unveiling the nuanced effects of humidity on the timber's thermal response. The results of this study are positioned to inform future conservation efforts by laying the groundwork for a comprehensive understanding of timber's mechanical properties. Particularly, the challenge lies in accurately estimating density, where surface tests are often less reliable than in-depth ones. Therefore, it is crucial to seek validation through other NDT tests, such as thermographic analysis and visual inspection, and hygrometric tests recognizing their importance in enhancing the reliability of density assessments. This approach will contribute to the development of more discerning preservation strategies. [ABSTRACT FROM AUTHOR]

Fe-25Mn-9Al-8Ni-1C-xTi (x = 0, 0.1, 0.2, 0.3, 0.4 wt.%) alloy was prepared by vacuum arc melting method, and the corresponding microstructure, tensile properties and thermal fatigue properties were studied. The results show that the Fe-25Mn-9Al-8Ni-1C-xTi alloy mainly consists of austenitic phase, ferrite phase and TiC phase. Ti element addition can significantly increase both the plasticity and tensile strength of the alloy. In particular, when Ti addition is 0.2%, the product of strength and ductility reached a maximum value of 25.09 GPa %. Compared with the alloy without Ti addition, its tensile strength and elongation increase 9.3% and 959%, respectively. Furthermore, Ti element can also improve the alloy thermal fatigue performance. The thermal fatigue performance of Fe-25Mn-9Al-8Ni-1C-0.2Ti is excellent with the crack length 1985 μm, which is reduced by 53.8% compared with Fe-25Mn-9Al-8Ni-1C alloy. Further research found that the formation of thermal fatigue cracks is mainly due to the difference in thermal expansion coefficient and thermal conductivity between austenite matrix, ferrite and TiC phase. It is easy to form oxidation corrosion micropores at the interface of these phases, which eventually become the source of fatigue. Meanwhile, the crack propagation modes of the series alloys are intergranular propagation, transgranular propagation and mixed propagation. [ABSTRACT FROM AUTHOR]

This experimental study aimed to investigate the potential control of microstructural-mineralogical characteristics on thermal properties and its relation with the deformational behaviour in mild to high temperature (25°–800°C) regime of coal-bearing sandstone from an underground coal mine fire region. Barakar sandstone from Jharia Coalfield, India, one of the world's largest underground coal mine fire regions, was chosen. The thermal parameters and their relations to the mineralogical, microstructural, and damage characteristics of Barakar sandstone have been discussed. Thermal conductivity (λ), thermal diffusivity (κ), and specific heat capacity (Cp) of heat-treated samples were determined using the transient plane source method. Additionally, detailed petrography, scanning electron microscopy, and electron probe micro-analyser were used to understand the thermal effect on mineralogy and microstructures. The deformational behaviour with elevated temperature was investigated through the universal testing machine. The obtained results suggest three characteristic temperature regimes: mild temperature regime (25°–300°C), transitional temperature regime (300º–500°C) and high temperature regime (500º–800°C). Moreover, prediction models for thermal properties have also been developed using multi-gene genetic programming (MGGP), considering physical properties as input parameters. In view of experimental constraints to determine the thermos-elastic properties of a rock due to tedious experimental processes, the proposed prediction models shall be very useful to indirectly estimate the thermal properties of sandstone rocks using easily determined physical parameters. The outcome of the present study may be useful to understand the subsidence induced by underground coalmine fire, which is a distressing issue in the Jharia region due to persistent coalmine fire. [ABSTRACT FROM AUTHOR]

Recent advances have shown the beneficial impact of adding nanoparticles to thermal oil. Diamond and boron nitride nanoparticles have superior thermal conductivity and excellent thermal and optical properties. In the current study, thermal conductivity, specific heat, and rheological behavior of diamond and boron nitride-based hybrid nanofluids in thermal oil are experimentally investigated for 0%, 0.2%, 0.4%, and 0.6% weight concentrations and a wide range of temperatures. The proportion between diamond and boron nitride utilized in the study is 1:1. A two-step method is applied to prepare stable hybrid nanofluids. The obtained data indicate that the hybrid nanofluids' thermal conductivity and specific heat enhance with increasing temperature and weight concentration. Almost 37.4% and 48.1% enhancement is observed in the thermal conductivity and specific heat, respectively, at 65 °C and 0.6% weight concentration. Thermal oil-based hybrid nanofluids display Newtonian behavior at low shear rates and an inverse relationship with temperature. Shear-thinning non-Newtonian behavior is observed at high shear rates and temperatures. A maximum increase in viscosity up to 22.0% is observed at 65 °C and 0.6% wt. concentration. The relative change indicates that all investigated properties have a significant impact, where the increasing trend of thermal conductivity and specific heat with increasing temperature and weight concentration of thermal oil-based hybrid nanofluids make them suitable for high-temperature heat transfer applications. [ABSTRACT FROM AUTHOR]

This paper describes the composites of silane cross-linked polyethylene (PEXb) mixed with four different fillers dedicated to improving thermal conductivity, such as multi-walled carbon nanotubes, graphite, boron nitride, and mineral filler. Using the mathematical modeling, the concentration of each filler was estimated to reach the value of 0.675 W m−1 K−1 suitable for the usage PEXb in the production of geothermal pipes. From tested fillers, all improve the thermal conductivity of pure PEXb; however, above the required value, only 28 mass% of boron nitride (0.937 W m−1 K−1). It was associated with its perfect dispersion and the highest gel content achieved, also resulting in the highest flexural modulus. Graphite at 5 mass% and mineral filler at 35 mass% allowed the thermal conductivity to equal 0.622 W m−1 K−1 and 0.624 W m−1 K−1, respectively, with a simultaneous medium effect on the mechanical properties. Carbon nanotubes increased PEX's conductivity to a small extent, due to their occurrence as agglomerates. [ABSTRACT FROM AUTHOR]

The effect of T4 and T6 treatment on the microstructures, precipitates, thermal expansion and thermal conductivity properties of Mg-2Nd-4Zn alloys was systemically investigated. The number of NdZn2 phase increased subjected to T6 treatment. The coherent relationship between the NdZn2 phase and Mg matrix was observed in the Mg-2Nd-4Zn alloys, which plays a great influence on improving the thermal expansion, thermal conductivity and mechanical properties of Mg-2Nd-4Zn alloys. The decrease in the coefficient of thermal expansion (CTE) and the thermal conductivity of Mg alloys were ascribed to the existence of solute atoms in alloys after the T4 treatment. It was also found that the T6-treated alloy has smaller area of the hysteresis loop, which has better thermal stability. Therefore, the high performance was mainly due to T6 treatment, the thermal conductivity of T6-treated Mg-2Nd-4Zn alloy is 124.4 K·m−1·K−1 at room temperature, and TYS of 235.5 MPa, CYS of 393.7 MPa, elongation of tension and compression are 31 and 27%, respectively. [ABSTRACT FROM AUTHOR]

The effect of defects on the thermal properties of Ψ-Graphene Nanotubes (Ψ-GNTs) is investigated in this study using Molecular Dynamics simulations. The results reveal that the thermal properties of Ψ-GNTs are profoundly impacted by the presence of defects. Specifically, a significant reduction in thermal conductivity is observed with increasing defect concentrations. This reduction is attributed to the scattering of phonons by the defects, which leads to increased phonon–phonon interactions and decreased thermal transport efficiency. Furthermore, the effect of temperature on the thermal properties of defective Ψ-GNTs is investigated. The findings demonstrate a nonlinear decrease in thermal conductivity with increasing temperature. [ABSTRACT FROM AUTHOR]

The most important thermal and rheological properties of water-based CaCO3/SiO2 dual hybrid nanofluid (DHNF) at overall volumetric concentrations of the nanoparticles from 0.1 to 0.5 and different volume fractions at temperatures of 15–60 °C have been studied. Prepared DHNFs consisted using SDS and ultrasonic homogenizer. Stability analysis of the DHNFs performed by changing ultrasonication time and power. The optimum consistency conditions and volume fractions of the nanoparticles determined for the prepared DHNFs. Specific heat capacity, thermal conductivity and resistivity, usual viscosity and density of the DHNFs studied, experimentally, compared with preexisting models, and finally, theoretical models with 99% precisions suggested. Maximum augmentation in thermal conductivity attained to 21.8% for 80:20 corresponding volume ratio and 0.5 vol% total concentration. At these conditions, maximum reduction in heat capacity occurred as 1.08%, and the greatest reduction in thermal resistivity got about 22.2% at 60 °C. Usual viscosity and density increased as 36.9 and 1.2%, respectively. [ABSTRACT FROM AUTHOR]

A novel composite phase change material, myristic acid (MA)/nano-titanium dioxide (nano-TiO2)/carbon additives, was synthesized via a melt blending method, in which MA serves as phase change material, nano-TiO2 acts as support material, and carbon additives are used as thermally conductive enhancer. A series of leakage tests have shown that MA/nano-TiO2 can maintain shape stability during the phase transition when the content of MA in MA/nano-TiO2 does not exceed 50 %. The FT-IR and XRD results demonstrated that there is no chemical reaction among the various components of the MA/nano-TiO2/carbon additive. When the content of MA is 50 %, the melting temperature of MA/nano-TiO2/carbon additives is about 54 °C and the melting enthalpy is about 80 J·g−1. When the content of all three carbon additives, multiwall carbon nanotubes, graphene, and expanded graphite, is 2.5 %, the corresponding thermal conductivity of MA/nano-TiO2/carbon additives is 0.532 W/(m·K), 1.128 W/(m·K), and 1.382 W/(m·K), respectively. The thermal conductivity of these three types of MA/nano-TiO2/additives is 1.23, 2.62, and 3.21 times that of MA/TiO2, respectively. Moreover, the decomposition temperature of these three types MA/nano-TiO2/carbon additives composites is around 245 °C. Therefore, the working ambient temperature of MA/nano-TiO2/additive composites should be lower than 245 °C. [ABSTRACT FROM AUTHOR]

The potential cooling solutions for the next generation are represented by nanofluids, offering several advantages for various technological applications. The intriguing realm of glycine-based acetone-based Al 2 O 3 nanofluids was explored in the present investigation, with meticulous attention to details given to scrutinizing their stability and thermophysical properties. The stability of the nanofluids was determined through a trifecta of analytical methods, namely visual inspection, UV absorbance measurement, and zeta potential analysis, all applied with caution. The results revealed that stability was observed for a duration of 3 days without glycine, and an impressive 6 week period was achieved when supplemented with the surfactant. The incorporation of glycine enhanced the stability of the colloidal suspension without compromising its thermophysical attributes. Furthermore, the study involved an in-depth examination of the density, viscosity, specific heat, and thermal conductivity of the prepared nanofluids, yielding interesting outcomes. The data showed a marked increase in nanofluid density, viscosity, and thermal conductivity with a corresponding rise in volume concentration, while specific heat exhibited a noticeable reduction. These significant observations were meticulously compared to various existing theoretical models and proposed correlations in the literature. The heat transfer performance of the nanofluid in the context of pulsating heat pipes was evaluated and the results proved riveting. The nanofluid demonstrated superior performance compared to the base fluid, confirming its remarkable efficacy. [ABSTRACT FROM AUTHOR]

We report the experimental and theoretical study of the diffraction patterns (DPs) and thermal properties of Sudan III. DPs are used in the calculation of the Sudan III nonlinear refractive index (NLRI), n 2 . As high as n 2 = 7.69 ×10-6 cm2/W is obtained. The study of the Sudan III thermal conductivity, TC, shows the reduction of the TC against the increase of the Sudan III temperature. The property, all-optical switching (AOS), is studied in details, both static and dynamic ones, using two, cw, visible, single mode laser beams of wavelengths 473 and 635 nm. [ABSTRACT FROM AUTHOR]

Graphite films are frequently used in the thermal interface materials (TIM) of thermal dissipation due to its high thermal conductivity. However, accurately measuring the thermal diffusivity of graphite films requires careful consideration of key parameters. In this study, four typical graphite films were analyzed to identify these parameters. The results revealed that pulse width was the most important parameter in accurately measuring thermal diffusivity. Specifically, when the pulse width was less than 1.8% of the half-heating time, thermal diffusivity measurements were more accurate. Conversely, when the pulse width exceeded 1.8% of the half-heating time, heating curves were affected, resulting in a gradual decrease in thermal diffusivity. Additionally, pulse voltage had little effect on thermal diffusivity measurements. These findings provide important guidance for accurately characterizing the thermal properties of graphite films and can inform the accurate measurement and development of efficient thermal interface materials. [ABSTRACT FROM AUTHOR]

This study focused on an important global issue containing both environmental pollution control and energy storage. Polyaniline has been utilized as a supporting material to load paraffin in order to form highly thermal conducting and shape-stable phase change material (PCM). Three different weight percentages (wt%), i.e., 10, 15, and 20 wt%, of polyaniline have been used to obtain shape-stable composite materials. The paraffin leakage of the prepared samples PPCM1, PPCM2, and PPCM3 has been examined by 500 thermal cycles in a hot air oven at 80 °C. Among three samples, the PPCM3 composite with 20 wt% of polyaniline in paraffin has shown excellent leakage-bearing properties with only ~ 0.06% leakage after 500 thermal cycles. Further, the chemical, structural, and morphological analyses of the PPCM3 composite have been carried out by FTIR, XRD, and FESEM. The thermal performance of the prepared sample has been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis, which revealed that the impregnation of polyaniline polymer has improved the thermal stability and thermal conductivity of paraffin with a small decrement in latent heat capacity of the PPCM3 composite. The latent heat of the composite decreased by 18.36% and thermal conductivity increased by ~ 65.45% for a 20 wt% concentration of polyaniline in paraffin with the maximum latent heat capacity. To check the thermal reliability of the formulated PPCM3 composite, the composite has been subjected to thermal cycling of 500 thermal cycles. With increased thermal conductivity, high latent heat capacity, good shape stability, excellent leakage-bearing capability, and improved thermal reliability, paraffin/polyaniline composite PCMs look promising for application in thermal energy storage areas. [ABSTRACT FROM AUTHOR]

In this study, new proton conducting membranes were prepared using poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole (PBI) and varying amounts of methylimidazoliumtriflate[MeIm/TfO], a protic ionic liquid, by the solution casting method. The thermal properties and conductivity of these membranes were investigated. The obtained parameters, such as high thermal stability (235–255°C) and the conductivity of 0.7–1.6 mS/cm at 145°C, indicate that PBI membranes doped with either MeIm/TfO or BuIm/TfO, which were previously studied by our group, are quite interesting for further investigation as potential electrolytes for PEMFCs. [ABSTRACT FROM AUTHOR]

As a nickel-based super alloy, Inconel 718 (In718) has gained attention in different industries due to its excellent mechanical behavior under elevated temperatures. Nevertheless, its low thermal conductivity limits its application in many fields, such as thermal energy conversion and heat dissipation. GRCop-84, in contrast, is a copper-based alloy with extremely high thermal conductivity. Making bi-metallic structures with GRCop-84 may expand the thermal-related applications of Inconel 718. In this study, we investigate the thermal properties of In718/GRCop-84 bi-metallic structures fabricated by the directed energy deposition (DED) technique with different process parameters of laser power and scanning velocity. The resulting microstructures were analyzed through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), while the frequency-domain thermoreflectance (FDTR) technique has been adopted to acquire the thermal properties. The melt pool thermal conductivities were 50 W/m K on single bead samples and 100 W/m K on single-layer pads, significantly lower than that of bulk GRCop-84. EDS analysis reveals large deviations from standard GRCop-84 compositions inside the melt pool. [ABSTRACT FROM AUTHOR]

Natural resource-driven approaches to bioengineering plastics are being developed to compete in the automobiles, power, and other sectors. Polytrimethylene terephthalate (PTT) is a particular of them, and it was chosen for the current investigation to build an advanced nanocomposite material. Using a twin-screw micro compounder, injection moulded PTT/Graphene-Oxide (GO)/Carboxyl functionalized Multiwall Carbon nanotube (f-MWCNT) hybrid nanocomposites were prepared. The impact of GO and f-MWCNT reinforcement on the composite's thermal and mechanical characteristics of hybrid nanocomposites was examined. GO was synthesized from the graphite powder by modified Hummer's method and MWCNTs were functionalized using the concentrated sulfuric acid (H2SO4) and nitric acid (HNO3) with a volume ratio of 3:1 in an ultrasonic bath at room temperature. In all formulations, the investigation was done at a constant filler amount of 2 wt%. To understand the chemical interaction between PTT and nanofiller, Raman spectroscopy was used and to examine the state of dispersion, scanning electron microscopy (SEM) was systematically analysed. In comparison to pristine PTT, the water absorption, tensile strength, flexural strength and impact strength of hybrid nanocomposites were improved marginally. It was also observed that GO has more prominent in increasing the mechanical properties of the hybrid and f-MWCNT in thermal properties. The 3-D geometrical bridge between GO (2-D) and f-MWCNT (1-D) made the hybrid more dispersible and effective for different applications. [ABSTRACT FROM AUTHOR]

In the present study, changes in thermal properties, microstructure and microhardness were investigated when 0.5, 1, 1.5 wt % Sb were added to Sn–1 wt % Ag–0.5 wt % Cu (SAC105) solder alloy system. The addition of Sb caused a significant improvement in microhardness while decreasing the melting temperature range, thermal conductivity and electrical conductivity. Addition of 0.5, 1, 1.5 wt % Sb to SAC105 alloy system decreased the thermal conductivity by 48% and electrical conductivity by 27%. The addition of Sb at the same rate increased the microhardness by 27%. [ABSTRACT FROM AUTHOR]

Polyimide-based composite films with high thermal conductivity, good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics fields. As one of the key technical challenges to be solved, interfacial compatibility between filler and matrix plays an important role for composite film. Herein, boron nitride was modified by grafting polyimide brushes via a two-step method, and a series of thermally conductive polyimide/boron nitride composite films were prepared. Both characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced, resulting in a significant reduction in defects and interfacial thermal resistance. The interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler surface. As a result, composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine filler. Tensile strength can reach up to 80 MPa even if the filler content is as high as 50 wt%. The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m−1·K−1, respectively. In addition, thermal and dielectric properties of composite films were also enhanced to some extent. The above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties. [ABSTRACT FROM AUTHOR]

With the rapid development of the electronics, communication, and energy industries, there is an increasing demand for flexible materials with high thermal conductivity and electrical insulation properties. Silicone rubber (SR) is widely used in various fields due to its excellent mechanical properties. However, its intrinsic low thermal conductivity requires the addition of thermally conductive fillers to enhance its thermal conductivity. Insulating thermally conductive composites are prepared by adding thermally conductive fillers such as boron nitride (BN) and graphite into a silicone rubber matrix. When BN is added as a single filler up to 20 wt%, the thermal conductivity of BN/SR reaches 0.526 W m−1 K−1, which is a 126% improvement compared to the SR matrix. When the total filler content is 20 wt%, and the ratio of BN to graphite is 1:1, the thermal conductivity of BN/graphite/SR composite is 0.685 W m−1 K−1. This represents a 194% and 30% increase in thermal conductivity compared to the SR matrix and BN/SR composite with the same filler content, respectively. On the cured silicone rubber substrate, the incremental cured BN/SR acts as an insulation coating. This allows for a significant reduction in the electrical conductivity of the composite without the use of adhesives, while preserving the thermal conductivity. Moreover, the interface formed through incremental curing retains high tensile and compressive strength. [ABSTRACT FROM AUTHOR]

This work investigates the physical–thermal properties of nanofluids made from graphene powder, propylene glycol, and water. Propylene glycol and water were mixed in the following ratios to make nanofluids: 100:0, 75:25, and 50:50. Graphene was added at 0.25 and 0.5% of the mixture's volume to the three base fluids. Nanofluids' viscosity, density, thermal conductivity, and specific heat are studied. After mixing with graphene nanopowder, critical fluids increased in density and thermal conductivity. Essential fluids showed these advantages. When the temperature was elevated, viscosity and specific heat decreased. Despite constant temperatures, this was the case. Increasing graphene concentration increases thermal conductivity by 10–16%. The viscosity of nanofluids with graphene nanopowder is less affected by temperature. As temperature rises, nanofluid density falls. Temperature and density are inversely related; thus, this makes sense. Adding graphene to propylene glycol at different concentrations increased its specific heat by 8–14%, depending on the concentration. [ABSTRACT FROM AUTHOR]

In this work, composite phase change materials (CPCM) containing myristic acid (MA), bentonite, and graphene were prepared by melt blending method, where MA is phase change material (PCM), bentonite is supporting material, and graphene is thermal conductivity enhancer. The CPCM containing 50 wt% MA can still maintain the stable morphology during phase change process. The chemical structure, crystal structure and microstructures of CPCM were examined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. Differential scanning calorimeter (DSC) analysis indicate that the melting enthalpy is 94 to 97 J·g−1. Thermogravimetric analysis (TGA) demonstrates good thermal stability of the CPCM. Thermal conductivity of the CPCM with 3 wt% graphene can reach 1.09 W⋅(m⋅K)−1, that is 2.37 times that of MA/bentonite. Experimental results indicate that the CPCM have significant improvement with regard to stability and thermal conductivity as compared to the pristine PCM. Moreover, the CPCM still remain good thermal properties after undergoing 100 thermal cycles. [ABSTRACT FROM AUTHOR]

As an advanced amorphous material, sp3 amorphous carbon exhibits exceptional mechanical, thermal and optical properties, but it cannot be synthesized by using traditional processes such as fast cooling liquid carbon and an efficient strategy to tune its structure and properties is thus lacking. Here we show that the structures and physical properties of sp3 amorphous carbon can be modified by changing the concentration of carbon pentagons and hexagons in the fullerene precursor from the topological transition point of view. A highly transparent, nearly pure sp3−hybridized bulk amorphous carbon, which inherits more hexagonal-diamond structural feature, was synthesized from C70 at high pressure and high temperature. This amorphous carbon shows more hexagonal-diamond-like clusters, stronger short/medium-range structural order, and significantly enhanced thermal conductivity (36.3 ± 2.2 W m−1 K−1) and higher hardness (109.8 ± 5.6 GPa) compared to that synthesized from C60. Our work thus provides a valid strategy to modify the microstructure of amorphous solids for desirable properties. sp3 amorphous carbon exhibits exceptional mechanical, thermal, and optical properties, but cannot be synthesized using traditional processes. Here authors report a nearly pure sp3−hybridized amorphous carbon synthesized from C70 which shows more short/medium-range order and enhanced thermal conductivity compared to C60. [ABSTRACT FROM AUTHOR]

Highlights: A core-sheath structured coaxial composite fiber with highly aligned and densely stacked boron nitride nanosheets arrangements in the sheath was successfully fabricated. The coaxial fibers have an ultrahigh axial Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m−1 K−1, and tensile strength of 192.5 MPa. The coaxial fibers exhibit intensively potential applications in the wearable thermal management textile. Hexagonal boron nitride nanosheets (BNNSs) exhibit remarkable thermal and dielectric properties. However, their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride, thereby limiting their performance in applications such as thermal management. In this study, we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation. The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath. Notably, the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers, primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process. With a BNNSs loading of 60 wt%, the resulting coaxial fibers showed exceptional properties, including an ultrahigh Herman orientation parameter of 0.81, thermal conductivity of 17.2 W m−1 K−1, and tensile strength of 192.5 MPa. These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers, making them highly suitable for applications such as wearable thermal management textiles. Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs. [ABSTRACT FROM AUTHOR]

The purpose of this study was to analyze the effects of sludge biochar (BC) application (2, 5, 10, 15% w/w) on the physico-chemical and thermal properties (thermal capacity, thermal conductivity and thermal diffusivity) of loess and the mechanism of action. The results showed that the application of BC changed the soil particle size distribution, reduced the soil bulk density, increased the soil total porosity (1.19–11.51%), organic matter content (10.94–85.02%), saturated water content (1.85–7.15%) and field water capacity (0.09–13.00%), and decreased the soil thermal capacity, thermal conductivity and thermal diffusivity, with an average decreasing amplitude of 2.13, 5.45 and 7.54%, respectively. Soil bulk density and water content (<30%) were positively correlated with soil thermal capacity, thermal diffusivity and thermal conductivity. The mechanisms are mainly that the negative impact of changing soil solid composition and increasing total porosity by biochar with low density and thermal parameter values; and the positive effect of raising water content by improving soil water holding capacity. Sludge biochar shows great potential in soil improvement and can realize sludge sustainable management. [ABSTRACT FROM AUTHOR]

A solid-phase metallurgy combined with spark plasma sintering technology was used to prepare U3Si2 pellets. The thermal conductivity and oxidation behavior of the pellets were studied. The pellets were highly dense (> 98% theoretical density) and had an ultra-high phase purity. The thermal conductivity of the U3Si2 pellets increased linearly with temperature from 300 to 973 K. By further annealing the pellets at 300 °C in air for two hours, the oxidation onset temperature was increased from 490 to 520 °C. A mechanism of pore passivation was proposed to account for the enhanced oxidation resistance. [ABSTRACT FROM AUTHOR]

Considering the harmful impact of the disposing of secondary aluminum dross (SAD) on the environment, we suggest producing aluminum dross microporous bricks (ADMBs) from SAD as a solution. These bricks possess thermal insulation properties, and we conducted research to study the impact of carbon powder particle sizes and sintering temperatures on their compressive strength, thermal conductivity, bulk density, and porosity. Additionally, we examined the mechanism of pore formation in the ADMBs. The results showed that the best overall performance of the prepared ADMBs was achieved with a porosity of 55.87%. There are three main types of internal pores. The first type is formed by the removal of carbon powder, which is generally formed near the surface layer of the ADMBS, and the hole size is related to the particle size of the carbon powder. The second type is formed by the expansion of holes, generally formed in the center of the ADMBS, the cavity size of which is related to the sintering temperature. The third type is formed by the expansion of cracks and is generally formed near the location where the original carbon powder was present. [ABSTRACT FROM AUTHOR]

This study investigated the mechanical properties and thermal conductivity of compacted graphite cast iron (CGI) with different pearlite concentrations. Four casts with different pearlite contents (4.12, 24.62, 53.24 and 87.74%) were obtained using heat treatments. As the pearlite content of the specimens increased from 4.12 to 87.74%, the tensile strength and hardness increased from 290.6 to 546.5 MPa, and from 114.3 to 238.6 HBS, respectively. The microscopic fracture surface observations of the CGI revealed that the quantity of tear ridges and cleavage planes decreased and increased, respectively, with an increasing pearlite concentration. The thermal conductivity decreased by 22.56% with an increasing pearlite content at the applied temperatures. Nevertheless, the thermal conductivity initially increased and then decreased with an increasing temperature, and its turning point was 473 K. Finally, the influencing mechanism of the pearlite content on the strength and thermal conductivity of CGI was illustrated. [ABSTRACT FROM AUTHOR]

Improved mechanical and thermal properties are important characteristics for enhancing the performance of cast iron components that operate at elevated temperatures. Thermal conductivity defines the temperature distribution within the casting and influences the magnitude of the thermally induced tensile stresses. The microstructural features that increase the thermal conductivity have a negative impact on tensile strength. The results reported in this work show that there is a unique inverse relationship between thermal conductivity and tensile strength, valid for the whole range of cast iron alloys regardless of graphite form, solidification rates, carbon content and matrix constituents. The finding indicates the challenges for the simultaneous improvement of these properties, and it can be utilized as a guideline during the design of cast iron components for high temperature applications. [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]

Non-edible oils hold great potential as a viable feedstock for bio-lubricant production. Among these oils, castor oil stands out due to its unique hydroxyl group structure. Castor oil finds applications in various fields such as lubrication, dielectrics, and heat transfer. This study focused on investigating the dynamic viscosity and thermal conductivity of castor oil and graphene nanoplatelets/castor oil nanofluids. The nanofluids were synthesized through a two-step process involving the combination of graphene nanoplatelets crystal powder with pure castor oil. Morphological and crystallographic analyses revealed platelet-shaped graphene nanoplatelets with a prominent (002) reflection. Dynamic viscosity measurements were performed using a rheometer at temperatures ranging from 40 °C to 100 °C, and thermal conductivity assessments were conducted using the Modified Transient Plane Source technique from 30 °C to 70 °C. Investigation revealed that as temperature increased, the nanofluids exhibited a significant decrease in dynamic viscosity. Conversely, the dynamic viscosity increased moderately with higher concentrations of graphene nanoplatelets. Importantly, the addition of graphene nanoplatelets did not disrupt the Newtonian flow behavior of castor oil. Furthermore, the study demonstrated a remarkable enhancement in thermal conductivity with increasing concentrations of graphene nanoplatelets. This enhancement can be attributed to the high conductivity of graphene nanoplatelets. Overall, biodegradable graphene nanoplatelets/castor oil nanofluid present promising prospects as an advanced lubricating oil with superior heat transfer properties. This research contributes to the understanding and utilization of nanofluids for effective thermal management applications. [ABSTRACT FROM AUTHOR]

Erythritol (ET) is a promising medium–low temperature organic phase change material. To solve the problems of supercooling, leakage, and low thermal conductivity, expanded graphite (EG) with four different particle sizes of 32 mesh, 50 mesh, 80 mesh, and 100 mesh was used as supporting material. A shape-stabilized composite phase change material (CPCM) with a mass ratio of EG to ET of 9:1 was prepared by the ultrasonic impregnation method. The properties were tested and analyzed by DSC, SEM, FTIR, XRD, and TGA. The experimental results showed that 50 mesh EG was more suitable as an adsorption carrier for erythritol among the four different particle sizes of EG. Compared with pure erythritol, the supercooling degree of 50 mesh EG/ET composite decreased by 35.2 %, the latent heat of solidification increased by 8 %, and the thermal conductivity increased by 250.8 %, which increased the heat storage and release capacity of the material by 19.2 %, and the 50 mesh EG/ET composite phase change material had good thermal stability. In this study, the relationship between the supercooling degree of EG/ET and EG particle size was analyzed, and EG/ET thermal storage materials with high thermal storage density and exothermic density were prepared. It helps to promote the application of EG-based composite thermal storage materials and the development of thermal storage technology. [ABSTRACT FROM AUTHOR]

Developing alternative eco-friendly construction materials is an important factor in sustainable development. Besides, one of the main ways to achieve this goal is the use of earthen materials in construction. In this respect, this study aims to investigate the feasibility of using Alfa fibers (Stipa tenacissima L.) and brick waste in the production of compressed earth blocks (CEB). Hence, the effects of Alfa fibers on the mechanical and thermal performance of CEB containing brick waste are analyzed. Brick waste content was fixed at 20% after an optimization study based on plasticity requirements, while Alfa fibers content varied from 0 to 0.5% of the dry weight of the block. Plain (unreinforced) CEB and fiber-reinforced CEB were tested for physical properties (density and absorption), compressive strength, and thermal behavior (conductivity and diffusivity). The results showed that Alfa fibers lightened the CEB. Also, adding Alfa fibers with a concentration of 0.5% increases the capillary absorption and the compressive strength by 40% and 111.25%, respectively. In terms of thermal properties, it is observed that using Alfa fibers improves the insulation aspect of the composite. Specifically, the thermal conductivity reduced by 13%. In all, using Alfa fibers and waste brick materials in CEB could be a promising solution to produce sustainable material with improved mechanical and thermal properties, contributing to the circular economy. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents may develop a pivotal role in future technologies considering sustainability and safety as pivotal aspects for chemistry developments. The possible application of these fluids for heat transfer operations is of great relevance for which the knowledge of thermal properties such as thermal conductivity is required as well as inferring structure–property relationships which allow reverse design of the fluids according to the technological requirements. Considering the technological relevance of this property, the available literature on the thermal conductivity for deep eutectic solvents is critically discussed showing strengths and weaknesses. The analysis of the state-of-the-art shows the future needs in this research field considering the application of these solvents for thermal-related technologies. The review indicates the scarcity of reliable experimental data and the need of predictive methods, which could be used for process design and solvent screening purposes. Likewise, considering the relevance of developing predictive methods for in silico design of these fluids according to industrial needs, the available predictive theoretical approaches are analysed showing their reliability as well as future needs. Finally, considering the need of developing suitable and reliable structure–property relationship, the molecular level basis of thermal conductivity in deep eutectic solvents is discussed, showing the role of hydrogen bonding and the effects rising from the involved hydrogen bond donors and acceptors as well as the eutectic compositions. This work reports the first literature review and analysis on thermal conductivity for deep eutectic solvents considering an experimental and theoretical approach as well as providing support for the molecular basis of this technologically relevant property, thus contributing to the development of environmentally friendly materials for thermal-related technologies. [ABSTRACT FROM AUTHOR]

Thermal properties such as thermal conductivity, heat capacity, and thermal diffusivity and physical properties such as calorific value, density, and kinematic viscosity of liquid fuels play a significant role in the combustion process. These properties vary with the chemical structures and the fatty acid profiles of biodiesels. Making correlations for various properties with respect to fatty acid profile helps to analyze the combustion process. Most of the reported works generated correlations using data taken from the literature, and the correlations based on the fatty acid profile for thermal properties of biodiesel are unavailable. As coconut oil, sunflower oil, and palm oil have entirely different fatty acid profiles, in this study, biodiesels produced from these three waste cooking oils and their three hybrids (each in a 1:1 ratio) were used for biodiesel production, followed by correlation formulation. Higher thermal conductivity (0.2211 W mK−1) and thermal diffusivity (0.2459 mm2 s−1) and lower heat capacity (0.8993 MJ m−3 K−1), density (862.8 kg m−3), kinematic viscosity (2.71 cSt), and calorific value (36.73 cSt) were observed for coconut-based biodiesels compared with other biodiesels. The addition of coconut content to hybrid biodiesel enhanced thermal conductivity and thermal diffusivity and reduced heat capacity, density, and kinematic viscosity. From the experimental data of thermal conductivity, heat capacity, thermal diffusivity, density, kinematic viscosity, and calorific value, empirical correlations were proposed with the fatty acid profile. Good agreement was obtained between experimental and calculated values. [ABSTRACT FROM AUTHOR]