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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]

The limited efficiency of traditional trial-and-error experiments has impeded the development and application of high-entropy fluorite oxides in thermal insulation coatings. To solve this problem, a novel entropy descriptor based on first principles is presented to help select candidate components for synthesizing high-entropy fluorite structure oxides. Results show that the compatibilities of 10 single-phase high-entropy fluorite oxides can be accurately predicted based on entropy formation ability. In the studied (Zr, Hf, Pr, La, X) O 2-δ system, a correlation between thermal characteristics and size/mass differences was established by designing the size and mass of X. Specifically, we found that the thermal conductivity is more strongly correlated with the difference in atomic mass, while the coefficient of thermal expansion is strongly correlated with the difference in atomic size. X-ray photoelectron spectroscopy (XPS) analysis shows that the concentration of oxygen vacancy can effectively reduce the thermal conductivity of high-entropy fluorite oxides. In addition, the values of hardness, elastic modulus and thermal conductivity of five single-phase fluorite oxides are successfully predicted by first principles calculation, and the differences between these values and the experimental results are small, which provides a prospective significance for the performance prediction of high-entropy fluorite oxides. Our findings provide a strategy for customizing high-entropy fluorite single-phase oxides with suitable properties to meet the performance requirements of thermal barrier coatings (TBCs). • The DFT calculation provides an entropy descriptor to evaluate the comfiability of high-entropy single-phase fluorite oxides based on their entropy formation capacity. • The hardness, elastic modulus and thermal conductivity of the studied sample are obtained by DFT calculation, and the difference between them and the experimental values is small. • In the (Zr, Hf, Pr, La, X)O 2-δ system, the atomic size difference and atomic mass difference of five single-phase samples were quantified, and their thermal conductivity and thermal expansion values were correlated. [ABSTRACT FROM AUTHOR]

Taking inspiration from the unique hierarchical structure of bio-materials like pearl oyster, this study employs bio-inspired composites technological route using flake powder metallurgy to prepare laminated Cu/Ti 3 SiC 2 /C composites. The prepared composites have clear laminated structure, uniform dispersion of reinforcing phase and clean interface. At a Cu-plated GNPs content of 0.5 wt%, the composites displayed tensile strength of 300.65 MPa, compressive strength of 575.32 MPa, electrical conductivity of 26.31 MS/m, and thermal conductivity of 285.87 W·m−1·K−1. The reinforcement of composites is caused by the load transfer effect of the laminated structure. During the loading process, the laminated structure creates multiple paths for deflecting cracks, which leads to the redistribution of the applied load. Moreover, the homogeneous distribution of GNPs throughout the laminated structure extends the mean free path of both free electrons and phonons within the material, consequently bolstering the electrical and thermal conductivity of the composites. [Display omitted] • Cu/Ti 3 SiC 2 /C laminated composites with balanced strength-toughness and good thermal and electrical conductivity were prepared. • The role of the lamellar structure was discussed. • The interfacial reactions and interfacial structure of Cu/Ti 3 SiC 2 /C was investigated. • The study investigated the mechanisms of interfacial thermal conductivity, interfacial electrical conductivity, and reinforced toughening. [ABSTRACT FROM AUTHOR]

This study explores the use of copper foam (CF) as a thermally conductive scaffold for phase change materials (PCMs), enhancing shape stability. Employing the ice template method (ITM), we fabricate a CF with a low-density, honeycomb structure and anisotropy from flake copper powders. The resulting phase change composites (PCCs), infused with paraffin wax (PW), showcase high thermal conductivity and shape retention compared to pure PW, with anisotropic heat flow due to directional channels in the CF. With a 34.4 wt% filling ratio, the PCCs achieve axial and lateral thermal conductivities of 2.85 W m−1 K−1 and 1.51 W m−1 K−1, respectively, and a thermal storage enthalpy of 158.18 J g−1. This work presents a novel method for advanced thermal energy storage and management, indicating the promise of ITM-derived CF in high-performance PCCs for diverse applications. • 3D porous copper with lighter weight, honeycomb-like and directional structure was prepared. • The composite has good form-stability and anti-leakage property. • The composite indicates high thermal conductivity of 2.85 W m−1k−1. • The composite indicates heat storage capability of 158.18 J g−1. • The composite has good anisotropic thermal conductivity. [ABSTRACT FROM AUTHOR]

In this work, a series of multicomponent rare-earth zirconate (RE 2 Zr 2 O 7 , RE=La, Nd, Sm, Eu, Gd or Yb) ceramics were synthesized using solid-state reaction method. The phase stability and key factors affecting the thermal conductivity and mechanical performances were investigated. These materials possess pyrochlore-fluorite dual-phase structure and show excellent high-temperature phase stability. (La 1/2 Yb 1/2) 2 Zr 2 O 7 displays a lower amorphous-like thermal conductivity (1.39–1.67 Wm−1K−1, 25–1000 °C), while other specimens present a 1/T-like dependence at low temperatures. (La 1/5 Nd 1/5 Sm 1/5 Gd 1/5 Yb 1/5) 2 Zr 2 O 7 exhibit higher hardness (11.37 ± 0.35 GPa) and fracture toughness (2.10 ± 0.11 MPa·m1/2) in comparison with others. Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase RE 2 Zr 2 O 7 ceramics, while the influence of configurational entropy is more significant for mechanical properties. A synergistic increase in configurational entropy and size disorder is an effective strategy to enhance the comprehensive performance of multicomponent dual-phase rare-earth zirconates. • A series of dual-phase medium- and high-entropy RE 2 Zr 2 O 7 ceramics were tailored and synthesized. • Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase rare-earth zirconates. • Entropy is a more effective descriptor than size disorder for influencing the mechanical properties of these materials. [ABSTRACT FROM AUTHOR]

Modern electronic technology necessitates the development of composite materials with effective electromagnetic protection. This work presents a novel strategy constructing an aramid nanofiber (ANF)-based Janus film (ANF@Cu-ANF/BN) using an electroless plating-vacuum assisted filtration-pressing technique. The film exhibits an unique asymmetric property profile, with one side being electrically conductive and thermally conductive/electrically insulating on the other. Exceptional EMI shielding effectiveness of 105.22 and 106.96 dB is obtained in the 8.2–12.4 GHz and 26.5–40 GHz ranges, respectively. In addition, the film demonstrates an impressive out-of-plane thermal conductivity of 2.703 W/(m·K). suggesting superior thermal management capabilities when integrated into heat sinks for high-power light-emitting diode modules. In terms of mechanical robustness, the film possesses a tensile strength of 14.31 MPa. The ANF@Cu-ANF/BN Janus composite films effectively harmonize electromagnetic shielding, thermal conductivity, and mechanical integrity, offering an innovative pathway of developing advanced materials that fulfill the stringent requirements of modern electronic devices. [Display omitted] • Aramid nanofibres coated with copper nanoparticles were achieved. • The Janus films exhibited electrically conductive (1593.65 S/cm)/insulating (5.55 × 109 Ω·cm) asymmetric property. • The Janus films showed superior EMI SE, reaching values of 105.22 and 106.96 dB within the X and Ka bands, respectively. • The Janus composites demonstrated an impressive out-of-plane thermal conductivity of 2.703 W/(m·K). [ABSTRACT FROM AUTHOR]

The phase change and thermal conductivity properties of nanocomposite materials consisting of cross-linked Poly(Styrene-block-Ethylene Glycol Dimethyl Methacrylate) (PS-PEG DM), boron nitride (BN), and selenium dioxide (SeO 2) were investigated in this study. The different content of phase-changed materials (PCM) nanocomposites was prepared by using the hydraulic pressure technique. Promising melting enthalpy values (104.5, 98.8 and 165.8 J g−1) have been reached for P1Se3, P2BN2Se2, and P3BN2Se2 PCM nanocomposites. The enthalpy efficiencies associated with the processes of melting and freezing, denoted as λ m and λ c , respectively, were determined by the analysis of data obtained from DSC. Our study was demonstrated to present comprehensive information on the PS-PEG/BN, PS-PEG/SeO 2 , and PS-PEG/BN/SeO 2 phase change nanomaterials, thereby facilitating their potential applications in various fields. The phase change and thermal conductivity properties of PS-PEG/BN/SeO 2 nanocomposites were investigated. The incorporation of SeO 2 and BN nanoparticles significantly enhanced the thermal conductivity (for P2BN4Se5), reaching values up to 8.277 W m−1 K−1. The λ m values of P1Se3, P2BN2Se2, and P3BN2Se2 were calculated as 68.79, 61.23, and 87.86, respectively. The λ c values of P2Se3; P1BN2Se2 were also calculated at 70.10; 98.93 and 161.92, respectively. [Display omitted] • Thermal energy storage properties of the PS-PEG/SeO 2 , PS-PEG/SeO 2 /BN PCM nanomaterials the thermal conductivity properties. • Studies are being carried out to increase the thermal conductivity properties of PS-PEG/SeO 2 , PS-PEG/SeO 2 /BN phase change nano materials. • The copolymers have the potential to serve as solid-state PCMs for applications involving thermal energy storage and temperature control. [ABSTRACT FROM AUTHOR]

The impact of Samarium (Sm) addition on hypereutectic Al-Ni alloys was systematically investigated, focusing on microstructural changes and thermal-physical, mechanical properties. The addition of 0.1–0.5 wt% Sm resulted in the refinement of primary Al 3 Ni phases from coarse lath-like structures to small particles, enhancing mechanical properties and reducing thermal expansion coefficients (CTE). Thermal conductivity (TC) improved with 0.1–0.3 wt% Sm addition, but declined at the amount of 0.5 wt%. Excessive Sm addition leads to the formation of a Sm-rich phase, characterized by a two-phase mixed structure of Al 11 (Ni, Sm) 3 surrounded by Al 4 Sm. Sm addition lowered the precipitation temperature of the primary Al 3 Ni phase, inducing significant constitutional undercooling and exhibiting a phase refinement effect. The Al-9Ni-0.3Sm alloy showed excellent performance, with a TC of 211.8 W/(m·K), CTE of 17.3×10−6/K (@25–100 °C), ultimate tensile strength of 169.5 MPa, and elongation of 10.4 %. Optimal addition of Sm improved TC, mechanical properties as well as reduced the CTE in the Al alloy at the same time and showed a good modification effect. [Display omitted] • Sm addition refines the primary and eutectic Al 3 Ni phases in the Al-10Ni alloy. • Adding Sm lowers the initial solidification temperature, inducing constitutional undercooling for phase refinement. • Sm modification enhances both thermal-physical properties and mechanical properties. • A new Sm-rich structure forms at higher Sm content, affecting modification and refinement effects in the Al-10Ni alloy. • The Sm-rich structure is determined as a structure of the inner Al 11 (Sm, Ni) 3 phase wrapped by the outer Al 4 Sm phase. [ABSTRACT FROM AUTHOR]

It is of both scientific and technical significance to adjust the balance between the thermal conductivity and mechanical performance of Al-Si alloys. In this work, we proposed a strategy of using mixed-additive to perform such tuning. A permanent mold casting (PMC) was used to optimize the as-cast properties based on the orthogonal combination of Sr and TiB 2. It is anticipated that the addition of Sr addition can modify the eutectic Si, while the addition of TiB 2 can refine the primary α-Al dendrites, with uncertainty of its effects on the modification efficiency of Sr. The results showed that addition of TiB 2 does not impair the modification efficiency of Sr. The optimized composition contained 200 ppm Sr and 300 ppm Ti. Casting specimens were then prepared using high-pressure die casting (HPDC) process. The results demonstrated that significant reduction in the size of β-AlFeSi, eutectic Si, and α-Al grains can be achieved by HPDC process. As a result, the tensile properties have been improved. The natural effects of HPDC process on the alloy, however, such as microstructure refinement and variation in porosity, leading to deduction in the thermal conductivity to 148.5 W/(m·K). This value still exceeds conventional alloys nevertheless. [Display omitted] • A novel strategy is proposed to improve the mechanical properties and thermal conductivity in Al-Si-Fe alloys. • The addition of TiB 2 does not impair the modification efficiency of Sr. • The HPDC alloy demonstrates excellent mechanical properties and favorable thermal conductivity. [ABSTRACT FROM AUTHOR]

Quaternary chalcogenides are attractive for a variety of technological fields of interest due to the diverse physical properties these materials possess. Herein, the structural and thermal properties of the disordered chalcopyrite AgInSnSe 4 are reported revealing a distinct relation between its structure and physical properties. Modeling of the experimental temperature-dependent thermal properties revealed an ultralow thermal conductivity (0.47 Wm−1K−1 at room temperature) due to lattice anharmonicity, a low speed of sound and a low Debye temperature. Moreover, first principles electronic structure calculations revealed that the Ag-Se tetrahedra within the crystal structure possess relatively weak bonds due to occupied antibonding states from p - d orbital hybridization, which suppress the thermal conductivity. In order to further quantify our findings, we extended our analyses to include comparisons with other ternary and quaternary adamantine materials, all of which possess a fourfold tetrahedral coordination of atoms, in revealing the origin of the thermal properties in AgInSnSe 4. • The defect chalcopyrite AgInSnSe 4 possesses ultralow thermal conductivity, κ , lower than that of related chalcogenides. • Substitution of Cu by Ag in this chalcopyrite structure induces tetragonal distortions along the c -axis in crystal lattice. • The ultralow κ , low Debye temperature, low speed of sound and large anharmonicity are consequences of lattice distortion. • This is the lowest thermal conductivity thus far reported for a tetrahedrally bonded diamond-like structured material. [ABSTRACT FROM AUTHOR]

Core-shell structured copper-boron nitride (Cu@BN) spherical fillers were synthesized to fabricate thermally conductive composites. To enhance the interaction between the fillers and the matrix, polysilazane (PSZ) was coated on the surface of the filler. The resultant composite exhibited remarkable characteristics, including a substantial tensile strength of 32.36 MPa, excellent electrical insulation properties, and impressive thermal conductivity of 3.47 W/mK. When applied in a light-emitting diode (LED) application, the composite effectively managed heat, reducing the operating temperature by 34 °C. The epoxy/PSZ-Cu@BN composites hold great promise for improving thermal management in electronic devices. • The copper-boron nitride (CuBN) core-shell structured filler was fabricated. • The PSZ coating of CuBN reinforced thermal and mechanical properties of composites. • The Epoxy/PSZ-CuBN composites achieved high thermal management performance. [ABSTRACT FROM AUTHOR]

With the increasing demand for highly integrated circuits to optimize energy efficiency, reduce weight, and improve mechanical properties, finding a Magnesium (Mg) matrix material with excellent mechanical strength and high thermal conductivity poses a significant challenge. In this work, titanium (Ti) particles were introduced into AZ91 (Mg-9Al-1Zn) alloy to fabricate Ti/AZ91 composites, employing a combination of stir casting, extrusion and rolling processes. This strategy simultaneously enhances the mechanical properties and thermal conductivity of the Ti/AZ91 composites compared with AZ91 alloy. The incorporation of Ti particles serves to refine grains, expediting the formation of Mg 17 Al 12 phase within the Mg matrix. Optimal comprehensive mechanical properties are attained in 10 wt% Ti/AZ91 composite, exhibiting an ultimate tensile strength of 365 MPa, an elongation of 11.9 %, and a significantly low wear rate of 4.548×10−3 mm3/m. Notably, the 10 wt% Ti/AZ91 composite shows a 41.1 % reduction in wear rate relative to the AZ91 alloy, attributed to the incorporation of hard Ti particles. Furthermore, the thermal conductivity of the 2.5 wt% Ti/AZ91 composite exhibits a significant enhancement over that of the AZ91 alloy. Detailed discussions are provided on the fundamental mechanisms responsible for strengthening, wear resistance, and thermally conductive in Ti/AZ91 composites. These results highlight the substantial potential of Ti/AZ91 composites for lightweight structural applications, such as highly integrated circuits requiring excellent mechanical properties and high thermal conductivity. [Display omitted] • The 10Ti/AZ91 composite demonstrates a remarkable improvement in UTS, EL and wear resistance. • Enhanced mechanical properties results from the deformable Ti particles, refined grains, and weakening of texture. • The Ti/AZ91 composites possess exceptional thermal conductivity while maintaining high strength. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) shows great potential in the fabrication of bulk YH 2- x. For the first time, the high-pressure SPS (HPSPS) of YH 2- x is explored and compared with the routine SPS. It is found that HPSPS remarkably reduces the densification temperature, and thus the thermal dehydrogenation phase transition (δ-YH 2- x → α-Y) and the hydrogen loss of YH 2- x can be avoided. Nearly fully dense δ-YH 1.80 monolith is successfully prepared by HPSPS under 500 MPa at a relatively low temperature of 800 °C. HPSPS is effective in overcoming the thermal dehydrogenation problem during the sintering of YH 2- x. Compared with significant grain growth in the routine SPS, the grain growth in the HPSPS is very limited. In terms of thermal properties, the thermal conductivity of HPSPS prepared YH 2- x is relatively low below 600 °C, then tends to be closed above 600 °C, compared with routine SPS prepared and directly hydrided YH 2- x. The thermal expansion of HPSPS prepared dense YH 2- x is basically consistent with that of directly hydrided bulk. This study provides a valuable reference for the sintering of high-quality δ-YH 2- x and other metal hydrides monoliths. • High-pressure SPS (HPSPS) is used to fabricate dense δ-YH 2- x for the first time. • The differences between routine SPS and HPSPS of dense YH 2- x are clarified. • HPSPS provides a "low-temperature sintering" and very limited grain growth. • The thermal dehydrogenation problem in the sintering of YH 2- x is overcome by HPSPS. [ABSTRACT FROM AUTHOR]

SiC is a promising structural material for future advanced nuclear energy systems. However, the inherent brittleness and difficulty of densification of SiC limits its practical application. In this study, medium entropy alloy (CrCoNi) reinforced silicon carbide composites (CCN/SiC) were sintered at 1950–2200°C by spark plasma sintering (SPS). The influence of CCN addition on the CCN/SiC composites was investigated in terms of microstructure, mechanical and thermal properties. The results show that SiC sintered at 2200℃ has the highest density, and the addition of 7.5 wt% CCN can significantly improve the fracture toughness of SiC. Transgranular fracture, crack deflection, and premature crack termination due to interfacial passivation are considered as potential toughening mechanisms. Although the addition of CCN can degrade the thermal conductivity of SiC ceramics, it has little effect on the structural stability of the SiC matrix at high temperatures. • A dimpled fracture feature was found in the CCN/SiC composites. • The composite exhibits very good structural stability at 1200 °C. • The addition of CrCoNi doubled the fracture toughness of SiC ceramics. [ABSTRACT FROM AUTHOR]

Sinnerite Cu 6 As 4 S 9 has been identified as a promising material for optoelectronic applications, with potential for other energy-related applications; however, knowledge of the electrical and thermal properties as well as the mechanisms underlying transport in sinnerite is lacking. We present an investigation of the synthesis, structural, thermal and electrical transport properties of stoichiometric and Sn-doped Cu 6 As 4 S 9. Sinnerite has a triclinic lattice structure, with highly distorted local atomic coordination environments that, in part, results in its complex structure and bonding. Our results and analyses indicate As 4 s 2 lone pair-induced distortions and strong lattice anharmonicity that leads to a relatively short phonon mean free path, resulting in intrinsically very low thermal conductivity. The electrical resistivity for both compositions, Cu 6 As 4-x Sn x S 9 (x = 0, 0.2), are relatively high and varies little with temperature, typical of degenerate semiconductors. An increase in mobility and electrical conductivity was obtained by Sn doping in Cu 6 As 3.8 Sn 0.2 S 9. This work demonstrates an effective route to synthesize bulk sinnerite as well as advances the knowledge of the properties of sinnerite, as this and other ternary chalcogenides continue to be of interest for potential technologically significant applications. [Display omitted] • Polycrystalline sinnerites were successfully synthesized by ball milling and solid-state annealing. • The thermal conductivity is intrinsically low (< 1 Wm−1K−1) due to the unique structure and bonding. • The mobility and electrical conductivity increase and the thermal conductivity decreases with Sn doping. • The thermoelectric properties improved by 60% with Sn doping. [ABSTRACT FROM AUTHOR]

Pyrochlore ceramics with chemical formula A 2 B 2 O 7 (A= rare earth, B= tetravalent metal) have extremely low thermal conductivities (κ) and are thought to be promising candidates for thermal barrier coatings (TBCs) applications. This study reports κ for nanocrystalline (nc) Gd 2 Ti 2 O 7 pyrochlore fabricated by spark plasma sintering followed by sintering at different temperatures to better understand their thermal properties. The structural analysis confirmed the synthesis of single-phase nc-Gd 2 Ti 2 O 7 pyrochlore. The thermal conductivity investigations displayed a systematic decrease in thermal conductivity from 1.6 Wm−1K−1 to 0.6 Wm−1K−1 for the sample sintered at a lower temperature due to high porosity. The value of the κ is found to decrease sublinearly (κ ∝ T-α, where 0 < α < 1) with temperature for all the nc-Gd 2 Ti 2 O 7 pyrochlore samples. DFT- GGA calculation exhibits that the nc-Gd 2 Ti 2 O 7 is a direct band gap at the Γ point of the Brillouin zone, and its value is increased with the sintering temperature. In addition, the effect of sintering temperature on the specific heat capacity (C p) is insignificant in nc-Gd 2 Ti 2 O 7 structures, as confirmed by the quasi-harmonic approximation. Theoretical and experimentally determined results are in good agreement, and values are compatible with the thermal insulation requirements for various applications. • The thermal conductivity (κ) decreases from 1.6 Wm-1K-1 to 0.6 Wm-1K-1 with lowering sintering temperature. • The thermal conductivity (κ) decreases similarly for the highly dense samples sintered at 1000 ℃ and 1200 ℃. • The κ value decreases sublinearly (κ ∝ T-α, where 0 < α < 1) with temperature for all the nc-Gd 2 Ti 2 O 7 pyrochlore samples. • DFT calculated specific heat capacity (C p) systematically increases with increasing measuring temperature. [ABSTRACT FROM AUTHOR]

Modified C/C composites are promising candidates to the advanced piston of internal engine, pantograph slide plate and rapid-fire gun barrel. To understand the corrosion in the working conditions of these thermal components, cyclic ablations of C/C-SiC-ZrB 2 -ZrC (C/C-SZZ) were carried out in high frequent impacted combustions at different temperatures (700–2300 ℃). Parallel study of AlSi alloy modified C/C-SiC-ZrB 2 -ZrC (C/C-SZZ-AS) which had lower cost was performed synchronously for comparison. Results indicated that the ablation rates of both the composites went down with decreased temperature while C/C-SZZ-AS presented a faster decline. Compared with C/C-SZZ, the pressure infiltrated AlSi alloy matrix of C/C-SZZ-AS raised the conductivity and specific heat capacity but reduced the emissivity, which led to a lower surface temperature and thermal gradient during ablation. And combined with the better plasticity and toughness of the alloy matrix, C/C-SZZ had stronger ablation resistance below 1500 ℃ in the serious thermal shock. At temperature above 1500 ℃, excessive phase transformation of the AlSi alloy matrix caused more defects and strengthened the mechanical erosion. And then the faster consumption of the AlSi alloy resulted in the greatly worsened ablation property of C/C-SZZ at 2300 ℃. • C/C-SiC-ZrB 2 -ZrC was high frequently cyclic ablated at different temperatures. • Pressure infiltrated AlSi alloy improved the ablation property below 1500 ℃. • The alloy matrix elevated the ablation sensitivity to combustion temperature. [ABSTRACT FROM AUTHOR]

The mechanical properties especially the compression performance are very important for thermal interface materials (TIMs) to mitigate warpage failure caused by stress concentration and reduce contact resistance in practical applications. However, high thermal conductivity and excellent mechanical properties are generally incompatible in traditional TIMs. Herein, we fabricate a high-performance carbon fiber-based TIM by using an extrusion method based on the flow shearing effect. The vertically oriented composite shows a through-plane thermal conductivity up to 18.5 W·m−1·K−1 at 20 wt% carbon fiber content, which is 92.7 times that of pure matrix and 6.3 times that of the random structure. Moreover, the as-prepared material exhibits low hardness of 56 (Shore 00) and outstanding elastic compression performance of 51.4% compression under a pressure of 45 psi. These excellent properties are primarily attributed to the high orientation of the carbon fibers (CFs), thereby establishing a direct and effective thermal conductivity path in the vertical direction. In addition, the synergistic effect of carbon fibers and alumina particles is also beneficial for building thermal conduction pathways. Our work provides an insight to further research in fabricating high-performance flexible TIMs as a promising candidate for applying in advanced thermal management fields. • The composite achieves a thermal conductivity of 18.54 W·m−1·K−1. • The composites exhibit good elastic compliance under high through-plane thermal conductivity. • The synergistic effect of carbon fibers and alumina promotes the enhancement of thermal conductivity [ABSTRACT FROM AUTHOR]

The unique transport properties make CuInTe 2 emerge as a promising thermoelectric material. However, the intrinsically low carrier concentration and high lattice thermal conductivity of CuInTe 2 limit its thermoelectric performance. In this work, firstly, we investigate the influence of excess Te on the electrical and thermal transport properties of CuInTe 2. The results suggest that excess Te can act as both electron acceptors and phonon scattering centers, which simultaneously optimizes the carrier concentration and impedes the propagation of high-frequency phonons. Furthermore, the substitutional Ag/Cu defects integrated with excess Te lead to a further reduction in lattice thermal conductivity. DFT calculations indicate that the substitution of Ag for Cu can reduce phonon group velocity and intensify the acoustic phonon scattering, which agrees well with our experimental data. Finally, a high zT value of 1.03 is obtained @840 K for sample Cu 0.8 Ag 0.2 InTe 2.2. This study demonstrates a facile but effective approach to boost the thermoelectric performance of chalcopyrite compounds. [Display omitted] • Excess Te optimizes the carrier concentration and impedes the propagation of high-frequency phonons. • The introduction of Ag on Cu sites results in a further reduction in lattice thermal conductivity. [ABSTRACT FROM AUTHOR]

This study explores the influence of processing methods on the connectivity of a ceramic component and its effect on the dielectric and thermal properties in Li 2 MoO 4 -polytetrafluoroethylene (LMO-PTFE) composites. Three processing cases were examined: cold sintering (case 1), dry pressing and subsequent thermal annealing (case 2), and cold sintering and subsequent thermal annealing (case 3). The processing methods change the connectivity of ceramic grains, the crystallinity of PTFE, and the dielectric properties of these composites. The microstructure analysis shows that CSP increases the LMO domain size via the dissolution and precipitation steps. The connected LMO grains increases the transport length of Li ions under electric field and manifests the space charge polarization in the dielectric measurments. More connected LMO grains of the composites also enhance thermal transport, while phonon scattering of discrete LMO particles lowers the thermal conductivity of the composites. • Processing methods change the connectivity of a ceramic component in a polymer matrix. • Cold sintering process increases the ceramic domain size in the ceramic-polymer composite. • The connected ceramics grains increase the transport length of Li ions under electric field. • Thermal conductivity can be enhanced by a chain of connected ceramic grains. • This study contributes to the rational design of high-performance dielectric composites. [ABSTRACT FROM AUTHOR]

To improve the incompatibility between thermal conduction and electromagnetic wave absorption properties, 3D interconnected CNF/Co composites as a multifunctional filler were fabricated with magnetic/dielectric dual loss and phonon/electron co-transfer via a straightforward sol-gel and annealing route. Results show that the CNF/Co composites produced at a high Co2+ concentration (c) exhibit low defects, small S BET , large electrical conductivity, and high Co content. The optimal comprehensive properties of CNF/Co composites are achieved at c = 0.8 M. Besides, the CNF/Co composites bear a large thermal conductivity (3.61 W/mK) at a low load (15 wt%) due to the enhanced phonon/electron co-transfer in 3D interconnected CNF frameworks and decreased phonon scattering. Moreover, the CNF/Co composites demonstrate tunable electrical conductivity (σ = 7.53 ×10−5 ∼ 1.22 ×10−2 S/cm) and significant enhancements in electromagnetic wave absorption properties (4.53 GHz/mm, 2.4 mm thickness, 35% load), outperforming most other previously reported materials. The significant enhancements could be attributed to the high attenuation and excellent impedance matching caused by magnetic/dielectric dual-loss Co and 3D interconnected porous frameworks. The exceptional electromagnetic wave absorption properties and thermal conduction endow the 3D interconnected CNF/Co composites with prospective application as a multifunctional filler in modern electronics. 3D interconnected CNF/Co composites were synthesized via a straightforward sol-gel and annealing route, exhibiting a synchronous enhancement in heat conductance and EMW absorption. [Display omitted] • A facile synthesis of 3D interconnected CNF/Co composites. • Optimizing the composition, structure, and properties of the composites. • A synchronous enhancement in heat conductance and EMW absorption. • Revealing the mechanism of synchronous enhancement. [ABSTRACT FROM AUTHOR]

Improving thermal properties of polymer-based composites by using different types of fillers most of the time also reduces material elasticity and flexural strength, which is a significant problem for application. To address this problem, we have used two types of two-dimensional materials, such as reduced graphene oxide (rGO) and hexagonal boron nitride (hBN) to achieve better thermal and mechanical properties. Great tensile strength and flexibility of both those 2D-materials combined with good thermal conductivity of hBN provided a synergistic effect for the resulting composites. Here we show the composites with 30% of hBN and 10% rGO by weight that have greatly improved flexural strength and flexural modulus as well as more than threefold increased thermal conductivity as compared to pristine polypropylene. Mechanical properties of composites only filled with hBN are significantly lower. [Display omitted] • Two types of 2D fillers such as hBN and rGO were successfully used in PP matrix. • Usage of two 2D fillers increases thermal and mechanical properties of PP. • Composite with rGO and hBN showed better mechanical properties than with only hBN. [ABSTRACT FROM AUTHOR]

Friction Stir Processing (FSP) involves the use of Silicon Carbide (SiC) and Graphite (Gr) nanoparticles as reinforcements to enhance the properties of AZ91 Mg alloy composites. The relationship between FSP processing parameters and surface properties of Mg alloy composites with SiC and Gr nanoparticles is poorly understood. The present study addresses this and investigates the impact of SiC and Gr volume percentages (%vol), tool traverse speed (TTS), and tool rotational speed (TRS) on the corrosion behavior and microhardness of AZ91 alloy composites. FSP turns graphite into layered graphene, making it more corrosion-resistant and stronger through various strengthening mechanisms. Taguchi optimization yielded optimal settings in runs H7 (1500 rpm-20 mm/min-13 %vol) and H8 (1500 rpm-40 mm/min-7 %vol) for high microhardness and low corrosion rate. Conversely, runs H1 (500 rpm-20 mm/min-7 %vol) and H3 (500 rpm-60 mm/min-13 %vol) resulted in reduced microhardness and increased corrosion rate. Integrating Taguchi and Grey Relational Analysis (GRA) optimized the multi-objective enhancement of microhardness and corrosion resistance, achieving 3rd-level values for TRS, TTS, and %vol. Notably, the reinforcement percentage, followed by TRS and TTS, simultaneously improved these responses. • Fabrication of flawless AZ91 surface hybrid composites using friction stir processing. • Exploring process parameters on the microstructure, microhardness and corrosion behavior. • Strengthening mechanisms associated with microstructural changes and contributions of SiC and Gr reinforcements. • Mechanical exfoliation of few-layered graphene (FLGs) from graphite. • Taguchi-Grey Relational Analysis employed for multi-objective optimization. [ABSTRACT FROM AUTHOR]

The natural mineral-based CoSbS compound has been identified as a potential candidate material for thermoelectric power generation. In this report, the solid solutions of CoSb 1−x S 1−x Se 2x (x ≤ 0.2) were constructed, and their electrical and thermal properties were studied at the temperatures ranging from 323 to 823 K. The results show that the dual doping of Se on Sb and S sites not only tunes the carrier concentration but also modifies the electronic structure, thereby optimizing the power factor of CoSbS effectively. Meanwhile, both the mass and the strain field fluctuation caused by the substitution of Se for both Sb and S strongly suppress the thermal conductivity of CoSbS, and finally make an enhanced zT ∼0.3 for CoSb 0.8 S 0.8 Se 0.4 at 823 K. In particular, the maximum averaged zT from 323 to 823 K in this study reaches ∼0.2, far exceeding the results of Se doping at single Sb or S site in CoSbS. These results indicate that dual doping at Sb and S sites via Se is an effective approach to make better thermoelectric performance for CoSbS. • Thermoelectric compound CoSbS with dual defects of Se Sb and Se S was constructed. • The carrier concentration and electronic structure of CoSbS were modified effectively by introducing of Se Sb and Se S defects. • An enhanced zT avg was obtained for CoSbS with Se Sb and Se S defects. [ABSTRACT FROM AUTHOR]

Pb doped Cu 3 Sb 1-x Pb x Se 4 (x = 0, 0.01, 0.02, 0.04 and 0.06) compounds have been synthesized via microwave-assisted solvothermal method followed by SPS progress, and their thermoelectric properties from 300 K to 623 K has been explored. On one hand, Pb doping in the Sb site improved the electrical properties of Cu 3 SbSe 4 , on the other hand, the second phase PbSe formed at the high doping content (x ≥ 0.02) reduced the thermal conductivity by the phonon scattering. Altogether, the improvement of the electrical properties and decrease of the thermal conductivity results in a promising peak zT of ∼0.52 at 623 K of Cu 3 Sb 0.96 Pb 0.04 Se 4 sample, which is about 80% higher than that of the un-doped Cu 3 SbSe 4. The current work provides a method which can reduce the thermal conductivity by forming heterojunction and also improve the electrical properties by doping of one element. • Highlight: • We investigated the thermoelectric performance of Pb-doped Cu 3 SbSe 4. • The in-situ second phase PbSe could reduce the thermal conductivity. • Small amount Pb doping Cu 3 SbSe 4 could optimize its carrier concentration. • The size of second phase could effect overall thermoelectric performance. [ABSTRACT FROM AUTHOR]

In this paper, we report on a systematic investigation on the microstructure, magnetocaloric effect and thermal transport properties of La-Fe-Si-H/Sn composites prepared by hot pressing. A continuously distributed Sn network is constructed to restore the mechanical integrity of La-Fe-Si-H hydrides. The hot-pressed composites show good magnetocaloric performance and improved thermal conductivity with optimized interface contacts of La-Fe-Si-H/Sn and hot-pressing parameters. A modified Hasselman-Johnson model is adopted in predicting the thermal conductivity of La-Fe-Si-H/Sn composites in terms of reasonable particle size, interfacial contact conditions and porosity. A large magnetic entropy change of 11 J/kg K in 2 T and high thermal conductivity of ∼9 W/mK could be simultaneously achieved in LaFe 11.6 Si 1.4 H x /Sn. This work contributes to the research on high performance magnetocaloric composites with combined outstanding magnetocaloric and thermal transport properties. • The mechanical integrity of La-Fe-Si-H has been restored by Sn matrix. • The large magnetocaloric effect is retained and thermal conductivity is improved. • The principles in the design of high thermal conductive functional composites are revealed. [ABSTRACT FROM AUTHOR]

Thermal management is one of the most promising applications of Al parts fabricated by additive manufacturing, primarily due to the drastically expanded design space enabled by the latter. The thermal properties of additively manufactured Al alloys are crucial for this application but remain poorly understood. The present study focuses on a high-strength Al-Mg-Sc-Zr alloy fabricated by Selective Laser Melting (SLM). The microstructure of the alloy is characterized by optical and electron microscopy, hardness and tensile testing are conducted, and the thermal conductivity and thermal dilatation behavior are tested. The fabricated samples exhibit strong age hardenability and yield strengths reaching ∼460 MPa. The thermal conductivity in the as-built condition is found to be rather low mainly because of the high solute concentration in the Al matrix as well as the fine grain size, and is improved by 33% after 10 h aging due to precipitation of particles. Meanwhile, abnormal non-linear thermal dilatation behavior is observed in the samples above 400 °C, probably related to the expansion of pores. Lastly, orientation dependency with respect to the building direction is found in both thermal conductivity and dilatation, which is associated with the grain alignment and melt pool structures. The above results provide critical knowledge to the process design toward co-optimization of mechanical and thermal properties of Al alloys fabricated by SLM. • The Selective Laser Melted Al-Mg-Sc-Zr alloy shows excellent age hardenability. • The as-built thermal conductivity is relatively low and is improved upon aging treatment. • The thermal expansion behavior shows anomaly at temperatures above 400 °C. • Both thermal conductivity and thermal expansion behavior exhibit anisotropy with respect to the building direction. [ABSTRACT FROM AUTHOR]

Al alloy modified C/C composites are one of the most promising light-weight materials. To understand the influence of alloying, AlSi and AlSiCu melts were pressure infiltrated into porous C/C skeletons respectively and the ablation properties were mainly studied. Results showed that Cu and Al generated Al 2 Cu in AlSi matrix, and the compression strength of the composite was enhanced while the thermal conductivity and the phase transition temperature decreased. The matrix alloy with Cu softened and melted faster and more during cyclic ablation, which protected the C/C skeleton form thermal stress damage. Thus, the addition of Cu led to a decrease in linear ablation rate. • The micro-scale Al 2 Cu phases are distributed at the matrix and C-Al interface of C/C-AlSiCu composite. • C/C-AlSiCu has a lower linear ablation rate than C/C-AlSi at the same cyclic ablation environment. • The cyclic ablation behaviors were dominated by the thermal conductivity, specific heat, and phase transition temperature. [ABSTRACT FROM AUTHOR]

α-SrSi 2 is a promising material for thermoelectric application around room temperature, especially if we can decrease the lattice contribution to the thermal conductivity. We report in this article the effect of the nanostructuring and the effect of the purity on the thermal and thermoelectric properties. Combining ball milling and spark plasma sintering we show that it is possible to obtain nanostructured pellets with grain size about 200 nm which permit to decrease the lattice components to the thermal conductivity close to that expected to highly disordered or amorphous materials. The results obtained in this study also show that the figure of merit ZT is improved after nanostructuring to a value of 0.20 around room temperature. The effect of the Sr purity on the thermoelectric properties is also presented. • Pure α-SrSi 2 is obtained after only 15 min of ball milling. • Nanostructuring of α-SrSi 2 is maintained after spark plasma sintering. • Lattice thermal conductivity is strongly affected by nanostructuring. • A maximum value of ZT = 0.20 is obtained for p-type α-SrSi 2 at room temperature. [ABSTRACT FROM AUTHOR]

The poor mechanical properties of La-Fe-Si based alloys restrict the potential of these magnetocaloric materials. Hence, a novel transient liquid phase bonding (TLPB) processing technique was deployed during spark plasma sintering (SPS) of La-Fe-Si based bulk materials. A series of binder-free LaFe 11.8 Si 1.2 bulk materials were prepared by SPS and hot-pressing sintering (HPS). Transient melting, which occurred during SPS, accelerated the decomposition of the 1:13 phase, resulting in low porosity and high strength. Compared to HPS samples, SPS samples have significantly larger maximum compressive strength (σ bc)max of ∼637.9 MPa at a strain of 4.7%, good thermal conductivity of ∼7.6 W·m−1·K−1 at 300 K, and a large (−Δ S M)max value of ∼11.7 J·kg−1·K−1 at T C = 193 K under a magnetic field change of 0 − 5 T. Thus, binder-free La-Fe-Si based bulk magnetocaloric materials with an excellent property set have been successfully prepared by TLPB assisted SPS technology. [Display omitted] • LaFe 11.8 Si 1.2 alloys were prepared by a novel transient liquid phase bonding assisted SPS. • The mechanical and thermal properties of SPS samples was better than HPS samples. • SPS is a promising processing technology to prepare MCMs with excellent performance. [ABSTRACT FROM AUTHOR]

In view of the diversified requirements for polymer-based composites in modern electronic devices and electrical systems, a great challenge has to be faced in realizing the simultaneous enhancement of thermal-electrical-mechanical properties. Herein, we designed the gradient structured composites by building polyethylene (PE) based composites with different Al 2 O 3 contents and optimized the properties by adjusting the distribution of temperature, electric and stress fields. The composites with double-layered gradient structure achieves superior through-plane thermal conductivity of 0.65 W/(m·K), high breakdown strength of 94.2 kV/mm and good tensile strength of 10.1 MPa, revealing an increase of 25 %, 10 % and 9 % compared to the traditional Al 2 O 3 /LLDPE composites, respectively. Finite element simulation provided favorable evidences for the action mechanism on gradient structure regulating temperature and electric field. The strategy of constructing gradient structure provides a feasible route to meet the comprehensive performance requirements of PE based composites in massive manufacture scenario for practical insulation applications. [Display omitted] ● The gradient structure was designed to achieve the simultaneous enhancement of thermal-electrical-mechanical properties. ● The mechanism of gradient structure lay in its regulation on the distribution of temperature, electric and stress field. ● FES provided the feasible models to reveal temperature profiles and breakdown process in the gradient structure. [ABSTRACT FROM AUTHOR]

ThN has the same crystal structure as UN but is considered to be easier to investigate theoretically since the Th atom is not magnetic. However, researchers recently predicted theoretically its thermal conductivity to be very low due to a very low electron density of states at Fermi Energy, which is incorrect. The electronic contribution to thermal conductivity in ThN has recently been consistently evaluated to be significant (∼40 Wm−1K−1) by using the measured resistivity and first principles. However, the method of evaluating the remaining contribution from phonons is still disputed. We present calculations of the lattice thermal conductivity of ThN, which is evaluated from the experiment at room temperature to be relatively low (∼20 Wm−1K−1) by using two methods: phono3py and ShengBTE. [ABSTRACT FROM AUTHOR]

The development of high-temperature composite phase change materials (CPCMs) suitable for mass-production and high-performance is still a very urgent problem in the efficient utilization of renewable energy. In this study, a SiC spherical high-temperature CPCMs based on aqueous gel-casting suitable for batch molding using commercially available silicone molds is proposed. The porosity of the porous SiC framework can be adjusted by changing the content of starch granules in the slurry. The sample containing 20 wt% starch has relatively high open porosity and thermal conductivity, which is considered to be close to the optimal formulation of CPCMs. This formula possesses a high thermal conductivity of 10.2 W·m−1·k−1 benefiting from the continuous thermal transport channels consisting of the uniformly distributed large spherical pores and interconnected small pores. Meanwhile, the thermal storage density of the CPCMs reaches 395.21 J·g−1 in the temperature range of 550 ℃ and 750 ℃ since up to 89.06% of the pores are filled with molten salts. At the same time, the CPCMs exhibit excellent cycle stability in 100 thermal cycles. In particular, these CPCMs can be easily integrated into thermal energy storage (TES) system. Based on the rapid heat storage simulation of the C-D model, the packed-bed latent thermal energy storage system containing spherical CPCMs will have a more uniform temperature distribution and a 26.7% reduction in charging time compared with the traditional packed-bed system. This work provides a new reference for the design of spherical CPCMs in TES systems. • A high-temp spherical shaped CPCMs suitable for mass production is prepared. • Spher-CPCMs achieve higher thermal conductivity at relatively large energy density. • CPCMs exhibit an excellent mechanical strength of 122.10 Mpa. • The charge-discharge process of a system with CPCMs is shortened by 26.7% and 36.3%. • Spherical CPCMs are potential substitutes for traditional steel ball capsules. [ABSTRACT FROM AUTHOR]

The present work deals with the structure, electrical and thermal transport properties of Al-Cu-Fe quasicrystal (IQC) reinforced with soft Sn phase (10–30 vol%) processed by mechanical milling and subsequent annealing. The 40 h milled powder of IQC-Sn nanocomposite contains IQC phase along with other crystalline phases i.e. B2-Al(Cu, Fe) (a = 0.29 nm; cP2) and monoclinic Al 13 Fe 4 (a = 1.549 nm, b = 0.808 nm, c = 1.248 nm; α = γ = 90°, β = 107.72°; mC102). The IQC phase was also found to be ordered from the existence (311111) superlattice reflection of IQC. The phase fraction of IQC phase increased (in comparison with the crystalline phases) on annealing of IQC-Sn powder milled powder at 800 °C. The nano quasi-crystalline and nano-crystalline nature of these IQC and crystalline phases in milled and annealed powders were observed through transmission electron microscopy. The nano-beam diffraction (NBD) of the annealed samples confirmed the presence of nearer to 5-fold symmetry corresponding to the IQC phase. The electrical and thermal transport properties of milled and annealed samples were studied. The electrical and thermal transport properties of annealed sample was higher than that of the milled IQC-Sn nanocomposite powders. The ratio of electrical and thermal conductivity for IQC-20Sn annealed sample was found to be the highest (σ/ κ ∼4704 SK/W). These findings suggest the possibility of using IQC-Sn annealed nanocomposites for potential application as thermoelectric materials. • The 40 h milled IQC-Sn nanocomposite have predominantly crystalline phases (i.e. B2 and Al 13 Fe 4 phase). • The milled IQC-Sn samples annealed at 800 °C leads to increase in the phase fraction of IQC phase. • The electrical and thermal transport properties of annealed samples were ∼100 times more than 40 h milled IQC-Sn. • Annealed sample shows higher ratio for σ/ κ (∼4704 SK/W) representing its suitability for thermoelectric applications. [ABSTRACT FROM AUTHOR]

Atomically thin boron nitride (BN) film has attracted increasing attention among two-dimensional materials for the potential application in electronics devices. The thermal properties of few-layer BN nanosheets (∼2.27 nm) on SiO 2 /Si substrates have been investigated without and with high- k Al 2 O 3 capping layer, using the temperature-dependent and polarized-laser power-dependent Raman spectroscopy measurements. Due to the effect of Al 2 O 3 capping layer, Raman spectrum illustrates the blue-shift of frequency from 1364.9 cm−1 to 1367.9 cm−1, and the first order temperature coefficient for E 2g mode of BN layers increases from −0.02243 cm−1/K to −0.06544 cm−1/K. Furthermore, the room-temperature thermal conductivity of BN with Al 2 O 3 capping layer is found to be 332.57 W/mK, which is much larger than that of BN without Al 2 O 3 capping layer (∼94.51 W/mK). The enhancement is attributed to the interface charges and compressive stress at the interface between BN and Al 2 O 3 capping layer, which has been clarified by the first principle calculations. This work is aimed at expanding the applications of BN materials and improving the performances of BN-based devices in thermal properties. • The few-layer BN sample (∼2.27 nm) was capped with a ∼5 nm Al 2 O 3 layer by ALD. • The Raman peak position of BN without and with Al 2 O 3 layer exists a blue-shift. • The room-temperature thermal conductivity of FLBN/Al 2 O 3 is improved to 332.57 W/mK. [ABSTRACT FROM AUTHOR]

This study aims to estimate effective thermal conductivities of metal matrix nanocomposites (MMNCs) containing carbon nanotubes (CNTs) using a new hierarchical micromechanical method. Nano-filler agglomeration made of CNTs into the MMNCs, frequently encountered in real engineering situations, is considered as the main novelty of this approach. Also, two important parameters, including CNT curvature and interfacial thermal resistance between the CNT and metal matrix are taken into account in the micromechanical modeling. The developed hierarchical approach is validated through the comparison with the experimental measurements available in the literature. When CNTs are not well dispersed into the metal matrix, by incorporating the interfacial thermal resistance, CNT curvature and agglomeration, the predictions are in good agreement with the experiment of MMNC thermal conductivities. The results reveal that the CNT agglomeration can dramatically decrease the MMNC thermal properties. It is confirmed that the key issues to enhance the thermal conductivity of CNT-reinforced MMNCs are homogeneous distribution of CNTs and decrease of CNT/metal interfacial thermal resistance. Also, it is observed that the MMNCs show a significant improvement of thermal conductivity by alignment of CNTs into the metal matrix. The effects of CNT volume fraction, diameter and length on the MMNC thermal conductivities are examined. • Thermal conductivity of CNT-metal nanocomposites with agglomeration is predicted. • A novel hierarchical micromechanical method is developed. • Predictions agree well with experimental data. • Agglomeration and interfacial resistance can decrease the thermal conductivity. [ABSTRACT FROM AUTHOR]

Using electrodeposition to prepare thermoelectric thin films enables the fabrication of energy-harvesting devices with low manufacturing cost. However, it is difficult to compute the thermal conductivity of these electrodeposited thin films owing to their large surface roughness. In this work, we prepared electrodeposited bismuth selenide (Bi 2 Se 3) thin films using hydrochloric acid (HCl) and nitric acid (HNO 3) solutions and measured the thermal conductivity using the 3ω method. The Bi 2 Se 3 thin films prepared using the HCl solution consisted of round grains with relatively large pores that reached the substrate appearing between the grains. In contrast, the Bi 2 Se 3 thin films prepared using the HNO 3 solution were composed of flake-like grains with the appearance of relatively small and shallow pores. As a result, the thermal conductivity could only be measured for the Bi 2 Se 3 thin films synthesized utilizing HNO 3 solution; however, the measured thermal conductivity was about 0.14 W/(m⋅K). The low value of thermal conductivity was attributed to their amorphous structure. To improve the electrical properties of Bi 2 Se 3 thin films, the electrodeposited samples were subjected to a thermal annealing treatment. An improvement in the electrical properties of the thin films was noticed with an annealing temperature of 300 °C; however, the thermal conductivity also increased to 0.76 W/(m⋅K). Therefore, the dimensionless quantity which represents the performance of the Bi 2 Se 3 thin film, ZT, was determined to be 0.08–0.09. Therefore, the effectiveness of the proposed method for preparing electrodeposited thin films while estimating the thermal conductivity and ZT was successfully demonstrated. Image 1 • Electrodeposited Bi 2 Se 3 films were fabricated on stainless-steel substrates. • The electrodeposition was performed using HCl and HNO 3 solutions with stirring. • The thermal conductivity of HNO 3 -prepared films can be measured using the 3ω method. • The thermal conductivity of the Bi 2 Se 3 film annealed at 300 °C was 0.76 W/(m∙K). • The dimensionless figure of merit was 0.09 for the Bi 2 Se 3 film annealed at 300 °C. [ABSTRACT FROM AUTHOR]

Using the tight-binding method based on density functional theory (DFT) calculations, the thermoelectric properties of pure and B/N doped carbon nanotubes (CNTs) are investigated in terms of temperature (T) and in the presence of external electric and magnetic fields. All thermoelectric properties for pure and doped structures increase with temperature and the increasing rate is stronger in the presence of the external fields. The electrical conductivity and heat capacity of pure CNTs is larger than doped structures. For pure and doped structures, the heat capacity increases linearly with T independent to the dopant atoms. In the presence of electric (magnetic) field, the electrical conductivity and heat capacity of pure CNT are smaller (larger) than that other. The thermoelectric functions are strongly dependent on the strength of applied electric field rather than electric field. • The electronic structure of CNTs are dependent on the dopant atoms and external electric and magnetic fields. • Energy gap reduction shows dependence on impurity and external electric (F) and magnetic (Π) fields. • The heat capacity Cv(T) and electrical conductivity σ(T) increase with temperature. • The σ(F = 0,Π = 0,T) and σ(F = 0,Π≠0,T) for pure CNT is larger than doped structures increase with temperature and field. • For pure and doped structures, the Cv increases linearly (parabollicly) with T independent to the dopant atoms. [ABSTRACT FROM AUTHOR]

To find high-performance ternary borides as the hard phase of the cermets, first-principles calculation was applied to systematically investigate the structure, mechanical, electronic and thermal properties of 26 ternary borides MⅠ x MⅡB x (x = 1 or 2). The phase stability and mechanical properties were evaluated by formation enthalpy and elastic constants. Debye temperatures were calculated to study the thermal conductivity, and the hardnesses of the candidates were predicted via the overlap populations calculation and hardness model. The results show that all the candidates possess thermodynamic and mechanical stability. Most of the MⅠ x MⅡB x (x = 1 or 2) exhibit a better ductility than WC, except Ta 2 FeB 2 , Mo 2 MnB 2 , Nb 2 CrB 2 , Nb 2 FeB 2 and Ti 2 ReB 2. Moreover, sorted from high to low, Nb 2 CrB 2 , Mo 2 CoB 2 , W 2 MnB 2 , Mo 2 FeB 2 , Ti 2 ReB 2 , NbFeB, MoCoB, Mo 2 NiB 2 , Nb 2 FeB 2 , and Mo 2 NbB 2 have a larger Debye temperature than WC. All the candidate ternary borides exhibit a lower hardness than WC, with the maximum hardness of 26.3 GPa for MoCoB. The analysis of electronic properties indicates that all the MⅠ x MⅡB x (x = 1 or 2) exhibit metallic, ionic and covalent hybrid properties. The calculated results are expected to provide guideline for developing ternary boride-based cermets or coating materials that may replace WC-Co cermet. • Ternary boride-based cermets may replace WC-Co. • The mechanical and thermal properties of 26 MⅠ x MⅡB x (x = 1,2) were investigated. • A novel high hardness and thermal conductivity MoCoB-Co cermet was proposed. • A scientific foundation for accelerated design of tungsten substitutable cermets. [ABSTRACT FROM AUTHOR]

Electrodeposition is considered as a cost-effective fabrication method for metal-diamond heat sink materials. However, the formation of the metal-diamond interface has not been addressed in detail to date although controlling the interfacial microstructures is crucial. In this study, we electrodeposited copper-diamond composite materials and observed that 66 μ m sized diamond particles decreased the thermal conductivity of copper whereas 420 μ m sized diamond particles increased the thermal conductivity. The differential effective medium (DEM) model analysis showed that the thermal boundary conductance values at the electrodeposited copper matrix-diamond interface were 1.3 MW/m2K and 3.1 MW/m2K when the diamond particle sizes were 66 μ m and 420 μ m, respectively. This discrepancy was attributed to the microstructure of the copper matrix in the vicinity of diamond particles, which was caused by particle size dependent current density distribution. These results show that particle size in electrodeposited composite materials can strongly affect the microstructure of the metal matrix. • Copper-diamond composite materials were produced by electrodeposition. • Copper-diamond thermal boundary conductance showed diamond particle size dependence. • Unexpected particle size effect on the microstructure of copper-diamond composites is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract Nanoscale oxide resistive switching structures have attracted widespread attention in connection with future logic, memory, neuromorphic computing, and storage structure applications. Resistive switching effects are usually assumed to be caused by conducting filaments (CFs), which are formed by metal diffusion, and their breaking across the insulating oxide between the metal electrodes. Understanding thermal transport in CF containing metal/oxide based structures is critical to determine whether these filaments exist. This paper reports phonon transport in Cu diffused aluminum oxide (AO) in a Cu/AO/Si resistive switching structure where Cu based CFs have formed locally as a result of electric breakdown. This was studied by measuring cross-plane thermal conductivity on CF containing AO layers from 100 to 500 K. Our results suggest that conferring thermal properties upon non-thermoelectric materials as a result of CF formation enables thermal conductivity to be controlled by CF density. Therefore, the proposed methodology, including a local probing method, will also help understand other physical properties of metal/oxide based resistive switching structures in the future. Graphical abstract Image 1 Highlights • We examined phonon transport of conducting filaments (CFs)-containing AO layer in AO-based resistive switching structure. • CF-containing AO layer exhibits 1.3–2.2 times higher thermal conductivity than that of unprocessed sample. • The density of the CFs plays a strong effect in enhancement of thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract The thermoelectric transport properties of artificially textured polycrystalline CrSiTe 3 samples have been investigated for elucidating their correlations with a crystal structure and the corresponding charge density distribution. We verified that the low mobility of 13–27 cm2 V−1 s−1 attributing poor electronic transport properties is originated from the discrete charge density distribution in the covalently bonded layer. Also, the modulation of thermal conductivity values from 3.5 to 5.4 W m−1 K−1 with varying the texture was confirmed in pristine CrSiTe 3. Thus, we suggest that the electronic and thermal transport properties of layer structured CrSiTe 3 are strongly correlated with crystallographic features. Graphical abstract Image 1 Highlights • Thermoelectric transport properties of CrSiTe 3 compounds. • Strong correlation between structure and thermoelectric properties. • The charge density distributions are strongly localized without no overlaps. • In-plane electronic transport properties depend on charge density distributions. • Anisotropy in thermal conductivity inherited from crystal structure. [ABSTRACT FROM AUTHOR]

Heat dissipation is a very important issue in the harsh thermal loads affecting the reliability of structures. In this study, the thermal conducting behavior of carbon nanotube (CNT)-reinforced metal matrix nanocomposites (MMNCs) has been analyzed using a micromechanical model based on the method of cell (MOC) approach. The critical role of interfacial thermal resistance between the CNT and metal matrix in the MMNC thermal conducting response has been extensively explored. Also, the effects of volume fraction, length, diameter and curvature of CNTs have been investigated. It has been found that forming a perfect CNT/matrix interface contact would enhance remarkably the overall thermal conductivities. Generally, the axial thermal conductivity of the CNT-reinforced MMNCs can be increased with (i) rising CNT length and (ii) using straight CNTs. Moreover, the transverse thermal conductivity of these nanocomposite materials are improved with (i) rising CNT diameter and (ii) using wavy CNTs. Besides, increasing CNT volume fraction leads to a significant increment in the effective thermal conductivities in the presence of a perfect bonding at the CNT/matrix interface. Effective thermal conductivities of the MMNCs estimated by the MOC approach have been compared with those predicted by the effective medium and Halpin-Tsai models. A quite good agreement has been observed between the predictions of the MOC approach and experimental data. • Thermal conducting behavior of MMNCs containing CNTs is analyzed. • A new version of MOC micromechanical approach is proposed. • Model predictions agree well with experimental measurements. • Interfacial thermal resistance has a damaging effect on MMNC thermal properties. [ABSTRACT FROM AUTHOR]

Abstract Zinc die casting alloys exhibit a pronounced aging process. This aging is caused by the diffusion and precipitation of the dissolved aluminum in the rich-zinc grain phase and is accelerated by an increase in temperature. In this work, we investigate the effect of temperature and aging in the zinc die casting alloy Zamak 5 by measuring the thermal diffusivity and heat capacity and also considering its micro-structure with the scanning electron microscope (SEM) and X-ray diffraction (XRD). Highlights • Measurements at zinc die-casting alloy Zamak 5. • Temperature and aging dependence of specific heat capacity and thermal diffusivity. • Determination of temperature and aging dependence of thermal conductivity. • Interpretation of aging effects in the micro-structure on the thermal diffusivity. [ABSTRACT FROM AUTHOR]

Abstract β -In 2- x Cu x S 3 (0 ≤ x ≤ 0.40) bulks were prepared by solid-state reaction followed by pulsed current sintering. For x ≤ 0.20, X-ray diffraction indicated the formation of single phase, while the secondary phase, Cu 2 S, was observed for the samples prepared at x = 0.30 and x = 0.40. The Cu-doping allowed us to optimize the power factor in range of whole measured temperature by reducing the low temperature electrical resistivity. With the significant reduction in lattice thermal conductivity, a maximum ZT of 0.51 at 700 K and an average ZT of 0.31 from 300 to 700 K were obtained for the sample with x = 0.05, which values are 0.3 and 1.2 times higher than that of pristine sample. Highlights • β- In 2- x Cu x S 3 bulks with high thermoelectric performance were prepared. • Both the electrical resistivity and lattice thermal conductivity reduced after Cu doping. • ZT ave is greatly enhanced after Cu doping. • Cu doping is an efficiently way to optimize the thermoelectric performance of β -In 2 S 3. [ABSTRACT FROM AUTHOR]

Abstract The thermoelectric properties of Sr 2 Si, Sr 5 Si 3 , and their composites are reported. Sr 2 Si-Sr 5 Si 3 composites were synthesized by partial decomposition of Sr 2 Si to Sr 5 Si 3 during spark plasma sintering. Semiconducting Sr 2 Si grains were surrounded by boundary regions composed of smaller grains of Sr 2 Si, metallic Sr 5 Si 3 , and semiconducting Sr 3 SiO. Addition of the Sr 5 Si 3 phase reduced the electrical resistivity from 1.69 × 10−3 Ωm to 6.45 × 10−5 Ωm at room temperature, which corresponded to the samples having no and the maximum amount of the Sr 5 Si 3 phase, respectively. The electrical resistivity decreased; however, the Seebeck coefficient slightly increased to 157 μV/K at 773 K, and the thermal conductivity was approximately constant. Therefore, the power factor and ZT monotonically increased with an increase in the amount of the Sr 5 Si 3 phase in the composite samples, which confirmed almost no effect resulted from the Sr 3 SiO phase. A low thermal conductivity was demonstrated by Sr 2 Si (ca. 1 W/mK at 776 K), which resulted from weaker atomic bonds, heavier atomic mass, greater atomic volume, and a greater number of atoms in the unit cell. A further enhancement of ZT can be achieved for higher amounts of Sr 5 Si 3 and at higher temperatures. Graphical abstract Image 1 Highlights • Thermoelectric properties of Sr 2 Si, Sr 5 Si 3 , and their composites were investigated. • Remarkable reduction in ρ was observed due to the presence of Sr 5 Si 3 phase. • Simultaneous increase in S and σ was observed. • The lower κ was largely unaffected by the presence of metallic Sr 5 Si 3 phase. • The PF and ZT increased almost linearly with an increased amount of Sr 5 Si 3. [ABSTRACT FROM AUTHOR]

Abstract In 2 Se 3 nanostructures have attracted much attention due to their potential applications in diverse areas, such as solar energy conversion, thermoelectric power generation, phase change random access memories, photodetectors, and optoelectronics in the visible region. In the present work, we have fabricated various In 2 Se 3 nanostructures on SiO 2 /Si substrate using a simple and single-step physical vapor deposition (PVD) method, without using metal seed layer on the substrates. Morphology, structure and phase of the as-grown In 2 Se 3 nanostructures have been carried out using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. In addition, we have also explored thermal properties of In 2 Se 3 nanostructures on SiO 2 /Si substrate using temperature and power dependent Raman spectroscopy. Further, the thermal conductivity of nanoparticles, nanospheres, and rod like flowers at room temperature were found to be ∼37.6, ∼39.5, and ∼15.6 W/m-K, respectively. This work suggests an effective way to form various novel nanostructures, opening up a new scenario to understand the vibrational properties and electron-phonon interactions of In 2 Se 3 nanostructures. Graphical abstract Image 1 Highlights • A simple and single step PVD method was used to grow various In 2 Se 3 nanostructures. • Temperature and power-dependent Raman study was done on various In 2 Se 3 nanostructures. • Thermal conductivity of various In 2 Se 3 nanostructures was evaluated. • p-p and e-p interactions have been analyzed with Raman measurements. [ABSTRACT FROM AUTHOR]

Abstract In this work, we report that the high performance of SnTe could be realized by enhancing electrical transport properties (power factor) and reducing thermal conductivity through stepwisely introducing elements of Sb, In and Se. We found that Sb and In co-doping can enhance Seebeck coefficients in the broad temperature range via optimizing carrier density and introducing resonant state, respectively. Moreover, nanostructures could be formed when the Sb content beyond the solubility limit in SnTe matrix, which coupled with point defects from In and Se alloying result in a very low (lattice) thermal conductivity through the enhanced phonon scattering from defects and grain boundaries. A peak ZT ∼1.0 at 923 K can be achieved with the enhanced power factor and reduced thermal conductivity. Accordingly, the average ZT value increases from ∼0.20 for undoped SnTe to ∼ 0.60 for multiple-doped SnTe (Sn 0.823 Sb 0.17 In 0.007 Te 0.98 Se 0.02) over 300–923 K, generating a high calculated conversion efficiency ∼ 11%. Present results indicate the high performance of SnTe can be obtained through stepwisely optimizing strategy in both electrical and thermal transport properties. Highlights • A stepwisely enhancing in thermoelectric transport properties were achieved in p -type SnTe. • Power factor of p -type SnTe was enhanced from ∼3.4 μW cm−1 K−2 to ∼ 11.7 μW cm−1 K−2 at 300 K through Sb and In co-doping. • κ lat of p -type SnTe was reduced from ∼3.4 Wm−1K−1 to ∼ 1.4 Wm−1K−1 at 300 K through Sb, In co-doping, and Se alloying. • ZT ave of p -type SnTe is distinctly enhanced from ∼0.2 to ∼0.6 over 300–923 K. [ABSTRACT FROM AUTHOR]

Abstract In this investigation, aluminum matrix composites with different graphite contents (6%, 12% and 18% volume fraction) are prepared using hot-press and powder metallurgy method. The distribution of graphite particles in the matrix is investigated by optical microscope. Density of the composite samples are examined and it is seen that increasing the graphite content decreases the densification due to graphite content and particle size. Results reveal that thermal conductivity of Al-18%G composite sample increased to 252 W/m.K. Similarly, results show that by compositing coefficient of thermal expansion (CTE) in 50–250 °C range decreased to 19.6 ppm/K. Finally, thermal stability of Al-18%G sample is evaluated by exposing to 1, 20, 50 and 100 thermal cycles. Due to difference between CTE of matrix and graphite, cracks propagate through the reinforcement/matrix interface and results in sample failure. Calculated CTE values are highly consistent with theoretical results of geometrical, Maxwell and Maxwell-Eiken models. Highlights • No crack, porosity or Al-carbide was found at the interface of the Al-G composites. • Density of composite samples was very close to theoretical value. • Samples microhardness reduced by 19 HV by increasing the graphite content to 18%. • A model was suggested based on graphite geometrical and physical properties. • By rising the graphite content to 18%, thermal conductivity increased to 252 W/m.K. [ABSTRACT FROM AUTHOR]

Abstract Copper micro-flakes were encapsulated with in situ catalytically grown graphene and then assembled into graphene/Cu (Gr/Cu) laminated composite under pressure at high temperature. The thermal conductivity (TC) and coefficient of thermal expansion (CTE) of the composites were investigated systematically. Although in situ catalytic growth graphene can avoid structural damage in a usual mechanical alloying process and is beneficial for improving interfacial bonding, the Gr/Cu laminated composites show decreased TC in both directions compared to the pure Cu matrix prepared by the same process. The composites exhibit anisotropic thermal properties owing to their laminated architecture and two-dimensional character of graphene. Given a volume fraction of graphene, the cross-plane TC of the Gr/Cu composite is lower than the in-plane TC because of more multilayer-graphene/copper interfaces and low cross-plane TC of graphene. Although the fraction of graphene is only 0.75 vol%, the Gr/Cu composite has a significantly lower cross-plane CTE than the pure Cu matrix in a wide temperature range. Graphical abstract Image 1 Highlights • Thermal properties of in-situ catalytically grown graphene/Cu composites are studied. • Anisotropic thermal properties are analyzed in graphene/Cu laminated composite. • Low fraction of graphene can significantly reduce thermal expansion coefficient. [ABSTRACT FROM AUTHOR]