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The effects of Ta doping on the thermal and electrical properties of SnO 2 varistors were researched. The results showed that the thermal conductivity is 2.01 WK−1m−1, the nonlinearity coefficient is 43, and the leakage current density is 0.7 μA/cm2 when the Ta doping level reaches 0.2 mol%. According to the measurement results of the EPR, SEM/EDS, and XRD, the Ta dopant can reduce the oxygen vacancy concentration, which was generated during the sintering. The decline of the oxygen vacancy concentration reduces the phonon scattering, then the thermal conductivity of the varistors is improved. On the other hand, the reduction of the oxygen vacancy concentration elevates the barrier height, so the nonlinearity coefficient is improved and the leakage current density is declined. [ABSTRACT FROM AUTHOR]

Exploring new applications of negative thermal expansion (NTE) materials is a recent research hotspot. In this work, the IV A element Sn was used to tailor the thermal expansion and dielectric properties of NTE material ZrMgMo 3 O 12 , and the samples Zr 1–x Sn x MgMo 3 O 12 (x = 0.05, 0.10, 0.15, 0.20, 0.25) can be used in the field of high-frequency dielectric ceramics. Both the substitution amount of Sn and sintering temperature have a certain effect on the properties of Zr 1-x Sn x MgMo 3 O 12. The coefficients of thermal expansion (CTE) can be adjusted between near zero thermal expansion (ZTE) (−0.24 × 10−6/K−1) and NTE (−8.16 × 10−6/K−1) and become larger toward negative as the amount of Sn increased under the same sintering temperature. The dielectric constants of Zr 1-x Sn x MgMo 3 O 12 can be adjusted in the range of 130∼155, which are about 25 times than ZrMgMo 3 O 12. The dissipation factors of Zr 1-x Sn x MgMo 3 O 12 were adjustable between 4.37 × 10−4 and 5.54 × 10−4, meeting the application requirements of high-frequency dielectric ceramics. This research shows that Sn can adjust the thermal expansion properties and significantly improves the dielectric properties of ZrMgMo 3 O 12 , so that Zr 1-x Sn x MgMo 3 O 12 materials have high value in the field of high-frequency dielectric ceramics. [ABSTRACT FROM AUTHOR]

In present work, high entropy (MoTaTiVW)C X ceramics with different carbon stoichiometries (X = 3–6) were produced using spark plasma sintering. The microstructure, mechanical properties, and thermal properties of (MoTaTiVW)C X with different carbon stoichiometries were studied. At X = 3, the carbon deficiency resulted in a multiphase structure of the sample, (MoTaTiVW)C 3 with a Mo-rich carbide phase. At X = 3.5, the single-phase rock salt structure was formed despite carbon vacancies of up to 30 %. The relative density of (MoTaTiVW)C X gradually decreases as the carbon stoichiometry increases from X = 3 to X = 6. The concentration of carbon vacancies affects the sintering activation energy, which can enhance mass transfer and promote the densification process. The Vickers hardness of (MoTaTiVW)C X shows an overall decreasing trend as the carbon stoichiometry increases from X = 3.5 to X = 6, peaking at 20.4 ± 0.4 GPa at X = 3.5. The fracture toughness increases and then decreases, peaking at 4.4 ± 0.2 MPa m1/2 at X = 4. The thermal conductivity of (MoTaTiVW)C X gradually increases, then decreases and finally increases with the increase of carbon stoichiometry. At room temperature, the maximum value of thermal conductivity is 6.35 ± 0.29 W/m·K of (MoTaTiVW)C 5 and the minimum value is 5.32 ± 0.35 W/m·K of (MoTaTiVW)C 5.5. At 1000 °C, the thermal conductivity of (MoTaTiVW)C X ranges from 15.94 ± 0.37 W/m·K to 19.56 ± 0.45 W/m·K. As the concentration of carbon vacancies decreases, the decrease in point defect concentration will reduce the degree of lattice distortion, thereby reducing phonon scattering and affecting thermal conductivity. The study suggests that carbon stoichiometry can be used to adjust the microstructure, mechanical properties, and thermal properties of high entropy carbide ceramics. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. The aim of this study was to determine the individual and combined effects of supplementing fat with whole-cracked rapeseed (FAT), nitrate (NITRATE), and 3-nitrooxypropanol (3-NOP) on compositional and functional properties of milk fat. An 8 × 8 incomplete Latin square design was conducted with 48 lactating Danish Holstein cows over 6 periods of 21 d each. Eight diets were 2 × 2 × 2 factorially arranged: FAT (30 or 63 g crude fat/kg DM), NITRATE (0 or 10 g nitrate/kg DM), and 3-NOP (0 or 80 mg 3-NOP/kg DM), and cows were fed ad libitum. Milk samples were analyzed for general composition, fatty acids (FA) and thermal properties of milk fat. Milk fat content was decreased by supplementing fat but increased by 3-NOP. The changes in FA composition were mainly driven by the FAT × 3-NOP interaction. Fat supplementation shifted milk FA composition toward a lower content of SFA and greater contents of MUFA and PUFA, whereas these effects became smaller in combination with 3-NOP. However, 3-NOP had no effects on SFA, MUFA, or PUFA in low-fat diets. Fat supplementation lowered solid-fat content in milk fat because of the decreased SFA content. The onset crystallization temperature of milk fat was decreased by 3-NOP when supplemented in low-fat diets. According to the FAT × 3-NOP interaction, supplementation of fat without 3-NOP shifted the peak temperature of the low-melting fraction of milk fat toward low temperature as a result of a decreased proportion of C16:0 and increased proportions of C18:1 cis -9, C18:1 trans -11, C18:2 cis -9, and CLA cis -9, trans -11. In conclusion, no additive effects were observed among FAT, NITRATE, and 3-NOP on chemical and thermal properties of milk fat, and fat supplementation largely changed milk FA composition, which in turn affected the thermal properties of milk fat. [ABSTRACT FROM AUTHOR]

Gadolinium Zirconate nanoparticles were synthesized by Co-precipitation and Ball milling techniques. In this study, the effect of the synthesis technique and calcination temperature on the structural, morphological and thermal properties were investigated. The thermal properties examined showed that the GZ nanoparticles obtained from CP technique suffered two-fold weight loss as compared to BM technique. The SEM results revealed the formation of agglomerated particles. However, TEM results confirms the formation of nanoparticles of 10.5 nm and 8 nm by BM and CP techniques respectively. GZ particles obtained through CP technique showed better uniformity of particle size over BM technique. The functional groups of the nanoparticle were studied using FT-IR spectroscopy analysis. The XRD results confirm the formation of defect-fluorite structure and pyrochlore structure for the samples calcined at 1100 °C and 1400 °C (BM) respectively. The formation of the corresponding structures was further confirmed by Raman Spectroscopy. The thermal conductivity of the nanoparticle produced by ball milling and co-precipitation technique is almost same. As compared to NiCrAlY and uncoated substrate materials, the micro hardness of the GZ coatings has the maximum hardness of 594.6 HV, indicating the improved hardness behavior of TBC system. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (cBN) has been used as a tool material for several decades due to its high hardness and thermal stability. Various binders are commonly added to cBN to synthesise cBN composites for better cutting performance. However, most studies have only investigated properties such as hardness and bulk modulus, without comprehensively studying elastic properties through experiments. In this study, the sound velocities and elastic properties of cBN with AlN binder were determined by using the ultrasonic interferometry technique. The bulk and shear moduli with their pressure dependence were determined as B 0 = 351 (3) GPa, G 0 = 344 (3) GPa, B 0 ′ = 4.32 (4) and G 0 ′ = 1.74 (2) using the finite strain equation-of-state approaches. Elasticity-related thermal properties, such as Debye temperature, Grüneisen parameter, thermal conductivity and coefficient of thermal expansion were also estimated. The results show that the elastic properties of the cBN composite with vol. 8.8% AlN-binder are comparable to the pure cBN compact. Additionally, the thermal conductivity and coefficient of thermal expansion have little effect on cBN composite with AlN binder compared to pure cBN. [ABSTRACT FROM AUTHOR]

As the research for advanced materials suitable for high-temperature uses continues, the need for oxide ceramic micro-nanofibers with outstanding mechanical and thermal properties becomes increasingly important. By incorporating two types of magnesium sources, specifically Mg(CH 3 COO) 2 ·4H 2 O and MgCl 2 ·6H 2 O, into the precursor, a range of fibers made of magnesium silicate ceramics was produced through electrospinning. X-ray diffraction (XRD) analysis verified that the resulting multiple phases included MgO, MgSiO 3 , Mg 2 SiO 4 , and amorphous SiO 2 , with the phase composition being affected by the diffusion reaction of Mg ions. The fibers produced using the dual-precursor method maintained a stable morphology with a uniform and compact structure after undergoing high-temperature treatments ranging from 1000 to 1200 °C. This study is the first to report the tensile strength of magnesium silicate fibrous membranes, which was found to be 1.54 ± 0.27 MPa and 1.21 ± 0.73 MPa after heat treatment at 800 °C and 1000 °C, respectively. Furthermore, these fibrous membranes demonstrated dependable thermal insulation properties within the testing range of 500–1000 °C, along with a low thermal conductivity at room temperature of 0.0301–0.0306 W m−1·K−1. Characterized by their impressive mechanical strength and high temperature stability, magnesium silicate ceramic micro-nanofibers show significant potential for various applications in the targeted field. [ABSTRACT FROM AUTHOR]

Li 2 O–ZnO–B 2 O 3 -WO 3 (LZBW) sealing glasses for Si substrates were prepared and the effect of WO 3 on the structure, thermal properties, and sintering behaviour was investigated. As the WO 3 increases from 0 to 12 mol%, the glass transition temperature and softening temperature reach the lowest values of 448 °C and 479 °C, respectively, at which time the glass network has the lowest degree of polymerization. The thermal expansion coefficient increases from 6.959 × 10−6/°C to 8.476 × 10−6/°C with increasing WO 3 contents. It is verified that the introduction of WO 3 can effectively improve the conductivity. The sealing property of the glasses was evaluated by the wetting angle of the glasses after co-sintering with Si substrate for 10 min at 860 °C, and the 25Li 2 O-7ZnO-2.7Bi 2 O 3 -1.3P 2 O 5 -55B 2 O 3 -9WO 3 glass had the minimum wetting angle of 34.07°. The excellent thermal properties, conductivity, and wetting behaviour of the LZBW glasses make it a potential material as a binder material for positive silver pastes. [ABSTRACT FROM AUTHOR]

This work investigates the behavior and properties of corundum and mullite ceramics at high temperatures and during very long exposures in a controlled atmosphere. The motivation of the work lies primarily in advanced applications in nuclear energy technology, specifically in the search for materials for helium-cooled reactors of the 4th generation. The studied ceramic samples Al63, Al70, Al76, Al96, Al100, where the number indicates the mass percentage of Al 2 O 3 , were exposed for 1000 h at a temperature of 900 °C in gaseous atmospheres of helium, nitrogen and air. The properties of the exposed and unexposed samples were evaluated by measuring the bending strength at room temperature (CMOR), hot modulus of rupture at high temperature (HMOR), and isothermal creep, BET method, and using electron microscopy. The color changes induced by the reducing atmosphere and temperature were also interpreted using a simple thermochemical model. The CMOR measurement results show that all ceramic samples do not significantly change their properties due to long-term exposure. The detected deviations in the exposed samples from the unexposed ones can be considered random caused by the inherent heterogeneous structure. A similar conclusion also applies in the case of the HMOR measurement results, except for the results for the Al63 sample, where the drop in the strength of the exposed samples by approx. 37 MPa (20 %) may be related with the highest proportion of polyvalent oxide admixtures of all studied ceramics, i.e. 1.01 wt % Fe 2 O 3 and 0.52 wt % TiO 2. The change in color indicates that the iron and titanium present are being reduced. However, none of the conducted experiments indicate that changes in the redox state associated with the formation of oxygen vacancies would significantly reduce strength at high temperatures or increase creep in mullite ceramics. [ABSTRACT FROM AUTHOR]

The properties of rare-earth (RE) monosilicates can be regulated by solid solution engineering based on the mixture rule. The combination and number of RE principals are critical factors for better performances. In the present study, four single-phase equimolar multicomponent RE-monosilicate solid solutions including (Dy 1/3 Er 1/3 Yb 1/3) 2 SiO 5 , (Ho 1/3 Er 1/3 Yb 1/3) 2 SiO 5 , (Y 1/4 Er 1/4 Tm 1/4 Lu 1/4) 2 SiO 5 and (Dy 1/4 Er 1/4 Tm 1/4 Yb 1/4) 2 SiO 5 were synthesized by solid-state reaction and hot-pressing method. The microstructures, thermal and mechanical properties, and corrosion resistance to high-temperature water vapor were systematically investigated. Compared to the single-principal and ternary RE-monosilicates, the quaternary RE-monosilicates exhibited lower thermal conductivity of 1.32 Wm−1K−1 at 400 °C, matched thermal expansion coefficients (3.3 × 10−6/oC ∼ 5.8 × 10−6/oC from 200 °C to 1000 °C) with SiC, and much lower weight loss during water vapor corrosion. The results indicate that the increase of the RE element number can promote the grain growth, lower the thermal conductivity and thermal expansion coefficient, and enhance corrosion resistance. [ABSTRACT FROM AUTHOR]

An estimated 30 % (∼11 million metric tons/year) of copper slag is still landfilled globally. Fayalitic copper slags are well-characterized, and they can be recycled into multiple safe end-products. Conversely, the major type of copper slag produced in Europe is lead-rich and warrants a deep understanding of phases present in it, properties, adverse environmental implications, and potential recycling strategies. The objective of this study is to thoroughly investigate such industrial slags by XRF, XRD, Mössbauer spectroscopy, SEM-EDS, novel automated image analysis using Aphelion, hot stage microscopy (HSM) and assess prospects for their valorization. These industrial slags were found to contain 26.1–50.5 wt% PbO, 3.4–5.4 % As 2 O 5 (both hazardous solid wastes), 5.7–42 % CuO (present partly as Cu 2 O, an irritant), 3.2–18.2 % Fe 2 O 3 , 14–15.9 % SiO 2 and oxides of chromium, cobalt (both carcinogenic), zinc and nickel (both toxic to aquatic life). The limitation of Rietveld XRD for glass quantification was overcome by newly-developed automated SEM-image processing which revealed that all three slags consisted of a lead silicate glass (36.3–65.8 vol%). Strikingly, rarely published arsenic- and lead-based compounds like (Ca,Pb) 4 As 2 O 9-x , (Ca,Cu) 2 PbO 4-x and Pb 3 Ca 2 Si 3 O 11 were found when slag's PbO/CuO was 0.6, and Ca 3 As 2 O 8 -Pb 2 SiO 4 formed when PbO/CuO equaled 9. The challenge of toxicity and landfilling can be overcome as these slags have high potential to be used for recovery of copper, cobalt, and lead. Radioactive waste immobilization glasses, gamma-ray shielding concrete and glass-ceramic consumer products may also be prepared from them. HSM revealed that a higher PbO/CuO ratio results in lower melting point and smaller melt contact angle indicating such slag can be useful for manufacturing recycled ceramics but corrosive towards refractories in copper converter. [ABSTRACT FROM AUTHOR]

The pyrochlore oxide La 2 Hf 2 O 7 (LHO) has attracted extensive attention in thermal management applications. Accurate determination and comprehensive understanding of thermal conductivity (κ) stand as imperative prerequisites for the effective utilization and manipulation of LHO in various applications. In this study, with the assistance of machine learning interatomic potential, we investigate the microscopic mechanisms of phonon thermal transport in LHO crystals. Our findings show that the thermal transport in LHO defies a precise explication through the conventional framework of the Boltzmann transport equation (BTE) due to the emergence of diffusive phonon modes, engendered by strong anharmonicity. Using the state-of-the-art dual-phonon model incorporating both propagating and diffusive modes, we successfully reproduce the experimentally measured results in both magnitude and temperature dependence. It is also shown that the thermal conduction in LHO crystals is dominated by the propagating modes at low temperatures while by the diffusive modes at high temperatures, which synergistically lead to a low κ for LHO crystals. The novel insights into phonon thermal transport provide a stepping stone for regulating the thermal transport properties of LHO crystals. [ABSTRACT FROM AUTHOR]

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

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

(KMg)3+ co-doped Sc 2 W 3 O 12 ceramics have been prepared via co-precipitation method. Effects of (KMg)3+ co-doping amount and sintering temperature on the phase constitution, microstructure, morphology, and negative thermal expansion (NTE) performance of K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1.25) ceramics were studied. Results indicate that: Sc3+ cations can be substituted by (KMg)3+ dual-cations and a composition-induced structural phase transition was observed in K x Mg x Sc 2- x W 3 O 12. For x ≤ 0.25, orthorhombic Sc 2 W 3 O 12 gradually changed into hexagonal K x Mg x Sc 2- x W 3 O 12 and coexisted. Single phase K x Mg x Sc 2- x W 3 O 12 with hexagonal symmetry can be prepared for 0.25 < x ≤ 1. When x ≥ 1.25, (KMg)3+ substitution reaches its solid solution limit in Sc 2 W 3 O 12 , and impurity MgWO 4 formed in the samples. As co-doping amount x increased, the NTE performance of the K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1) ceramics gradually enhanced. The coefficient of thermal expansion (CTE) of K x Mg x Sc 2- x W 3 O 12 (0 ≤ x ≤ 1) ceramics enhanced from −2.14 × 10−6 °C−1 to −19.68 × 10−6 °C−1 in 30–700 °C. With the increase of sintering temperature from 800 to 1100 °C, the grains grew up and the density of the K 0.75 Mg 0.75 Sc 1.25 W 3 O 12 ceramics increased as well, and the NTE performance was also improved. The linear CTE of K 0.75 Mg 0.75 Sc 1.25 W 3 O 12 ceramics enhances from −2.15 × 10−6 °C−1 to −14.70 × 10−6 °C−1 in 30–700 °C. [ABSTRACT FROM AUTHOR]

Lightweight phenolic matrix composites are highly potential in ablative thermal protective materials for future aerospace vehicles, and hybrid modification is considered as one of effective ways to improve the oxidation and ablation resistance of phenolic matrix. Herein, the co-continuous silica zirconium hybrid phenolic resin (SZRx) was synthesized, which can be used to prepare lightweight ablation resistant aerogel composites by the sol-gel method. The SZRx aerogel showed stable porous structure and excellent hydrophobicity, and the silicon zirconium hybrid greatly improved the high temperature carbon residue and oxidation resistance of phenolic resin. The SZRx aerogel composites also possessed excellent integrated characteristics of heat protection and insulation, with a linear ablation rate as low as 0.032 mm/s and a back temperature below 200 °C. The synergistic effect of silicon and zirconium formed the multiphase ceramic layer (C, SiO 2 , SiC and ZrO 2) with the sea-island-like structure on the surface of the composite material, which can effectively resist high-temperature ablation and aerodynamic exfoliation. This can indicate that silicon zirconium dual element hybrid phenolic resin is the highly competitive matrix for lightweight and ablation resistant composite materials. [Display omitted] [ABSTRACT FROM AUTHOR]

This work describes the preparation and properties of a novel category of thermosetting microwave absorbing composite materials. The composites were prepared by a simple solution casting process, employing high temperature resistant polysilylaryl-enyne (abbreviated as PSAE) resin as matrix and perovskite CaMnO 3 (abbreviated as CMO) ceramic filler as absorbent filler. The microstructure, electromagnetic, wave absorbing and thermal properties of the CMO-PSAE composites were all examined. The results showed that the increasing fraction of CaMnO 3 filler not only densified the microstructure of the composites, but also greatly improved their temperature resistance, thermal conductivity and wave absorption properties. The CMO-PSAE composite doped with 50 vol% CaMnO 3 ceramic filler showed the strongest ability to absorb electromagnetic waves, with an effective absorption bandwidth (EAB) of 4.16 GHz and a minimum reflection loss is −53.01 dB. Besides, the thermal conductivity of the composite reached 1.106 W/(m·K). Furthermore, this composite material has exceptional thermal resistance, with the highest T d5 reaching 650 °C. Composites with varying doping levels can be used for specific performance needs in practical scenarios. Thus, such novel CMO-PSAE composites exhibit potential applications in the electromagnetic countermeasure field under high-temperature environments. [ABSTRACT FROM AUTHOR]

The order-disorder transition (ODT) of RE zirconate (RE 2 Zr 2 O 7) has received much attention due to its potential applications in the design of thermal barrier coatings (TBCs). A series of high entropy RE zirconates (RE = La, Sm, Gd, Er and Lu) were designed and synthesized in order to regulate the fluorite-pyrochlore phases, and to investigate the effect of phase composition on the microstructures and performances. The results showed that the sintering temperature, as well as equivalent ion radius, played an important role in regulating the phase transformation of fluorite-pyrochlore. The coexistence of pyrochlore-fluorite phases not only can result in the decrease in grain size but also increased the lattice strain of each phase, thereby enhancing the phonon scattering and contributing to the reduction in the thermal conductivity. The CMAS corrosion resistance was mainly related to phase compositions, and the thicknesses of reaction layer decreased gradually with the increasing fluorite phase content. The results will provide theoretical guidance for the microstructural design of high entropy RE zirconates as next generation TBC materials in future. [ABSTRACT FROM AUTHOR]

Dy 2 O 3 –Sm 2 O 3 co-doped transparent glass ceramics (GCs) containing NaBi(WO 4) 2 crystalline phase were prepared by melt-curing-crystallization method. The optimal heat treatment condition is 580 °C/2 h. The optimum incorporation concentration of Dy 2 O 3 is 0.4%, exceeding which a quenching phenomenon dominated by quadrupole-quadrupole interactions emerges. Meanwhile, when the concentration of Dy 2 O 3 was fixed, the chromaticity coordinate of the sample moved the cool white light region to the warm white light region as the concentration of Sm 2 O 3 increased. The temperature-dependent emission spectra of the 0.4% Dy 2 O 3 -0.7% Sm 2 O 3 co-doped GC samples show that emission intensity at 575 nm at 185 °C still reaches 80% of the room temperature. The thermal quenching activation energy was 0.1537 eV and the activation energy after the addition of Mo6+ was 0.1957 eV. This study indicates that Dy 2 O 3 –Sm 2 O 3 co-doped GCs containing NaBi(WO 4) 2 crystalline phase can achieve light-color tunable emission, which is potentially valuable for solid-state color rendering and illumination applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • CNTs-related composite PCMs are categorized in a new way: CNTs are usd as nanoadditives, porous supporters, and secondary network. • The research progress in the mechanism of heat transfer and phase transition of CNTs-related composite PCMs is introduced in detail. • In-depth insights into the micro-mechanism of heterogeneous interactions induced by CNTs are revealed. • The current challenges of designing CNTs-related composite PCMs are summarized. With the merits of inherent physicochemical properties of hollow structure, high mechanical strength, thermal stability, ultrahigh light absorption capacity, and ultrahigh thermal conductivity, carbon nanotubes (CNTs) are extensively used to enhance the thermal storage capabilities of solid–liquid phase change materials (PCMs). Interestingly, CNTs can act as thermally conductive additives and supporting skeletons when marring with PCMs. The state-of-the-art reviews on PCMs pay attention to carbon-based porous composite PCMs or nanoparticle dispersed PCMs, CNTs-derived PCMs only share a small part, lacking of a comprehensive review for multifunctional CNTs compounded PCMs. Herein, focusing on the enhancement effects of CNTs on PCMs, we retrospectively describe composite PCMs with a novel category way, by using CNTs as nanoadditives, porous supporters, and secondary network. We emphasize the micro-mechanism of heterogeneous interactions induced by CNTs: crystallization behavior, interfacial thermal resistance, thermal conductivity, phonon transport. Simultaneously, we provide in-depth insight into relationship between micro structural and thermal properties of CNT-derived PCMs. As a result, some different pathways of modern utilization based on the improved PCMs are presented. Finally, we outline the current challenges of designing CNTs to enable advanced functional thermal storage materials. The review aims to inspire clever use of CNTs into PCMs for targeted applications. [ABSTRACT FROM AUTHOR]

The present research article demonstrates the dispersion of boehmite (BHM) nanoparticles into sericin (SER) from silk industry waste with polyvinyl alcohol (PVA) to enhance the optical, mechanical, thermal and electrical characteristics of PVA/SER blend nanocomposites prepared by a simple green synthesis. Techniques such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV visible spectroscopy, field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out for the characterization of the prepared composites. XRD revealed the increased crystallinity of the polymer blend by the reinforcement of BHM. The existence of intermolecular interactions in the blend composite was confirmed by FTIR and UV spectroscopy. The optical bandgap energy of the biopolymer blend decreases with the inclusion of BHM. The SEM and HR-TEM confirmed the homogeneous dispersion of BHM in the blend at 5 wt% loading. The glass transition temperature and thermal stability of the blend nanocomposites were significantly improved by the inclusion of BHM was deduced from DSC and TGA. The dielectric constant and AC conductivity were remarkably increased with the reinforcement of nanoparticles. The activation energy obtained from AC conductivity decreased with temperature. The mechanical properties of the blend nanocomposites (hardness, tensile strength and Young's modulus) were greatly increased in presence of BHM. The 5 wt% sample has the highest tensile strength, Young's modulus, dielectric constant, AC conductivity and optical properties, allowing it to be used to make optoelectronic devices with better charge-storing capacity and flexible-type electrochemical gadgets. [ABSTRACT FROM AUTHOR]

In this study, composite phase change materials (CPCMs) comprising hexadecylamine (HDA) (C 16 H 35 N), disodium hydrogen phosphate dodecahydrate (DHPD) (Na 2 HPO 4 ·12H 2 O), and expanded graphite (EG) were prepared using the demulsification method. These CPCMs exhibit high latent heat and stable thermal properties. This approach effectively mitigates the issues of substantial supercooling and poor thermal conductivity commonly associated with DHPD and HDA. Additionally, the inclusion of EG imparts superior morphological stability to the CPCMs. The HDA/DHPD/EG CPCMs demonstrated robust thermal and morphological stability at temperatures below 100 °C. Their latent heat reached up to 221 J/g and remained stable at this value even after 50 cold-heat cycles, thereby indicating excellent cycling stability. When EG was incorporated at 2 wt%, the thermal conductivity of the HDA/DHPD/EG CPCMs increased to 0.751 W/(m·K), indicating that the three-dimensional network structure of EG facilitates heat conduction and offers exceptional photothermal conversion capabilities, with a photothermal conversion efficiency of up to 97.1 %. The aforementioned results highlight the promising potential of the prepared CPCMs for applications in low-temperature waste heat recovery. [ABSTRACT FROM AUTHOR]

One of the challenges facing our current and future generations is the effective management of energy and its acquisition through more sustainable means. One solution is using materials capable of generating energy from temperature differences. Construction materials could be the answer, as they are already integrated into structures and have good thermoelectric properties. Geopolymers, emerge as a promising candidate due to their enhanced sustainability compared to alternative materials. Our research explored the use of geopolymers for electricity generation from heat. To minimize the usage of kaolin, we incorporated 50 % of two mining residues obtained from old mines located in Portugal. This approach optimizes the utilization of mineral resources and mitigates the environmental impact. Various methods were used to characterize this material, such as X-ray diffraction, simple compressive strength tests and evaluation of thermoelectric properties, such as the Seebeck coefficient and figure of merit. The geopolymers tested exhibit semiconductor characteristics, demonstrating poor heat conduction due to their low thermal conductivity. Regarding thermoelectric properties, these materials display N-type behavior, with a Seebeck Coefficient between −643 μV/°C and −2760 μV/°C. These findings underscore the advantages of utilizing this sustainable material for the widespread implementation of energy management in buildings on a large scale. [ABSTRACT FROM AUTHOR]

BiCuSeO, an oxide thermoelectric material with a superlattice structure, presents the advantages of affordability, low toxicity, and environmental friendliness. However, its intrinsic low electrical conductivity has impeded its possible applications. To address this challenge, we put tiny PbZr 0.52 Ti 0.48 O 3 (PZT) with varying weight percentages (x = 0, 5, 7, 9, 11) into BiCuSeO (BCSO) to fabricate thermoelectric nanocomposites. Through the spark plasma sintering process, PZT particles underwent in-situ decomposition, generating nano-sized second phases such as PbO 2 , TiO 2 , and PbZrO 3 , which are homogenously distributed within BCSO matrix (validated by XRD and TEM). The introduced PbO 2 , TiO 2 , and PbZrO 3 second phases served a dual purpose: inhibiting the grain growth of BCSO and introducing additional nano-grain boundaries. This resulted in more effective phonon scattering sites, thereby reducing lattice thermal conductivity. Simultaneously, the Pb element derived from PZT decomposition was doped into the Bi site of the BCSO matrix, causing a reduction in the band gap of BCSO from 0.49 eV to 0.388 eV and a significant increase in carrier concentration. Consequently, this doping enhanced the electrical conductivity of BCSO-based composites, with the composite with 11 wt% PZT additive amount exhibiting a remarkable 318-fold increase, reaching 550 S/cm compared to pristine BCSO. Notably, the composite with 7 wt% PZT additive amount achieved an exceptionally low lattice thermal conductivity of 0.333 W m−1 K−1 at 823 K. Through the synergistic optimization of electrical and thermal transport properties, the BCSO-based composite with 7 wt% PZT additive amount obtained a ZT value of ∼0.9 at 873 K, representing a 2.45-fold increase compared to pristine BiCuSeO. This straightforward method presents a cost-effective and scalable approach to enhance the thermoelectric performance of various materials, opening new avenues for potential commercial applications. [ABSTRACT FROM AUTHOR]

Thermal protection was always a prominent issue in the aerospace industry. For vehicle safety, reliability and payload requirements, thermal protection materials were usually expected to possess low density, superior mechanical and thermal insulation properties. Here, lightweight and high-strength porous mullite-silica ceramics were manufactured using particle-stabilized foaming technique. The strength and thermal insulation properties of porous ceramics modified with hollow silica spheres were significantly enhanced. A 10 wt% hollow spheres addition achieved a 28.9 % increase in strength and a 33.4 % decrease in thermal conductivity with almost constant porosity (from 86.39 % to 87.04 %). Considering the characteristics of light weight, high compression strength and superior thermal insulation performance, porous ceramics could be applied as thermal protection materials in the aerospace sector. [ABSTRACT FROM AUTHOR]

Porous high-entropy transition metal compounds, an important type of ultra-high temperature material, have attracted increasing attention in the applications of extreme environments due to their low density, good thermal insulation and stable chemical properties. A robust, flame-retardant and high-temperature resistant high-entropy carbonitride (Ti 1/5 V 1/5 Mo 1/5 Nb 1/5 Ta 1/5)(C 0.55 N 0.45) (HECN) porous ceramic was synthesized and thoroughly characterized. It exhibited a porosity of 93.5 %, a compressive strength of 1.3 MPa and a good high-temperature stability up to 1673 K, which, along with its outstanding fire-retardancy, and low thermal conductivity (as low as 0.150 W m−1 K−1 at 298 K), made it a good candidate material for thermal insulation applications in ultra-high temperature environments. Moreover, the Density functional theory (DFT) calculations predict that the [N]/([C]+[N]) ratio in HECN foam affects its lattice thermal conductivity which is decreased by 67 % upon increasing the ratio from 0 to 1/2. [ABSTRACT FROM AUTHOR]

The high production cost and extremely weak mechanical properties of SiO 2 aerogels have been two major challenges hindering its widespread application. Atmospheric pressure drying (APD) has always been regarded as the optimal process to reduce costs. However, traditional APD is cumbersome, still uses a large amount of expensive raw materials, and is extremely immature. In this study, a novel APD was developed, inspired by the wing changes during adult damselfly process. Inorganic silica source/water was used as the raw material, and CO 2 was used instead of low surface tension solvent to stabilize the aerogel skeleton structure in situ, and ultimately aerogel material was obtained. The thermal conductivity of pure aerogels was as low as 0.0264 W/(m·K), the porosity reached 94.7 %, and the preparation cycle was only 28.5 h. The thermal stability of the skeleton structure and the chemical stability of surface were investigated and showed the hydrophobicity to withstand temperatures up to 400 °C. Aerogel composites feature low thermal conductivity of 0.0283 W/(m·K), and prominent thermal insulation properties over a wide temperature range of 50–300 °C. For traditional APD, this method shortens preparation cycle by 1–6 times. Compared with the commercial aerogel, the cost is reduced by 38.2 %, and the process is simple and environmentally friendly under the premise of ensuring excellent performance. [Display omitted] • A novel atmospheric pressure drying of aerogels preparation inspired by biology. • Stabilization of aerogel structures with CO 2 instead of low surface tension solvents. • The preparation cycle time is shortened by 1–6 times, the cost is reduced by 38.2 %. • Thermal conductivity of 0.0264 W/(m·K) and hydrophobic temperature resistance of 400 °C. • Aerogel composites have outstanding thermal insulation and moisture resistance. [ABSTRACT FROM AUTHOR]

Dy3+, Eu3+ co-doped glass ceramics (GCs) containing SrMoO 4 crystalline phase were prepared by melt-curing-crystallization method. The most favorable heat treatment conditions for the glass ceramics were found to be 610 °C/2 h by differential scanning calorimetry (DSC), ultraviolet spectrophotometer (UV–Vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The best doping concentrations of Dy3+ and Eu3+ in this glass ceramic were 0.8 % and 0.6 %, concentration quenching caused by dipole-dipole interactions occurs when the content of rare earth ions in GCs continues to increase. The chromaticity coordinates of the Dy3+- Eu3+ co-doped glass ceramics changed from cool white light to warm white light with the addition of Eu3+ concentration. At the optimal doping concentration (0.8 % Dy3+-0.6 % Eu3+), the chromaticity coordinate of glass ceramics is (0.3972, 0.3331), and the related color temperature is 3047 K. The luminescence intensity can still reach about 80 % of room temperature at 180 °C, and its thermal quenching activation energy is 0.233 eV. This suggests that glass ceramics have excellent thermal stability. After adding an appropriate amount of Li+, the crystalline phase of the glass ceramics remained unchanged and the luminous intensity of the glass ceramics increased by a factor of about 1.4 in the same environment. The thermal quenching activation energy of the glass ceramic doped with 0.2 % Li+-0.8 % Dy3+-0.6 % Eu3+ was 0.344 eV. The experimental results indicate that GCs has potential application prospects in the field of solid-state lighting. [ABSTRACT FROM AUTHOR]

This study describes the preparation of bimodal reinforced Cu/Ti 3 SiC 2 /C laminated-like composites using flake powder metallurgy and vacuum hot-press sintering process. The objective was to accurately modulate the formation of oriented reinforcement network in two-dimensional carbon materials. The powders used in the five designed composites were flake Cu powder (45–60 μm), Ti 3 SiC 2 (1–5 μm), graphite flakes (GFs, 120 μm) and graphene nanoplatelets (GNPs, 15 μm). Among them, the proportions of Ti 3 SiC 2 (10 wt %) and GFs (3 wt %) remained unchanged, GNPs accounted for 0 wt %, 0.5 wt %, 1.0 wt %, and 1.5 wt %, and Cu powder accounted for a decreasing proportion. Formation mechanisms of GFs and GNPs in oriented networks were quantitatively analyzed using the alignment model. Additionally, the related strengthening and failure mechanisms were investigated. According to the study, the bimodal laminated-like Cu/Ti 3 SiC 2 /C composites with 0.5 wt% GNPs added showed the best overall performance. Specifically, it exhibited a hardness of 125.7 HV, tensile strength of 276.3 MPa, thermal conductivity of 207.8 W m−1 K−1, and electrical conductivity of 23.6 MS/m. The network enhanced by the two-dimensional carbon material achieves efficient and orderly load transfer and dissipation mechanisms, optimizing stress distribution and enhancing fracture resistance, resulting in improved mechanical properties. In addition, the formation of the oriented reinforcement network optimizes the orientation arrangement of the reinforcing particles, which somewhat mitigates the scattering of thermoelectric carriers by structural defects in the composites, and the enlarged mean free-range improves the migration efficiency of electrons and phonons. Therefore, the erection of bimodal laminated-like structure achieves the goal of optimizing the properties of the composites. [ABSTRACT FROM AUTHOR]

Strontium titanate nanoparticles (SrTiO 3 NPs) were produced via the solid-state reaction method. Then, they were used to enhance the structural, mechanical, electrical, and dielectric properties of polyvinyl alcohol (PVA)/polyethylene oxide (PEO) blend for energy storage applications. For this purpose, SrTiO 3 NPs were dispersed in the polymer blend to fabricate nanocomposite films using a solution casting method. The nanocomposite films were then characterized using a variety of instruments, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Ultraviolet/Visible spectroscopy (UV/visible), and impedance analyzers. Based on XRD and TEM measurements, the synthesized SrTiO 3 NPs have a cubic perovskite phase and a diameter that varies between 70 and 160 nm. Additionally, according to XRD measurements, adding SrTiO 3 NPs to PVA/PEO reduces the crystallinity of the resulting nanocomposites. In addition, the surface morphology and elemental composition were demonstrated through the utilization of scanning electron microscope. (SEM) and energy dispersive X-ray spectroscopic analysis (EDX) spectra, where PVA and PEO polymers formed a homogenous and rough surface, and the SrTiO 3 NPs of low concentrations were spread out within the blend's structure. Analysis of the FTIR peaks revealed prominent characteristic peaks associated with vibrational groups that change randomly with the concentration of SrTiO 3 NPs. With increasing SrTiO 3 NPs concentration, the nanocomposite UV/visible absorbance, optical bandgap energies, and refractive index were calculated and discussed. Impedance studies conclude that the amount of SrTiO 3 NPs in a mixture raises the mixture's AC electrical conductivity, dielectric loss, and dielectric constant. The mechanical characteristics, such as Young's modulus, yield strength, and strain at failure, were assessed by examining the tensile test of prepared films. The thermal stability of PVA/PEO-SrTiO 3 nanocomposite films were studied by thermogravimetric analysis (TGA). These experimental results point to the potential for employing the produced nanocomposites in optoelectronic and capacitive energy storage systems. [ABSTRACT FROM AUTHOR]

During the machining of Inconel 718 using SiAlON ceramics, the tool life can be significantly influenced by diffusion wear. To investigate this crucial wear behavior, this study focuses on the thermochemical interactions in the diffusion couple between SiAlON ceramics and Inconel 718 superalloy. So, we examine the microstructural characteristics and phase formation behavior in the reacted layer between these two materials. The interfaces between these two materials exhibit distinguishable elemental contrasts and phase formations. Particularly, the phases indicate vitrification or devitrification in the diffusion layer, influenced by the chemical composition. This issue in the diffusion couple was analyzed with thermophysical properties using light flash analysis (LFA). After, it was confirmed that the vitrification of the diffusion layer can be induced by the conduction behavior of heat trapped between SiAlON and Inconel 718 during supercooling. These characterizations verify that the devitrification of the welding layer (diffusion layer), resulting from the reaction between SiAlON ceramics and Inconel 718 superalloy, can depend on the thermal conductivity of the prepared ceramics. Furthermore, we discovered a possibility that this could contribute to improving tool performance by suppressing diffusion wear. [ABSTRACT FROM AUTHOR]

In this work, a series of K 2 O–MgO–B 2 O 3 –P 2 O 5 (KMBP) glasses were prepared by the melt-quenching method and the glass-ceramics were prepared by the one-step heat treatment. The thermal, structural, physical and optical properties, as well as the crystallization behaviour of the KMBP system, were investigated in detail using characterization techniques such as DSC, XRD, SEM, FTIR, transmittance spectroscopy and microhardness. As indicated by DSC, the thermostability and glass-forming ability were gradually enhanced through the partial substitution of K 2 O by MgO. XRD showed that the main crystalline phases of the glass-ceramics (GC) were gradually converted from the P –Mg–K–O based crystalline phases to the P –Mg–O based and the P –Al–O based crystalline phases. The SEM results indicated that tiny grain-like crystals were successfully precipitated from the parent glasses after heat treatment. The deconvoluted FTIR spectra results showed a gradual conversion of the [BO 3 ] and [PO 3 ] units towards the [BO 4 ] and [PO 4 ] units with the increase of the MgO contents. The increase in the degree of glass network polymerization was the essential reason for the increment in the microhardness of the parent glasses. The microhardness of GC featured a trend concordant with the crystallinity of the crystalline phases. The values of metallization criteria (M C) between 0.34 and 0.45, as well as the higher values of third-order nonlinear polarizability (χ (3)) and nonlinear refractive index (n nl) are indicative of the good suitability of the KMBP glasses for the nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Barium borosilicate (BBS) glass is a potential three-dimensional system packaging and sensor cover material. In this study, we prepared glass samples with different SiO 2 /B 2 O 3 ratios based on the revised model of Dell and Bray and discussed the effect of boron anomaly on dielectric and thermal properties through Raman spectroscopy. The results indicate that the [BO 4 ] tetrahedrons are beneficial in reducing the dielectric constant and dielectric loss to a certain extent, while the improvement in the coefficient of thermal expansion (CTE) is attributed to the depolymerization of the glass network by the [BO 3 ] triangles. After the disappearance of the boron anomaly, a certain amount of dielectric performance is sacrificed in exchange for an increase in the CTE. When the substitution rate of B 2 O 3 for SiO 2 reaches 15.12 mol%, the CTE of the sample increases to 8.43 × 10−6/°C, in addition, the dielectric constant and dielectric loss decrease to 4.90 and 0.0071 (@1 GHz), respectively. In summary, this work provides a suitable method for preparing glass with a high coefficient of expansion and low dielectric loss to address the thermal mismatch effect of different materials in electronic packaging systems. [ABSTRACT FROM AUTHOR]

Bioactive glasses (BG) containing silicon, phosphorous, and boron have emerged as promising materials for bone tissue engineering. Modifying ions play a multifaceted role in BGs, influencing their structure, properties, and biological activity that depends on their size, charge, and coordination chemistry. This study investigates the addition of sodium borate (Na 2 B 4 O 7) to the 58S BG and the mixed alkali effect (MAE) resulting from incorporating Na and B ions into the CaO–SiO 2 –P 2 O 5 system. In specific concentrations, Na+ and Ca2+ ions function as network modifiers, introducing structural disruptions and generating defects that impact the glass transition temperature (T g), crystallization temperature (T c), hardness, and sintering characteristics. The physicochemical characterization of BGs confirms the incorporation of Na and B structures. Furthermore, the Na and B doped glass sample with a [Na/Si] ratio of 0.045 exhibits favorable properties for promoting cell attachment, including forming a hydroxyapatite (HAp) layer over the surface, thereby accelerating human placental mesenchymal stem cells (hPMSCs) proliferation. The findings demonstrate the potential of Na 2 B 4 O 7 incorporation in BG for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

This work addresses the problem of obtaining of Ca 3 Co 4 O 9+δ -based ceramics with enhanced thermoelectric performance. Phase-inhomogeneous layered calcium cobaltite ceramics with cationic nonstoichiometry were prepared by solid-state reactions method and a field assisted sintering technology (FAST). Comprehensive experimental characterizations were conducted on the prepared bulk samples, focusing on their phase composition, as well as thermal (including thermal expansion, thermal diffusivity, and thermal conductivity), electrical (encompassing electrical conductivity and the Seebeck coefficient), and functional properties (such as power factor and figure-of-merit). The FAST technique allowed to obtain ceramics with low porosity and high electrical conductivity, which increased as the Ca:Co ratio within the samples decreased, while sample phase inhomogeneity considerably increased the Seebeck coefficient. The best thermoelectric performance was demonstrated for cationic nonstoichiometric Ca 3 Co 4.4 O 9+δ , which power factor and figure-of-merit values at 825 °C reached 427 μW⋅m−1⋅K−2 and 0.146, respectively. • Ca 3 Co 4 O 9+δ -based ceramics prepared by field assisted sintering technology possessed low porosity and high conductivity. • Electrical conductivity of bulk samples increased at decreasing Ca:Co ratio. • Phase inhomogeneity of prepared ceramics increased the Seebeck coefficient. • Ca 3 Co 4.4 O 9+δ ceramics showed the best thermoelectric performance. [ABSTRACT FROM AUTHOR]

Low-cost amorphous nano-carbon (ANC) was employed as an absorbent to modify the microwave performance of AlN ceramics (AlN-4 wt% Y 2 O 3 - x wt% C, x = 0, 2.0, 3.8, 3.9, 4.0) via hot-pressing sintering, and the thermal and mechanical properties were also investigated. With the increase of ANC content from 0 to 4.0 wt%, the relative density of AlN composite decreases from 3.28 g cm−3 to 3.16 g cm−3 when sintered at 1800 °C for 2 h, and with the increase of sintering temperature from 1700 °C, the density of the 4.0 wt% ANC doped AlN composite presents trend of increase and reaches the maximum value of 3.16 g cm−3 at 1800 °C and then decreases. The XRD pattern shows that the composites are composed of AlN and Y–Al–O (YAG, YAP, YAM et al.) phases. SEM results indicate that average grain sizes for AlN and secondary phases gradually decrease with increasing carbon content, suggesting inhibited grain growth due to ANC addition. No obvious changes in phase constitution nor intensity changes were detected with the increase in carbon content and sintering temperature. As the carbon content increases from 0 to 4.0 wt%, the dielectric constant gradually increases from ∼9 to 13.89 at 10 GHz, the dielectric loss gradually increases from the vicinity of 10−3 to 0.38 at 10 GHz, and the reflective loss decreases from −27.92 dB to −49.40 dB, the thermal conductivity of the AlN-ANC composite decreases from 116.63 W m−1 K−1 to 50.13 W m−1 K−1. In addition, with 4.0 wt% ANC addition, the dielectric constant, dielectric loss, reflective loss, hardness, elastic modulus, bending strength, and fracture toughness are 13.89, 0.38, 49.40 dB, 6.4 ± 0.4 GPa, 262 GPa, 268.78 MPa, and 1.4 ± 0.1 MPa m1/2, respectively. Its ability to efficiently absorb microwave energy enhances the performance of devices including radar systems, communication equipment, and microwave heating systems, making it a promising candidate for microwave vacuum electronic applications. [ABSTRACT FROM AUTHOR]

High-entropy ceramics have garnered significant attention in recent years owing to their exceptional properties and structural diversity. In this work, single-phase medium/high entropy ceramics, namely (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.5 Ti 0.5)O 3 and (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.1 Ti 0.9)O 3 , were successfully designed and prepared utilizing Spark Plasma Sintering (SPS). A comprehensive investigation was conducted into the phase structure, microscopic morphology, dielectric properties, and thermal behavior of these ceramics. It was observed that all ceramics maintained a cubic perovskite structure (space group: Pm 3 ‾ m), and the introduction of multi-element doping rendered them more stable across a wide frequency and temperature range. Notably, (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.5 Ti 0.5)O 3 exhibited remarkably low dielectric loss (0.0001 at 1 kHz) at room temperature, along with excellent dielectric temperature stability (25–400 °C). By reducing the zirconium concentration in (Ca 0.2 Sr 0.4 Ba 0.4)(Zr 0.1 Ti 0.9)O 3 , a slight decrease in dielectric temperature stability was observed (25–350 °C); however, it demonstrated lower thermal conductivity (0.41 W/(m·K), 1200 °C) and maintained good high-temperature stability. The discovery highlights the promising practicality of both ceramics for high-temperature dielectric applications. [ABSTRACT FROM AUTHOR]

Borophosphosilicate glasses with varying sodium ion concentrations were investigated for their, structural, thermal, and electrical properties. All the obtained glasses were transparent except the glass with the highest sodium content, which exhibited translucency due to inhomogeneities. Increasing sodium content led to reduced boron and silicon content while maintaining a constant B/Si ratio, indicating progressive depolymerization of the glass network. Confocal microscopy, scanning electron microscopy, and atomic force microscopy showed homogeneous and granular structure for samples with lower sodium content, but higher sodium content resulted in visible agglomeration/nanocrystallization. X-ray diffractograms showed amorphous nature for most samples, with samples doped with the highest concentrations of Na 2 O showing several broad reflections suggesting nanoscale crystallinity. Fourier-transform infrared spectroscopy revealed shifts in dominant bands with increasing sodium content, indicating depolymerization of the borate network. An observed decrease in glass transition temperature and thermal stability with increasing sodium content was attributed to depolymerization and formation of non-bridging oxygens. Impedance spectroscopy revealed two relaxation processes associated with the transport of Na+ ions through two different regions. DC conductivity and activation energy predominantly increased with the sodium ion content at high temperatures. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN), prized for its high thermal conductivity and electronic insulating properties, finds widespread use in electronic applications, particularly as a substrate material. However, its relatively low fracture toughness limits its application. In this study, to enhance both the thermal and mechanical properties of AlN ceramics, we thoroughly investigate the microstructure, thermal, and mechanical properties of self-reinforced AlN ceramics fabricated by spark plasma sintering, with self-reinforcement achieved through the integration of AlN whiskers within the AlN matrix. Unlike previous studies utilizing conventional pressureless sintering with limited sintering conditions, this work employs spark plasma sintering with a wide range of temperatures (1600–1900 °C) and holding times (10–30 min), providing a comprehensive understanding of the sintering behavior. Microstructural features, observed through optical and scanning electron microscopy, reveal distinct toughening mechanisms via crack deflection and branching, with a maximum 20% enhancement. The self-reinforced AlN ceramics exhibit remarkable improvements in thermal conductivity, reaching up to 150 W m−1 K−1, surpassing reported values for spark plasma-sintered AlN ceramics. Adding AlN whiskers enhances the thermal and mechanical properties of AlN simultaneously, particularly at 1800 °C for 10 min with controlled grain size and nicely integrated AlN whiskers. This work not only contributes valuable insights into the complex relationship between processing parameters, microstructure, and resulting thermal and mechanical properties but also highlights the enhanced thermal and mechanical properties of self-reinforced AlN ceramics. [ABSTRACT FROM AUTHOR]

Addressing the issue of carbon contamination during the smelting of specialty metals or alloys, utilizing graphite crucibles, has attracted considerable research attention, prompting the exploration of novel ceramic crucible materials. AlN ceramic, renowned for their exceptional high-temperature stability and resistance to corrosion, have emerged as promising candidates to mitigate this concern. Nonetheless, the limited mechanical properties and thermal shock resistance of AlN curtail its widespread application. In this study, Y 2 Zr 2 O 7 was introduced as an additive to enhance AlN's properties, and AlN-based composite ceramics were fabricated by employing pressureless sintering. The effects of Y 2 Zr 2 O 7 addition (3–10 wt%) on the mechanical properties and thermal shock resistance of the resulting composites were examined. The findings revealed that the incorporation of 5 wt% Y 2 Zr 2 O 7 (AlN-5YZO) led to the highest relative density and a refined grain structure, resulting in superior mechanical properties. Notably, the flexural strength, fracture toughness, and Vickers hardness of AlN-5YZO reached 322 MPa, 3.70 MPa m1/2, and 13.34 GPa, respectively. Furthermore, the presence of crack branching and crack deflection within the composite ceramics impeded crack propagation, effectively augmenting their thermal shock resistance. AlN-5YZO samples exhibited residual strength retention rates of 91.0 %, 84.2 %, and 76.7 % after 10, 20, and 50 thermal shocks between 1000 and 1600 °C, surpassing those of pure AlN. The findings of this study present promising avenues for advancing crucible materials tailored for high-temperature applications. [ABSTRACT FROM AUTHOR]

Microwave heating has been applied to improve cement-based materials (CBMs) structures deicing efficiency, which reduce the effect of icing on their service life. Moreover, the enhanced thermal properties of CBMs can further improve their deicing efficiency. In this study, silicon carbide (SiC) ceramic particles with favorable thermal properties were used to prepare the SiC cement-based materials (SCBMs). The effect of SiC ceramic on the mechanical strength of CBMs was investigated. Next, the heat transfer and storage ability of CBMs were investigated to analyze the changes in their thermal-physical parameters. Then, the surface thermal responses of the CBMs during microwave heating and off were recorded to characterize their temperature evolution in a low-temperature condition. Furthermore, the deicing efficiency of CBMs was determined using the ice layer shedding time (ILST) as the index. The results show that the filling effect of SiC ceramic on CBMs improved their mechanical strength within a certain content range. However, a large content of SiC ceramic caused an increase in the weak area and porosity within the CBMs, further reducing their mechanical properties. The thermal-physical parameters of CBMs were improved after adding SiC ceramic. The thermal conductivity and thermal effusivity of SCBMs-100 were 13.17 W/(m·K) and 1.44 W/(mm2·K), respectively, 7.90 and 2.35 times higher than the control group. Due to the favorable thermal properties of SCBMs, their heating rate and surface temperature field distribution characteristics were further improved. Furthermore, with the increase of SiC ceramic content, the ILST of SCBMs was further reduced during microwave heating. Therefore, the SiC ceramic was a favorable material, improving the thermal properties and deicing efficiency of CBMs to a certain extent. However, considering its effect on the deterioration of the mechanical properties of CBMs, the optimal content of SiC ceramic might be 75%. [ABSTRACT FROM AUTHOR]

The 2.5D oxide/oxide composites become attractive for their excellent integrity and mechanical properties. The thermal shock resistance performance of the material is very important in the actual high temperature application. In this work, the evolution of microstructure and mechanical behavior of the 2.5D oxide/oxide composites from thermal shock at different temperatures and cycles was investigated experimentally mainly by optical microscope, X-ray computed tomography and macro-mechanical tests. The thermal shock resistance mechanism of oxide/oxide composites was qualitatively explored. The results showed that cracks propagation was the main manifestation of thermal shock damage in composites. Compared with 2D composites, 2.5D composites exhibited the finite domain effect on crack propagation due to its reinforcement had certain fibers in Z -direction. This directly caused the critical thermal shock temperature difference of the 2.5D composites (∼900 °C) was more than twice that of the 2D oxide/oxide composites (∼400 °C). In addition, the finite domain effect also significantly reduced the damage growth rate of the 2.5D composites from cyclic thermal shock, highlighting its excellent thermal shock damage resistance. [ABSTRACT FROM AUTHOR]

The rapid development of micro-electronics has a growing demand on the heat dissipation performance of devices, especially thermal management materials. However, recent researches focus on the improvement of single ability, such as thermal or mechanical properties. Herein, a strategy that simultaneously improves thermal and mechanical performance of thermal manager material was proposed, which was achieved by preparing Cu-SiC w composites via the co-electrodeposition technology. The influence of electroplating parameters, such as temperature, current density and reinforcement contents, on the microstructure evolution, mechanical and thermal conductivity were investigated systematically. The fabricated SiC w composite displayed excellent shear strength up to 420 MPa, which is resulted from the Orowan strengthening and load transferring. Additionally, the thermal conductivity of 340 W/(m·K) was obtained, owing to the uniform distribution of whiskers and good interface between the Cu matrix and whiskers. Therefore, the presented work provided an effective method for fabricating comprehensive thermal-mechanical properties and homogeneous heat dissipation capacity Cu-SiC w composites and paved the way for the practical application in the field of the connector between the power devices and heat sinks. [ABSTRACT FROM AUTHOR]

This study utilizes modulation of ionic disorder and electronegativity differences for targeted component design of high-entropy ceramic compositions. A series of novel multicomponent ceramics with the general formula (LaGdYSm) x 2 Yb x 1 Zr 2 O 7 (x 1 +4x 2 = 2, x 1 = 0.6,0.4,0.2,0) were prepared by solid-state reaction. The evolution patterns of their microstructures were analyzed using XRD and TEM, and the anti-sintering ability and thermophysical properties were evaluated. The results confirm that the multicomponent ceramics gradually transform from the coexistence of pyrochlore/fluorite dual-phase structure to pyrochlore structure with the tuning of the size disorder degree. After 50h of exposure to air at 1500 °C, the ceramics retained excellent phase stability. Segregation of La and Yb elements with large differences in radius size occurs, forming a mixture of the La-rich pyrochlore and the Yb-rich fluorite phases. The specimen with the maximum size disorder exhibits the lowest grain growth rate and the greatest thermal insulation properties. Large lattice distortions and sluggish diffusion effects are responsible for the mutual inhibition of grain growth in the two-phase coexistence zone. The thermal insulation properties of the ceramics show well correlated with the degree of the size disorder, further validating the effectiveness of the component design. Meanwhile, the thermal expansion coefficients of prepared ceramic can reach 11.49 × ∼11.58 × 10−6 K−1 at 1000–1100 °C. The customization principles used in this work fill a gap in the compositional design methodology for multicomponent lanthanum zirconate-based high-entropy ceramics. It is essential for developing rare-earth zirconates with tunable thermophysical properties in the area of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

The research and development of chrome-free refractories for non-ferrous metal smelting furnace is imperious for environmental protection. In present investigation, the magnesia-zirconia composite refractories were fabricated with sintered magnesia and desilicated zirconia as raw materials. The mechanical properties, thermal shock resistance properties, phase and microstructure of samples were investigated, and the specific fracture energy of magnesia-zirconia refractories matrix was obtained by statistical grid nanoindentation. The results showed that the magnesia-zirconia refractories added 5 wt%(MZ1 sample) desilication zirconia obtained the best performance, where the apparent porosity was only 18.06 % and the CMOR was 14.9 MPa. In addition, the specific fracture energy of MZ1 sample was 248 N m−1, which was 98 % higher than MZ0 (125 N m−1). Compared with the sample without desilicated zirconia, the residual strength ratio of magnesia-zirconia refractories increased more than 50.0 %. The improvement of the thermal shock resistance and mechanical properties of magnesia refractories was greatly attributed to the formation of t-ZrO 2 in the matrix, where the dissolve of Ca2+ into the ZrO 2 in the matrix is more benefit to the formation of the stable t-ZrO 2 phase. The propagation of cracks is prevented by t-ZrO 2 , which further prevent the trans -granular fracture of magnesia aggregate. Therefore, the magnesia-zirconia refractories contained t-ZrO 2 was expected to be candidate materials as chromium-free refractories used in non-ferrous metal smelting furnaces. [ABSTRACT FROM AUTHOR]

Al 2 O 3 /B 2 O 3 powder mixtures prepared at various ratios from 10.7 to 54.1 wt% B 2 O 3 were used to synthesize Al 18 B 4 O 33 powders by solid state calcination at 1300 °C for 1 h. Al 18 B 4 O 33 formation was completed at 44 wt% B 2 O 3 instead of stoichiometric ratio of 13.17 wt% B 2 O 3. In other words, B 2 O 3 -rich liquid phase accelerated Al 18 B 4 O 33 crystallization. Al 18 B 4 O 33 particles were not acicular in shape when first formed, but they were fully acicular for the 44 wt% and the 54.1 wt% B 2 O 3 mixtures. Anorthite-based glass and CaO were selected to induce liquid phase sintering. CaO considerably improved densification to 95.4 % relative density at 1350 °C. Both glass and mullite also enhanced densification to 94.8 %. Epitaxial nucleation of mullite on Al 18 B 4 O 33 particles resulted in a solid solution as well. Dielectric, mechanical and thermal properties of the samples were investigated and evaluated for possible applications. [ABSTRACT FROM AUTHOR]

The ZrO 2 fiber paper exhibits excellent thermal insulation properties, however, its limited mechanical strength and insufficient thermal stability hinder its widespread applications. The composite fiber papers, using mullite fibers possessing a high aspect ratio and exceptional thermal stability combined with ZrO 2 fibers, were fabricated via a vacuum-assisted filtration method. This method involved the successive stacking of composite fibers with alumina sol, using vacuum-induced directed water flow to create a layered structure reminiscent of nacre. The layered structure of the nacre, which demonstrates remarkable strength and hardness, has also served as a source of inspiration for the architectural design of the fiber paper. The tensile strength of pure ZrO 2 fiber paper was significantly enhanced by the addition of 7 wt% mullite fibers, resulting in a remarkable increase to 0.1805 kN/m. The paper exhibited exceptional resistance to bending, maintaining 96 % of its bending strength even after undergoing 100 cycles. The thermal shrinkage of the composite paper, containing 15 wt% mullite fibers, was reduced from 17.75 % observed in pure ZrO 2 fiber paper to a mere 1.32 % after undergoing heat treatment at a temperature of 1300 °C for 2 h. The composite paper, measuring 5 mm in thickness and consisting of 7 wt% compositions, displayed exceptional thermal insulation properties when exposed to a hot side temperature of 1370 °C. It effectively insulated temperatures up to approximately 1000 °C. [ABSTRACT FROM AUTHOR]

In this study, we successfully prepared quaternary germanate glasses (Ba x/3 Sr x/3 Ca x/3)Ge (1-x) O 3 (x = 0.1–0.5) using a containerless solidification method. The structure of the germanate amorphous materials was characterized using techniques such as XRD, SEM, TEM and Raman. We evaluated the thermodynamic properties of the amorphous materials using differential scanning calorimetry and investigated their crystallization activation energies. In terms of application performance, we measured electrical conductivity and impedance spectra for the electrical properties, while the optical properties were assessed through the refractive index and transmittance. The results revealed that the (Ba 0.2/3 Sr 0.2/3 Ca 0.2/3)Ge 0.8 O 3 system represented the germanium anomaly point. Due to the highest number of ternary rings and the most compact structure within this system, the values of density, glass transition temperature, refractive index, and bandgap all reached their maximum. As the content of alkaline earth oxides increased, the glass network structure gradually fractured, leading to an increase in non-bridging oxygens and corresponding changes in properties. [ABSTRACT FROM AUTHOR]

Double-ordered manganites LnBaMn 2 O 6–δ (Ln = Nd, Sm) were shown to possess a variable oxygen content from δ = 0 to 1 while maintaining a tetragonal structure within the temperature range of 973–1223 K and under partial oxygen pressure 10−22 – 1 atm. Coulometric titration technique was successfully utilized to reveal three separated phase in these materials depending on oxygen content. Thermodynamic analysis based on experimentally obtained isothermal functions δ = f (p O 2) enabled one to develop a defect formation model suggesting a coexistence three main processes of defect formation in the studied oxides. Thus oxidation and partial disproportionation of manganese supplemented by intrinsic oxygen disordering were demonstrated to govern defect equilibrium. Different influence of activity coefficients involved in the thermodynamic model was considered. Moreover, a reduction in the radius of lanthanide was found to be favorable to expand oxygen homogeneity region and to decrease in the enthalpy of oxidation reaction. [ABSTRACT FROM AUTHOR]

The biogenic synthesis of Fe 3 O 4 nanoparticles was boosted by the use of a recently found organic acid produced from Citrus sinensis. Fe 3 O 4 nanoparticles were synthesized at 350 °C and 450 °C, and their physical and chemical properties were studied using a number of different characterisation techniques. Crystalline structure and phase were determined by X-ray diffraction (XRD) analysis of as-synthesized and annealed Fe 3 O 4 nanoparticles. This finding demonstrates that the Fe 3 O 4 nanoparticles have a unique, cubic spinel structure with only one phase. With the use of well-established formulae, we were able to calculate the crystallite size and lattice parameter of the synthesized Fe 3 O 4 nanoparticles, and found that their size increased as a function of the annealing temperature, from 11 nm to 34 nm. The FTIR method was used to analyse the as-synthesized and annealed Fe 3 O 4 nanoparticles for functional groups, molecular structure, and chemical bonding. Metallic components at 465, 551 and 1628 cm−1 were found after analysing the three samples. Field Emission Scanning Electron Microscopy (FESEM) was used to analyse the surface morphology and grain size fluctuations of Fe 3 O 4 nanoparticles, while Energy Dispersive X-ray Spectroscopy (EDX) was used to study the elemental composition. Fe 3 O 4 nanoparticles' thermal characteristics change depending on the annealing temperature. The antibacterial efficacy of Fe 3 O 4 nanoparticles, manufactured using green methods, was assessed against two different types of bacteria: Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative). [ABSTRACT FROM AUTHOR]