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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]

The concurrent enhancement of toughness, electrical conductivity, and thermal stability in polycrystalline diamond composites represents a formidable challenge. Here, a novel diamond-TiC composites (referred to as DTC) with high fracture toughness and conductivity were synthesized through a high-temperature and high-pressure reaction sintering process utilizing two precursors: diamond mixtures containing TiH 2 and Ti-coated diamonds. On the one hand, the inherent bonding and encasing of TiC onto the diamond matrix form a heterogeneous structure, providing high strength and excellent fracture toughness up to 11.6 MPa·m1/2. On the other hand, the established oxygen barrier and current pathway offer a thermal stability of 765 °C and high conductivity up to 837 S·m−1. Remarkably, this rare combination of mechanical, electrical, and thermal properties has been realized within a single material under relatively moderate sintering conditions, thus positioning diamond-TiC composites as a promising ceramic for electrical applications in high-stress environments. [ABSTRACT FROM AUTHOR]

In the present study, Mg–5Ni and Mg–15Ni alloys are prepared, and their (de)hydrogenation properties are investigated by thermal desorption spectroscopy (TDS). A new hydrogenation condition is developed to improve the hydrogen uptake properties of the Mg–Ni alloy. It is found that the hydrogen absorption and thermal desorption properties of both alloys are extremely sensitive to the presence of 3% O 2 in the hydrogenation environment. Although O₂ accelerates hydrogen absorption, it lowers the desorption temperature and reduces the hydrogen storage capacity of the Mg–Ni alloy by consuming Mg₂Ni if it is added in every cycle. The hydrogen storage capacity of Mg–Ni alloys can be significantly increased by adding oxygen only in the second cycle instead of in all cycles. In the early stages of hydrogenation, only two TDS peaks are observed, while in later cycles a new peak appears at higher temperatures. These peaks correspond to the decomposition of Mg₂NiH₄ (peak 1), MgH₂ (peak 2), and the release of hydrogen from the bulk material (peak 3). It is also evident that the Mg–15Ni sample has a better hydrogen storage capacity than the Mg–5Ni sample. • Studying (de-)hydrogenation properties of Mg–Ni alloys in presence of 3% O 2. • O 2 accelerates hydrogen absorption and lowers the hydrogen desorption temperature. • Adding 3% O 2 only in 2nd cycle improves hydrogen storage capacity of Mg–Ni alloys. • In early cycles, two TDS peaks are seen, while in later ones a new peak appears. • The Mg–15Ni sample has a better hydrogen storage capacity than Mg–5Ni. [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]

There is a notable scarcity of reference data on the thermal conductivity of orthohydrogen in both vapor and liquid phases within the open literature, compared to parahydrogen and normal hydrogen. An improved corresponding states principle (CSP) model is proposed to predict the thermal conductivity of orthohydrogen by employing an optimized shape factor, which is expressed as a correlation with respect to pressure and temperature from the triple point to 300 K and at pressures up to 20 MPa. Critical parameters, ideal state thermal properties, and eccentricity factor are involved in the calculation as input parameters. The feasibility and accuracy of the proposed CSP model is verified by using experimental data of parahydrogen and some theoretical data of orthohydrogen. The estimated uncertainty of the model against high-precision experimental data of parahydrogen is within ±2.82 %. When the model is applied to dilute gas orthohydrogen, the predictions exhibit a deviation of less than ±5 % compared to other methods found in the literature. In addition, a correlation for thermal conductivity of parahydrogen, presented as a single function of temperature, is also proposed along the vapor-liquid equilibrium at temperatures from the triple point to the critical point, with an uncertainty of ±3 %. [ABSTRACT FROM AUTHOR]

In the thermal protection system of spacecraft, the bolts connecting the ceramic to the internal superalloy need to have low thermal conductivity and high strength. Two dense high entropy fluorite oxides (Zr 1/7 Hf 1/7 Ce 1/7 Y 2/7 La 2/7)O 2-δ (ZHCYL) and (Zr 1/8 Hf 1/8 Ce 1/8 Y 1/4 La 1/4 Pr 1/8)O 2-δ (ZHCYLP) were designed and synthesized by using the synergistic effect of plasma-assisted ball milling and spark plasma sintering(SPS). Through the synergistic effect of lattice distortion and oxygen vacancy guided by entropy regulation, ZHCYLP synthesized in this study has lower thermal conductivity(1.13 W·m−1·K−1), higher high temperature strength(192 MPa at 1000 °C) and high temperature phase stability up to 1600 °C than 8YSZ ceramics. The thermo-mechanical coupling finite element analysis results of high temperature bending test show that the variation trend of the maximum stress value of the sample is consistent with the experimental results. This shows that the mechanical and thermal properties of high entropy oxides can predict the variation trend of the maximum stress value in high temperature bending tests. It opens up a new way for designing and synthesizing high entropy oxide materials with low thermal conductivity and high strength which can be applied in the field of heat protection and load bearing. [ABSTRACT FROM AUTHOR]

Ceramic fibers are an important thermal insulation material that are not only widely used in extreme conditions, but also play an important role in energy conservation and energy efficiency for sustainable development. However, the practical application of conventional ceramic fibers has a high thermal conductivity in high-temperature environments, which hinders their widespread application. Here, a novel lamellar structured porous SiTiOC/C composite ceramic materials was designed and prepared with excellent thermal insulating properties. The unique microstructure endowed the porous SiTiOC/C composite ceramic materials with a high IR refractive index (93.81%) and an ultra-low thermal conductivity (0.0562 W·m−1 K−1 at 600 ℃). In addition, the porous SiTiOC/C composite ceramic materials not only exhibited excellent mechanical properties (4.46 MPa at 800 ℃), but also demonstrated impressive oxidation resistance and thermal stability. In summary, the proposed porous SiTiOC/C composite ceramic materials provide a reference for the development of high-temperature insulation with good mechanical properties. [ABSTRACT FROM AUTHOR]

Ceramic aerogels are promising candidates for high-temperature thermal resistance and thermal insulation materials. However, their application can be restricted by their brittleness when exposed to harsh conditions. Herein, this study has developed a novel synthesis process based on a sol-gel method and carbothermal reduction-nitridation to produce a porous TiN composite aerogel from an organic/inorganic hybrid. The resulting TiN displays a polyhedral particle size of around 30–60 nm with nanoscale pores. In addition, the TiN aerogel demonstrates a high BET-specific surface area of 653.42 m2/g and a very low thermal conductivity of 0.046 W/(m·K). Furthermore, the TiN aerogel composite displays a good thermal difference with no shrinkage and cracks of the morphology during the butane blazing torch at 1300 °C for 10 min under air environment, demonstrating its excellent thermal insulation property and anti-oxidation characteristics. The gas-solid reaction mechanism of TiN aerogel based on the Gibbs free energy calculations is also proposed. [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]

A geometric bowtie design for the purpose of mimicking (matching) and/or mitigating (reducing) the thermal expansion effects between two laterally opposing structures is investigated. A bowtie design is that of two opposing overlapping triangles with farthest sides parallel. This design embodies thermal centering concepts which utilize the relationships of the trigonometric identity known as the law of sines for a triangle from which beneficial thermal properties can be engineered. For validation. The bowtie design is embodied using two separated Zerodur plane mirrors, symmetrically opposed, and each seated in Maxwell-style kinematic couplings of spheres and vee-groves. The vee-grooves form a wheel-like pattern on an aluminum baseplate. The intersection of the vee-grooves is the common overlapping thermal center of both mirror mounts. The refractive-index corrected interferometric measurement of the displacement between these two mirrors shows that even during non-isothermal non-equilibrium transitions and states, the nominal ∼90 μm thermally induced (13 °C) expansion of an aluminum baseplate can be mitigated, being reduced more than 98 % to ∼1.4 μm by mimicking the thermal expansion properties of the mirrors' structural material. Engineering thermally-invariant kinematic bowtie designs using materials having higher thermal expansion coefficients is also described. • Kinematic bowtie design for thermal mimicry and mitigation is described based on law of sines. • Thermal mimicry and mitigation demonstrated for separated parallel Zerodur mirrors. • Thermal expansion mitigation for an aluminum base demonstrated to be reduced to near 1 %. • Non-isothermal non-equilibrium observations are described and considered. • Designs for effective CTE engineering even for zero and negative values are given. [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]

In this study, the microstructure and thermal properties of the plasma-sprayed free-standing Lu 2 Si 2 O 7 coating before and after thermal aging at 1350 °C were investigated. The tri-layer Yb 2 SiO 5 /Lu 2 Si 2 O 7 /Si EBCs were designed and prepared onto SiC f /SiC substrates, and its thermal shocking behaviors were also explored. Results showed that the as-sprayed coating was mainly composed of Lu 2 Si 2 O 7 and amorphous phase, and significant microstructural evolution, such as grain growth and defects reduction, was observed after thermal aging. Plastic deformation and well damage tolerance including twinning and dislocation were confirmed by TEM analysis. The CTE of the coating before and after heat treatment were similar, while the thermal conductivity increased after thermal aging. After 100 thermal cycles, penetrating microcracks in the Yb 2 SiO 5 top layer were mostly stopped at the Yb 2 SiO 5 -Lu 2 Si 2 O 7 interface, implying the excellent crack propagation resistance of the tri-layer EBCs. The thermal shock behaviors were clarified based on microstructure combined with thermal stresses analysis. • Microstructure and thermal property of Lu 2 Si 2 O 7 coating were studied. • Lu 2 Si 2 O 7 exhibited microstructure and thermal property evolution after aging. • The Yb 2 SiO 5 /Lu 2 Si 2 O 7 /Si EBCs possessed excellent thermal shock resistance. • Lu 2 Si 2 O 7 could be a promising interlayer material for tri-layer EBCs. [ABSTRACT FROM AUTHOR]

In this study, a highly dense GdB 6 bulk ceramic material was fabricated using one-step in-situ reaction spark plasma sintering technology. The sample with a relative density of 96.7 % and a purity of 96.9 wt% was successfully obtained by sintering at 1800 °C for 30 min under a uniaxial pressure of 50 MPa. The Vickers hardness, elastic modulus and fracture toughness of the as-obtained GdB 6 bulk ceramics were 18.9 GPa, 209 GPa and 1.6 MPa·m1/2, respectively. The thermal conductivity of GdB 6 at room temperature was 28.68 W·m−1·K−1, 70 % of which was mainly attributed to phonon vibration, while the remaining 30 % to the electrical thermal conductivity. In addition, the as-obtained GdB 6 ceramics showed no phase transformation after heat treatment at a relatively high temperature of 2100 °C for 20 min in Ar atmosphere. The highly covalent octahedral boron framework played a critical role in maintaining the phase stability of the GdB 6 crystal lattice. This suggested that GdB 6 ceramics could be used as potential ultra-high temperature ceramics for aerospace applications and high-power vacuum electronic devices operated at high temperatures. [ABSTRACT FROM AUTHOR]

Rare earth compounds (RE 2 O 3), typically Eu 2 O 3 and Gd 2 O 3 , are considered as absorbing materials due to their long chain neutron absorbing ability and high efficiency of neutron absorption. In this paper, a specifically designed x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x = 0.6, 0.7, 0.8, 0.85) composite ceramics with excellent thermal properties were synthesized through direct thermal decomposition reactions followed a high-temperature sintering method under vacuum conditions. X-ray diffraction (XRD) and Raman spectroscopy analysis indicated that the obtained ceramics consisted of monoclinic Eu 2 O 3 and fluorite Gd 2 Zr 2 O 7 phases. The hardness of x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics (x = 0.8, 0.85) have no significantly changes in the test temperature range (25–350 °C). The thermal expansion coefficients (TECs) (7.3–10 ×10-6 K-1) are lower than Dy 2 TiO 5 (9.3–10.4 ×10-6 K-1), and the thermal expansion rate changes linearly with the increase of temperature, which indicates that the x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 ceramics exhibit excellent high temperature phase stability. Furthermore, the range of thermal conductivities is from 0.96 W·m-1·K-1 to 2.02 W·m-1·K-1 (25–800 °C), which is higher than Dy 2 TiO 5 (0.27–0.55 W/m·K, 220–650 °C). Compared with the state-of-art Dy 2 TiO 5 ceramics, x Eu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 have superior thermal properties and are therefore expected to be the next generational of neutron absorbent materials used in ash rod. [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]

In this work, an acid invertase isolated from Lathyrus aphaca seedlings is purified, and its thermal properties are investigated. Acid invertase was purified through salt fractionation, CM-cellulose, and Ultrogel ACA-44 chromatography. Using SDS-PAGE, the consistency of the isolated enzyme was verified. The enzyme weighs 29 kDa at the molecular level. Acid invertase functions best at a pH of 3.0 and a temperature of 45 °C. Activation energy of 29.5 kJ mol−1 and K m and V max values of 0.5 mM and 119.7 µmol. min−1. mg−1 of protein was found for the isolated enzyme. It was shown that the mercaptide-forming agent p -chloromercuribenzoic acid (PCMB; 0.5 mM) and the enzyme's activity were both modestly increased by Ca2+, Mn2+, and Mg2+ ions but inhibited by Hg2+, Cd2+, and Pb2+ ions. At elevated temperatures, the invertase exhibited an increase in thermostability due to an increase in activation entropies (∆Sº) and a decrease in activation enthalpies (∆Hº). The interactions between 4 M urea and α-chymotrypsin were tetraphasic, causing periodic increases and decreases in invertase activity. It also suggests a potential explanation for acid-invertase thermal inactivation at high temperatures. This enzyme might be a catabolite-resistant invertase to produce high-gravity ethanol or fructose syrup. [Display omitted] • Acid invertase was purified from Lathyrus aphaca seedlings with molecular weight 29 kDa. • Acid invertase free in a solution of 5% (w/v) sucrose, pH 3.0, is stable up to 50 °C for a period of 4 h. • The K m and V max values for acid invertase was 0.5 mM and 119.7 µmol. min-1.mg−1 of protein. • The acid invertase is more stable and their energy of deactivation are 107 kJ/mol (25 kcal/mol), respectively. • The effects of α-chymotrypsin and 4 M urea were tetraphasic with periodic gain and loss of enzyme activity. [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]

High-entropy carbide ceramic materials exhibited excellent thermal and mechanical properties, making them highly sought after in high-temperature applications. However, the oxidation resistance of high-entropy carbide ceramic needed to be further improved. This work unraveled the oxidation behavior and mechanism of high-entropy carbide ceramic by introducing the Cr 3 C 2. The results indicated that the oxidation rate of (TiZrTaNbCr)C initially decreased with temperature up to 900 °C, followed by an increased with further temperature rise up to 1100 °C. At 800 and 900 °C, the parabolic oxidation rate constants were 0.70 and 0.17 mg2cm−4min−1, respectively. And the minimum thickness of oxidized layer was 60 µm at 900 °C for 120 min. This unusual phenomenon suggested the formation of different oxidation products. Specifically, the CrNbO 4 and Nb 2 Zr 6 O 17 oxide layer were formed at 900 °C, leading to an increased resistance to oxygen diffusion. Subsequently, loose oxidation products of Nb 2 O 5 were formed after 1000 °C, hindering the oxidation resistance. In the current study on oxidation resistance of high entropy carbides, this work showed a competitive performance. Overall, this study illustrated the oxidation mechanism and behavior of (TiZrTaNbCr)C and proposed a new avenue for the design of high-entropy ceramic components. [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]

The mechanical and thermal properties of ZrC x are strongly dependent on the composition and microstructure. In the present study, densified ZrC x (x = 0.5, 0.7 and 1.0) with relative density in the range of 99.2–99.7% have been prepared by a combination of spark plasma sintering (SPS) and vacuum arc melting (VAM). Both the Young's modulus and Vickers hardness monotonically increase with increasing C/Zr ratio. The maximum Young's modulus and Vickers hardness values of 488.1 ± 13.4 GPa and 28.8 ± 1.7 GPa, respectively, for dense ZrC have been obtained. With increasing the C/Zr ratio, the thermal conductivity of ZrC x increases. The thermal conductivity ZrC ranged from 25.17 W/m/K to 43.85 W/m/K from ambient to 1200 °C. Owing to the higher density of ZrC x , the present thermal conductivities and Young's modulus of ZrC x are higher than those of the previous studies. The present results are beneficial to design and preparation of ZrC x ceramics. [ABSTRACT FROM AUTHOR]

Flexible SiC nanowire aerogel felt has excellent foldability, high-temperature resistance, and thermal insulation properties. However, the large-scale and high-efficiency production of SiC nanofiber aerogel felt remains a challenge. In this work, a three-dimensional network-structured short-chopped carbon fiber felt was used as a template for preparing SiC nanowire aerogel felt. The short-chopped carbon fibers were combed and dispersed using an airflow in a carding machine to obtain the desired felt. This method enables rapid and uniform preparation of carbon fiber felt, enhancing the efficiency of SiC nanowire aerogel felt production. The experimental results showed that the aerogel felt was mainly composed of β-SiC nanowires with a density of 5.29 g/cm3. Additionally, the SiC nanofiber aerogel felt exhibited remarkable superelasticity and low thermal conductivity (0.013 W/m·K). This research contributes to the practical application of flexible SiC nanowire aerogel felt in the field of thermal insulation. • Carding machine dispersed carbon fiber. • Fabrication of large size SiC nanofiber aerogel felt. • SiC nanofiber aerogel felt has flexibility and low thermal conductivity. [ABSTRACT FROM AUTHOR]

A novel NbSi 2 /Nb 2 O 5 -SiO 2 /MoSi 2 multilayer thermal protection ceramic coating is designed and fabricated via halide-activated pack cementation and liquid-plasma-assisted particle deposition and sintering technology, endowing the coating with multiple high-temperature protective properties. The incorporation of MoSi 2 nanoparticles not only gives superior high-temperature oxidation resistance/hot corrosion resistance of coating by forming a dense SiO 2 barrier layer, but also promotes passive radiative heat dissipation. When NbSi 2 /Nb 2 O 5 -SiO 2 /MoSi 2 coating was prolonged exposure to air at 1250 °C for 50 h of oxidation and at 900 °C for 100 h of corrosion, the mass gains are only 0.37 mg/cm2 and − 0.52 mg/cm2, respectively. The multilayer coating exhibits enhanced emissivity (>0.88) over the thermal infrared range of 3–20 µm, due to the lattice vibrational absorption-matching synergy of Nb 2 O 5 , SiO 2 , and MoSi 2 , as well as the mutual doping of SiO 2 /Nb 2 O 5 , mismatch of atoms at the interface, and a high degree of lattice distortion within the coating. [ABSTRACT FROM AUTHOR]

We perform a simulation study of hydrogen injection in a depleted gas reservoir, to assess the geomechanical impact of hydrogen storage, relative to other commonly injected gases (methane, CO 2). A key finding is that the differences in hydrogen density, compressibility, viscosity and thermal properties, compared to the other gases, result in significantly less thermal perturbation at reservoir level. The risks of fault reactivation and wellbore fractures due to thermally-induced stress changes are significantly lower when storing hydrogen compared to results observed in CO 2 scenarios. This implies that hydrogen injection and production has a much smaller geomechanical footprint, with benefits for operational safety. We also find that use of nitrogen cushion gas ensures efficient deliverability and phase separation in the reservoir. However, in this study, a large fraction of cushion gas was back-produced in each cycle, demonstrating the need for further studies of the surface processing requirements and economic implications. [Display omitted] • Geomechanical modelling assesses the risks associated with hydrogen storage. • Diffusivity, dissolution and methanogenesis have negligible effect on models. • Thermal perturbations associated with storage alter fracture pressures. • Significant mixing of hydrogen with cushion gas is observed. • Hydrogen storage presents less geomechanical risk than CO 2 or methane storage. [ABSTRACT FROM AUTHOR]

Improvement in thermal stability is especially important for the oxide/oxide composites, which are widely applied at high temperatures. Herein, the continuous alumina fiber reinforced alumina matrix (Al 2 O 3 /Al 2 O 3) composites were fabricated at 1200–1400 °C using Al 2 O 3 powders with a mean size of 0.6 μm. The Al 2 O 3 /Al 2 O 3 composite fabricated at 1300 °C achieved a high flexural strength of 392.9 ± 20.1 MPa and a high interlaminar shear strength of 20.6 ± 1.0 MPa. After exposure at 1000 °C for 100 h and 1400 °C for 10 min, the 1300 °C fabricated Al 2 O 3 /Al 2 O 3 composite showed no significant reduction in mechanical properties. A slight decrease in mechanical properties was observed after aging at 1200 °C for 100 h. The high strength retention after the heat treatment benefited from the coarse Al 2 O 3 powders, which could not be easily sintered at high temperatures. This work can expand the selection of the Al 2 O 3 /Al 2 O 3 composites for potential applications at service temperatures as high as 1400 °C for a short term. [ABSTRACT FROM AUTHOR]

Current highly integrated devices require heat interface materials with excellent heat conductivity. A simple approach was employed to synthesize thermally conductive and outstanding thermal stability nanocomposite. Calcium carbonate nanoparticles (nano CaCO 3) reinforced with reduced graphene oxide (rGO) nanoparticles (rGO/CaCO 3) are synthesized using a novel process, and the effect of rGO in CaCO 3 structure is examined by Field Emission Scanning Electron Microscope, X-ray diffraction, TGA-DTA, and thermal conductivity. The experimental results show that adding rGO resulted in higher crystallinity and thermal stability. As the wt.% of rGO increases from 1 to 5%, the crystallite size was suppressed by 21.06%, 27.39%, 32.48%, 41.5%, and 45.30%, respectively, compared to the pure nano-CaCO 3. Additionally, rGO enhances the thermal conductivity by 35.31% and thermal diffusivity to 1.834 mm2/s by adding 5% rGO. [ABSTRACT FROM AUTHOR]

Melt-quenching techniques were employed to produce a series of Nd 2 O 3 doped Al 2 O 3 –Na 2 O–WO 3 –B 2 O 3 glasses. Structure, optical, and thermal properties were investigated to illustrate the effectiveness of the Nd3+ ions in enhancement performance and analyze their behaviour. Nd 2 O 3 demonstrably contributed to the composite, as evidenced by evaluating all features. The density marginally rises with the addition of Nd 2 O 3 instead of B 2 O 3. The relevant physical characteristics had been calculated. The structure was analyzed by FTIR measurement and identified the vibration modes of varied concentrations. From FTIR spectra, N 4 values were reckoned, and the conversion of the network structure unit from BO 3 to BO 4 was verified. Numerous significant peaks have been caught in the absorption bands of the UV–Vis–NIR measurement. Optical bandgap and band tail are determined. DSC measurements were utilized to identify the thermal characteristics. As Nd3+ ions increased, glass thermal stability improved. Overall, the Nd3+ ion modifier rule was realized. [ABSTRACT FROM AUTHOR]

Among the family of high-quality fiber materials, mullite fiber membrane is a promising one that possesses abilities of both the thermal resistance and oxidation resistance under high temperature. High-purity mullite nanofibrous membranes were prepared by electrospinning method with low-cost aluminum chloride hexahydrate (AC) as the aluminum source. The effects of sintering temperature and AC content on the phase structure, microstructure, thermal and mechanical properties of the mullite nanofibrous membranes were investigated. The results show that the sintering temperature as low as 1000 °C is the very appropriate temperature for obtaining the high-purity mullite nanofibers with smooth surface. The minimum thermal conductivity of 0.029 W m−1 K−1 and maximum tensile strength of 6.11 MPa are gained from the mullite nanofibrous membranes with AC content of 2 mmol. The mullite nanofibrous membranes with excellent properties can be selected as an ideal candidate for thermal insulation and reinforced applications. [ABSTRACT FROM AUTHOR]

Zirconium carbide (ZrC) disks were fabricated using binder jet printing to study the effect of powder feedstock, print parameters, and heat treatment on flowability and final materials properties. A median volumetric particle size smaller than 10 μm was shown to cause the powder to stop flowing during printing. Disks were printed using ZrC with suitable flowability and then heat-treated at temperatures between 1800 °C and 2200 °C for 1 or 5 h. The density, part shrinkage, thermal diffusivity, and fracture strength all increased with increasing temperature and time. The heat-treated disks were then heated to 2200 °C for 5 h and the properties converged for disks of the same particle size, indicating the hottest temperature and longest time of exposure dictates the final properties. Lastly, it was shown that larger particles produce lower density materials with worse thermal diffusivity, most likely because of poor connectivity between particles after heat treatment. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of (1-x)K 0.5 Bi 0.5 TiO 3 - xBaTiO 3 [(1-x)KBT - xBT] were synthesized using a solid-state reaction pathway. X-ray diffraction analysis confirmed the presence of a single-phase perovskite structure. To explore relaxation and conduction mechanisms, complex impedance spectroscopy was employed. Reduction in Curie temperature was observed as BT content increased. The grain and grain boundary contributions to relaxation was examined through complex impedance and modulus plots and quantified via fitting experimental data to an equivalent circuit model. Examination of the Complex impedance spectra uncovered the existence of dielectric relaxation characteristic of a non-Debye nature. Furthermore, the activation energy determined suggests commonalities in governing the conduction and relaxation processes in relation to temperature-dependent conductivity and relaxation time. A negative temperature coefficient of resistance behaviour was obtained from the temperature-dependent conductive study. Dielectric spectra revealed that these ceramic capacitors are useful in reduction of signal interference, signal attenuation and impedance matching circuits applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Upcycling materials were produced composite using clothing waste and PCMs. • Clothing waste, without sorting, was utilized in specimens via a physical process. • The composites demonstrated enhanced latent heat storage capacity. • Clothing waste is valuable for building due to its high insulation. The current volume of clothing waste reached 115 million tons in 2021 and is projected to increase to approximately 150 million tons by 2030. This significant surge in clothing waste has prompted heightened discussions regarding environmentally friendly recycling methods. Clothing presents complex properties, posing substantial challenges to recycling and usually resulting in environmental pollution when disposed. In this study, our recycling approach capitalizes on the differing melting points of textiles. This transformation was achieved through a physical process that included an opening procedure and high temperature heat compression. Textile materials exhibit exceptional thermal properties. Through experimentation on 50 g fiber specimens, thermal conductivities similar to commercial insulation materials were observed, registering an average of 0.0592 W/m·K at 20 °C and 0.06053 W/m·K at 40 °C. This study explores the impregnation of phase change materials (PCMs) into clothing waste-based specimens, equipping them with heat storage capabilities. During the experimental phase, we employed three distinct types of PCMs to evaluate their thermal properties and heat storage capacities in relation to their respective melting temperatures. Through thermal properties analysis, we determined the latent heat capacity of each specimen, ranging from a minimum of 6.63 J/g to a maximum of 75.81 J/g. Our observations indicated a reduction in peak temperature and time-leg effects attributable to the use of PCMs for surface heat flow. This research underscores the superior thermal performance of construction and building materials derived from clothing waste, enhanced by the integration of PCMs, when compared to traditional materials and other waste-derived alternatives. [ABSTRACT FROM AUTHOR]

Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model. [Display omitted] [ABSTRACT FROM AUTHOR]

Conducting in-situ measurements of planetary environments is a key scientific goal in the geoscience field for the extraterrestrial exploration, such as the Moon or Mars. Among these measurements, determining the thermal properties of regolith is particularly challenging due to the material's inhomogeneities. In this paper, an active thermal probing technique is proposed, utilizing a transient hot-wire technique with a needle-like probe structure integrated with temperature sensors and a heater. It is capable of measuring in-situ temperature variations and inner heat flux without disturbing the surrounding regolith. In addition, a machine-learning-based method is proposed for inverting in-situ thermophysical properties, including density, thermal conductivity, and heat capacity. An embedded artificial neural network model has been developed and trained with data sets from both finite element simulations and experiments. This machine learning model is capable of efficiently predicting temperature responses for different lunar regolith simulants. For total 12 parameters, the errors of ten cases are less than 10%, and other two cases are 12.23% and 13.17%. Finally, the proposed method is verified by heat measurement experiments under normal pressure and vacuum, and the variation of thermal properties with different compactness is obtained. The proposed probing technique provides novel ideas to measure the in-situ thermal properties of extraterrestrial regolith. [ABSTRACT FROM AUTHOR]

Anorthite ceramics (CaAl 2 Si 2 O 8) was obtained by slip casting of water suspension of kaolin (Al 2 O 3 ·2SiO 2 ·2H 2 O) and CaCO 3 as a source of CaO. A relative density of 87 % of the theoretical density was achieved after a 3-h-long sintering of green samples at 1200 °C. It was found that slip casting allows the fabrication of anorthite with relatively small pores (<8 μm) which was beneficial for achieving a high fracture strength of 129 MPa and good thermal shock resistance. For a quantitative measurement of thermal shock resistance, a critical temperature interval (ΔT c) was determined by a reduction in the mean fracture strength of at least 30 %. The experimentally determined ΔT c of 300 °C was higher than the value calculated by the equation assuming that the thermal stress created during quenching causes the fracture. It was found that the discrepancy between experimental and calculated values of ΔT c could be explained by an introduction of cracks of various sizes by indentation method and careful observation of crack growth initiation after quenching from various temperatures. It is believed that the reason for the discrepancy lies in the different nature of stress that was used in the theoretical calculation and the stress that acts during sample quenching. [ABSTRACT FROM AUTHOR]