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Low thermal conductivities and high thermal expansion coefficients are desirable for rare-earth zirconate thermal barrier coating materials. Introduction of cation doping and adjustment of the nonstoichiometry are efficient methods for enhancing the thermophysical characteristics of materials. Herein, the thermophysical properties of Yb3+-doped nonstoichiometric gadolinium zirconate ceramic materials were investigated using first-principles calculations and solid-state reaction techniques. As the Yb3+ content increases, additional cations enter the interstitial spaces (for excess Gd3+ gadolinium zirconate) and form vacancy defects (for excess Zr4+ gadolinium zirconate), which serve as phonon scattering centres to decrease the thermal conductivity. When Yb3+ is doped at the same concentration, gadolinium zirconate with excess Zr4+ exhibits a lower thermal conductivity. Specifically, Gd 1.875 Yb 0.25 Zr 2.125 O 7 shows the lowest minimum thermal conductivity of 1.133 W/(m⸱K) (according to the Clark model) and 1.241 W/(m⸱K) (according to the Cahill model). In addition, the experimental results also suggest that the optimal content of Yb3+ is 0.25 excess Zr4+ gadolinium zirconate, which has the lowest intrinsic thermal conductivity of 1.037 W/(m⸱K) at 1300 K. Moreover, the thermal expansion coefficient of the Yb3+-doped excess Gd3+ nonstoichiometric material is greater than that of the doped excess Zr4+ material, this is due to the greater electronegativity difference between Yb3+ and Zr4+ than that between Yb3+ and Gd3+ and the lower binding energy of Gd-O than that of Zr-O. The experimental results and the calculated results are in good agreement. The aim of this work is to enhance the thermophysical characteristics of gadolinium zirconate ceramics for use as thermal barrier coating materials. [ABSTRACT FROM AUTHOR]

To simulate the influence of rainfall on the internal forces of expansive soil slope retaining structures, an approximate calculation method for the humidity stress field of expansive soil is proposed in this study. Considering both rainy and non-rainy conditions, on a high expansive soil slope, a numerical model is constructed for a combining supporting structure, which is composed of upper and lower anti-sliding piles and anchor rods/cable frames. Furthermore, the distribution of internal forces in the retaining structure is studied, and design optimization is performed. The research findings reveal that the bending moment profile along the longitudinal axis of the lower anti-sliding pile demonstrates a distinctive "W" pattern, which is characterized by initial reduction, following augmentation, a subsequent reduction, and final amplification. In contrast, the upper anti-sliding pile experiences an ascending trend, followed by a descending trend, and then a subsequent ascending trend. Interestingly, the introduction of rainfall grants an escalation in both the shear force exerted along the entire length of the upper and lower anti-sliding piles and the bending moment encountered by the lower anti-sliding pile. The determination of the internal force distribution of the expansive soil slope retaining structures under different conditions, using the proposed calculation method, provides a further optimization in their design. [ABSTRACT FROM AUTHOR]

Mg-Y-Zn-Al alloys processed by the rapidly solidified ribbon consolidation (RSRC) technique are candidate materials for structural applications due to their improved mechanical performance. Their outstanding mechanical strength is attributed to solute-enriched stacking faults (SESFs), which can form cluster-arranged layers (CALs) and cluster-arranged nanoplates (CANaPs) or complete the long-period stacking ordered (LPSO) phase. The thermal stability of these solute arrangements strongly influences mechanical performance at elevated temperatures. In this study, an RSRC-processed Mg—0.9%, Zn—2.05%, Y—0.15% Al (at%) alloy was heated at a rate of 0.666 K/s up to 833 K, a temperature very close to melting point. During annealing, in situ X-ray diffraction (XRD) measurements were performed using synchrotron radiation in order to monitor changes in the structure. These in situ XRD experiments were completed with ex situ electron microscopy investigations before and after annealing. At 753 K and above, the ratio of the matrix lattice constants, c/a, decreased considerably, which was restored during cooling. This decrease in c/a could be attributed to partial melting in the volumes with high solute contents, causing a change in the chemical composition of the remaining solid material. In addition, the XRD intensity of the secondary phase increased at the beginning of cooling and then remained unchanged, which was attributed to a long-range ordering of the solute-enriched phase. Both the matrix grains and the solute-enriched particles were coarsened during the heat treatment, as revealed by electron microscopy. [ABSTRACT FROM AUTHOR]

A novel (Nd 0.2 Sm 0.2 Eu 0.2 La 0.2 Dy 0.2) 2 Gd 0.5 Yb 0.5 TaO 7 high-entropy oxide was successfully prepared through the sol–gel and high-sintering technique. The synthesized powder has a single-lattice structure, and the bulk sample has sole pyrochlore-type lattice. Given the particularity structure and the high concentration of oxygen vacancies caused by ion doping, the (Nd 0.2 Sm 0.2 Eu 0.2 La 0.2 Dy 0.2) 2 Gd 0.5 Yb 0.5 TaO 7 's thermal conductivity (1.385–1.187W·m−1·K−1) is lower than those of (La 1/6 Nd 1/6 Yb 1/6 Y 1/6 Sm 1/6 Lu 1/6) 2 Ce 2 O 7 , Sm 2 Zr 2 O 7 , and Sm 2 Ce 2 O 7. Its excellent phase stability and suitable coefficient of thermal expansion (～10.80 × 10−6 K−1, ～1200 °C) also indicate its potential as candidate oxide for thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Rare‐earth hafnates are gaining attention due to their excellent high‐temperature phase stability and low thermal conductivity. However, they still have shortcomings of low thermal expansion and poor calcium‐magnesium‐aluminum‐silicate (CMAS) corrosion resistance. In this study, we employed high‐entropy engineering and component design to synthesize three high‐entropy hafnates (La0.2Ce0.2Nd0.2Gd0.2T0.2)2Hf2O7 (T = Dy, Ho, Tm) as well as a single‐component hafnate Nd2Hf2O7, with the aim of preparing thermal barrier coatings with an excellent comprehensive performance. Test results indicate that the high‐entropy compositions have excellent thermal properties. The focus is on elucidating the corrosion process and failure mechanism of CMAS at 1300°C. Moreover, the analysis of residual CMAS and corrosion products was conducted to evaluate the discrepancies in CMAS corrosion behavior among the various compositions. [ABSTRACT FROM AUTHOR]

In order to meet the sealing temperature of copper alloy below 1000 °C, a kind of Li 2 O-ZnO-SiO 2 -P 2 O 5 -(B 2 O 3 +Al 2 O 3 +K 2 O) (LZS) glass-ceramics with high expansion coefficient and high resistivity was synthesized via the melting method and then crystallized through controlled cooling. The network structure, thermal properties, crystal phase transition, thermal expansion coefficient, and high-temperature resistivity have been investigated. As the mass ratio of ZnO/Li 2 O increases, the network structure of the LZS glass is strengthened, leading to an increase in the glass transition and crystallization temperature. Moreover, the predominant crystal phases in LZS glass-ceramics transit from Li 2 SiO 3 to Zn[Zn 0.1 Li 0.6 Si 0.3 ]SiO 4 and subsequently to Zn 2 SiO 4. At a ZnO/Li 2 O ratio of 3, a cristobalite phase with a high expansion coefficient emerges. The change in crystal phase results in a variation in the coefficient of thermal expansion (CTE) of glass-ceramics, ranging from 13.2 to 11.2 × 10−6 K−1. At a ZnO/Li 2 O ratio of 3, the softening temperature of glass-ceramics is minimized. Moreover, as the ZnO/Li 2 O mass ratio increases, the resistance of crystallized glass decreases first and then increases. The maximum resistivity is achieved at a ZnO/Li 2 O mass ratio of 5. By optimizing the mass ratio of ZnO/Li 2 O, it is determined that when the mass ratio of ZnO/Li 2 O is 3, the CTE is 12.4 × 10−6 K−1, and the softening temperature (Ts) is 679.8 °C, which is the best material for sealing applications. [ABSTRACT FROM AUTHOR]

Chromium-plated diamond/copper composite materials, with Cr layer thicknesses of 150 nm and 200 nm, were synthesized using a vacuum hot-press sintering process. Comparative analysis revealed that the thermal conductivity of the composite material with a Cr layer thickness of 150 nm increased by 266%, while that with a Cr layer thickness of 200 nm increased by 242%, relative to the diamond/copper composite materials without Cr plating. This indicates that the introduction of the Cr layer significantly enhanced the thermal conductivity of the composite material. The thermal properties of the composite material initially increased and subsequently decreased with rising sintering temperature. At a sintering temperature of 1050 °C and a diamond particle size of 210 μm, the thermal conductivity of the chromium-plated diamond/copper composite material reached a maximum value of 593.67 W∙m−1∙K−1. This high thermal conductivity is attributed to the formation of chromium carbide at the interface. Additionally, the surface of the diamond particles in contact with the carbide layer exhibited a continuous serrated morphology due to the interface reaction. This "pinning effect" at the interface strengthened the bonding between the diamond particles and the copper matrix, thereby enhancing the overall thermal conductivity of the composite material. [ABSTRACT FROM AUTHOR]

Rare‐earth tantalates present promise as thermal barrier coatings due to their favorable thermodynamic characteristics. To further diminish thermal conductivity, three high‐entropy tantalate samples, namely (Ce0.2Nd0.2Sm0.2Eu0.2Lu0.2)3TaO7, (Nd0.2Sm0.2Eu0.2Gd0.2Tm0.2)3TaO7, and (Ce0.2Nd0.2Sm0.2Eu0.2Dy0.2)3TaO7, denoted as HE‐1, HE‐2, and HE‐3, respectively, were synthesized in this investigation. HE‐1 exhibits a low thermal conductivity of 1.46 W/(m·K)–1 at 1000°C. The rationale behind this reduced thermal conductivity is expounded via the phonon scattering mechanism. The introduction of atomic disparities and grain size inhomogeneity, attributable to high‐entropy doping, collaborates to enhance phonon scattering, culminating in the lowest thermal conductivity. HE‐3, on the other hand, possesses a notable thermal expansion coefficient of 11.6 × 10−6 K−1 at 1200°C and manifests pronounced anisotropy in CTEs. All three high‐entropy samples demonstrate commendable mechanical properties, with Young's modulus lower than that of single‐component rare‐earth tantalates, while simultaneously exhibiting high hardness values (>8.4 GPa). This work furnishes a valuable reference for the utilization of high entropy rare‐earth tantalates in the realm of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

This study aims to investigate the thermomechanical properties of vanadium dioxide (VO2) thin films. A VO2 thin film was simultaneously deposited on B270 and H-K9L glass substrates by electron-beam evaporation with ion-assisted deposition. Based on optical interferometric methods, the thermal–mechanical behavior of and thermal stresses in VO2 films can be determined. An improved Twyman–Green interferometer was used to measure the temperature-dependent residual stress variations of VO2 thin films at different temperatures. This study found that the substrate has a great impact on thermal stress, which is mainly caused by the mismatch in the coefficient of thermal expansion (CTE) of the film and the substrate. By using the dual-substrate method, thermal stresses in VO2 thin films from room temperature to 120 °C can be evaluated. The thermal expansion coefficient is 3.21 × 10−5 °C−1, and the biaxial modulus is 517 GPa. [ABSTRACT FROM AUTHOR]

Using copper-boron alloy as the metal matrix and different-sized diamond particles through 110 μm, 230 μm to 550 μm as reinforcement, the diamond/copper-boron alloy composites were prepared via gas pressure infiltration technology under 1100 ℃ and 10 MPa gas pressure. The influences of the size of diamond particles on the configuration, interlayer phase distribution, and thermophysical properties of the composites were investigated. The results show that with the increase of particle size, there is a benefit of better interface bonding, and the thermal conductivity of the diamond/copper-boron composite is enhanced while the thermal expansion coefficient decreases. When the diamond particle size is 500 μm, the best performance of the composite is obtained. The thermal conductivity is 680.3 W/(m·K), and the thermal expansion coefficient increases from 4.095×10−6 K−1 to 7.139×10−6 K−1.

CrTaO4 (or Cr0.5Ta0.5O2) has been unexpectedly found to play a decisive role in improving the oxidation resistance of Cr and Ta-containing refractory high-entropy alloys (RHEAs). This rarely encountered complex oxide can effectively prevent the outward diffusion of metal cations from the RHEAs. Moreover, the oxidation kinetics of CrTaO4-forming RHEAs is comparable to that of the well-known oxidation resistant Cr2O3- and Al2O3-forming Ni-based superalloys. However, CrTaO4 has been ignored and its mechanical and thermal properties have yet to be studied. To fill this research gap and explore the untapped potential for its applications, here we report for the first time the microstructure, mechanical and thermal properties of CrTaO4 prepared by hot-press sintering of solid-state reaction synthesized powders. Using the HAADF and ABF-STEM techniques, rutile crystal structure was confirmed and short range ordering was directly observed. In addition, segregation of Ta and Cr was identified. Intriguingly, CrTaO4 exhibits elastic/mechanical properties similar to those of yttria stabilized zirconia (YSZ) with Young’s modulus, shear modulus, and bulk modulus of 268, 107, and 181 GPa, respectively, and Vickers hardness, flexural strength, and fracture toughness of 12.2±0.44 GPa, 142±14 MPa, and 1.87±0.074 MPa·m1/2. The analogous elastic/mechanical properties of CrTaO4 to those of YSZ has spurred inquiries to lucrative leverage it as a new thermal barrier material. The measured melting point of CrTaO4 is 2103±20 K. The anisotropic thermal expansion coefficients are αa = (5.68±0.10)×10−6 K−1, αc = (7.81±0.11)×10−6 K−1, with an average thermal expansion coefficient of (6.39±0.11)×10−6 K−1. The room temperature thermal conductivity of CrTaO4 is 1.31 W·m−1·K−1 and declines to 0.66 W·m−1·K−1 at 1473 K, which are lower than most of the currently well-known thermal barrier materials. From the perspective of matched thermal expansion coefficient, CrTaO4 pertains to an eligible thermal barrier material for refractory metals such as Ta, Nb, and RHEAs, and ultrahigh temperature ceramics. As such, this work not only provides fundamental microstructure, elastic/mechanical and thermal properties that are instructive for understanding the protectiveness displayed by CrTaO4 on top of RHEAs but also outreaches its untapped potential as a new thermal barrier material.

This work investigates the influence of composition on the thermal properties of the high entropy alloy family Cu5Cr35Fe35V20-X5 (at. %), where X = Ti, Ta, W or Mo in the framework of acting as a thermal barrier between the W-based plasma-facing elements and the CuCrZr or Cu-based heat sink components of the fusion reactor. The alloys were produced by arc melting and their microstructure and mechanical properties were previously characterized by XRD, SEM, and Vickers hardness measurements. Thermal properties have been measured on as-cast at thermally treated alloys using the laser flash method in the temperature range 25 °C to 600 °C to determine the thermal diffusivity, α, thermal conductivity, λ, and specific heat, Cp. Dilatometry experiments were also carried out to obtain the linear thermal expansion coefficient, CTE, as a function of temperature.For all materials, the thermal conductivity increases with temperature from 15 W/m·K at RT to 28 W/m·K at 600 °C and does not significantly depend on the thermal treatment for the Mo-HEA and W-HEA, but increases after aging for the Ta-HEA and Ti-HEA. These values are lower than those of W (∼122 W/m·K at 600 °C) and much lower than for CuCrZr-IG (∼354 W/m·K at 400 °C). The thermal expansion coefficients of these HEAs, ∼10 × 10−6 °C−1 at RT and ∼ 2 × 10−6 °C−1 at 650 °C are between those of CuCrZr and the W for the entire operative temperature range. These results indicate that the Cu5Cr35Fe35V20-X5 (X = Ti, Ta, W, Mo) HEAs have a promising combination of the thermophysical properties, λ, Cp and CTE, to act as thermal barrier in plasma-facing components that require the union of W- and Cu-based materials.

Developing highly reliable infrared radiation materials with broadband high emissivity at high temperatures, low thermal conductivity, and excellent thermal stability is highly desirable for aerospace thermal protection applications. However, it remains a huge challenge to take into account infrared radiation heat dissipation and blocking heat transfer through low thermal conduction simultaneously. In this work, we reported a broadband high emissivity Ca2+-doped YbCrO 3 ceramic with emissivity above 0.89 at room temperature across the entire range of wavelength (1–14 μm). This doping strategy leads to the introduction of impurity energy levels into the band gap of YbCrO 3 , which increases the possibility of light absorption to promote electron transition, improving the emissivity of the near-infrared band (1–3 μm). Simultaneously, un-equivalent doping induces electron exchange between chromate ceramic ions, which complicates the electronic structure (producing lattice distortion and extra multi-mode vibrations) and reduces the band gap width, thus boosting the emissivity in the mid-infrared band (3–14 μm). More importantly, (Yb 0.8 Ca 0.2)CrO 3 presents a high emissivity (0.76) at an elevated temperature of 1200 °C, together with low thermal conductivity (2.5 W m−1 K−1 at 1000 °C) due to strong phonon scattering. Moreover, the doping-dominating phase stabilization effect contributes to impressive thermal stability (stable at 1300 °C for 50 h) and a high coefficient of thermal expansion (9.0–9.5 × 10−6 K−1), which makes it suitable for long-term high-temperature thermal protection application. All these merits render the development of thermally stable high-temperature infrared radiation ceramic materials core competitive. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To date, there are very few experimental techniques, if any, that are suitable for the purpose of acquiring quantitative maps of the thermal expansivity of 2D materials and nanostructured thin films with nanoscale lateral resolution in spite of huge demand for nanoscale thermal management, for example in designing integrated circuitry for power electronics. Besides, contactless analytical tools for determining the thermal expansion coefficient (TEC) are highly desirable because probes in contact with the sample significantly perturb any thermal measurements. Here, ω‐2ω near‐field thermoreflectance imaging is presented as a novel, all‐optical, and contactless technique to map the TEC at the nanoscale with precision. Testing of this technique is performed on nanogranular films of gold and multilayer graphene (ML‐G) platelets. With ω‐2ω near‐field thermoreflectance, it is demonstrated that the TEC of Au is higher at the metal‐insulator interface, with an average of (17.12 ± 2.30) ×10−6 K−1 in agreement with macroscopic techniques. For ML‐G, the average TEC is (−5.77 ± 3.79) x10−6 K−1 and is assigned to in‐plane vibrational bending modes. A vibrational‐thermal transition from graphene to graphite is observed, where the TEC becomes positive as the ML thickness increases. The nanoscale method here reported demonstrates results in excellent agreement with its macroscopic counterparts, as well as superior capabilities to probe 2D materials and interfaces. [ABSTRACT FROM AUTHOR]

Copyright of Diamond & Abrasives Engineering is the property of Zhengzhou Research Institute for Abrasives & Grinding and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Solid oxide electrolysis cell (SOEC) industrialization has been developing for many years. Commercial materials such as 8 mol% Y2O3-stabilized zirconia (YSZ), Gd0.1Ce0.9O1.95 (GDC), La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), La0.6Sr0.4CoO3−δ (LSC), etc., have been used for many years, but the problem of mismatched thermal expansion coefficients of various materials between cells has not been fundamentally solved, which affects the lifetime of SOECs and restricts their industry development. Currently, various solutions have been reported, such as element doping, manufacturing defects, and introducing negative thermal expansion coefficient materials. To promote the development of the SOEC industry, a direct treatment method for commercial materials—quenching and doping—is reported to achieve the controllable preparation of the thermal expansion coefficient of commercial materials. The quenching process only involves the micro-treatment of raw materials and does not have any negative impact on preparation processes such as powder slurry and sintering. It is a simple, low-cost, and universal research strategy to achieve the controllable preparation of the thermal expansion coefficient of the commercial material La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) through a quenching process by doping elements and increasing oxygen vacancies in the material. Commercial LSCF materials are heated to 800 °C in a muffle furnace, quickly removed, and cooled and quenched in 3.4 mol/L of prepared Y(NO3)3. The thermal expansion coefficient of the treated material can be reduced to 13.6 × 10−6 K−1, and the blank sample is 14.1 × 10−6 K−1. In the future, it may be possible to use the quenching process to select appropriate doping elements in order to achieve similar thermal expansion coefficients in SOECs. [ABSTRACT FROM AUTHOR]

Spark plasma sintering is a process of rapid, low-temperature, and high-density sintering. Moreover, traditional sintering methods can solve the problems of large grain sizes and low densities. The sintering temperature plays a crucial role in influencing the physical properties of high-silicon–aluminum (Si-Al) composites. This work investigated the impact of temperature on the microstructure, interface, and physical properties of high-Si-Al composites by spark plasma sintering. The results demonstrate that when the powder was processed by ball milling at a sintering temperature of 565 °C, the material exhibited the densest microstructure with minimal pore formation. The average size of the silicon phase is the smallest. The material's thermal conductivity is 134.6 W/m·K, the thermal expansion coefficient is 8.55 × 10−6 K−1, the Brinell hardness is 219 HBW, the density is 2.415 g/cm3, and the density reaches 97.75%. An appropriate sintering temperature facilitates particle rearrangement and dissolution–precipitation processes, enhancing the material structure and performance. [ABSTRACT FROM AUTHOR]

In this paper, non-woven fabric and glass fiber fabric were used to prepare resin-based absorbing composite. The thermal expansion coefficient and the microwave absorbing properties of the absorbing composites with different glass fiber volume fraction were studied. The results show that the simulation results of the thermal expansion coefficient calculated by Schapery model are inconsistent with the experimental results, the metallographic results were studied to reveal that it is the added absorbent in the composite that partially replaced the resin at the interface between resin and fiber bundle causes the parameters of the material substituted in the Schapery model to be improper. A different simulation model was proposed to introduce a set of different parameters of the material to reduce the error between simulation and experiment results and the simulation results show that the error is reduced from a maximum of 53 % to a minimum of 3 %. Meanwhile the microwave absorbing properties show that the absorbing peaks of the composite materials move to low frequency with the increasing glass fiber volume fraction and the minimum reflection loss (RL) first increase and then decrease. The metallographic results show that the different distribution of absorbent in the composites within different reinforced fibers causes the movement of the absorbing peaks and the change of its minimum RL. Those research results lay a foundation for the further popularization and application of the absorbing composites.

The effects of cold rolling reduction ratio, initial grain size, and aging condition (temperature and time) on static strain aging (SSA) behavior were systematically investigated in stable austenitic stainless steel. The aging treatment increased the yield strength (YS) and ultimate tensile strength (UTS), and the SSA effect was more pronounced at higher reduction ratio or smaller initial grain size. The SSA effect occurred in the temperature range of 400∼600 °C, where the accumulated dislocations remained in the form of wavy boundaries. Quantifying the dislocation density clearly showed that the SSA effect was directly related to the dislocation density. The volume shrinkage and increase in thermal expansion coefficient by aging treatment suggested the correlation between SSA behavior and atomic distribution changes. 3D atom probe tomography analysis clearly exhibited the clustering and segregation of solute C atoms during aging treatment. These results suggest that the SSA effect may be attributed to the interaction between solute C atoms and dislocations. Through grain refinement and optimal aging treatment at 500 °C for 1 h, the YS and UTS were significantly increased by 319 MPa and 230 MPa, respectively, to obtain a non-magnetic stainless steel with ultrahigh YS of up to 1600 MPa.

On the basis of comparison of temperature dependences of lattice parameters of CuCrSe2 and Cu0.5ZrSe2 in the temperature region including transition between phases with centrosymmetric and noncentrosymmetric distribution of copper on positions tetrahedrally coordinated by selenium. It is concluded that the critical factor that ensures the stability of the non- centrosymmetric copper distribution is the covalent interaction between copper and selenium sublattices. This effect is not related to the anisotropy of the elastic constants of the lattice and can be observed in other layered structures with copper tetrahedrally coordinated by chalcogen.

In this work, a new supplementary formula was introduced to modify the Kerner model. This supplementary formula enable the Kerner model to predict the thermal expansion coefficient of multi-phase reinforced composites by normalization of the thermal expansion coefficient, bulk modulus, and shear modulus of the reinforcements. For comparison, the modified Kerner model as well as modified Schapery, the rule of mixtures, and Turner models were used to predict the thermal expansion coefficient of multi-phase reinforced composites 6092 Aluminum Alloy/silicon carbide/β-eucryptite. The results confirm the robustness of the modified Kerner model for predicting the thermal expansion coefficient of composites with multi-phase near-spherical inclusions. It may provide a fine selection to predict the thermal expansion coefficient of multi-phase reinforced metal matrix composites which cannot predict efficiently before.

To simulate the influence of rainfall on the internal forces of expansive soil slope retaining structures, an approximate calculation method for the humidity stress field of expansive soil is proposed in this study. Considering both rainy and non-rainy conditions, on a high expansive soil slope, a numerical model is constructed for a combining supporting structure, which is composed of upper and lower anti-sliding piles and anchor rods/cable frames. Furthermore, the distribution of internal forces in the retaining structure is studied, and design optimization is performed. The research findings reveal that the bending moment profile along the longitudinal axis of the lower anti-sliding pile demonstrates a distinctive “W” pattern, which is characterized by initial reduction, following augmentation, a subsequent reduction, and final amplification. In contrast, the upper anti-sliding pile experiences an ascending trend, followed by a descending trend, and then a subsequent ascending trend. Interestingly, the introduction of rainfall grants an escalation in both the shear force exerted along the entire length of the upper and lower anti-sliding piles and the bending moment encountered by the lower anti-sliding pile. The determination of the internal force distribution of the expansive soil slope retaining structures under different conditions, using the proposed calculation method, provides a further optimization in their design.

TiSi 2 and Ti 5 Si 3 ceramics are high-temperature coating materials that are mainly synthesized using high-purity Ti and Si. In this study, to determine the application potential of TiSi 2 and Ti 5 Si 3 ceramics prepared through Al reduction-electromagnetic directional crystallization (AR-EDC) from Ti-bearing blast furnace slag (TBFS), spent SCR catalysts (SSCs), and diamond wire saw Si powder (DWSSP) for high-temperature coating, the thermal conductivity of AR-EDC-prepared TiSi 2 and Ti 5 Si 3 ceramics was measured. In addition, the effect of dissolved W and Al on the thermal conductivities of TiSi 2 and Ti 5 Si 3 ceramics was investigated. Meanwhile, the thermal conductivities of AR-EDC-prepared TiSi 2 and Ti 5 Si 3 ceramics were compared with those of commercial TiSi 2 and Ti 5 Si 3 ceramics and typical high-temperature coating materials. Additionally, the thermal coefficient expansions of AR-EDC-prepared TiSi 2 and Ti 5 Si 3 ceramics were compared with those of typical high-temperature Ti alloys. The results showed that the heat transfer mode of TiSi 2 ceramics was phonon heat transfer, while that of the Ti 5 Si 3 ceramics was radiation heat transfer, and dissolved W and Al reduced their thermal conductivities. At the temperature range of 298–873K, the thermal conductivities of the TiSi 2 and Ti 5 Si 3 ceramics were 29–35 W/(m·K) and 6–11 W/(m·K), respectively, and their thermal expansion coefficients were 8 × 10−6–12 × 10−6 K−1 and 5 × 10−6 –10 × 10−6 K−1, respectively. These results indicate that the thermal conductivity and thermal expansion coefficient of AR-EDC-prepared TiSi 2 and Ti 5 Si 3 meet the requirements for high-temperature coating. This study shows that Ti 5 Si 3 and TiSi 2 ceramics prepared from Ti- and Si-rich wastes are promising high-temperature coating materials. [ABSTRACT FROM AUTHOR]

The oxygen vacancy formation behavior and electrochemical and thermal properties of Ba0.5Sr0.5Fe1−xMnxO3−δ (BSFMnx, x = 0–0.15) cathode materials were investigated. For thermogravimetric analysis, the weight decreased from 1.98% (x = 0) to 1.81% (x = 0.15) in the 400–950 °C range, which was due to oxygen loss from the lattice. The average oxidation state of the B-site increased, the Oads/Olat ratio decreased, and the binding energy of the Olat peak increased with Mn doping. These results indicate that Mn doping increases the strength of the metal–oxygen bond and decreases the amount of oxygen vacancies in the lattice. The electrical conductivity of BSFMnx increased with the temperature due to the thermally activated small-polaron hopping mechanism showing a maximum value of 10.4 S cm−1 (x = 0.15) at 450 °C. The area-specific resistance of BSFMn0.15 was 0.14 Ω cm2 at 700 °C and the thermal expansion coefficient (TEC) gradually decreased to 12.7 × 10−6 K−1, which is similar to that of Ce0.8Sm0.2O2 (SDC) (12.2 × 10−6 K−1). Mn doping increased the metal–oxygen bonding energy, which reduced the oxygen reduction reaction activity but improved the electrical conductivity and thermal stability with SDC. [ABSTRACT FROM AUTHOR]

Owing to the orientation of grains, textured ceramics possess particular properties along a specific direction. In this study, combining reactive template grain growth (RTGG) and vat photopolymerization, the textured cordierite ceramics with low thermal expansion coefficient (CTE) and custom structure were prepared successfully. Initially, the generation mechanism of the oriented c axis of α-cordierite grains in the XY plane was revealed by analyzing the evolution of microstructure during the sintering process. Then, two printing models were used to investigate the anisotropic CTE of porous cordierite ceramics fabricated by vat photopolymerization, indicating the effect of oriented grains and microstructure on the CTE. Finally, based on the selected dominant model, the controllable oriented microstructure was achieved by altering the shear stress provided by the scraper. The results showed that the oriented α-cordierite grains and skeletons were originated from the oriented tabular talc particles. Owing to the c axis of α-cordierite grains oriented in the XY plane, the CTE of the test direction parallel to the XY plane is lower than that perpendicular to the XY plane. In addition, with decreasing the setting layer thickness to adjust shear force, the oriented degree of tabular talc particles and α-cordierite skeletons became controllable. When the layer thickness reached a minimum of 25 μm, the CTE of porous cordierite ceramic reached the lowest of 1.26 × 10−6 K−1. [ABSTRACT FROM AUTHOR]

Due to the symmetry of their structure and the way they rotate, rolling bearings are often used at high temperatures and high speeds. When the temperature changes, the material properties of the rolling bearing change, which in turn causes the dynamic model equation of the rolling bearing to change. Given the problem in that the conventional dynamic model equation does not consider temperature changes, but because temperature changes cause changes in material performance parameters resulting in differences between the dynamic simulation signals and the actual signals, this paper fully considers three factors, namely, the thermal expansion coefficient, the hardness value, and the friction coefficient. With the influence of temperature changes, a study on the mechanism of the symmetric mechanism-rolling bearing dynamic system considering the influence of temperature factors is proposed. First, combined with the material properties of the rolling bearing, the changes in thermal expansion coefficient, hardness value, and friction coefficient caused by temperature changes were analyzed. Second, the functional relationship expressions obtained above were substituted into the existing conventional dynamic model. Finally, the comprehensive functional relationship formula was substituted into the conventional dynamic model to obtain the rolling bearing dynamic model under temperature difference changes. By studying the mechanism of the symmetric mechanism-rolling bearing dynamic system that considers the influence of temperature factors, this method can undertake a more comprehensive consideration of the dynamic analysis research into rolling bearing fault diagnosis, thereby verifying the effectiveness of the method. [ABSTRACT FROM AUTHOR]

Abstract To date, there are very few experimental techniques, if any, that are suitable for the purpose of acquiring quantitative maps of the thermal expansivity of 2D materials and nanostructured thin films with nanoscale lateral resolution in spite of huge demand for nanoscale thermal management, for example in designing integrated circuitry for power electronics. Besides, contactless analytical tools for determining the thermal expansion coefficient (TEC) are highly desirable because probes in contact with the sample significantly perturb any thermal measurements. Here, ω‐2ω near‐field thermoreflectance imaging is presented as a novel, all‐optical, and contactless technique to map the TEC at the nanoscale with precision. Testing of this technique is performed on nanogranular films of gold and multilayer graphene (ML‐G) platelets. With ω‐2ω near‐field thermoreflectance, it is demonstrated that the TEC of Au is higher at the metal‐insulator interface, with an average of (17.12 ± 2.30) ×10−6 K−1 in agreement with macroscopic techniques. For ML‐G, the average TEC is (−5.77 ± 3.79) x10−6 K−1 and is assigned to in‐plane vibrational bending modes. A vibrational‐thermal transition from graphene to graphite is observed, where the TEC becomes positive as the ML thickness increases. The nanoscale method here reported demonstrates results in excellent agreement with its macroscopic counterparts, as well as superior capabilities to probe 2D materials and interfaces.

Natural fiber reinforced plastics (NFRP) are increasingly used as a sustainable material alternative to glass or carbon fiber reinforced plastics in lightweight solutions. Visible and/or decorative coated components must meet high surface qualities and defects such as fiber print-through due to different expansion behavior of fiber and matrix are not permitted. Various studies investigate the expansion behavior of NFRP under the influence of temperature and humidity on mechanical properties. In contrast, there are no studies that relate these properties to decoratively coated NFRP and the importance for surface quality. The present study aims to fill this gap using a flax fiber reinforced bio-based epoxy resin (FFRP) manufactured by resin transfer molding process (RTM). The surface roughness and the coefficient of thermal expansion (CTE) were determined as a function of the fiber mass fraction. Further, FFRP and carbon fiber reinforced plastics (CFRP) were decoratively coated and subjected to an alternating climate test. The results showed that reducing the fiber mass fraction of an FFRP to 40 % and using a glass-fiber non-woven on the surface, in combination with 50 % fiber mass fraction, were the most promising methods for reducing roughness in the uncoated state. In addition, the FFRP exhibited an increased CTE longitudinally of 11 ppmK−1 and transversely of 105 ppmK−1 to the fiber direction compared to the CFRP (5 and 79 ppmK−1), along with increased roughness of Ra 0.8 compared to 0.6. The effect of fiber print-through was shown for all variants by the stress in the alternating climate test.

Abstract In a short-pulse CO2 laser based on discharge excitation, there is a pulse tail that depends on the device configuration and operating conditions. The pulse tail is longer than the spike pulse and causes thermal effects such as a crack, heat-affected zones (HAZ), and so on. There are various types of glass having different physical constants related to heat, such as the thermal expansion coefficient and the softening point. Even if the same CO2 laser pulse is radiated onto glass, the processing results may differ depending on the glass material. Four types of glass, namely, crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass were irradiated with two types of short CO2 laser pulses, one with a large pulse tail and one with a small pulse tail, at a repetition rate of 200 Hz and a fluence per pulse of 22 J/cm2. As the processing characteristics, the ratios of the surface hole diameter and the HAZ diameter to the irradiation diameter, as well as the drilling depth, were investigated. The pulse-tail energy of the short CO2 laser pulses did not affect the surface hole diameter. In the glasses with small softening points of 740 °C or less, the pulse-tail energy of short CO2 laser pulses affected the HAZ with a large number of pulse irradiations with a total irradiation fluence of 2000 J/cm2 or more. The short CO2 laser pulses with a small tail produced a smaller HAZ than the short CO2 laser pulses with a large tail. In drilling with a large number of pulse irradiations, the short CO2 laser pulses with a small tail produced deeper drilling than the short CO2 laser pulses with a large tail. The glass material did not affect the surface hole diameter and the drilling depth. The glass material affected the HAZ.

The “seesaw relationship” between thermal conductivity and thermal expansion coefficient (CTE) in most high temperature ceramics has become an obstacle to the design of long-life multilayer thermal/environmental barrier coatings (T/EBC). Due to low thermal conductivity and CTE, defect fluorite type high-entropy rare earth (RE) hafnates have drawn a lot of interest for potential application in T/EBC systems. This work designs and synthesizes the (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 with comprehensive thermal performance and investigates the thermophysical mechanism from the phonon scale. In addition to the lattice distortion effect caused by the point defects of multicomponent substitutional atoms in (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7, the oxygen vacancies in the defect fluorite lattice also play a critical role in reducing the thermal conductivity. From microscopic thermal expansion behavior, the low-frequency optic phonons originated from the vibration of RE atoms are the key factors in altering CTE for hafnates. And doping smaller RE ions is beneficial for enhancing the RE–O bond strength and further reducing CTE. The results contribute to the understanding of high-entropy strategic design and suggest that (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)2Hf2O7 is a promising top layer material in the implementation of T/EBC.

In recent years, the MgO-Nd 2 Zr 2 O 7 composite ceramics inert matrix (IM) was proposed as a candidate for the transmutation of Pu and minor actinides (MA) in light water reactors (LWR) or accelerator driven sub-critical system (ADS). To take full advantage of the pyrochlore structure of Nd 2 Zr 2 O 7 to accommodate different types of MA and Pu, in this work, Y and Ce co-doped ω MgO-(1- ω)(Nd 1- x Y x) 2 (Zr 1- x Ce x) 2 O 7 (M-NYZC) composite ceramics used as a candidate IM for inert matrix fuel were prepared by solid-state one-step sintering method at 1500 °C for 3 h. The phase structure and microstructure of M-NYZC composite ceramics were characterized by XRD and SEM-EDS. Also, the thermal physical properties of M-NYZC composite ceramics including the thermal expansion coefficient and thermal conductivity were investigated systematically. Results from XRD and SEM-EDS showed that the magnesium oxide and NYZC pyrochlore solid solution are intermixed well with each other, and the M-NYZC samples present uniform element distribution with a grain size of about 1 μm. Also, the as-prepared samples possessed well densified microstructure, and the average relative density of all samples could exceed 95 %. Moreover, the thermal expansion coefficient and thermal conductivity of 0.5M-0.5NYZC (x = 0, 0.15, 0.2, 0.5, 0.9) samples were located in the range of 13.4 × 10-6–14.4 × 10-6 K-1 and 16.34–3.70 W·m-1·K-1 respectively. By comparison, the thermal physical properties of 0.5M-0.5NYZC samples are superior to that of traditional UO 2 and MOX fuels. It is suggested that the M-NYZC composite ceramics prepared in this study can meet the thermal physical performances of inert matrix fuel. [ABSTRACT FROM AUTHOR]

To optimise the mechanical and thermophysical properties of Gd 3 TaO 7 , Lu3+ doped Gd 3 TaO 7 oxides were synthesised using sol-gel and high-temperature sintering methods. The results show that nanopowders with uniform particle sizes and bulk samples with compact microstructures were successfully obtained. Owing to the decreased order degree of lattice with increasing fraction of Lu3+, the lattice of (Gd 1‒x Lu x) 3 TaO 7 transforms gradually from an ordered pyrochlore (x ≤ 0.5) into a disordered fluorite (x ≥ 0.7). The Young's modulus (174–192 GPa), Vickers hardness (9.9–10.9 GPa), and fracture toughness (2.61–3.68 MPa m0.5) of the bulk samples are superior or comparable to those of Y 2 O 3 -stabilised zirconia (YSZ), which can prolong the service life of thermal barrier coating. The thermal conductivity of (Gd 1‒x Lu x) 3 TaO 7 (0.976–1.628 W m‒1 K‒1, 50–1000 °C), first decreases and then elevates with increasing fraction of Lu3+. Owing to the intensive phonon scattering caused by high-concentration point defects, the thermal conductivity of (Gd 1‒x Lu x) 3 TaO 7 is approximately half that of YSZ. Additionally, the excellent lattice steadiness up to 1400 °C and high average thermal expansion coefficient (≥10.71 × 10‒6 K‒1, 1000–1400 °C) of (Gd 1‒x Lu x) 3 TaO 7 oxides will assist in preventing the premature failure of thermal barrier coating. [ABSTRACT FROM AUTHOR]

High-entropy fluorite oxides (HEFOs) must be evaluated under various test conditions to be used as advanced thermal barrier coating (TBC) materials. This study investigated the chemical valence, lattice parameters, and thermal expansion coefficient (TEC) of an HEFO (Zr 0.2 Ce 0.2 Hf 0.2 Y 0.2 Al 0.2)O 2-δ heated and cooled between 1200 °C and 1500 °C in air. Thermogravimetry-differential scanning calorimetry (TG-DSC) was used to probe the temperature ranges of the reduction and oxidation reactions, and X-ray photoelectron spectroscopy was used to determine the valence states of the chemical elements. In-situ high-temperature X-ray diffraction was used for examining the crystal phase and calculating the TECs. The results show that chemical valences related to Zr, Hf, Y, and Al oxidation states were maintained during the entire thermal cycle, whereas these for Ce underwent partial valence transitions. In other words, Ce4+ was partially reduced to Ce3+ when heated from (1200–1300) °C, and Ce3+ was partially re-oxidized to Ce4+ as the temperature increased from 1400 °C to 1500 °C. Such chemical reactions correlate well with the TG-DSC results. The TEC values ranged from (9.58–9.28) × 10−6 K−1 and exhibited a weak, nonlinear dependency on temperature, decreasing with an increase in temperature, except when heated from 1200 °C to 1240 °C. The reduction and oxidation reactions had a minor effect on the TEC and the differences due to heating and cooling were appreciable yet subtle when compared to that at the same temperature, with the maximum difference being less than 0.2 × 10−6 K−1. [ABSTRACT FROM AUTHOR]

In a short-pulse CO2 laser based on discharge excitation, there is a pulse tail that depends on the device configuration and operating conditions. The pulse tail is longer than the spike pulse and causes thermal effects such as a crack, heat-affected zones (HAZ), and so on. There are various types of glass having different physical constants related to heat, such as the thermal expansion coefficient and the softening point. Even if the same CO2 laser pulse is radiated onto glass, the processing results may differ depending on the glass material. Four types of glass, namely, crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass were irradiated with two types of short CO2 laser pulses, one with a large pulse tail and one with a small pulse tail, at a repetition rate of 200 Hz and a fluence per pulse of 22 J/cm2. As the processing characteristics, the ratios of the surface hole diameter and the HAZ diameter to the irradiation diameter, as well as the drilling depth, were investigated. The pulse-tail energy of the short CO2 laser pulses did not affect the surface hole diameter. In the glasses with small softening points of 740 °C or less, the pulse-tail energy of short CO2 laser pulses affected the HAZ with a large number of pulse irradiations with a total irradiation fluence of 2000 J/cm2 or more. The short CO2 laser pulses with a small tail produced a smaller HAZ than the short CO2 laser pulses with a large tail. In drilling with a large number of pulse irradiations, the short CO2 laser pulses with a small tail produced deeper drilling than the short CO2 laser pulses with a large tail. The glass material did not affect the surface hole diameter and the drilling depth. The glass material affected the HAZ. [ABSTRACT FROM AUTHOR]

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In this study, the primary factors affecting the performance of PcBN (Polycrystalline cubic boron nitride) tool materials were investigated by high temperature/high pressure sintering through the variation of TiB 2 -Sialon volume ratio, the strength of TiB 2 -Sialon binder itself, as well as the matching of the average coefficient of thermal expansion (CTE) with cBN (Cubic boron nitride). The effects of TiB 2 -Sialon on the phase composition, microstructure, and mechanical properties of PcBN composites were studied by X-ray diffraction (XRD), universal testing machine, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the properties of TiB 2 -Sialon binder are analogous to those of the corresponding composites. The phase composition of PcBN composite is not affected by the change of volume ratio. It was found that prepared composite, have TiB 2 rod crystals growing along the (100) plane and Sialon rod crystals growing on the (001) plane. The influence of the volume ratio of TiB 2 -Sialon on the mechanical properties of the composites is principally concerned with the density, mechanical properties, and thermal expansion coefficient of the used binder. The extent to which the binder matches the coefficient of thermal expansion is favorable to the strength of the composite. When the volume ratio of TiB 2 to Sialon was 1:3, the hardness (25.21 GPa, 37.44 GPa) and toughness (7.09 Pa m1/2 and 7.48 Pa m1/2) of TiB 2 -Sialon binder/TiB 2 -Sialon-cBN composites reached the maximum value, and the optimal impact resistance was also achieved. The density of the binder and the composite material was maximized when the volume ratio is 1:4. The average thermal expansion coefficient of the binder hoc tempore matches comparatively with cBN, and the interface bonding is better, displaying the best flexural strength (805.30 MPa and 1059.60 MPa) and wear ratio (2005). Therefore, adjusting the volume ratio of TiB 2 -Sialon within a certain range is beneficial to further enhance the binder's strength and mechanical properties. [ABSTRACT FROM AUTHOR]

The fire effect and performance of bridge pylons under construction were investigated via an analysis conducted on two types of pylons with different wall thicknesses. Three fire scenarios, namely internal fire, external ring fire, and external side fire, were established for a 40 m high section of the bridge pylon under construction. The distribution of fire smoke and temperature was obtained using fire dynamics simulation software for different fire scenarios. In addition, a finite element simulation was performed using the thermal–mechanical coupling method to obtain the temperature, stress, and deformation of the columns. The simulation results demonstrate that the average temperature of the internal fire is higher. The chimney effect extends the height range of temperature influence. In the vertical direction, the temperature decrease curve for the internal fire follows a single negative exponential function, while the external fire adheres to a double negative exponential function. The thickness of the temperature influence in the bridge pylon is extended by heating to approximately 200 mm. The stress value considering the thermal expansion coefficient is nearly 27.5 times that without the expansion coefficient, while the deformation value increases by 1 to 8 times. In conclusion, the calculations of the coupled expansion coefficient are helpful in improving the fire safety of bridge pylons. [ABSTRACT FROM AUTHOR]

In this work, a new supplementary formula was introduced to modify the Kerner model. This supplementary formula enable the Kerner model to predict the thermal expansion coefficient of multi-phase reinforced composites by normalization of the thermal expansion coefficient, bulk modulus, and shear modulus of the reinforcements. For comparison, the modified Kerner model as well as modified Schapery, the rule of mixtures, and Turner models were used to predict the thermal expansion coefficient of multi-phase reinforced composites 6092 Aluminum Alloy/silicon carbide/β-eucryptite. The results confirm the robustness of the modified Kerner model for predicting the thermal expansion coefficient of composites with multi-phase near-spherical inclusions. It may provide a fine selection to predict the thermal expansion coefficient of multi-phase reinforced metal matrix composites which cannot predict efficiently before. [ABSTRACT FROM AUTHOR]

Gas turbines efficiency growth is primarily associated with an increase in the operating temperature of the combustion chamber, which places new stringent requirements on the materials of thermal barrier coatings. Strontium cerate doped with tin SrCe 1- x Sn x O 3 where x = 0.1 ... 0.5, was proposed as a promising material. The research has shown that the lightly doped solid solution SrCe 1-x Sn x O 3 has an orthorhombic Pnma structure at x < 0.3, whereas at a high content of Sn4+ the monoclinic structure P2 1 /m becomes more favorable. Thermogravimetric analysis (TGA) in reducing atmosphere (5%H 2 in Ar) shows no mass lost as a result of unchangeable charge of Ce4+ and Sn4+. An increase in the distortion of the crystal lattice, due to the large difference in the ionic radii of Ce4+ and Sn4+, leads to a deterioration in the symmetry of the crystal lattice, a reduction of thermal conductivity (from 1.9 to 1.4 W m−1 K−1 at 1000 °C) and at the same time, growth of hardness and porosity. The increase in porosity, along with an increase in the required temperature of solid-state synthesis, indicates an enhancement in the melting point of the obtained materials. For the compounds with an orthorhombic structure, the thermal expansion coefficient increases with a growth in the Sn content, achieving a highest point 12.47·10−6 K−1 at 1100 °C for x = 0.3. The combination of the revealed properties and their comparison with advanced refractories makes the solid solution, primarily SrCe 0.5 Sn 0.5 O 3 , a promising material for application as thermal barrier coatings. [ABSTRACT FROM AUTHOR]

The duration of ball milling greatly influences the characteristics of high-silicon–aluminum composite during the ball milling process. This study examines how the microstructure, thermal conductivity, and hardness of a high-silicon–aluminum composite are affected by different ball milling times. We exposed the powder to various durations of ball milling and employed different pellet ratios. Following this treatment, the powder underwent consolidation via discharge plasma sintering. Our findings show that with a pellet ratio of 10:1 and a milling duration of 8 h, the powder particles were refined, resulting in a more uniform and dense material composition. This refined material boasted a thermal conductivity of 111.6 W/m·K, a Brinell hardness of 136.8 HBW, and a density of 2.304 g/cm3. This method facilitates the creation of a uniform composite powder composition. It encourages the development of a fine-grain structure, which enables the production of particle-reinforced composites with superior properties. [ABSTRACT FROM AUTHOR]

In this work, the 3D-SiCp/A356 composites with interpenetrating microstructure were prepared by pressure infiltration of A356 aluminum alloy into a porous 3D-SiC ceramic preform, which served as reinforcement. The effects of the surface oxidation treatment of the SiC particles on microstructure, thermal expansion coefficient, and bending strength of as-fabricated composites were investigated. The results revealed that the initial structure of the 3D-SiC ceramic preform could be retained after pressure infiltration, the pores of the preform were filled with A356 aluminum alloy, and the particles were uniformly distributed in the A356 matrix alloy. The thermal expansion coefficient of the SiC/A356 composite reinforced by oxidized SiC particles was lower than that of the unoxidized SiC particle-reinforced composite. It increased with increasing temperature for both, eventually reaching maxima at 420 °C and 350 °C, respectively, and decreased thereafter. However, a rapid decrease in the thermal expansion coefficient was evident at 565 °C because of the over-burning of the A356 aluminum matrix. In particular, the surface oxidation treatment of SiC particles changed the nature of bonding between SiC and Al, which reduced the strength of the composites. As a result, the bending strength of the unoxidized SiC particle-reinforced composite was approximately twice that of the oxidized SiC particle-reinforced composite. Additionally, the bending strength values of the SiC–Al showed an obvious anisotropic behavior. The bending strength measured by loading parallel to the infiltration direction was 2.5 times larger than that of a perpendicular loading.

Abstract The long‐term stability issue of halide perovskite solar cells hinders their commercialization. The residual stress–strain affects device stability, which is derived from the mismatched thermophysical and mechanical properties between adjacent layers. In this work, we introduced the Rb2CO3 layer at the interface of SnO2/perovskite with the hierarchy morphology of snowflake‐like microislands and dendritic nanostructures. With a suitable thermal expansion coefficient, the Rb2CO3 layer benefits the interfacial stress relaxation and results in a compressive stress–strain in the perovskite layer. Moreover, reduced nonradiative recombination losses and optimized band alignment were achieved. An enhancement of open‐circuit voltage from 1.087 to 1.153 V in the resultant device was witnessed, which led to power conversion efficiency (PCE) of 22.7% (active area of 0.08313 cm2) and 20.6% (1 cm2). Moreover, these devices retained 95% of its initial PCE under the maximum power point tracking (MPPT) after 2700 h. It suggests inorganic materials with high thermal expansion coefficients and specific nanostructures are promising candidates to optimize interfacial mechanics, which improves the operational stability of perovskite cells.

This study aims to investigate the thermomechanical properties of vanadium dioxide (VO2) thin films. A VO2 thin film was simultaneously deposited on B270 and H-K9L glass substrates by electron-beam evaporation with ion-assisted deposition. Based on optical interferometric methods, the thermal–mechanical behavior of and thermal stresses in VO2 films can be determined. An improved Twyman–Green interferometer was used to measure the temperature-dependent residual stress variations of VO2 thin films at different temperatures. This study found that the substrate has a great impact on thermal stress, which is mainly caused by the mismatch in the coefficient of thermal expansion (CTE) of the film and the substrate. By using the dual-substrate method, thermal stresses in VO2 thin films from room temperature to 120 °C can be evaluated. The thermal expansion coefficient is 3.21 × 10−5 °C−1, and the biaxial modulus is 517 GPa.

In the present work, we have used classical molecular dynamics and quantum mechanical density functional theory modeling to investigate the grain size-dependent thermal expansion coefficient (CTE) of nanocrystalline Cu. We find that the CTE increases by up to 20% with a gradually decreasing grain size. This behavior emerges as a result of the increased population of occupied anti-bonding states and bond order variation in the grain boundary regions, which contribute to the reduced resistance against thermally-induced bond stretching and dictate the thermal expansion behavior in the small grain size limit. As a part of the present work, we have established a procedure to produce ab initio thermal expansion maps that can be used for the prediction of the grain size-dependent CTE. This can serve as a modeling tool, e.g., to explore the impact of grain boundary impurity segregation on the CTE. [ABSTRACT FROM AUTHOR]

Chemical bond and defect engineering have profound impact on energy band and crystal structure of materials, which can adjust physicochemical and mechanical properties of materials. Bi Sn and V Sn are simultaneously designed in SnTe material system via the (SnTe) x (Bi 2 Te 3) alloying form, which was realized by vacuum melting and spark plasma sintering technology. Both point defects increase band gap and decrease ΔE L−Σ , which improves obviously Seebeck coefficient of SnTe. The high-efficiency improvement in the middle temperature zone makes average power factor of (SnTe) 24 (Bi 2 Te 3) achieves 1656 μWm-1K−2(323K–773K). Bi Sn induces strong coupling hybridization between Te-5s and Te-5p, and forms the lower bonding state. The lower bonding state and the larger -IpCOHP increase bond strengthen, which result in the smaller thermal expansion coefficient and the higher hardness. Bonding evolution makes thermal expansion coefficient of SnTe reduce by 27%, and Vickers hardness increase by 44%. Higher average power factor, lower thermal expansion coefficient and higher hardness can improve output power density and service life, which provides strategies for exploiting high-power thermoelectric devices with suitable mechanical properties. [ABSTRACT FROM AUTHOR]

The design of metal-supported solid oxide fuel cells (MS-SOFCs) has again aroused interest in recent years due to their low cost of materials, strength, and resistance to thermal cycling, as well as the advantages of manufacturability. MS-SOFCs are promising electrochemical devices for hydrogen energy. Compared to SOFCs, where ceramic electrodes or electrolytes are used as a carrier base, they are of great interest due to their fast start-up capability, greater reliability, mechanical stability, and resistance to the thermal cycle. MS-SOFCs have many advantages over conventional ceramic-based SOFCs, with the selection of metal-based electrode materials (anode, cathode) and their degradation processes being some of the biggest challenges facing researchers. Therefore, this review reports on the state of the latest research on MS-SOFCs with various structures, discusses the corresponding electrode materials and their existing problems, and puts forward topical issues that need to be addressed in MS-SOFCs. [ABSTRACT FROM AUTHOR]

A low leakage rate sealant of 10 wt% ZrO 2 -added CaO–K 2 O–Na 2 O–BaO silicate glass for SOFC has been studied. The structure of the sealant is stable at high temperatures with leakage rates less than 10−4 sccm∙cm−1, and no crystal except for ZrO 2 is found in XRD analysis after heating at 800 °C for 100 h. ZrO 2 is distributed in the glass matrix and plays a supporting role in avoiding over-softening at operating temperature. Good compatibility in both oxidizing and reducing atmospheres between the sealant and SUS430 interconnect was proved by SEM at 750 °C for 100 h. A fully coupled 3D Multiphysics button SOFC is constructed for mechanical analyses. The results show that the increase of ZrO 2 in the sealant will decrease the stress and displacement in the SOFC. Besides, the width of the sealant also affects the stress value and distribution. The results show that GZ10 is a competitive sealing material compared with other ZrO 2 -added sealants. [ABSTRACT FROM AUTHOR]

With the rapid development of modern industry， SiC/Cu composites have great application prospect in electronic packaging due to their excellent conductivity， high strength and thermal conductivity. In this paper， high-volume-fraction β-Sic＠Cu/Cu composites were successfully prepared by electroless plating and powder metallurgy method， and their phase， microstructure and thermal expansion coefficient were characterized by metallographic microscope， XRD and SEM. Results showed that with the increase of SiC volume fraction， the density and flexural strength of β-SiC＠Cu/Cu composites decreased， while the hardness of the composites increased. Moreover， the flexural strength of β-SiC＠Cu/Cu composites was over 70 MPa， the thermal expansion coefficient was 4.5×10-6～10.0×10-6/℃， which met the performance requirements of modern electronic packaging materials.