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

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

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

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]

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]

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]

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]

• A novel geopolymer concrete is developed incorporating waste ceramic aggregates. • The designed geopolymer exhibit ultra-high residual strength after 1000 ℃ thermal exposure. • The high temperature resistance and mechanism of designed geopolymer are investigated. A novel geopolymer concrete is developed, incorporating waste ceramic aggregates, with ultra-high residual strength after exposure to elevated temperatures. Different aggregate volume fractions and particle size gradations are designed, and the variations in mass loss, volume shrinkage, compressive strength, mineral composition, and microstructure of geopolymer mortar after exposure to high temperatures ranging from 20 ℃ to 1000 ℃ are investigated by testing mass loss, volume change, strength, XRD and SEM. The results show that the waste ceramic aggregates (WCA) applied in the preparation of geopolymer mortars improve the mechanical properties and high-temperature resistance. By optimizing aggregate particle size gradation, the microstructure of the geopolymer mortar becomes denser and more homogeneous, and the high-temperature resistance is further improved. The residual compressive strength at 1000 °C is 115.2 MPa, 476 % higher than that of reference. These findings demonstrate the great potential of geopolymer mortars using ceramic aggregates with optimized gradation for high temperature resistant applications. [ABSTRACT FROM AUTHOR]

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

• Shear fracture properties of SCC granite specimens with varying heat treatments are investigated. • The acoustic emission (AE) characteristics are examined. • Fracture surface morphology is investigated by 3D laser scanning. • Attenuation of shear properties of heating-treated granites origin from microstructure degradation. The exploitation of geothermal resources enhances the energy structure but poses challenges related to thermal–mechanical issues. This study utilizes short core in compression (SCC) specimens of granite to investigate thermo-mechanical properties. We examined the effects of heat treatment temperature on physical properties, shear fracture toughness, as well as acoustic emission (AE) characteristics. Fracture surface morphology and microstructure of the heat-treated SCC specimens were also analyzed using 3D laser scanning and scanning electron microscopy. Results indicate that both mass loss and P-wave velocity decrease with increasing heating-treated temperature, and similar trends are observed in mechanical properties. Specifically, fracture energy and shear fracture toughness decline by 51.48 % and 61.27 %, respectively, as temperature rises from 25 °C to 750 °C. The b -value and proportion of shear cracks initially increase before falling, with an inflection point at 300 °C, linked to thermal-induced microstructural deterioration. Fractal dimension (D) and joint roughness coefficient (JRC) show significant increases with higher heat treatment temperatures. Microstructural degradation, including dehydration and thermal-induced microcracking, drives the reduction in shear properties of heat-treated granites. Overall, our findings offer valuable insights into determining various methods of heat storage reconstruction with great application potential. [ABSTRACT FROM AUTHOR]

To maintain the high thermal conductivity (TC) and reduce the coefficient of thermal expansion (CTE) of conventional copper (Cu)/graphite composites, novel Cu/graphite/carbon fibers (CFs) hybrid composites were designed by replacing part of graphite with Cu-coated CFs and prepared by spark plasma sintering (SPS) process. The incorporation of CFs resulted in increased interface density, reduced twin boundaries, and significant grain refinement of the Cu matrix. TEM observations revealed that the Cu-coating on surfaces of CFs enhanced the interfacial bonding between CFs and Cu matrix. The Cu-coated CFs can act as connecting channels between graphite particles, which partially compensate the negative effect on TC. Furthermore, strong interfacial bonding and large Cu/CFs contact areas contribute to the reduction in CTE. As a result, the Cu/30%graphite/10%CFs composite showed TC and CTE of 453.5 Wm−1 K−1 and 10.9 × 10−6 K−1, respectively. Compared to the Cu/40%graphite composite, the CTE of Cu/30%graphite/10%CFs composite was reduced by ∼20 % with only 4.4 % sacrifice in TC. Consequently, the Cu/graphite/CFs hybrid composites showed an excellent balance between TC and CTE, which are superior to the conventional Cu/graphite and Cu/CFs composites. The findings of this work provide new insights for designing and preparing new thermal management materials. [Display omitted] • Novel Cu/graphite/CFs hybrid composites were designed. • Microstructure and thermal properties of the hybrid composites were first reported. • The CFs can act as connecting channels between graphite particles. • Strong and large Cu/Cu-coated CFs contact areas can cause lower CTE. • The hybrid composites showed an excellent balance between TC and CTE. [ABSTRACT FROM AUTHOR]

• An SVR model is built to predict the thermal expansion in Ni-based superalloys. • Several alloys are discovered via GA while the model is as fitness function. • Final alloy has low thermal expansion and superior mechanical properties. Traditional Ni-based superalloys are widely used due to their excellent high-temperature performance; however, their high thermal expansion at elevated temperatures limits their further application in the modern aerospace industry. To discover Ni-based superalloys with low thermal expansion for high-temperature environments, such as 900 °C. In this study, we developed a Support Vector Regression (SVR) model with a high coefficient of determination (R2 = 0.84) to predict the coefficient of thermal expansion (CTE) in Ni-based superalloys. Ten samples were selected and produced from a pool of candidates generated via genetic algorithm and the SVR model, revealing that seven of them exhibited superior CTE performance. Notably, the discovered alloy with the lowest CTE (11.0 e-6 °C-1 from RT to 900 °C) presented a remarkable 16.7 % reduction compared to the best performance in existing database. The finally selected alloy demonstrated both low thermal expansion and superior mechanical properties compared to traditional superalloys with low thermal expansion. [ABSTRACT FROM AUTHOR]

Considering the cyclic variation of temperature and load in the glass molding, the mechanical properties and wear behavior of the nitriding mold steel at high temperatures are necessary to investigate. In this research, the microhardness variation of mold steel after plasma nitriding is elucidated and associated with the microstructure. The high-temperature nanoindentation experiments are conducted to clarify the impact of temperature on mechanical behavior of the nitriding steel. The hardness and elastic modulus of the nitriding steel are decreased by 40.9 % and 19.5 % when the temperature increased from room temperature to 400 °C. Correspondingly, due to the hardness dropping, the wear resistance of the nitriding mold steel decreases gradually with the temperature. However, the wear resistance of the nitriding mold steel under high temperatures is still superior to that of conventional mold steel. A wear schematic model is developed to elucidate the wear behavior evolution mechanism of the nitriding steel with temperatures. This work provides a comprehensive investigation of the mechanical and wear behavior of the nitriding mold steel under high temperatures which avoids mold wear failure in glass compressing molding. • High-temperature mechanical and wear behavior of nitriding mold steel was investigated by experiments. • The wear rate of mold steel after nitriding decreased by more than 92.6 % at RT. • Below 300 °C, the nitriding mold steel possessed excellent wear resistance, but encountered serious wear at 400 °C due to the decrease in mechanical properties by thermal softening. [ABSTRACT FROM AUTHOR]

This study addresses the urgent demand for sustainable building materials, presenting a pioneering use of miscanthus fibers (MF) in metakaolin-based geopolymer paste for thermal insulation. Investigating metakaolin types, alkaline solutions, and curing methods, the study assesses workability, density, compressive strength, thermal properties, porosity, and microstructure. With 30 wt% MF, compressive strength reduces from 19.38 MPa to 6.43 MPa at 28 days, with porosity increasing from 37% to 52%. This heightened porosity, especially in pores >10 μm, lowers thermal conductivity, crucial for insulation. The geopolymer matrix without MF exhibits a thermal conductivity of 0.45 W.m−1.K−1, serving as a reference. A 50 wt% MF formulation achieves the lowest thermal conductivity (0.21 W.m−1.K−1) and 5 MPa compressive strength. Aligning with plastering, rendering, and masonry mortar standards, using Argical 1000 metakaolin enhances compressive strength by 57% compared to the reference sample made with Argicem metakaolin. Analytical Scanning Electron Microscopy reveals robust fiber-matrix adhesion, ensuring structural integrity. • Lowest thermal conductivity achieved for 50 wt% fibers, Argical 1000, Na solution. • Highest compression strength achieved with low MF, Argical, K solution. • The rate of macro pores (>10 μm) increases with the amount of fibers added. • 50 wt% MF gave 0.21 W.m−1.K−1 thermal conductivity and 5 MPa compressive strength. [ABSTRACT FROM AUTHOR]

The aging Al–Zn–Mg–Cu alloy exhibits a significant decrease in performance after undergoing thermal shock. In order to improve the resistance of this type of alloy to thermal shocks, the influence of deep cryogenic treatment (DCT) on the high temperature mechanical properties and microstructure of thermal shocked Al–Zn–Mg–Cu alloy is investigated in this paper. It was found that the mechanical properties of Al–Zn–Mg–Cu alloys decrease significantly with the increase of electric heating temperature. The deep cryogenic treatment reduced the grain size of Al–Zn–Mg–Cu alloy, increased the density of the precipitates, and also inhibited the coarsening of the precipitates. Therefore, the deep cryogenic treatment can slow down the weakening effect of Al–Zn–Mg–Cu alloy at high temperatures. [ABSTRACT FROM AUTHOR]

The present work focuses on the role of NiB and ZrB 2 addition on density, structural evolution, mechanical and thermal properties of 90W-6Ni-4Co (wt%) heavy alloys. The investigated tungsten heavy alloys were sintered at 1485 °C and 1500 °C with a holding time of 75 min in H 2 atmosphere. Compared to the base alloy 90W-6Ni-4Co, the NiB-substituted alloys showed improved densification at both sintering temperatures. An in-depth study of the phase and microstructure of the 1500 °C sintered samples was carried out. X-ray diffraction analysis confirmed the presence of ZrO 2 in ZrB 2 containing WHAs. Microstructural analysis affirms that ZrB 2 incorporation attributes for grain size refinement in sintered alloys. Furthermore, the elephant foot formation in the sintered samples was avoided by incorporating NiB individually or in combination with ZrB 2 dispersoids. The distortion parameter (δ) of the samples sintered at 1500 °C was found to be decreased from 24.83 (0 wt% ZrB 2) to 6.36 (2 wt% ZrB 2). On the other hand, the combined addition of NiB and ZrB 2 provides better shape retention with δ =2.82 for the tungsten heavy alloys with 3 wt% NiB and 2 wt% ZrB 2. The maximum compressive stress of ∼2000 MPa was obtained in the 89W-6Ni-4Co-1ZrB 2 samples. The maximum and minimum bulk hardness of 432 ± 5 HV 3 and 365 ± 9 HV 3 was obtained for 88W-3Ni-3NiB-4Co-2ZrB 2 and 90W-6Ni-4Co heavy alloys. The coefficient of thermal expansion of the 90W-6Ni-4Co alloy was found to be the highest (7.65 × 10−6 /°C), which was reduced to 7.1 × 10−6 /°C and 6.8 × 10−6 /°C with the incorporation of 1 and 2 wt% ZrB 2 respectively. W-rich channels were noticed in the microstructure of 1500 °C sintered samples. Overall, W-Ni/NiB-Co-ZrB 2 alloys are very effective in enhancing the mechanical properties and distortion behavior compared to W-Ni-Co alloys. • ZrB 2 addition refines W grain size in sintered alloys. • XRD and EDS analysis confirm the partial transformation of ZrB 2 to ZrO 2. • A distinct channel like structure was noticed in NiB-substituted sample. • The liquid phase sintered W-Ni/NiB-Co-ZrB 2 alloys prevent shape distortion. • ZrB 2 -containing heavy alloys offer reduced thermal expansion coefficient. [ABSTRACT FROM AUTHOR]

• Lesser mealworm protein gel (LMPG): a potential vitamin B 12 encapsulant. • Improved LMPG by a synergy of transglutaminase (TGase) and ultrasound (US) • Enhanced thermal stability and gelling in TGase-induced LMPG after 60 min-US. • A high controlled release rate of cobalamin under in vitro simulated digestion. • Developing new gluten-free bread products with vitamin B 12 -loaded gel powders. A combined approach of microbial transglutaminase (MTGase) crosslinking and high-intensity ultrasound (HIU) was implemented to improve the physicochemical, rheological, structural, and thermal properties, as well as the targeted release of vitamin B 12 of lesser mealworm protein isolate (LMPI)-based gels. Prolonging HIU to 60 min significantly reduced LMPIs' size, polydispersity, zeta-potential, and fluorescence intensity while increasing surface hydrophobicity, free amino (FAGs), and sulfhydryl (FSGs) groups. The MTGase-catalyzed LMPI gels effectively decreased the content of FAGs and FSGs. LMPI gels from 60 and 75 min HIU and MTGase catalysis exhibited a shear-thinning flow behavior, superior thermal stability, and improved water retention and gel strength with the most controlled release of vitamin B 12 during in vitro simulated gastrointestinal digestion. Incorporating freeze-dried gel powders from 60 min HIU-treated MTGase-catalyzed LMPI and pea protein isolate into the dough of a new gluten-free bread improved physicochemical, textural, and sensory properties, with notable vitamin B 12 retention rate. [ABSTRACT FROM AUTHOR]

Resin-reinforced Ag sintering materials represent a promising solution for die-attach applications in high-power devices requiring enhanced reliability and heat dissipation. However, the presence of resin and intricate microstructure poses challenges to its thermal performance, and improvement strategies remain unclear. This work utilizes 3D FIB-SEM nanotomography to reconstruct the microstructure of this material under various process conditions. The analysis reveals that, even with an Ag volume fraction as low as 47.3%, Ag particles form a robust 3D network. Geometric tortuosity quantifies the effect of different sintering conditions on the Ag particle network in all spatial directions. Effective thermal conductivity is simulated based on realistic microstructure models. Results show a significant negative correlation between tortuosity and effective thermal conductivity. Increasing sintering temperature in Model B notably reduces tortuosity and enhances effective thermal conductivity. Sensitivity analysis underscores the dominant role of Ag volume fraction in regulating effective thermal conductivity. Finally, transient thermal impedance measurement of this material as a thin die-attach layer in actual high-power devices demonstrated its application potential. This article strives to explore the relationship between process, microstructure, and thermal properties of this material to provide a reference for further development. • 3D FIB-SEM nanotomography meticulously reconstructed and distinguished the microstructure under different process conditions. • Effective thermal conductivity is simulated from a realistic microstructure model using a high-performance cluster. • Tortuosities intuitively reflects the influence of process conditions on the microstructure and thermal properties. • Sensitivity analysis shows the dominant role of Ag volume fraction on the effective thermal conductivity. [ABSTRACT FROM AUTHOR]

The development of lightweight shape memory materials with exceptional thermal insulation properties is highly important in aerospace applications. Herein, shape memory polyimide (PI) aerogels was fabricated by molecularly designed PI molecular chains through freeze gelation and subsequent thermal imidization. The freezing conditions were controlled to regulate the porous microstructures of the aerogels. The interactions between PI chains formed physically crosslinked netpoints, which could overcome the expansive force and capillary force, thereby creating a stable porous structure. Because shape memory was thermally activated, the shape memory mechanisms associated with the thermal conductivity of the aerogels were comprehensively explored. Upon decreasing the pore size, dense frameworks were formed, contributing to the improved thermo-mechanical and compressive properties. Moreover, the heat transfer efficiency in the aerogel skeleton was enhanced, resulting in a rapid shape recovery response. Benefiting from the physically crosslinked structures, including entangled chains and π-π interactions, the fabricated PI aerogels demonstrated exceptional shape fixation and recovery capabilities. These findings may provide guidelines for designing smart aerogels for aerospace applications. [Display omitted] • Shape memory polyimide aerogels with tunable porous microstructures were fabricated. • The size of the micropores was regulated by controlling the freezing conditions. • The reduction of pore size accelerated the shape recovery process. • The comprehensive exploration of the shape memory mechanisms was conducted. [ABSTRACT FROM AUTHOR]

Utilizing element substitution to enhance the hydrogen storage capabilities of Mg-based alloys represents a promising approach in the quest for efficient energy storage solutions. Thereby, in this paper, Ni is chosen to substitute a portion of Mg in a Ce–Mg-based alloy aimed at improving its hydriding and dehydriding performance. Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys are successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys are performed using X-ray diffraction and scanning electron microscope. The alloys are composed of a primary phase of Mg 2 Ni, lamella eutectic composites of Mg + Mg 2 Ni, and some amount of CeMg 12 and Ce 2 Mg 17. In the as-cast Mg 87 Ni 10 Ce 3 alloy, the Mg 2 Ni phase disappears, transforming into a typical eutectic structure of hundreds of nanometers thick Mg–Mg 2 Ni lamellas. This structure significantly enhances the hydrogen storage kinetics, with a hydrogen absorption capacity of 5.66 wt% at 653 K and a desorption capacity of 5.45 wt% over 2 h at 683 K, outperforming other alloys. Moreover, its peak hydrogen release temperature is significantly lower than that of the Mg 92 Ni 5 Ce 3 alloy. The formation of the CeH 2.29 phase within the alloy acts as a catalyst, effectively improving the exothermic and endothermic kinetics of hydrogen absorption and desorption, resulting in a much lower hydrogen desorption activation energy compared to MgH 2. However, the variation in the activation energy of the alloy remains limited, ranging between 66.6 ∼71.1 kJ/mol. [Display omitted] • Mg 77+ x Ni 20- x Ce 3 (x = 0, 5, 10, 15) alloys were prepared in an induction furnace. • Ni substituting for Mg significantly lowers the peak temperature of hydrogen release. • Ni substituting for Mg reduces the desorption activation energy values. • The Mg 87 Ni 10 Ce 3 alloy can absorb more than 5.66 wt % H 2 within 120 min at 653K. [ABSTRACT FROM AUTHOR]

• Novel method is applied to fabricate SiC fiber-reinforced Al matrix composites. • SiC fibers with high volume fraction is introduced into the Al matrix uniformly. • SiC fiber significantly improve the mechanical properties of Al matrix composites. • Coefficient of thermal expansion decreases with increasing the SiC fibers' content. Combining the colloidal dispersion method with the squeeze melt infiltration technique, aluminum matrix composites with different volume fractions of silicon carbide fiber were fabricated at 680 °C under vacuum. Microstructure analysis found that composite presented a dense structure and fibers were homogeneously distributed in matrix. The hardness, yield strength and elastic modulus of the composite monotonically increased with increasing the volume fraction of fiber. The highest flexural strength for composite with 10 vol% SiC fiber was achieved. The improved mechanical properties could be attributed to the dispersion strengthening and enhanced load transferring ability by fibers as well as the dislocation strengthening. On the other hand, the coefficient of thermal expansion of composites was measured at temperature up to 400 °C. It was found that the uniform introduction of silicon carbide fiber could significantly low the CTE of aluminum matrix composite, which could be attributed to the low CTE of SiC fiber and good fiber–matrix interface bonding. [ABSTRACT FROM AUTHOR]

The study showed that transglutaminase (TG) significantly affected the thermal properties and retrogradation of wheat flour (WF). Confocal laser scanning microscopy showed that the samples treated with TG had an increased number of starch granules embedded in protein fragments compared with the control sample. Thermal properties were altered, and the swelling power of the samples decreased with increasing enzyme concentration. A change in pasting properties, especially a decrease in the final and setback viscosities, was also observed after adding TG. TG delayed the retrogradation process, with inhibitory effects attained at an enzyme concentration of approximately 0.05%. The inhibitory effects of TG on the retrogradation of WF were mainly hypothesized to be caused by alterations in the water absorption of the starch granules from the effect of TG on the surface. [Display omitted] • TG inhibited the retrogradation of wheat starch. • TG had major impacts on thermal properties and reduced swelling power of WF. • Microstructure revealed the change in protein and starch distribution in WF. [ABSTRACT FROM AUTHOR]

This study examined the impacts of milled starch particles at 14 μm (MS1), 9 μm (MS2), 265 nm (NS1) and 130 nm (NS2) on fish myofibrillar proteins (MP) undergoing multiple freeze-thawing by analyzing changes in texture, microstructure and thermal property of MP gels. SEM and light microscopy observation showed that multiple freeze-thawing caused not only the deterioration of gel structure but also the tight bunching of MP strands. As freeze-thaw cycles increased, the hardness and adhesiveness decreased, while drip loss and free water content increased, attributed to the deterioration of gel structure. The cohesiveness, breaking force, and deformation initially decreased and then recovered, as these parameters were mainly controlled by the bunching of MP strands via disulfide bond between protein macromolecules. All experimental analyses confirmed that micro- and nano-sized starch could alleviate the quality deterioration of MP gels. Notably, NS2 exhibited the most favorable performance in inhibiting texture deterioration of the freeze-thawed MP gels, thanks to its exceptional active filling effect and the much more disulfide bonds generated in MP. MS1 was the most effective in reducing drip loss of MP gel, due to the transformation of free water into bound water in MP/MS1 gel. Additionally, MS and NS, especially MS1, remarkably enhanced the freezing stability of MP as evidenced by a significantly increased T g (−55.85 °C to −39.51 °C) of MP and a shortened temperature region for maximal-ice-formation (−55.85∼−30.92 °C to −39.51∼−27.65 °C). Overall, combined utilization of MS1 and NS2 can maintain the optimal quality of fish gel products during frozen storage. [Display omitted] • Freeze-thawing causes MP gel structure deterioration and MP strands bunching. • Cohesiveness and breaking force decrease and then recover with freeze-thaw cycles. • Micro- and nano-starch (MS&NS) reduce quality deterioration of freeze-thawed gels. • NS2 (130 nm) shows the best performance on texture and MS1 (14 μm) on drip loss. • MS1 has a greater effect on enhancing MP freezing stability than MS2 and NS2. [ABSTRACT FROM AUTHOR]

In this study, the influences of thermal exposure on the microstructure and creep resistance of matrix alloy and (TiB+TiC+Y 2 O 3)/α-Ti composites were systematically studied. The results indicate that long-term thermal exposure leads to β-Ti dissolution, as well as the precipitation of a large number of S1 type silicides and α 2 particles. The high temperature and internal stress by thermal exposure promote β-Ti→α-Ti phase transition. In order to reduce the total energy, nanoscale {10 1 ̅ 1} transformation twins were formed at the α/β interfaces. The introduction of precipitates and nano twins leads to a significant improvement in the creep resistance after thermal exposure. The creep life can be increased by up to 108 %, while the steady-state creep rate can be reduced by an order of magnitude. After creep, there was no significant increase in the size of precipitated silicides and α 2 particles. The rod-shaped S1 type silicide has a better pinning strengthening effect on dislocations than spherical S2 type silicide. Nano twins improve the stability of the α/β interfaces during creep. Some twins were coarsened after creep by merging mechanism. Twins and reinforcements provide nucleation sites for sub-grains during the creep process. • The characteristics of α 2 phases, silicides and nano twins after thermal exposure were investigated. • The reasons for the enhanced creep properties by thermal exposure were analyzed. • The response of silicides and nano twins to creep deformation were analyzed by TEM and HRTEM. • Dynamic recrystallization behavior based on DDRX and CDRX process were discussed. [ABSTRACT FROM AUTHOR]

To improve the thermal gel properties of egg yolk, the effect of several valence metal ions (K+, Ca2+, Mg2+ and Fe3+) with different concentrations (0–0.72%) on the rheological, gel, and structural properties of egg yolk were investigated. Results showed that monovalent and divalent ions were beneficial to the formation of uniform and dense gel network, especially with the addition of 0.72% magnesium ion, which further improved gel hardness, water holding capacity (WHC) and viscoelastic properties, the properties of egg yolk gel increased with the increase of the concentration of mono-bivalent metal ions. Adding ferric ion remarkably increased the average particle size (d 4,3) and apparent viscosity of egg yolk, destroying the disulfide bonds and the hydrophobic interactions in gel. Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectra analysis revealed that metal ions promoted the hydrophobic aggregation among egg yolk proteins and induced the transition of protein secondary structure from ordered to disordered. This work will provide a theoretical reference for the development of low salt and nutrient fortified egg yolk products. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the microstructure, mechanical properties, and thermal conductivity of as-extruded Mg–4Zn-0.6Zr-xCa (x = 0, 0.3, 0.6, 0.9 wt%) alloys were investigated. The results revealed a bimodal grain size distribution in all the alloys due to incomplete dynamic recrystallization (DRX), characterized by the coexistence of elongated deformed grains and equiaxed DRX grains. The bimodal grain size distribution enhanced the mechanical properties of the studied alloys. Furthermore, Ca alloying facilitated the formation of Ca 2 Mg 6 Zn 3 phases, through which the DRX extent was also enhanced. The precipitation of secondary phases, along with the increased DRX induced by Ca addition, was beneficial in eliminating the lattice distortion of the alloys, resulting in improved thermal conductivity compared to the Ca-free Mg–4Zn-0.6Zr alloy. The optimum combination of mechanical properties and thermal conductivity was achieved in the Mg–4Zn-0.6Zr-0.6Ca alloy, with yielding strength, ultimate tensile strength, tensile fracture elongation, and thermal conductivity values of 271 MPa, 318 MPa, 17.6 %, and 123.9 W/(m‧K), respectively. This work demonstrates that Mg–Zn–Zr–Ca-based alloys can be developed with high strength and high thermal conductivity, significantly expanding the industrial application of magnesium alloys. [ABSTRACT FROM AUTHOR]

Tuning the microstructure of composite energetic materials is an effective way to improve charging, safety, and combustion performance. In this paper, boron (B)/barium chromate (BaCrO 4) composite particles with controllable microstructure were prepared using droplet microfluidic technology (DMT). Based on the theory of droplet template self-assembly, composite particles with controllable morphology, size, and composition were prepared, revealing the regulation mechanism of the particle microstructure. The composite particles prepared using DMT exhibit a uniform distribution of characteristic elements, high circularity, smooth surface, enhanced bulk density, and excellent flow properties. The thermal decomposition characteristics, safety, and combustion properties of the samples were investigated by thermal weight loss, mechanical sensitivity, and combustion tests. Thermal weight loss and mechanical sensitivity tests showed that the samples had stable thermal decomposition properties and significantly increased mechanical stability compared to the control. The combustion test results showed that the DMT-prepared samples had a short ignition response time and significantly improved delay precision. This paper presents a straightforward method for preparing B/BaCrO 4 particles with high delay accuracy, which can serve as a reference for preparing other composites. [Display omitted] [ABSTRACT FROM AUTHOR]

• Cu/Fe/Kovar composites have a much better thermal conductivity than Kovar alloys. • Good thermal conductivity of Cu/Fe/Kovar composites is attributed to the formation of Cu network. • Fe interlayer decreases the mutual diffusion between Cu coating and Kovar alloy matrix. To improve the thermal conductivities of Kovar alloys (4J50), Fe and Cu coatings were prepared on surfaces of one of Kovar alloys (4J50) powders by electroless plating and Cu/Fe/Kovar composites were hot-pressing sintered. The Fe interlayer is prepared to decrease the mutual diffusion between the Cu coating and the Kovar alloy matrix. Since the existence of Cu network in the composites, the composites present a better thermal conductivity than Kovar alloys. The Cu/Fe/Kovar composites containing 10 wt% and 20 wt% Cu have a thermal conductivity of 24.7 W/(m·K) and 25.8 W/(m·K), respectively, which is 48 % and 54 % higher than that of the Kovar alloy (16.7 W/(m·K)). Due to the presence of Cu network, the coefficients of thermal expansion of the composites is slightly higher than that of the Kovar alloy. The method reported in this study can be also applied to improve the thermal conductively of other Kovar alloys. [ABSTRACT FROM AUTHOR]

For carbon reinforced metal matrix composites (MMCs), achieving both superior thermal conductivity (TC) and excellent thermal cycling stability has remained challenging owing to the poor interfacial bonding between carbon and metal matrix. Here, we reported an ultrasonic assisted electrodeposition and electrophoresis composite processing to fabricate Cu/GO/Cu laminated composites with Ag intermediate layer to improve the interfacial bonding and its TC. A superior in-plane TC of the Cu/Ag/GO/Ag/Cu composite (563.6 W·m−1·K−1) prepared under 0.05 mol/L Ag+ concentration was achieved, which was increased by approximately 41.5% and 15.9%, comparing to pure Cu (398.2 W·m−1·K−1) and Cu/GO/Cu composite (483.6 W·m−1·K−1). Simultaneously, the influence of thermal cycling on TC and residual stress were investigated in a temperature range of −196 ∼ +200 °C. The in-plane TC of Cu/Ag/GO/Ag/Cu composite was still as high as 498.5 W·m−1·K−1 after thermal cycling treatment for 30 times. The mechanism of high thermal properties was investigated by molecular dynamics simulation. The increased lattice thermal conductivity and interfacial bonding were responsible for it. It is expected that our work could provide an alternative method for fabricating MMCs with high TC and thermal cycling stability. [Display omitted] • The Cu/Ag/GO/Ag/Cu laminated composites were fabricated by ultrasonic assisted electrodeposition and electrophoretic method. • The addition of the Ag intermediate layer effectively improved its thermal conductivity. • The influence of thermal cycling on the thermal conductivity and residual stress of the composites was investigated. [ABSTRACT FROM AUTHOR]

• Under the synergistic effect of the chain extender ADR and the flexible phase PBSG, the impact strength of the PLA/PBAT blend (ATR-P8) reached a maximum value of 56.51 kJ/m2. • The annealing treatment improved the heat-resistant of the PLA blends significantly, which could keep 12 h at 100 °C under 20 g loading with little deformation. Super toughened and high heat-resistant poly (lactic acid) (PLA)/poly (butylene-adipate-co-terephthalate) (PBAT) blends were synergistically prepared by compounding pre-prepared polyborosiloxane gel (PBSG) and multicomponent epoxy chain extender (ADR) with further heat-treatment. The effects of PBSG content on the performance and microstructure of the blends were investigated. The impact strength of the blends without heat treatment increased with the increase of PBSG content. After heat treatment, the impact strength of the blends showed a tendency of first increasing and then decreasing with the increase of PBSG content, and the maximum impact strength of the blends before and after the heat treatment was 56.51 kJ/m2 and 46.08 kJ/m2, respectively. The heat treatment could greatly improve the vicat soft temperature and thermo-mechanical properties of the blends. After the heat treatment, the vicat soft temperature of all the blends exceeded 150 °C, and the storage modulus of all the blends exceeded 100 MPa, and the annealed PLA blend beard a 20 g weight could kept at 100 °C for 12 h with negligible deformation, which attributed to the improvement of the interface properties and the crystallization properties. [ABSTRACT FROM AUTHOR]

Effects of agar on the rheological property and heat stability of casein micelle gels induced by rennet were investigated. The interactions between casein micelle and agar were investigated. Electrostatic interactions between casein micelle and agar were not observed. The movement of agar characteristic bonds indicated the hydrogen bond interaction existed in the casein micelle/agar mixture. The addition of agar promoted the casein micelles aggregation and decreased the rennet coagulation time (RCT) and the storage modulus (G'). The strip-like network microstructure changed into a sheet-like network after the addition of agar. The composite gels were present as a bicontinuous phase structure. The agar and protein were both present as continuous phases. The addition of 0.5% agar increased the water holding capacity (WHC) from 63.30% to 92.44% and decreased the gel hardness from 73.41 g to 60.57 g. The protein digestion rate of gels increased after agar addition during gastric digestion. The WHC increased from 35.20% to 83.56% and the microstructure of gels improved by the addition of 0.5% agar after heating at 80 °C for 30 min. In conclusion, the WHC and thermal stability of the gels improved after the addition of agar. [Display omitted] ● The hydrogen bond interaction existed in the casein micelle/agar mixture. ● The addition of agar decreased the rennet coagulation time and the storage modulus. ● The composite gels had a bicontinuous phase structure. ● The addition of agar improved the thermal stability of the gels. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are a group of natural polyesters that are synthesised by microorganisms. In general, their thermoplasticity and (in some forms) their elasticity makes them attractive alternatives to petrochemical-derived polymers. However, the high crystallinity of some PHAs – such as poly(3-hydroxybutyrate) (P3HB) – results in brittleness and a narrow processing window for applications such as packaging. The production of copolymeric PHA materials is one approach to improving the mechanical and thermal properties of PHAs. Another solution is the manufacture of PHA-based block copolymers. The incorporation of different polymer and copolymer blocks coupled to PHA, and the resulting tailorable microstructure of these block copolymers, can result in a step-change improvement in PHA-based material properties. A range of production strategies for PHA-based block copolymers has been reported in the literature, including biological production and chemical synthesis. Biological production is typically less controllable, with products of a broad molecular weight and compositional distribution, unless finely controlled using genetically modified organisms. By contrast, chemical synthesis delivers relatively controllable block structures and narrowly defined compositions. This paper reviews current knowledge in the areas of the production and properties of PHA-based block copolymers, and highlights knowledge gaps and future potential areas of research. [ABSTRACT FROM AUTHOR]

Invar 36 alloy manufactured via the laser powder bed fusion (LPBF) process have attracted interest for their excellent low expansion properties. The properties of Invar 36 alloy, particularly thermal expansion, are highly sensitive to variations in process parameters. However, the effect of process parameters on microstructure and properties has not been systematically studied. This study examines the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of Invar 36 alloy under various processing parameters with different volumetric energy densities (VED). The results demonstrate that VED variations significantly impact the microstructure, mechanical properties, and CTE. Increasing VED leads to larger grain size and higher high angle grain boundaries, while geometric dislocation density and Taylor factor do not exhibit a linear relationship. At 89.29 J/mm3 VED, the Invar 36 alloy displays the optimal yield strength (405.4 MPa), tensile strength (489.3 MPa), and elongation (43.3%). The CTE meets the ASTM F1684 standard for all specimens. Lower relative density corresponds to smaller CTE, with the lowest CTE achieved at VED of 41.67 J/mm3. Furthermore, the influence of porosity on CTE diminishes with rising temperature. This research opens up the possibility of process parameters optimization for improved CTE and mechanical properties in as-printed Invar parts. [ABSTRACT FROM AUTHOR]

Monolithic polymer-derived SiC is highly desirable for high temperature applications because of its unique thermal properties in extreme conditions. The current study focuses on the formation, evolution, and stability of polymer-derived SiC at different high temperatures. SiC-based monoliths were pre-pyrolyzed at 1200 °C and then pyrolyzed at 1600 - 2500 °C in a flowing argon atmosphere. The porosity, density, compositions, and phases of the SiC samples were studied. Dense SiC monolith was obtained from 1200 °C to 2200 °C. SiC crystallized at 1900 °C and formed a near stoichiometric composition. β-SiC remained stable even at 2200 °C. However, the SiC monolith experienced continuous mass loss above 1900 °C and disintegrated at 2500 °C with ∼89.5% mass loss. This work opens a pathway for preparing near stoichiometric and dense SiC monoliths through polymer precursor pyrolysis; it also provides fundamental understanding of polymer-derived SiC at different high temperatures. • Dense SiC monolith was prepared by crosslinking and pyrolysis of SMP-10 precursor. • SiC formed at 1900 °C was near stoichiometric. • Pyrolysis at 2200 °C initiated the sublimation of 'Si' and led to excessive carbon. • Pyrolysis at 2500 °C led to disintegration of SiC and a porous graphitic structure. • The work offers a complete map of polymer-derived SiC formation and decomposition. [ABSTRACT FROM AUTHOR]

As an environmentally friendly material, alkali-activated fly ash-slag (AAFS) is considered as a promising alternative cement because of its excellent mechanical properties and thermal stability. Nevertheless, high temperature induced damage in AAFS can potentially bring serious risks for its practical applications. This paper presents a systematic experimental study on behaviour of AAFS paste subjected to elevated temperatures up to 800 °C in terms of microstructure as well as thermal and mechanical properties. Microstructural evolution was characterised by means of Rietveld-based quantitative X-ray diffraction (QXRD), backscattered scanning electron microscope (BSEM) and X-ray microcomputed tomography (XCT), while thermal and mechanical properties were evaluated from thermogravimetric analysis (TGA), thermal deformation and compressive and flexural strengths. Results indicate that the compressive strength of AAFS paste rises by 77.5 % at 200 °C, followed by a mitigation from 200 to 600 °C and a regain at 800 °C. Different phases in AAFS paste including unreacted particles, reaction products and pores took up 30 %, 67.7 % and 2.31 % at ambient temperature, and 4.95 %, 84.8 % and 10.3 % after exposure to 800 °C, respectively, suggesting the recrystallisation with the formation of nepheline and gehlenite. In addition, the relationships between microstructural characteristics including three-dimensional (3D) pore structure features and thermal and mechanical properties of AAFS paste at elevated temperatures were explored and discussed in depth to gain insights into the underlying degradation mechanisms including pore pressure build-up, thermal gradient and phase transformation. [ABSTRACT FROM AUTHOR]

A detailed evaluation of alkali-activated fly ash-slag's (AAFS) mechanical and microscopic behavior characteristics under thermal cycling is crucial for its application in complex high-temperature environments. This study investigated the performance evolution and mechanism of AAFS materials under 60 ℃ thermal cycling from the aspects of quality, compressive strength, drying shrinkage, hydration products, and microstructure. It has the highest compressive strength at 60 thermal cycling, and the compressive strength will rebound and rise after 300 thermal cycling. The formation, decomposition, or restructuring of the gel phase of hydration products causes changes in internal pore characteristics, and the number and width of microcracks, thereby affecting macroscopic performance changes. It is found that in the complex high-temperature environment, the fly ash-slag mass ratio in the alkali-activated system should be 1:1, the most suitable alkali activator module is about 1.0, and the Na 2 O concentration is 4%⁓6%. • The highest compressive strength at 60 thermal cycling. • When the thermal cycling times reach 300, the compressive strength rebound increases. • In a complex high-temperature environment, the alkali-activated raw materials are not suitable for pure fly ash and slag systems. • The C-(A)-S-H gel phase is unstable under long-term cycling at 60 °C. • The fly ash-slag mass ratio in the alkali-activated system should be 1:1, the most suitable alkali activator module is about 1.0, and the Na 2 O concentration is 4%⁓6%. [ABSTRACT FROM AUTHOR]

Seashells accumulate rapidly, particularly in coastal areas and in countries that consume a lot of seafood. In order to be recycled and used in ordinary building materials, we have carried out a study into the feasibility of using the seashells in plaster as a substitute and additive. Two cases of incorporation were carried out, the first involving the substitution of plaster by seashell powder in percentages (4%, 8%, 12%, 16% and 20% by mass), the second consisting of the use of the powder as an additive in percentages (2%, 4%, 6%, 8% and 10%). The compressive and flexural strength values are close to those of the control gypsum. However, the use of powder as a substitute can improve the thermal insulation and durability of the gypsum composite. [ABSTRACT FROM AUTHOR]

To address the challenges associated with significant thermal disturbance and carbon emissions resulting from the conventional stabilization of frozen soil using cement, geopolymer material is used to replace cement to stabilize frozen soil. The unconfined compressive strength (UCS) of the geopolymer stabilized soil was investigated in relation to the proportions of metakaolin (MK), calcium carbide slag (CCS), curing temperature, and curing age. Microscopic analysis was conducted to unveil the stabilized mechanism. The UCS, shear strength, thermal conductivity, hydration products and microstructure of geopolymer stabilized soil and cement soil were compared in parallel. A total of 240 experiments were conducted in this study. The outcomes indicate that the optimal content of MK and CCS is 10% and 6% respectively. The UCS of samples with the optimal content after 28d of curing at 20 °C, −2 °C, and − 10 °C are 3.783 MPa, 1.164 MPa, and 0.901 MPa respectively. The primary causes of the rise in UCS of the geopolymer stabilized soil are the production of amorphous calcium silicate hydrate and calcium aluminate hydrate gel as a result of the stimulation of MK based geopolymer with CCS. The UCS of the geopolymer stabilized soil decreases with a decrease in curing temperature. In frozen conditions, the expansion of ice crystals in the soil creates voids and promotes crack growth, leading to a decrease in the efficiency of geopolymerization reactions. After 28d of curing at room temperature and low temperature, the geopolymer stabilized soil with the optimal content exhibits higher UCS, failure strain, shear strength, cohesion, and internal friction angle compared to the cement soil. At all curing temperatures and ages, the geopolymer stabilized soil has a lower thermal conductivity than the cement soil. The geopolymer stabilized soil is less susceptible to low temperature curing than cement soil, demonstrating a larger amount of hydration products and a denser microstructure, according to experimental results from XRD and SEM. The results of this work offer a theoretical foundation for using geopolymer in place of cement to stabilize soils in permafrost regions. • The optimal mixing content of geopolymer stabilized soil during low temperature curing was investigated. • The curing temperatures and curing ages have positive effects on the compressive strength of geopolymer stabilized soil. • The mechanical and thermal properties of geopolymer stabilized soil and cement soil were compared in parallel. • The low curing temperatures significantly inhibit the hydration products. [ABSTRACT FROM AUTHOR]

• 500 °C serves as the threshold for altering the spatial arrangement of limestone. • 500 °C accelerates thermal motion, leading to stratification of rock walls. • Following heat treatment, the microscopic structure displays a 'thousand-layer' pattern. • The thermal conductivity and heat storage coefficient decrease by about 3 % per 100 °C. This article combines X-ray diffraction (XRD) analysis of limestone after high-temperature treatment with microscopic structural characteristics. It aims to elucidate the changes in diffraction peak characteristics from a microscopic perspective and investigate the thermodynamic property variations of the material. The research findings indicate that 500 °C is the threshold temperature at which limestone's crystalline orientation and spatial arrangement change, resulting in a decrease in peak height in the diffraction pattern. Additionally, temperatures ranging from 500 to 600 °C accelerate particle thermal motion, leading to the detachment of rock layers, the inward extension of fissures, and the formation of a sedimentary rock-like 'layered' stacking structure. The thermal conductivity, specific heat capacity, and heat storage coefficient of limestone gradually decrease after thermal treatment, with a reduction rate of approximately 3 % per 100 °C. The microstructural characteristics and thermodynamic property changes of high-temperature limestone reveal the impact of high-temperature damage on limestone structure and thermodynamic properties, facilitating the advancement of limestone material applications and damage control under high-temperature conditions. [ABSTRACT FROM AUTHOR]

In this work, Zr 50 Cu 42 Al 8 alloy was rapidly quenched into as-cast rod with nano-glass microstructure and fully amorphous as-spun ribbon, respectively. The different microstructure between the as-cast rod and as-spun ribbon results in the different glass transition, crystallization temperatures and their kinetics. The continuous heating transition (CHT) curves of the as-cast rod and as-spun ribbon derived from their heating rate dependence of onset crystallization temperature imply that the partial nano-crystallization stabilizes the amorphous remainders in the Zr 50 Cu 42 Al 8 rod when annealed below ∼ 757 K, and give rise to the possibility to obtain nano-crystallization by annealing the fully amorphous ribbons within the temperature interval between the two CHT curves. It is as expected that the ribbons annealed at 730 K for 678 s and at 720 K for 3644 s, respectively show similar microstructure and thermal properties to the as-cast rod. The results provide a valid way to achieve tailorable nano-crystallization in the fully amorphous alloys. [ABSTRACT FROM AUTHOR]

Needle-punched fabric reinforced nanoporous phenolic composite (NPC) is a kind of promising ablative thermal protection material for spaceflight. However, in practical applications, typically anisotropic microstructure of NPC may lead to different performances and damage mechanisms under various directional mechanical or thermal loads. Herein, NPC is prepared and cut into specimens along three typical plane directions including XY -plane (0°), Z -plane (90°), and transitional-plane (45°), and their mechanical, thermal insulation, and ablation behaviors are systematically investigated. Benefiting from the woven fabric in XY -plane, NPC in 0°-plane direction exhibits highest tensile strength (169.2 ± 12.6 MPa), and CT image-based simulation further verifies that woven fabrics are primary load-bearing structure. Meanwhile, NPC in 45°-plane direction shows highest compressive strength (443.1 ± 18.2 MPa) but low compressive stress at low strain, demonstrating a weak bonding between two layers of woven fabrics. Moreover, the heat transfer simulation indicates that horizontally stacked woven fabrics effectively protect the internal material from thermal erosion, thus NPC in 0°-plane direction exhibits optimal thermal insulation. The ablation testing and micro-CT observations further demonstrate that the angle between woven fabric and thermal load significantly influences the ablation mechanism. The present work will further promote the structural reliability and optimization of needle-punched composites. [Display omitted] [ABSTRACT FROM AUTHOR]

To pursue superior yield strength and low thermal expansion characteristic of Fe-36Ni Invar alloy, Fe-36Ni Invar alloys containing various cerium (Ce) contents (0 wt%, 0.0050 wt%, 0.0170 wt%, and 0.0360 wt%) were prepared by vacuum induction melting, followed by the heat treatment process. With increasing Ce content, the evolution of the second-phase particles followed the sequence: MnO-MnS (0% Ce) → MnO-MnS + Ce 2 O 3 (0.0050% Ce) → Ce 2 O 3 + Ce 2 O 2 S (0.0170% Ce) → Ce 2 O 3 + Ce 2 O 2 S + Ni 5 Ce (0.0360% Ce). The results indicated that the grain size and the fraction of annealing twins (f AT) were fairly sensitive to the Ce content. The smallest average grain size (d ¯) and the highest f AT were obtained by adding 0.0170% Ce. The small addition of Ce was beneficial to the improvement of strength and low thermal expansion behavior. In particular, 0.0170% Ce alloy achieved the optimal combination properties. However, the excessive addition of Ce (0.0360%) induced a sharp decrease in mechanical performance and an undesirable increase in the coefficient of thermal expansion (CTE). The Ni 5 Ce phase was unfavorable to the enhancement of mechanical properties and low thermal expansion behavior. Last but not least, 0.0170 wt% Ce content was advised for Fe-36Ni Invar alloy by considering the balance of strength and thermal expansion behavior. • An approach for Fe-36Ni Invar alloy by Ce treatment was proposed. • The grain size and fraction of annealing twins were sensitive to the Ce content. • Improved mechanical properties were obtained by proper Ce addition. • The proper addition of Ce decreased the coefficient of thermal expansion. • The optimum Ce content of Fe-36Ni Invar alloy was 0.0170%. [ABSTRACT FROM AUTHOR]

Aerogel, being extremely light and porous, is desirable for various applications of energetics such as a self-destructive microchip component. Additive manufacturing often requires a polymer binder which decreases thermal conductivity and changes combustion characteristics of the product. In this work, we fabricate a novel, polymer-free, reduced graphene oxide (rGO)-based Al/metal oxide nanothermite aerogel with a wide range of nanoparticle loading, via a new additive manufacturing process. SEM images revealed its unique porous structure formed by extra thin rGO sheets as the 3D skeleton, which wrapped Al and metal oxide nanoparticles into individual nanothermite clusters. DSC-TGA results and high-speed combustion videos confirmed the enhanced energetic performance of the printed specimen, suggesting the important role of rGO. A high linear burning rate of 5.8 m/s was achieved for a printed rGO/Al/metal oxide sample with a diameter of 1.6 mm (1/16") at 95 % thermite nanoparticle loading, and the propagation occurred at roughly the same rate with and against the print direction. This method allows for more complex 3D printing fabrication of various rGO/nanoparticle aerogels. Thermal camera footage clearly indicated the generation and increase of the pre-heating zone, reaction front, and cooling zone during the propagation. This method allows for more complex 3D printing fabrication of various rGO/nanoparticle aerogels. [Display omitted] • A novel room-temperature direct ink writing method for polymer-free rGO-nanoparticle aerogel. • Aerogel presents a unique porous structure and high nanoparticle loading up to 95 %. • Two different metal oxide nanoparticles were tested to develop nanothermite aerogel. • Fast and controllable linear combustion propagation rate between 10 cm/s and 5 m/s. • Increased heat transfer rate due to the highly conductive rGO scaffold. [ABSTRACT FROM AUTHOR]