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In the present research, the impacts of Ce additions at various concentrations (0, 1.0, 3.4, and 4.0 wt.%) on the evolution of the microstructure, mechanical properties, and thermal conductivity of as-cast and as-extruded Mg-3Sn alloys were investigated. The findings demonstrate that adding Ce caused the creation of a new ternary MgSnCe phase in the magnesium matrix. Some new Mg17Ce2 phases are generated in the microstructure when Ce levels reach 4%. The thermal conductivity of the Mg-3Sn alloy is significantly improved due to Ce addition, and the Mg-3Sn-3.4Ce alloy exhibits the highest thermal conductivity, up to 133.8 W/(m·K) at 298 K. After extrusion, both the thermal conductivity and mechanical properties are further improved. The thermal conductivity perpendicular to the extrusion direction of Mg-3Sn-3.4Ce alloy could achieve 136.28 W/(m·K), and the tensile and yield strengths reach 264.3 MPa and 227.2 MPa, with an elongation of 7.9%. Adding Ce decreases the dissolved Sn atoms and breaks the eutectic α-Mg and Mg2Sn network organization, leading to a considerable increase in the thermal conductivity of as-cast Mg-3Sn alloys. Weakening the deformed grain texture contributed to the further enhancement of the thermal conductivity after extrusion. [ABSTRACT FROM AUTHOR]

One-dimensional negative thermal expansion material has important applications in thermal expansion control and fiber toughened composite. Orthorhombic Al1.6Sc0.4Mo3O12 nanofibers have been prepared by electrospinning. The phase composition, microstructure, morphology, and thermal expansion performance of the samples prepared at various temperatures were investigated. Results show that as-prepared Al1.6Sc0.4Mo3O12 nanofibers are smooth and homogeneous with a fiber diameter of about 370.00 nm, but they show an amorphous structure. Orthorhombic Al1.6Sc0.4Mo3O12 nanofibers can be obtained at 550 ℃ with a diameter of around 140.00 nm. With the increase of post-annealing temperatures, the crystallization of the samples was improved. However, higher post-annealing temperatures will destroy the nanofiber structure of the samples. HTXRD reveals that orthorhombic Al1.6Sc0.4Mo3O12 nanofibers show anisotropic NTE in 25–700 °C. The expansion coefficients αa, αb, and αc of Al1.6Sc0.4Mo3O12 nanofibers are −5.05 × 10–6 °C−1, 4.41 × 10–6 °C−1, and −3.18 × 10–6 °C−1, respectively. The αv is −3.83 × 10–6 °C−1, and the corresponding αl is −1.28 × 10–6 °C−1. [ABSTRACT FROM AUTHOR]

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

This study focused on developing microstructural, thermal, and radiation shielding changes in Al50Si25B25 powders using mechanical alloying techniques. Based on the x‐ray powder diffraction data, the crystallite size and microstrain of the 100‐hours milled powder were calculated as 0.25 nm and 50.33 %, respectively. The solubility of silicon in the α‐aluminium matrix increased with longer mechanical alloying duration. Transmission electron microscope analyses further showed that the alloy particulates had an average size of 3 μm and an average grain size of 0.226 nm. The radiation shielding properties of the Al50Si25B25 powders indicated that the Linear Attenuation Coefficient value increased from 0.0554±0.1689 cm−1 to 1.0632±0.2425 cm−1 with an increase in the thickness of the Al50Si25B25 alloy. This work successfully demonstrated the potential of mechanical alloying techniques to enhance the microstructural and thermal properties of Al50Si25B25 powders. It highlighted their effectiveness in providing radiation shielding capabilities when varying the thickness of the alloy. [ABSTRACT FROM AUTHOR]

PC/ABS blends are commonly used for the production of automotive components due to their thermal and mechanical properties. However, changes in process conditions can have a significant impact on their properties and microstructure. Therefore, determining the optimal parameters for the injection molding (IM) process is critical for effective control of the mechanical properties and quality of the injected parts. In this study, the Taguchi method is applied to investigate the relationship between the tensile stress (σ), Young's modulus (E) and IM process of PC/ABS blends. The effects of different molding parameters such as material temperature, injection pressure, holding time and mold temperature were investigated. The optimal injection parameters to achieve higher tensile stress (σ) and Young's modulus (E) were predicted by studying the signal-to-noise ratio (S/N). Thus, the objectives of the Taguchi approach for the IM process are to determine the optimal combination of process parameters and to reduce the quality variations between only a few trials. Two optimal parameter combinations were found yielding very significant mechanical properties (σ, E) of the injected parts. These optimum combinations consist of material temperature of 260 °C, injection pressure ranging between 40 and 50 bar, holding time of 8 s and mold temperature of 60 °C. Experimental results prove that injection pressure and material temperature have the most significant impact on the mechanical properties and the microstructure of PC/ABS blends. These findings may have interesting applications in the automotive industry. [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]

Si3N4 ceramics with high mechanical properties and thermal conductivity, exhibiting fine and bimodal microstructure, were prepared by adjusting the Er2O3/MgO ratio and hot‐pressing sintering at 1800°C for 4 h. The microstructure, grain distribution, lattice oxygen content, mechanical properties, and crack propagation process of the sintered bulk samples were systematically investigated. It was found that a low Er2O3/MgO ratio contributed to the densification of Si3N4 ceramics, whereas a high Er2O3/MgO ratio favored the grain growth of Si3N4 ceramics. In this research, the grain size distribution and average diameters as well as their impact on mechanical properties were examined. When the ratio of Er2O3/MgO was 3:1, Si3N4 had a larger average diameter and higher thermal conductivity, but the mechanical properties were somewhat reduced. When the ratio of Er2O3/MgO was 2:2, the sample displayed enhanced mechanical performance, which can be explained by the formation of a bimodal structure. The research indicates that it is feasible to control the microstructure and optimize the mechanical properties of Si3N4 ceramics by tailoring the sintering additives. [ABSTRACT FROM AUTHOR]

Summary: The inherent poor cooking quality and poor texture of mixed‐grain pasta limit consumer acceptance. This study systematically investigated the effect of curdlan in the processing of sweet potato puree oat mixed‐grain noodles, and comprehensively analysed a number of key indicators such as cooking characteristics, moisture state, texture properties, microstructure, starch crystallinity characteristics, short‐range ordered structure and thermal properties. At the production practice level, the study clearly indicated that the 0.6% curdlan addition ratio was the best solution in sweet potato puree oat mixed‐grain noodles processing. This finding not only significantly reduces the fracture rate, water absorption rate and cooking loss rate during the cooking process, but also significantly improves the quality and yield of the product, and brings significant improvement in the taste and texture of the noodles, which is of great significance for industrial production. In the microstructural and molecular studies, we revealed how curdlan could enhance the structural stability and mechanical strength of noodles by promoting the uniform distribution of starch granules in the gluten protein network. Further, through X‐ray diffraction, ordered structure and thermal property analyses, we have found that colchicine can effectively regulate the interactions of hydrogen bonding between starch and the content of straight‐chain and branched‐chain starch, which significantly reduces the crystallinity, ordered short‐chain structure and enthalpy of pasting of starch in the pasta. These in‐depth research results not only help us to understand more comprehensively the formation mechanism of the modification of pasta quality by curdlan, but also provide a solid theoretical foundation and practical guidance for the improvement of pasta quality in mixed grains. [ABSTRACT FROM AUTHOR]

To solve the decrease in the crystallization, mechanical and thermal properties of recycled polyethylene terephthalate (rPET) during mechanical recycling, the aromatic amide fatty acid salt nucleating agents Na-4-ClBeAmBe, Na-4-ClBeAmGl and Na-4-ClAcAmBe were synthesized and the rPET/nucleating agent blend was prepared by melting blending. The molecular structure, the thermal stability, the microstructure and the crystal structure of the nucleating agent were characterized in detail. The differential scanning calorimetry (DSC) result indicated that the addition of the nucleating agent improved the crystallization temperature and accelerated the crystallization rate of the rPET. The nucleation efficiencies (NE) of the Na-4-ClBeAmBe, Na-4-ClBeAmGl and Na-4-ClAcAmBe were increased by 87.2%, 87.3% and 41.7% compared with rPET which indicated that Na-4-ClBeAmBe and Na-4-ClBeAmGl, with their long-strip microstructures, were more conducive to promoting the nucleation of rPET. The equilibrium melting points (T 0 m) of rPET/Na-4-ClBeAmBe, rPET/Na-4- ClBeAmGl and rPET/Na-4-ClAcAmBe were increased by 11.7 ◦C, 18.6 ◦C and 1.9 ◦C compared with rPET, which illustrated that the lower mismatch rate between rPET and Na-4-ClBeAmGl (0.8% in b-axis) caused Na-4-ClBeAmGl to be the most capable in inducing the epitaxial crystallization and orient growth along the b-axis direction of the rPET. The small angle X-ray diffraction (SAXS) result proved this conclusion. Meanwhile, the addition of Na-4-ClBeAmGl caused the clearest increase in the rPET of its flexural strength and heat-distortion temperature (HDT) at 20.4% and 46.7%. [ABSTRACT FROM AUTHOR]

Al–Zn–Mg–Cu alloys have been prepared using the gravity die-casting process. The influence of copper addition on microstructure, mechanical and thermal properties are studied. The experimental alloys were prepared using 5754 alloys, Al–Cu alloys, and pure zinc (solid form). Alloys are mechanically stirred for uniform distributions of alloying elements and precipitate phases. Four alloys with different copper weight percentages (0.02 wt%, 0.89 wt%, 1.57 wt%, and 3.34 wt%) were prepared. The α-Al and η (MgZn2) phases are observed in as-cast Al–Zn–Mg alloy. The addition of copper in Al–Zn–Mg alloys formed a θ phase (Al2Cu). Micro-Vickers hardness of Al–Zn–Mg–Cu alloy increased (from 116 HV1 to 133 HV1) with copper addition (0.02–1.57 wt%) at firstly due to the formation of θ phase (Al2Cu). Then, micro-Vickers hardness decreases due to high amounts of precipitates. Copper addition reduces the melting point (623–612 °C) and precipitation temperature (472–466 °C) of aluminum alloy. Al–Zn–Mg alloys have tensile strength of 422 MPa due to precipitates phase formation of η and T phases, solid solution strengthening (zinc and magnesium). Copper addition increases tensile strength due to the formation of θ phases. After achieving a strength of 486 MPa at an elongation of 3.72% (1.57 wt% Cu), tensile strength reduces due to a higher amount of precipitates. [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]

Polymeric materials are progressively taking the place of ceramic materials in insulators for high voltage transmission as a result of their disadvantages, such as their high weight, weak mechanical strength, and challenging manufacturing processes. In most situations, polymeric insulators are preferable to ceramic insulators, although they can have drawbacks such low operating temperature and toughness. This research's objective was to improve an epoxy composite produced with oyster shell nanoparticles for the production of high insulating electrical insulator for high voltages application. The solution stir-cast process was used to develop the composites. Microstructure, tensile and impact strength, and electrical conductivity were all measured. Electrical conductivity decreased by 99.62%, while tensile strength increased by 96.74 %. The developed composites withstand 12.5 kV. High-strength electrical insulators may be made using this recipe and the composite material developed.

MCrAlY (M = Ni and/or Co) metallic coatings are essential for the protection of hot-end components against thermal and corrosion damage. Increasing the Al content is considered a feasible solution to improve the high-temperature performance of MCrAlY coatings. In this paper, the effects of high Al contents (12–20 wt.%) on the phase constituents and cast microstructures in MCrAlY alloys were studied by high-energy X-ray diffraction and electron microscopy techniques combined with phase equilibria calculations. High Al content improved the stability of β, σ, and α phases. Meanwhile, an evolution of the cast microstructure morphology from a dendrite structure to an equiaxed grain structure was observed. The thermal properties were analyzed, which were closely related to the phase constituents and solid-to-solid phase transitions at evaluated temperatures. This work is instructive for developing high-Al-content MCrAlY coatings for next-generation thermal barrier applications. [ABSTRACT FROM AUTHOR]

The microstructure of mesophase pitch carbon fibers (CFs) are tuned by varying ramp rates from 1 to 50 °C min−1 up to 1000 °C to study the effect of ramp rate on CFs' microstructure, thermal and mechanical properties with the goal of offsetting the cost by decreasing cycle time. The ramp rates represent carbonization times ranging from 16.4 to 1.17 h, not including cool down. Differential scanning calorimetry, thermogravimetric analysis, and derivative thermogravimetry are used to investigate the impact ramp rate has on the thermal properties of mesophase pitch. It is found that lower ramp rates are endothermic in nature with a lower temperature onset and maximum weight loss. Higher ramp rates possess an exothermic nature with higher temperatures resulting in maximal weight loss over a smaller range of temperatures. Mechanical testing shows varying CF strengths and moduli dependent on ramp rate and an optimized process is developed to produce the strongest CF. Microstructural characterization revealed that faster ramp rates lead to smaller interplanar spacings and larger crystallites but possessed greater disorder. [ABSTRACT FROM AUTHOR]

This study was conducted on SAC105 (Sn-1wt.%Ag-0.5wt.%Cu) lead-free solder modified with Bi and Sb. The wetting, melting point, and mechanical properties were analysed with the addition of 1~5 wt.%Bi and 1~5 wt.%Sb for SAC105 base alloy. The wetting characteristics were assessed by wetting time (zero cross time, ZCT) obtained from wetting balance tests. The mechanical properties were analysed by tensile tests. Considering two factors (Bi, Sb), a three-level (0, 1, 2 wt.%) design of experiment (DOE) method array was applied for Taguchi optimization. The results indicated that the solder wetting increased as Bi content increased, while it decreased with Sb. The ZCT decreased with increasing Bi content up to 4 wt.%, while it increased proportionally to Sb content. The melting point, measured using a differential scanning calorimeter (DSC), showed that the melting point tended to decrease according to Bi increase, while it increases depending on the Sb content. Increase in Bi and Sb levels resulted in enhanced tensile strength in the mechanical properties tests, with Bi having a more noticeable impact. The Taguchi optimized conditions for the Bi and Sb studies were found to be 2 wt.%Bi and 2 wt.%Sb. This led to an optimal set of 0.9 s of wetting time, a 222.55 °C melting point, a 55 MPa tensile strength, and a 50% elongation. [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]

In this study, the composition-dependent properties of a new type of NiTiCuW shape memory alloy were investigated. The martensite transformation temperature was measured by differential scanning calorimetry, crystal structure by XRD, microstructure analysis by microhardness measurement and scanning electron microscopy. The increase in Cu/W ratio in the composition decreased the transformation temperature below room temperature, and the alloys are in austenite phase at room temperature. X-ray results also supported the thermal measurement results. Moreover, a difference in the microhardness values of NiTiCuW alloys was observed, which exhibited martensite phase and austenite phase at room temperature. [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]

Zirconium carbide (ZrC) ceramics have a high melting point, low neutron absorption cross section, and excellent resistance to the impact of fission products and are considered to be one of the best candidate materials for fourth-generation nuclear energy systems. ZrC ceramics with a high relative density of 99.1% were successfully prepared via pressureless sintering using a small amount of MoSi2 as an additive. The influence of the MoSi2 content on the densification behavior, microstructure, mechanical properties, and thermal properties of ZrC ceramics was systematically investigated. The results show that the densification of ZrC was significantly enhanced by the introduction of MoSi2 due to the formation of a liquid phase during sintering. In addition, the ZrC grains were refined due to the pinning effect of the generated silicon carbide. The flexural strength and Vickers hardness of ZrC ceramics with 2.5 vol% MoSi2 sintered at 1850 °C were 408 ± 12 MPa and 17.1 GPa, respectively, which were approximately 30% and 10% higher compared to the samples without the addition of MoSi2. The improved mechanical properties were mainly attributed to the high relative density (99.1%) and refined microstructure. [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]

The (1−x)CaO-B2O3-SiO2(CBS)/xMg2SiO4 composites were prepared and the influence of CBS crystallizable glass content on the sintering properties, dielectric properties, and thermal properties of the composites were investigated. The primary crystal phases in the CBS/Mg2SiO4 composites were CaMgSi2O6 and CaB2O4. An appropriate amount of Mg2SiO4 reduced the crystallization temperature of the composite. For x = 0.30, a sintering temperature of 890°C with a holding time of 60 min resulted in a bulk density of 2.645 g/cm3, dielectric constant of 6.6, and dielectric loss of 2.54 × 10−3 at 10 kHz. Prolonged holding time promotes grain growth; when extended from 60 min to 180 min for x = 0.30, the permittivity increased from 6.5 to 6.6 and Q×f increased from 10,100 GHz to 15,700 GHz when x = 0.30 at 13 GHz. The CTE of 70 wt.% CBS + 30 wt.% Mg2SiO4 composite was 9.5 ppm/°C, which approached the value of a circuit board for a ceramic ball grid array package (CBGA). [ABSTRACT FROM AUTHOR]

Lutetium monosilicate (Lu2SiO5) has been considered as environmental barrier coatings (EBCs) materials for SiCf/SiC. Microstructural evolution and thermal properties changes of the Lu2SiO5 coating would occur in high temperature environment. In this study, Lu2SiO5 coating was fabricated by vacuum plasma spray technique. The microstructure, thermal stability, thermal conductivity, as well as thermal expansion behavior of the coating before and after thermal aging at 1350 °C were investigated. The tri-layer EBCs of Lu2SiO5/Yb2Si2O7/Si were designed and prepared onto SiCf/SiC substrates, and its thermal shocking behaviors were also explored. Results showed that the as-sprayed coating was mainly composed of Lu2SiO5, Lu2O3 and amorphous phases, and significant microstructural evolution, such as grain growth and defects reduction, was observed after thermal aging. The coating exhibited linear expansion, and the CTE of the coating before and after heat treatment were similar, while the thermal conductivity increased after thermal aging. Thermal shock results showed that the coating remained intact after 100 cycles, and penetrating microcracks in the Lu2SiO5 top layer were mostly stopped at the Lu2SiO5-Yb2Si2O7 interface, indicating that the tri-layer EBCs on the SiCf/SiC substrate had good thermal shock resistance. The thermal shock behaviors were explained based on microstructure combined with thermal stresses analysis. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the present work is to study the impacts of rapid cooling and Tb rare-earth additions on the structural, thermal and mechanical behavior of Bi–0.5Ag lead-free solder for high-temperature applications. Design/methodology/approach: Effect of rapid solidification processing on structural, thermal and mechanical properties of Bi-Ag lead-free solder reinforced Tb rare-earth element. Findings: The obtained results indicated that the microstructure consists of rhombohedral Bi-rich phase and Ag99.5Bi0.5 intermetallic compound (IMC). The addition of Tb could effectively reduce the onset and melting point. The elastic modulus of Tb-containing solders was enhanced to about 90% at 0.5 Tb. The higher elastic modulus may be attributed to solid solution strengthening effect, solubility extension, microstructure refinement and precipitation hardening of uniform distribution Ag99.5Bi0.5 IMC particles which can reasonably modify the microstructure, as well as inhibit the segregation and hinder the motion of dislocations. Originality/value: It is recommended that the lead-free Bi-0.5Ag-0.5Tb solder be a candidate instead of common solder alloy (Sn-37Pb) for high temperature and high performance applications. [ABSTRACT FROM AUTHOR]

Magnesium chips were coated with a high concentration of graphite using a binder and were used as the raw material for injection molding. The microstructure of the magnesium injection-molded product with added graphite exhibited a dispersion of needle-like graphite particles. No significant voids were observed at the interfaces between the graphite and the matrix. The addition of more than 0.5 mass% graphite decreased the proof stress and tensile strength of the injection-molded products. The Young's modulus of the graphite-added products tended to decrease with an increase in the graphite content, which is consistent with the lower limit of the rule of mixtures. The thermal conductivity of the 6.9 mass% graphite-added product increased compared with that of the AZ91D magnesium alloy and the coefficient of linear thermal expansion decreased. Both values are within a range that satisfied the rules of mixtures. [ABSTRACT FROM AUTHOR]

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO2 powder, and KCl foaming agent as raw materials. Ni(NO3)2·6H2O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO2 powder. The influence of Ni(NO3)2·6H2O catalyst content (0, 5, 10 wt.% of the TiO2 powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO3)2·6H2O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively. [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 method has been developed for securing an optical fiber in a quartz connector by using sodium polysilicate hydrogel formed in a cylindrical gap between a connector and an optical fiber by means of alkaline decomposition of the quartz surfaces of manufactured components. The conditions for the thermal decomposition of hydrogel are determined, and it is shown that hydrogel decomposition with cellular structure formation is possible at temperatures below the thermal decomposition temperature of the polymer coating of the optical fiber. The hydrogel formation conditions and the thermal properties of the hydrogel are determined. Conclusions regarding the suitability of the proposed method for securing an optical fiber in a quartz connector are drawn. [ABSTRACT FROM AUTHOR]

Hybrid plasma spraying combines plasma spraying of dry coarse powders and liquids (suspensions or solutions) potentially providing high deposition rates and coatings with novel microstructures and amended functionality. Such composites may be potentially interesting also for the thermal barrier coatings (TBCs). In this study, the first experimental TBCs with hybrid ceramic top-coats were deposited by hybrid water-/argon-stabilized plasma (WSP-H) technology. Coarse dry YSZ (yttria-stabilized zirconia: ZrO2-Y2O3) powder was selected to form the top-coat matrix. Suspensions of YSZ, Al2O3 (alumina), YAG (yttrium aluminum garnet: Y3Al5O12), or GZO (gadolinium zirconate: Gd2Zr2O7) were the source of the additional miniature phase. Uniform functionalized coatings with TBC-relevant thickness and microstructure were successfully deposited. Hybrid and reference coatings deposited also with WSP-H torch and with YSZ feedstocks showed comparable thermal diffusivity regardless of the spraying conditions but the addition of Al2O3 and YAG increased it by ~ 65%, whereas GZO decreased it by ~ 20%. Thermal cycling resistance of the coatings was evaluated by thermal cycling fatigue (TCF) test. Hybrid coating with the addition of YSZ miniature phase endured on average 640 TCF cycles, which was 250-300 cycles less than the reference YSZ coatings deposited without liquid feedstocks but still comparable to the currently used YSZ-based industrial TBCs. Coatings with dissimilar chemistry of additional miniature splats showed inferior mean TCF lifetimes: GZO 438 cycles, Al2O3 272 cycles, and YAG 173 cycles, opening space for further coating optimization. All hybrid coatings failed above the bond-coat/top-coat interface. Comparison of coatings before and after the thermal exposure by scanning electron microscopy (SEM) and x-ray diffraction (XRD) revealed possible changes within the coating microstructure, namely sintering (typical for top-coat consisting only of YSZ), conversion of metastable and amorphous phase (top-coats with the addition of Al2O3 and YAG) or interaction between the matrix and secondary phase (top-coat with the addition of GZO). [ABSTRACT FROM AUTHOR]

This paper is dedicated to studying the effect of replacing molybdenum with vanadium on the tendency to amorphisation, structure, and thermal properties of high-entropy alloys of the (Fe0.25Ni0.25Co0.25Cr0.125Mo0.125‑xVx)100‑yBy system, where x = 0; 0.0625; 0.125 and y = 17–25. The alloy structure was analyzed using X‑ray diffraction, scanning and transmission electron microscopy methods. Thermal properties were determined by differential scanning calorimetry. It was found that the replacement of molybdenum with vanadium leads to the formation of crystalline particles of complex nitrides (V, Cr, Mo)(N, B) in the ribbon structure. The dependences of the characteristic alloy temperatures have been established. Molybdenum replacement with vanadium was shown to stabilize the supercooled liquid in alloys with completely amorphous structure. [ABSTRACT FROM AUTHOR]

The mesophase pitch-based carbon fiber interface material (TIM) with a vertical array was prepared by using mesophase pitch-based short-cut fibers (MPCFs) and 3016 epoxy resin as raw materials and carbon nanotubes (CNTs) as additives through electrostatic flocking and resin pouring molding process. The microstructure and thermal properties of the interface were analyzed by using a scanning electron microscope (SEM), laser thermal conductivity and thermal infrared imaging methods. The results indicate that the plate spacing and fusing voltage have a significant impact on the orientation of the arrays formed by mesophase pitch-based carbon fibers. While the orientation of the carbon fiber array has a minimal impact on the shore hardness of TIM, it does have a direct influence on its thermal conductivity. At a flocking voltage of 20 kV and plate spacing of 12 cm, the interface material exhibited an optimal thermal conductivity of 24.47 W/(m·K), shore hardness of 42 A and carbon fiber filling rate of 6.30 wt%. By incorporating 2% carbon nanotubes (CNTs) into the epoxy matrix, the interface material achieves a thermal conductivity of 28.97 W/(m·K) at a flocking voltage of 30 kV and plate spacing of 10 cm. This represents a 52.1% increase in thermal conductivity compared to the material without TIM. The material achieves temperature uniformity within 10 s at the same heat source temperatures, which indicates a good application prospect in IC packaging and electronic heat dissipation. [ABSTRACT FROM AUTHOR]

Rigid pavements at military airfields experience surface deterioration within 6–18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form of disintegration of aggregates and cement paste into small pieces that pose severe risks of physical injury to maintenance crews or damage to an aircraft engine. Since coarse aggregates typically occupy 60–80% of the concrete volume, aggregates' thermal properties and microstructure should play a crucial role in the degrading mechanism. At high temperatures, concrete with lightweight aggregates is reported to have better performance compared to concrete with normal-weight aggregate. Thus, the present study carried out a detailed investigation of the mechanical and thermal performance of lightweight aggregate concrete exposed to the combined effects of high temperatures and hydrocarbon oils simultaneously. To replicate harsh airfield operating conditions, standard-sized concrete cylinders were exposed to elevated temperatures using an electric oven. Additionally, a mixture of equal parts of aircraft engine oil, hydraulic oil, and kerosene was applied before each exposure to high temperatures. To identify the resistance of different concrete with various lightweight coarse aggregates, pumice, perlite, lytag (sintered fly ash), and crushed brick were used as lightweight coarse aggregates in concrete. Also, basalt aggregate concrete was used as a reference. After curing, cylinders were tested for the ultimate strength. Later, after every 20 cyclic exposures, three cylinders from each aggregate type were tested for residual comprehensive strength, thermal, chemical, and microstructural (SEM) properties. Overall, concrete with crushed brick aggregate and lytag used in this study showed superior resistance to the simulated airfield conditions. The findings of this study will provide valuable insights to select an appropriate coarse aggregate type for military airfield pavement construction, aiming to effectively minimize surface spalling. [ABSTRACT FROM AUTHOR]

The chemical corrosion resistance properties of newly developed oxide (mullite-, cordierite)-bonded SiC ceramics prepared using mixture of waste fly ash and metal oxide additives were investigated in environments containing Na2SO4 at temperature 1000 °C for 8 h. The thermal shock resistance to cooling were evaluated as a function of quenching cycles. The changes in weight, flexural strength, and morphology due to thermal and chemical corrosion were examined. The mechanisms of flexural strength degradation due to chemical and thermal corrosion were analyzed, and the results were compared with literature data. In the hot corrosion by Na2SO4, the cordierite component was severely attacked in the cordierite-bonded SiC ceramics resulted ~ 34% strength degradation after 8 h corrosion; on the contrary, mullite-bonded SiC ceramics exhibited ~ 4% improvement of flexural strength. The chemical and thermal shock resistance results suggest a potential advantage of porous SiC ceramics prepared using waste fly ash for several industrial applications. [ABSTRACT FROM AUTHOR]

To optimize their Al2O3-SiO2 raw materials, anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1 350 ℃ for 3 h, using green and pollution-free kaolin, kyanite, andalusite and sillimanite as Al2O3-SiO2 raw materials, respectively, and industrial CaCO3 as the CaO source. Effects of Al2O3-SiO2 raw material types on the physical properties, phase composition and microstructure were investigated. The results are as follows. All samples prepared by different Al2O3-SiO2 raw materials have hexagonal flake anorthite and a small amount of mullite and corundum. Their bulk density and thermal conductivity decrease in the order of using kaolin, andalusite, kyanite and sillimanite as the Al2O3-SiO2 raw material, but their apparent porosity increases. Moreover, in the sample with kaolin, the bonding between anorthite crystals on the pore walls is closer than that of the other samples, which is conducive to increasing the cold crushing strength. The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite, andalusite and sillimanite as the Al2O3-SiO2 raw material, thus their cold crushing strength decreases accordingly. In comprehensive consideration, the properties of the sample from kyanite are the optimal. Its apparent porosity, thermal conductivity and cold crushing strength are 84.6%, 0.141 W·m-1·K-1 and 1.89 MPa, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers 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.)

The thermal properties of the aluminum EN AW-2024 alloy (duralumin) delivered in the T3 condition (solution annealed, quenched, cold-deformed, and naturally aged) were experimentally investigated using differential thermal analysis (DTA), differential scanning calorimetry (DSC), and light flash apparatus (LFA) for thermal diffusivity and thermal conductivity evaluation. The microstructure of the alloy in the initial state and after heating to 400?C was investigated by scanning electron microscope (SEM) and energy-dispersive spectroscopy. The presence of an exothermic thermal effect in the temperature range from 230 to 283?C during the first heating of the examined sample was determined by the results of DTA/DSC analysis. The thermal diffusivity of the investigated alloy was measured in the temperature range from 25 to 400?C using three heating runs. During the first heating, the thermal diffusivity of the investigated alloy increased with an increase in temperature up to approximately 300?C, after which it decreased. During the second and third heating, it was observed that the measured thermal diffusivity values at temperatures lower than 300?C were significantly higher than during the first heating, and the thermal diffusivity gradually decreased with increasing temperature in the entire investigated temperature range. Experimentally determined thermal diffusivity and density, as well as calculated specific heat capacity data, were used to determine the thermal conductivity of the studied alloy in the temperature interval from 25 to 400?C. The obtained results indicate that initial heating to a temperature above 300?C causes a significant increase in the values of the thermal diffusivity and thermal conductivity of the investigated 2024-T3 alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic 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.)

This article proposes a modeling method for C/C-ZrC composite materials. According to the superposition of Gaussian random field, the original gray model is obtained, and the threshold segmentation method is used to generate the C-ZrC inclusion model. Finally, the fiber structure is added to construct the microstructure of the three-phase plain weave composite. The reconstructed inclusions can meet the randomness of the shape and have a uniform distribution. Using an algorithm based on asymptotic homogenization and finite element method, the equivalent thermal conductivity prediction of the microstructure finite element model was carried out, and the influence of component volume fraction on material thermal properties was explored. The sensitivity of model parameters was studied, including the size, mesh sensitivity, Gaussian complexity, and correlation length of the RVE model, and the optimal calculation model was selected. The results indicate that the volume fraction of the inclusion phase has a significant impact on the equivalent thermal conductivity of the material. As the volume fraction of carbon fiber and ZrC increases, the equivalent thermal conductivity tensor gradually decreases. This model can be used to explore the impact of material microstructure on the results, and numerical simulations have studied the relationship between structure and performance, providing the possibility of designing microstructure based on performance. [ABSTRACT FROM AUTHOR]

Rigid pavements at military airfields experience surface deterioration within 6–18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form of disintegration of aggregates and cement paste into small pieces that pose severe risks of physical injury to maintenance crews or damage to an aircraft engine. Since coarse aggregates typically occupy 60–80% of the concrete volume, aggregates’ thermal properties and microstructure should play a crucial role in the degrading mechanism. At high temperatures, concrete with lightweight aggregates is reported to have better performance compared to concrete with normal-weight aggregate. Thus, the present study carried out a detailed investigation of the mechanical and thermal performance of lightweight aggregate concrete exposed to the combined effects of high temperatures and hydrocarbon oils simultaneously. To replicate harsh airfield operating conditions, standard-sized concrete cylinders were exposed to elevated temperatures using an electric oven. Additionally, a mixture of equal parts of aircraft engine oil, hydraulic oil, and kerosene was applied before each exposure to high temperatures. To identify the resistance of different concrete with various lightweight coarse aggregates, pumice, perlite, lytag (sintered fly ash), and crushed brick were used as lightweight coarse aggregates in concrete. Also, basalt aggregate concrete was used as a reference. After curing, cylinders were tested for the ultimate strength. Later, after every 20 cyclic exposures, three cylinders from each aggregate type were tested for residual comprehensive strength, thermal, chemical, and microstructural (SEM) properties. Overall, concrete with crushed brick aggregate and lytag used in this study showed superior resistance to the simulated airfield conditions. The findings of this study will provide valuable insights to select an appropriate coarse aggregate type for military airfield pavement construction, aiming to effectively minimize surface spalling.

Titanium alloys are considered one of the most promising materials. However, their poor thermal expansion property remains a major obstacle to their widespread application. In this study, we explored an innovative design strategy to tune the thermal expansion properties of titanium alloy. Specifically, we used rare earth iron intermetallic compounds (Gd-Fe IMCs) with low coefficient of thermal expansion (CTE) as expansion inhibitors to prepare composites with the required thermal expansion properties via in situ reaction. The morphology and size of Gd-Fe IMCs can be effectively controlled by electromagnetic and ultrasonic fields, resulting in a dense distribution of micro/nano-structured Gd-Fe IMCs and strong interfacial bonding of the composites. This alloy has an excellent CTE of 6.8 × 10 ^−6 /K and a high ultimate tensile strength of 921 MPa. The improvement in the physical properties (especially in thermal expansion properties) of titanium alloy can be attributed to the synergistic effect between Gd-Fe IMCs and Ti matrix. This design strategy can also be extended to other titanium alloys as a reference for designing low thermal expansion titanium alloys.

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]