High Temperature Performance Research Articles

Polyimide-coated MgO nanoparticles improves high-temperature energy storage performance in polyetherimide-based nanocomposite films

Enhancing the energy storage capacity of dielectric polymers can be achieved by the introduction of inorganic nanoparticles. However, the difference in surface energy often influences the interfacial compatibility of nanoparticles with polymers, consequently limiting their comprehensive dielectric properties. Here, the magnesium oxide (MgO) nanoparticles were coated with polyimide (PI) shells via in-situ polymerization, which is beneficial to improve the scattered particles in the polyether imide (PEI) matrix. The PI buffer shell is tightly bound to the PEI matrix through automatic electrostatic interaction making the defects decrease, together with the increased dielectric permittivity (εr) attributed to MgO, significantly enhancing the discharged energy density (Udis) and storage efficiency (η) of the PI@MgO/PEI nanocomposite films in harsh conditions. Thus, the maximal Udis of the PI@MgO/PEI nanocomposites is 4.33 J/cm3 at 150 °C, twice that of the pristine PEI. Even if an η exceeds 90 %, the Udis of 3.83 J/cm3 of 1 vol%-PI@MgO/PEI at 500 MV/m and 150 °C is better than that of the most advanced dielectric polymers.

Surface phosphating modification of FeCoNiMn high-entropy alloys for efficient electromagnetic-wave absorption performances

FeCoNi-based magnetic high-entropy alloys (HEAs) have attracted much attention as an emerging electromagnetic-wave absorbing (EMA) material. In this study, FeCoNiMn HEAs flake powders were prepared by high-energy ball-milling and phosphating using phosphoric acid-anhydrous ethanol solutions. The micro-morphology, static magnetic properties, corrosion resistance, high-temperature oxidation resistance and EMA performances of the samples were systematically investigated. The results showed that the phosphate protective film can be generated on the powder surface by phosphating treatment, which enhanced dielectric loss and improved the corrosion resistance and high-temperature oxidation resistance of HEAs. The #P50 had a minimum reflection loss of −62.4 dB at 10.7 GHz and an effective bandwidth of 4.1 GHz. Therefore, the phosphated HEAs have excellent EMA performances and great adaptability to harsh service environments, which provide a new idea for the study of EMA materials.

The mechanical properties and high-temperature oxidation behavior of (TiZr)65-x-yNb15Mo20SixAly refractory high entropy alloys

Herein, the mechanical properties and high-temperature oxidation of (TiZr)65-x-yNb15Mo20SixAly refractory high-entropy alloys were systematically investigated. Results indicate that alloying with Si improves the strength but reduces the plasticity of the alloy. Maintaining a proper ratio of Al/Si is crucial to achieve the optimal performance of the alloy. The (TiZr)50.5Nb15Mo20Si9.5Al5 has excellent high-temperature performance, with a yield strength of 815 MPa at 800°C and a compressive strain greater than 40 %. Moreover, the (TiZr)50.5Nb15Mo20Si9.5Al5 exhibits a superior oxidation resistance compared to (TiZr)55Nb15Mo20Si10 alloy at 1000℃. The introduction of Si enhances the oxidation resistance, decreases the diffusion of the Zr element at 1000 °C and facilitates internal oxidation and the creation of TiNb2O7. However, it is important to note that the doping of Al in the higher Si alloys has negative impacts on the oxidation resistance and mechanical properties.

Effects of yttrium on microstructure and low cycle fatigue properties of superalloy IN713C at high temperature

In order to improve the high temperature and low cycle fatigue performance of the IN713C alloy, trace amounts of yttrium (Y) element were added to such an alloy. The effect of Y on the microstructure and fatigue performance under push-pull loading condition of the IN713C alloy at 650 °C was investigated, and the fracture mechanisms of the IN713C alloy with different Y additions at strain amplitudes of 0.3%, 0.4% and 0.5% were also investigated. The results showed that addition of Y significantly increased the fatigue life of the IN713C alloy under different strain amplitude values. Compared with the traditional IN713C, the fatigue life of the alloy with 300 ppm Y was increased by 44.4%, 213.3%, and 61.4%, and that of the alloy with 500 ppm Y was increased by 184.6%, 66.1%, and 172.1%, respectively, at the strain amplitudes of 0.3%, 0.4%, and 0.5%. Shrinkage pores were found to be the main crack source at low strain amplitude (0.3%), while carbides and other interdendritic precipitates were the source of cracks at high strain amplitude (0.4% and 0.5%). The addition of Y increased the fatigue life of the IN713C alloy by reducing shrinkage and refining carbides and grain size.

Gadolinium doping induced the microstructure evolution and mechanical properties improvement of Nb-Si based in-situ superalloy

Nb-Si superalloy is one of the most potential structure-materials of next generation aero engine. The influence of rare-earth element Gd on microstructure and mechanical properties of Nb-16Si-24Ti is explored in this paper. Results show that phase composition no change by doping of Gd. And the mass of Nbss/(Nb, X)3Si eutectic exists in the matrix instead of primary Nbss. The rare-earth element Gd reduces the Si contents in Nbss phases, and the content of O is also limited because of its high active. The deflection, bridging and secondary crack are easily found in coarsened Nbss, and the peak-value of fracture toughness is 8.37 MPa·m1/2 in NST-0.05Gd alloy. The phenomenon of solution strength is obvious, and the maximum value of RT compressive strength is 2214 MPa. The thermal compression test indicates that silicide phases play the major role for high-temperature performance, and the Nbss phases have the poor heat-resistance under HT condition.

(Electronics and Photonics Division Poster Award Winner) Operation up to 225°C of NiO/ β-(Al0.21Ga0.79)2O3 /Ga2O3 Heterojunction Lateral Rectifiers

The characteristics of NiO/β-(Al0.21Ga0.79)2O3/Ga2O3 heterojunction lateral geometry rectifiers with the epitaxial layers grown by metal organic chemical vapor deposition were measured over a temperature range from 25 °C–225 °C. The forward current increased with temperature, while the on-state resistance decreased from 360 Ω.cm2 at 25 °C to 30 Ω•cm2 at 225 °C. The forward turn-on voltage was reduced from 4 V at 25 °C to 1.9 V at 225 °C. The reverse breakdown voltage at room temperature was ∼4.2 kV, with a temperature coefficient of −16.5 V•K−1. This negative temperature coefficient precludes avalanche being the breakdown mechanism and indicates that defects still dominate the reverse conduction characteristics. The corresponding power figures-of-merit were 0.27–0.49 MW•cm−2. The maximum on/off ratios improved with temperature from 2105 at 25 °C to 3 × 107 at 225 °C when switching from 5 V forward to 0 V. The high temperature performance of the NiO/β-(Al0.21Ga0.79)2O3/Ga2O3 lateral rectifiers is promising if the current rate of optimization continues.

A new method to calculate and predict thermodynamic properties of nonpolar, polar and quantum fluids at high temperatures

As the only known equation of state (EOS) with the rigid theoretical foundation, the virial equation of state (VEOS) can be reliable enough to describe real-gas imperfection for low-to-moderate densities when truncated after the second or third virial coefficient. In our previous work, on the basis of the corresponding state principle, the generalized second and third virial coefficient models were proposed for nonpolar, polar and quantum fluids in a wide temperature range. In this work, combined with the ideal heat capacities, the high-temperature performance of the truncated VEOSs was evaluated on derived thermodynamic properties including speed of sound, isobaric heat capacity, entropy and internal energy. The criterion for being “valid” is defined as 1% relative deviation from the multiparameter EOSs, and this work presents the valid density and pressure regions of the truncated VEOSs for the derived thermodynamic properties. The truncated VEOSs have valid densities of the saturated densities below the critical temperatures, and have valid densities that tend to be constant beyond the critical temperatures. The SRK EOS is chosen as the representative of generalized EOSs. By the comparisons with the SRK EOS, the truncated VEOSs show the advantage in stability and universality. The truncated VEOSs can give a reliable extrapolation with wide applicable pressure ranges at high temperatures for nonpolar, polar and quantum fluids. The applicable density regions of the truncated VEOSs for derived thermodynamic properties are recommended to be the valid density regions of the pvT property. The applicable temperature ranges of the truncated VEOSs for derived thermodynamic properties are determined by the temperature ranges of the available ideal heat capacity data.

Sandwich probe temperature sensor based on In2O3-IZO thin film for ultra-high temperatures

High-temperature thin-film thermocouples (TFTCs) have attracted significant attention in the aerospace and steel metallurgy industry. However, previous studies on TFTCs have primarily focused on the two-dimensional planar-type, whose thermal sensitive area has to be perpendicular to the test environment, and therefore affects the thermal fluids pattern or loses accuracy. In order to address this problem, recent studies have developed three-dimensional probe-type TFTCs, which can be set parallel to the test environment. Nevertheless, the probe-type TFTCs are limited by their measurement threshold and poor stability at high temperatures. To address these issues, in this study, we propose a novel probe-type TFTC with a sandwich structure. The sensitive layer is compounded with indium oxide doped zinc oxide and fabricated using screen-printing technology. With the protection of sandwich structure on electrode film, the sensor demonstrates robust high-temperature stability, enabling continuous working at 1200 °C above 5 h with a low drift rate of 2.3 °C·h−1. This sensor exhibits a high repeatability of 99.3% when measuring a wide range of temperatures, which is beyond the most existing probe-type TFTCs reported in the literature. With its excellent high-temperature performance, this temperature sensor holds immense potentials for enhancing equipment safety in the aerospace engineering and ensuring product quality in the steel metallurgy industry.

Preparation and Characterization of Bio-Asphalt Based on Sludge-Derived Heavy Oil

To achieve the efficient resource utilization of municipal sludge and promote the sustainability of pavement materials, this study employed liquefaction technology to process municipal sludge. The resulting liquefied-sludge-derived heavy oil was blended with 50# asphalt to prepare a bio-asphalt that can replace petroleum asphalt. Firstly, orthogonal experiments were conducted to analyze the effects of the solid–liquid ratio (dried sludge:anhydrous ethanol), liquefaction temperature, and reaction time on the yield of the sludge-derived heavy oil. Then, the basic characteristics of the sludge-derived heavy oil were studied using an elemental analyzer, gel permeation chromatography, thermal analysis, gas chromatography–mass spectrometry, and Fourier transform infrared spectroscopy, and the differences between the sludge-derived heavy oil and petroleum asphalt were compared. Finally, to determine the appropriate content range of sludge-derived heavy oil in bio-asphalt, a comprehensive evaluation of the three major indicators, aging resistance, storage stability, low-temperature performance, and high-temperature performance was carried out for the prepared bio-asphalts. The results indicated that the optimal preparation process for liquefied sludge oil involves a liquefaction temperature of 275 °C, a solid–liquid ratio of 1:15, and a reaction time of 1 h, resulting in an oil production rate of 22.36%. The sludge-derived heavy oil demonstrated good thermal stability, with its primary components being aliphatic compounds (carboxylic acids, ketones, aldehydes, alcohols, alkanes, esters, etc.), with esters being the most abundant. Furthermore, the sludge-derived heavy oil was highly compatible with 50# asphalt, but no chemical reaction occurred between them. When the sludge-derived heavy oil content ranged from 5% to 20%, bio-asphalt showed favorable aging resistance and storage stability. As the content of the sludge-derived heavy oil increased, its low-temperature performance improved, but there was a slight decrease in high-temperature performance. Additionally, correlation analysis highlighted that the influence of sludge-derived heavy oil content on the high-temperature performance of bio-asphalt was notably greater than on other properties. Therefore, the recommended dosage of sludge-derived heavy oil should be between 5% and 10%.

Cooling performance enhancement of electric vehicle film capacitor for ultra-high temperatures using micro-channel cold plates thermal management system

The increasing voltage and power density demands of electric vehicles pose notable challenges to the high-temperature resistance performance of film capacitors within motor controllers. Existing methods primarily focus on material modifications and conventional thermal management designs, often tested at 85 °C, which fail to meet the escalating demands for high-temperature operations. This paper presents the design and optimization of a thermal management system for film capacitors through simulations and experiments under ultra-high temperatures. ANSYS electro-thermal coupled simulation was used to analyze the temperature distribution of the capacitor under different ripple currents, leading to the development of a thermal management system based on internal micro-channel cold plates (IMCPs). These IMCPs were optimized using response surface and genetic algorithms to enhance cooling performance. Experimental and simulation comparisons were made between standard capacitors and those with IMCPs under ripple currents of 120 A and 180 A at 85 °C. Further examinations were conducted at ultra-high temperatures of 125 °C and 140 °C with a ripple current of 180 A. The findings show that capacitors with IMCPs had average temperature reductions of 45.50 °C and 48.45 °C at 85 °C under 120 A and 180 A ripple currents, respectively. Additionally, standard capacitors developed cracks or exploded at 125 °C and 140 °C under 180 A ripple current, while capacitors with IMCPs maintained normal functionality. These results indicate that capacitors integrated with IMCPs meet the rigorous high-temperature operational standards required for motor controllers in high-voltage electric vehicles.

A novel oxide ceramic matrix composite with integrated high-temperature EMW absorption and mechanical performance

Oxide ceramic matrix composites (OCMC) are extensively used as thermal structural materials due to good high-temperature resistance, mechanical properties, and oxidation resistance, but they are rarely regarded as electromagnetic wave absorbing materials due to the high resistivity of oxide ceramics/fibers. However, high-performance Al2O3 fiber can be used to design and fabricate OCMC with integrated high-temperature microwave absorbing and mechanical properties by introducing dielectric material into Si-based ceramic matrix. The N610/Si3N4-SiOC composites have the prior mechanical performance because the uniformly distributed Si3N4 matrix made the fiber bear effectively. After that, the Sc2O3 modified SiOC matrix was filled into inter- and intra-fascicular pores forming interfacial polarization, dipole polarization, multiple reflection and scattering to attenuate the incident electromagnetic wave (EMW). The effective absorption bandwidth (EAB) and the minimum reflection coefficient (RCmin) of N610/Si3N4-SiOC(Sc) composites at the thickness of 2.75 mm reach 3.0 GHz and −42 dB in the X band, respectively. In addition, the EMW absorption performance of the composite is relatively stable with EABmax and RCmin of 3.5 GHz and −41 dB in 4–18 GHz at high temperatures. This work provides a strategy for designing and fabricating OCMC with excellent mechanical properties and EMW absorption properties.

Effect of reactive fumes suppressant DOPO on the chemical composition and performance of asphalt

9,10-Dihydro-9-oxa-10-phosphorophenanthrene-10-oxide (DOPO), recognized for its role as an efficacious fume suppressant, has been shown to mitigate the emission of noxious vapors emanating from asphalt. However, the comprehensive influence of DOPO on the composition and properties of asphalt had remained unexplored. This study embarked on an in-depth examination of the effects of various DOPO dosages on the chemical composition of asphalt, employing hydrogen nuclear magnetic resonance spectroscopy (1H NMR) alongside an exhaustive analysis of asphalt components. Furthermore, the investigation elucidated the consequences of different DOPO dosages on the physical, rheological properties, and aging resistance of asphalt. The results of 1H NMR and component analysis of asphalt disclosed that DOPO engaged in chemical reactions with the unsaturated groups within the asphalt, catalyzing a metamorphosis of saturates into aromatics and resins. Such chemical transformations were instrumental in augmenting the softening point, viscosity, and rutting propensity of the asphalt while imposing a minimal impact on its penetration and ductility. Post exposure to the thin film oven test (TFOT), pressure aging vessel (PAV), and ultraviolet (UV) aging, the DOPO modified asphalt (DMA) exhibited a diminution in the increment of softening point and viscosity aging index relative to the control asphalt. Furthermore, the DMA showcased enhanced retention rates of penetration and ductility, coupled with substantially reduced shifts in complex modulus and phase angle post-aging, underlining its superior aging resistance. Fourier transform infrared spectroscopy analysis revealed a comparatively slower rate of change in carbonyl and sulfoxide groups in DMA after aging, as opposed to the control asphalt. Notably, DMA exhibited enhanced resistance to UV aging relative to TFOT and PAV aging scenarios, a trait attributable to remarkable UV absorption capabilities of DOPO. Fundamentally, DOPO enhanced the high-temperature performance and aging resistance of asphalt while simultaneously diminishing the emission of noxious fumes.

Significantly enhanced high-temperature energy storage performance for polymer composite films with gradient distribution of organic fillers

Film capacitors as one of the most important electronic devices are heading in large capacity, heightened integration and excellent extreme-condition tolerance, which faces the challenges in maintaining outstanding performance under harsh conditions of high temperature and large electric field. Nonetheless, polymer capacitive films, which are renowned for their exceptional thermal stability, experience an escalation in conduction losses at elevated temperatures, resulting in degradation of energy storage performance. This study presents the gradient distribution of organic fillers content in all-organic polymer capacitive films utilizing electrospinning technique, the significantly improved high-temperature energy storage performance has been achieved. Glucose (GLC), a weak polar molecule rich in hydroxyl groups, is blended with the most promising polyetherimide (PEI). Experimental and theoretical calculations confirm that the formed hydrogen bond between GLC and PEI acts as a trapping site for capturing carriers and suppressing conduction losses. Furthermore, the spatial distribution of organic fillers was designed on the basis of direct mixing. The results demonstrate that the gradient composite film introduces interlayer interfacial polarization, while the dielectric mismatch between adjacent layers increases the height of potential barriers for the charge carriers across the interfaces, thereby achieving a synergistic enhancement of dielectric response and insulation strength. The maximum discharge energy density of 6.52 J/cm3 with an efficiency of 85.6 % has been achieved at 150℃ for the modified capacitive films. This work establishes a decoupling relationship between permittivity and electric breakdown strength, offering insights for the advancement of polymer films with outstanding energy storage capabilities in extreme environments.

Research on Microstructure and High-Temperature Performance of Novel Ti65 Titanium Alloy with V-Groove Connection in Laser Additive Manufacturing

Research on Microstructure and High-Temperature Performance of Novel Ti65 Titanium Alloy with V-Groove Connection in Laser Additive Manufacturing

Slurry sprayed glass-ceramic coating for boiler tubes and its high temperature performance

Industrial boilers operate in extreme environments and are prone to degradation caused by high temperature oxidation, corrosion, and erosion. Protective coatings provide boiler components with protection to prolong their operation lifetime. Thus, a glass-ceramic coating has been developed using a slurry spray technique on carbon steel AS/NZS 3678 substrates. Microstructure, mechanical characteristics, and high temperature performance of the coating were investigated. The coating composed of chemically inert oxide ceramics dispersed in a glassy silicate binder matrix. The adhesion strength of the coating was 10.79 ± 0.86 MPa. Coating mass loss after abrasion test was 0.013 % of the tested specimen. The coating withstood at least 75 air quenched thermal shock cycles from 800 °C to the room temperature without any visible spallation and cracks. The coating mostly remained undamaged after cyclic oxidation at 800 °C for 10 cycles. However, minor iron oxide formation was observed, specifically, in relatively thin sections of the coating. The oxidation resistance of the boiler steel has been improved with the developed coating. The linear oxidation rate constant of the boiler steel has been statistically reduced from 6.90 × 10−4 mg cm−2 s−1 to 1.95 × 10−4 mg cm−2 s−1 for coated steel (p = 0.007). The developed slurry spray glass-ceramic coating is a potential candidate for boiler environments.

Effect of heat treatment solid solution temperature on high-temperature performance and diffusion welding tissue of IC10 superalloy

Abstract IC10 superalloys with small pressure and large gaps were welded by TLP diffusion welding. Based on this, the effects of heat treatment on the weld organization and welding performance of IC10 joints were discussed. The results showed that when SBM-3 was used as intermediate solder, the weld structure was similar to that of base metal under the welding process of 1250°C, 0.2 MPa, and 6h. The tensile strength was 133.7 MPa at the temperature of 1100°C. After heat treatment mechanism A, in the joint structure, a larger volume concentration of γ+γ′ phase existed in the weld, smooth transition from base metal to welded joint. Under the heat treatment mechanism A, the tensile strength at 1100°C high temperature can reach 204.6MPa (more than 85% strength of IC10). The appropriate heat treatment mechanism can get small enough micro holes and low enough porosity joints, ensuring the excellent high-temperature mechanical properties of high-temperature alloy.

Investigation and evaluation of high-temperature lead-bismuth eutectic (LBE) corrosion resistance and compression performance of the FeCrAl-based coatings

The high-temperature lead-bismuth eutectic (LBE) corrosion resistance and ring compression performance of the Fe15Cr11Al2Si, Fe15Cr11Al0.5Y, and Fe15Cr11Al2Si0.5Y coatings were investigated. Even if the corrosion test temperature reaches 800 °C, all these coatings can effectively protect the steel cladding tube. After the corrosion test temperature exceeded 660 °C, an obvious Al-rich oxide layer was formed on the surface of the coating, and Al element enrichment occurred at the interface between the coating and the substrate. After the corrosion test at 800 °C, holes appeared in the thick interface layer of the Fe15Cr11Al2Si0.5Y coating. The Fe15Cr11Al2Si coating cracked after the ring compression test with a deformation rate of 3%, and the coating peeled off after the deformation rate reached 5%. When the deformation rate reached 5%, there was still no cracking in the Fe15Cr11Al0.5Y coating. When the deformation rate reached 30%, the coating cracked, but the cracked coating was still tightly bonded with the substrate. The Fe15Cr11Al2Si0.5Y coating has the worst compression performance, even if the deformation rate is 1%, the coating still peels off obviously. The underlying mechanism for the evolution of corrosion resistance and compression performance was discussed.

High-temperature mechanical performances of SiC whisker in-situ toughened 3DN C/SiC countersunk bolts prepared by chemical vapor infiltration

High performance bolts, made of continuous fiber reinforced silicon carbide composites (C/SiC), are crucial to the design and preparation of the hot-end C/SiC components with large complex structures both in aerospace and aeronautical fields. In this work, in-situ grown SiC whiskers were uniformly introduced into the porous laminated 3DN C/SiC countersunk bolt, in order to improve the brittle nature of the 3DN C/SiC threads. Results showed that 7 % increase of tensile strength of the 3DN C/SiC countersunk bolts was achieved via in-situ grown SiC whiskers, and a fatigue life of 106 cycles was also passed. The stud fracture morphologies indicated that the SiC whiskers grew within the woven pores and toughened the layered SiC matrix, so that the load transfer between the layered SiC matrix and carbon fibers was improved under tension. Further high temperature tests showed that the tensile and the shear strengths of the in-situ toughened 3DN C/SiC countersunk bolts were degraded to 64.74 % and 28.83 % at 1000 °C in air respectively. During the thermal exposure, the carbon fibers were largely consumed by oxidation, while the SiC whiskers grew slender and formed a fluffy layer to partially reinforce the SiC matrix. The synergy effect of SiC whiskers and carbon fibers to hinder crack propagation and to toughen the SiC matrix contributes to the above mechanical properties of the bolts.

Study on microstructure and thermal shock resistance of plasma sprayed Cr2O3/8YSZ composite coating

In order to explore the high temperature performance of Cr2O3/8YSZ composite coating, four kinds of Cr2O3/8YSZ composite coatings were prepared on the surface of Q235 steel by using the plasma spraying technology (the content of 8YSZ is 50%, 30%, 20% and 0%, respectively). The morphology of the coating was characterized through thermal field emission scanning electron microscopy, and the distribution of elements in the section of the coating was scanned by using EDS line. The phase composition of the composite coating was analyzed by using X-ray diffractometer, and the surface roughness of the composite coating was measured by using surface profilometer. The microhardness of the coating was measured by using automatic micro-Vickers hardness tester, and the scratch resistance of the coating was compared by using scratch tester. The thermal shock resistance of the coating was tested in Gleeble-3800 thermal physical simulator, and the cross section morphology after thermal shock was observed and analyzed. The results show that when the ratio of Cr2O3 to 8YSZ is 7∶3, the sample coating has good thermal shock resistance due to the deflection effect of 8YSZ on the vertical cracks and the thermal stress release effect of the pores and cracks in the coating.

High Temperature Performance Study of Piperidine-based Ionic Liquids in Sodium Ion Batteries

High Temperature Performance Study of Piperidine-based Ionic Liquids in Sodium Ion Batteries