High Temperature Performance Research Articles

Cycloolefin Copolymers With a Multiply Rigid Structure for Protecting Triplet Exciton From Thermo- and Moisture-Quenching.

Polymeric room temperature phosphorescence (RTP) materials have been well developed and utilized in various fields. However, their fast thermo- and moisture-quenching behavior highly limit their applications in certain harsh environments. Therefore, the preparation of materials with thermo- and moisture-resistant phosphorescence is greatly attractive. Compared with common water-soluble polymers, cycloolefin copolymers (COC) show outstanding hydrophobicity and higher rigidity, even at elevated temperatures, being as a promising candidate to prepare phosphorescence materials with suppressed thermo- and moisture-quenching behavior. Herein, a type of COC bearing hydroxyl, ester, and adamantanyl side groups is synthesized. After dispersing various phosphors into this matrix, the resultant composites exhibit full-color RTP with lifetimes of 249-590 ms. Their luminescence does not show obvious quenching in water, acid, alkalinous, reductive, and oxidative environments. In the presence of both rigid COC matrix and rigid phosphors, the corresponding composite displays high-temperature phosphorescence performance. Even at 378 K, the composite can emit phosphorescence with a lifetime of 40-98 ms. The applications of these COC-based composites for imaging, information encryption, and anti-counterfeiting are thus explored.

High-Temperature Oxidation Performance of HVOF and Plasma Sprayed Ni-20Cr, Ni-20Cr+TiC and Ni-20Cr+TiN coatings on T22 boiler steels

High-Temperature Oxidation Performance of HVOF and Plasma Sprayed Ni-20Cr, Ni-20Cr+TiC and Ni-20Cr+TiN coatings on T22 boiler steels

Linear Dielectric Polymers with Ferroelectric-Like Crystals for High-Temperature Capacitive Energy Storage.

Achieving optimal capacitive energy storage performance necessitates the integration of high energy storage density, typical of ferroelectric dielectrics, with the low polarization loss associated with linear dielectrics. However, combining these characteristics in a single dielectric material is challenging due to the inherent contradictions between the spontaneous polarization of ferroelectric dielectrics and the adaptability of linear dielectrics to changes in the electric field. To address this issue, a linear isotactic sulfonylated polynorbornene dielectric characterized by ferroelectric-like crystals has been developed. The sulfonyl dipoles in the ferroelectric-like crystals are oriented in the same direction, thereby enabling this polymer to exhibit a considerable dielectric constant (7.5) at room temperature. Notably, when the operating temperature surpasses the polymer's glass transition temperature (Tg ≈ 140 °C), its dielectric constant rises to 12 with just minor changes in the dissipation factor. At 150 °C, 90% efficiency of the discharge energy density reaches as high as 6.76 Jcm-1 under a low electric field of 320 MV m-1, which is ten times that of the state-of-the-art, high-temperature, capacitor-grade polyetherimide. The enhancement of high-temperature capacitive performance, achieved by utilizing the crystallinity of isotactic polymers to form a polar structure, presents a new perspective for the design of high-temperature dielectric polymers.

High-entropy engineered BaTiO3-based ceramic capacitors with greatly enhanced high-temperature energy storage performance

Ceramic capacitors with ultrahigh power density are crucial in modern electrical applications, especially under high-temperature conditions. However, the relatively low energy density limits their application scope and hinders device miniaturization and integration. In this work, we present a high-entropy BaTiO3-based relaxor ceramic with outstanding energy storage properties, achieving a substantial recoverable energy density of 10.9 J/cm3 and a superior energy efficiency of 93% at applied electric field of 720 kV/cm. Of particular importance is that the studied high-entropy composition exhibits excellent energy storage performance across a wide temperature range of −50 to 260 °C, with variation below 9%, additionally, it demonstrates great cycling reliability at 450 kV/cm and 200 °C up to 106 cycles. Electrical and in-situ structural characterizations revealed that the high-entropy engineered local structures are highly stable under varying temperature and electric fields, leading to superior energy storage performance. This study provides a good paradigm of the efficacy of the high-entropy engineering for developing high-performance dielectric capacitors.

Efficacy of octadecylamine-functionalized graphene versus graphene nanoplatelets and graphene oxide as asphalt binder modifiers for high-temperature performance

In this work, we comprehensively report on the synthesis of octadecylamine (ODA)-functionalized graphene (G-ODA) and compare its performance to those of graphene nanoplatelets (GNPs) and graphene oxide (GO) as asphalt binder modifiers. An exploration into the mechanisms through which asphalt binder properties are enhanced by each graphene-based material has been conducted, identifying the one that demonstrates superior compatibility with asphalt. The study systematically evaluates the performance of each modifier, analyzing viscosity, rheology, anti-aging properties, morphology, and chemical transformations within asphalt binders. Experimental results indicate that all three graphene-based modifiers enhance the high-temperature performance and aging resistance of the asphalt binder, with GO emerging as the most compatible material, exhibiting superior performance across all investigated responses. The rheological properties results show that GO can improve G*/sin(δ) for the unaged binder by about 120%, followed by G-ODA and GNP. On the contrary, multiple stress creep and recovery (MSCR) results indicate that both GO and GNP efficiently reduce permanent deformation, with reductions in Jnr of about 39% and 34%, respectively while the G-ODA shows a smaller reduction of − 10%. Additionally, GO excels in improving elastic response, showing a substantial increase in percent recovery at 297%, compared to 48.4% with GNP and 28.8% with G-ODA. Fourier-transform infrared spectroscopy (FTIR) analysis establishes the absence of evidence indicating chemical interaction between any of the graphene-based materials and asphalt molecules. This suggests that the improvement is solely attributed to physical interaction, specifically through π-π interaction. On the other hand, AFM phase images indicate that all graphene-based materials can alter the morphology of asphalt binders. They increase the projected surface area of the Peri/Catana phases, which can influence the rheological properties of the binder.

Metallurgical Investigation and Failure Analysis in GTD-111 Stage 2 Buckets From an Industrial F-Class Gas Turbine

Abstract A utility experienced cracking in multiple stage 2 buckets (S2Bs) in a large F-class power generation gas turbine after only 7348 h and 31 starts following a standard repair and rejuvenation heat treatment cycle. The blades were cast from a directionally solidified (DS) superalloy and the cracking was found in the shroud section of the blade in the Z-notch region. A detailed failure investigation was conducted to determine the failure mechanism and most likely contributing factors to root cause in terms of design, operation, fabrication, and metallurgy. Three blades, two with visible cracks and one without cracks, were subjected to nondestructive and destructive evaluation. Methods consisted of visual inspection, three-dimensional scanning, physical measurements, chemical analysis, optical metallography, LED surface topological evaluation, and scanning electron microscopy. The failure mechanism was determined to be due to creep with damage propagating along the grain boundaries in a high stress concentration area. Evaluation of precipitate structure and size also confirmed this area exhibited the highest temperature during operations. High temperature creep testing was also conducted in material from the two different casting houses to confirm metallurgical risk did not have a significant impact on creep performance. An evaluation of the operational profile of an entire fleet of GE 7FA units showed that the failed 7F.03 S2Bs were in the highest operating temperature base loaded units. The findings from this work will help better define key factors that influence the high temperature performance of nickel-base superalloys used in the hot section of industrial power generating turbines.

Physical Properties, Chemical Structure, and Microstructure of Thermoplastic Polyurethane Recycled Material-Modified Asphalt

Firstly, thermoplastic polyurethane recycled material (TPRM) particles were used to prepare modified asphalt. Then, the modified asphalt’s physical properties were investigated. The results show that the TPRM particles improved its high-temperature performance, low-temperature crack resistance, and shear behavior due to its increased cohesion and low-temperature fracture energy levels. Thermal susceptibility was affected by the degree of swelling and dissolution of the TPRM particles, the composition of the asphalt, and the interface effect between the asphalt molecules and both the regular and slender–irregular TPRM particles. The TPRM particles swelled and dissolved after absorbing the light components of asphalt. Changes in the shearing temperature and time made the TPRM particles swell and dissolve more than changes in the activation temperature and time. An increase in the shearing/activation temperature and time increased the hydrogen bond content in the modified asphalt due to the rearrangement of the polyurethane’s molecular structure and the hydrogen bonds formed by the asphaltene and polyurethane molecules. Slender–irregular TPRM and “sea–island” and hilly and gulley structures were found in the modified asphalt matrix.

Metal-organic cage crosslinked nanocomposites with enhanced high-temperature capacitive energy storage performance

Polymer dielectric materials are widely used in electrical and electronic systems, and there have been increasing demands on their dielectric properties at high temperatures. Incorporating inorganic nanoparticles into polymers is an effective approach to improving their dielectric properties. However, the agglomeration of inorganic nanoparticles and the destabilization of the organic-inorganic interface at high temperatures have limited the development of nanocomposites toward large-scale industrial production. In this work, we synthesize metal-organic cage crosslinked nanocomposites by incorporating self-assembled metal-organic cages with amino reaction sites into the polyetherimide matrix. The in-situ crosslinking by self-assembled metal-organic cages not only achieves a homogeneous distribution of inorganic components, but also constructs robust organic-inorganic interfaces, which avoids the interfacial losses of conventional nanocomposites and improves the breakdown strength at elevated temperatures. Ultimately, the developed nanocomposites exhibit exceptionally high energy densities of 7.53 J cm−3 (150 °C) and 4.55 J cm−3 (200 °C) with charge-discharge efficiency of 90%.

Oxidation sequence modulation induced superior high-temperature tribological performance of Ti-Hf-Nb-V refractory high entropy alloy fabricated through directed energy deposition

Oxidation sequence modulation induced superior high-temperature tribological performance of Ti-Hf-Nb-V refractory high entropy alloy fabricated through directed energy deposition

Mechanical and microstructural properties of fiber-reinforced basalt rock cutting waste-based geopolymer composites exposed to high temperatures.

Managing basalt rock cutting waste in an environmentally responsible manner is crucial to mitigate its negative impacts and protect both the environment and human health. Recycling basalt rock cutting waste in geopolymer applications offers multiple environmental, economic, and performance benefits, making it a promising approach for sustainable construction practices. For this purpose, this study concerns about the performance of fiber-reinforced basalt rock-cutting waste-based geopolymer composites at high temperatures up to 1000°C. Geopolymer composites were manufactured by activating basalt rock cutting waste with sodium silicate. Alongside the fiber-free mixtures, fiber-reinforced geopolymer composites incorporating 0.5% and 1.0% basalt or polypropylene fibers by volume were synthesized. These composites underwent thermal curing at 100°C for two distinct durations: 8h and 24h. In addition, the geopolymer composites were subjected to thermal exposure at three different temperatures: 600°C, 800°C, and 1000°C. Changes in the strength and weights of the composites were determined after high-temperature exposure. In addition, XRD and SEM/EDX analyses were performed on the selected composites to investigate the changes in the microstructure of the composites. Thermal curing time and fiber content had significant influence on the high-temperature performance of the geopolymer composites. In this study, geopolymer mortars based on basalt rock cutting waste were successfully developed, demonstrating resistance to elevated temperatures up to 1000°C. No reduction in compressive strength was observed in any of the composites when exposed to 600°C, 800°C, and 1000°C. In fact, an increase in strength was recorded at varying rates, compared to the pre-exposure values.

High-temperature performance of metal/n-Ga2O3/p-diamond heterojunction diode fabricated by ALD method

A metal/n-Ga2O3/p-diamond heterojunction diode with superior high-temperature performance was demonstrated in this work. The p-type diamond was lightly boron doped, and the Ga2O3 film was grown via atomic layer deposition without intentional doping. The forward current density increased with temperature, while the reverse current decreased at elevated temperatures. This behavior was attributed to the distinct carrier ionization dynamics across varying temperature ranges. Under high reverse voltage stress, the reverse current remained relatively stable, with no breakdown occurring up to 498 K. An avalanche breakdown voltage of 186 V at 498 K indicates the diode's robust high-voltage endurance capability. These findings underscore the potential of the metal/n-Ga2O3/p-diamond heterojunction diode for high-temperature and high-voltage applications.

Modification and Characterization for Nickel-Based Alloys used in Ultra-Supercritical Units

As global warming intensifies and the need for renewable energy grows, ultra-supercritical (USC) units have emerged as a key development in coal power technology due to their potential to improve efficiency while reducing emissions. Nickel-based alloys, known for their high-temperature corrosion resistance, oxidation resistance, and high strength, have become one of the most promising materials for USC units. This paper discusses the primary modification methods for nickel-based alloys, including high-entropy alloying and oxide dispersion strengthening techniques, and explores their effectiveness in enhancing the high-temperature performance of these alloys. Advanced characterization techniques were employed to investigate the microstructural evolution and creep behavior of the nickel-based alloys, which provide theoretical references and design ideas in related areas.

Optimal Blend Between Fluorinated Esters and Fluorinated Ether for High-Performance Lithium-Ion Cells at High Voltage.

An experimental investigation is conducted to identify the optimal blend of fluoroethylene carbonate (FEC), 3,3,3-trifluoropropylene carbonate (TFEC), and various fluorinated ethers, including 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), and bis(2,2,2-trifluoroethyl) ether (BTE), to enhance the performances of lithium-ion cells at high voltage. The cell incorporating TTE exhibits a significantly superior capacity for retention after long-term cycling at 4.5 V, which might be attributed to the improved kinetics of lithium ions and the generation of a thin, reliable, and inorganic-rich electrode-electrolyte interface. This enhancement facilitates greater lithium ion mobility within the cell, while effectively suppressing active lithium loss and side reactions between the electrodes and electrolytes at elevated voltages. Furthermore, the cell with TTE demonstrates a superior rate capability and high-temperature performance. As a result of the inherent safety characteristics of these all-fluorinated electrolytes, cells using these formulations show excellent safety properties under typical abuse scenarios. Except at elevated temperatures, none of the cells undergo thermal runaway when subjected to mechanical or electrical abuse, and there are minimal differences in safety performance across the different formulations. Considering electrochemical performance, safety, and cost factors, it can be concluded that TTE might be more optimal to cooperate with FEC and TFEC for high-performance high-voltage cells.

Preparation and Application of Radiation-crosslinked Polypropylene by One-step Process for Corrosion Prevention of High-temperature Pipelines

Using propylene-ethylene block copolymer (PPB) and metallocene polypropylene random (mPPR) as matrix, olefin block copolymer (OBC) and metallocene polyethylene (mPE) as reinforcement, trimethylolpropane trimethacrylate as sensitizer, antioxidant 1010 and dioctadecyl 3,3-Thio-dipropionate as antioxidant, the radiation-crosslinked polypropylene with excellent high-temperature performance was prepared by one-step process and it was used to produce the heat shrinkable tape with three layers structure further. The effect of the formula, the orientation, the crosslinking, the heat treatment and shrink on the crosslinked-polypropylene were studied. The results show that the crosslinked-polypropylene has optimum overall property when the amounts of PPB, mPPR, OBC, and mPE were 50, 10, 15, and 15 phr, respectively. After the orientation in one-step process and the radiation crosslinking with the irradiation dose of 6 Mrad, the tensile strength, the elongation at break, the shrinkage ration, the gel content of the crosslinked-polypropylene reached 33 MPa, 390%, 30%, 51%, respectively. After heat treatment, its mechanical properties further improved and the decrease of its tensile strength and elongation at break did not exceed 15% after thermal ageing at 130 oC for 100 days. Moreover, the corresponding heat shrinkable tapes show outstanding peel strength, impact strength and cathodic disbondment properties in various conditions.

Experimental investigation and molecular dynamics simulations of plasma treatment on the interface properties of carbon fiber-reinforced PI resin composites

ABSTRACT This paper examines surface modification of carbon fibers using low-temperature plasma and investigates the temperature-dependent interfacial properties of high-performance polyimide-based composites. Additionally, the mechanisms by which air and argon plasma treatments enhance the high-temperature interfacial properties of carbon fiber-reinforced polymers (CFRP) are examined. First, the changes in physical morphology and surface structural defects of carbon fibers under different plasma atmospheres are discussed: carbon fibers develop surface protrusions after various plasma treatments, and a grooved morphology forms after argon plasma treatment. The ID/IG ratio (R value) of the carbon fiber surface increased from 1.25 in untreated fibers to 1.37 after air plasma treatment, and further to 1.60 after argon plasma treatment. The short-beam shear strength test results show that at 300°C, the ILSS (interlaminar shear strength) of argon plasma-treated laminates increased from 67.70 MPa to 87.69 MPa, a 29.53% improvement. The ILSS of air plasma-treated laminates reached 81.46 MPa, a 20.33% improvement. Argon plasma-treated laminates showed more stable interlaminar shear performance at high temperatures, maintaining an interfacial retention rate of 85.11% at 300°C. Secondly, the mechanisms by which air and argon plasma modification enhance the high-temperature interface performance of CFRP are as follows: Air treatment, due to the dual effects of chemical bonding and physical etching, allows the laminated plates to exhibit excellent performance at room temperature. However, in high-temperature environments, the chemical bonding effect is easily affected and damaged, significantly reducing the interface retention rate of the laminated plates. The etching effect of argon treatment is quite significant, which means that the improvement effect of argon mainly manifests in the mechanical interlocking action, with the chemical bonding effect being relatively small. The physical effect of mechanical interlocking is less influenced by temperature, thus the high-temperature retention rate of the laminate is relatively high. Furthermore, molecular dynamics models of the interface were built using atomic simulation to explore how plasma modification introduces active groups that enhance the interface at the molecular level. The impact of these modifications on interfacial structure and energy was analyzed using molecular dynamics metrics. Both experimental and molecular dynamics simulation results confirm that plasma treatment has a positive regulatory effect on the interface.

The high value utilization characteristics of coal gangue powder with emulsified asphalt mastic through rheological and viscoelastic damage theory

In order to solve the problems of rutting and early fatigue cracks in emulsified asphalt cold recycled pavement, and the shortage of natural stone resources and new environmental hazards caused by the use of traditional limestone powder filler. In this study, coal gangue powder was added to prepare Emulsified Asphalt Mastic (EAM) to improve the rheological properties and fatigue performance. A series of tests, including frequency scanning, temperature scanning, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Scanning (LAS), and Fourier Transform Infrared spectroscopy (FTIR) were conducted. Through rheology theory, viscoelastic damage theory, the impact of three fillers: Coal Gangue Powder (CGP), Limestone Powder (LP) and Portland Cement (PC), as well as four kinds of Powder-Binder ratios (P/B) (0.6, 0.9, 1.2, 1.5) on the high temperature rheology and medium temperature fatigue performance of EAM was analyzed. The findings reveal that the filler content has a great influence on the proportion of viscoelastic components of EAM in the low frequency domain. The complex shear modulus (G*) and phase angle (δ) of EAM were suitable for Christensen-Anderson-Marasteanu model (CAM) model in the wide frequency domain. Increasing the filler content and Rotating Thin Film Oven Test (RTFOT) aging can improve the high-temperature stability and stress sensitivity of EAM, but it reduced its fatigue resistance. The high temperature performance of EAM containing PC and CGP exhibit superior high-temperature performance compared to LP fillers. Conversely, LP mastic demonstrate superior anti-fatigue performance under actual strain levels in both thin and thick asphalt pavement layers, surpassing the performance of PC mastic and CGP mastic. Therefore, coal gangue powder can be used as a new type of green filler to replace limestone powder. An appropriate amount of incorporation can improve the high temperature stability of the mortar and does not have a huge impact on the fatigue performance. The most suitable range of P/B is identified as 0.6–1.0 when utilizing LP as the filler, 1.2–1.5 when utilizing PC or CGP as the filler.

Enhancement of High-Temperature Thermoelectric Properties in Pd-decorated Bi-Sb-Te System

Bismuth antimony telluride (Bi-Sb-Te)-based alloys remain the dominant choice for near-roomtemperature thermoelectric cooling applications. One of the most studied approaches to improve the thermoelectric performance of Bi-Sb-Te alloys has been a nanostructuring strategy, to suppress the lattice thermal conductivity. This study investigates the impact of incorporating reduced pyrolyzed Pd acetate within a Bi0.5Sb1.5Te3 matrix, building upon recent advancements in nanostructured Bi-Sb-Te alloys. While Pd acetate addition lowers the thermoelectric figure-of-merit (zT) at low temperatures, due to a corresponding increase in carrier concentration, it significantly enhances zT at higher temperatures. Notably, at 473 K, the addition of 0.02 wt.% Pd acetate increased zT by 32% (from 0.41 to 0.54) compared to the pristine sample. Above 423 K, the average zT improved by approximately 21% (from 0.44 to 0.53) in the 0.02 wt.% Pd acetate sample, primarily due to reduced bipolar conduction. Effective Mass (EM) modeling was employed to analyze band parameters. With the addition of Pd acetate, the density-of-states effective mass (md*) generally increased, while non-degenerate mobility (µ0) decreased. At 473 K, the thermoelectric quality factor increased by 42% (from 0.125 to 0.177) with 0.02 wt.% Pd acetate addition, indicating an improved theoretical maximum zT. These findings demonstrate the potential of incorporating Pd acetate for enhancing high-temperature thermoelectric performance in Bi0.5Sb1.5Te3.

Ab initio machine-learning unveils strong anharmonicity in non-Arrhenius self-diffusion of tungsten

The knowledge of diffusion mechanisms in materials is crucial for predicting their high-temperature performance and stability, yet accurately capturing the underlying physics like thermal effects remains challenging. In particular, the origin of the experimentally observed non-Arrhenius diffusion behavior has remained elusive, largely due to the lack of effective computational tools. Here we propose an efficient ab initio framework to compute the Gibbs energy of the transition state in vacancy-mediated diffusion including the relevant thermal excitations at the density-functional-theory level. With the aid of a bespoke machine-learning interatomic potential, the temperature-dependent vacancy formation and migration Gibbs energies of the prototype system body-centered cubic (BCC) tungsten are shown to be strongly affected by anharmonicity. This finding explains the physical origin of the experimentally observed non-Arrhenius behavior of tungsten self-diffusion. A remarkable agreement between the calculated and experimental temperature-dependent self-diffusivity and, in particular, its curvature is revealed. The proposed computational framework is robust and broadly applicable, as evidenced by first tests for a hexagonal close-packed (HCP) multicomponent high-entropy alloy. The successful applications underscore the attainability of an accurate ab initio diffusion database.

Enhancing room and high temperature performance on WC-Co cemented carbide via nitrogen modification

Enhancing room and high temperature performance on WC-Co cemented carbide via nitrogen modification

Molecular simulation of graft-activated crumb rubber modified asphalt: A study on high temperature performance and its interface behavior with aggregate

Molecular simulation of graft-activated crumb rubber modified asphalt: A study on high temperature performance and its interface behavior with aggregate