High Temperature Performance Research Articles

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 the temperature range from 25-225°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. 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 3107 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.

Investigation of High-Speed Rubbing Behavior of GH4169 Superalloy with SiC/SiC Composites

The silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC), ceramic matrix composite (CMC) and nickel-based superalloy GH4169 can be utilized in high-temperature applications due to their high-temperature performance. The SiC/SiC composites are commonly used in turbine outer rings, where they encounter friction and wear against the turbine blades. This high-speed rubbing occurs frequently in aircraft engines and steam turbines. To investigate the tribological behavior of these materials, rubbing experiments were conducted between the SiC/SiC and the GH4169 superalloy. The experiments involved varying the blade tip speeds ranging from 100 m/s to 350 m/s and incursion rates from 5 μm/s to 50 μm/s at room temperature. Additionally, experiments were conducted at high temperatures to compare the tribological behavior under ambient conditions. The results indicated that the GH4169 superalloy exhibited abrasive furrow wear during rubbing at both room temperature and high temperature. Furthermore, at elevated temperatures, some of the GH4169 superalloy adhered to the surface of the SiC/SiC. The analysis of the experiments conducted at ambient temperatures revealed that the friction coefficient increased with higher blade tip velocities (100~350 m/s). However, the coefficient was lower at high temperatures compared to room temperature. Furthermore, significant temperature increases were observed during rubbing at room temperature, whereas minimal temperature changes were detected on the rubbing surface at high temperatures.

Influence of Biomass-Modified Asphalt Binder on Rutting Resistance

Biomasses are environmentally friendly additives that lower pollution in pavement engineering because of their biodegradability. On the other hand, to build a safe, long-lasting pavement, rutting prevention is crucial. This study provides a comprehensive review of the efficacy of biomass as recyclable materials in reducing rutting and enhancing characteristics of asphalt mixtures. According to findings, the hydrocarbon polymer properties of lignin and biomass ash improve asphalt binder consistency, hardness, and function at high temperatures. The results showed that biochar, due to its solid shape, enhances the stiffness and viscosity of the mixtures. The high-temperature performance of asphalt binder is improved by bioshell waste, which increases rutting parameters. Thus, biomass like ash, lignin, and biochar can increase asphalt binder rheology and rutting resistance due to chemical forces such as Van der Waals and hydrogen ions. The macroscopic and microscopic investigation also shows higher interaction and better adhesion in bioasphalt. However, asphalt binders containing bio-oil exhibited no unique behaviors due to their lubricant impact. Based on the estimation of the life cycle assessment (LCA), it was determined that biomass utilization has the potential to decrease the cost and CO2 emissions of pavement engineering by as much as 10% and more than three times, respectively. An examination of recyclability revealed that biomass utilization can decrease the requirement for additional stabilizers by as much as 20%.

Sandwich-structured SrTiO3/PEI composite films with high-temperature energy storage performance

Dielectric capacitors are widely used in aerospace and power systems due to their non-polluting, high power density and fast charge/discharge rates. Polyetherimide (PEI) exhibits excellent temperature tolerance, high withstand voltage and low dielectric loss. However, its relatively low dielectric constant restricts its energy storage density. In this paper, a sandwich-structured composite film with the outer layer of pure PEI and the middle layer of strontium titanate (SrTiO3)/PEI is prepared by the solution casting method. At room temperature, the composite film with 5 vol% two-dimensional (2D) SrTiO3 plates achieves an outstanding energy storage density of 19.46 J cm−3 and an ultra-high energy storage efficiency of 97.05% under an electric field of 630 MV m−1. Furthermore, this composite film exhibits a maximum energy storage density of 10.34 J cm−3 and an energy storage efficiency of 88.13% at 150 °C. Combined with finite element simulation results, it confirms that the synergistic effect of 2D SrTiO3 plates and sandwich-structured can effectively hinder the development of electric trees. This work presents a sophisticated approach to design and preparation of dielectric composites suitable for the applications of high-temperature energy storage.

High-Temperature Cyclic Oxidation Behavior and Microstructure Evolution of W- and Ce-Containing 18Cr-Mo Type Ferritic Stainless Steel

Due to the recurrent starting and stopping operations of automobiles during service, their engines’ hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion.

Nano-Additives in Asphalt Binder: Bridging the Gap between Traditional Materials and Modern Requirements

This research delves into the realm of asphalt technology, exploring the potential of nano-additives to enhance traditional asphalt binder properties. Focusing on Nano-Titanium Dioxide (NT), Nano-Aluminum Oxide (NA), and Nano-Silica Oxide (NS), this study investigates the effects of incorporating these nanomaterials at varying dosages, ranging from 0% to 8%, on the asphalt binder’s performance. This study employs a series of experimental tests, including consistency, storage stability, rotational viscosity, mass loss due to aging, and rheological properties, to assess the impact of nano-additives on asphalt binder characteristics. The findings indicate a substantial improvement in the consistency of the asphalt binder with the addition of nanomaterials, particularly NS, which shows a 41% reduction in penetration at an 8% content and a notable increase in the softening point. The storage stability tests reveal that NS-modified asphalt exhibits superior stability compared to NT and NA, with a significantly lower ΔT increase. Furthermore, the investigation into rotational viscosity suggests that NS, despite increasing the binder’s viscosity, does not exceed the AASHTO M320 threshold, ensuring the binder’s workability. Aging tests demonstrate that NT, at lower concentrations, acts as an effective anti-aging agent, whereas NA and NS tend to increase the mass loss, impacting thermal stability. This study concludes that while each nanomaterial uniquely influences the asphalt binder’s properties, NS stands out in terms of enhancing the high-temperature performance and storage stability. Optimal dosages of 6% for NT and NA and 4% for NS are recommended based on the Overall Desirability analysis. This research bridges the gap between traditional asphalt materials and modern requirements, highlighting the transformative impact of nano-additives in advancing asphalt pavement technology.

Investigating the anti-aging properties of asphalt modified with polyphosphoric acid and tire pyrolysis oil

Abstract This research focuses on the aging resistance properties of asphalt, which are crucial for determining the lifespan of asphalt pavement. To combat aging, waste tire pyrolysis oil (TPO) is often added to asphalt, enhancing its resistance to aging but compromising high-temperature performance. This study offered a pioneering solution by integrating TPO with polyphosphoric acid (PPA) to address these issues. In this study, we conducted a series of tests to characterize the properties of PPA/TPO modified asphalt, including temperature sweep and bending beam rheometer tests. The results demonstrated that the presence of PPA in the PPA/TPO modified asphalt could improve its high-temperature performance while maintaining its low-temperature properties. Moreover, PPA in the PPA/TPO modified asphalt enhanced the modified asphalt’s resistance to fatigue and deformation during the aging process, while the presence of TPO effectively reduced the impact of thermo-oxidative aging on the modified asphalt during the aging process. Additionally, physicochemical interactions between the base asphalt and modifiers were observed before and after aging. In summary, this study had offered an innovative method to enhance the anti-aging properties of asphalt, and had provided more options for sustainable, environmentally friendly roads.

High-temperature creep and corrosion behavior of 316LN stainless steel in oxygen-saturated sodium

The high-temperature performance and sodium corrosion of in-core components are the main problems of liquid sodium-cooled reactors, and low-carbon nitrogen-controlled 316 stainless steel (316LN) is the main research and development direction of the main materials for the core of sodium-cooled fast reactors. In this work, the creep behavior of 316LN in oxygen-saturated liquid sodium at high temperatures (650 ℃, 700 ℃ and 750 ℃) was tested and compared with the results of creep tests in air at the same conditions. It is found that the creep life in the sodium environment is reduced by 63.44%, 67.93% and 40.07%, respectively. The specimens in oxygen-saturated sodium exhibit reduction in ductility, selective dissolution as well as oxidative corrosion. The corrosion mechanism of 316LN under external loading in oxygen-saturated sodium is illustrated.

Correlation between high temperature performance of gussasphalt mixture for steel bridge decks and rheology of asphalt mastic

Rutting is a prevalent issue in the Gussasphalt (GA) mixture layer of steel bridge deck pavements. This study aims to investigate the correlation between the rheology of GA mastic and the high-temperature performance of the GA mixture. To achieve this objective, GA mastic underwent temperature and frequency sweep tests, along with multiple stress creep and recovery tests employing a dynamic shear rheometer. Additionally, indentation tests, uniaxial penetration tests, and Lueer fluidity tests were conducted on the GA mixture. The Grey Relational Analysis method was employed to evaluate the relationship between asphalt mastic rheology and the high-temperature deformation resistance of the GA mixture. The findings reveal that the addition of mineral filler enhances the deformation resistance of both GA mastic and the mixture. The percent difference in non-recoverable creep compliance (Jnr-diff) was minimized when the weight ratio of filler to asphalt binder (F/B) was 2.5. Furthermore, increasing the F/B ratio from 2.0 to 3.5 resulted in a more than twofold increase in the GA mixture’s shear strength. Asphalt type emerged as a significant factor affecting the indentation parameter of the GA mixture, with an F-value reaching 8.82 based on ANOVA analysis. The rheological properties of GA mastic exhibited a significant correlation with the high-temperature performance of the mixture. The highest Grey Relational Grade of 0.87 was observed between the non-recoverable creep compliance at a 3.2 kPa stress level (Jnr3.2) and indentation. In future research, greater emphasis can be placed on exploring the micromechanical properties of the GA mastic-aggregate interface.

Exploiting top ductile B2/β layers to in-situ cold-forging Ti–22Al–25Nb alloy manufactured by laser melting deposition

Ti–22Al–25Nb intermetallic alloy is the latest generation of lightweight aerospace material with superior high-temperature performance. In the present study, a novel hybrid 3D-printing technique, point-forging and laser-deposition (PF-LD), was adopted for demonstrating its possibility in the preparation of near-net-shaping Ti–22Al–25Nb component. We innovatively exploited the top ductile B2/β-phase-zone as a natural protective layer, successfully preparing Ti–22Al–25Nb intermetallic parts with relatively larger build-height without initiating any macro-micro cracks. Three groups of control trials were further performed to ascertain the effect of initial laser parameters on microstructural characteristic and mechanical performance. Among three deposition strategies, the sample with intermediate laser scanning rate reached the best combination of ultimate tensile strength (UTS: ∼ 1280.7 MPa) and elongation after failure (EL: ∼ 5.7 %), while superior tensile strength (UTS: ∼ 1314.8 MPa) could be also achieved at the expense of tensile ductility (EL: ∼ 2.4 %). This study not only reveals a new idea to low-temperature forming Ti–22Al–25Nb alloy, but also provides an insight into the relationship between PF-LD processing parameters and mechanical performance.

Design of SBS molecular structure and contribution mechanism from its soft and hard segments to modify asphalt

ABSTRACT The excellent performance of SBS-modified asphalt is attributed to the release of the SBS soft segment (PB segment) and hard segment (PS segment) in the asphalt. The release mechanism of the SBS soft and hard segments was studied using MD simulation and laboratory experiments, and the optimal molecular structure of SBS for asphalt modification was determined. MD simulation results revealed that SBS with a higher PS content exhibited better compatibility with asphalt. The larger and stronger molecular aggregates of the PS segment improved the high-temperature shear resistance of the asphalt but reduced the molecular mobility of the system. Additionally, radial distribution function analysis showed varying degrees of aggregation behaviour of asphaltenes with different segment ratios of polymer modifiers. Laboratory experiments were conducted using synthetically prepared SBS modifiers with specific segment ratios, as well as PB and PS monomer modifiers. Conventional tests and rheological experiments indicated that the PB segment improved the low-temperature performance of the asphalt, while the PS segment enhanced its high-temperature performance. The experimental results of the Cole–Cole plots are consistent with the solubility parameter results. Morphological studies revealed a two-phase continuous structure formed between SBS and asphalt when the SBS segment ratio was approximately 30/70.

Effect of Force and Heat Coupling on Machined Surface Integrity and Fatigue Performance of Superalloy GH4169 Specimens

GH4169 is one of the key materials used to manufacture high-temperature load-bearing parts for aero-engines, and the surface integrity of these parts in service conditions significantly affects their high-temperature fatigue performance. Under a coupling effect of high temperature and alternating load, the evolution process of the machined surface integrity index of superalloy GH4169 specimens was studied, and fatigue performance tests at 20 °C, 450 °C, and 650 °C were carried out to analyze the primary factors affecting the high-temperature fatigue performance of specimens. The results indicated that the surface roughness of specimens remained essentially unchanged. However, the value of surface residual stress decreased significantly, with a release of more than 60% at the highest temperature. At 650 °C, the surface microhardness increased, while the degree of surface plastic deformation decreased under alternating loads. Simultaneously, when the surface roughness was less than Ra 0.4 μm, surface microhardness was the main factor affecting the high-temperature fatigue performance of specimens. The influence of surface microhardness on low-cycle fatigue performance was not consistent with that on high-cycle fatigue performance. The latter increased monotonically, whereas the former initially increased and then decreased with increasing surface microhardness.

The negative effect of V content on high temperature oxidation resistance of austenitic stainless steels at 850 °C

The effect of V on the high-temperature oxidation performance of austenitic stainless steel has been investigated by the constant-temperature oxidation weight gain approach, while the morphology, composition and elemental distribution of the oxide film are further analyzed by scanning electron microscopy and energy dispersive spectrum, transmission electron microscope and X-ray powder diffractometer as well as X-ray photoelectron spectroscopy, revealing the mechanism of the effect of V on the high-temperature oxidation performance of austenitic stainless steel. As a result, the addition of V has a significant adverse effect on the oxidation resistance of steel. Noteworthy, vanadium pentoxide generated during the oxidation process increases the internal stress of the surface oxide layer, reduces the integrity of the oxide layer and promotes oxygen penetration into the matrix. Simultaneously, the Z-phase formed at the grain boundaries of the matrix inhibits the diffusion of Cr ions, resulting in the inability to form an effective protective layer of Cr2O3 oxidation on the surface.

Study on the high-temperature performance and self-healing capability of asphalt modified with pyrolysis oil from waste tires and polyphosphoric acid

Study on the high-temperature performance and self-healing capability of asphalt modified with pyrolysis oil from waste tires and polyphosphoric acid

Enhancing strength and ductility in high Nb-containing TiAl alloy additively manufactured via directed energy deposition

Intermetallic TiAl alloys have found applications in the aerospace and automotive fields. Nevertheless, to satisfy the increasingly complex environmental requirements, these lightweight alloys must be improved particularly in strength and ductility. Additive manufacturing (AM) exhibits a rapid solidification rate and may strengthen intermetallic TiAl alloys. In this study, an additively manufactured (AMed) Ti-48Al-8Nb alloy with fine formability was successfully fabricated by optimizing the power used during directed energy deposition. The preferential crystal plane for the obtained alloy is {111}γ due to its lowest surface energy, and the presence of the thermal gradient during the AM process results in the alloy growing along the building direction. The TiAl alloy AMed at 500W delivers an excellent tensile strength of 880MPa that is 1.71 times higher than that of its as-cast counterpart, as well as elongation of 0.7% at room temperature. The superior properties of this alloy are due to the formation of numerous deformation twins during tensile deformation at room temperature that enables twin intersections to produce high-density nano-twins while contributing to stress release. Moreover, the AMed TiAl alloy exhibits outstanding high-temperature strength retention performance.

Synthesis and high-temperature energy storage performances of fluorinated polyimides

In light of the increasingly stringent requirements for the applications of light-weight flexible high-temperature-resistant dielectric materials in the fields of aerospace, electronics, and electric vehicles, the imperative lies in the development of dielectric materials with high discharged energy density, enduring temperature resistance and high reliability. This work introduced side-chain trifluoromethyl (–CF3) groups into high-temperature engineering polymer polyimides and conducted comprehensive studies on the breakdown and energy storage capabilities. The introduction of bulky –CF3 substituents reduces the intermolecular interactions, increases the free volume, and suppresses the high-temperature leakage conductance loss by decreasing the formation of intermolecular charge transfer complexes between polymer chains. As a result, the fluorinated polyimides (PFI) with lower dielectric constant exhibit enhanced breakdown strengths (730 MV m−1 at 25 °C; 630 MV m−1 at 150 °C), leading to a high discharged energy density of 3.6 J cm−3 (∼1.7 times of pristine polyimides), alongside a charge-discharge energy efficiency of ∼80% at 150 °C. These findings underscore the great potential of PFI for applications in the field of high-temperature energy storage.

(Ag0.80Bi0.04Sr0.04)(Nb1-xTax)O3 ceramics with enhanced energy storage for high-temperature application via synergic optimization

Dielectric capacitors with high power density are essential components in advanced electronic and micro-electronic products. Nevertheless, the limited energy storage density and efficiency, coupled with poor performance at elevated temperatures, severely restrict their usefulness. In this work, Ta was introduced to the (Ag0.80Bi0.04Sr0.04)NbO3 ceramic prepared via the hydrothermal-synthesized powders to improve the room- and high-temperature energy storage performance. A large breakdown strength of 729kV/cm, a high recoverable energy storage density of 8.5J/cm3 and a benign energy efficiency of 75.6% were simultaneously achieved in (Ag0.80Bi0.04Sr0.04)(Nb0.85Ta0.15)O3 ceramics. Moreover, the larger energy storage efficiency (83.5%) at elevated temperatures than room temperature, the benign frequency and cycle stability foreshow great potential in realizing the application of capacitors at high-temperatures.

Application of fume silica nanoparticles to improve high-temperature rheological performance of terminal blend rubberized asphalt

This study aims to evaluate the impact of fume silica nanoparticles (FSNPs) on the high-temperature rheological properties of terminal blend rubberized asphalt (TBRA). In this research, FSNPs were utilized to modify TBRA asphalt with three different CR contents (30%, 40%, 50%). The micro-morphology of FSNPs was observed through Scanning Electron Microscopy (SEM) experiments. The effects of FSNPs on the high-temperature rheological properties of TBRA were assessed using temperature sweep tests, Multiple Stress Creep Recovery (MSCR), and rotational viscosity experiments. Furthermore, the influence of FSNPs on the chemical and thermal properties of TBRA was analyzed through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) experiments. Rheological tests and SEM results indicate that FSNPs can effectively enhance the high-temperature elasticity, fatigue resistance, and deformation resistance of TBRA binders. This improvement is attributed to the unique branched network structure of FSNPs, which plays a pivotal role in enhancing the elasticity within the TBRA asphalt matrix. Additionally, the degradation of TBRA's low-temperature performance due to FSNPs is minimal. Considering the optimal viscosity for FSPN-modified TBRA, recommended ratios are: TB30/6%, TB40/4%, and TB50/2%. FTIR and TGA results demonstrate that the modification of TBRA by FSNPs is primarily physical blending, and the addition of FSNPs enhances the thermal stability of TBRA.

High temperature performance of high magnesium nickel slag based geopolymers with different P/Al molar ratios prepared by acidic activator

This study uses high magnesium nickel slag (HMNS) directly as a raw material, to prepare high-temperature-resistant HMNS silico-aluminophosphate geopolymer (HMNSGP) activated by different types of acid activators including Al(H2PO4)3, H3PO4 and KH2PO4. By using characterization techniques such as XRD, FTIR, SEM-EDS, and MIP, the micro-properties, pore structure, and reaction mechanism of HMNSGP were investigated. The high temperature resistance of HMNSGP was evaluated by comparing compressive experiments before and after high temperature and TG-DSC. The results showed that the best samples were prepared using aluminium dihydrogen phosphate (ADP) at a P/Al molar ratio of 0.6. At room temperature, the main phases geopolymerized of the sample are crystalline products (Newberyite) and amorphous hydrated products (-Si-O-P-O-Si-, -Al-O-P-O-, -Si-O-Al-O-Si- and -P-O-Mg-). At 1200°C, HMNSGP can still maintain its integrity, and its compressive strength can be increased to 48.4MPa. The HMNSGP prepared using H3PO4 has the same hydration products as the optimal samples, but the lower amount of gel phase causes spallation at high temperatures. Besides primary phases geopolymerized with ADP as activator, the KH2PO4 sample includes crystalline products (K-struvite). However, this phase decomposes at 207℃, affecting its high-temperature resistance while a significant volume shrinkage occurs at 1200℃. In summary, using ADP with a P/Al molar ratio of 0.6 can directly prepare HMNS into an environmentally friendly refractory geopolymer material, the compressive strength shows stable growth after being exposed to 1200℃. This results suggested that HMNSGP prepared with ADP can be used for structural applications, laying the foundation for future replacement of refractory cement.

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