Enhancing Comprehensive Performance via Capturing and Scattering the Carriers inside PESU-Based Nanocomposite Film Capacitors

Film capacitors have become key electronic components for electrical energy storage installations and high-power electronic systems. Nonetheless, high-temperature and high-electric-field environments would cause a surge of the energy loss, placing a fundamental challenge for film capacitors applied in harsh environments. Here, we constructed a composite film, combining poly(ether sulfone) (PESU) with excellent thermal stability and large-band-gap filler boron nitride nanosheets (BNNSs). The introduction of BNNSs would form deep/shallow traps inside the dielectric polymer matrix, effectively affecting charge migration. Via density functional theory (DFT) calculation, the higher highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the BNNS than the matrix facilitate scattering electrons and attracting holes. The resultant composite obtains the desired discharged energy densities (Ud) of 5.89 and 3.86 J/cm3 accompanied by an efficiency above 90% at 150 and 200 °C, respectively, surpassing those of existing dielectric materials at the high-temperature conditions. The paper provides a promising composite dielectric material for high-performance film capacitors capable of operating in harsh environments.

Tailoring Multiple Strengthening Phases to Achieve Superior High-Temperature Strength in Cast Mg-RE-Ag Alloys

Mg alloys with excellent high-temperature mechanical properties are urgently desired to meet the design requirements of new-generation aircraft. Herein, novel cast Mg-10Gd-2Y-0.4Zn-0.2Ca-0.5Zr-xAg alloys were designed and prepared according to the advantages of multi-component alloying. The SEM and XRD results revealed that the as-cast microstructures contained α-Mg grains, β, and Zr-containing phase. As Ag rose from 0 wt.% to 2.0 wt.%, the grain size was refined from 40.7 μm to 33.5 μm, and the β phase significantly increased. The TEM observations revealed that the nano-scaled γ' phase could be induced to precipitate in the α-Mg matrix by the addition of Ag. The stacking sequence of lamellar γ' phases is ABCA. The multiple strengthening phases, including β phase, γ' phases, and Zr-containing particles, were effectively tailored through alloying and synergistically enhanced the mechanical properties. The ultimate tensile strength increased from 154.0 ± 3.5 MPa to 231.0 ± 4.0 MPa at 548 K when Ag was added from 0 to 2.0 wt.%. Compared to the Ag-free alloy, the as-cast alloy containing 2.0 wt.% Ag exhibited a minor reduction in ultimate tensile strength (7.0 ± 4.0 MPa) from 498 K to 548 K. The excellent high-temperature performance of the newly developed Mg-RE-Ag alloy has great value in promoting the use of Mg alloys in aviation industries.

Study on Thermal Stability and Fatigue Properties of SBS/CNT-Modified Asphalt Sealant

Carbon nanotubes (CNTs) and styrene-butadiene-styrene (SBS) are used as reinforcing modifiers in asphalt sealants due to their excellent properties, which can effectively improve the internal structure of the sealant and enhance its mechanical properties. Based on this background, two SBS/CNT-modified asphalt sealants were identified and selected by the orthogonal experimental method and compared with two commercially available sealants. The softening point, flow value, multi-temperature frequency scan test, and multiple stress creep recovery test were used to study the high-temperature rheological properties and aging resistance of four types of sealants. The overall evaluation shows that the proportion of the sealant compound's preparation material is 1% by weight of CNT doping, 5% by weight of SBS doping, and 5% by weight of furfural-extracted-oil doping. The results show that the addition of SBS and CNTs more significantly improves the fatigue resistance of the sealants. With the CAM model, C1.0S5F5 reflects a better relaxation property, which better avoids secondary cracking after the construction of the sealant. With the Burgers model, C1.0S5F5 shows excellent deformation resistance under heavy traffic conditions. In summary, conventional performance indicators, such as the softening point and flow value of SBS/CNT-modified asphalt sealants, can meet the specification requirements and show good high-temperature stability and anti-aging properties compared to commercially available sealants.

A Facile Method to Fabricate Al2O3-SiO2 Aerogels with Low Shrinkage up to 1200 °C

Monolithic Al₂O₃-SiO₂ composite aerogels were synthesized by using inexpensive aluminum chloride hexahydrate (AlCl₃·6H₂O) and tetraethyl orthosilicate (TEOS). By adjusting the molar ratio of Al and Si, the best ratio of high-temperature resistance was found. The resultant aerogels (Al:Si = 9:1) exhibit high thermal performance, which can be identified by the low linear shrinkage of 5% and high specific surface area (SSA) of 283 m²/g at 1200 °C. Alumina in these aerogels mainly exists in the boehmite phase and gradually transforms into the θ-Al₂O₃ phase in the process of heating to 1200 °C. No α-Al₂O₃ is detected in the heating process. These Al₂O₃-SiO₂ composite aerogels are derived from a simple, low-priced and safe method. With their high thermal performance, these aerogels will have a wide application in high-temperature field.

Effect of Grain Refinement on the Comprehensive Mechanical Performance of W-Cu Composites

W-Cu composites are commonly subjected to coupled multiple fields in service, which imposes high requirements on their overall performance. In this study, the ultrafine-grained W-Cu composite was fabricated using the combination of electroless plating and spark plasma sintering. The wear resistance and high-temperature compressive properties of the ultrafine-grained W-Cu composite were investigated and compared with those of the commercial coarse-grained counterpart. Moreover, the underlying strengthening and wear mechanisms were also discussed. Here we show that the ultrafine-grained W-Cu composite exhibits superior integrated mechanical performance, making it a potential alternative to commercial W-Cu composites.

High-Temperature Resistance of Modified Potassium Magnesium Phosphate Cement

To study the high-temperature mechanical properties of potassium magnesium phosphate cement mortar and the high-temperature resistance of its laminates. Potassium magnesium phosphate cement (MKPC) was prepared by using heavy-burning magnesium oxide and potassium dihydrogen phosphate as the main raw materials, borax as the retarder, and compounded with a certain amount of fly ash and silica fume. The effect of the mass ratio of magnesium to phosphorus (M:P), compounded fly ash and silica fume on the setting time and mechanical properties of MKPC was investigated. Furthermore, based on the better M:P, the compressive strength of MKPC mortar was studied after 3 h of constant temperature at 400 °C, 600 °C, and 800 °C, and the effect of fly ash and silica fume on the high-temperature resistance of MKPC was analyzed. The high-temperature resistance of MKPC was further evaluated by analyzing the temperature variation of potassium magnesium phosphate cement laminate during a constant temperature of 650 °C for 3 h. The results showed that the mechanical properties of potassium magnesium phosphate cement were influenced by different raw material ratios, and the mechanical properties of potassium magnesium phosphate cement were optimal when M:P was 2:1, fly ash was 5% and silica fume was 15%. The internal temperature of MKPC laminate increased slowly with time, and its high-temperature resistance was better.

Substituting Resistance Spot Welding with Flexible Laser Spot Welding to Join Ultra-Thin Foil of Inconel 718 to Thick 410 Steel

This paper investigated various aspects of replacing existing micro-resistance spot welding (micro-RSW) with micro-laser spot welding for joining Inconel 718 thin foils to thick 410 steel stack-up to allow faster, non-contact joining together with flexibility in spot positioning and removal of tip dressing required for RSW electrodes. The joint quality was evaluated based on the mechanical strength, microstructural characteristics and joint strength at elevated temperature as these joints are often used for high-temperature applications. Experimental investigations were performed using micro-RSW and micro-laser spot welding to obtain the 90° peel and lap shear specimens, each comprising four spots. The obtained strength from laser joints was significantly higher than that of micro-RSW joints due to larger weld nugget formation and interface width. The process map for obtaining good quality welds was also identified, and about a 17% reduction in joint strength was obtained when welded specimens were subjected to elevated temperature (i.e., 500 °C) in comparison with room temperature. This reduction was compensated for using the flexibility of laser welding to add two extra spots. The overall performance of the micro-laser spot welds was found to be better than the micro-RSW considering joint strength, flexibility in placing the spots and time to produce the welds.

All-Climate High-Voltage Commercial Lithium-Ion Batteries Based on Propylene Carbonate Electrolytes

Propylene carbonate (PC)-based electrolytes have many attractive advantages over the commercially used ethylene carbonate (EC)-based electrolytes like a wider operating temperature and higher oxidation stability. Therefore, PC-based electrolytes become the potential candidate for lithium-ion batteries with higher energy density, longer lifespan, and better low- and high-temperature performance. In spite of the superiority, PC is incompatible with the graphite anode because PC fails to passivate the graphite anode, leading to severe decomposition and gas evolution, which seriously restrict the development of the PC-based electrolytes. Nevertheless, it is recently found that the usage of diethyl carbonate (DEC) as a cosolvent will greatly improve the anodic tolerance of PC to realize the reversible lithiation/delithiation of the graphite anode in the PC-based electrolyte. It is because DEC induces anions into the solvation shell of Li⁺ to form an anion-induced ion-solvent-coordinated (AI-ISC) structure with higher reduction stability. In this work, we fabricated 4.4 V pouch cells to assess in detail the practical viability of the PC-based electrolyte in a commercial battery system. In comparison to conventionally used EC-based cells, the pouch cells with the PC-based electrolyte exhibit more excellent high-voltage tolerance and electrochemical performance at all temperature ranges (-40 to 85 °C), demonstrating the wide application prospect of the PC-based electrolyte.

Evaluation of High-Temperature and Low-Temperature Performances of Lignin-Waste Engine Oil Modified Asphalt Binder and Its Mixture

This research aims to explore the high-temperature and low-temperature performances of lignin-waste engine oil-modified asphalt binder and its mixture. For this research, the lignin with two contents (4%, 6%) and waste engine oil with two contents (3%, 5%) were adopted to modify the control asphalt binder (PG 58-28). The high-temperature rheological properties of the lignin-waste engine oil-modified asphalt binder were investigated by the viscosity obtained by the Brookfield viscometer and the temperature sweep test by the dynamic shear rheometer. The low-temperature rheological property of the lignin-waste engine oil-modified asphalt binder was evaluated by the stiffness and m-value at two different temperatures (-18 °C, -12 °C) obtained by the bending beam rheometer. The high-temperature and the low-temperature performances of the lignin-waste engine oil-modified asphalt mixture were explored by the rutting test and low-temperature bending beam test. The results displayed that the rotational viscosity and rutting factor improved with the addition of lignin and decreased with the incorporation of waste engine oil. Adding the lignin into the control asphalt binder enhanced the elastic component while adding the waste engine oil lowered the elastic component of the asphalt binder. The stiffness of asphalt binder LO60 could not meet the requirement in the specification, but the waste engine oil made it reach the requirement based on the bending beam rheometer test. The waste engine oil could enhance the low-temperature performance. The dynamic stabilities of LO40- and LO60-modified asphalt mixture increased by about 9.05% and 17.41%, compared to the control mixture, respectively. The maximum tensile strain of LO45 and LO65 increased by 16.39% and 25.28% compared to that of LO40 and LO60, respectively. The high- and low-temperature performances of the lignin-waste engine oil-modified asphalt LO65 was higher than that of the control asphalt. The dynamic stability had a good linear relationship with viscosity, the rutting factor of the unaged at 58 °C, and the rutting factor of the aged at 58 °C, while the maximum tensile strain had a good linear relationship with m-value at -18 °C. This research provides a theoretical basis for the further applications of lignin-waste engine oil-modified asphalt.

Hafnium vs. Zirconium, the Perpetual Battle for Supremacy in Catalytic Olefin Polymerization: A Simple Matter of Electrophilicity?

The performance of C2-symmetric ansa-hafnocene catalysts for isotactic polypropylene typically deteriorates at increasing temperature much faster than that of their zirconium analogues. Herein, we analyze in detail a set of five Hf/Zr metallocene pairs-including some of the latest generation catalysts-at medium- to high-polymerization temperature. Quantitative structure-activity relationship (QSAR) models for stereoselectivity, the ratio allyl/vinyl chain ends, and 2,1/3,1 misinsertions in the polymer indicate a strong dependence of polymerization performance on electrophilicity of the catalyst, which is a function of the ligand framework and the metal center. Based on this insight, the stronger performance decline of hafnocenes is ascribed to electrophilicity-dependent stabilization effects.

High-Temperature Performance Evaluation of Asphaltenes-Modified Asphalt Binders

Asphalt binder comprises four main fractions-asphaltenes (A), saturates (S), aromatics (A), and resins (R)-referred to as "SARA". Asphaltenes plays an important role in determining the linear viscoelastic behavior of asphalt binders. In this research, asphaltenes are added as a distinct modifier to improve the performance properties of asphalt binder. The modified binders are aged using a rolling thin film oven. A dynamic shear rheometer is then used to measure the rheological properties of the binders at high temperatures. Changes in the chemical composition of the modified binders are also studied through the determination of SARA fractions, using precipitation and gravity-driven chromatography methods. The rheological results show that asphaltenes improve the stiffness and elasticity of asphalt binder. It is also shown that the addition of asphaltenes raises the high Performance grade (PG) temperature of the asphalt binder, with every 6% of asphaltenes added resulting in a one-interval increase in high PG temperature grade. SARA analysis shows that the increase in polar fraction content due to the addition of asphaltenes causes the stiffness, elasticity, and viscosity of asphalt binders to increase. The results indicate that asphaltenes are an effective yet inexpensive additive to improve asphalt binder properties at high temperatures.

A High-Temperature Na-Ion Battery: Boosting the Rate Capability and Cycle Life by Structure Engineering

High-temperature sodium ion batteries (SIBs) have drawn significant heed recently for large-scale energy storage. Yet, conventional SIBs are in the depths of inferior charge/discharge efficiency and cyclability at elevated temperatures. Rational structure design is highly desirable. Hence, a 3D hierarchical flower architecture self-assembled by carbon-coated Na₃ V₂ (PO₄ )₃ (NVP) nanosheets (NVP@C-NS-FL) is fabricated via a microwave-assisted glycerol-mediated hydrothermal reaction combined with a post heat-treatment. The growth mechanism of NVP@C-NS-FL is systematically investigated, by forming a microspherical glycerol/polyglycerol-NVP complex initially and then converting into flower-like architecture during the subsequent annealing at a low temperature ramping rate. Benefiting from the integrated structure, fast Na⁺ transportation, and highly effective heat transfer, the as-obtained NVP@C-NS-FL exhibits an excellent high-temperature SIB performance, e.g., 65 mAh g^-1 (100 C) after 1000 cycles under 60 °C. When coupled with NaTi₂ (PO₄ )₃ anode, the full cell can still display superior power capability of 1.4 kW kg^-1 and long-term cyclability (2000 cycles) under 60 °C.

Study on the Effect of Microwave Processing on Asphalt-Rubber

The addition of crumb rubber (CR) into base asphalt plays a critical role in the improvement of the performance of Asphalt-Rubber (AR) binders. However, due to the problems, like high constructing temperature and energy consumption brought by the additional rubber, the use of AR binders could be limited in some areas. During this study, CR is processed by microwave is adopted to reduce the viscosity of the AR binders system, while the CR processed by long screw extrusion also is studied. First, the swelling (the absorption of light component into the CR particle) and dissolution (some molecules of CR dissolving into the base asphalt), both of which determine the improved performance of AR binders, are investigated by fluorescence microscopy and extraction tests. The size of the CR particle after swelling observed by fluorescence microscopy is used to evaluate the swelling rate of CR samples, and the ratio of the weight loss of CR samples after extraction to the original weight is employed to measure the dissolution rate. Then, Brookfield rotational viscometer and storage stability tests are conducted. Last, the rheologic performance, including high and low-temperature performances, is characterized by the dynamic shear rheometer (DSR) and bending beam rheometer (BBR), respectively. The fluorescence microscopy and extraction results show that microwave processing could effectively increase the swelling and dissolving rate, with the figures rising twofold and more than threefold, respectively. The results show that microwave processing could effectively reduce the viscosity of AR binders, with a viscosity decrease of 65% at 190 °C and, at the same time, the high temperature of Performance Grade (PG) decrease from 88 °C to 76 °C. The storage stability could be negatively impacted, but it is slight and the low-temperature performance is improved slightly.

High-Temperature Performance of Polymer-Modified Asphalt Mixes: Preliminary Evaluation of the Usefulness of Standard Technical Index in Polymer-Modified Asphalt

The objectives of this study are to evaluate the high-temperature performance of polymer-modified asphalt and asphalt mixtures, and to investigate if the standard technical indexes are useful in the performance evaluation of the polymer-modified asphalt. There are four typically used polymer-modified asphalt types employed in the study. The standard high-temperature rheological test, such as the temperature sweep test, was used to express the high-temperature performance of the polymer-modified asphalt. Also, considering the non-Newtonian fluid properties of the polymer-modified asphalt, the multiple stress creep recovery (MSCR) and zero-shear viscosity (ZSV) tests were employed for the characterizations. Besides, based on the mixture design of SMA-13, the high temperature of the polymer-modified asphalt mixture was evaluated via Marshall stability and rutting tests. The test results concluded that the ranking of the four kinds of polymer-modified asphalt was different in various laboratory tests. The TB-APAO has the best technical indexes in MSCR and ZSV tests, while the WTR-APAO performed best in the temperature sweep test. In addition, the correlation between the polymer-modified asphalt and the asphalt mixture was very poor. Thus, the present standard technical indexes for the profoundly polymer-modified asphalt mixtures are no longer suitable.

Influence of Binder Property and Mortar Thickness on High-Temperature Performance of Cold Recycled Mixtures with Asphalt Emulsion

Four kinds of cold recycling (CR) mixtures with different asphalt emulsions were studied for their high-temperature performance in both binder properties and internal structures aspects. Digital image processing was introduced to determine the thickness spectrum for the asphalt mortar of the CR mixtures from a mesoscopic perspective. The time–temperature sweep (TTS) test was conducted to obtain the rheological parameters of each corresponding emulsified residue and the permanent deformation performance of each CR mixture was measured by dynamic creep test. A principle component analysis (PCA) was used to compare the typical performance parameters of the CR mixtures and find the factors controlling the rutting resistance of CR mixtures. The results show that the high-temperature performance of the CR mixtures with a modified emulsified asphalt showed improvements relative to the nominal case. Including Marshall stability, several parameters from the rheological properties of binder (G*/sinδ, flow number) and mortar thickness (max, range proportion 0–10 mm) could significantly influence the high-temperature performance and rutting resistance of the CR mixtures.

Performance Evaluation of Asphalt Rubber Mixture with Additives

Crumb rubber, as a recycled material used in asphalt mixture, has gained more attention in recent years due to environmental benefits and the advantages of its pavement, such as excellent resistance to cracking, improved durability, less road maintenance, lower road noise, etc. However, the high-temperature performance of mixture with crumb rubber does not perform well. In order to improve the performance, this paper examined the effect of additives on the laboratory performance of asphalt rubber Stone Matrix Asphalt (AR-SMA) with additives. Three groups of AR-SMA: no additives, Styrene–Butadiene–Styrene (SBS) and Granular Polymer Durable additive (GPDa) were included, with no additives as a control group. Each group was investigated at three asphalt rubber content (ARC): 6.4%, 6.9%, 7.4% with regard to high-temperature and fatigue properties. The results show that with increasing ARC, the high-temperature performance of mixture without additive decreases, and the high-temperature performance increases first and then decreases for SBS and GPDa. Moreover, the rutting resistance of AR-SMA with GPDa at 6.9% ARC performs best. Under the condition of mixtures with appropriate ARC, AR-SMA with GPDa has higher fatigue life and sensitivity to fatigue cracking than the control group. Simultaneously, the fatigue performance of AR-SMA with GPDa is not as significant as that without additive with increasing ARC. In a word, GPDa is a good choice to improve the performance of AR-SMA. However, it should be noted that optimal asphalt content of AR-SMA mixtures with GPDa is higher than that of traditional mixtures.

High-Conductive AZO Nanoparticles Decorated Ni-Rich Cathode Material with Enhanced Electrochemical Performance

A facile solution route was employed for the preparation of an Al doped ZnO (AZO) coating layer, which was composed of many AZO nanoparticles. These nanoparticles have an average particle size of 50 nm and have been successfully decorated on the surface of NCM523. As cathode material for lithium ion batteries, the AZO-decorated NCM523 exhibits superior lithium storage improvements according to good cyclic performance, enhanced rate performance (134.2 mAhg^-1 after 200 cycles at 10 C), and high-temperature performance (148.9 mAhg^-1 at 10 C at 60 °C). Such significant improvement could be attributed to the structural superiority of the AZO decoration on the surface of NCM523, which would stabilize the surface structure of the bulk, suppress the undesirable side reaction at the interface of the electrodes, and lead to the enhancement of the conductivity. The preparation of AZO-decorated NCM523 provides an effective method for the high-performance lithium ion batteries and has a certain reference for other materials.

Nanoscale Porous Lithium Titanate Anode for Superior High Temperature Performance

In this work, nanoscale porous lithium titanate (LTO) anode material was synthesized by using aqueous spray drying method after ball milling. The size of the LTO nanoparticles was optimized to 200 nm because of its considerable moisture absorption levels for stable performance and its cooperation to make good quality electrodes found with testing. The electrochemical performance of the synthesized LTO nanoparticles was found to be very stable at high operating temperature (50 °C) and high current rate (5 C) which was worth noticing than its usual unfavorable behaviors (gas generation and surface phase transitions) at higher temperatures. In the postanalysis on the aged LTO cells, high-resolution-transmission electron microscope (HRTEM) and fast Fourier transform (FFT) measurements reveal that the LTO phase transitions are maintained to very thin surface level (3-5 nm) even after 500 cycles at 50 °C. Moreover, the synthesized LTO material showed stable cycling with a high capacity of 138.74 mA h g(-1) at 1 C rate and 111.53 mA h g(-1) at 5 C rate. Furthermore, high columbic efficiency and excellent capacity retention over 500 cycles at 50 °C was achieved. The enhanced electrochemical properties can be attributed to the increase in surface area and shortened Li(+) diffusion lengths because of the nanoscale primary particles and porous structure of the synthesized LTO particles.