High Temperature Aging Research Articles

Lithium-ion battery thermal safety evolution during high-temperature nonlinear aging

The thermal safety performance of lithium-ion batteries is significantly affected by high-temperature conditions. This work deeply investigates the evolution and degradation mechanism of thermal safety for lithium-ion batteries during the nonlinear aging process at high temperature. Through a comprehensive analysis from multiple perspectives, it has been revealed that lithium plating and R-H+ reduction are the primary factors contributing to the notable deterioration for battery safety performance during high-temperature aging. Side reactions, such as lithium plating and R-H+ reduction, occurring with aging, not only result in the thickening of the interfacial film but also generate a significant amount of reductive gas. Consequently, these results in a significant increase in cell impedance and a notable decrease in cell thermal stability. These findings offer valuable insights for the development and optimization of safer cell designs.

Enhancing properties of Al-Zn-Mg-Cu alloy through microalloying and heat treatment

This paper aims to understand the influence of microalloying constituents (Ti, Zr, Sr and Sc), and three heat treatment conditions i.e., T6, retrogression and reaging (RRA) and high temperature aging (HTA) on mechanical and thermal characteristics of modified Al-Zn-Mg-Cu-X alloy using microstructural analyses consist of precipitation characteristics, phase fraction and phase morphology. Addition of 0.25 wt % Sc significantly refines the grain structure, reducing the grain size from 62 μm to 34 μm and increasing Al3Zr, Al3(Zr, Ti), and Al3(Sc, Zr) precipitate fraction. After T6 aging, the alloy exhibits primary precipitates of fine η and T phases, accompanied by secondary intermetallics as well as S phases. RRA treatment led to a slightly larger fraction of coarse Zn and Cu-rich phases, while HTA results in larger η, T, and S phases due to high-temperature aging. The addition of Sc reduces the cooling rate by raising the transition temperature to 532 °C with an enthalpy of 22.1 J/g. T6 treatment shows dissolution of most η phases within the matrix, although RRA and HTA exhibit higher enthalpy due to a greater fraction of η phases. The tensile strength of Al-Zn-Mg-Cu-X alloy follows the following sequence: T6 > RRA > HTA > as-cast condition, regardless of micro-alloy additions. Under T6 conditions, Sc added alloy achieves 30 % higher strength, i.e., 575 MPa, than base alloy due to fine dispersoids. RRA treatment enhances elongation without compromising mechanical properties, resulting in a shift from transgranular brittle fracture to intergranular-dominated mix-mode fracture, with the presence of secondary cracking.

Improving the hydrothermal stability of Al-rich Cu-SSZ-13 zeolite via Pr-ion modification.

Al-rich (Si/Al = 4-6) Cu-SSZ-13 has been recognized as one of the potential catalysts to replace the commercial Cu-SSZ-13 (Si/Al = 10-12) towards ammonia-assisted selective catalytic reduction (NH3-SCR). However, poor hydrothermal stability is a great obstacle for Al-rich zeolites to meet the catalytic applications containing water vapor. Herein, we demonstrate that the hydrothermal stability of Al-rich Cu-SSZ-13 can be dramatically enhanced via Pr-ion modification. Particularly, after high-temperature hydrothermal aging (HTA), CuPr1.2-SSZ-13-HTA with an optimal Pr content of 1.2 wt% exhibits a T80 (temperature window of NO conversion above 80%) window of 225-550 °C and a T90 window of 250-350 °C. These values are superior to those of Cu-SSZ-13-HTA (225-450 °C for T80 and no T90 window). The results of X-ray diffraction Rietveld refinement, electron paramagnetic resonance (EPR) and spectral characterization reveal that Pr ions mainly located in the eight-membered rings (8MRs) in SSZ-13 zeolite can inhibit the generation of inactive CuOx during hydrothermal aging. This finding is further supported by density functional theory (DFT) calculations, which suggest that the presence of Pr ions restrains the transformation from Cu2+ ions in 6MRs into CuOx, resulting in enhanced hydrothermal stability. It is also noted that an excessive amount of Pr ions in Cu-SSZ-13 would result in the production of CuOx that causes the decline of catalytic performance. The present work provides a promising strategy for creating a hydrothermally stable Cu-SSZ-13 zeolite catalyst by adding secondary metal ions.

Comparison of elvaloy and styrene-butadiene-styrene added polymer modified bitumen

One of the methods used to produce road pavements resistant to increased traffic volume and harsh environmental conditions is to improve the properties of bituminous binders, such as high temperature resistance and aging resistance, by using various additives. Styrene-Butadiene-Styrene and Elvaloy are two different commercial additives that are frequently used in pavement construction. In this study, the performance of three different B50/70 grade pure bitumens was modified by using Elvaloy at 1.6%, 1.7%, and 1.8%, and five different B50/70 grade pure bitumens were modified using 4.0%, 4.5%, and 5.0% Styrene-Butadiene-Styrene. Penetration, softening point, elastic recovery, flash point, storage stability, dynamic shear rheometer, beam bending rheometer, rotational thin film oven, and pressure aging vessel tests were applied to the binders in accordance with the Polymer Modified Bitumen technical specifications. According to the test results, it was determined that the additive rates for both modifiers are the optimum values in accordance with the specification. The results of the storage stability tests also showed that the non-homogeneous dispersion of the Styrene-Butadiene-Styrene modified binders during mixing had a significant effect on the behaviour of the binder after storage.

Structure evolution of porous alumina during aging process and its support effect on PtSn/Al2O3 catalyzed propane dehydrogenation

Precise control of porous alumina microstructures is always challenging due to the diversity and complexity of the growth process-related alumina crystalline phase and surface properties. In this work, we established a bottom-up synthesis route with a combination of rapid precipitation at high supersaturation and high-temperature aging in terms of enhancing particle aggregation kinetics. Surprisingly, we discovered that there were two distinct growth stages of alumina precursor (ammonium aluminum carbonate hydroxide) during the aging procedure, that is, oriented attachment at the early stage of crystallization and subsequent Oswald ripening. High-temperature aging can effectively strengthen the aggregation kinetics between the particles and produce large mesoporous (∼16 nm) and a remarkable number of defect sites with the exposure of up to 14 % unsaturated pentacoordinate aluminum ions. Owing to the presence of strong metal-support interactions, the alumina-supported PtSn catalyst exhibited excellent catalytic activity in the propane dehydrogenation reaction with propylene formation with 99 % selectivity and superior stability with a low deactivation rate of 0.007 h−1 over 24 h. These results suggested that it was feasible and instructive to achieve precise control of the structure and surface properties of alumina by manipulating the aggregation process of the initial particles during the aging stage.

Cooling efficiency of thermochromic asphalt pavement material and its contribution to field performance enhancement of asphalt mixture

The thermochromic asphalt pavement material (TAPM) has the potential to bilaterally regulate the pavement temperature according to seasonal environment, which is beneficial to heat island effect mitigation and pavement performance enhancement. However, studies on quantifying the cooling efficiency and verifying the field performance of TAPM are still limited. This study aims to more extensively verify the cooling efficiency of TAPM in different climatic regions and to reveal its cooling mechanism in the field. The key thermophysical parameter, solar albedo, of TAPM was back-calculated using an interpolation methodology to match the numerical simulation results with the specimen temperature data monitored experimentally. The cooling efficiency of TAPM in broader climatic regions was demonstrated through the numerical simulation combined with real meteorological conditions. In view of the cooling characteristics of TAPM as well as the temperature dependency attribute of asphalt mixture, various field performance properties of TAPM were characterized. It was found that at a temperature larger than 31 ℃, the solar albedo of TAPM is 0.30, which is six times larger than that of the conventional asphalt pavement material, indicating a strong reflection ability to solar radiation. The average temperature reduction of TAPM compared with the conventional asphalt pavement material in different regions is 6.26 ℃ with a standard deviation of 0.79 ℃, demonstrating the effective, universal and stable cooling effect of TAPM in summer across China. The cooling function of TAPM contributes to the improvement of high-temperature stability, aging resistance and low-temperature cracking performance of asphalt mixture. Therefore, it is necessary to consider the unique cooling function of TAPM for a more objective evaluation of its field performance.

Structural adhesive-loaded fiber membranes with temperature overload reinforcement

A two-step method was utilized to prepare high-performance thermoplastic polyimide (TPI) solutions, which were further spun into nanofibrous membranes by electrostatic spinning and equipped with adhesives for use. The resulting TPI nanofibrous membranes (TPI NFMs) act as both an adhesive carrier and reinforce the bonding effect at high temperatures. At room temperature, the T-type peel strength of the best ratio film was 6.09 N/mm, and the shear strength was 28.19 MPa. After high-temperature aging, the TPI NFMs fill cracks produced by adhesive decomposition and oxidation, enhancing the bonding by compensating for defects. After 0.5 h of aging, the T-type peel strength decreased by 3%, and the shear strength decreased by 10.7%. After 2.5 h of aging, the T-type peel strength decreased by 34.3%, and the shear strength decreased by 32.6%.

Effect of styrene butadiene styrene and desulfurized rubber powder on asphalt modification: Preparation, performance enhancement, mechanism analysis

The aim of this study is to propose a desulfurized rubber powder / styrene butadiene styrene (DRP/SBS) composite modified asphalt technology by combining the advantages of DRP and SBS. This reduces the production cost of modified asphalt and improves the performance of asphalt. In this paper, orthogonal tests were used to optimize preparation process parameters of DRP/SBS composite modified asphalt. And the physicochemical properties, modification mechanism of composite modified asphalt had been thoroughly studied. Subsequently, the results showed that the optimum content of DRP and SBS modifiers are 25 % and 2 %, respectively. The suitable preparation process is to add SBS first, then DRP, while shearing at 5000 r/min for 50 min. In addition, DRP/SBS composite modified asphalt has better high-temperature performance, viscosity-temperature characteristics, aging resistance, and storage stability. Meanwhile, the storage stability of the composite modified asphalt was verified by fluorescence microscopy test. Through the Fourier transform infrared spectroscopy test, it was observed that the composite modified asphalt modification process is a compatible and stable modification of physical and chemical coexistence. Overall, the composite modification method achieves recycling of waste tires while improving pavement performance, thus promoting the sustainability of pavement.

The Influence of High-Temperature Tests on the Resistance to Degradation and Reduction in Strength Properties of Lithium-Containing Ceramics Used as Blanket Materials for Tritium Breeding

Conducting high-temperature tests on ceramics-containing lithium, which are employed as tritium breeding materials, plays a crucial role in comprehending their ability to withstand degradation and maintain their strength properties throughout operation. From the standpoint of fusion research, it is imperative to grasp these phenomena in order to guarantee the safety and effectiveness of reactors. Additionally, these factors could impact the choice of particular materials and designs for blanket materials. The primary objective of this research is to evaluate alterations in the strength characteristics of ceramics-containing lithium when subjected to high-temperature thermal stability tests, while also preserving the hardness stability and resistance to cracking in ceramics subjected to cyclic tests. Lithium-containing ceramics based on lithium titanate (Li2TiO3), lithium orthosilicate (Li4SiO4), and lithium methacyrconate (Li2ZrO3), having a high structural ordering degree and good strength properties, were chosen as objects for assessing resistance to high-temperature degradation. During the studies, it was discovered that the presence of interphase boundaries in the composition of ceramics linked to the development of impurity phases results in crack resistance growth during long-term high-temperature tests simulating the stress effect on the material. At the same time, an assessment of high-temperature aging as a result of modeling destruction processes showed that ceramics based on lithium metazirconate are the most resistant to degradation of strength properties. By simulating high-temperature aging processes, it became feasible to establish connections between structural alterations resulting from the thermal expansion of the crystal lattice and oxygen migration phenomena occurring at elevated temperatures. These factors collectively contribute to a detrimental reduction in the strength properties of ceramics-containing lithium.

Evaluation of the rheological properties and aging resistance of asphalt modified by MDI/TDI polyurethane

The high cost and high dosage of polyurethane (PU) used in asphalt modification limit its application in asphalt pavement construction. To address these problems, two novel PUs were synthesized by the reaction of low-cost polypropylene glycol (PPG-2000) separately with 4,4 - diphenylmethane diisocyanate (MDI) and with toluene diisocyanate (TDI). This study has further optimized the preparation process and analyzed the influence of the PU synthesis materials on the modified asphalt. Dynamic shear rheology, multiple-stress creep recovery, Fourier-transform infrared spectroscopy, and fluorescence microscopy were used to evaluate the rheological properties and aging resistance of modified asphalt. Results show that the PUs synthesized by MDI and TDI significantly improved the high-temperature performance, low-temperature performance, and aging resistance of modified asphalt compared to unmodified asphalt. Asphalt modified with the PU synthesized by MDI had better high-temperature performance, but the low-temperature performance and aging resistance were worse than those for asphalt modified with the PU synthesized by TDI. The results of rheological aging and chemical aging evaluation showed that the PU synthesized by TDI provided better anti-aging performance. The optimum dosages of both PUs were not more than 6%. These PUs reduce the cost of construction engineering and show excellent application prospects in pavement construction. These two PU-modified asphalts can be applied to pavement construction in different regions based on the properties required.

Effect of Ti/Al Ratio on Precipitation Behavior during Aging of Ni-Cr-Co-Based Superalloys

Precipitation behaviors of Ni-Cr-Co-based superalloys with different Ti/Al ratios aged at 750, 800, and 850 °C for up to 10,000 h were investigated using scanning and transmission electron microscopy. The Ti/Al ratio did not significantly affect the diameter of the γ′ phase. However, the volume fraction of the γ′ phase increased with increasing Ti/Al ratios. The η phase was not observed in alloys with a small Ti/Al ratio, whereas it was precipitated after aging at 850 °C for 1000 h in alloys with a Ti/Al ratio greater than 0.80. Higher aging temperatures and higher Ti/Al ratios led to faster η formation kinetics and accelerated the degradation of alloys. It is thought that the increase in hardness with an increase in the Ti/Al ratio is attributed to the effective inhibition of the γ′ phase on dislocation movement due to the increase in the volume fraction of the γ′ phase and an increase in the antiphase boundary (APB) energy.

The effect of high temperature aging on fluorescence properties of Eu3+-doped La2(Zr0.7Ce0.3)2O7

Introduction of luminescent rare earth ions into thermal barrier coatings (TBCs) for the study of TBCs failure mechanism is a very effective non-destructive method. In this paper, Eu3+ ions were doped into La2(Zr0.7Ce0.3)2O7 (LZ7C3) to form LZ7C3:Eu fluorescent material using a high-temperature solid-phase synthesis method. By analyzing the physical structure, fluorescence properties and thermophysical properties of LZ7C3:Eu powders synthesized with different Eu3+ dopant concentrations at different temperatures, we determined that a synthesis temperature of 1400 °C, a dopant concentration of 1 mol% are the optimal synthesis conditions for LZ7C3:Eu. Independent LZ7C3:Eu coating was prepared by atmospheric plasma spraying technology, and high temperature aging test was carried out at 1400 °C. The influence of high temperature aging on the 5D0→7F2 energy level transition peak of Eu3+ in LZ7C3 powder and its coating was examined by microscopic emission spectroscopy. The results show that the peak of the 5D0→7F2 energy level transition is red-shifted, and the peak intensity and the full width at half maxima (FWHM) of the powder decrease gradually with the increase of high temperature aging time. The peak of the 5D0→7F2 energy level transition of the coating exhibits a constantly fluctuating tendency of red-shifting and then blue-shifting, and the peak intensity and the FWHM also continue to decrease. High temperature aging has a negative effect on the fluorescence properties of LZ7C3:Eu materials.

Optimal conditions for beef tenderization through radiofrequency heating with cold air.

High-temperature (15-37°C) aging can shorten the tenderizing time of beef; however, the use of constant temperature heating can lead to microbial spoilage. This study tested radiofrequency (RF) tenderization (RF-T) to find the appropriate conditions for the aging-like effect of beef without microbial spoilage. After subjecting beef to 22h RF-T with four different cooling temperatures (15, 5, -10, and -20°C), the proliferated aerobic bacteria on the surface showed a concentration of 6-6.2logCFU/g at -10 and -20°C, lower than 7-7.5logCFU/g at 15 and 5°C. When beef was treated with 25W/kg RF heating power for 48h RF-T, the estimated reduction rate of the sliced shear force (SSF) and the increase rate of glutamic acid based on the weight before RF-T were 22.6% and 1.51-fold, which were greater than 19.6% and 1.37-fold with 20W/kg, and 11.0% and 1.11-fold with 15W/kg. The optimal specific RF heating power was calculated as 30W/kg from the results' extrapolation. When processed for 48h under optimal conditions (30W/kg specific RF heating power, -20°C cooling air), the tenderization rate and the increased rates of free amino acids based on the weight before RF-T of beef reached over 20% and 1.5-fold with 5.22 log CFU/g aerobic bacteria, which was lesser than the Korean regulation value of 6.7logCFU/g (5×106 CFU/g). Therefore, RF-T could be proposed as a promising high-temperature tenderization method with lowered risk of microbial spoilage. PRACTICAL APPLICATION: We showed that lowering the chamber temperature during RF-T was effective in surface drying and inhibiting aerobic bacteria. RF-T for 24-48h with 30W/kg specific RF heating power had an aging-like effect given tenderization and increase in FAAs. Moreover, by providing the matching circuit and impedance during RF-T, this method could be industrially reproducible.

Ti30Zr10Hf10Ni35Cu15 high-entropy shape memory alloy with tunable transformation temperature and elastocaloric performance by heat treatment

This work investigates the influence of heat treatments on a pseudo-binary Ti30Zr10Hf10Ni35Cu15 high-entropy shape memory alloy. Heat treatments on the alloy resulted in the formation of second phases and thus were able to adjust its transformation temperatures. This phenomenon results from the formation of H-phase and (Zr,Hf)7Cu10 phase during low-temperature and high-temperature aging, respectively. The superelasticity of solution-treated, 500 °C-aged and 700 °C-aged samples was tested under compression, and all samples exhibited nearly 5 % recoverable strain and 15 °C elastocaloric cooling capacity. Further cyclic compression tests confirmed their stability, with up to 75 % of the initial cooling capacity retained after 5000 compression cycles. Due to its high yield strength, the Ti30Zr10Hf10Ni35Cu15 high-entropy shape memory alloy showed great superelasticity and elastocaloric performance at various testing temperatures. Furthermore, with heat treatments, the austenitic transformation finishing temperature (Af) of the alloy was tunable to between −10 °C (furnace-cooled) and 60 °C (700 °C-aged) with promising functional performance. These features expand the application range of TiZrHfNiCu high-entropy shape memory alloys as potential superelastic and elastocaloric materials.

Precipitate composition regulation and corrosion resistance improvement of boron-containing S31254 steels through a pre-aging treatment

Boron (B) at the grain boundary (GB) influences the segregation of Cr and Mo in S31254 super austenitic stainless steels, which inhibits the formation of precipitates. In this work, to make full use of B at the GB, a pre-aging treatment schedule at 300 ℃ for 50 and 150 min was proposed. After pre-aging treatment and high-temperature aging at 950 ℃, B-containing S31254 was used to investigate the effect of heat treatment on the precipitates. Results verified that pre-aging treatment for 50 and 150 min could promote the segregation of B at GB, and the nucleation of precipitates was inhibited during high-temperature aging. Consequently, the B-containing and Mo-rich precipitates were formed at 950 ℃. Especially, pre-aging treatment for 50 min showed the optimum effect on regulating precipitate compositions. B-containing and Mo-rich phase reduced the Cr-depleted region near the precipitates, which could remarkably improve corrosion resistance. Pre-aging treatment and high-temperature aging can regulate precipitate compositions, which can in turn improve corrosion resistance.

Perovskite evolution on La modified Mn1.5Co1.5O4 spinel through thermal ageing with enhanced oxidation activity: Is sintering always an issue?

Non-precious metal oxides have great potential in catalytic deep oxidation of emitted hydrocarbons to help address various environmental pollution concerns. However, sintering issue is a stumbling block in practical application upon long-term high-temperature operation or thermal shock experience. Herein, La was applied to modify Mn1.5Co1.5O4 spinel to get a highly active oxidation catalyst with exceptional stability against high-temperature thermal ageing treatment. With thermal ageing at 750 °C for 100 h, the La modified Mn–Co composite reached 90 % conversion in toluene oxidation at 265 °C under the high WHSV of 120,000 mL g−1 h−1, while this value increased to 312 °C over blank Mn–Co spinel. The addition of La not only inhibited the growth of spinel nanocrystals, but also brought about perovskite formation through sintering, generating perovskite-spinel interfaces, thus enhancing both activity and stability. Meanwhile, the La modified Mn–Co spinel exhibited superior performance in presence of water or sulfur dioxide after thermal ageing treatment. This work offers a versatile strategy to design anti-sintering and active oxidation nanocatalysts based on non-precious metal oxides for industrial applications.

Polyethylene Composite Particles as Novel Water Plugging Agent for High-Temperature and High-Salinity Reservoirs

Water channeling has always been one of the urgent problems during oilfield development. Especially for fractured reservoirs with high temperature, high salinity, and severe heterogeneity (e.g., deep carbonate reservoirs), it is difficult for the existing plugging agents to realize effective water plugging. In this paper, chemically stable polyethylene (PE) was selected as the main component to prepare multiscale PE composite particles that can be easily dispersed in water as a novel water plugging agent for fractured reservoir with high temperature and high salinity. The characteristics of the prepared PE composite particles, including thermal stability, salinity resistance, dispersibility, coalescence properties, and microscopic morphology, were systematically studied. Finally, the plugging performance of the particles was evaluated through visual physical simulation experiments. The prepared PE composite particles can be pulverized to a minimum of 6 μm, and the particle size is controllable within 6 μm to 3 mm by adjusting the pulverization parameters. The PE composite particles are easily dispersed in water by adding the dispersant, which is conducive to injectivity during the field application process. The particle size remains unchanged under the condition of salinity of 0–3.0 × 105 mg/L, which indicates that the prepared particles have good salt-resistant stability. After high-temperature aging, the particles adhere to each other, and the size of the agglomerations reach a size dozens of times larger than the initial size of the particle, which is conducive to effective plugging in fractures. Thermal degradation behavior analysis shows that the PE composite particles could theoretically withstand a temperature of 434.4 °C. It can be seen from the SEM images that after high-temperature melting and kneading with other components, the microstructure changes from a fibrous structure to a dense flake structure. Physical simulation experiments show that the PE composite particles accumulate in fracture after injection and form effective plugging through coalescence and adhesion of the particles, thereby realizing water flow diversion.

Precipitation behaviors of the rapidly-solidified CoCrFeNiTi high-entropy alloy during aging treatment

The precipitation behavior of second phases plays a crucial role in optimizing the microstructure and improving the mechanical properties of precipitation-strengthened high-entropy alloys (HEAs).In this work, the CoCrFeNiTi HEA alloy was fabricated by the laser cladding, and a novel method was proposed to regulate the type, size, and distribution of precipitates in rapidly-solidified CoCrFeNiTi HEA. During the rapid non-equilibrium solidification of laser cladding, the CoCrFeNiTi HEA consisted of FCC phase, Laves phase, and tiny amount of η phase. The 900 ℃ isothermal aging treatment was designed to achieve a fine-distributed η phase with nanometer size. Four types of coherent η phase with different formation mechanisms and morphologies were found. By comparing the aging treatment of 700 ℃ and 1100 ℃, it was revealed that the competition between the continuous precipitation and the discontinuous precipitation played a crucial role in regulating the type and size of the η phase. Low temperature aging facilitated the continuous precipitation of η phases, while high temperature aging favored the discontinuous precipitation. With the 900 ℃ aging, the synergistic relationship between the matrix and the precipitates was optimized. The microhardness and nanohardness of the HEA coating were ∼865 HV and ∼11.2 GPa, respectively, indicating excellent wear resistance capability. This research not only provides insights into the precipitation behavior in rapidly-solidified HEAs but also offers valuable guidelines for designing precipitation-strengthened HEAs with optimized microstructures and superior mechanical properties.

WS2-based inorganic triboelectric nanogenerators with light-enhanced output and excellent anti-aging ability

Conventional triboelectric nanogenerators (TENGs) usually use polymer as friction layers, because polymer usually has large electronegativity differences and reliable frictional recovery properties. In recent years, inorganic material-based TENG has drawn attention due to its much higher resistance to high-temperature aging, light aging, and fatigue resistance than polymer. However, the performance of TENG with aging has not been fully studied. In this work, pure inorganic TENG based on WS2 and ITO glass was prepared, achieving a short-current (ISC) of 0.3 μA and an open voltage (VOC) of 30 V in the dark. Particularly, the current output of the nanogenerator could be enhanced to 0.61 μA under illumination. In addition, accelerated aging experiments indicated that the inorganic nanogenerator had a good improvement in performance degradation compared to most conventional polymeric nanogenerators. Based on this work, WS2-based inorganic TENGs have stability advantages and may be fully used in a wider range of environments.

Ultrasonic‐Assisted Freeze‐Drying for Polyimide/Carboxylated MWCNTs Aerogel Sensor with Excellent Aging Sensing Performance

AbstractAlong with the rapid development of science and technology, the new demand for flexible strain sensors have been put forward in the field of aerospace and other sophisticated exploration areas. Meanwhile, the high temperature generated during the launch of the aerospace aircraft presents new challenges. The existing high temperature resistant sensors are limited in further development by their inherent defects (stability, high processing costs, etc.). A flexible strain sensor with high‐temperature sensing capability is urgently needed. Therefore, the composite polyimide aerogel flexible strain sensor is prepared by ultrasonic‐assisted freeze‐drying method and thermal imidization. Characterizing the structure and sensing performance of the polyimide/carboxylated MWCNTs (PI/CNTs) composite aerogel, the tunneling effect is innovatively introduced to theoretically calculate the parameters in the sensing path. The prepared composite sensor has a high sensitivity (5.34), a fast response time (187 ms), and long‐term cycling stability (1000 cycles). The composite aerogel sensor, which has undergone high temperature aging, still has good sensing performance. It can be used for sensing under extreme conditions, for example, the peripheral electronic devices of aerial probes are used to sense and detect external deformation or withstand pressure conditions.