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A rheological model was developed to predict the aging behavior, i.e., the increase of viscosity over time, for plastisols containing a fraction of plasticized processed PVC. The model is valid for low-concentration plastisols, composed of a bimodal virgin resin and a monomodal processed PVC powder which is initially plasticized with at least 33 wt% of diisononyl phthalate (DINP). The swelling rate was determined for individual spherical particles of each type and accounts for variations of the transfer surface during diffusion of DINP. The viscosity of this multimodal suspension was subsequently determined according to the Farris approach (Trans Soc Rheol 12:281–301, 1968). Predictions of the model are congruent with experimental data and a subsequent variational study aimed at completing these observations by investigating the effects of parameters that cannot be varied experimentally. Results demonstrate that the aging phenomenon depends on several factors such as amount and initial plasticizer concentration of processed PVC but also initial radius and size distribution as well as shape and deformability of particles. Limitations of the model are also discussed. [ABSTRACT FROM AUTHOR]

In this study, the microstructure evolution and aging behavior of surface-nanocrystallized WE43 Mg alloy induced by ultrasonic shot peening at a cryogenic temperature were examined. The results reveal that the original coarse grains with an average grain size of 46.7 μm were refined to nanocrystalline grains with 31.5 nm in the nanocrystalline region, demonstrating a marked grain refinement effect. After aging treatment, the nanocrystalline region experienced two aging stages. During Stage Ⅰ, there was a rapid increase in hardness, and in Stage Ⅱ, it reached a maximum of 154.2 HV, representing a 105.6% improvement over the solution-treated alloy. Further microstructural characterization indicates that solute segregation initially occurred along the grain boundaries, leading to a rapid increase in hardness during Stage Ⅰ. Subsequently, two types of precipitates were observed both at the grain boundaries and within the grains during Stage Ⅱ, with the combined effects of solute segregation and precipitation contributing to a further increase in hardness.

The primary objective of this study is to clarify the fundamental question of whether, in principle, it is possible to dispense with a prior solution annealing process in favor of a direct aging heat treatment for specimens of maraging stainless steel grade X3NiCoMoTi18‐9‐5 (1.2709) produced by laser powder bed fusion (LPBF). The waiver of a solution annealing process would significantly increase the process efficiency and thus support a sustainable and resource‐friendly production of such components. Therefore, the hardness, microstructure, and the present phases of specimens in as‐built + aged condition (AB + A) and solution‐annealed + aged (SOL + A) are examined during this study. Initially, an extended parameter study is performed using a Renishaw AM 250 LPBF system equipped with a pulsed mode laser system to achieve the highest possible apparent density. As test specimens, small cubes are produced for parameter study and are analyzed for porosity by means of optical microscopy. To investigate the relationship between microstructure and hardness in different material states, one series of specimens is aged directly after LPBF processing in the as‐built state (AB + A). For comparison, the other series was solution annealed at 820 °C for 60 min, quenched in water and then aged (SOL + A). A maximum hardness value of 614 HV1.0 is achieved for specimen aged at 490 °C for 120 min in as built condition (AB + A), while 624 HV1.0 was measured for specimen aged at 490 °C for 180 min in conventionally solution annealed + aged (SOL + A) condition. Significant austenite reversion is not observed at aging temperature of 490 °C in both cases. Aging of specimens at temperatures of 540 and 600 °C resulted in reduction of specimen hardness due to higher percentage of austenite reversion. No significant difference between the hardness values of AB + A and SOL + A specimens is observed. It can therefore be concluded that, in principle, conventional solution annealing and ageing can be dispensed with in favor of direct aging. However, as the results are based on small sized specimens, further investigations into the scalability are needed. [ABSTRACT FROM AUTHOR]

Nitrile Butadiene Rubber (NBR) is widely used as a sealing material due to its excellent mechanical properties and good oil resistance. However, when using NBR material, the seal structure is unable to avoid the negative effects of rubber aging. Hence, the influence of oil and thermal aging on the characteristics of NBR seals was studied by coupling the mechanical behavioral changes with the tribological behavioral changes of NBR in oil and the thermal environment. For this paper, aging testing and compression testing of NBR were carried out. Additionally, friction testing between friction pairs under different aging times was carried out. The surface morphology of the NBR working surface under different aging conditions was also observed. Finally, coefficients of different test conditions were introduced into the finite element model of NBR seals. It can be seen from the results that the elastic modulus increased with the increase in aging time in the thermal oxidative aging testing. The elastic modulus after 7 days of thermal oxidative aging increased by 135.45% compared to the unaged case, and the elastic modulus after 7 days of oil aging increased by 15.03% compared to the unaged case. The compression set rate of NBR increased significantly with the increase in aging time and temperature. The coefficient of friction (COF) between friction pairs increased first and then decreased with the increase in aging time. The maximum contact pressure decreased by 2.43% between the shaft and sealing ring and decreased by 4.01% between the O-ring and groove. The proportion of the effective sealing area decreased by 3.05% between the shaft and sealing ring and decreased by 6.11% between the O-ring and groove. Furthermore, the sealing characteristics between the O-ring and groove were better than those between the shaft and sealing ring. [ABSTRACT FROM AUTHOR]

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The heat-aging process, a practical aging technology that not only improves the comprehensive performance of Al alloys but also reflects the requirements of short processes, has an extremely practical significance. The effects of the heating rate and termination temperature on the "heat-aging" behavior of a spray-deposited AlZnMgCu alloy hot-extruded plate were investigated using hardness, electrical conductivity, room-temperature tensile strength, exfoliation corrosion experiments, and transmission electron microscopy microstructure (TEM) observation. The results show that as the termination temperature increases, the hardness of the spray-deposited AlZnMgCu alloy first increases to a peak and then rapidly decreases, while the electrical conductivity continues to increase. The increase in the heating rate improves the peak hardness corresponding to the termination temperature. The heat treatment process of heating at a speed of 20 °C/h to 200 °C after the spray deposition has similar mechanical and corrosion resistance properties to the RRA process and can effectively reduce the heating time from 40 h to 8 h, thus establishing a heat treatment process for spray-deposited AlZnMgCu alloy extruded plate with high aging efficiency. [ABSTRACT FROM AUTHOR]

VW63Z magnesium alloy, known for its high strength-to-weight ratio and excellent mechanical properties, is a promising candidate for applications in the automotive industries. Among the anti-corrosion technologies for VW63Z alloys, organic electrophoretic coatings have gained significant attention due to their ability to provide a uniform and controlled coating thickness, high coating adhesion, and excellent corrosion protection properties. In this work, to investigate the aging behaviors of an organic electrophoretic coating for magnesium alloys, water absorption kinetics curves of the coatings after immersion in 3.5 wt.% NaCl at 20 °C and 40 °C were measured, and parameters such as the saturated water absorption and saturation time of the free film coatings were fitted to determine the densification evolution of the organic coatings. A tensile test was used to test the tensile strength of the organic coating during service to determine the evolution of the strength and toughness of the organic coating. The evolution of wet adhesion of organic coatings with service time was tested by ASTM D4541-02. The impedance spectra of the organic coatings under the above conditions were detected by EIS, and finally, the failure behavior of the organic coatings under immersion was analyzed. [ABSTRACT FROM AUTHOR]

The aging behavior of microplastics (MPs) in the environment has garnered significant attention, yet the exact aging process undergone by microplastics during advanced oxidation still remains unclear. This study emphasized elucidating the oxidation and dechlorination mechanisms of polyvinyl chloride microplastics (PVC MPs) within the UV-activated sodium percarbonate system (UV/SPC). After 35 h of UV/SPC (0.05 M) treatment, it exhibited effective dechlorination with a Cl− release of 100.62 ± 13.17 mg/L. And this treatment resulted in the fragmentation and release of fragments from the PVC MPs, thereby contributing to their further aging and dechlorination. In addition, an increase in oxygen-containing functional groups was identified. Quenching experiments confirm that · O H and · C O 3 − are the primary active species present in the system. In summary, the aging of PVC MPs results in a process of fragmentation, releasing fragments that are more fragile and susceptible to mineralization compared to the original PVC MPs. The release of chloride ions originates from the mineralization of these fragments released from PVC MPs by · O H and · C O 3 − . This study has provided valuable insights into the aging mechanisms of MPs in practical wastewater treatment. [ABSTRACT FROM AUTHOR]

Maraging steels are widely used in Additive Manufacturing due to their good processability and outstanding combination of strength and toughness. 18Ni300 is one of the most employed maraging steels. However, it contains cobalt, which has recently been strictly regulated due to its environmental and health hazards, having been classified as carcinogenic. Moreover, this steel contains Ti, showing a high affinity for oxygen, leading to high oxide fractions in powder and final parts. In the current work an ultrahigh strength Co and Ti free maraging steel for AM was processed and characterized. The results were then compared to 18Ni300. The novel alloy, processed with Powder Bed Fusion - Laser Beam (PBF-LB) shows hardness, yield strength, and tensile strength of 525 HV1, 1475 MPa, and 1588 MPa, respectively, after solution annealing and aging treatments.

Although previous studies have broadly explored the aging process of styrene-butadiene-styrene (SBS)-modified asphalt, there still is a lack of understanding of the precise evolution patterns of its phase structure during aging, and whether aged SBS-modified asphalt retains its modified properties or reverts to conventional asphalt. To fill these gaps, this paper focused on key performance characteristics that differentiate SBS-modified asphalt from conventional asphalt, including viscosity, elasticity, and toughness properties; evaluated how aging influences mechanical properties; and examined morphological changes at different aging stages. The effective method for phase structure characterization was established. Based on the results, it was found that mechanical property variations, especially in the toughness curve, effectively indicate the phase structure. The fracture strength σB and fracture elongation εB of SBS-modified asphalt after rolling thin-film oven (RTFO) aging for 8 h closely matched those of 70# base asphalt after RTFO aging for 8 h, with values of 1,364.32 and 0.005, compared with 1,421.07 and 0.007, respectively. This curve helps determine whether aged SBS-modified asphalt remains modified or reverts to conventional asphalt. Aging primarily affected instantaneous elastic deformation, and had a minimal impact on delayed elastic deformation. Morphological analysis supported these findings, and showed that SBS polymer degradation precedes significant network disruption, and increased toughness results mainly from SBS polymer presence. [ABSTRACT FROM AUTHOR]

Small lithium-ion (Li-ion) batteries are often used in smart devices. Due to its low battery capacity, the lifespan of the headset needs to be improved by reducing the decay of the Li-ion battery capacity. Here, an electrochemical-thermal coupling model and a capacity fade model based on the pseudo-two-dimensional (P2D) model are established by COMSOL multi-physics field simulation software. The aging behavior of the Li-ion battery during cycling and the effects of different factors on the battery capacity are investigated; the condition of the battery is further predicted. The simulation parameters include charge–discharge rate, initial concentration of lithium ions in the liquid phase, and radius of the anode particles. The results show that the electrolyte diffusion coefficient increases with the increase of temperature in the range of 1000–1600 mol/m3 concentration. However, the initial concentration of 1600 mol/m3 leads to a higher concentration increment (421 mol/m3) during 3000 cycles; it aggravates the concentration polarization. The larger particle radius forms a thicker SEI film. When the radius rises from 2 to 12.5 μm, the thickness and resistance of the SEI film increase to 1136.51 nm and 6.685 m Ω ∙m2, respectively. It consumes more lithium ions and increases the cycle time under the same current. [ABSTRACT FROM AUTHOR]

Glycidyl azide polymer (GAP)-based polyurethane is an ideal elastomeric matrix for high-energy, low-smoke, and insensitive solid propellants. As the skeleton structure of GAP propellants, changes in the structure and properties of GAP elastomers during aging lead to the deterioration of propellant performance (especially in relation to mechanical properties), which causes safety risks. A high-temperature-accelerated aging experiment (70 °C) on a GAP elastomer was conducted. The evolution of the microstructure of the GAP elastomer system was analyzed by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR), and variations in the macroscopic properties were analyzed by the hardness test and the uniaxial tensile test. The experimental results showed that thermal aging of the GAP elastomer is a coupled process of multiple chemical reactions. The azide groups, urethane groups, and ether bonds were the weak links in the network structure, breaking during the aging process, and the crosslinking density rose and then decreased. Macroscopic properties also showed segmented changes. The aging process was divided into three stages: post-curing (stage one); when the crosslinked network began to break (stage two), and when the crosslinked network was destroyed (stage three). Changes in the microstructure and macroscopic properties were consistent. This work is of great significance for exploring the aging mechanism of GAP propellants and extending their storage life. [ABSTRACT FROM AUTHOR]

The loading and unloading elevators are the primary equipment in the refueling system, used for transferring fuel assemblies in the sodium-cooled fast reactors. The guideway friction pairs are the critical components of these elevators in the refueling system. With the excellent hardness and wear resistance in air, nitrided W18Cr4V steel is a promising material for the guideway friction pairs. In order to assess the feasibility of using nitrided W18Cr4V steel, it is essential to understand the aging behavior of nitrided W18Cr4V steel in high-temperature sodium. Aging tests were conducted on nitrided W18Cr4V steel in sodium and in argon environments at various temperatures for different exposure times. The results showed that the nitrogen atoms in the nitrided layer exhibited bidirectional diffusion behavior in the sodium or argon environment at 540 °C. Compared to the argon environment, cracks formed within the nitrided layer and the diffusion of nitrogen into the sodium was accelerated in the nitrided layer. As a significant number of nitrogen atoms had diffused into the sodium, there was little difference in the hardness between nitrided W18Cr4V steel and non-nitrided W18Cr4V steel after long-term exposure to 540 °C sodium. [ABSTRACT FROM AUTHOR]

Aging treatments have been widely utilized for enhancing the mechanical properties of many materials, such as Al–Cu alloys. In conventional aging treatments, there is a trade-off between the aging conditions (e.g., aging times and temperatures) and the mechanical properties (e.g., hardness and strength). There is usually compensation in the aging treatments, such as deteriorated hardness of the alloys, when tuning the aging conditions. The ultrasound-promoted aging treatments were conducted in this study to solve the aforementioned conventional difficulties since it is believed that the ultrasound could accelerate the diffusion of the atoms and thus shorten the aging time while keeping the aging temperature low. The Al-4 wt.% Cu alloys were utilized for the verification of the influence of the ultrasound on the mechanical properties of the alloys since the Al-4 wt.% Cu alloys have been widely studied. It was found that with the promotion of the ultrasound, the micro Vickers hardness of the alloys could be enhanced. On the other hand, the alternations of strength and elongation by applying an ultrasound were limited. It is therefore concluded that the ultrasound could have certain positive effects on the enhancement of the alloy properties, such as micro Vickers hardness.

To explore the performance evolution mechanism of SBS-modified bitumen (SMB) during construction and service, the chemical structure, molecular weight and properties of styrene–butadiene–styrene triblock copolymer (SBS) and SMB under multiple aging levels were assessed via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and a dynamic shear rheometer (DSR). The results indicate that the polybutadiene segments in SBS are susceptible to oxidative degradation, and the molecular weight of SBS decreases rapidly during the aging process. The complex modulus and temperature sensitivity of SMB show relatively small changes during the early aging stage, which is mainly attributed to the impact of SBS oxidative degradation. While its temperature sensitivity decreases sharply after double PAV aging, it means the influence of asphalt aging on its performance is dominant. And there is a significant difference in the effect of aging on the creep recovery behavior of SMB under high and low shear stresses. The percentage recovery (R) of SMB decreases and then increases under low shear stress as aging progresses. While the value R of SMB increases gradually under high shear stress with the extension of aging. Meanwhile, the viscoelastic properties of SMB have gradually transformed to those of aged matrix asphalt after serious aging, which is also confirmed by the gradual destruction and degradation of the SBS cross-linked network in the binder from a fluorescence micrograph. This research will help to understand the performance failure mechanism of SMB during service, providing a theoretical reference for the selection of maintenance and renovation opportunities during the service process of SBS-modified asphalt pavement, as well as the avenue to achieve high-performance recycling. [ABSTRACT FROM AUTHOR]

Microstructure evolution and mechanical properties of the aging treated AlN/AZ91 composites were systematically investigated by optical microscopy (OM), high resolution scanning electron microscopy (HRSEM) with an energy dispersive spectrum (EDS), and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The results show that the higher fracture elongation (14 ± 1%) and ultimate tensile strength (275 ± 6 MPa) were simultaneously obtained in the peak-aged AlN/AZ91 composites. Comparied with AZ91 matrix alloy, the strength was increased by about 44% and the elongation was approximately five times higher, which mainly attributed to the precipitation of nano-sized γ-Mg17Al12 phase and the activation of non-basal slip systems induced by in-situ AlN particles at room temperature. However, the in-situ formation of AlN reinforcements consumed part of Al element in the matrix alloy, which resulted into the volume fraction decreasing of γ-Mg17Al12 precipitates, and then the age hardening and strengthening efficiency were reduced in the AlN/AZ91 composites. On the other hand, the mismatch of thermal expansion coefficient between AlN particles and AZ91 matrix generated high density dislocations around AlN particles, which promoted the precipitation of γ-Mg17Al12 phase, and then the peak aging time and temperature were decreased.

Hydrogen is recognized as a significant potential energy source and energy carrier for the future. On the one hand, storing hydrogen is a challenging task due to its low volumetric density, on the other hand, a particular type of hydrogen in the form of a liquid can be used to store large quantities of hydrogen at ambient conditions in thermoplastic tanks. But storing hydrogen in this form for a long time in polymer tanks affects the physical and chemical properties of the liner. In the current automotive industry, high-density polyethylene (HDPE) has already been used in existing fuel tank applications. However long-term exposure to fuels leads to the permeation of hydrocarbons into the polymers, resulting in a loss of mechanical properties and reducing the efficiency of fuel cells (FC) in automotive applications. Additionally, facing material shortages and a limited supply of resin leads to an increase in the cost of the material. Therefore, an alternative material is being searched for, especially for hydrogen fuel tank applications. In this study, two semi-crystalline thermoplastics, HDPE and polyketone (POK), were compared, which were exposed to a selected liquid organic hydrogen carrier (LOHC) at 25 °C and 60 °C for up to 500 h in an enclosed chamber, to measure their fuel up-take. A short analysis was carried out using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and mechanical testing to understand the influence of the LOHC on the polymer over time. Fuel sorption and tensile properties showed a plasticizing effect on HDPE. The material degradation was more pronounced for the aged samples of HDPE in comparison to POK. As expected, thermal aging was increased at 60 °C. The fuel absorption of POK was lower compared to HDPE. A slight increase in crystallinity was observed in POK due to the aging process that led to changes in mechanical properties. Both HDPE and POK samples did not show any chemical changes during the aging process in the oven at 25 °C and 60 °C. [ABSTRACT FROM AUTHOR]

The present work investigates the transformation kinetics of silicon carbide reinforced Al–Zn–Mg–Cu alloy composite through thermal diffusion activation energy (TDAE). Alloy and composite were casted through stir casting process with varying weight percent (0, 5, 10, 15, 20 wt.%) of SiCp. To evaluate the thermal diffusion activation energy (TDAE) and precipitation sequence, differential scanning calorimetry (DSC) was carried out with varying heating rate. Hardness measurement of as cast specimen showed increased hardness with increasing the wt.% of SiCp. Vicker's micro hardness test was used to investigate the aging behavior of alloy and composite. Investigation reveals that SiCp does not change in precipitation sequences but alter the aging kinetics. Microstructural features reveal the dispersion of SiCp in the AA7075 matrix. HRTEM morphology study reveals presence of precipitates inside the composite. [ABSTRACT FROM AUTHOR]

The goal of this paper is to analyze the aging behavior and the mechanism evolution of nano-Al2O3 (NA)-reinforced styrene-butadiene-styrene (SBS) asphalt under different thermal-oxidative aging conditions. First, NA/SBS-modified asphalt and SBS-modified asphalt with different aging levels were prepared. Second, the viscosity and high temperature rheological performance of the specimens were tested and the property-related aging indexes were calculated and compared. Third, a Fourier transform infrared (FTIR) test of the specimen was conducted and the chemical group-related aging indexes were calculated and analyzed. Fourth, gel permeation chromatography (GPC) was used to analyze the molecular weight of the specimens under different aging levels. Then, an atomic force microscope (AFM) was adopted to analyze the microsurface morphology of different specimens. Finally, correlation analysis between property-related indexes and chemical group indexes was conducted. The results show that NA can enhance the thermal-oxidative aging resistance of SBS asphalt. NA can inhibit the increase in sulfoxide groups and the degradation of the SBS polymer with the increase in aging. NA can slow down the formation of large molecule during the aging process. The degree of change in both the bee structures and micromorphological roughness of NA/SBS asphalt is lower than that of SBS asphalt under different aging levels. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) inevitably undergo multiple aging processes during their life cycle in the environment. However, the information regarding the mechanical fragmentation behavior of MPs remained unclear, including the changes in the intrinsic properties of aged MPs, the measurement of aging degree, the underlying mechanism, and the interaction with heavy metals. Here, MPs (PS, PP, PET) were aged by crushing (-CR) and ball-milling (-BM) to simulate mild and severe mechanical fragmentation, respectively. Our results indicated that mechanical fragmentation significantly affected the morphology of MPs. The aging degree of MP-BM was deeper compared to MP-CR owing to smaller particle size, larger specific surface area, poorer heat resistance, better hydrophilicity, and richer oxygen-containing functional groups. The carbonyl index (CI) and O/C ratio were used to measure the aging degree of the two mechanical aging treatments. Besides, the mechanism was proposed and the discrepancy between the two treatments was elaborated from three aspects including the excitation energy source, reaction interface, and reaction dynamics. Furthermore, the extrinsic properties of MPs altered with the increase of aging degree; specifically, the adsorption capacities of heavy metals were enhanced. Meanwhile, it was unveiled that the CI value and O/C ratio played a vital role in estimating the adsorption ability of heavy metals. The findings not only reveal the mechanical fragmentation behavior of MPs but also provide new insights into the assessment of the potential risks of the aged MPs via chemical indexes. [ABSTRACT FROM AUTHOR]

The aging behavior and degradation mechanism of fluoroelastomers (FKM) after exposure to thermal air, commercial lubricating oil, and the corresponding base oil at elevated temperatures were investigated. The FKMs immersed in oil and exposed to air are denoted by FKM‐O and FKM‐A, respectively. The crosslinking densities of the samples were determined by equilibrium swelling and dynamic mechanical analyses, and the results were different. Compared to the performances of FKM‐A, noticeable changes in the mechanical and swelling performances of FKM‐O were observed, attributed to the severe deterioration induced by both the lubricating oil and the high‐temperature. The FTIR results revealed that the dehydrofluorination induced by the oil caused the fracture of the CF bonds, and the degradation of the oil itself exerted negative impacts on the properties of the FKM. The findings of this study will facilitate the development of FKMs with degradation‐resistant properties for various applications. [ABSTRACT FROM AUTHOR]

It is well known that the development of lightweight alloys with improved comprehensive performance and application value are the future development directions for the ultra-high-strength 7xxx series Al-Zn-Mg-Cu alloys used in the aircraft field. As the lightest metal element in nature, lithium (Li) has outstanding advantages in reducing the density and increasing the elastic modulus in aluminum alloys, so Al-Zn-Mg-Cu alloys containing Li have gained widespread attention. Furthermore, since the Al-Zn-Mg-Cu alloy is usually strengthened by aging treatment, it is crucial to understand how Li addition affects its aging precipitation process. As such, in this article, the effects and mechanism of Li on the aging precipitation behavior and the impact of Li content on the aging precipitation phase of Al-Zn-Mg-Cu alloys are briefly reviewed, and the influence of Li on the service properties, including mechanical properties, wear resistance, and fatigue resistance, of Al-Zn-Mg-Cu alloys are explained. In addition, the corresponding development prospects and challenges of the Al-Zn-Mg-Cu-Li alloy are also proposed. This review is helpful to further understand the role of Li in Al-Zn-Mg-Cu alloys and provides a reference for the development of high-strength aluminum alloys containing Li with good comprehensive properties. [ABSTRACT FROM AUTHOR]

Microstructure evolution and mechanical properties of the aging treated AlN/AZ91 composites were systematically investigated by optical microscopy (OM), high resolution scanning electron microscopy (HRSEM) with an energy dispersive spectrum (EDS), and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The results show that the higher fracture elongation (14 ± 1%) and ultimate tensile strength (275 ± 6 MPa) were simultaneously obtained in the peak-aged AlN/AZ91 composites. Comparied with AZ91 matrix alloy, the strength was increased by about 44% and the elongation was approximately five times higher, which mainly attributed to the precipitation of nano-sized γ-Mg 17 Al 12 phase and the activation of non-basal slip systems induced by in-situ AlN particles at room temperature. However, the in-situ formation of AlN reinforcements consumed part of Al element in the matrix alloy, which resulted into the volume fraction decreasing of γ-Mg 17 Al 12 precipitates, and then the age hardening and strengthening efficiency were reduced in the AlN/AZ91 composites. On the other hand, the mismatch of thermal expansion coefficient between AlN particles and AZ91 matrix generated high density dislocations around AlN particles, which promoted the precipitation of γ-Mg 17 Al 12 phase, and then the peak aging time and temperature were decreased. [ABSTRACT FROM AUTHOR]

The aging behavior and degradation mechanism of nitrile rubber (NBR) under free and compression states were investigated in simulated air and hydraulic oil environments at various elevated temperatures. The variations in the crosslinking density, volatile components and the chemical structure of NBR during aging were studied using equilibrium swelling testing and dynamic mechanical analysis (DMA), pyrolysis‐gas chromatography–mass spectrometry and attenuated total reflection‐Fourier transform infrared spectroscopy. The migration of additives in different media and the crosslinking density of NBR aged in different conditions were compared. The tensile strength, DMA, and thermogravimetric analysis results were consistent with the changes in the crosslinking density of NBR and the migration of additives. Four effects of the simulated hydraulic system on the thermal aging of NBR were examined. Both the compression stress and the oil medium slowed the aging of NBR. The results can provide new insights into the use of NBR products in lubricating oil environments and NBR lifespan prediction in hydraulic working conditions. [ABSTRACT FROM AUTHOR]

The loading and unloading elevators are the primary equipment in the refueling system, used for transferring fuel assemblies in the sodium-cooled fast reactors. The guideway friction pairs are the critical components of these elevators in the refueling system. With the excellent hardness and wear resistance in air, nitrided W18Cr4V steel is a promising material for the guideway friction pairs. In order to assess the feasibility of using nitrided W18Cr4V steel, it is essential to understand the aging behavior of nitrided W18Cr4V steel in high-temperature sodium. Aging tests were conducted on nitrided W18Cr4V steel in sodium and in argon environments at various temperatures for different exposure times. The results showed that the nitrogen atoms in the nitrided layer exhibited bidirectional diffusion behavior in the sodium or argon environment at 540 °C. Compared to the argon environment, cracks formed within the nitrided layer and the diffusion of nitrogen into the sodium was accelerated in the nitrided layer. As a significant number of nitrogen atoms had diffused into the sodium, there was little difference in the hardness between nitrided W18Cr4V steel and non-nitrided W18Cr4V steel after long-term exposure to 540 °C sodium.

To study the creep and aging behavior under the combined effect of temperature, humidity and static load, polyurethane adhesive was selected to make butt joints. The creep properties of the joint were analyzed experimentally under different static loads in hygrothermal environment. At the same time, an aging test under the combined effect of temperature, humidity and static load was carried out, and the variation law of the residual strength of the joint with the load and loading time was obtained. The complex fracture behavior of polyurethane adhesive joints was studied from macro to microscale. The results show that the hygrothermal environment had a significant effect on the creep properties of polyurethane adhesive joints. The creep strain rate of the joint was significantly higher, and the failure fracture time was shorter in the high temperature and humidity environment. When the temperature, humidity and static load were coupled, the joint failure strength decreased with time. With increasing load, the decline rate of the failure strength increased significantly. The interface failure of the joints and the hydrolysis reaction of the polyurethane adhesive were the main reasons for reducing the failure strength. [ABSTRACT FROM AUTHOR]

To explore the performance evolution mechanism of SBS-modified bitumen (SMB) during construction and service, the chemical structure, molecular weight and properties of styrene–butadiene–styrene triblock copolymer (SBS) and SMB under multiple aging levels were assessed via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and a dynamic shear rheometer (DSR). The results indicate that the polybutadiene segments in SBS are susceptible to oxidative degradation, and the molecular weight of SBS decreases rapidly during the aging process. The complex modulus and temperature sensitivity of SMB show relatively small changes during the early aging stage, which is mainly attributed to the impact of SBS oxidative degradation. While its temperature sensitivity decreases sharply after double PAV aging, it means the influence of asphalt aging on its performance is dominant. And there is a significant difference in the effect of aging on the creep recovery behavior of SMB under high and low shear stresses. The percentage recovery (R) of SMB decreases and then increases under low shear stress as aging progresses. While the value R of SMB increases gradually under high shear stress with the extension of aging. Meanwhile, the viscoelastic properties of SMB have gradually transformed to those of aged matrix asphalt after serious aging, which is also confirmed by the gradual destruction and degradation of the SBS cross-linked network in the binder from a fluorescence micrograph. This research will help to understand the performance failure mechanism of SMB during service, providing a theoretical reference for the selection of maintenance and renovation opportunities during the service process of SBS-modified asphalt pavement, as well as the avenue to achieve high-performance recycling.

Aluminum matrix composites have been widely used in aerospace and automotive fields due to their excellent physical properties. Cryogenic treatment was successfully adopted to improve the performance of aluminum alloy components, while its effect and mechanism on the aluminum matrix composite remained unclear. In this work, the effects of cryogenic treatment on the microstructure evolution and mechanical properties of 15%SiCp/2009 aluminum matrix composites were systematically investigated by means of Thermoelectric Power (TEP), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The results showed that TEP measurement can be an effective method for evaluating the precipitation characteristics of 15%SiCp/2009 aluminum matrix composites during aging. The addition of cryogenic treatment after solution and before aging treatment promoted the precipitation from the beginning stage of aging. Furthermore, the aging time for the maximum precipitation of the θ″ phase was about 4 h advanced, as the conduction of cryogenic treatment accelerates the aging kinetics. This was attributed to the great difference in the linear expansion coefficient between the aluminum alloy matrix and SiC-reinforced particles, which could induce high internal stress in their boundaries for precipitation. Moreover, the lattice contraction of the aluminum alloy matrix during cryogenic treatment led to the increase in dislocation density and micro defects near the boundaries, thus providing more nucleation sites for precipitation during the aging treatment. After undergoing artificial aging treatment for 20 h, the increase in dispersive, distributed precipitates after cryogenic treatment improved the hardness and yield strength by 4% and 16 MPa, respectively. [ABSTRACT FROM AUTHOR]

The strength-ductility trade-off severely limits the extensive application of particle-reinforced aluminum matrix composites mainly owing to the critical issues of local particle agglomeration and poor interfacial characteristics. The present work concentrates on these intractable puzzles and proposes Mg-Ag microalloying TiB2/Al-4.5Cu composites fabricated by an optimized salt-metal reaction method and multistage heat treatment. The resulting microstructure evidence that this new tactic synergistically ameliorates the detrimental agglomeration of TiB2 particles by Mg and Ag doped at the TiB2/α-Al interface， meanwhile promoting the formation of nanosized Ω-Al2Cu and σ-Al5Cu6Mg2 phases. The mechanical property experimental results indicate that the Mg-Ag microalloyed TiB2/Al-4.5Cu composites exhibit an accredited combination of the tensile strength (ultimate tensile strength is 496.3 ± 15.0 MPa) and ductility (uniform elongation is 12.8 ± 1.4 %). We emphasize the reciprocal effect between TiB2 particles and the precipitated phase associated with unrelaxed misfit strains. Close attention is also paid to the interface binding characteristics and semi-coherent interphase boundary to evaluate their contribution to the ductility. The microalloying strategy can potentially be applied to many other metal matrix composites and boost analogous approaches for designing ultrahigh yet ductile materials for technological applications.

High-strength Al-Cu-Mg alloys are good matrix candidates for fabricating strong and tough Al matrix composites reinforced with carbon nanotubes (CNTs). In this study, an element mechanical alloying method was used to achieve homogeneous CNT dispersion in hard Al-Cu-Mg matrix. A comprehensive transmission electron microscopy study was applied on peak-aged CNTs/Al-Cu-Mg composites and referential Al-Cu-Mg alloy. It was found that the ex-situ CNTs increased the dislocation density and hindered the recrystallization of the Al-Cu-Mg matrix. Thus, larger local stress and strain were detected in CNTs/Al-Cu-Mg composites. The precipitation in CNTs/Al-Cu-Mg composites was accelerated, which brought extra 12 % improvement to tensile yield strength of the composite. The distribution of precipitates in CNTs/Al-Cu-Mg composites were nonuniform due to the element mechanical alloying process, which was probably beneficial to the high ductility of the CNTs/Al-Cu-Mg composite. With the synergetic strengthening effect of CNTs and fine precipitates, CNTs/Al-Cu-Mg composites exhibited well-balanced strength and ductility. [ABSTRACT FROM AUTHOR]

The effect of Equal channel angular pressing (ECAP) deformation on the microstructure, mechanical properties, and aging behavior of solution treated Ti–1300 alloy was investigated. The results show that the grains are not broken during ECAP deformation due to coordination of grain rotation. The dominant deformation mechanism involved dislocation slip and twinning. The ECAP deformation has a significant effect on the subsequent aging behavior. The microstructure of aged samples comprised αs phase in β matrix. The precipitation of αs phase in the pre-deformed sample is higher than that in the solution treated sample, which is reflected in the improvement of microhardness of the pre-deformed + aging sample. The microhardness of the alloy after ECAP deformation increases with decreasing aging temperature and increasing aging time. [ABSTRACT FROM AUTHOR]

Clarifying the aging behavior and attenuation mechanism of retired batteries is helpful to reuse them safely and efficiently. The aging behavior of a retired battery system similar to a blind box was studied by means of capacity calibration, cycle aging and material surface analysis. The results show that although the whole retired battery system is retired according to the rule of capacity attenuation to 80%, the state of health（SOH） value of most battery modules in the retired battery system is much higher than 80%. The selected battery module only circulates below 60% SOH for 400 times in the aging mode of 2 C-rate and 100% depth of dischar-ege（DOD）. The attenuation of the first 200 cycles is slow, and the attenuation of the last 200 cycles is fast. The results of material surface analysis show that the deterioration of anode is more serious than that of cathode after cyclic aging, and the consumption of recyclable lithium is one of the main reasons for the attenuation of battery capacity. Therefore, when the retired batteries are used in echelon, they can be sorted and grouped from the module level to maximize their residual value. At the same time, the retired batteries should be used under mild working conditions such as low current rates and shallow charge and discharge as much as possible. [ABSTRACT FROM AUTHOR]

The study aimed to assess the association between body image perception and (dis)satisfaction and the anthropometric profile of older women. Data from 60 women attending a senior community center were analyzed. Body image perception and (dis)satisfaction were considered dependent variables and were assessed using a silhouette scale constructed for the Brazilian population. The independent variables were body mass (BM), body mass index (BMI), waist circumference (WC), and calf circumference (CC). The associations were performed by logistic and linear regression models. Half of the participants overestimated their body size and 61.7% were dissatisfied due to excess weight. Overweight older women had 3.6 times higher odds to overestimate body size and 14.4 higher odds to be dissatisfied due to excess weight compared to normal-weight women. The increase in BM, BMI, WC, and CC raised mean difference between perceived and desired BMI and the odds of dissatisfaction due to excess weight. The anthropometric profile was more important to explain (dis)satisfaction than body size perception. The stimulus to changes that provide the adequacy of the anthropometric profile may reduce dissatisfaction due to excess weight among older women. [ABSTRACT FROM AUTHOR]

The present study evaluates the process activation energy or thermal diffusion activation energy (TDAE) to understand the aging kinetics or transformation kinetics. AA7075–5 Vol.% of SiCp composite were fabricated through stir casting technique. Differential scanning calorimetry (DSC) was carried out at different heating rates to understand the precipitation sequence and evaluate the process activation energy or thermal diffusion activation energy (TDAE) of composite. Rockwell hardness tests investigated the aging behavior of AA7075–5 Vol.% of SiCp composite. Results show incorporation of SiCp in the matrix does not affect the sequences of formation and dissolution of precipitate but affects the kinetics of precipitation growth. The formation of precipitation in the alloy and composite requires an access amount of vacancies; an increase in dislocation density may result in heterogeneous nucleation of precipitation and create free path for the kinetically faster atomic transportation of precipitates. Hence, incorporation of SiC particles in the composite would offer a lot of nucleation sites for precipitate, resulting in lower activation energy to form precipitates and takes less time to reach the maximum hardness. In contrast, the addition of a lesser volume fraction of SiCp also showing accelerated aging phenomena in the composite during the aging process. The hardness profile shows hardness increases 3.86% compared to the base alloy AA7075. High-resolution transmission electron microscope (HRTEM) micrograph of peak age (T6) condition divulges that enormous fine and plate-like ή (MgZn2) precipitates are uniformly distributed in the composite. [ABSTRACT FROM AUTHOR]

Broadband light absorbers are attractive for their applications in photodetection and photothermic conversion. Metal black absorbers are highly nanoscale porous deposits in the presence of inert gas and exhibit nanoscale structure. Silver nanoparticles have attracted intensive research interest because of their distinctive electrical and optical properties. Here, we fabricated a number of silver black films with nanoscale thicknesses under various gas ambient atmospheres (He and Ar). Our aim is to fabricate broadband absorbers with high absorption performance from the visible-to-mid-IR (MIR) spectral range and investigate their aging behaviors. The He-ambient silver black film exhibited average absorption coefficients of 3.17, 2.27, and 1.81 μm–1 in the visible, near-IR (NIR), and MIR ranges, respectively, with the highest value of 6.50 μm–1 at a wavelength of 357 nm. Those of the Ar-ambient film were 0.48, 0.51, and 0.443 μm–1 in visible, NIR, and MIR ranges, respectively. The absorption coefficients of the He-ambient film were much higher than those of the Ar-ambient film, which were very promising candidates as broadband absorbers. Moreover, metal black films suffered from aging phenomena because of their nanoscale porous structure. The long-term stability of the optical properties was worthy of attention for applications. Therefore, the room temperature aging behaviors of nanoscale-thick silver black films were investigated. Comparative analyses of the atomic content before/after aging demonstrated that the aging was attributed to crystallization, deliquescence, and oxidation. Comparative analyses of the absorption and photothermal response characteristics before/after aging were also performed. The results demonstrated that the nanoscale-thick silver black films possessed great absorption stability in the visible-to-MIR range and photothermal response stability, which can provide valuable reference for applications of broadband absorbers such as IR dynamic scene generation. [ABSTRACT FROM AUTHOR]

With their excellent balance of strength, electrical conductivity and ductility, copper alloys are widely applied. However, miniaturized products must be high-strength while maintaining high electrical conductivity. Herein, we analyze whether severe plastic deformation can improve the aging property of copper alloy. We experimentally investigated the aging properties and microstructures of CuCrZr alloys after a remarkable torsional plastic deformation (RMACREO) process. The RMACREO-processed specimen exhibited a lower aging temperature than the solution-heat-treated specimen without degrading the Vickers hardness and electrical conductivity. We suggest that the RMACREO process introduced a large amount of distortion in the microstructure and generated a sub-grain structure. The RMACREO process apparently decreased the generation activation energy of the chromium precipitates, thereby decreasing the aging temperature. [ABSTRACT FROM AUTHOR]

Epoxy potting materials are inevitably exposed to cyclic temperature environments during use. Under temperature load, thermal stress concentration occurs inside the epoxy encapsulation layer and leads to interface debonding and resin cracking, which eventually leads to the failure of the encapsulated component. In view of this, the effects of thermal cycling on epoxy resin and its encapsulated assemblies were investigated in this work. The surface morphology was characterized by scanning electron microscope (SEM) and atomic force microscope (AFM), the mechanical properties were measured by the Shore hardness tester and universal electronic extensometer, and the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to explore the thermogravimetric and thermal stability of epoxy resin under thermal cycling. The electrical properties of encapsulated assemblies of epoxy resin were measured by broadband dielectric spectroscopy and breakdown voltage. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the changes of the epoxy molecular structure before and after thermal cycling. Based on the aforementioned results and analysis, an aging mechanism of epoxy resin under an alternating thermal cycle was proposed. [ABSTRACT FROM AUTHOR]

In this paper, the effects of tea polyphenols and matcha on the aging behavior and digestibility of extruded fresh wet rice noodles during 180 days of storage were explored. The results showed that adding of tea polyphenols and matcha can significantly reduce the hardness of fresh wet rice noodles and inhibit the aging degree. At room temperature, tea polyphenols had a significant effect on inhibiting the aging of fresh wet rice noodles in the early storage period (0~60 d), while matcha had a relatively better effect in the middle and late storage period (90~180 d). The aging-inhibiting effects of tea polyphenols and matcha at 4 ℃ were limited, and the aging degree of different types of fresh wet rice noodles was close at the end. In addition, compared with the raw fresh wet rice noodles, adding tea polyphenols and matcha could increase the slowly digestible components (SDC) and resistant components (RC) of fresh wet rice noodles. The effect of tea polyphenols was more significant. During storage at room temperature and 4 ℃, tea polyphenols and matcha played a significant role in the RC increasing in fresh wet rice noodles. The results provided basic data for the development of nutritious and healthy fresh wet rice noodles.

Abnormal grain growth (AGG) at longitudinal weld of 2196 AlCuLi profile was observed during solution treatment, and the effects of AGG on the aging behavior and mechanical properties of the profile were investigated. The results show that the AGG area almost contained no low angle grain boundaries (LAGBs) while the fine extrusion fibers in the matrix area contained numerous LAGBs. The AGG structure at weld seam leads to precipitated phases coarsening, PFZ widening and a sharp decrease of elongation in profiles. During aging process, the AGG area precipitated more coarse S′/S and T2 phases and exhibited a faster age hardening rate than the matrix area, while the numerous LAGBs in the matrix area promoted the precipitation of strengthening phases (T1, δ′/β′) and suppressed the formation of coarse phases. The phases formed along the grain boundaries are mainly coarse quasi-crystal T2 phases while abundant fine T1 phases formed along the LAGBs of the matrix area, and the PFZ of AGG area is far wider than that in matrix area. During the pre-stretching process, the fine grains and LAGBs of the matrix area conduced to form and store more dislocations, which provided more nucleation sites for T1 phases.