Aged Samples Research Articles

Effect of Hygrothermal Aging on the Decomposition Reactions of Magnesium/Teflon/Viton (MTV) Pyrotechnic

ABSTRACTMagnesium/Teflon/Viton (MTV) pyrotechnic compositions are widely used in various applications. Magnesium is known to oxidize under elevated humidity and temperature conditions. Consequently, the performance of MTV pyrotechnics degrades as they age. Accurate characterization of the aging process is necessary for the prediction of storage life and performance of MTV pyrotechnics. This study investigates the hygrothermal aging of an MTV pyrotechnic mixture using accelerated aging, thermogravimetry (TG), differential scanning calorimetry (DSC), and differential thermal analysis (DTA). The kinetic parameters were obtained using the Friedman isoconversional method. Differential TG (DTG) curves were analyzed to identify the reaction steps occurring during the decomposition of pristine and aged MTV samples. Scanning electron microscope–electron‐dispersive spectroscopy (SEM–EDS) and Fourier transform infrared (FTIR) spectroscopy revealed changes in morphology and chemical composition. As expected, increased humidity caused significant degradation of the metallic fuel in the MTV pyrotechnic. Furthermore, the formation of unwanted compounds due to aging was clearly observed. The formation of these compounds, in addition to the depletion of the metallic fuel, was realized to be the cause of reduced the performance of aged MTV pyrotechnics.

Hydrothermal Stability of Active Sites in Cu-Exchanged Small-Pore Zeolites for the Selective Catalytic Reduction of NOx.

Combining operando X-ray absorption spectroscopy (XAS) and computational modelling shows unequivocally the distribution of active species in fresh and hydrothermally aged Cu-CHA and Cu-AEI zeolites during NH3-assisted selective catalytic reduction of NOx. Four principal species co-exist: (i) CuI cations coordinated to NH3, (ii) CuI cations coordinated to the zeolite framework, (iii) solvated CuII cations, and (iv) framework-coordinated CuII species (CuII st) formed upon hydrothermal ageing of the zeolite sample. The CuII st species were only observed in the hydrothermally aged zeolite samples and are formed upon the interaction of hydrated CuII cations with extra-framework Al (EFAl) generated during the hydrothermal treatment. These sites are inactive for NOx reduction, leading to a decrease in the catalytic performance of the hydrothermally aged zeolites. CuII st formation was higher in Cu-CHA (~46 %) than in Cu-AEI (~28 %). The better hydrothermal stability of Cu in the AEI framework is attributed to the tortuous channel structure of AEI that hinders the migration of hydrated CuII cations during hydrothermal ageing.

Multimodal HSI Combined with Multiblock Data Fusion: A New Tool for the Study of Time-Dependent Alteration Processes in Dyed Textiles.

The present study describes an innovative approach for the study of time-dependent alteration processes. It combines an advanced hyperspectral imaging (HSI) system, to collect visible reflectance and fluorescence spectral data sets sequentially, with a tailored multiblock data processing method. This enables the modeling of chemical degradation maps and the early, spatially resolved detection of dye alteration in textiles. A chemometric method based on data fusion and principal component analysis was employed to identify spectral features of dye degradation, combining and enhancing information from reflectance and fluorescence HSI data. The most significant spectral profiles extracted were used to develop an asymmetric Gaussian-based pixel-by-pixel fitting model applied to the HSI fluorescence data set, enabling the reconstruction of degradation maps for rapid and intuitive visualization. In particular, changes in intensities and horizontal shift of dye emission peaks were pixel-by-pixel evaluated and fitted for the reconstruction of the degradation maps. Artificially aged wool samples tinted with indigo carmine (IC) dye served as a case study. IC is extensively used in textiles, and it is notable for its light sensitive. The results show that this approach effectively identifies spatial variations and chemical changes in dyed wool fibers, offering potential for sustainable conservation of historical textiles and other types of time-dependent processes. Thus, by amplifying variation in spectral profiles induced over time by aging, even minimal changes at early stages can be easily detected and localized, offering powerful tools for future studies on food and drug shelf life and stability, as well as forensic trace analysis.

Effect of solution aging treatment on corrosion resistance and erosion resistance of laser metal deposition 17-4PHss

Slurry erosion and cavitation erosion are the primary causes of failure in pass flow components, and preventive maintenance can effectively extend their service life. In this paper, 17-4PH stainless steel was prepared using laser metal deposition (LMD) technology and aged to investigate the effect of solution treatment on its microstructural transformations. The microhardness, electrochemical corrosion behavior, slurry erosion resistance, and cavitation erosion behavior of the as-built and solution-treated, aged samples were analyzed, with traditional forged specimens used as controls. During heat treatment, the microstructure fully transformed to martensite, and NbC precipitated as a second phase. Solution treatment led to microstructural coarsening, while aging significantly refined the microstructure and produced partial reverted austenite. Microhardness analysis showed that the microhardness of the solution-treated and aged samples increased to 465.5 ± 8.6 HV0.2 due to the combined effects of finer and more uniformly distributed NbC precipitation and grain refinement. The solution aging samples exhibited the lowest corrosion current density and the highest corrosion potential, influenced by the presence of reverted austenite. Slurry erosion results indicated that the corrosive environment accelerated mass loss due to the synergistic effects of mechanical abrasion from gravel and brine corrosion. Meanwhile, the solution aging samples demonstrated superior resistance to slurry erosion, with mass losses in clear water and brine slurry of only 69 % and 63 % of those observed in the traditional forged samples. In the cavitation erosion experiment, the solution aging sample showed the lowest cumulative mass loss (3.54 ± 0.18 mg), and the work-hardening of the reverted austenite further enhanced the cavitation erosion resistance of the solution aging sample.

Effects of aging of polyethylene microplastics and polystyrene nanoplastics on antibiotic resistance gene transfer during primary sludge fermentation

The increasing presence of nano and microplastics (NPs/MPs) in wastewater treatment plants and their inevitable accumulation in the sludge has raised serious concerns in recent years. This study investigated the effects of pristine and aged polyethylene microplastics (PEMPs), polystyrene nanoplastics (PsNPs), and their mixtures on the primary sludge fermentation process. Pristine MPs/NPs (150 μg/L and 2 g/L for PsNPs and PEMPs, respectively) underwent two weeks of weathering in the presence of humic and alginic acids. The results from a batch fermentation experiment (15 days, pH 10) revealed that the exposure to aged PEMPs/PsNPs experienced greater VFA production than pristine samples. Notably, the aged PEMPs/PsNPs mixture showed a 23.12% increase in VFA production over the pristine mixture. The relative abundance and total concentration of antibiotic resistance genes (ARGs) increased in all PEMPs/PsNPs batches compared to the control, with the most significant rise in total ARGs observed in the aged PEMPs sample. Aged PEMPs exhibited a 26.22-fold increase in tetA genes, while aged mix samples showed a 19.68-fold increase in tetM genes compared to their pristine counterparts. Both pristine and aged PEMPs/PsNPs, particularly the aged PEMPs adversely affected the microbial communities at the genus level and altered the microbial structure. Microbial richness and diversity were enhanced in samples exposed to pristine PEMPs/PsNPs and aged PsNPs but decreased in aged PEMPs and in the aged mixture group, suggesting a negative impact of aged polyethylene microplastics on microbial communities. Correlation analysis suggested that phyla Planctomycetes, Proteobacteria, and TM7 are potential hosts of ARGs. These findings manifest the substantial effects of aged nano/microplastics compared to their pristine forms, emphasizing the complex interplay between various forms of PEMPs/PsNPs and microbial dynamics in sludge fermentation processes.

Effect of irradiation on Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles and their catalytic efficiency in water treatment

This study investigates the magnetic, thermal, and electrical properties of Co0.72Sr0.07Ni0.21Fe2O4 ferrite nanoparticles under different conditions, including as-prepared, irradiated (at a dose of 100 kGy in CO2 atmosphere), and aged (at 1000°C). The magnetic properties are analyzed using M-H loops, revealing that the aged sample exhibits the highest magnetization values. The observed decrease in magnetization after irradiation and increase after aging is consistent due to the presence of a new phase (γ-FeOOH) in the irradiated sample that XRD confirms. Electrical conductivity measurements demonstrate that the aging sample exhibits the highest electrical conductivity due to increased grain boundaries, while the irradiated sample shows increased conductivity attributed to oxygen vacancies. As well as the nanocomposite of PVP and Co0.72Sr0.07Ni0.21Fe2O4 nanoparticles aged (at 1000°C) is found to be effective in degrading the Toluidine Blue (TB) dye through catalytic oxidation and photodegradation mechanisms. The catalytic degradation of TB dye provides valuable insights into the potential application of these ferrite nanoparticles in environmental remediation and wastewater treatment. Also, nanocomposite demonstrated significant antimicrobial activity against five pathogenic bacterial strains commonly found in contaminated water, with superior effectiveness against Gram-negative bacteria, particularly Salmonella enterica and Pseudomonas aeruginosa, suggesting its potential as an effective water treatment agent. The novelty and the aims are to analyze the changes in magnetization and conductivity of the nanoparticles under different conditions, including as-prepared, irradiated, and aged samples. Additionally, the catalytic efficiency of the aged nanoparticles in degrading Toluidine Blue (TB) dye is examined, providing insights into their potential application in environmental remediation and wastewater treatment.

Influence of surface chemical modifications on enhancing the aging behavior of capacitor biaxially-oriented polypropylene thin film

Modern power electronic systems require appropriate metallized polypropylene capacitors (MPCs) to operate in harsh environments. Due to their limited operating capabilities, commercial biaxially-oriented polypropylene (BOPP) films—the primary component of MPCs—are susceptible to degradation in high electric fields and at high temperatures. In order to enhance the aging behavior of BOPP, this work proposes one-sided phosphorylation at optimum and excessive acid concentrations of 8 % and 15 % for 24 hours at a [high] temperature of 60 °C. The proposed surface modifications' success in enhancing the aging behaviors of BOPP is confirmed by DC electrothermal aging. Field emission scanning electron microscopy (FE-SEM) analysis reveals changes in surface morphology resulting from phosphorylation. The changes in crystal structure of the original and phosphorylated samples are evaluated using X-ray diffraction (XRD). The average crystallite size, dislocation density, and microstrain during aging are also characterized using the Williamson-Hall (W-H) analysis method. Fourier transform infrared (FTIR) spectroscopy is used to identify changes in the chemical composition and functional groups resulting from phosphorylation and aging, while X-ray photoelectron spectroscopy (XPS) is used to analyze changes in the surface chemical elements of the original, phosphorylated, and aged samples. The charge-thermally stimulated discharge (C-TSD) technique and broadband dielectric spectroscopy (BDS) are used to verify the electrical performance. Mechanical properties, including thermal stability, are measured using the dynamic mechanical analysis (DMA) technique. The results indicated that the optimized phosphorylation improved the BOPP film's electrical and mechanical properties. As a result, the surface charge stability was found to increase under thermally stimulated discharge by 74 % and the dielectric constant by 2 %, while the dielectric losses decreased by 20.2 %. Under aging, for the first time, the dielectric constant was found to increase by 4.8 %, while dielectric losses decreased by 8.9 %. In return, deformation resistance, ductility, and lower energy dissipation demonstrated enhanced mechanical performance.

Effect of hygrothermal ageing on the mechanical properties of glass fiber reinforced polymer composite: Experimental and numerical approaches

This paper studied the effect of hygrothermal ageing on the mechanical performance of glass fiber-reinforced polymer composites (GFRPCs), a crucial material for marine applications due to its lightweight and superior resistance to environmental chemicals. However, prolonged exposure to moisture and temperature can degrade its properties, impacting structural integrity. The influence of moisture diffusion in GFRP composite laminates was evaluated by accelerated ageing tests, which involved submerging the composite laminate in seawater at 75°C until it reached full saturation. The composite laminates were fabricated with weight fractions of glass fiber reinforcements 55 %, 60 %, and 65 %. After two months of submersion, mechanical characteristics, namely tensile strength, modulus of elasticity, and interlaminar shear strength (ILSS) were investigated. A computational model was developed using COMSOL Multiphysics to analyse the coupled interfaces of moisture diffusion and heat. The failure mechanism of the GFRP composites was analysed using a scanning electron microscope (SEM). After two months of submersion, the moisture uptake data for the tension test samples showed a maximum saturation of 3.45 % for the 55 % fiber weight fraction, leading to a reduction in tensile strength from 269 MPa to 171 MPa and in modulus of elasticity from 24 GPa to 21 GPa. For the ILSS test samples, the maximum moisture saturation was 2.95 % for the 55 % fiber weight fraction, with a corresponding decrease in ILSS from 24 MPa to 21 MPa. However, increasing the glass fiber weight fraction from 55 % to 65 % resulted in improved tensile strength, modulus of elasticity, and ILSS in both as-manufactured and aged samples. The results of simulations and experiments showed that hygrothermal ageing causes the fiber surface to debond and causes matrix cracking, which in turn creates an uneven internal stress field.

A multi-class support vector machine classification model based on 14 microRNAs for forensic body fluid identification

MicroRNAs (miRNAs) are promising biomarkers for forensic body fluid identification owing to their small size, stability against degradation, and differential expression patterns. However, the expression of most body fluid-miRNAs is relative (differentially expressed in certain body fluids) rather than absolute (exclusively expressed in a specific body fluid). Moreover, different body fluids contain heterogeneous cell types, complicating their identification. Therefore, appropriate normalization strategies to eliminate non-biological variations and robust models to interpret expression levels accurately are necessary prerequisites for applying miRNAs in body fluid identification. In this study, the expression stability of six candidate reference genes (RGs) across five body fluids was validated using geNorm, NormFinder, BestKeeper and RankAggreg, and the most suitable combination of RGs (hsa-miR-484 and hsa-miR-191–5p) was identified under our experimental conditions. Subsequently, we systematically evaluated the expression patterns of the 28 most promising body fluid-specific miRNA markers using TaqMan RT-qPCR and selected the optimal combination of markers (12 miRNAs) to establish a multi-class support vector machine (MSVM) classification model. An independent test set (60 samples) was used to validate the accuracy of the proposed classification model, while an additional 30 casework samples were used to assess its robustness. The MSVM model accurately predicted the body fluid origin for almost all (59/60) single-source samples. Moreover, this model demonstrated the capability to identify aged forensic samples and to predict the primary components of mixed stains to a certain extent. In summary, this study presented a miRNA-based MSVM classification model for forensic body fluid identification using the qPCR platform. However, extensive validation, especially inter-laboratory collaborative exercises, is necessary before miRNA can be routinely applied in forensic identification practice.

Post-harvest processed parsnip showed improved anti-oxidative capacity and protective potential against acrolein-induced inflammation in vitro and in vivo.

Post-harvest processing plays a crucial role in enhancing the bioactive properties of vegetables. This study aimed to investigate the impact of post-harvest aging on parsnip's bioactive profile and its protective effects against acrolein (Acr)-induced inflammation, a common pollutant and irritant linked to respiratory inflammation. Parsnips (Pastinaca sativa L.) were aged at 60°C for up to 30 days, with extracts collected at intervals. Total phenolic content (TPC) and antioxidant capacity were assessed using DPPH assays. Key bioactive compounds, including falcarindiol, DDMP, and 5-HMF, were quantified. In vitro studies used BEAS-2B cells to evaluate anti-inflammatory effects, while in vivo tests involved treating Acr-exposed mice with aged parsnip extract to observe cytokine responses. Aged parsnip extracts showed a 9.96-fold increase in TPC and a 4.25-fold increase in antioxidant capacity after 30 days. Bioactive compounds significantly increased in aged samples, especially falcarindiol and 5-HMF. In vitro, aged parsnip reduced Acr-induced TNF-α and IL-1β expression. In vivo, treated mice showed reduced bronchial inflammation, goblet cell hyperplasia, and cytokine expression compared to controls. These findings suggest that post-harvest aging enhances parsnip's antioxidant and anti-inflammatory properties, highlighting its potential as a functional food ingredient for managing inflammation and respiratory health.

Vaterite-type calcium carbonate and aminopropyltriethoxysilane-modified cellulose nanofibrils for preservation of aged paper

Deacidification and structural reinforcement are critically important for the long-term preservation of paper cultural relics. In this study, a novel approach is presented to synergistically combine highly reactive vaterite-type calcium carbonate with aminopropyltriethoxysilane-modified cellulose nanofibrils (NH2-CNFs) for the restoration of aged paper. Employed as a deacidification agent, vaterite demonstrated superior efficacy at a low dosage in comparison with commercially available calcite-type calcium carbonate. Concurrently, the carboxylate content of NH2-CNFs was reduced, enhancing its hydrophobicity and thermal stability. A comprehensive characterization of both vaterite and NH2-CNFs was conducted using multiple analytical techniques. Upon application of this restoration system to aged paper samples, the pH and alkaline reserve were elevated to 8.05 and 0.637 mol/kg, respectively. The tensile strength of the paper sample was augmented by 15 %, while folding endurance and tearing resistance were enhanced by 139 % and 66 %, respectively. Notably, the integration of vaterite exhibited no deleterious impact on the mechanical properties of the paper substrate. Additionally, this treatment imparted a substantial anti-aging effect, as evidenced by the results of dry heat and UV-irradiation aging. Consequently, this research introduces a novel and efficacious methodology for the restoration of aged paper, offering promising implications for the conservation of historical documents.

The development of two fast genotyping assays for the differentiation of hemp from marijuana

AbstractThe legalization of hemp cultivation in the United States has raised the need for reliable methods to distinguish between legal hemp and illegal marijuana. Genetic analysis has emerged as a powerful tool, surpassing traditional chemical methods in specific aspects, such as analyzing trace amounts, aged samples, and different parts of the sample. Genetic differences in cannabinoid synthase genes offer promise for precise crop type determination, particularly focusing on genes like tetrahydrocannabinolic acid synthase (THCAS), cannabidiolic acid synthase (CBDAS), and cannabichromenic acid synthase (CBCAS). However, previous research faced several challenges in developing discriminatory genetic markers, including limited sample sizes, high similarity between the synthase genes, and the presence of pseudo synthase genes. A comprehensive study using Next‐Generation Sequencing (NGS) introduced a differentiation flowchart based on THCAS, CBDAS, and THCAS pseudogenes. To bridge the gap between NGS and the practical requirements of crime laboratories, two rapid genotyping assays were developed: a CE‐based SNaPshot™ assay and a TaqMan™ real‐time PCR assay. While the SNaPshot™ assay effectively differentiated various hemp and marijuana types, differentiation was limited with marijuana samples containing THC% close to the 0.3% legal threshold (0.3%–1%). The TaqMan™ qPCR SNP genotyping assay provided quicker results, making it an efficient choice for crime laboratories. However, this method had the same limitations as the SNaPshot™ assay with addtional challenges in differentiating edible hemp seed samples, and it did not provide additional CBD information. The study also highlighted the influence of two variants of one THCAS pseudogene on chemotype determination, emphasizing the necessity for precise genetic analysis for accurate categorization of cannabis varieties.

A Quaternary aminostratigraphy for the Pannonian Basin: The competing influences of time, burial depth and temperature in deep-core material

Long-term terrestrial archives of Quaternary climate change illustrate how global changes affect regional climates, but correlation of terrestrial deposits to global records can be challenging due to a lack of material for radiometric dating. The Pannonian Basin (Hungary) contains large river basins, with near-continuous Quaternary deposits ∼600 m in depth. This study tested the IcPD (intra-crystalline protein degradation) approach to amino acid geochronology using bithyniid snail opercula to date deep-core material in geothermally warm regions. Material from seven fully-cored boreholes was collected from four sub-regions: the Körös and Jászság basins, Makó Trough and Békés Basin. IcPD increased with age until approximately 2.3 million years ago, generally supporting stratigraphic correlations previously made between the boreholes. IcPD was consistent between different boreholes within the same sub-region. However due to the steep geothermal gradient in this region, IcPD was systematically different between sub-regions that had different sedimentation rates. Equivalently aged samples buried more deeply had higher IcPD levels, indicating a greater geothermic effect. This provides an insight into how variations in burial temperature can affect protein decomposition within a deeply-buried (>80 m) fossil over geological time, and demonstrates the importance of understanding the geothermal setting for amino acid geochronology. This study shows the utility of IcPD to correlate terrestrial deep-core sediments over the Pleistocene.

Hyper-binding: the surprising roles of age and affect.

When irrelevant stimuli are processed and then bound to relevant stimuli in memory, it is known as hyper-binding. Hyper-binding has been demonstrated consistently in older-aged participants, but university-aged participants do not typically show hyper-binding. This phenomenon has been attributed to older individuals having greater difficulty filtering out irrelevant information compared to younger adults. Emotions can also influence how individuals attend to and process information, and older individuals report feeling greater positive, and less negative, affect than younger adults. Low arousal positive affect is associated with greater cognitive breadth and reduced distractor suppression. Therefore, it is possible that differences in affect contribute to the differences in hyper-binding demonstrated for younger versus older adults. In four studies, we measured hyper-binding using a standard hyper-binding task and examined whether individual differences in hyper-binding could be predicted by individual differences in self-reported affect. Study 1 included an online community sample between 18 and 45years of age. Study 2 included university undergraduate students that were tested online. Study 3 participants included university undergraduate students that were tested in the lab. Study 4 participants included an older aged sample that was tested online. Overall, there were no significant relationships between affect and hyper-binding across age samples. Surprisingly, however, significant hyper-binding was observed for all age groups and was not larger for older individuals. The results suggest that individual differences in naturally occurring affect do not meaningfully predict hyper-binding, but the prevalence of hyper-binding across all studies demonstrates it may not be unique to older adults.

Investigation of Combined Aging and Mullins Stress Softening of Rubber Nanocomposites.

The present study investigated the effects of thermal aging, ultraviolet radiation (UV), and stress softening on the performance properties of rubber modified with Cloisite Na+ or Cloisite 20A. Tensile strength (TS), strain at break (SB), modulus, and the retention coefficient were measured before and after aging. Results showed that TS and SB decreased by about 50% after 7 days of aging for all tested samples due to the breakage of the chemical bonds between rubber and nanoparticles. The modulus at 300% elongation increased by 20%, 15%, and 7% after thermal aging for the unmodified sample, nanocomposites with Cloisite Na+, and Cloisite 20A, respectively. The shape retention coefficient of all samples was not affected by heat, except for the virgin rubber sample, which exhibited a decrease of about 15% under thermal aging. The virgin matrix and nanocomposites showed different values of aging coefficient during thermal aging and UV radiation. The dissipated energy of samples that were aged after stretching was slightly higher than that of samples that were aged after stretching due to the breakdown of the bonds within the nanocomposites. Loading-reloading energy results showed that the level of stress softening was lower when Mullins was applied after the aging of the samples. Differential scanning calorimetry results indicated a slight decrease in Tg1 in the aged and stretched samples and an increase in the temperature of the first endothermic peak due to the addition of nanofillers in the stretched and aged samples. Thermogravimetric analysis revealed that all tested samples exhibited similar thermograms, regardless of their state of stretching or aging. Scanning electron microscopy analysis showed that the fracture surface of the virgin unaged sample was rough with some holes, while it was flatter and less rough after aging.

Utilizing a combination of experimental and machine learning methods to predict and correlate between accelerated and natural aging of CFRP/AL adhesive joints under hygrothermal conditions

AbstractThis study investigates how carbon fiber reinforced polymer (CFRP)‐to‐aluminum adhesive joints behave under accelerated aging conditions with hygrothermal exposure and compares these findings against naturally aged samples to evaluate material reliability in challenging environments. The CFRP‐to‐aluminum adhesive joints were manufactured and subjected to natural aging for durations ranging from 1 to 3 years with 6‐month intervals, as well as accelerated aging (hygrothermal) for periods ranging from 100 to 1200 h, with intervals of 50 h. Subsequently, the mechanical properties of the joints were evaluated using a three‐point bending test. To forecast natural aging times from accelerated aging data, five machine learning models were utilized: artificial neural network, support vector regression, linear regression, polynomial regression, and random forest regression. Hygrothermal aging significantly degraded the matrix, causing a shift in failure modes from cohesive to mixed types (cohesive, adhesive, and fiber tear failures), leading to a notable decline in bending strength. The study observed a 23.13% strength reduction in samples aged naturally for 3 years and a 24.33% decrease in those subjected to 1000 h of accelerated aging. The random forest regressor demonstrated superior accuracy in predicting natural aging times across different accelerated aging periods. Through the application of machine learning models, this study introduces a novel approach to forecast natural aging durations using data from accelerated aging experiments. This method shows potential for optimizing joints and composite structures, ultimately improving their durability and minimizing the likelihood of failures during operational use.Highlights Studied hygrothermal effects on accelerated aging of carbon fiber reinforced polymer/Aluminum (AL) adhesive joints. Noted strength reduction from hygrothermal aging. Used five machine learning models; random forest regression had the highest accuracy. Analyzed correlation between natural and accelerated aging of dissimilar adhesive joints.

Low-temperature oxidation behaviors of Cu-15Ni-8Sn alloy in different aging conditions

Cu-15Ni-8Sn (wt%) alloy has been widely used in engineering applications due to its excellent mechanical strength, wear, and corrosion resistance. However, low-temperature oxidation (LTO) poses a significant challenge, restricting its further application and longevity. In this study, the low-temperature oxidation behavior of the Cu-15Ni-8Sn alloy under different aging condition was investigated using multi-scale characterization by SEM and TEM. The characterization results reveal the oxide films of the aged sample contain tri-layers at low temperature, the outermost layer is dominated by CuO and Cu2O, the middle oxide layer contains of Cu2O, NiO, SnO2 and SnO, and the inner oxide layer is composed of NiO and SnO2. In addition, the as-quenched sample has superior oxidation resistance compared to the aged samples, and the oxidation resistance of the aged samples decreases with the increase of aging time. That is, there is a trade-off between hardness and oxidation resistance in aged Cu-15Ni-8Sn alloys. Therefore, these findings provided a way to adjust the aging parameter based on specific service conditions.

Enhancing wear resistance of CoNiCrMo medium entropy alloy through cold working and aging: Tradeoffs with corrosion performance

This study investigates the wear behavior and corrosion resistance of MP35 N alloy under various conditions, including annealed, cold-worked, and aged states. The microstructure was characterized using optical microscopy, X-ray diffraction, and transmission electron microscopy. Results indicated that cold rolling induced a dislocation structure and deformation features such as mechanical twins, stacking faults, and slip bands. The presence of non-homogeneous strain and planar defects in the cold-rolled samples led to broader diffraction peaks compared to the annealed samples. The microstructure of the cold-rolled and artificially aged samples exhibited deformation features, dislocation structures, and ultra-fine precipitates. High-angle annular dark field imaging and energy-dispersive X-ray spectroscopy revealed that these precipitates were Ti-rich particles, which, along with molybdenum segregation in stacking faults, contributed to the highest hardness observed. X-ray diffraction analysis confirmed the segregation and depletion of alloying elements from the lattice during aging. Wear and corrosion tests demonstrated that while cold working and aging enhanced the wear performance of the annealed CoNiCrMo alloy, they adversely affected its corrosion resistance. Specifically, the volume loss for cold-worked and aged samples was approximately 2.7 and 2.1 times smaller than that of the annealed specimen, respectively. However, the annealed alloy exhibited a lower corrosion current density (icorr) of 70 nA cm−2 compared to the cold-worked and aged samples, which had icorr values of 130 and 200 nA cm−2, respectively.

Sulphanilamide degradation by undoped and copper doped ZnO, and ferromagnetic properties of fresh, aged, and heat-treated aged ZnO

This work looks into how well Cu-doped zinc oxide works as a photocatalyst when exposed to visible light to break down sulphanilamide. The synthesized samples were characterized by XRD and then FTIR techniques for structural besides compositional analysis. The approximate value of bandgap found out by NBE values of PL spectra showed a decrease in bandgap with doping. Deconvoluted PL spectra revealed the presence of radiative recombination pathways associated with zinc interstitial and zinc vacancy in addition to band-to-band recombination in all samples. FESEM images showed a nanoflake shape for pure ZnO, while Cu-ZnO had a pseudo-spherical shape. SQUID-VSM was adopted to understand the magnetic nature of freshly prepared, heated, and unheated aged samples. Ferromagnetic behavior was observed with saturation magnetization of 5.56×10–4, 2.88×10–4, and 2.78×10–4 emu/g for freshly prepared, heated, and unheated aged samples, respectively. A 2% Cu-doped sample exhibited the highest efficiency of 92.3% towards the degradation of sulphanilamide. Since we got better efficiency for 2% Cu-ZnO, we should further decrease the doping percentage and check whether we will get even higher efficiency in the future. The photocatalytic degradation efficiency of ternary ZnO compounds, codoped ZnO, should be evaluated, yet another future scope.

Mechanical characterization and structural analysis of elastodontic appliances under intraoral and artificial aging conditions

BackgroundThis study focused on the aging mechanism and degradation of mechanical and structural features of elastodontic appliances (EA) under artificial and intraoral aging to achieve oral myofunctional therapy with particular removable silicone elastomer devices.Materials and methodsEAs artificially aged in saliva with different pH values were investigated through cyclic compression testing along with characterization techniques (Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy), and characterization analysis was also performed on clinically retrieved EAs.ResultsArtificial aging was found to have minimal effect on the structural properties of EAs, and intraorally aged samples showed perceptible micro-morphology. The Mullins index and peak stress decreased (P<0.01), while the compression set increased with prolonged aging time. Samples in alkaline saliva showed the largest Mullins effect (P<0.05).ConclusionsThe aging mechanism of the elastomer was found to be the crosslinking of main chains and scission of side chains. The presence of OH- enhanced the rupture degree of side bonds. The decline in viscoelastic properties was shown to be more severe with longer service durations.Clinical relevanceResearch on how the salivary environment and pH affect the aging characteristics of EAs is vital for guiding clinical applications and future modifications to extend their clinical lifetime.