Aging Time Research Articles

Influences of deformation defects on etching behaviors of high-strength and high-conductivity Cu alloy for lead frame

With increasing integration of the semiconductor devices, the requirements on size accuracy and surface quality of the lead frame are higher. Cold-rolling and low-temperature aging are usually used in processing of the Cu alloy for lead frame, which generate/eliminate the deformation defects that affect the etched surface morphology and roughness, while the influence mechanisms have not been well revealed. In this study, the CuCrSn alloy was used as the experimental material, which was cold-rolled to different degree and then aged at 450 °C for different time, and the microstructures and etched surfaces of the specimens were characterized. The results show that etched surface morphologies of grains with different orientations in the coarse-grained Cu alloy are different. With increasing cold-rolling deformation, the influences of grain orientation become less obvious, and the dislocation groups on the slip planes result in grooves approximately parallel to the rolling direction, meanwhile the surface uniformity are improved and the surface roughness decreases. For the 80 % cold-rolled Cu alloy, the density of grooves decreases with increasing aging time and elimination of the dislocations, and the etched surface roughness decreases firstly and then tends to be stable. The etched surface changes significantly and the surface roughness increase obviously after recrystallization of the specimen.

Long-term evolution of Ti-Cu amorphous film: Agglomeration and crystallization behaviors of Cu

Sometimes the films deposited by magnetron sputtering are in a metastable state. The films tend to transition to the equilibrium phase, which is crucial for the stability of the microstructure and properties of the films in practical applications. In this study, Ti-Cu films were deposited using a high-power pulsed magnetron sputtering technique, and the evolution of the microstructure of the film under natural aging and thermal aging conditions was systematically investigated. The results showed that the as-deposited Ti-Cu film was amorphous, and as the aging time increased, particles comprising Cu agglomerates and crystalline phases were gradually formed in the film. During aging treatments, Cu agglomerates at the Ti-Cu film led to strong scattering and absorption of the incident light, resulting in reflectance losses. Cu agglomerates at the film was more intense under thermal aging conditions than under natural aging conditions, which was attributed to the fact that the provision of additional temperature could accelerate the diffusion of the smaller Cu atoms in the Ti-Cu amorphous film. Exploring the long-term evolution of the Ti-Cu film structure will provide theoretical guidance for the stability of films in practical applications.

Investigating the Effects of Distillation System, Geographical Origin, and Aging Time on Aroma Characteristics in Brandy Using an Untargeted Metabonomic Approach.

In this study, the influence of the distillation system, geographical origin, and aging time on the volatiles of brandy was investigated. An untargeted metabolomics approach was used to classify the volatile profiles of brandies based on the presence of different distillation systems and geographical origins. Through the predictive ability of PLS-DA models, it was found that higher alcohols, C13-norisopenoids, and furans could serve as key markers to discriminate between continuous stills and pot stills, and the contents of C6/C9 compounds, C13-norisoprenoids, and sesquiterpenoids were significantly affected by brandy origin. A network analysis illustrated that straight-chain fatty acid ethyl esters gradually accumulated during aging, and several higher alcohols, furfural, 5-methylfurfural, 4-ethylphenol, TDN, β-damascenone, naphthalene, styrene, and decanal were also positively correlated with aging time. This study provides effective methods for distinguishing brandies collected from different distillation systems and geographical origins and summarizes an overview of the changes in volatile compounds during the aging process.

Effect of repeated-tempering induced martensite on the microstructural evolution in 17–7 PH stainless steel

Single long-time tempering and triple tempering processes have been applied to 17–7 PH stainless steel (chemical composition: Fe-0.09C-16.4Cr-7.7Ni-0.9Al, wt%) to investigate the effects of the stability of austenite on subsequent martensitic transformation and aging hardening. The as-received steel was composed of 0.55 austenite and 0.45 martensite (volume fraction). Scanning electron microscopy images showed that the volume fraction of martensite (up to 0.98) in triple-tempered specimens ((0.5 h @ 760 °C) × 3) was about 0.15 higher than that (0.83) in single-tempered ones ((1.5 h @ 760 °C) × 1). The results clearly indicate the effectiveness of the triple-tempering process in progressively improving martensitic transformation. Direct observation of the austenite/martensite interface has provided evidence that the preceding martensitic transformation induces accommodation strain into the adjacent austenite, which brings about the mechanical stabilization of austenite but will facilitate the succeeding martensitic transformation after three consecutive tempering operations. The relevant microstructural evolution has been explored and discussed. Furthermore, subsequent aging at 565 °C led to precipitation hardening associated with the formation of NiAl nanoparticles. The triple-tempered specimen yielded the higher peak hardness value (424 HV) in 20 min, significantly faster than the single-tempered specimen, which took 90 min to reach the lower one (357 HV). The corresponding number density of NiAl nano-precipitates and dislocation densities of martensite at various aging times have been examined by transmission electron microscopy to elucidate the benefits of the triple tempering process for precipitation strengthening.

Chemo-mechanical ageing of paper: effect of acidity, moisture and micro-structural features

A multi-scale modeling framework is proposed for the prediction of the chemo-mechanical degradation of paper, with the particular aim of uncovering the key factors affecting the degradation process. Paper is represented as a two-dimensional, periodic repetition of a fibrous network unit cell, where the fibers are characterized by a moisture-dependent chemo-hygro-mechanical constitutive behavior. The degradation of paper occurs primarily as a result of the hydrolysis of cellulose, which causes a reduction of the degree of polymerization and a consequent decrease of the effective mechanical properties, ultimately leading to fiber embrittlement and a loss of material integrity. The interplay between the acidity of the paper, the ambient environmental conditions, and its chemo-mechanical degradation behaviour is a complex process. In the model, these interactions are accounted for by determining the coupled temporal evolution of the degree of polymerization, the acidity of the paper, and the moisture content, from which the time-dependent tensile strength of the paper is calculated. The internal stresses developing in the fibrous network under a change in moisture content lead to brittle fiber fracture once they reach the fiber tensile strength. The successive breakage of individual fibers results in damage development in the fibrous network, altering its effective constitutive properties. The temporal evolution of the effective hygro-mechanical properties of the fibrous network is calculated by employing asymptotic homogenization. For obtaining accurate model input, the strength and stiffness properties of individual fibers and the degree of polymerization of paper samples are measured at different ageing times by carrying out dedicated experiments. Subsequently, a series of numerical simulations is performed to analyze the chemo-mechanical degradation process of paper, highlighting the influence of the time-evolving acidity and moisture content. The numerical study further considers the effects of micro-structural features (i.e., the anisotropy of the fibrous network orientation and the fiber longitudinal elastic modulus) on the macroscopic degradation response of paper. The results of this work may help conservators of cultural heritage institutions determining optimal environmental conditions to limit or delay the time-dependent degradation of valuable historical paper artefacts.

Effect of Ni content on 475°C embrittlement of directed energy deposited duplex stainless steel using a laser beam and wire feedstock

Duplex stainless steel (DSS), specifically the 2209 grade, is increasingly employed in additive manufacturing, particularly in processes like directed energy deposition using a laser beam with wire (DED-LB/w). However, a significant challenge arises when DSS faces brittleness within the temperature range of 250–500 °C. This study employs advanced characterization techniques, including atom probe tomography (APT) and transmission electron microscopy (TEM), to investigate DSS embrittlement after aging at 400 °C for up to 1000 h. The hardness analysis revealed that the higher Ni content in DED-LB/w-fabricated DSS cylinder promotes the age hardening compared to 2205 wrought DSS plate. Furthermore, APT and TEM demonstrated that, alongside the decomposition of ferrite into Fe-rich (α) and Cr-rich (αʹ) phases, clustering of Ni, Mn, and Si atoms contributes to the embrittlement. Although the Ni-Mn-Si-rich clusters could suggest nucleation of G-phase, the G-phase crystal structure was not observed by TEM. This might be attributed to the short aging time or limitations in the characterization technique. This work underscores the impact of characterization techniques on the measurement of spinodal decomposition, with APT providing capability of detecting nanometer sized clusters. By elucidating the complexities of 475 °C-embrittlement in DED-LB/w DSS, this study offers valuable insights for industrial applications and a deeper understanding of age hardening in duplex DSSs under specific manufacturing conditions.

Insight into compression-rebound behavior of lignocellulose-derived aerogel through finite element modeling based dynamic impact simulation

In this study, lignocellulose-derived aerogel (LA) with compression-rebound was synthesized from liquefied wood through sol-gel polymerization, aging and freeze-drying process. The results presented a gradual increase in the compressive strength, flexural strength, and maximum decomposition temperature of the LA sample with prolonged aging time from 3 to 10 h, demonstrating excellent elasticity and thermal stability. After more than 10 h, the bending strength began to decrease, indicating that the material’s rigidity was greater than its elastic toughness at this time. A nonlinear viscoelastic constitutive model based on the Ogden function and parallel rheological framework showed very high correlation with experimental measurement results, and also demonstrated admirable mechanical properties. These predictions can provide an effective approach for the application of LA in buffer packaging.

Effect of extreme environments on aging of fluoroelastomers

Fluoroelastomer compositions are used in extreme environments, such as high pressure and high temperature (HPHT), in a wide range of applications in the oil and gas industry. As hydrocarbon production is expanded to deeper formations, and operating temperature and pressure become higher, the material performance of these elastomers becomes more important. Hence, fluoroelastomers face new challenges and require further understanding when these undergo aging. In this study, a practical fluoroelastomer (FKM) composition was aged in deionized water and an alkaline hydraulic fluid up to 31 MPa, 225 °C and 168 hrs. High pressure, high temperature and aging time have deleterious effects on the physical and mechanical properties of FKMs in both the fluids. Spectroscopically, under these conditions, two hydrocarbon-related bands at 2917 and 2850 cm−1 and three fluorocarbon bands at 886, 1158 and 1396 cm−1 in the Fourier Transform Infrared spectra decreased in intensity after aging. The temperature, at which the rate of degradation was maximum, measured through thermogravimetry also decreased under HPHT conditions. It was further observed that the filler particles bound to the rubber leached out during the aging experiment to cause a color change of the fluid. The tensile sheet was delaminated with cracks on the surface under extreme conditions due to rapid changes in the properties of the surface compared to the bulk. Based on the characterization of the aged rubber vulcanizate and the particles leached out into the aging fluid, a mechanism of HPHT aging of FKM vulcanizate is proposed, which would be helpful in designing fluorocarbon compositions in extreme environments.

WPŁYW GENOTYPU I CZASU DOJRZEWANIA NA CECHY FIZYKOCHEMICZNE MI ˛ESNI ´ SZKIELETOWYCH BUHAJKÓW OPASANYCH W SYSTEMIE PÓŁINTENSYWNYM

The aim of the study was to determine the effect of the genotype and ageing time on pH, water holding capacity, shear force and energy, and the myofibrillar index of m. longissimus lumborum and m. semitendinosus muscles in semi-intensively fed bulls. Carcass value indices and the chemical composition of the muscles depending on the genetic group were assessed as well. The study involved 46 young bulls from four genetic groups, i.e. the Hereford breed (HER, 8 bulls), the Limousin breed (LIM, 8 bulls), commercial cross-breeds (MT, 14 bulls), and the Polish Black-and-White Holstein-Friesian breed (PHF, 16 bulls). The analyses showed that the semi-intensive fattening system ensures production of carcasses with satisfactory slaughter yield and quality parameters (good musculature and moderate fatness). The best quality parameters were determined in the meat from the LIM and MT young bulls, whereas the poorest results were exhibited by the PHF beef. The ageing time had a positive effect on the meat quality parameters (especially tenderness and color), contributing to a significant reduction in the differences between the genotypes observed in the initial postmortem period. The results of the shear force and myofibrillar index, i.e. parameters of meat tenderness, suggest that a 14-day ageing period seems to be the necessary minimum. This period should even be extended in the case of the LL muscle of HER and PHF young bulls or the ST muscle of HER, MT, and PHF young bulls. Further research with consumer assessment is therefore advisable to determine the optimal ageing time of beef produced in the country.

Cytological structures and physiological and biochemical characteristics of covered oat (Avena sativa L.) and naked oat (Avena nuda L.) seeds during high-temperature artificial aging

BackgroundSeed aging, a natural and inevitable process occurring during storage. Oats, an annual herb belonging to the Gramineae family and pooideae. In addition to being a healthy food, oats serve as ecological pastures, combating soil salinization and desertification. They also play a role in promoting grassland agriculture and supplementing winter livestock feed. However, the high lipid and fat derivatives contents of oat seeds make them susceptible to deterioration, as fat derivatives are prone to rancidity, affecting oat seed production, storage, development, and germplasm resource utilization. Comparative studies on the effects of aging on physiology and cytological structure in covered and naked oat seeds are limited. Thus, our study aimed to determine the mechanism underlying seed deterioration in artificially aged ‘LongYan No. 3’ (A. sativa) and ‘BaiYan No. 2’ (A. nuda) seeds, providing a basis for the physiological evaluation of oat seed aging and serving as a reference for scientifically safe storage and efficient utilization of oats.ResultsIn both oat varieties, superoxide dismutase and catalase activities in seeds showed increasing and decreasing trends, respectively. Variance analysis revealed significant differences and interaction in all measured indicators of oat seeds between the two varieties at different aging times. ‘LongYan No. 3’ seeds, aged for 24–96 h, exhibited a germination rate of < 30%, Conductivity, malondialdehyde, soluble sugar, and soluble protein levels increased more significantly than the ‘BaiYan No. 2’. With prolonged aging leading to cell membrane degradation, reactive oxygen species accumulation, disrupted antioxidant enzyme system, evident embryo cell swelling, and disordered cell arrangement, blocking the nutrient supply route. Simultaneously, severely concentrated chromatin in the nucleus, damaged mitochondrial structure, and impaired energy metabolism were noted, resulting in the loss of ‘LongYan No. 3’ seed vitality and value. Conversely, ‘BaiYan No. 2’ seeds showed a germination rate of 73.33% after 96 h of aging, consistently higher antioxidant enzyme activity during aging, normal embryonic cell shape, and existence of the endoplasmic reticulum.ConclusionsROS accumulation and antioxidant enzyme system damage in aged oat seeds, nuclear chromatin condensation, mitochondrial structure damage, nucleic acid metabolism and respiration weakened, oat seed vigor decreased. ‘LongYan No. 3’ seeds were more severely damaged under artificial aging than ‘BaiYan No. 2’ seeds, highlighting their heightened susceptibility to aging effects.

Impact of Aging Time on the Metallurgical Properties and Hardness Characteristics of an Al-Si-Mg-Cr Hypoeutectic Alloy Intended for Automotive Applications

This research investigates the microstructural evolution and mechanical properties of LM25 (Al-Si-Mg) alloy and Cr-modified LM25-Cr (Al-Si-Mg-Cr) alloy. Microstructural analysis reveals distinctive ε-Si phase morphologies, with Cr addition refining dendritic structures and reducing secondary dendrite arm spacing in the as-cast condition. Cr modification results in smaller-sized grains and a modified ε-Si phase, enhancing nucleation sites and reducing ε-Si size. Microhardness studies demonstrate significant increases in hardness for both alloys after solutionising and aging treatments. Cr-enriched alloy exhibits superior hardness due to solid solution strengthening, and prolonged aging further influences ε-Si particle size and distribution. The concurrent rise in microhardness, attributed to refined dendritic structures and unique ε-Si morphology, underscores the crucial role of Cr modification in tailoring the mechanical properties of aluminium alloys for specific applications.

Controlling catalytic and reaction factors for regulating the distribution of aromatic products in n-butane aromatization over Ga/HZSM-5

The selective production of benzene, toluene, and xylene (BTX) has the potential to enhance the overall economics of aromatic production and subsequent processes, owing to their differing applications in the petroleum industry. Despite the economic significance of selective BTX production, the individual selectivity of BTX and the corresponding generation mechanisms have not been thoroughly investigated. Therefore, this study aims to explore the factors that affect the distribution of BTX and their respective trends of variation during n-butane aromatization over Ga/HZSM-5. This study demonstrates that selective production can be achieved by controlling the conditions that significantly influence product distribution, including the reaction temperature, extent of catalyst deactivation, and distribution of acid sites. The selectivity for benzene relative to toluene increased with increasing reaction temperature but decreased with increasing catalyst aging time. In addition, Ga/HZSM-5, which had a low Si/Al ratio, exhibited a pronounced preference for benzene. Consequently, it is possible to control benzene to toluene selectivity ratio within a range of 0.5–1.1 while maintaining over 85 % of n-butane conversion by adjusting these key factors. Further results proposed that the distinct role of protolytic cracking over Brønsted acid sites may contribute to the shift in aromatics distribution toward benzene during the series reaction, whereas the dehydrogenation over Ga Lewis acid sites plays a promotional role in the shift toward toluene.

Alkali Extraction of Arsenic from Groundwater Treatment Sludge: An Essential Initial Step for Arsenic Recovery.

Arsenic (As)-bearing Fe(III) precipitate groundwater treatment sludge has traditionally been viewed by the water sector as a disposal issue rather than a resource opportunity, partly due to assumptions of the low value of As. However, As has now been classified as a Critical Raw Material (CRM) in many regions, providing new incentives to recover As and other useful components of the sludge, such as phosphate (P) and the reactive hydrous ferric oxide (HFO) sorbent. Here, we investigate alkali extraction to separate As from a variety of field and synthetic As-bearing HFO sludges, which is a critical first step to enable sludge upcycling. We found that As extraction was most effective using NaOH, with the As extraction efficiency increasing up to >99% with increasing NaOH concentrations (0.01, 0.1, and 1 M). Extraction with Na2CO3 and Ca(OH)2 was ineffective (<5%). Extraction time (hour, day, week) played a secondary role in As release but tended to be important at lower NaOH concentrations. Little difference in As extraction efficiency was observed for several key variables, including sludge aging time (50 days) and cosorbed oxyanions (e.g., Si, P). However, the presence of ∼10 mass% calcite decreased As release from field and synthetic sludges considerably (<70% As extracted). Concomitant with As release, alkali extraction promoted crystallization of poorly ordered HFO and decreased particle specific surface area, with structural modifications increasing with NaOH concentration and extraction time. Taken together, these results provide essential information to inform and optimize the design of resource recovery methods for As-bearing treatment sludge.

Influencing mechanisms of C content and aging treatment on intergranular corrosion sensitivity of 316 stainless steel weld metals

For analyzing the intergranular corrosion sensitivity of 316 stainless steel weld metals with different C contents, the intergranular corrosion behaviors of the weld metals under as-welded and different as-aged states were evaluated by both the H2SO4–CuSO4 solution corrosion method and the double loop electrochemical potentiokinetic reactivation method, respectively. The results indicate that after long term aging treatment at 550 °C, the δ ferrite in high C weld metal has a higher transformation fraction than that in low C weld metal, which results in a higher intergranular corrosion sensitivity for high C weld metal. However, after the long term aging treatment at 600 °C, the δ ferrite in high C weld metal transforms completely in the early stage aging, and with increasing of the aging time, the desensitization process occurs in the Cr-poor region of high C weld metal, which improves the intergranular corrosion resistance, and results in a higher intergranular corrosion sensitivity for low C weld metal. Therefore, under the service environment of considering the intergranular corrosion performance of the weld metal, the welding material with the appropriate C content should be selected according to the service temperature.

Optical, electrical, and mechanical reliability of 1700 PPI Micro-LED device

With the Micro-LED display device being widely used in the advanced display fields, the high reliability of device had become one of the key issues for applications of Micro-LED in many display fields such as VR/AR, portable displays, and flexible displays. The 512 × 384 green Micro-LEDs 0.39 in. array with 1700 PPI featuring a pixel pitch of 15 μm was integrated with the substrate by the AuIn flip-chip bonding. The average brightness, electroluminescence (EL) spectra, and I-V characteristics of the Micro-LED device aged at 85 °C/85 % RH for different time were measured to evaluate the optical and electrical reliability of the Micro-LED device. The mechanical reliability of the Micro-LED device after 336 h of aging was evaluated by shear test. The average brightness of the Micro-LED device decreased from 2.08 × 104 nit to 1.64 × 104 nit and the on-resistance of the Micro-LED device increased from 2.30 Ω to 2.82 Ω with the aging time increased to 336 h. The Micro-LED device was broken up with the shear strength value of 12.06 MPa, and the shear strength was only reduced by 8.25 % compared with that measured before aging.

Mechanical strength and low-velocity impact behavior of glass fiber reinforced filament wound pipes with different number of layers after hydrothermal aging

Composite pipe is preferred over metal and other materials for water supply, liquid chemical transport, and fuel and gas transport. This is because composite pipes are more corrosion resistant, have a high strength/density ratio, high stiffness/density ratio, and more durable than metal pipes. The properties of the composite pipes employed may differ based on the operating environment. Therefore, determining the properties of the composite pipe according to the working environment is extremely important for its lifespan. The thickness of the samples is increased in line with different needs (such as increased strength). Increasing the thickness of samples, especially those exposed to different environmental conditions, and investigating the changes that will occur in the physical and mechanical properties of the samples are another important situation. In this investigation, glass fiber (GFRP) reinforced epoxy composite pipes have been examined, which were manufactured using the filament winding method with different layers [±55°]. To determine their properties in different working environments, the GFRP composite pipes were subjected to hydrothermal aging in pure water at 80°C for several days (7, 14, 21, and 28). The changes in their mechanical properties under working conditions were determined through hoop tensile strength tests and low velocity impact tests applied at different energy levels. The experimental results show that the tangential stress values increased by 10.59% as the number of layers increased. As the aging time increased, the durability of the 6-layer composite pipe decreased by 17.69%. Furthermore, the ability of the aged pipes to withstand damage was evaluated, revealing that the aging process exacerbated the damage within the pipes.

A novel epoxy resin composite coating containing polyaniline modified GO with triple anti-corrosion effects of barrier, passivation and corrosion inhibition

Corrosion of metallic materials can have a detrimental impact on their performance, leading to a shortened service life of engineering equipment and posing risks to both people and the environment. This paper presents a novel epoxy resin (EP)-based composite coating (PFANI-GO/EP) that offers triple corrosion protection functions: barrier, passivation, and corrosion inhibition. Perfluorooctanoic acid-doped polyaniline modified graphene oxide (PFANI-GO) demonstrates superhydrophobicity, effectively enhancing the coating's barrier ability against corrosive substances. The combination of PANI and perfluorooctanoic acid (PFOA) in composite materials aids in the formation of a passivation film and hydrophobic layer, which prevent metal corrosion. After a 15-day immersion in brine, the PFANI-GO/EP coating demonstrates the highest impedance modulus of 1 × 109 Ω·cm2 at 0.01 Hz, compared to pure EP coating, GO/EP coating, and PFANI/EP coating. Therefore, due to its corrosion resistance and prolonged corrosion aging time, PFANI-GO/EP coating shows promising potential for mitigating metal corrosion.

Effect of hygrothermal aging on mechanical properties of continuous flax fiber composites

AbstractThe influence of hygrothermal aging on the mechanical properties of flax fiber‐reinforced polymer (FFRP) composites was studied by examining the mechanical properties and failure mechanism of the composite laminates exposed in distilled water at different temperatures. The resin transfer molding (RTM) process was used to manufacture FFRP laminates, which were then subjected to accelerated aging tests in distilled water at different temperatures. The moisture absorption characteristics of FFRP were analyzed by a water absorption test. Tensile, bending, and low‐velocity impact tests of laminates after different aging conditions were performed. Combined with DSC and FTIR tests, the failure mechanism of FFRP exposure to hygrothermal aging was analyzed. The result indicated that the increase in temperature will accelerate the moisture absorption process of FFRP, and the hygroscopic behaviors at different temperatures conform to Fick's law. In the early stage of hygrothermal aging, the composites undergo post‐curing, and the tensile and bending strengths increase. After that, the tensile and bending strengths are decreased because of the thermo‐oxygen aging of materials and fiber/matrix interface damage. After hygrothermal aging, the impact peak force of FFRP decreases obviously while the absorbed energy increases due to the increase of internal defects and plasticization of composites. The increase of hygrothermal aging temperature aggravates the aging of materials, resulting in a more obvious decline in the tensile, bending, and impact properties of the composites.Highlights The effect of hygrothermal aging on the mechanical properties of FFRP is investigated. With the increase of hygrothermal aging time, the tensile and bending strength of FFRP increased at the early stage of aging and then decreased. After hygrothermal aging, the impact peak force of FFRP decreases and the absorbed energy increases due to the increase of internal defects and plasticization of composites.

Investigating the effects of corrosion parameters on the surface resistivity of transformer’s insulating paper using a two-level factorial design

The integrity of the insulation in oil-filled power transformers, shunt reactors, and high voltage bushings can be affected when copper dissolves in the insulating oil and then deposits onto the paper insulation. The presence of dissolved copper in the oil increases dielectric losses, while copper deposition significantly improves the conductivity of the paper insulation. Various factors, including temperature, oxygen, sulfur groups, passivators, and ageing time, have been found to contribute to the acceleration of corrosion activity in transformer insulating oils. Unfortunately, there is a lack of extensive research focused on systematically analysing and measuring the impact of corrosion-related factors on the dissolution of copper in transformer insulating oils and the deposition of copper onto solid insulation surfaces (Kraft paper). Therefore, this study aims to thoroughly examine the effects of corrosion factors on copper and sulfur deposition on Kraft paper insulation when it is submerged in transformer mineral oil (TMO). Using a two-level (2k) factorial design, we investigated three crucial factors: i) oil temperature, ii) elemental sulfur concentration, and iii) ageing time. It is worth mentioning that the results obtained from the two-level factorial design indicate that the surface resistivity is primarily affected by the temperature of the oil. This factor alone explains a significant 38.68% of the observed variation. In order to improve predictability, a regression model was created to estimate the surface resistivity of TMO-impregnated paper insulation. This model takes into account factors such as oil temperature, elemental sulfur concentration, and ageing time.

Effect of artificial aging on optical properties of ultra-translucent zirconia ceramics of different brands.

This work aimed to evaluate the effect of artificial aging on the translucency and color difference (ΔE) of ultra-translucent zirconia and provide a reference for clinical application. The discs of ultra-translucent zirconia from six brands (Wieland, 3M ESPE, Amann Girrbach, Kuraray Noritake, Upcera, and Besmile) were cut and sintered according to each manufacturer's product instructions; the experimental groups were named ZNT, LVP, AG, KAT, UPC, and BSM, respectively. IPS e.max Press was used as the control group (PLT). The specimens (n=6) were prepared with a diameter of 14 mm and a thickness of 1 mm. The specimens were subjected to artificial aging treatment according to the following conditions: in an autoclave at 134 ℃ at 0.2 MPa for 4, 8, and 12 h. According to the CIE1976Lab system, the CIE L*, a*, and b* values of the specimens before and after aging were measured by a co-lorimeter. The translucency parameter (TP) and ΔE were calculated. The mean TP values of each group before aging inorder were PLT>KAT>AG>ZNT>BSM>UPC>LVP. We found no significant difference in translucency in all experimental groups after aging for 4 and 8 h compared with those before aging. After 12 h of aging, the TP values of the KAT and ZNT groups were not significantly different from those before aging, but the TP values of the AG, BSM, LVP, and UPC groups were significantly lower than those before aging (P<0.05). The TP value of the control group was significantly higher than that of the other experimental groups at different stages (P<0.05). ΔE=3.3 was considered the visible color difference, and ΔE was less than 3.3 in all groups after 4 h of aging. After aging for 8 h, ΔE of the UPC group was slightly higher than 3.3. ΔE of the BSM and UPC groups was greater than 3.3 after 12 h of aging. The TP and ΔE of different brands of ultra-translucent zirconia may change after various aging times. The translucency of some zirconia showed a decreasing trend and the color difference showed an increasing trend with the aging time.