Longer Aging Times Research Articles

Effects of humidity, ionic contaminations and temperature on the degradation of silicone-based sealing materials used in microelectronics

This paper investigates the effects of three ageing factors (chemical, humidity, and temperature) and their interactions on the physical properties and degradation of silicone sealant used in microelectronic applications. The thermal degradation of silicone sealants was investigated by exposing samples to temperatures in the range of 150 up to 175 °C. Also, a set of samples were aged at 40 °C in a salt spray set-up with 100 % humidity in a salty atmosphere. Results showed detectable changes in the FTIR spectra of aged specimen as compared with the as-received sample. In all accelerated testing conditions, peak intensities decreased with ageing time, inferring that that the surface characteristics of the sealant is affected by ageing. Shear test results showed that with increasing the ageing time, the maximum shear stress in most cases has decreased in all ageing conditions. Also, it appears that samples with longer ageing times have experienced more elongation before failure. Results also show that salt spraying of specimens is associated with a decrease in the mechanical properties of the sealant, indicating the deleterious implications of ionic contaminations for the mechanical properties of samples.

Microstructural studies of Stellite 6 hardfacing deposited on nickel-based superalloys subjected to long-time aging

Microstructural studies of Stellite 6 hardfacing deposited on nickel-based superalloys subjected to long-time aging

Mechanical and dynamic characteristics for the CFRP, GFRP, and hybrid composites exposed to HCl environment

In the current study, the low-velocity impact (LVI) characteristics of carbon fiber-reinforced polymer (CFRP), glass fiber-reinforced polymer (GFRP), and hybrid composites before and after the corrosive environment exposure were investigated. In this regard, CFRP, GFRP, and hybrid composites were subjected to LVI and tensile loadings after being kept in a 10% diluted HCl environment for 1 week and 1 month, and the impacts of the corrosive environment on the composites’ dynamic and mechanical responses were determined by comparing the outcomes of the control and aged specimens. LVI tests for CFRP, GFRP, and hybrid composites were carried out by transferring 25.2 and 11.2 J impact energy to the specimens with two impact velocities of 3 and 2 m/s, respectively, and thus, the effects of impact energy and hybridization were investigated. Moreover, tensile tests were conducted for the control and aged specimens with 2 mm/min crosshead speed, and thus, the effects of fiber material, hybridization, and corrosive environment on the mechanical properties were determined. The study found that CFRP composites had higher stiffness than GFRPs, whereas hybrid composites exhibited dynamic responses between CFRP and GFRP, as expected. On the other hand, it turned out that the composites absorbed most of the impact energy, which was interpreted as being absorbed by the damage of fiber-reinforced composites, which stand out with their brittle characteristics. Furthermore, it was discovered that the damage severity elevated as expected with a longer aging time, which was attributed to the corrosive liquid attacking the fibers, matrix, and fiber/matrix interfaces and reducing strength. It was also observed that, as predicted, the corrosive effects generally resulted in a reduction in tensile responses, including ultimate strain and tensile strength.

Changes in the peel strength between the painting and first lining papers in Japanese scroll model samples

To maintain the permanence of a painting in a hanging scroll until subsequent repairs are made, inhibiting not only the deterioration of the painting and lining papers but also inhibiting decrease in the adhesiveness between them is important because the first lining process significantly influences the mechanical support to the painting paper by attachment. Several studies have been conducted on the deterioration attributed to each component of the lining system. This study evaluated the adhesiveness behaviour by peel strength in the lined complex depending on the painting and lining materials with varied concentrations, as well as the fibre type of the lining paper. The lined complex consisting of the untreated painting paper showed the highest initial peel strength owing to the significant cohesiveness of the wheat starch paste layer, which was attributed to the paper's higher wettability and permeability, even though substrate failure occurred with longer ageing times. Degradative materials such as Cu2+ attributed to pigments in the painting paper decomposed starch and decreased adhesiveness the fastest. Lined complexes coated with animal glue containing alum or Cu2+ in the painting paper maintained the lowest peel strength during ageing owing to lower wettability and permeability, resulting in interfacial failure between the animal glue and the wheat starch paste layer. In addition, adhesiveness varied with different fibre types of the lining paper, depending on combined factors such as fibre length, surface roughness, shape, and intensity of hydroxyl groups. Thus, variable conditions attributed to fibre characteristics, materials used for lining, and degradative products in the painting paper influenced the changes in adhesion and adhesiveness. This variation contributed to different lining effects that influenced the life expectancy of the hanging scroll and determined the efficiency of the subsequent repair work.

A Bi-Pronged Attempt at Normalizing DL-EPRT Vis-à-Vis Grain-Boundary/σ-Phase Locales in Thermally Sensitized UNS S32205 Duplex Stainless Steel

In a quest to vet UNS S32205 as a potential structural material to serve moderate-to-high temperature operations of NPP auxiliary components, the DL-EPR test was exploited. A bifronted scheme comprised of 650 and 850 °C discrete treatments intended to explore progressive eutectoid decomposition and degree-of-sensitization (DoS) scenarios was adopted. The nuance witnessed with yet another dual approach—the Cihal- and image processing (IP)-normalized signal landscape—was rationalized through its attribution to culprit microstructures. This was sought, inter alia, in the vicinity of grain boundaries and σ-phase inclusions by virtue of postmortem FESEM, STEM-EDX, HRTEM SAED and XRD ascertainment. Discernable reactivation-kinetics resurgence was believed to mark the onset of deleterious σ-phase dissolution. This only came into fruition with longer ageing times (8–17 h) at 650 °C and succumbed to prematurely (1 h), and at DC biases more cathodic than −0.25 VAg/AgCl with the 850 °C counterpart. Opportune corroboration was offered in ir/ia breakaway for the respective conditions, which was unveiled to be particularly pre-emptive (5 h) with IP- vs. Cihal-normalized peers (8 h) related to the 650 °C condition. Meanwhile, the 850 °C condition endured a similar surge after as little as 1 h of ageing across the board, which hints at concomitant sigma-phase culpability.

The precipitation mechanism of the secondary phase in Inconel 617B alloy during ageing

ABSTRACT Precipitation of the secondary phase is a key factor that influences the strengthening effect of nickel-based superalloy. The precipitation behaviours of the M23C6 carbide and γ′-Ni3(Ti, Al) phase in Inconel 617B alloy aged at 700°C for different times were studied by scanning electron microscopy, transmission electron microscopy and atom probe tomography. Plate-like carbide nucleated in the interior of grain and irregular shape carbide precipitated at grain boundary respectively during the early stage of ageing. γ′ particle co-precipitated around carbide is a common microstructure feature during ageing for 5–160 h. After ageing for 160 h, γ′ phase is the main secondary phase. The carbide only distributes on the grain boundary, high density γ′ particle homogeneously distributes in the matrix after a longer ageing time. Elemental partitioning to the secondary phases and composition profiles across different phases was quantitatively analysed. Enrichments of Ti and Al at the carbide/γ interface are directly observed, which act as the nucleation site of γ′ particles during ageing. Enrichments of B, Si and Co at different interfaces are also detected. Based on the experimental results, the precipitation mechanisms of γ′ particles and carbide were discussed.

Large-Scale Analysis on Accelerated Aging of Pentaerythritol Tetranitrate (PETN) Powders in Detonators.

Pentaerythritol tetranitrate (PETN) has been used extensively in commercial detonators and other explosive applications for many decades. Here, we show the results of a comprehensive 1.5 year aging study of PETN in commercial detonators, addressing batch-to-batch variations, surface area changes, and comparisons of aged loose powders side-by-side with identically aged detonators. Function time analysis of the aged detonators has also been provided and discussed in the context of powder aging. This large-scale, statistically relevant study addresses long-standing questions on PETN aging without the complications from making comparisons between multiple batches of material. We have evaluated the aging time required to reach the maximum measured amount of PETN coarsening and estimated an activation barrier of ∼123 kJ mol-1, which is higher than literature values reported by Gee et al. It is possible that this discrepancy is due to the fact that that this study cannot quantify the relative contributions of surface diffusion versus sublimation processes. At the lower temperatures of 50 and 60 °C, we assume that surface diffusion dominates over sublimation processes, even at longer aging times. At the higher temperature of 75 °C, we assume that both surface diffusion and sublimation contribute at the early time points, which are included in the Arrhenius analysis for coarsening.

Synthesis of layered double hydroxides: Investigating the impact of stirring conditions and reactor design parameters

The synthesis by coprecipitation of Layered Double Hydroxides (LDHs) is governed by the stages of nucleation and crystal growth associated with the efficiency of the mixing and dispersion process of the reagents. Mixing efficiency is related to process variables, such as agitation speed, type of impeller and baffles presence, among others. In this context, this work proposes an analysis of these variables in a batch reactor, using a 23 factorial design employing the factors: acceleration speed (200 and 1000 rpm), mixing time (2 and 18 h) and presence or absence of baffles. The results were evaluated quantitatively (amount of LDH produced, time and amount of base for the formation of LDHs to begin) and qualitatively (mixing aspects, sedimentation ad grinding). The significant factors affecting the amount of LDH produced (51.94–80.81 g) were agitation speed and aging time. These factors were also correlated with the structural characteristics of the materials produced, such as crystallinity, crystallite size (70.99–174.79 nm), surface area (69.81–97.62 m2/g), pore volume (0.28–0.59 cm3/g), and pore diameter (11.40–34.66 nm). LDHs produced at higher agitation rates (1000 rpm) and longer aging times (18 h) yielded higher quantities of materials (80.81 g) with improved structural characteristics. The study highlights the importance of systematically exploring the synergistic effect between process variables, emphasizing the research potential in this area.

Formation and long-time exposure aging of oxides on Ni-Cr and Ni-Cr-X (X = Mo, W) alloys in acidic chloride solutions: Ramifications towards corrosion resistance

The passivation of Ni-22Cr, Ni-22Cr-6Mo, and Ni-22Cr-6Mo-3W (wt%) was characterized from 100 s to 10 days in 0.1 M NaCl in pH 4 at various potentials in the passive range. The influence of aqueous solution exposure time in NaCl (exposure aging), passivation potential, as well as Ni-Cr-X alloy composition (Mo or W) on passive film growth, composition, oxidation state, molecular identity, and inner versus outer film layering were investigated. Initial passive film formation was dominated by Ni(II). Cr(III) oxides and hydroxides tended to enrich upon formation and exposure aging. Corundum and rock salt are speculated to undergo a solid-state phase transformation to form NiCr2O4 at long times under certain conditions. The concept of the time-potential-transformation diagrams to describe the evolution of passive film phases and protectiveness is introduced. Factors limiting Cr(III) enrichment were discussed. Aliovalent Mo and W ions were detected in passive films, particularly after aging. The roles of Cr enrichment, Ni depletion, and Mo and/or W aliovalent cations after oxide aging towards protectiveness to passive and localized corrosion in chloride (Cl-) solutions were discussed.

Homogeneous Age-hardening of Large-sized Al-Sc Foams via Micro-alloying with Zr and Ti.

Al-based foams have drawn increasing attention from industry due to their integration of structure and functional properties. However, large-sized Al-based foams still cannot be homogeneously strengthened by long-time aging due to their low thermal conductivity. In this study, we proposed an age-hardening approach that was applied in large-sized Al-0.16Sc-0.17Zr (wt.%) foams via micro-alloying with Zr and Ti compared with Al-0.21Sc foams; it not only achieved homogeneous strength by long-term aging but also reduced the cost of the alloy by substituting Zr and Ti for the more expensive Sc content. The results show that the Al3(Sc, Zr, Ti) phase with a core-shell structure as a crucial precipitation strengthening phase by micro-alloying with Zr and Ti was less prone to coarsening after a prolonged aging heat treatment. Therefore, the yielding strength of Al-Sc foam micro-alloying with Zr and Ti remained almost unchanged after a maximum aging time of 1440 h due to less coarsening precipitate, which is consistent with the results of mechanical experiments. These findings provide a new way for the heat treatment strengthening of large-sized Al-based foams, thus promoting their industrial applications.

Analysis and identification of degradation products in gas, particle, and liquid phases of polypropylene and polyethyleneterephthalate microplastics aging through non-thermal plasma simulation.

Plastic aging can cause alterations in the physical and chemical characteristics of plastics, as well as their behavior in the environment. Due to the extremely slow natural aging process, laboratory simulated aging methods have to be used. In this study, non-thermal plasma (NTP) was adopted to investigate the aging process of polypropylene (PP) and polyethylene terephthalate (PET) microplastics. Various analytical instruments, including proton transfer reaction mass spectrometry and single-particle aerosol mass spectrometry, were employed to examine and identify the organic constituents of the gas, liquid, and particle phase degradation products, as well as to monitor the degradation process. The results showed that after 90min of aging, both PP and PET surfaces showed yellowing, and the carbonyl index of PP increased while that of PET decreased, with an increase in crystallinity. The organic components of reaction products, such as ketones, esters, acids, and alcohols, increased with longer aging times. Gas products mainly contain aromatic hydrocarbons, while particles from aged PET contain compounds with benzene rings and metal elements. Liquid products from aged PP show a significant presence of branched alkanes. Based on this analysis, degradation mechanisms of PP and PET by NTP were proposed. This investigation represents the initial systematically exploration of the release of organic substances during the degradation of microplastics mediated by NTP. It provides significant insights into the detrimental organic compounds emitted during this process, thereby offering valuable information for understanding the environmental and human health implications of natural microplastic degradation. Furthermore, it addressed the requirements for increased attention to the potential environmental risks associated with these harmful components.

The Influence of Heat Treatment on Microstructure and Properties of Selective Laser Melting CuCrZr Alloy

The effects of different heat treatment processes on the properties of selective laser melting (SLM) CuCrZr alloy are investigated toenhance its overall performance. Solution treatment (ST) results in recrystallized grains, leading to an increase in electrical conductivity to 45.36% IACS and a decrease in tensile strength to 221.8 MPa compared to SLM CuCrZr alloys. Solution aging treatment (SAT) further improves the conductivity to 83.12% IACS and the tensile strength to 335.6 MPa. The optimal combination of electrical conductivity (72.82% IACS) and tensile strength (611.3 MPa) is achieved through direct aging treatment (DAH) at 480 °C for 2 h. With increasing aging temperature and time, the electrical conductivity initially increases rapidly and then plateaues, while the tensile strength exhibits an initial increase followed by a decrease. The proportion of precipitated phase gradually increases with longer aging time. Coherent precipitation occurs between the phase and the matrix at 480 °C for 120 min, while at 480 °C for 360 min, both face‐centered cubic and body‐centered cubic precipitates coexist with an incoherent relationship with the matrix. Overall, DAH proves effective in enhancing the properties of SLM CuCrZr alloy, with precipitation strengthening serving as the primary mechanism for improving its performance.

Formation of secondary organic aerosol from wildfire emissions enhanced by long-time ageing

Formation of secondary organic aerosol from wildfire emissions enhanced by long-time ageing

Solid/solid state interfacial reactions in the lead-free solders/Cu- 2.3%wt. Fe alloy (C194) couples

BackgroundLead-free solders (LFSs) involve incorporating trace elements into Sn, resulting in alloys like Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and Sn-0.7 wt.% Cu (SC). These solder have similar properities to Sn-Pb solders. C194, renowned for its exceptional corrosion resistance, high strength, and good weldability, serves as a preferred lead-frame material in electronic packaging. In this study, we investigated the solid/solid state interfacial reactions between the LFS and Cu-2.3 wt.% Fe alloy (C194). MethodsThree LFS including Sn, SAC, and SC were first reflowed with C194 to form the LFS/C194 couple. Then the LSF/C194 couples were aged at 125–175 ℃ for 100–2000 h. Significant findingsThe results revealed that only the (Cu, Fe)6Sn5 phase was formed in the Sn/C194 couple aged at 125 ℃. At higher temperatures and longer aging times, the (Cu, Fe)3Sn phase was formed in all three couples. The Fe addition into Cu could inhibit the (Cu, Fe)3Sn phase growth. Kirkendall voids in this study occur more frequently with the increase in aging temperatures and times, but the intensity varies in each system. Meanwhile, the thickness of total intermetallic compound (IMC) was increased with the increase in aging times and temperatures in these three couples. The IMC growth mechanism is diffusion controlled in all LFSs/C194 couples.

The effects of aging time on the sol-gel properties and its relationship with the anti-corrosive performance of coatings prepared by sol-gel dip coating

This work evaluated the changes in the physicochemical properties (viscosity, surface tension, and zeta potential) of both alumina sol and boehmite solution at different aging times and their relationship with the corrosion resistance (in a saline solution) of the alumina film/boehmite conversion coating/carbon steel substrate systems prepared by sol-gel dip coating. The boehmite solution did not show significant changes in physicochemical properties throughout the studied time. As a result, the electrochemical behavior of the coating systems was independent of the aging time used to pretreat the substrate with the boehmite solutions. On the other hand, the changes in the physicochemical properties of the alumina sol with age were observed since the second week, causing an increase in the thickness (from 3.06 to 5.10 μm) and a decrease in the global resistance (from 138 to 30 kΩ cm2) of the systems. The most intense solvent evaporation effect and the macromolecules formed due to hydrolysis and condensation reactions during the studied aging period affected the properties of the alumina sol, leading to more heterogeneous and defective films when produced from sols with longer aging times.

Minor additions of Sn suppress the omega phase formation in beta titanium alloys

A critical characteristic of β-Ti alloys is the inevitable formation of ω-precipitates during certain heat treatments which leads to embrittlement, or even to a complete loss of ductility. Therefore, alloy design with the goal to inhibit the elementary ω-formation process is of utmost importance. Here, we propose a design strategy for prototypical β-type Ti–Cr–(Mo) alloys to alleviate this problem using only minor additions of Sn. Upon addition of Sn, we observed an extensive deceleration or even suppression of the ω-formation kinetics during isothermal ageing. Furthermore, the internal friction response of the elementary formation process indicated a decisive reduction of potential ω-nucleation sites, while the activation energy of the process remained almost unchanged. The results show, that the addition of Sn can significantly increase the width of the time–temperature process window and the long-time ageing resistance of β-Ti alloys, opening up huge opportunities for advanced alloy design and manufacturing routes.

Влияние сухого созревания на белки мышечной ткани говядины

Meat is an inherent part of human diet. Its quality develops at different stages of production, storage, and processing. In this respect, the stage of aging is especially important. This technology makes it possible to regulate biochemical processes in meat raw materials. Long-term dry aging is a promising method that presupposes conditions that limit the growth of microorganisms. The transformations in the protein component are an important but understudied aspect of meat quality formation during dry aging.
 The research featured Hereford beef carcasses of Siberian breeding. The samples were isolated from the inner part of bone spinal-lumbar cuts after 21, 35, and 42 days of dry aging under the following conditions: 0–1°C, 74–75% relative humidity, 0.5 m/s air velocity. The samples were subjected to dry aging after 24 h at 4°C. The fractional composition of proteins was controlled by vertical electrophoresis in a Mini-Protean Tetra System chamber. The amino acid composition was defined by high-performance liquid chromatography in a Shimadzu LC-20 Prominence liquid chromatograph with a Shimadzu SPD20MA diode-matrix detector and a Kromasil C-18 separation column. The protein digestibility was measured by sequential exposure to pepsin-trypsin proteinase system under simulated gastric digestion.
 Long-time dry aging triggered proteolysis under the action of endogenous enzymes. The electropherogram analysis showed that the proteolytic changes in high-molecular myofibrillar proteins of high-quality beef became more pronounced after a longer maturation period. The distribution of protein fractions by dry aging stages indicated a different rate of degradation of contractile, regulatory, and cytoskeletal proteins. As a result, the structural integrity of muscle fibers degraded, the meat grew tender, and the proteins became more available to digestive enzymes. The amino acid and protein digestibility analyses in vitro demonstrated an increase in the nutritional value of beef and the availability of proteins to the action of proteinases after 42 days of dry aging.
 Long-term dry aging of high-quality beef increased the digestibility of muscle proteins as a result of proteolysis that accompanied the accumulation of low-molecular fractions. According to the amino acid analysis, the optimal result was most pronounced on day 42 as proven by the moderate oxidative changes in proteins.

Effect of sintering temperature and low-temperature aging on microstructure and flexural strength of Fe2O3-doped 3Y-TZP ceramics fabricated by stereolithography-based additive manufacturing

In this study, the effects of sintering temperature and low-temperature degradation (LTD) on the microstructure and flexural strength of 0.06 wt% Fe2O3-doped 3Y-TZP ceramics fabricated via stereolithography-based additive manufacturing were evaluated to assess their suitability for dental applications. The ceramics' comprehensive properties, including density, microstructure, phase composition, and three-point flexural strength, were analyzed over a range of sintering temperature from 1400 °C to 1600 °C. The findings revealed that specimens sintered at 1500 °C exhibited the highest density (6.03 g/cm3), a uniform microstructure, and superior mechanical properties (911.54 MPa). However, sintering temperatures above 1500 °C led to abnormal grain growth and martensitic transformation of tetragonal zirconia to the monoclinic phase, resulting in reduced density and material degradation. To investigate the effects of LTD on the phase structure, microstructure, and flexural strength, the specimens sintered at 1500 °C were subjected to LTD tests at 134 °C and 2 bar for 5, 10, and 20 h, respectively. The results demonstrated an increase in the m-phase content from 2.58 wt% to 21.89 wt% on the ceramics' surface. Atomic force microscopy observations revealed a gradual increase in the m-phase grain with longer aging time. Meanwhile, the flexural strength decreased but remained within the required range for dental restorations. In conclusion, the specimens fabricated via stereolithography-based additive manufacturing and sintered at 1500 °C for 4 h demonstrated high mechanical properties and good LTD resistance. These findings, in conjunction with the positive aesthetic properties obtained in previous studies, highlight their potential as a promising material for dental applications.

Effect of Zn(TFSI)2 on the performance-aging time of perovskite solar cells

Hole transport layers (HTLs) are one of the essential layers of perovskite solar cells (PSCs). Generally, 2,2ʹ,7,7ʹ-Tetrakis [N,N-di(4-methoxyphenyl)amino]-9,9ʹ-spirobifluorene (spiro-MeOTAD) doped by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as the HTL in PSCs. PSCs employing spiro-MeOTAD require an additional aging process to reach an optimized point of photovoltaic performance due to doping and energy alignment. However, LiTFSI is responsible for low thermal stability and has a hygroscopic nature; therefore, Zinc(II) bis(trifluoromethanesulfonyl)imide (Zn(TFSI)2) has been reported as an outstanding candidate to replace LiTFSI. Nevertheless, utilization of Zn(TFSI)2 as a dopant for PSCs has rarely been reported, which is likely due to the difficulty in achieving high device performances comparable to that with LiTFSI. Herein, we investigate the effect of Zn(TFSI)2 on the doping kinetics of spiro-MeOTAD and correlate it with the time-dependent photovoltaic performance of PSCs employing Zn(TFSI)2. Devices with Zn(TFSI)2 require a considerably longer aging time (∼270 h) to reach the optimized performance, while LiTFSI takes only ∼20 h due to the different doping kinetics of spiro-MeOTAD depending on the dopant. Remarkably, engineering at the interface of the perovskite/HTL can effectively shorten the device aging time by manipulating the recombination rate, leading to a comparable aging time to LiTFSI.

Why does distilled liquor has a soft and harmonious flavor after long-time ageing? A thermodynamic analysis

The effect of acid–ester equilibrium on the quality of aged distilled liquor (e.g., Baijiu) and techniques for the rational design of flavor are yet to be fully understood. In terms of thermodynamics, the long-term ageing is a spontaneous process in which the thermodynamically unstable state changes to the stable state. This study used gas chromatography, sensory evaluation, and thermodynamic strategies to explore the acid–ester equilibrium during the ageing process of Baijiu. The content of most esters in new Baijiu is significantly higher than that of acids and a consistent rule in the ester balance was detected, with the reaction quotients of esterification reactions gradually approaching the equilibrium constants. The thermodynamic data confirm that the contents of esters and acids become stable after ageing. And the stability of ester and acid content is the premise of the soft and harmonious flavor of Baijiu: after ageing, the Baijiu will keep its harmonious flavor which derives from the blending process. On the contrary, the blended but unaged Baijiu, will lose the harmonious flavor due to the change of the content of esters and acids.