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This study investigates the mechanical, fatigue, water absorption, and flammability properties of polyethylene terephthalate (PET) core-pineapple fiber sandwich composites reinforced with silane-treated neem fruit husk (NFH) biosilica additives. The novel approach includes modifying the fiber’s surface and incorporating biosilica to enhance environmental resistance. The composites were prepared using a hand layup method, followed by silane treatment of the biosilica, pineapple fiber, PET core and vinyl ester resin. Subsequently, to evaluate environmental impacts on composite’s performance, sandwich composites were subjected to temperature aging at 40^∘C and 60^∘C in a hot oven for 30 days and warm water aging at the same temperatures in tap water with pH 7.4. According to the results, adding 1%, 3%, and 5 vol.% silane-treated biosilica significantly improved the mechanical properties. The composite with 3% biosilica (L2) showed a tensile strength of 120.8MPa, flexural strength of 194.4MPa, compression strength of 182.4MPa, rail shear strength of 20.21MPa, ILSS of 23.14MPa, hardness of 85 Shore-D, and Izod impact strength of 6.56 J. Even under temperature and water aging conditions, the composites showed only minimal reductions in properties, highlighting the efficacy of the silane treatment. The temperature-aged L2 composite had a tensile strength of 104MPa, flexural strength of 172.8 MPa, compression strength of 164MPa, and ILSS of 22.5MPa, while the water-aged L2 composite exhibited a tensile strength of 96MPa, flexural strength of 152.8MPa, compression strength of 146.4MPa, and ILSS of 21.4MPa. Scanning electron microscope (SEM) analysis confirmed uniform dispersion of biosilica particles, critical for improved performance, though higher concentrations led to agglomeration and stress points. The composites also demonstrated excellent flame retardancy, maintaining a UL-94 V-0 rating with decreased flame propagation speeds, specifically 9.05mm/min for L2. These findings underscore the potential of silane-treated biosilica as a reinforcing additive to enhance the durability and performance of composites in adverse conditions.

We study the combined effects of aging and links removal on epidemic dynamics in the Barabási–Albert scale-free networks. The epidemic is described by a susceptible-infected-refractory (SIR) model. The aging effect of a node introduced at time t_i is described by an aging factor of the form (t-t_i)^-β in the probability of being connected to newly added nodes in a growing network under the preferential attachment scheme based on popularity of the existing nodes. SIR dynamics is studied in networks with a fraction 1-p of the links removed. Extensive numerical simulations reveal that there exists a threshold p_c such that for p≥p_c, epidemic breaks out in the network. For p<p_c, only a local spread results. The dependence of p_c on β is studied in detail. The function p_c(β) separates the space formed by β and p into regions corresponding to local and global spreads, respectively.

Investigated in this study are precipitate evolution with and without addition of W, Co, and B in two kinds of 9-12% Cr steels (named as A and B) used for power plants after various aging time and temperature using OM, SEM, TEM, etc. Three kinds of precipitates (Cr-rich M₂₃C₆, Nb-rich and V-rich MX, W-rich and Mo-rich Laves phase) were observed and investigated in the two alloys. Upon aging, the area fraction of M₂₃C₆ increased whereas that of Laves phases decreased despite of increase in size. The area fraction of W-rich Laves phase was much higher than that of Mo-rich Laves phase, indicating that W addition, compared to that of Mo addition, is more powerful in the formation of Laves phase precipitation (specimen A). The martensitic microstructure of specimen B was more stable than that of specimen A due to the addition of cobalt and boron. The tensile test and impact test were measured and studied in relation to the long term aging effect.

The precipitation phenomena and the related hardening in an Al–Cu–Mg–Si alloy were studied by calorimetry, X-ray diffraction analysis and microhardness measurements. The main calorimetric peaks were identified to be due to β^′′, θ′ and Q′ phases precipitation. The hardening during aging at room temperature and 160°C, was respectively, explained by atomic clusters and GP zones formation and by GP zones and β^′′/θ′ phases coprecipitation. Although the mechanical properties variation during aging at 200°C is simple, the corresponding microstructural evolution is complex: on the basis of the DSC results, the increasing of microhardness values, is mainly due to the coprecipitation of GP zones and β^′′/θ′ phases, however, the maximum hardening is explained by the coexistence of β^′′/θ′ and θ^′′ phases. Another important conclusion is that during aging at 160°C and 200°C, the θ′ phase is essentially developed from GP zones.

The microstructures and mechanical properties of as-extruded Mg–2.3Zn–0.18Y–$x$Zr ($x$ = 0.03, 0.06 and 0.13 at.%) alloys and aged Mg–2.3Zn–0.18Y–0.13Zr alloy were studied. The results revealed that the microstructures of as-extruded Mg–2.3Zn–0.18Y–$x$Zr alloys are typical bimodal structures. The coarse $\alpha$-Mg grains are surrounded by fine dynamically recrystallized $\alpha$-Mg grains. The average size of $\alpha$-Mg grains decreases with increasing Zr content. Moreover, the addition of Zr (at.%) can improve the mechanical properties of alloy. The as-extruded Mg–2.3Zn–0.18Y–0.13Zr alloy has the best mechanical properties with ultimate tensile strength (UTS) and yield strength (YS) of 346 MPa and 292 MPa, respectively, and an elongation of 26.7%, which can be attributed to the grain refining effect and precipitate strengthening. The UTS and elongation of Mg–2.3Zn–0.18Y–0.13Zr alloy changed slightly after aging treatment, but the YS increases remarkably, with the maximum increase of 30 MPa. The fracture surfaces of all alloys consist of many tearing ridges and dimples.

This paper’s aim is to describe the results of the phase transformation of BCuAl₉Fe₄ alloy after casting, quenching and aging. After casting, the microstructure of this alloy consists of $\alpha$ phase with grain size about 100 $\mu$m, mixture $(\alpha +\gamma )$ and the inter-metallic phase Fe₃Al. However, the proportion of the $\alpha$ phase in the casting alloy is coarse. The alloy was heated at $850^{\circ }$C for 2 h then quickly cooling in water. After quenching, the microstructure of alloy shows that the grain size reduced to about 40 $\mu$m. After quenching, the alloy was aged at $350^{\circ }$C for 2 h, the martensite phase of this alloy decomposed into order phase ($\alpha +{\gamma }_2)$ with fine grain size, dispersed in the matrix. The intermetallic phase was fine and evenly dispersed in the matrix. By TEM analysis, after heat treatment, the structure of martensite and the inter-metallic phase in this alloy which had small grain size were formed.

The aging behavior of the random n-vector model with long-range interaction decaying as r^-(d+σ) (where d is the dimensionality), is investigated by the theoretic renormalization-group approach. The system initially disordered at a high temperature is firstly quenched to the critical temperature T_c and then released to an evolution with model A dynamics. The aging properties are studied by the short-time expansions. The scaling behavior of two-time response and correlation functions are obtained in a frame of the expansion in ∊ = 2σ-d. In dimensions d < 2σ, the long-time limit of the critical fluctuation dissipation ratio X^∞ is calculated up to one-loop order. The simulation of X^∞ is discussed.

A series of Y₂O₃ nanoparticles of average particle size 19–37 nm are synthesized by a glycine-nitrate method. Room temperature ferromagnetism is observed in all samples. The magnetization of these samples decreases with increasing annealing temperature, showing a size-dependent ferromagnetism. Vacuum-heating effect on the ferromagnetism is also investigated, which indicates that the observed ferromagnetism is possibly associated with oxygen defects. Interestingly, an aging behavior of the ferromagnetism is observed when the sample is exposed to air or immersed in ethanol. These results further support the oxygen-vacancy-mediated ferromagnetism mechanism.

The effect of thermal heat treatment on the mechanical and electrical properties of Cu–Ag alloys was investigated. The homogenization heat treatment leads to an increase in tensile strength and a decrease in electrical conductivity due to dissolution of Ag into copper matrix. Also, it is shown that electrical conductivity of as-cast Cu–Ag alloys decreases with increasing Ag content. In contrast, the aging heat treatment gives rise to increase both the tensile strength and electrical conductivity because the Ag solute diffuses out from copper matrix during aging heat treatment. Therefore, it can be mentioned that the electrical conductivity of Cu–Ag alloys depends on Ag solute in copper matrix. Also, aging treatment is favorable to acquire high strength and high electrical conductivity.

This paper investigates the impact of heat input and post-weld aging behavior at different temperatures on the laser paper welded maraging steel grade 250. Three different levels of heat inputs were chosen and CO₂ laser welding was performed. Aging was done at six different temperatures: 360${}^{\circ }$C, 400${}^{\circ }$C, 440${}^{\circ }$C, 480${}^{\circ }$C, 520${}^{\circ }$C and 560${}^{\circ }$C. The macrostructure and microstructure of the fusion zone were obtained using optical microscope. The microhardness test was performed on the weld zone. Tensile tests and impact tests were carried out for the weld samples and different age-treated weld samples. Fracture surfaces were investigated by scanning electron microscopy (SEM). Microhardness values of the fusion zone increased with increasing aging temperature, while the base metal microhardness value decreased. Tensile properties increased with aging temperature up to 480${}^{\circ }$C and reduced for 520${}^{\circ }$C and 560${}^{\circ }$C. This was mainly due to the formation of reverted austenite beyond 500${}^{\circ }$C. XRD analysis confirmed the formation of reverted austenite.

Different time-dependent mechanisms such as creep, environmental surface oxidation or internal material degradation due to aging and irradiation will subject structures to the possibility of premature failures. In this paper a micro-scale finite element mesh consisting of multiple elements encased in ~50–150μm sized grains with designated grain boundaries is used to replicate shapes and dimensions to simulate an isotropic metallic microstructure. The grains are encased in pseudo-grain boundary element sets which can have different material and damage parameters compared to the grains. In this type of mesh random crack paths for intergranular and transgranular cracking conditions are allowed. It is shown that creep cracking using a uniaxial ductility constraint-based model coupled with a functionally distributed time-dependent environmentally assisted corrosion/oxidation/material degradation damage model acting on surface or internally can be realistically predicted using this model. It is also evident material properties input data have scatter especially at the sub-grain level where the measurement methods are new and not always standardised. This is dealt with in the model by employing a normal distributive probabilistic method to allow for statistically varied random damage and crack growth development. In this way it is possible to take into account the inherent variability in material input properties at the analysis stage without the need to change material properties following each run. The method could negate the need for knowing the exact material properties, which in any case is impossible to derive at the microstructural level, as results of each run can be varied using a statistically distributed critical damage criterion specified for each element.

The pseudoelastic behavior of a Co₄₉Ni₂₁Ga₃₀ ferromagnetic shape memory alloy under compression along [100] has been studied in the temperature range 300–500 K. In such a crystals, the effect of aging under a constant stress close to the critical stress to induce the martensitic transformation, produces its separation in two stages. This is due to the different ordering behavior of parent and martensite phases under aging. Increasing order of parent phase leads to a decrease of transformation temperatures, which in return leads to an increase in critical stress to induce the transformation. Aging of martensite produces its stabilization — increase in transformation temperatures. It is remarkable that this stabilization has a very slow recovery, as compared to other alloys systems, such as Cu-based shape memory alloys.

Precipitation hardening is an effective way to improve the functional stability of NiTi shape memory alloys. The precipitates, mainly Ni₄Ti₃, could be introduced by aging treatment in Ni-rich NiTi alloys. However, the presence of Ni₄Ti₃ precipitates could disturb the transformation behavior, resulting in the multi-stage martensitic transformation (MMT). With the presence of MMT, it is difficult to control the transformation behavior, and thus limits the applicability of NiTi alloys. In this work, previous efforts on explaining the observed MMT are summarized. The difficulties in developing a unified explanation are discussed, and a possible way to avoid the MMT is proposed.

The aging degradation behavior of Fe-doped Lead zirconate titanate (PZT) subjected to different heat-treated temperatures was investigated over 1000h. The aging degradation in the piezoelectric properties of PZT was indicated by the decrease in piezoelectric charge coefficient, electric field-induced strain and remanent polarization. It was found that the aging degradation became more pronounced at temperature above 50% of the PZT’s Curie temperature. A mathematical model based on the linear logarithmic stretched exponential function was applied to explain the aging behavior. A qualitative aging model based on polar macrodomain switchability was proposed.

Ability of epitaxial perovskite oxide ferroelectric films to maintain a poled polarization state on a long-term scale is crucial for advanced devices employing such films. Here polarization relaxation with time, or aging, is experimentally studied in epitaxial capacitor heterostructures of PbTiO₃ sandwiched between SrRuO₃ and Pt electrodes. The relaxation obeys logarithmic time-decay for the time 10²–10⁵s after poling pulses. The decay is by factor $\sim$10 slower than that reported for polycrystalline films. Our experimental results show that existing models are insufficient for epitaxial films.

Ti–6Al–2Sn–4Zr–2Mo (Ti-6242), a near-$\alpha$ titanium alloy explicitly designed for high-temperature applications, consists of a martensitic structure after selective laser melting (SLM). However, martensite is thermally unstable and thus adverse to the long-term service at high temperatures. Hence, understanding martensite decomposition is a high priority for seeking post-heat treatment for SLMed Ti-6242. Besides, compared to the room-temperature titanium alloys like Ti–6Al–4V, aging treatment is indispensable to high-temperature near-$\alpha$ titanium alloys so that their microstructures and mechanical properties are pre-stabilized before working at elevated temperatures. Therefore, the aging response of the material is another concern of this study. To elaborate the two concerns, SLMed Ti-6242 was first isothermally annealed at 650${}^{\circ }\mathrm{\text{C}}\le T\le 1025^{\circ }$C and then water-quenched to room temperature, followed by standard aging at 595${}^{\circ }$C. The microstructure analysis revealed a temperature-dependent martensite decomposition, which proceeded sluggishly at $T\le 700^{\circ }$C despite a long duration but rapidly transformed into lamellar $\alpha +\beta$ above the martensite transition zone (770${}^{\circ }\mathrm{\text{C}}\le T\le 800^{\circ }$C). As heating to $T>\beta -\mathrm{\text{transus}}(993^{\circ }$C), it produced a coarse microstructure containing new martensites formed in water quenching. The subsequent mechanical testing indicated that SLM-built Ti-6242 is excellent in terms of both room- and high-temperature tensile properties, with around 1400 MPa (UTS)$+$5% elongation and 1150 MPa (UTS)$+$10% elongation, respectively. However, the combination of water quenching and aging embrittled the as-built material severely.

At the onset of post-implantation embryonic development, the specification of human primordial germ cells (hPGCs) marks the preparation to attain the totipotent state through the extraordinary features of extensive epigenetic reprogramming (in terms of DNA demethylation and chromatin reorganization), a mitochondrial bottleneck, and a characteristic gene regulatory network, which are in stark contrast with those of the somatic lineage. Together, they provide for the attribute of immortality to the germ cell lineage, reflecting their significance in transgenerational inheritance. Interestingly, these features are the antithesis of the several hallmark phenotypes of aging, which gradually accumulate in the somatic lineage over time. In this chapter, we discuss the salient features of hPGC development, the hallmarks of aging, the application of cellular reprogramming as a therapeutic route to rejuvenation, and the intriguing translational potential of the lessons learned from the immortal human germline lineage in the field of anti-aging research.

The computational model of heat conduction is deduced for external insulation system of the exterior wall by the variable controlling method. In the method, the thermophysical parameter is constant. The external insulation systems of EPS, XPS, PUR, and PF are analyzed with this model. The weaken state is computed after the external insulation systems have been constructed for several years. The study results show that the insulation ability of deferent systems are all weakened with increase of the service time. The weaken amplitudes are all more than 8%. And it is as more as 18.6% in the XPS system, which is 8% more than EPS system. There are many cracks in the anti-crack mortar. So, it is the key factor for the weaken behavior in XPS system.

The accelerated aging test of SBR-based absorption materials in heat seawater were carried in laboratory. The elongation at break of the materials in aging time was investigated. Two methods were adopted to forecast the life expectancy of the materials. Mathematical model was applied through MATLAB software programming to gain the forecasted life expectancy is 10.98y in seawater at 25 ℃. The time-temperature superposition method was applied to gain the life expectancy, which is 12.08y in seawater at 25 ℃.

Due to the demand for weight loss and energy saving, the need to manufacture automobile structural components from aluminum alloy sheets is apparent. Hot stamping technology has been developed to form complex parts of aluminum alloys. However, the longtime solution and aging of aluminum alloys is still a challenge. Aiming at this goal, the effects of solution temperature and time on the mechanical properties of 6061-T6 aluminum alloy were studied. The results showed that solution temperature had a significant effect on the solution process and solution heat treated at 560 °C for 10 min was recommended. Then the negative natural aging effect (keeping effect) of 6061 was also investigated and it indicates that artificial aging must be carried out within 3 hours after quenching. Finally, novel heating methods were employed in the solution and aging process to achieve an efficient hot stamping process. The results showed that parts with good mechanical properties can be obtained by solution at 560 °C for 5 min and aging or pre-aging at 192 °C for 5∼10 min with the implementation of novel heating methods in hot stamping.