The creep behavior of HR3C austenitic steels was investigated at 650°C and over the stress range from 150 to 250MPa for up to 13,730h. The corresponding microstructure evolution was characterized by ...optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the initial stage of the creep process, the creep-resistance of HR3C steel is enhanced by the precipitation of second-phases particles in the grain and at the grain boundary. Compared with the precipitates inside the grain, the higher nucleation and growth rate of precipitates at the grain boundary is related to the higher interfacial energy and diffusion rate of atoms. The high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) results show that the precipitates inside the grain may initially nucleate at dislocation pile-up sites, and the interface coherency between the precipitate and the matrix can be destroyed after a long-term creep process. The TEM morphology indicates that the agglomerated tiny particles interact with the dislocations, contributing mostly to the precipitation strengthening inside the grain during the long-term creep process at 650°C, while the growth of chain-like M23C6 precipitates at the grain boundary increases the tendency of intergranular cracking as the creep time increased.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Stress/deformation-induced accelerated corrosion has been reported for many alloys used in structural and functional applications. To understand the effect of applied elastic stresses on corrosion ...behavior of alloys, samples of stainless steel (SS) 304 were subjected to different levels of elastic tensile stresses and their corrosion behavior was studied. The applied elastic stress is believed to alter materials' pitting behavior in chloride-containing environments. Results from this study show that applied tensile stresses hinder pitting resistance of SS304. Stress and stress concentration around pit vicinity accelerate salt-film repair, thereby impeding repassivation. Through this mechanism, pit growth is stabilized. Results from electrochemical tests on samples at different elastic stress levels are discussed in this paper.
Given the threat of environmental degradation and land deterioration to conventional agriculture, modern greenhouse cultivation has attracted increasing attention as an effective alternative. ...However, the high energy consumption of greenhouse systems is concerning given the need to limit the environmental impact of human activities. The solar integration to agricultural greenhouse in the form of modern solar greenhouse has the potential to simultaneously respond to the declining availability of suitable land and the imperative for minimum emissions. In this review, an overview of China's progress towards the development of modern solar greenhouses, as well as the attempts to mitigate the effects of heat loss, shadowing, and poor light condition is presented. A promising prospect is shown by China's modern solar greenhouses at present levels of performances and costs exemplified by the photovoltaic (PV) greenhouses with a practicable payback period of less than 9 years. Additionally, application of advanced solar technology for better thermal storage, PV power generating and light utilization balance has been proved effective to further promote solar energy utilization in modern solar greenhouses.
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Light‐weight, power‐free mechanochromic sensors that can change and record the reflective color depending on the magnitude and rate of the applied force are fabricated from inverse opals by ...infiltrating the colloidal crystals of silica particles with uncrosslinked SU‐8, followed by removal of the colloidal templates. The mechanical sensing range of the materials is high, 17.6–20.4 MPa. Due to elastoplastic deformation of the SU‐8 films, the deformed structures and thus colors can be locked after the removal of the load, therefore establishing a quantitative relationship between the mechanical force and optical responses. In comparison, mechanochromic photonic gels reported in the literature typically detect force in the range of 10–100 kPa; once the load is removed, the structure and color return back to the original ones. The mechanochromic sensors are highly sensitive: the ratio of shift in the stopband wavelength to the change in applied strain is up to 5.7 nm per percent, the highest among literature. Comparison of finite element simulations with experiments confirms the elastoplastic deformation of the films and highlights that reconfiguration of pore shape under compression plays a key role in the mechanochromic response.
Power‐free and highly sensitive mechanochromic sensors that can quantitatively measure the magnitude of mechanical force are prepared from uncrosslinked SU‐8 inverse opals. They can record impact forces by exhibiting different visible colors depending on the amount and rate of the applied forces. Experiments and finite element simulations attribute this to the elastoplastic deformation of the crystals.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The human-centered body sensor network (BSN) becomes one of the Internet of Things (IoT) development directions in the future due to interdisciplinary advantages in the fields of wireless ...communication technology, embedded microelectronic technology, and mobile Internet technology. Only depending on the terminal perception and transmission technology is not enough to make up the weak data storage, computing, and analysis capacity. Thus, in combination with green sensors, smart clouds computing, artificial intelligence technology, and BSN, this paper proposes a concept of green cognitive BSN (Green-CBSN). Starting from the three aspects including green active sensor, energy harvesting and efficient data collection, and health big data recognition and interaction, this paper introduces the architecture and thought of Green-CBSN in detail. Then, we invite some volunteers equipped with wearable devices, such as smart clothing and smartphone, and carry out the physiological signal collection, heart rate monitoring, and physiological data emotion analysis experiments of electrocardiograph and photoplethysmography. At last, this paper summarizes the open issues and research directions about IoT security, health big data recognition algorithm optimization, and energy saving and green energy harvesting, to provide the reference for Green-CBSN.
Angle-independent structural colors obtained from colloidal nanoparticles (NPs) are of interest for potential applications in displays, color printing, 3D printing, and direct writing. However, it ...remains challenging to prepare uniform structural colors that can be directly written from colloidal inks that not only have no coffee-ring effect, but also have ultrasmooth film thickness, which will be important for layer-by-layer stacking. Herein, we synthesize polypyrrole (PPy) black coated silica NPs that have a low coverage (∼10.7 wt%) of bumpy PPy nanogranules (10-30 nm in diameter). When the PPy@silica NPs are drop-cast on a substrate, the surface roughness of the PPy@silica NPs effectively suppresses the coffee-ring effect and center aggregation during the drying of the colloidal ink, leading to ultrasmooth surfaces with sub-micron thickness and uniform structural colors with wide viewing angles. The color can be fine-tuned by the size of silica NPs, and the presence of PPy black significantly enhances the color contrast by suppressing incoherent and multiple light scattering. Moreover, we show that the bumpy colloidal ink is very versatile: the ink can be formulated from both low and high surface tension liquids as solvents and applied to a hydrophilic or hydrophobic substrate. We demonstrate direct writing of uniformly colored lines and three different color drops stacked on top of each other.
Graphene has been considered an extraordinary platform for electronic applications, while it still remains a challenge to fast synthesize large single-crystalline graphene (LSCG) for widespread use. ...Since the adsorption energy of single carbon on the substrate plays an important role in the nucleation and growth of graphene, we have considered adjusting its adsorption energy to synthesize LSCG. Here, our density functional theory (DFT) calculations expose that oxygen can significantly reduce (∼1.03 eV) the adsorption energy of single carbon on oxygen-covered Cu compared with the bare Cu. Motivated by the calculation result that oxygen can induce weaker carbon adsorption energy, the sequential double oxygen passivation method through chemical vapor deposition is proposed to successfully grow the millimeter-scale single-crystalline graphene with the rate of about 100 μm min−1. This approach could provide a new sight into fast synthesizing LSCG facilely and economically.
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The effect of thiosulfate addition on the metastable pitting behavior of stainless steels 304L (UNS S30403) and lean duplex stainless steel (LDX2101, UNS S32101) in 0.6 M NaCl solution was studied. ...It was found that metastable pits initiate preferentially on the ferritic phase of S32101. Current transients during potentiostatic polarization were used to study the pitting behavior of the tested steels. Statistical analysis of peak current, growth time, and occurrence time of the metastable pitting events was used to evaluate pitting behavior. From the distribution curves of these parameters, it was concluded that the addition of thiosulfate stabilizes metastable pit growth and promotes pitting kinetics in chloride solution. This effect is more pronounced for 304L compared to S32101.
The effect of quench polish quench (QPQ) nitriding temperature on the microstructure and wear resistance of SAF2906 duplex stainless steel was investigated. Results showed the surface of the nitrided ...samples was composed of an oxidized layer, a loose compound layer, a compact compound layer, and a diffusion layer. The oxidized layer was composed of Fe3O4. The main phases of the loose compound layer were CrN, αN, Fe2–3N, and Fe3O4. The compact compound layer was composed of CrN, αN, and Fe2–3N. In the diffusion layer, CrN and expanded austenite (S) were the main phases. The nitrided layer thickness increased from 20 to 41 μm with an increasing temperature of 570 to 610 °C. When the nitriding temperature was above 590 °C, the precipitates in the diffusion layer became coarsened, and their morphologies gradually changed from spherical particulate to rod-like and flocculent-like. Tribotests showed the cumulative mass loss of QPQ-treated samples was much lower than that of the substrate. The cumulative mass loss of the samples nitrided at 610 °C was higher than that at 570 °C during the first 29 h. When the test time was over 29 h, the former was lower than the latter.
The mass transfer in metal-assisted chemical etching between the interfaces has been revealed directly by an epoxy protection method. The results show that the dissolution of Si occurs in the Au film ...surface instead of the Au-Si interface. A mass transfer path inside the Au film is proposed, in which the Si atoms dissolve in the Au film, and then diffuse across the Au lattice, and are oxidized and etched away at the Au film/solution interface. This model is proved by the oxidation products of Si atoms (SiO
2
and SiF
6
2−
) on the surface of the Au thin film. In addition, the abnormal emission of H
2
at the Au-Si interface indicates the probability of the diffusion of H atoms inside the Au film during the etching. This work provides a further insight into the mechanism of metal-assisted chemical etching.
The mass transfer during the initial etching process: Si atoms dissolve in the Au film, and then diffuse across the Au lattice, and are oxidized and etched away at the Au film/solution interface.
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