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To explore the synergistic wettability of the Ti-Cu-Fe multi-metal system, the wetting behaviors of CuSi3 droplets on the TC4 and 304SS plates during the cold metal transfer welding process in various gas atmospheres were studied ...
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To explore the synergistic wettability of the Ti-Cu-Fe multi-metal system, the wetting behaviors of CuSi3 droplets on the TC4 and 304SS plates during the cold metal transfer welding process in various gas atmospheres were studied in this work. The effects of Ti, Fe, Si, C, and O on the spreading dynamics of liquid Cu were analyzed in detail. The results reveal that the CO2 + Ar hybrid gas shielding atmosphere significantly affects the interfacial mass transfer. The sufficient interfacial reaction and increased element diffusion promoted the formation of Ti2Cu/TiCu multiphase microstructure at the Cu/Ti interface instead of a continuous Ti2Cu layer, and a thicker and loose Fe (s, s) layer was formed at the Cu/Fe interface. The variations of surface phase composition and the generation of inward flow weakened the wettability of CuSi3/TC4 and CuSi3/304SS systems. The dissolution of Si and surface adsorption of O decreased the sigma lv of liquid Cu, whereas Ti and Fe had the opposite effect. When the shielding gas changed from pure Ar to CO2 + Ar hybrid gas, the potential spreading model of the CuSi3/TC4 system changed from reaction-limited to diffusion-limited, and the wetting activation energy increased from 46 kJ/mol to 57 kJ/mol. Removing oxide film, forming Ti2Cu and diffusion of Ti controlled the wetting. Whereas for the CuSi3/304SS system, the potential spreading model changed from diffusion-limited to a molecular dynamics model. Removing oxide film, diffusion of Fe and interfacial adsorption were the dominant factors for wetting.
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In this paper, a novel arc oscillation welding method, namely, the arc oscillation along the welding direction with the aid of alternating magnetic field, is adopted to weld thin-walled 2205 duplex stainless steel in autogenous mo...
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In this paper, a novel arc oscillation welding method, namely, the arc oscillation along the welding direction with the aid of alternating magnetic field, is adopted to weld thin-walled 2205 duplex stainless steel in autogenous mode. The oscillating arc can route some effects on the weld forming as well as the microstructure evolution of weld zone, which in turn affects the weld performance. The results show that such arc oscillation can alleviate the surface root sagging of the weld during the conventional GTAW process, and the improvement effect becomes more pronounced with the increase of excitation frequency. Simultaneously, the heat affected zone of the weld with magnetic field at a higher frequency becomes narrower. Based on the reheating effect of arc oscillation on the molten pool, gamma/alpha (austenite/ferrite) phase ratio in the weld zone are regulated. At an excitation frequency of 10 Hz, the weld with gamma/alpha ratio nearly 1:1 is obtained. Meanwhile, arc oscillation can manipulate the texture characteristics of weld microstructure, which follows that the higher the excitation frequency, the lower the texture density. Eventually, the strength and plasticity of the weld are improved synergistically at a higher magnetic field frequency in this work.
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Thermal interface materials (TIMs) play a crucial role in enhancing the reliability and sustainable utili-zation of next-generation electronics and thus can help meet the increasing demand for multifunctional devices with higher p...
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Thermal interface materials (TIMs) play a crucial role in enhancing the reliability and sustainable utili-zation of next-generation electronics and thus can help meet the increasing demand for multifunctional devices with higher performance. Herein, we introduce a method for creating a TIM with high cross-plane thermal conductivity based on graphite nanoplatelet (GNP)/polyurethane (PU) films. The graphite nanoplatelets ensured the heat transfer properties of the TIM. Moreover, the hot-pressing procedure improved the thermal conductivity to 26.3 W (m K)(-1) with the improved orientation of the GNPs in the PU matrix, as confirmed by microscopy investigation. Under a thermal dissipation power of 10-20 W, a drastic reduction in the chip temperature (17.5-42.3 degrees C) was achieved using our oriented GNP/PU TIM compared to a commercial silicone TIM (5.0 W (m K)(-1)). In addition, as-prepared pads can be mass produced at an acceptable cost, indicating that our work provides a promising new approach to fabricating TIMs for application in the next-generation thermal management of high power density electronics. (C) 2021 Elsevier Ltd. All rights reserved.
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The silicon coated Carbon nanotubes (CNTs) nanocomposite (CNTs@Si) with a shell structure was successfully synthesized by a simple chemical vapor deposition (CVD) method. In this work, the CNTs@Si is not only introduced as a struc...
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The silicon coated Carbon nanotubes (CNTs) nanocomposite (CNTs@Si) with a shell structure was successfully synthesized by a simple chemical vapor deposition (CVD) method. In this work, the CNTs@Si is not only introduced as a structural material providing oxidation performance, but also as an extremely effective electromagnetic wave (EMW) absorption nanocomposite. Dielectric characteristics EMW absorption properties within the frequency range of 2-18 GHz of CNTs@Si were studied, and the oxidation resistance of CNTs@Si was characterized. Due to the dense space conductive network formed by CNTs, the EMW absorbing properties of CNTs@Si nanocomposite features excellent electromagnetic wave absorption capacity at a filling amount of 1%. The maximum reflection loss (RL) reaches-61.57 dB at the thickness of 1.8 mm, and a wide effective absorption bandwidth (EAB, RL <-10 dB) of 2.88 GHz is achieved. The obtained CNTs@Si core-shell nanocomposites exhibit excellent antioxidant performance and absorbing performance due to silicon bridging. Efficient electromagnetic wave absorption and excellent oxidation resistance of CNTs@Si can be regarded as a brand-new competitive candidate for EMW absorption materials in harsh environment. (c) 2021 Elsevier Inc. All rights reserved.
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Interface optimization has been widely used to improve the optoelectronic properties of nanocomposites, but the theoretical estimation of their effect on the interfacial carrier transfer dynamics is insufficient. Therefore, it is ...
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Interface optimization has been widely used to improve the optoelectronic properties of nanocomposites, but the theoretical estimation of their effect on the interfacial carrier transfer dynamics is insufficient. Therefore, it is very significant to explore the introduced interface electronic structural state and corresponding interfacial electron transfer behavior. In this paper, the possible electron transition path in l-cysteine (l-Cys) sensitized C3N4/CoP (R-C3N4/CoP) and contrast C3N4/CoP is explored, and the corresponding electron transition probability of these paths is calculated by the transition dipole moment. As a result, due to the introduction of l-Cys, the electron transition probability of R-C3N4/CoP is one order of magnitude higher than that of other path without l-Cys. Moreover, these theoretical calculation results are in good agreement with our experimental results.
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Heavy metal pollution in Antarctica has far exceeded expectations. Antarctic yeast is widely present in polar marine environment. The mechanisms of metabolomics effect of heavy metal on polar yeast have not been reported previousl...
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Heavy metal pollution in Antarctica has far exceeded expectations. Antarctic yeast is widely present in polar marine environment. The mechanisms of metabolomics effect of heavy metal on polar yeast have not been reported previously. In this study, gas chromatography-mass spectrometry (GC-MS) wascarried out to performed the metabolite profiling analysis of Antarctic sea-ice yeast Rhodotorula mucilaginosa AN5 exposed to different cadmium (Cd) stresses of 5 mM (HM5), 10 mM (HM10) and 20 mM (HM20), respectively. Metabolic profile analysis showed that the composition and contents of cellular metabolites have been altered by cadmium. 93 different metabolites were identified altogether, among which 23, 58 and 81 different metabolites were found in HM5, HM10 and HM20 group respectively. MetaboAnalyst analysis showed that in HM5, HM10 and HM20 groups, 12, 24 and 31 metabolic pathways were involved in the stress of cadmium to R. mucilaginosa, respectively. By contrasting with Kyoto Encyclopedia of Genes and Genomes database, we discovered that exposure of yeast AN5 to Cd stress resulted in profound biochemical changes including amino acids, organic acids and saccharides. These results will supply a nonnegligible basis of studying the adaptive resistance mechanism of Antarctic yeast Rhodotorula mucilaginosa to heavy metal. [GRAPHICS] .
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Criegee intermediates (CIs) play a significant role in cell membrane peroxidation, but their identification remains elusive at the molecular level. Herein, we combined interfacial extraction and sonic spray ionization mass spectro...
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Criegee intermediates (CIs) play a significant role in cell membrane peroxidation, but their identification remains elusive at the molecular level. Herein, we combined interfacial extraction and sonic spray ionization mass spectrometry to study the oxidation reaction of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1 & PRIME;-rac-glycerol) (POPG) mediated by ozone (O3) at/near the surface of a hung water droplet. On-line interfacial extraction and ionization provided a snapshot of the short-lived CIs. Experiments in which the content of water was varied provided evidence for the formation of CIs, which has not been previously observed. Capture experiments using 5,5-dimethyl-pyrroline N-oxide (DMPO) indicated that CIs could be selectively characterized, and the extracted ion current (EICs) of CIs vs DMPO-CI adducts further confirmed the successful observation of CIs. Theoretical calculation suggested that surface ozonolysis of POPG was mainly mediated by anti-CI. These results open a new route for aqueous surface reactive species identification, and benefit toward the understanding of disease development associated with cell oxidative stress mediated by CIs.
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High efficiency and broad bandwidth wave absorption materials are urgent need in daily life for human health. Carbon material (graphene, etc.) is widely used in electromagnetic wave (EMW) absorption field for light weight, high su...
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High efficiency and broad bandwidth wave absorption materials are urgent need in daily life for human health. Carbon material (graphene, etc.) is widely used in electromagnetic wave (EMW) absorption field for light weight, high surface area, and excellent electrical conductivity. However, the immoderate conductivity of the carbon will also cause the impedance mismatch and need more consideration. We have synthesized sucrose-derived carbon-based hybrid absorbers, and a series of Ni-based alloys (Ni, Fe-Ni, Co-Ni) are decorated on the surface of the carbon. Consequently, the Ni/C composite shows a maximum attenuation constant, and an ultra-broad wide effective bandwidth of 6.24 GHz with an optimal reflection loss (RL) value of -20.5 dB located at thickness of only 1.7 mm. The Co-Ni/C composite has an improved impedance matching level, and shows the optimal RL of -34.3 dB located at a thickness of 3.3 mm with an effective bandwidth of 4.24 GHz. The Fe-Ni/C composite shows an optimal RL among all the samples of -42.3 dB located at a thickness of 5.7 mm with the effective bandwidth of 2.8 GHz. The Ni-based alloys decorated sucrose-derived carbon hybrid can be a proper candidate for microwave absorption as its light-weight outstanding EMW absorption property.
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In this study, the effect of repair welding on the fatigue behavior of AA6082-T6 welded T-joints in marine structures was investigated based on experiments and the fitness-for-service (FFS) assessment in BS7910. Repair welding led...
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In this study, the effect of repair welding on the fatigue behavior of AA6082-T6 welded T-joints in marine structures was investigated based on experiments and the fitness-for-service (FFS) assessment in BS7910. Repair welding led to an increase in residual stress and a decline in fatigue life according to fatigue tests and FEA. Meanwhile, repair welding changed the crack initiation site (CIS) and crack shape factor (CSF, the ratio of crack depth a to length 2c; i.e., a/2c), as indicated by fatigue fractography. In addition, when FFS assessment was performed, two methods for characterizing the CSF under different repair welding lengths during fatigue crack growth were presented: fixed and non-fixed a/2c. The results showed that repair welding led to a transition from ductile fracture to brittle fracture. For a fixed CSF, the critical crack depth and crack opening area of T-joints with repair welding lengths of 30 mm were greatly reduced by 63-66% and 86-89%, respectively, compared to T -joints without repair welding. However, the corresponding reductions for the non-fixed a/2c method were approximately 40% and 90%. The comparison indicated the results obtained with a non-fixed CSF were more consistent with the experiments, with a deviation below 15%.
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Joining ceramics and metals is important to expand their application scope in the nuclear industry. The brazing of SiC and Mo was conducted using a Nb0.74CoCrFeNi2 eutectic high-entropy alloy filler. The microstructure and mechani...
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Joining ceramics and metals is important to expand their application scope in the nuclear industry. The brazing of SiC and Mo was conducted using a Nb0.74CoCrFeNi2 eutectic high-entropy alloy filler. The microstructure and mechanical properties of the joints were examined at different brazing temperatures. As the temperature increased, the eutectic structure gradually disappeared, and a layered structure was formed at the brazed joint. An increase in the MoNi phase content can improve joint strength owing to differences in the thermal expansion coefficient and lattice mismatch between phases. The joints exhibited a maximum shear strength of 62 MPa at 1300 degrees C. Finite element analysis results demonstrated that the presence of a Cr0.46Mo0.4Si0.14 phase causes the concentration of residual stress. Brittle fracture occurred mainly in the Cr0.46Mo0.4Si0.14 phase, causing the rupture of the joint. This study provides valuable insights into the use of eutectic high-entropy alloys as fillers to establish a strong and reliable connection between ceramics and metals.
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