查看更多>>摘要:? 2022 Elsevier B.V.The atomically interfacial engineering combined with the rational architecture design is of significant important for developing promising oxygen electrocatalysts towards efficient energy-related applications, but still remains a grand challenge. Herein, we report numerous CoFe alloy nanoparticles, with tunable compositions, anchored firmly over the well-designed oxygen-dopants-rich carbon nanoboxes (CoFe@C NBs) as an active electrocatalyst for electrochemical oxygen reduction reaction (ORR), which is fabricated via a facile cation exchange and pyrolysis strategy. Thanks to the robust interfacial electronic coupling and the highly-exposed synergetic bimetallic centers, this optimized CoFe-27 @C NBs with the Co: Fe atomic ratio of 5.4: 1 could exhibit superior activity, excellent long-term stability and high methanol tolerance during a long-term ORR operation, with an excellent half-wave potential of 0.90 V and decent limiting current density of 5.4 mA cm?2, comparable with the commercial Pt/C catalysts and being one of the most active transition-metal ORR electrocatalysts developed. By the atomic-level synchrotron radiation characterizations and the detailed electrochemical measurements, it can be found that the strong electronic coupling at the metal-support interface could effectively promote the charge transfer and catalytic reaction kinetics, contributing to efficient 4e- ORR for CoFe-27 @C NBs.
查看更多>>摘要:? 2022 Elsevier B.V.The microstructure stability, evolution law and identification of carbide and harmful phase TCP of nickel-base powder superalloy aged at 800 ℃ for 100 h —10000 h were studied by means of field emission scanning electron microscope, atomic force microscope and electron backscatter diffraction. The results show that with the increase of aging time, the grain size changed little, the grain boundary coarsened and the twin boundary Σ3 increased first and then decreased. γ' phase coarsened obviously from 500 h aging, and the coarsening rate increased first and then decreased The coarsening mechanism is mainly the combination of adjacent γ' phase by AFM analysis. Lath-like σ phase CrCo precipitated at the grain boundary first after aging for 1000 h. When the aging time was up to 2000 h, the needle-like μ phase Co7(W, Mo)6 was observed in the crystal. With the further increase of aging time, the total content of TCP phase at grain boundary and in crystal increased obviously. However, at 10000 h, the TCP phase in the crystal and at the grain boundary almost disappeared, mainly because the atoms in the TCP phase diffused into the γ' phase to form a new solid solution and deposited on the grain boundary, which further coarsened the grain boundary.
查看更多>>摘要:? 2022 Elsevier B.V.The effects of Pt/Ta seed layer on the thermal stability of perpendicular magnetic anisotropy (PMA) compared to a single Ta seed layer was investigated in detail. The results showed that the PMA property is still stable in Pt/Ta/CoFeB/MgO sample above 300 °C annealing temperature. However, it deteriorates in Ta single seed layer when the annealing temperature increase up to 270 °C. Through microstructure analysis, the reason was attributed to the different elements diffusion tendency in the whole structure. It was found that the crystallization of seed layer Pt supplies an efficient diffusion paths for Ta. It decreases the ratio of Ta (about 15%) at CoFeB/MgO interface, and ensure more Fe-O bonding to improve PMA and its temperature stability. However, the Ta single seed layer is amorphous. It may diffuse to the CoFeB easily and decrease the hybridization between Fe/Co 3d and O 2p orbits. These observations confirm that the Pt/Ta seed layer provides a promising avenue to enhance the thermal stability of PMA effect, and meets the requirement of field-free spin-orbit torque (SOT) switching based on their opposite spin Hall angels.
查看更多>>摘要:? 2022 Elsevier B.V.Based on the fact that the mean free path of phonon is larger than that of the electron, the improvement of ZT could be obtained by adjusting the size of grain boundary. Pushing the size of grain boundary down to the length ranges stated by the electron MFP, both electron transport and phonon transport are affected strongly, but the reduced scale of phonon transport is larger than that of electron transport, leading to the enhancement of ZT. By combining all electron and phonon transport property from full electron-phonon interactions, the room-temperature thermoelectric property of n-type SnSe under different electron/phonon transport mechanism is evaluated. The h-LO dominates the scattering process of electron transport, while the optic branch controls the scattering process of phonon transport. Compared to the bulk ZT (0.26), the room temperature ZT of 0.62 with the size of 7 nm is obtained, which is nearly three times higher than that of bulk value. Our work not only reveals the enhancement of ZT by the electron filtering effect, but also exhibits the computational framework for accurately calculating the thermoelectric performance under different electron/phonon transport mechanisms.
查看更多>>摘要:? 2022 Elsevier B.V.In the present study, the reduced graphene oxide (RGO) decorated by monodispersed superparamagnetic Fe3O4 (RGO-IO) nanocomposite was prepared and confirmed with various spectroscopic and microscopic techniques. The elemental spectral mapping depicts the composition of carbon, oxygen and iron in confirmed the successful formulation and homogenous distribution. The X-ray photoelectron spectroscopy (XPS) analysis of nanocomposite confirms the existence of elements such as C, O and Fe. The Raman spectroscopy analysis showed the characteristic peak for RGO i.e. D-band and G-band and A1 g phonon and Eg phonon peaks for IO is indicating the formation of RGO-IO. Moreover, the HR-TEM microscopic analysis evidently revealed the 2D structured RGO nanosheets are well decorated by a large quantity of IO nanoparticles. The in vitro cytotoxic activity of nanocomposite showed less toxicity and increased the cellular growth of mouse C2C12 and 3T3-L1 cells at higher concentration. The treatment of nanocomposite increases the ROS generation due to the excellent electrochemical performance and induces the formation of myotubes and mature adipocytes. The nanocomposite upregulates the expression of molecular marker proteins responsible for the myogenesis and adipogenesis was confirmed. Together, the synthesized RGO-IO nanocomposites provide surplus support for the use of nanomaterials in tissue engineering and regenerative medicine.
查看更多>>摘要:? 2022 Elsevier B.V.In this paper, the carbon coated iron nickel nanoparticles were obtained by calcining PVP crosslinked iron nickel oxalate. The morphology, structural composition and microwave-absorbing (MA) properties of the composites were analyzed by various characterization methods. The results show that FeNi/C composites have excellent impedance matching characteristics and MA performance in multiple frequency by virtue of their microscopic network structure. At the same time, through the analysis of loss mechanism, we found that the material has high dielectric loss and magnetic loss characteristics. Under the joint action of various loss mechanisms such as interface polarization and eddy current loss, the material has a high reflection loss (RL) value at different frequency. At a thickness of 3 mm, the sample FNC12 has a minimum RL of ? 52.99 dB at 3.6 GHz. The effective absorption bandwidth (EAB) (RL ≤ ?10 dB) is 1.81 GHz.
查看更多>>摘要:? 2022 Elsevier B.V.2D MXenes have attracted extensive attention for energy storage applications owing to their high electronic conductivity, excellent redox activity, and remarkable mechanical property. Nevertheless, they still suffer from sluggish ion kinetics caused by layer restacking. Herein, flexible V2CTx/Ti3C2Tx composite films have been successfully assembled. The delaminated Ti3C2Tx matrix guarantees the predominant electronic conductivity and mechanical stability of the flexible electrode. Meanwhile, V2CTx spacers embedded in Ti3C2Tx layers efficiently restrain their self-restacking and consequently result in enriched ion channels for electrolyte ion accessibility. Benefiting from this elaborately designed vertical-liked pillar structure, the V2CTx/Ti3C2Tx electrode exhibits a maximum gravimetric capacitance of 365 F g?1 at 1 A g?1, and outstanding cycling stability without capacitance loss after 10,000 cycles. Moreover, the assembled symmetric supercapacitor shows a high energy density of 5.4 mWh g?1 at a power density of 357.8 mW g?1. This work may demonstrate an efficient approach for combining the respective advantages of binary or ternary MXenes with different metal elements and morphologies for efficient energy storage.
查看更多>>摘要:? 2022 Elsevier B.V.High-entropy metallic glass nanoparticles (HEMG-NPs) have shown great potential in the development of sustainable energy. Discovering new nanomaterials for electrocatalysis and maintaining their long-term stability is an effective way. The presence of nanoparticles in an independent transparent substrate material provides a unique way for its stability and maximum performance. This special composite structure is very beneficial to the study of the fine structure of a single specific particle. Here, we propose a general synthesis strategy, in which alloy targets are implanted into the substrate by ion implantation and annealed to grow into NPs. The disordered arrangement of ions into the substrate and the subsequent slow dynamics, disordered microscopic microstructure. Calculating the similarity of the depth range of simulated metal ion implantation provides a theoretical basis for the successful formation of HEMG-NPs. Electrocatalytic water splitting shows that CuCoNiFeZn HEMG-NPs is a non-precious single nano-microcatalyst suitable for multifunctional (HER and OER) electrocatalysis, highlighting its application in sustainable energy conversion. The use of ion implantation aims to synthesize HEMG-NPs with long-term stable storage and minimized denaturation. In further research, the formation of fine structure corresponds to the law of electrocatalytic activity. Develop high-efficiency electrocatalytic HEMG-NPs materials based on the original microstructure.
查看更多>>摘要:? 2022 Elsevier B.V.This study developed a novel series of AlCrCuFeNi2Vx (x = 0, 0.3 and 0.6) high-entropy alloys (HEAs), and systemically assessed the relationship between composition, processing, microstructure and mechanical properties. The alloys were produced by arc melting and studied in as-solidified and homogenized (annealing at 650 ℃ for 4 h) conditions. In the base alloy of AlCrCuFeNi2, the microstructure consists of disordered bcc and fcc phases, ordered B2 and L12 phases, and the B2 phase and bcc phase are coherent. With the increase of V content, the volume fraction of bcc/B2 phases increase, accompanied with a peculiar phenomenon that the shape of B2 phase has transferred from irregular matrix to spherical precipitates, which caused by the increase of lattice misfit after V addition. Moreover, a large number of Cu particles are randomly distributed in the NiAl (B2) phase, and the crystal structure of Cu particles has changed from 9 R structure to fcc structure after annealing treatment. Mechanical tests of these alloys reveal that the 0.6 at% V addition has doubled the yield strength (V0, 780 MPa; V0.6, 1673 MPa) for the increase in volume fraction of bcc/B2 phase and the solid solution strengthening produces by V addition. The yield strength is increased by 124 MPa after annealing treatment in V0.6 alloy without sacrificing the ductility due to the promotion of L12 phase after annealing treatment.
查看更多>>摘要:? 2022NiCoxP @ NiCo-LDH catalysts are prepared by phosphating NiCo nanosheets on NiCo-layered double hydroxide (LDH) with multi-layer heterostructure. The NiCoxP @ NiCo-LDH could undergo electrocatalytic hydrogen evolution from the methanol/water mixture and value-added formate co-production. During the electrocatalytic reactions, the phosphating NiCoxP nanosheets could greatly improve the electron transfer efficiency, and it has a synergistic effect with heterostructures to enhance the electrocatalytic performance. During the hydrogen evolution and methanol oxidation reactions, the potential is only 0.132 and 1.23 V when the current density reaches 10 mA cm?2. Meanwhile, the NiCoxP @ NiCo-LDH symmetric two-electrode electrolyzer has a lower potential of only 1.43 V at a current density of 10 mA cm?2 and the Faraday efficiency of the production of formate and H2 is nearly 100%. The electrocatalysts also display excellent stability during the water/methanol co-electrolysis.