查看更多>>摘要：? 2022 Elsevier B.V.Ion-irradiation of titanium oxide (TiO2) nanoparticles is shown to result in the merging of the nanoparticles to form continuous chains of different shapes and dimensions, including one-dimensional nanostructures. Changes in the structure, morphology and surface chemistry of the nanoparticles were studied following irradiations with different ion-species and energies, and using scanning and transmission electron microscopies, X-ray diffraction, as well as various spectroscopic methods. High-resolution electron microscopic images confirm the merging of near-neighbor nanoparticles after irradiation, while X-ray diffraction reveals the formation of a new phase of titanium oxide resulting from ion-induced recrystallization. Analysis with X-ray photoelectron spectroscopy, Raman scattering, optical absorption, and infrared spectroscopy confirms the presence of oxygen vacancies and the formation of surface defects in the nanostructures. The resulting changes in surface chemistry and morphology are shown to affect the wettability and electrical conductivity of the material. The creation of defects and the evolution of the nanostructure, including the merging of nanoparticles and the formation of particle chain, are shown to be consistent with the predictions of Monte Carlo-based 3D TRI3DYN simulations, while the alteration of the wettability and electrical conductivity are explained using first principles-based calculations.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, Fe2O3 with oxygen vacancies (OVs) introduced by Ti doping is partially wrapped by reduced graphene oxide (rGO), and then grown directly on carbon cloth (CC) to obtain a self-supported electrode with hierarchical structures (Ti-Fe2O3@rGO/CC). Compared with Fe2O3 nanosheets, Ti-doped Fe2O3 nanosheets show better lithium storage performance because the existence of OVs can not only promote faster charge transfer kinetics but also help to maintain the integrity of electrode structure and improve the electrochemical activity. Especially, the rGO sheets are partially wrapped on Ti-Fe2O3, inhibiting the agglomeration of components and shortening the diffusion distance of Li+, to obtain better cycle stability. Moreover, it can also provide a buffer to alleviate the volume expansion, avoid the excessive growth of SEI film, and ensure that OVs can maximize their advantages under deep discharge conditions. The Ti-Fe2O3@rGO/CC electrode delivers a high capacity of 1193 mAh g?1 (3.245 mAh cm?2) at 200 mA g?1, showing great potential as an anode material for lithium-ion batteries.
查看更多>>摘要：? 2022 Elsevier B.V.Developing non-precious metal electrocatalysts with stable and high activity toward the oxygen evolution reaction (OER) is of great significance for efficient electrolysis of water for hydrogen production. Herein, we report an electrocatalyst derived from covalent organic frameworks (COFs) anchored by pyrolytically active bimetals (Fe/Co), in which COF-derived carbon is used as the support to anchor active bimetal Fe/Co nanoparticles. The porous and periodically structured COFs have great potential as active center carriers for electrocatalysts. Since Fe/Co ions are immobilized in the pore channels of the triazine-based Schiff base network (SNW-1), the aggregation and migration of Fe/Co ions effectively was prevented during pyrolysis. Importantly, the COF-derived catalyst possesses abundant nitrogen content, high micropore and mesopore volumes and good electrolyte permeability. As a result, the COF-derived catalyst displays excellent OER performance, with low overpotential (η10 = 288 mV) and Tafel slope (40 mV dec?1) in alkaline media, outperforming commercial RuO2 and most oxygen electrocatalysts. Moreover, the catalyst exhibited satisfactory stability. Thus, this work expands new horizons and pathways for the development of OER electrocatalysts based on COFs.
查看更多>>摘要：? 2022 Elsevier B.V.Effect of SiCw volume fraction on thermal shock resistance (TSR) of ZrB2-20 MoSi2 composite has been studied in the present work. Three composites namely ZMSw0 (ZrB2-20 MoSi2-0 SiCw), ZMSw5 (ZrB2-20 MoSi2 - 5SiCw) and ZMSw20 (ZrB2-20 MoSi2-20 SiCw) were prepared by multi-stage spark plasma sintering at 1700 °C. TSR was measured using indentation quench technique. Results indicate that an increase in silicon carbide percentage decrease the crack growth rate and increase the critical temperature differential ΔTc, which in turn continuously raises the TSR of the composites. Development of thermal residual stresses due to thermal shock leads to excellent crack shielding and higher TSR of the ZMSw20 composite. The reduction in hardness and fracture toughness due to thermal shock for the ZMSw20 composite is lesser than that of both the ZMSw0 and ZMSw5 composites.
查看更多>>摘要：? 2022 Elsevier B.V.O3-type NaNi0.5Mn0.3Co0.2O2 based positive electrode materials are very promising for sodium-ion batteries. However, the irreversible phase transition due to structural deformation leads to sluggish kinetics, rapid capacity fade, and low C-rate performance, limiting its wide practical applications. The partial substitution of Co3+ (0.545 ?) by Al3+ (0.535 ?) ions in the transition-metal layer in NaNi0.5Mn0.3Co0.2-xAlxO2 (0.01 ≤ x ≤ 0.02) is an effective strategy to address the issue of structural deformation and thus to improve the electrochemical performance of NaNi0.5Mn0.3Co0.2O2 cathode. Solution combustion synthesis of NaNi0.5Mn0.3Co0.2-xAlxO2 (x = 0.01, 0.02) shows O3-type structure of NaNi0.5Mn0.3Co0.2?xAlxO2 material with the space group of R3ˉm. The composition with an overall x = 0.02 Al doping delivers an initial 120 mAh g?1 capacity at a 0.1 C rate. It retains 90 % capacity even after 200 cycles than the other stoichiometric aluminum substitution, x = 0.01 (77 %). Moreover, the NaNi0.5Mn0.3Co0.18Al0.02O2 shows a good capacity of ~ 83 mAh g?1 even at a high C-rate of 5 C, almost 70 % of the initial capacity at the 0.1 C rate. The Al-substitute NaNi0.5Mn0.3Co0.2?xAlxO2 cathode's electrochemical performance is attributed to the enhancement in the structural stability of the sodium layered transition metal oxide after the partial substitution of Co3+ by Al3+ ion. Finally, the practical sodium-ion full cells are realized using a hard carbon-based anode and NaNi0.5Mn0.3Co0.18Al0.02O2 cathode, showing 91 % capacity retention at the end of 100th cycles with an OCV of 3.5 V.
查看更多>>摘要：? 2022 Elsevier B.V.Vanadium trioxide (V2O3) is a promising anode material for lithium-ion batteries due to its high theoretical capacity. However, it faces severely hindered in practice by its low electrical conductivity and serious volume change. Mixed metal engineering could improve electrochemical reactivity and ion transport by modulating surface interface structure, thus upgrading host material performance. Herein, the metallic Ni nanocrystals are evenly distributed in V2O3 hollow nanoprisms wrapped by nitrogen-doped carbon (Ni-V2O3 @NC) through a facile self-template method. The unique hollow nanoprism structure can effectively mitigate volume expansion, while the metallic Ni nanograins and N-doped carbon layer can enhance the electric conductivity and adjust the surface structures of host material toward better activity. Metallic Ni nanograins also act as catalyst, which may bring additional reversible capacity to composite. Due to the interaction of components, the as-accomplished Ni-V2O3 @NC nanocomposite exhibits excellent specific capacity (927 mAh g?1 at 200 mA g?1), cycling stability and rate performance.
查看更多>>摘要：? 2022The construction of multidimensional composite photocatalysts with substantial photocatalytic performance, fast charge separation, and a wide light absorption range system poses a major challenge to the field of photocatalytic research. Here, ZnO nanorods with assembling ZnIn2S4 nanosheets via a hydrothermal approach to construct a unique Z-scheme 2D/1D ZnIn2S4/ZnO heterojunction photocatalyst. The morphology, composition, microstructure, and properties of the 2D/1D ZnIn2S4/ZnO photocatalyst were thoroughly investigated through a variety of detailed characterizations. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) findings showed that a significant number of ZnIn2S4 nanosheets evenly grew on the surface of ZnO nanorods. Based on the XPS investigation, the close chemical interaction between ZnIn2S4 and ZnO was identified. The visible light absorption range of the as-prepared photocatalysts was expanded, facilitating electron–hole separation upon photoexcitation according to UV–vis DRS and electrochemical tests. Under light radiation, the 2D/1D ZnIn2S4/ZnO photocatalyst can degrade 96.84 % of methyl orange (MO) within 120 min. Furthermore, the photocatalytic hydrogen evolution rate reached 3348.3 μmol/g/h within 6 h. The enhanced photocatalytic performance was substantial because of the Z-scheme system formed between ZnIn2S4 and ZnO and the 2D/1D nanostructures’ nature, which facilitated carrier transfer and increased the number of active sites for photocatalytic reactions. The charge transfer mechanism of ZnIn2S4/ZnO was discussed in detail according to radical trapping experiments. We expect that the fabrication of 2D/1D materials with a Z-scheme system will offer new ideas and record the development of high-efficiency energy conversion photocatalysts.
查看更多>>摘要：? 2022 Elsevier B.V.The metamagnetic transition in cerium-based intermetallics is a very common intriguing phenomenon that has remained the subject of close study for several decades. We report crystal structure, magnetization and resistivity of a new ternary cerium germanide Ce3Pd2Ge7 with an orthorhombic structure of La3Co2Sn7-type (space group Cmmm, cell dimensions a = 4.3257(3), b = 26.339(2), c = 4.3594(3) ?, V = 496.69(2) ?3). Low-temperature magnetic properties are characterized by a two-step metamagnetic transition, which can be associated with two nonequivalent positions of Ce ions in the lattice. The first metamagnetic transition occurs in weak magnetic fields below T1 ≈ 11 K and then moves to higher fields when the temperature goes down (B ～ 1.5 T at T = 2 K). The second transition manifests itself below T2 ≈ 8 K as a rapid increase of magnetization, which starts from zero field and reaches saturation at fields B ≈ 0.1 T. The magnitude of each transition increases with decreasing temperature and the polarized magnetization ΔM reaches 0.13 μB/Ce and 0.08 μB/Ce upon the first and second transitions respectively. The interchange of nonmagnetic Pd and Ge ions (≈ 0.8 %) leads to the appearance of a hysteresis of metamagnetic transitions, as well as to the splitting of the field cooled (FC) and zero field cooled (ZFC) magnetization curves in hysteresis area. The dependence of the polarized magnetization ΔM on temperature which persists up to high fields as well as the continuation of the hysteresis well above the metamagnetic transition (at least up to B ～ 9 T) indicates a new type of spin-glass-like state, which is caused by the suppression of spin fluctuations and the localization of magnetic moments during the metamagnetic transition.
查看更多>>摘要：? 2022 Elsevier B.V.High-efficiency and thermal stability are two important factors of ideal microwave absorption materials (MAMs), which are becoming desired because of the more complex modern service environment. Herein, a novel quaternary magnetic core-shell-shell structure FeCo-Co@Fe3O4 @SiO2 (FCSF) has been fabricated by a facile and generic route. In this structure, the incipient oxidation temperature of magnetic core can be greatly increased from 523 K to 773 K by the Fe3O4/SiO2 double shells, and the multiple magnetic heterointerfaces can generate electron transfer and spin-orbit interaction based on DFT calculations. The minimum reflection loss (RLmin) and efficient absorption band (RL<?10 dB, feff) of FCSF composites can reach up to ?42.8 dB and 7.3 GHz with the thickness of 2 mm, due to the emerged electromagnetic loss mechanisms of interface polarization and exchange resonance. Moreover, owing to the optimized impedance matching and enhanced electromagnetic loss at elevated temperature, the RLmin values of FCSF at 673 K and 773 K increase by 15.4% and 41.2% compared with that at 298 K, respectively. The results demonstrate that the FCSF composite can act as a promising candidate for high-efficiency MAMs in thermal environment, and the synthetic strategy of heterostructures in this work can also be applied to design other MAM systems.
查看更多>>摘要：? 2022 Elsevier B.V.The segregation of Cu is crucial for the magnetic properties of 2:17 type SmCo magnets, which is firstly affected by the ordering process during aging treatment. In this research, the ordering process is successfully regulated by doping nano ZrO2, which achieves a prolonged ordering process and an increased duration of twin boundaries in 2:17 type SmCo magnets. The continuous migration of twin boundaries in a longer period drives extra Cu to converge towards the cell boundary center, resulting in about 10.52 kOe coercivity only by isothermal aging treatment. The precipitation sequence of the lamellar phase and the cell boundary phase is exchanged. A new understanding of Cu segregation contributes to the development of high performance 2:17 type SmCo magnets.
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