查看更多>>摘要：Low initial coulombic efciency (ICE) and poor long-term cycling performance are key issues of silicon (Si) anode for lithium-ion batteries (LIBs), due to the irreversible consumption of Li ion. Herein, Si with corn-like structure is synthesized by a simple and low cost magnesiothermic reduction method from pre-treated sepiolite ore. The ICE of corn-like Si reaches 75.1 % and can be increased to almost 100 % by a simple surface prelithiated engineering, meanwhile the charge capacity remains 788 mA h·g-1 (0.56 mAh·cm-2) after 500 cycles at 1 A·g-1(0.71 mA·cm-2). Further SEM observation reveals that the prelithiated Si electrode keeps the original corn-like structure during cycling, confrming that available-Si from natural clay is applicable for the production of LIBs.
查看更多>>摘要：? 2022We report magnetic and thermal properties of Cu substituted Ni92?xCuxCr8 polycrystalline alloys close to their critical concentration (xc ~18%), where ferromagnetic order disappears. From the detailed analysis of field and temperature dependent magnetization data weak itinerant ferromagnetic character has been identified for the compositions below xc. Spin-fluctuations theory using the Ginzburg–Landau formalism further revealed the contributions of spin fluctuations, which increase near xc. Specific heat data shows unusual low-temperature variation with an enhanced Sommerfeld coefficient and non Fermi-liquid behavior due to strong magnetic fluctuations near xc. The magnetization data and the linear term of the specific heat follow the theoretical predictions of a ferromagnetic quantum critical point within the experimental uncertainties. The exponent of the power-law M(H) ∝Hλ fits to low-temperature magnetic isotherms and its variation with composition indeed suggests a possibility of quantum Griffiths phase in these alloy compositions. Finally, this study shows that the Cu substituted Ni-Cr system shows Griffiths phase at critical point even after the reduction of disorder.
查看更多>>摘要：? 2022 Elsevier B.V.For the development of discontinuously reinforced titanium matrix composites (DRTMCs), tailoring the reinforcement network distribution has demonstrated significant advantages in alleviating the conflict between strength and ductility. In the present work, network structured titanium matrix composites reinforced with feathery NiTi2 and TiC nanoparticles were successfully prepared via an in-situ processing strategy. The introduction of C and Ni into the Ti matrix was achieved by electroless nickel plating of graphene nanosheets (GNFs) and a short-time ball milling process. The investigations of microstructure revealed that the 3D network architecture gradually formed with the increase of the reinforcement content, and the in-situ generated feathery NiTi2 was tightly connected to the TiC nanoparticles and grown into the Ti matrix. However, when the nickel content is too high, the 3D network architecture was replaced by a large number of amorphous areas, thereby deteriorating the performance of the composites. The tensile tests showed that the as-rolled composites can reach a tensile strength of 994 MPa while maintaining an acceptable ductility (~10.5%). The findings highlight the importance of interfacial microstructure design, which is helpful for the development of high-performance titanium matrix composites.
查看更多>>摘要：? 2022Nanoscale [(Ba0.85Ca0.15)0.995Nd0.005](Ti0.9Hf0.1)O3 (Nd-BCTH) ceramics were prepared via the hydrothermal method, and the effects of sintering temperature and holding time on the phase structure, micromorphology, electrical and optical properties of the Nd-BCTH ceramics were explored. All the Nd-BCTH ceramics present rather pure perovskite structure with composition approaching rhombohedral phase around the morphotropic phase boundary (MPB) region. The highest relative density is obtained for the sample sintered at 1220 °C for 10 h. The existence of Ba2+, Ca2+, Ti4+, Hf4+ and Nd3+ is confirmed and the elements distribute rather uniformly detected by X-ray photoelectron spectrometer (XPS) and energy dispersive X-ray (EDX) analysis. The ceramics present nanoscale grain size, which tends to increase with the increase of sintering temperature and holding time, and significantly affects dielectric constant and Curie temperature. Very thin and narrow ferroelectric hysteresis loops are observed, where a considerable energy storage density (173.88 mJ/cm3) and high energy storage efficiency (80.68%) are obtained at low electric field. The increase of sintering temperature and holding time induces a red shift at 400 nm absorption edge and a blue shift at 300 nm absorption edge in the Nd-BCTH ceramics, and all ceramics have a maximum absorption value at around 260 nm. Under the excitation of 269 nm light, the Nd-BCTH ceramics show the strongest fluorescence peak at 473 nm, corresponding to the 4G3/2→4I9/2 transition, emitting indigo blue fluorescence. When the ambient temperature is above 400 °C, grains conduction dominates the conductive mechanism in the nano-sized Nd-BCTH ceramics. Such conduction can be attributed to oxygen vacancies caused due to the evaporation of alkaline-earth metals during high temperature sintering, and show typically thermally excited relaxation process.
查看更多>>摘要：? 2022The low utilization rate of photo-generated carriers in graphite-phase carbon nitride (g-C3N4) is the main factor limiting its photocatalytic performance. In this work, to begin with single-atom Co was inserted into the structure of g-C3N4, then it was vulcanized to prepare composite Co-S single-site in g-C3N4. The results show that the Co-S single-site cocatalyst was successfully synthesized and was stably anchored in the structure of g-C3N4. As an active site, it can not only enhance the reaction activity, but also capture electrons to provide transfer channels for the photo-generated carrier, thereby enhancing the photocatalytic hydrogen evolution performance of g-C3N4. The hydrogen production of Co-S single-site modified g-C3N4 reaches 72.85 μmol (per 0.02 g photocatalyst) under visible light, which is 9 times higher than that of pure g-C3N4. This work provides a reasonable method for the preparation of composite single-site cocatalyst.
查看更多>>摘要：? 2022The development of efficient non-noble-metal based catalysts for oxygen evolution reaction is the crucial issue to promote electrolytic water technology. Herein, an effective phosphorus-modified hollow porous Nickel-Cobalt oxides nanocube was prepared by thermal oxidation and partial phosphorization processes. The optimal P-NiO/NiCo2O4 nanocube disclosed remarkable electrochemical activity for OER in 1.0 M KOH with a low overpotential of 290 mV at 10 mA cm?2, a low Tafel slope of 49.6 mV dec?1, and good long-life stability for 20 h. Based on the experimental and theoretical calculation results, the introduction of P was proved to be the key to the excellent electrochemical activity for OER. P doping could optimize the adsorption of the intermediates, decrease the energy barrier and change the rate-determining step. Meanwhile, the P-dopant could modulate the electronic structure and enhance the conductivity of NiO/NiCo2O4. In addition, hollow, porous hybrid structure and oxygen vacancies could increase the number of active sites exposed, and facilitate the ion transport. The present work provides a valuable strategy to design transition-metal oxide based electrocatalysts with enhanced electrocatalytic performances by controlling partial P doping.
查看更多>>摘要：? 2022Novel refractory carbide reinforced tungsten matrix (W-MeC) composites have high microstructural stability and attractive high-temperature mechanical, thermo-physical and chemical properties, and they are promising candidates for a very wide range of applications across the aerospace, military, advanced machining and energy industries. In this review, material design, fabrication methods and microstructural features of W-MeC composites are presented. The mechanical and thermo-physical properties, resistance to oxidation, thermal shock and ablation, and the mechanisms of high-temperature strengthening of W-MeC composites are covered. In addition, the applications of W-ZrC composites as well as major challenges and future trends are outlined as well. This review provides a good understanding of the state-of-the-art research in W-MeC composites and inspires researchers to explore and develop W-MeC composites with improved properties fabricated in smart and cost-effective manners.
查看更多>>摘要：? 2022 Elsevier B.V.Spark plasma sintering (SPS) has some advantages for preparing multifunctional materials, such as fast heating rate, short sintering time, and high compactness of products. In this work, we reported the effect of sintering time on the structural and magnetocaloric properties of Mn1.15Fe0.85P0.65Si0.13Ge0.2B0.02 prepared by SPS. The crystalline structure, microstructure and composition were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). The results indicated that all the alloys crystallized in the hexagonal structure with a space group of P6 ? 2m. A secondary phase of (Mn,Fe)3(Si,Ge) was not found in SEM but in TEM measurement. Transition temperature and isothermal entropy change were determined from thermal magnetization data measured in different constant magnetic fields. The results showed that the alloys undergo first-order phase transitions at transition temperatures between 248.8 K and 281.9 K. The maximum isothermal entropy change was found in the alloy sintered for 15 min, being 15.6 J ? kg?1 ? K?1 for a magnetic field change of 3 T. It indicated that no less than 15 min sintering time was required to prepare the alloy with good homogeneousness and large magnetocaloric effect. Consequently, SPS is an effective method for synthesizing the Fe2P-type alloys and the resultant alloys are promising magnetocaloric materials for magnetic refrigeration near room temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Single-atom based photocatalysts have been widely used in the degradation of organic pollutants due to their excellent activity, nearly 100 % atomic utilization efficiency and well-defined active centers. Here, we propose a single Co atom cocatalyst coordinated by nitrogen-doped graphene (Co-NG) to enhance the photocatalytic activity of perylene diimide (PDI) toward bisphenol A (BPA) degradation. Firstly, the self-assembled PDI on the surface of Co-NG exhibits a uniform dispersion state, which facilitates electron transport across the interface. Secondly, Nitrogen-doped graphene can act as a charge transfer bridge to facilitate charge migration from PDI to single Co atom catalytic center. Therefore, in the photocatalytic degradation of BPA, the Co-NG/PDI composite photocatalyst showed a significant increase in activity. 7 % Co-NG/PDI composite possesses the best photocatalytic performance, and the apparent rate is 6.64 times and 7.6 times higher than those of self-assembled PDI and Co-NG. The excellent activity is due to its high photogenerated carrier migration and transfer efficiency. Furthermore, the results of free radical capture experiment and ESR test confirm that singlet oxygen, superoxide radical, hydroxyl radical and hole are the main active species in the degradation process of BPA. We detected the intermediate products and proposed the degradation by LC-MS analysis. This study may provide a promising sunlight-driven photocatalyst for the treatment of the BPA in wastewater.
Mohammad Moradi S.Zangeneh S.Vardak S.Bahrami R....
15页
查看更多>>摘要：? 2022 Elsevier B.V.In this research, a novel antibacterial alloy was fabricated through the addition of Cu and Nb to the conventional Co-Cr-Mo (CCM) alloy. Tungsten inert gas (TIG) welding was utilized to add Cu and Nb to the CCM alloy by surface re-melting. The microstructural investigations revealed that the addition of Cu and Nb to the CCM alloy resulted in significant changes. It was also concluded that the addition of Nb up to the optimum value of 0.2 wt%Nb increased the wear resistance, however, no significant effect was observed on corrosion resistance. Moreover, it has been found that the optimum alloy showed higher charge transfer resistance (Rct) in SBF solution and also better protein adsorption. In addition, it was concluded that the modification of the CCM alloy with 4.5%wt Cu and 0.2 wt%Nb led to a decrease in the Co concentration released in SBF solution, and boosted the antibacterial property of the CCM alloy.
NSTL
Elsevier