Liu Feng

Silicon monoxide (SiO) has emerged as a promising silicon-based anode material owing to its high theoretical specific capacity and extended cycle life. Nevertheless, its practical application is hindered by significant volume expansion and insufficient cycling stability. In this study, a composite material of SiO coated with zinc sulfide and nitrogen-doped carbon (ZnS&NC/SiO) was successfully prepared via a developed method of in situ conversing MOFs into nitrogen-doped carbon and ZnS. As an anode of lithium-ion batteries, the ZnS&NC/SiO composite exhibited superior reversible capacity (748 mAh·g^-1 after 1000 cycles at 1.0 A·g^-1) and ultralower electrochemical impedance spectra (Rct = 62 Ω). The performance is much superior to that of the reported SiO-based anode materials, which is attributed to the special coating structure that relieves volume expansion and improves the inherently low electrical conductivity, the doped N atoms that provide more active sites, and the SiO and ZnS enables one of them to serve as a buffer medium for more stable structure due to the different lithium intercalation potential. The designed structure could provide a promising strategy for other electrode materials.

Using silicon/reduced graphene oxide (Si/rGO) composites as lithium-ion battery (LIB) anodes can effectively buffer the volumetric expansion and shrinkage of Si. Herein, we designed and prepared Si/rGO-b with a sandwiched structure, formed by a duple combination of ammonia-modified silicon (m-Si) nanoparticles (NP) with graphene oxide (GO). In the first composite process of m-Si and GO, a core–shell structure of primal Si/rGO-b (p-Si/rGO-b) was formed. The amino groups on the m-Si surface can not only hybridize with the GO surface to fix the Si particles, but also form covalent chemical bonds with the remaining carboxyl groups of rGO to enhance the stability of the composite. During the electrochemical reaction, the oxygen on the m-Si surface reacts with lithium ions (Li⁺) to form Li₂O, which is a component of the solid–electrolyte interphase (SEI) and is beneficial to buffering the volume expansion of Si. Then, the p-Si/rGO-b recombines with GO again to finally form a sandwiched structure of Si/rGO-b. Covalent chemical bonds are formed between the rGO layers to tightly fix the p-Si/rGO-b, and the conductive network formed by the reintroduced rGO improves the conductivity of the Si/rGO-b composite. When used as an electrode, the Si/rGO-b composite exhibits excellent cycling performance (operated stably for more than 800 cycles at a high-capacity retention rate of 82.4%) and a superior rate capability (300 mA h/g at 5 A/g). After cycling, tiny cracks formed in some areas of the electrode surface, with an expansion rate of only 27.4%. The duple combination of rGO and the unique sandwiched structure presented here demonstrate great effectiveness in improving the electrochemical performance of alloy-type anodes.

We have developed a convenient and environmentally benign method for the fabrication of sub‐micron‐sized TiO₂ spheres through direct hydrolysis, with the assistance of hollow detergent bubbles as template. The samples obtained at elevated temperatures are firstly characterized by X‐ray diffraction (XRD) and the corresponding photocatalytic activities are evaluated by measuring the photocatalytic oxidation of methyl orange (MO). The results reveal that relative crystallinity and crystallite size have mutual influence on photocatalytic property. Then scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are carried out to investigate the morphology. It can be concluded that hollow templates transform into solid TiO₂ products without auxiliary additives. This strategy is quite promising for the low cost, no waste effluent and high productivity, providing a wide range of applications in photocatalysis, catalysis, solar‐cell, separation, and purification processes.

Cu-rich precipitates are the important influence factors for the irradiation embrittlement of the reactor pressure vessel model steels. The microstructure of the Cu-rich precipitates could be revealed by mechanical and magnetic properties. In this article, the effect of the Cu-rich precipitates on thermal conductivity was studied. The reactor pressure vessel (RPV) model steels were aged for different time at 500°C. The results show that the thermal conductivity of RPV model steel is first decreased and then increased during the experiment, with a minimum value at 48.33 ± 0.21 W·m⁻¹·K⁻¹ after being aged for 200 h. The changing thermal conductivity is decided by the synergistic effect of the following three factors: (1) the crystal structure transformation of Cu-rich precipitates, (2) the orientation relationship between the matrix and Cu-rich precipitates, (3) the content of Cu atoms in the matrix.

In this paper, a bulk V-containing cobalt-based alloy with high chromium and tungsten contents was prepared by mechanical alloying and hot pressed sintering using Co, Cr, W, Ni, V and C pure element powders. XRD, SEM, TEM and Vickers hardness tests were employed to characterize the microstructure and mechanical properties of the mechanical alloyed powders and hot pressed bulk cobalt-based alloy. The results show that all elements can be mixed uniformly and that the Co, Cr, and Ni elements were made into an amorphous state after 10 h ball milling in a high energy ball miller. The microstructure of the prepared bulk alloy was composed of a γ-Co matrix with a large number of nano-twins and fine M₂₃C₆ and M₁₂C carbide particles well-distributed in the alloy. The V element was mainly distributed in M₂₃C₆-type carbide and no V-rich MC-type carbide was found in the microstructure. The prepared alloy had a high hardness of 960 ± 9.2 HV and good a fracture toughness K_Ic of about 10.5 ± 0.46 MPa·m^1/2. The microstructure formation and strengthening mechanisms of the prepared cobalt-based alloy are discussed.