Suppressing Sodium Dendrites by Multifunctional Polyvinylidene Fluoride (PVDF) Interlayers with Nonthrough Pores and High Flux/Affinity of Sodium Ions toward Long Cycle Life Sodium Oxygen‐Batteries

Rechargeable sodium–oxygen (Na–O₂) batteries are of interest due to their high specific capacity, high equilibrium potential output, and the abundance of sodium resources; however, their cycle life is still very poor due to instability of electrolytes and especially the uncontrollable growth of Na dendrites. Herein, as a proof‐of‐concept experiment, a facile and low‐cost strategy is first proposed and demonstrated to effectively suppress growth of Na dendrites by using a fibrillar polyvinylidene fluoride film (f‐PVDF) with nonthrough pore as a multifunctional blocking interlayer. Unexpectedly, the f‐PVDF interlayer endows Na–O₂ battery with superior electrochemical performances, including high rate capability and long cycle life (up to 87 cycles), which is superior to those of the compact PVDF (c‐PVDF), PVDF with through pores (p‐PVDF), polyethylene oxide (PEO), and conventional polytetrafluoroethylene (PTFE) counterparts due to the following combined advantages: (1) the stronger C? F polar function groups provide a better affinity to Na ions, thus enabling a more homogeneous Na deposition than that of C? O function groups in PEO interlayer; (2) compared with c‐PVDF and p‐PVDF interlayers, f‐PVDF holds more electrolyte uptake for higher ion conductivity; (3) the good wettability of the f‐PVDF interlayer with electrolyte benefits Na dendrite suppression compared with PTFE interlayer.     

Hexafluoroisopropyl Trifluoromethanesulfonate-Driven Easily Li+ Desolvated Electrolyte to Afford Li||NCM811 Cells with Efficient Anode/Cathode Electrolyte Interphases

Solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) with optimized components and structures are considered to be crucial for lithium-ion batteries. Here, gradient lithium oxysulfide (Li₂SO_x, x = 0, 3, 4)/uniform lithium fluoride (LiF)-type SEI is designed in situ by using hexafluoroisopropyl trifluoromethanesulfonate (HFPTf) as electrolyte additive. HFPTf is more likely to be reduced on the surface of Li anode in electrolytes due to its high reduction potential. Moreover, HFPTf can make Li⁺ desolvated easily, leading to the increase in the flux of Li⁺ on the surface of Li anode to avoid the growth of Li dendrites. Thus, the cycling stability of Li||Li symmetric cells is improved to be 1000 h at 0.5 mA cm⁻². In addition, HFPTf-contained electrolyte could make Li||NCM811 batteries with a capacity retention of 70% after 150 cycles at 100 mA g⁻¹, which is attributed to the formation of uniform and stable CEI on the cathode surface for hindering the dissolvation of metal ions from the cathode. This study provides effective insights on the strong ability of additives to adjust electrolytes in “one phase and two interphases” (electrolyte and SEI/CEI).     

Spontaneously Splitting Copper Nanowires into Quantum Dots on Graphdiyne for Suppressing Lithium Dendrites

As an emerging carbon allotrope, the controllable growth of graphdiyne has been an important means to explore its unique scientific properties and applications. In this work, the effect of the crystal structure of copper (Cu) on the growth of graphdiyne is systematically studied. It is found that the crystal boundaries are the origin of the reaction activity. The polycrystalline Cu nanowire with many crystal boundaries is spontaneously split into Cu quantum dots (about 3 nm) by the grown graphdiyne. These Cu quantum dots are uniformly dispersed on the graphdiyne, and they block the long-range ordered growth of the graphdiyne. These Cu quantum dots in situ supported on graphdiyne demonstrate high efficiency in inhibiting the growth of lithium dendrites in lithium metal batteries. Based on this interesting finding, the Cu quantum dots anchored on the all-carbon graphdiyne can be prepared on a large scale, and unique applications of Cu quantum dots in electrochemical fields can be implemented.     

宝钢电镀锌汽车板生产技术的最新进展

2003年,宝钢在解决厚镀锌层汽车外板生产的关键技术方面获得突破性进展:即提出了控制导电辊粘锌的有效措施;掌握了控制预磷化板磷化膜质量的诀窍;解决了边部枝晶问题,使得宝钢具备了稳定大批量生产O5板的能力以及与国外钢铁列强角逐高档电镀锌O5板市场的实力.     

49MnVS3非调质钢连铸方坯中心裂纹分析

采用金相、扫描电镜及能谱分析了连铸方坯中心位置的宏观和微观特征.发现偏析是导致中心裂纹产生的主要原因,裂纹发生在柱状晶末端和粗大等轴晶区,沿一次枝晶晶界展开;开裂方式为沿晶开裂,开裂时期处于液相.存在两种晶界偏析,一种为析出的MnS夹杂物,另一种为聚集的浓化钢液.中心位置析出物未达到非调质钢质量要求.     

Ti-SiC Composite and TiC Ceramic Layer Formation on Ti6Al4V Surface by Laser Alloying of Pre-Placed SiC Coating

The Ti-6Al-4V alloy pre-placed with SiC coating was laser alloyed using high power CO2 laser. The laser alloyed cross section shows dendrite and Ti-SiC composite layer microstructure and the respective hardness was 650–800 HV and 1500–2000 HV. The observed hardness was 2 to 7 times greater than that measured on the bulk Ti-6Al-4V substrate. The laser alloyed surface produced high temperature ceramic phases such as TiC, TiSi and Ti5Si3. The elemental analysis was qualitatively estimated using SIMS analysis.     

Distribution of macro-inclusions in low carbon aluminium-killed steel slabs

Macro-inclusions in low carbon, aluminium-killed steel slabs were characterised by step-machining within a 10?mm zone from the slab surface using an ASPEX automatic inclusion analyzer. Dendritic structures within the cross-section of slabs were examined. The results show that alumina clusters and alumina associated with bubbles are the dominant macro-inclusions. Along the slab width direction, macro-inclusions were mostly found at the slab centre because of the deeper hooks and freezing meniscus surrounding the submerged entry nozzle. In terms of slab thickness, inclusions were mainly concentrated within the zone 3.5–6?mm from the top of the slab surface, where the columnar dendrites showed a relatively small inclination angle, indicating small cross-flow velocities at the solidification front. The number density of macro-inclusions were strongly dependent on the washing effect produced by the flow velocity. High speed casting promotes this behaviour and improves the surface quality of the slabs.     

等轴晶在对流金属液中非稳态移动的物理及数学模型

本文通过两相流理论,对金属凝固过程中等轴晶在对流金属液中的游离移动现象建立了非稳态数学模型,并推导了求解等轴晶在非稳态,非均匀液相流场中做非稳态移动的数值表达式。进一步建立了描述等轴晶在对流金属液中迁移和堆积规律的局部堆积方程式。