纳米晶Li7Si3合金的制备与性能表征

为研究纳米结构锂电池阳极材料的特性,试制了纳米晶Li-Si合金.采用优化的纳米晶合金块体材料制备工艺,即熔炼制备粗晶Li7Si3合金铸锭、高能球磨得到Li7Si3非晶粉末,结合放电等离子烧结(spark plasma sintering,SPS)制备得到了纳米晶Li7Si3合金,并对其进行了Rietveld结构精修和杨氏模量测定.结果表明:纳米晶Li7Si3单胞结构参数为a=b=0.4452 nm(比粗晶增加0.38%),c=1.8239 nm(比粗晶增加0.58%),单胞体积Vo=0.313 070nm3(比粗晶增加1.35%).利用纳米压痕法测定纳米晶Li7Si3合金的杨氏模量为(30.6±2.4)GPa.     

Tuning fermi level and band gap in Li4Ti5O12 by doping and vacancy for ultrafast Li+ insertion/extraction

Li₄T_i5O₁₂ (LTO) attracts great interest due to the “zero strain” during cycles but the poor electronic and ionic conductivity critically impede the practical application. Herein, we report a synergy strategy of tuning localized electrons to shift Fermi level and band gap by Mg/Zr co-doping and oxygen vacancy incorporation, which significantly improves Li⁺ and electronic transport. More importantly, the intrinsic synergistic mechanism has been revealed by neutron diffraction, X-ray absorption spectra, and first-principles calculations. The “elastic effect” of lattice induced by Mg/Zr co-doping allows LTO to accommodate more oxygen vacancies to a certain degree without a severe lattice distortion, which largely improves the electronic conductivity. Mg/Zr co-doping and oxygen vacancy incorporation effectively enhanced the dynamic characteristics of LTO electrode, achieving the excellent rate performance (90 mAh/g at 20C) and cycle stability (96.9% after 500 cycles at 10C). First-principles calculations confirm Fermi level shifts to the conduction band, and the band gap becomes narrowed due to the synergistic modulation, and the intrinsic mechanism of the enhanced electronic and Li-ion conductivity is clarified. This study offers some insights into achieving the fast Li⁺ insertion/extraction by tuning the crystal and electronic structure with lattice doping and oxygen vacancy engineering.     

GH4169高温合金惯性摩擦焊的有限元模拟

基于Ansys有限元分析软件,建立了GH4169高温合金惯性摩擦焊过程的二维模型,进行了热力耦合分析,得到了焊接过程中的瞬时温度场和应力应变场,获得了焊接缩短量。根据惯性摩擦焊工艺分析了温度场和应力应变场的形成过程。     

细晶处理对镍基合金疲劳蠕变交互作用行为的影响

本文研究了两种晶粒度的GH 698合金在700℃疲劳蠕变交互作用下的断裂寿命和形变行为.结果表明:在疲劳蠕变应力交互作用下的断裂寿命可以分成F,FC和C三个区.在FC及C区,交变应力的存在明显地阻碍蠕变形变过程,提高了断裂寿命.细晶处理后使这种阻碍作用加强,断裂寿命提高幅度变大.在大应力的疲劳区进行细晶处理,反而使合金寿命降低.     

冷轧对GH4169合金组织与性能的影响

采用X射线衍射技术及透射电子显微镜研究了冷轧变形道次及不同变形量对GH4169合金中金属间化合物γ″相和δ相的分布，形貌，数量及性能的影响，结果表明：随着变形程度的增加，析出相由晶内和和晶界析出逐渐转变到形变带及位错墙处析出，γ″相的尺寸逐渐减小，γ″、δ相的析出含量以及材料的强度逐渐增加，双道次冷轧变形提高了δ相的含量，但降低了γ″相的析出量和材料的强度。     

电场固溶对2091A1-Li合金显微结构的影响

用电子探针及透射电镜研究了２０９１ＡｌＬｉ合金的电场固溶对显微结构的影响。结果发现，电场固溶通过促进含铜相溶解提高铜元素的固溶程度，加剧Ｌｉ原子在晶界上的非平衡偏聚，导致析出相δ′分布不均匀，体积分数减少，晶界上出现粗大的δ平衡相，Ｔ１及Ｓ′相均匀弥散分布，合金的力学性能（Ｔ６）达到了应变时效处理（Ｔ８）的水平。     

GH4169线性摩擦焊接头的焊合率与弯曲强度

论述了高温合金GH4169线性摩擦焊的试验过程。分析了弯曲强度、断裂挠度与焊合率之间的关系及接头的金相组织。结果表明,GH4169线性摩擦焊接头的弯曲强度与焊合率成正比线性关系,断口为韧性断口;断裂强度受摩擦时间的影响较大。     

某航空发动机第三级涡轮叶片失效分析

本文对某型号航空发动机GH4033第三级涡轮叶片榫头裂纹及断裂失效进行了分析,确定了失效模式为两类,第一类为蠕变疲劳裂纹,第二类为起始应力较大的高低周复合疲劳断裂.研究发现GH4033合金屈服强度偏低、晶界强化能力不足是叶片发生蠕变疲劳开裂的主要原因.而叶片的高低周复合疲劳断裂则主要与个别相邻叶片的叶冠间隙偏大引发的高振动弯曲应力及R处加工刀痕引发的应力集中有关.最后提出了预防叶片发生该类失效的措施.     

Scavenging of “Dead Sulfur” and “Dead Lithium” Revealed by Integrated–Heterogeneous Catalysis for Advanced Lithium–Sulfur Batteries

The simultaneous engineering of sulfur cathode and Li anode is critical for electrolyte-starved high energy density Li–S batteries, in which slow electrochemical conversions and side chemical reactions of dead sulfur are found to be the determining factors in limiting the sulfur utilization, corresponding to the poor reversible capacity of Li–S batteries. Herein, this work challenges the conventional wisdom of heterogeneous and homogeneous catalyses in Li–S batteries and proposes the concept of integrated–heterogeneous catalysis to simultaneously scavenge the dead sulfur and dead lithium to compensate the active materials sulfur and lithium loss simply through adding a small amount of ZnI₂ into conventional electrolyte of Li–S cells. Regulated by integrated–heterogeneous catalysis, over 1300 h of cycling is realized in Li||Li symmetric cells, revealing superb compatibility of the ZnI₂-incorporated electrolyte with lithium metal. Meanwhile, the ZnI₂ shows good prospects in promoting the reutilization of dead sulfur in both theoretical calculation and experimental tests. Practically, a high initial capacity of 1170 mAh g⁻¹ with decent cycling stability is achieved in electrolyte-starved and high-loading pouch cells (5.0 µL mg⁻¹ and 5.2 mg cm⁻²).     

Fast Ion Transport in Li-Rich Alloy Anode for High-Energy-Density All Solid-State Lithium Metal Batteries

All-solid-state Li batteries (ASSLBs) with solid-polymer electrolytes are considered promising battery systems to achieve improved safety and high energy density. However, Li dendrite formation at the Li anode under high charging current density/capacity has limited their development. To tackle the issue, Li-metal alloying has been proposed as an alternative strategy to suppress Li dendrite growth in ASSLBs. One drawback of alloying is the relatively lower operating cell voltages, which will inevitably lower energy density compared to cells with pure Li anode. Herein, a Li-rich Li₁₃In₃ alloy electrode (LiRLIA) is proposed, where the Li₁₃In₃ alloy scaffold guides Li nucleation and hinders Li dendrite formation. Meanwhile, the free Li can recover Li's potential and facilitate fast charge transfer kinetics to realize high-energy-density ASSLBs. Benefitting from the stronger adsorption energy and lower diffusion energy barrier of Li on a Li₁₃In₃ substrate, Li prefers to deposit in the 3D Li₁₃In₃ scaffold selectively. Therefore, the Li–Li symmetric cell constructed with LiRLIA can operate at a high current density/capacity of 5 mA cm⁻²/5 mAh cm⁻² for almost 1000 h.