A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250 mA h g⁻¹). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta⁵⁺ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta⁵⁺ doped LLO at 5 C is 155 mA h g⁻¹, while it is only 122 mA h g⁻¹ for bare LLO. Theoretical calculations reveal that Ta⁵⁺ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.     

Enhanced photooxidative desulphurization of dibenzothiophene over fibrous silica tantalum: Influence of metal-disturbance electronic band structure

Fibrous silica tantalum (FSTa) and a series of metal oxides (silver oxide (AgO), copper oxide (CuO) and zinc oxide (ZnO)) supported on FSTa were prepared by hydrothermal and electrochemical method, respectively. X-ray diffraction, nitrogen adsorption-desorption analyses, Fourier-transform infrared, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence were used to characterize the catalysts. The catalyst activity towards on photocatalytic oxidative desulfurization (PODS) of 100 mg L^?1 dibenzothiophene (DBT) was ranked in the following order: FSTa (3.03 × 10^?3 mM min^?1) > Zn/FSTa (2.65 × 10^?3 mM min^?1) > Cu/FSTa (2.33 × 10^?3 mM min^?1) > Ag/FSTa (1.46 × 10^?3 mM min^?1) under visible light irradiation for 150 min. This result demonstrated that the addition of metal oxides lowered the efficiency of PODS of DBT, most probably due to the unfit energy level of the photocatalyst towards redox potentials of superoxide anion radical (?O₂^?) and hydroxyl radical (?OH). Nevertheless, among the metal oxides loaded FSTa, Zn/FSTa showed a higher desulfurization rate, which likely due to its higher valence band energy (E_VB = 3.12 eV) than the redox potential of the H₂O/?OH (+2.4 eV vs. NHE), which allowed the production of ·OH for oxidation of DBT into dibenzothiophene sulfone (DBTO₂). In parallel, the hole at the VB of ZnO can also directly oxidize DBT to DBTO_2, as confirmed by the scavenger experiment. A kinetics study using Langmuir–Hinshelwood model illustrated that the photodegradation over Zn/FSTa followed the pseudo-first-order, and adsorption was the rate-limiting step. These findings are believed to aid in the rational design of high-performance photocatalysts for various photocatalytic applications, especially the removal of sulphur-containing compounds from fuel oils.     

Erosive wear behavior of spark plasma-sintered SiC–TaC composites

Spark plasma sintering of SiC-10, 20, or 30 wt% TaC composites was performed at 1800°C. Microstructures of sintered composites revealed uniform dispersion of TaC particles in SiC matrix. With the increase in TaC content, hardness decreased from 25.75 to 23.30 GPa and fracture toughness increased from 3.48 to 3.85 MPa m^1/2. Erosion testing was performed to evaluate the potential of sintered composites at room temperature and 400°C by a stream of SiC particles impinging at different angles (30°, 60°, or 90°). The erosion rate varied from 25 to 166 mm³/kg, with change in TaC content, impingement angle, or temperature. The erosion rate increased as the angle of impingement and temperature increased, but reduced when the TaC concentration increased. Worn surfaces revealed that the material was dominantly removed via fracture of SiC grains and TaC particles pull-out. SiC-30 wt% TaC composites exhibited superior erosive wear resistance at low impingement angle and room temperature.     

影响气相沉积用钽丝性能的因素研究

以不同的冶金级钽粉为原料,通过相同的加工工艺试制成相同规格的钽丝,经过对钽丝产品机械性能、抗氧脆性、抗氢脆性以及表面质量的分析,确定气相沉积用钽丝一定要采用普通钽粉来制取,此外可以通过增大加工率来增加钽丝的抗拉强度。     

钽条闪光对焊工艺参数对其组织性能的影响

为解决连续化生产中钽条焊接的技术难题,在惰性气体的保护下采用电容储能式预热闪光对焊,对轧制后的4 mm×4 mm钽条进行焊接试验研究.利用金相显微镜、扫描电镜和力学性能检测设备等分析检测手段,对不同焊接顶锻力作用下的焊接区(包括热影响区)的显微组织、晶粒和晶界微区成分、硬度以及焊接区拉伸强度等进行了测试.研究表明,采用合适的闪光对焊工艺可以实现大尺寸钽条的对接,焊缝组织致密,接头具有较高的结合强度,对于大尺寸钽条无头轧制与连续拉拔技术的发展具有一定的使用价值.     

纯钽表面微弧氧化“类骨小梁”状多孔涂层的细胞相容性

目的 提高医用纯钽的生物活性，利用微弧氧化(MAO)技术在其表面制备出“类骨小梁”状分级多孔涂层，并对比该涂层与传统“火山坑”状MAO涂层以及机械抛光纯钽表面在表面粗糙度、亲水性以及细胞相容性方面的差异。方法 使用0.1 mol/L Na₂B₄O₇和0.05 mol/L Na₃PO₄电解液在纯钽表面分别制备出“类骨小梁”状及“火山坑”状多孔涂层(分别命名为B-MAO和P-MAO涂层)。采用扫描电镜、X射线衍射以及X射线光电子能谱对不同结构涂层进行形貌观察和相组成分析，使用十字划格法评价涂层结合强度，使用激光共聚焦显微镜测定涂层的表面粗糙度，使用接触角仪测量其亲水性，并将小鼠前成骨细胞(MC3T3-E1)接种于材料表面，对比不同形貌状态对细胞铺展、增殖以及成骨分化的影响。结果 MAO涂层物相主要为Ta₂O₅。B-MAO涂层由于内部孔隙度高，应力释放充分，涂层结合强度高，而P-MAO涂层则因具有分层现象和较大的残余应力，易从基体剥落。抛光...     

退火温度对高纯钽棒再结晶织构及力学行为的影响

本文对冷变形后的高纯钽棒进行不同温度(850~1050℃)的退火处理,研究了退火后的微结构及织构演变规律、再结晶形核与取向的依赖性以及再结晶组织对其力学行为的影响。结果表明,冷变形组织呈{100}和{111}取向分布的纤维状结构,以()[]组分为主的α-织构。退火处理后,高纯钽棒组织分别处于回复阶段(850℃)、完全再结晶(950℃)以及晶粒长大阶段(1050℃)。随着退火温度的增加,α-织构逐渐弱化,γ-织构逐渐形成,尤其是完全再结晶后,α-织构组分完全消失。屈服强度和应变硬化能力随着退火温度的增加而降低,塑韧性得到明显改善,完全再结晶时均匀伸长率达到17.85%。当温度增加到1050℃时,二次再结晶晶粒容易发生沿晶断裂,力学性能较差。     

钽表面划痕过程声发射特性

以集成电路阻挡层材料钽为对象,研究其表面划痕过程中的声发射特性,初步探索材料去除机制,分析划痕参数对声发射特性的影响,为采用声发射技术监测材料去除过程提供依据。结果显示:在划痕过程中,钽交替经历犁沟和塑性流动,形成深浅起伏的沟槽,并产生连续型声发射信号;随着划痕速度增加,信号强度增高,包络波动更剧烈,冲击性更强,而中位频率先升高、后稳定甚至降低;随着划痕载荷增加,信号增强,冲击性呈正相关变化。钽的表面划痕过程可以用声发射表征。