时效处理对AA2099铝锂合金摩擦学行为的影响

研究了固溶及不同时效状态AA2099铝锂合金的力学性能、摩擦学行为及机理.结果表明:随时效时间的延长,摩擦系数先降低后升高,时效35 h时摩擦系数最低(0.137);磨损量单调减少,时效96 h合金的磨损率最低,为1.7×10–3 mm3/(N·m).固溶态和不同时效态的AA2099铝锂合金主要磨损机制均为磨粒磨损和黏着磨损.摩擦产物对摩擦系数有重要影响,时效35 h的合金摩擦产物分布均匀且连续,具有良好的减摩作用;合金的力学性能与磨痕浅层结构稳定性共同影响合金的磨损率,时效时间小于35 h,合金表面易形成发生剥落的结构,磨损量变化与传统认为的H/E变化不符,但随时效时间进一步延长,剥落减少,磨损量与H/E变化正相关.     

An improved method of detecting and processing for the beacon in satellite-to-ground laser communication links

In satellite-to-ground laser communication links, the motion and vibration of the satellite are important factors that affect the real-time requirements of pointing, acquiring, and tracking. In order to acquire again the beacon quickly and accurately after losing it for a short time, we propose an improved method of detecting and processing for the beacon. In contrast to the conventional design of processing systems for the beacon, the advantage of the system we designed is provided by the spatial environment, where the optical communication terminal is located, and the motion trace of the beacon can be predicted effectively. We perform numerical simulations and simulation experiments, with a sampling frequency of the CCD in a system of 60 Hz and frequency and amplitude of the simulation vibration signal of 1 Hz and 0.1 mrad, respectively. We assume the motion of the satellite to be of translation type. The prediction precision is not more than 6 pixels of the CCD after the algorithm converges and the experimental results correspond fairly to the numerical simulation.     

Ternary Monolithic ZnS/CdS/rGO Photomembrane with Desirable Charge Separation/Transfer Routes for Effective Photocatalytic and Photoelectrochemical Hydrogen Generation

Highly efficient and easy recyclable monolithic photocatalysts with ideal separation/transport route for photogenerated charge carriers are much desired. In this work, a ZnO seed‐induced growth approach is developed to fabricate a ternary monolithic photomembrane, that is, ZnS/CdS heterojunction nanorods in situ grow into the interspaces of multilayer reduced graphene oxide (rGO) sheets (denoted as ZnS/CdS/rGO). The monolithic ZnS/CdS/rGO photomembrane can serve as an efficient visible‐light photoactive membrane for photocatalytic (PC) or photoelectrochemical (PEC) hydrogen generation. The fast electron transport of 1D CdS nanorods, the excellent electronic conductivity of multilayer stacked rGO sheets, the intense visible‐light absorption of CdS, the unique hierarchical structure, and double heterojunctions (ZnS/CdS and CdS/rGO) efficiently boost the photogenerated electron‐hole pairs separation and transfer across the interfacial domain of the photomembrane under visible‐light irradiation. Furthermore, the superior stability and reusability of the photomembrane is achieved by the ideal process of photogenerated electron‐hole pair separation/transfer, i.e., holes transfer to ZnS and electrons transfer to rGO to inhibit CdS from photocorrosion.     

机械载荷作用下单边裂纹载流薄板的应力场

采用坐标变换的方式,将单边裂纹载流薄板通电瞬间由温度产生的应力场表达式中的各应力分量分离,并用极坐标进行表示．给出了Ⅰ型穿透裂纹尖端附近的应力场的表达式．最后将温度产生的应力场与单向拉伸载荷作用产生的应力场相叠加,推导出用极坐标表示的机械载荷作用下单边裂纹载流薄板的应力场的表达式,并给出算例．     

Rare Earth Evoked Subsurface Oxygen Species in Platinum Alloy Catalysts Enable Durable Fuel Cells

Alleviating the degradation issue of Pt based alloy catalysts, thereby simultaneously achieving high mass activity and high durability in proton exchange membrane fuel cells (PEMFCs), is highly challenging. Herein, we provide a new paradigm to address this issue via delaying the place exchange between adsorbed oxygen species and surface Pt atoms, thereby inhibiting Pt dissolution, through introducing rare earth bonded subsurface oxygen atoms. We have succeeded in introducing Gd−O dipoles into Pt₃Ni via a high temperature entropy-driven process, with direct spectral evidence attained from both soft and hard X-ray absorption spectroscopies. The higher rated power of 0.93 W cm⁻² and superior current density of 562.2 mA cm⁻² at 0.8 V than DOE target for heavy-duty vehicles in H₂-air mode suggest the great potential of Gd−O−Pt₃Ni towards practical application in heavy-duty transportation. Moreover, the mass activity retention (1.04 A mg_Pt⁻¹) after 40 k cycles accelerated durability tests is even 2.4 times of the initial mass activity goal for DOE 2025 (0.44 A mg_Pt⁻¹), due to the weakened Pt−O_ads bond interaction and the delayed place exchange process, via repulsive forces between surface O atoms and those in the sublayer. This work addresses the critical roadblocks to the widespread adoption of PEMFCs.     

Theoretical Investigation of the Fusion Process of Mono-Cages to Tri-Cages with CH4/C2H6 Guest Molecules in sI Hydrates

Owing to a stable and porous cage structure, natural gas hydrates can store abundant methane and serve as a potentially natural gas resource. However, the microscopic mechanism of how hydrate crystalline grows has not been fully explored, especially for the structure containing different guest molecules. Hence, we adopt density functional theory (DFT) to investigate the fusion process of structure I hydrates with CH₄/C₂H₆ guest molecules from mono-cages to triple-cages. We find that the volume of guest molecules affects the stabilities of large (5¹²6², L) and small (5¹², s) cages, which are prone to capture C₂H₆ and CH₄, respectively. Mixed double cages (small cage and large cage) with the mixed guest molecules have the highest stability and fusion energy. The triangular triple cages exhibit superior stability because of the three shared faces, and the triangular mixed triple cages (large-small-large) structure with the mixed guest molecules shows the highest stability and fusion energy in the triple-cage fusion process. These results can provide theoretical insights into the growth mechanism of hydrates with other mono/mixed guest molecules for further development and application of these substances.     

Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体的角重迭参数计算

本文使用角重迭模型(AOM),针对Eu3+:Ln2O2S(Ln=Lu,Y,Gd,La)晶体系列,在考虑硫和氧两种不同格位的情况下,对f电子的全部四个角重迭参数eσ、eπ、eδ和eφ进行了计算,得到了一些基本规律,即中心离子与配位体之间的共价性大小次序为Lu～Y>Gd>La,并且Ln-O键的共价性要强于Ln-S键.     

N原子对取代NH_4H_2PO_4盐类晶体的二次谐波发生的影响(英文)

从N—H键在取代NH4H2 PO4盐的 [AH]4 [H2 PO4]类晶体中的突出作用出发 ,作者对几个 [AH]4 [H2 PO4]型晶体的二次谐波发生进行理论上的研究 (这里A =伯、仲、叔胺 )。并对这一类晶体的二次谐波发生和其亚结构单元 [AH]+ 中N原子上的净电荷之间的依赖关系进行了估计。     

SmP5O14晶体中Sm3+离子的能级和晶场参数

本文利用光谱方法测定了SmP5O14晶体中Sm3+离子的能级,通过拟合定出晶场参数,利用这些参数所计算的能级和实验能级符合得很好。