Si基锂离子电池负极材料研究进展

硅具有高的理论比容量、较低的嵌锂电位、来源广泛且环境友好等优点,被认为是下一代锂离子电池负极材料的有力竞争者。然而,在锂离子脱嵌过程中巨大的体积膨胀引起了活性材料的粉化和破裂,这带来了电极循环性能差、容量衰减快甚至电极失效等一系列问题。迄今为止,有大量关于改性硅基材料的报道。本文将重点介绍硅基材料的纳米结构化设计和硅/碳材料的结合。首先,分析了硅的储锂及失效机制,从机理上理解硅的失效对其电化学性能的影响。其次,从理论上阐述了纳米级硅材料对缓解体积效应的机理,从结构设计、材料合成、形态特征和电化学性能等方面论证了纳米硅材料的优势。随后,从缓解体积膨胀、提高电导率和形成稳定的固体电解质（SEI）膜等方面总结了硅碳复合材料的研究进展。此外,还讨论了将导电聚合物和金属引入硅基材料的电化学性能增强机理。最后,从提高首次库仑效率、SEI膜稳定性和质量负载量等方面对硅基材料的产业化应用提出几点建议。     

利用添加剂调控铂晶面结构提高氧还原催化性能的研究现状

基于质子交换膜燃料电池（PEMFC）的转换效率主要受阴极氧还原反应（ORR）动力学缓慢的限制,设计高效稳定的低铂催化剂,对于降低PEMFC产业化应用的成本和提高催化性能至关重要。目前,研究人员已对此开展广泛研究,并取得了丰硕成果,开发包括具有可调晶面、高指数晶面、Pt-M（M为过渡金属）合金的Pt纳米结构。本文从利用不同添加剂调控Pt基催化剂晶面结构和形貌以促进氧还原电催化性能的角度着手,综述了保护剂、络合剂、封端剂、还原剂、分散剂等常用添加剂对Pt基催化剂正四面体、立方体、八面体以及具有高指数晶面的凹纳米立方体等晶面结构进行调控的研究进展,在湿化学法、电沉积法、合金法、溶剂热法等不同研究方法中添加剂在调控晶面结构和提高催化性能方面发挥的作用,并对Pt基催化剂中Pt晶面调控在未来面临的挑战和发展方向做了简要总结。     

A very low energy compact electron beam ion trap for spectroscopic research in Shanghai

In this paper, a new compact low energy electron beam ion trap, SH-PermEBIT, is reported. This electron beam ion trap (EBIT) can operate in the electron energy range of 60-5000 eV, with a current density of up to 100 A/cm(2). The low energy limit of this machine sets the record among the reported works so far. The magnetic field in the central drift tube region of this EBIT is around 0.5 T, produced by permanent magnets and soft iron. The design of this EBIT allows adjustment of the electron gun's axial position in the fringe field of the central magnetic field. This turned out to be very important for optimizing the magnetic field in the region of the electron gun and particularly important for low electron beam energy operation, since the magnetic field strength is not tunable with permanent magnets. In this work, transmission of the electron beam as well as the upper limit of the electron beam width under several conditions are measured. Spectral results from test operation of this EBIT at the electron energies of 60, 315, 2800, and 4100 eV are also reported.     

Nitrogen removal from eutrophic water by floating-bed-grown water spinach (Ipomoea aquatica Forsk.) with ion implantation

The aim of this study was to investigate the use of water spinach (Ipomoea aquatica Forsk.) with N(+) ion-beam implantation for removal of nutrient species from eutrophic water. The mutated water spinach was grown on floating beds, and growth chambers were used to examine the growth of three cultivars of water spinach with ion implantation for 14 days in simulated eutrophic water at both high and low nitrogen levels. The specific weight growth rates of three cultivars of water spinach with ion implantation were significantly higher than the control, and their NO(3)-N and NH(4)-N removal efficiencies were also greater than those of the control. Furthermore, compared with the control, the nitrogen contents in the plant biomass with ion implantation were higher as well.     

脉冲偏压对电弧离子镀Ti/TiN纳米多层薄膜显微硬度的影响

采用脉冲偏压电弧离子镀方法在高速钢基体上沉积Ti／TiN纳米多层薄膜,采用正交实验法设计脉冲偏压电参数,考察脉冲偏压对Ti／TiN纳米多层薄膜显微硬度的影响．结果表明,在所有偏压参数（脉冲偏压幅值、占空比和频率）和几何参数（调制周期和周期比）中,脉冲偏压幅值是影响显微硬度的最主要因素;当沉积工艺中脉冲偏压幅值为900V、占空比为50％及频率为30kHZ时,薄膜硬度可高达34．1GPa,此时多层膜调制周期为84nm,TiN和Ti单元层厚度分别为71和13nm;由于薄膜中的单层厚度较厚,纳米尺寸的强化效应并未充分体现于薄膜硬度的贡献中,硬度的提高主要与脉冲偏压工艺,尤其是脉冲偏压幅值对薄膜组织的改善有关．     

Influence of aging behavior of Armos fiber after oxygen plasma treatment on its composite interfacial properties

This work concerns the aging behavior of Armos fiber and Armos fiber reinforced poly (phthalazinone ether sulfone ketone) (PPESK) composite after oxygen plasma treatment. Armos fiber surface chemical composition, surface morphology and roughness, and surface wettability as a function of storage time in air after oxygen plasma treatment were measured by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic contact angle analysis (DCAA) system, respectively. The fiber surface aging behavior could be detected obviously in chemical composition and surface wettability, whereas the surface morphology and roughness remained nearly stable after storing in air as long as 10 days after oxygen plasma treatment. The effects of surface aging behavior after oxygen plasma treatment on Armos fiber reinforced PPESK composite interfacial properties were evaluated by interlaminar shear strength (ILSS) test and humid resistance measurement. It was found that the values of ILSS reduced and the composite humid resistance properties decayed. The polar functional groups that were reoriented from the surface into the bulk of the fibers or moved away from the fiber surfaces, maybe responsible for the weak interfacial strength between the fiber and the matrix in composite system.     

Mn1.3Fe0.7P0.45Si0.55化合物的热滞与磁热效应

用机械合金化方法制备出了Mn1.3Fe0.7P0.45Si0.55化合物。研究了Mn1.3Fe0.7P0.45Si0.55化合物的结构、磁性和磁热效应。结果表明,该化合物形成了Fe2P型六角结构,空间群为P62m,化合物中存在少量的(Mn,Fe)3Si相。在居里点附近,随着温度的提高化合物发生了由铁磁到顺磁的一级相变过程。化合物的Curie温度为315K,热滞为4K。在1.5T磁场变化下,化合物的最大等温磁熵变为10.3J/(kg.K)。低成本的原料、简单的制备工艺、合适的Curie温度、较小的热滞和较大的磁熵变,使得Mn1.3Fe0.7P0.45Si0.55化合物有希望成为一种可应用的新型室温磁制冷材料。     

应变速率对金属动态再结晶影响的数值模拟

采用元胞自动机方法建立了多晶金属材料塑性加工过程动态再结晶的二维模型,模拟了动态回复、位错密度变化和动态再结晶的微观结构演化等一系列过程。利用该模型可得到晶粒形态及晶粒的取向和大小,模拟结果很好地描述了动态再结晶的生长动力学特征,并动态地再现了实验方法观察到的动态再结晶的微观组织特征。在该模型的基础上,分析了应变速率对动态再结晶过程,以及动态再结晶晶粒尺寸的影响。     

Nanometer-thick SGOI structures produced by Ge+ ion implantation of SiO2 films and subsequent hydrogen transfer of Si layers

Nanometer-thick silicon-germanium-on-insulator (SGOI) structures have been produced by the implantation of Ge⁺ ions into thermally grown SiO₂ layer and subsequent hydrogen transfer of silicon film on the Ge⁺ ion implanted substrate. The intermediate nanometer-thick Ge layer has been formed as a result of the germanium atom segregation at the Si/SiO₂ bonding interface during annealing at temperatures 800–1100 ^оС. From a thermodynamic analysis of Si/Ge/SiO₂ system, it has been suggested that the growth of the epitaxial Ge layer is provided by the formation of a molten layer at the Si/SiO₂ interface due to the Ge accumulation. The effect of germanium on the hole mobility in modulation-doped heterostructures grown over the 3–20 nm thick SGOI layers was studied. An increase in the Hall hole mobility in SGOI-based structures by a factor of 3–5 was obtained in comparison with that in respective Ge-free SOI structures.