表面科学研究回顾与21世纪发展展望

表面与界面是材料物理、化学性质发生空间突变的二维区域,材料的许多重要物理、化学过程首先发生在表面,同时材料的很多破坏和失效也首先起源于表面和界面。因此,表面是材料与外部环境直接发生联系的窗口,从研究材料表面界面的各种物理化学过程入手最终可以达到改善材料性能的目的。过去１０年中,材料表面科学在促进材料科学基础研究、推动新材料新技术发展中发挥了关键作用。世纪之交乃至下一世纪,表面科学将面临新的挑战和机     

Non-contact in-situ pulsed electro acoustic method for the analysis of charge transport in irradiated space-used polymers

The characterization of dielectric materials in space environment requires to understand and predict their electric behaviour, taking into account ionisation, and ageing effect (through electron or UV radiation, thermal cycling, …)For this purpose, new methods have been developed for the characterisation and qualification of space materials and satellite structure. These studies led initially to the development of dedicated facilities for the simulation of representative irradiation conditions. This work is focused on a new non-disturbing technique for the measurement of charge distribution within space irradiated polymers. This technique named PEA (Pulsed Electro-Acoustic) has been implemented in the irradiation facility for in-situ and real time measurement during irradiation and relaxation of polymer materials. Implementation and validation of this technique are presented and discussed in this paper.     

高感光度测定研究

研究了感光材料高感光度测定方法 ,并将工作标准感光仪改造成适合高感光度范围的感光测定仪 ,解决了现有感光仪无法测定高感光度的问题。     

sp3sTight-binding parameters for transport simulations in compound semiconductors

A genetic algorithm approach is used to fit orbital interaction energies of sp3s* tight-binding models for the nine binary compound semiconductors consistent of Ga, Al, In and As, P, Sb at room temperature. The new parameters are optimized to reproduce the bandstructure relevant to carrier transport in the lowest conduction band and the highest three valence bands. The accuracy of the other bands is sacrificed for the better reproduction of the effective masses in the bands of interest. Relevant band edges are reproduced to within a few meV and the effective masses deviate from the experimental values typically by less than 10%.     

中低Z材料辐射烧蚀实验研究

 在星光Ⅱ激光装置上,利用波长为0.35μm的激光注入柱腔金箔靶产生的金箔后向X光作源,烧蚀中低Z样品材料,通过空间分辨测量靶源区和样品自发辐射X光的时间过程获得了中Z铝材料的辐射烧穿时间结果;在北京同步辐射源上对透射光栅进行了实验标定。     

Cu对用于高速相变存储器的Sb2Te薄膜的结构及相变的影响研究

采用原位X射线衍射仪、拉曼光谱仪和X射线反射仪分别研究了Cu-Sb₂Te 薄膜的微结构、成键结构和结晶前后的密度变化. Sb₂Te薄膜的结晶温度随着Cu含量的增加而增大. 在10 at.%和14 at.% Cu的Sb₂Te薄膜中, Cu与 Te 成键, 结晶相由六方相的Cu₇Te₄、菱形相的Sb及六方相的Sb₂Te构成. 10 at.% 和14 at.% Cu 的Sb₂Te薄膜在结晶前后的厚度变化分别约为3.2%和 4.0%, 均小于传统的Ge₂Sb₂Te₅ (GST)薄膜. 制备了基于Cu-Sb₂Te薄膜的相变存储单元, 并测试了其器件性能. Cu-Sb₂Te器件均能在10 ns的电脉冲下实现可逆SET-RESET操作. SET和RESET操作电压随着Cu含量的增加而减小. 疲劳测试结果显示, Cu 含量为10 at.%和14 at.%的PCRAM单元的循环操作次数分别达到1.3×10⁴和1.5×10⁵, RESET和SET态的电阻比值约为100. Cu-Sb₂Te可以作为应用于高速相变存储器(PCRAM)的候选材料.     

MNZ超材料的电磁特性

主要围绕磁导率接近0的MNZ超材料,通过理论分析和数值模拟方法对MNZ材料的电磁特性进行了研究。针对线源置于二维MNZ材料内部的情况,通过理论详细分析了在MNZ材料和空气交界处的阻抗匹配特性和传播常数的连续性,基于有限元数值方法模拟验证了电磁场在MNZ材料边界处的等幅同相特性,从而实现了均匀平面波的传播特性。同时,考虑到将线源置于空气中有助于辐射出电磁能量,通过数值模拟分析了电磁波由空气入射到MNZ材料的电磁特性,发现在特定极化条件下,只能当电磁波波前与MNZ材料边界平行时,才能较好地实现阻抗匹配,从而基于MNZ材料实现新颖的辐射特性。     

纯电动汽车磷酸铁锂电池组的建模及优化

鉴于传统神经网络和支持向量机机理复杂、计算量大的缺陷,很难实时跟踪磷酸铁锂电池组复杂快速的内部反应,影响电池荷电状态的估算精度,提出应用一种简单、有效的极限学习机对一额定容量为100Ah、额定电压为72V的纯电动汽车磷酸铁锂电池组建模,并分别与BP神经网络、RBF神经网络、支持向量机进行对比。随后,以学习时间和泛化性能为优化目标,应用粒子群方法寻找最佳隐层节点个数。结果表明,基于极限学习机的磷酸铁锂电池组模型的学习时间、泛化性能优于BP神经网络、RBF神经网络、支持向量机;隐层节点优化后,模型的学习时间和泛化性能达到最优。     

Sulfur Immobilized in Hierarchically Porous Structured Carbon as Cathodes for Lithium–Sulfur Battery with Improved Electrochemical Performance

In order to overcome the main obstacles for lithium–sulfur batteries, such as poor conductivity of sulfur, polysulfide intermediate dissolution, and large volume change generated during the cycle process, a hard‐template route is developed to synthesize large‐surface area carbon with abundant micropores and mesopores to immobilize sulfur species. The microstructures of the C/S hybrids are investigated using field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherms, and electrochemical impedance spectroscopy techniques. The large surface and porous structure can effectively alleviate large strain due to the lithiation/delithiation process. More importantly, the micropores can effectively confine small molecules of sulfur in the form of S_2–4, avoiding loss of active S species and dissolution of high‐order lithium polysulfides. The porous C/S hybrids show significantly enhanced electrochemical performance with good cycling stability, high specific capacity, and rate capability. The C/S‐39 hybrid with an optimal content of 39 wt% S shows a reversible capacity of 780 mA h g^?1 after 100 cycles at the current density of 100 mA g^?1. Even at a current density of 5 A g^?1, the reversible capacity of C/S‐39 can still maintain at 420 mA h g^?1 after 60 cycles. This strategy offers a new way for solving long‐term reversibility obstacle and designing new cathode electrode architectures.     

基于单粒子模型与偏微分方程的锂离子电池建模与故障监测

锂离子电池内部结构是一种复杂的分布参数系统, 如果为了降低计算难度而使用常微分方程描述锂离子电池, 可能会引入系统误差, 降低系统模型的可信度, 需要使用偏微分方程建立分布参数系统的精确模型. 本文提出了一种基于单粒子模型和抛物型偏微分方程的锂离子电池系统建模与故障监测系统设计方法, 当锂离子浓度实测值与理想值的残差大于预设门槛时判定分布参数系统处于故障状态. 通过一个仿真实例进行了锂离子电池系统建模和故障诊断实验, 实验证明基于单粒子模型和偏微分方程的锂离子电池故障监测系统具有更高的精确度和可信度.