航空发动机用光纤叶片振动传感探头的研制

主要介绍了一种制作光纤叶片振动传感器探头的新工艺,该工艺选用特殊的大芯径精密陶瓷插芯,采用了一种创新性的光纤定位技术,利用该工艺制作的光纤叶片振动传感探头经试验验证完全满足航空发动机叶片振动参数的测量要求.     

Self‐Assembled Room Temperature Multiferroic BiFeO3‐LiFe5O8 Nanocomposites

Multiferroic materials have driven significant research interest due to their promising technological potential. Developing new room‐temperature multiferroics and understanding their fundamental properties are important to reveal unanticipated physical phenomena and potential applications. Here, a new room temperature multiferroic nanocomposite comprised of an ordered ferrimagnetic spinel α‐LiFe₅O₈ (LFO) and a ferroelectric perovskite BiFeO₃ (BFO) is presented. It is observed that lithium (Li)‐doping in BFO favors the formation of LFO spinel as a secondary phase during the synthesis of Li_xBi_1?xFeO₃ ceramics. Multimodal functional and chemical imaging methods are used to map the relationship between doping‐induced phase separation and local ferroic properties in both the BFO‐LFO composite ceramics and self‐assembled nanocomposite thin films. The energetics of phase separation in Li doped BFO and the formation of BFO‐LFO composites are supported by first principles calculations. These findings shed light on Li's role in the formation of a functionally important room temperature multiferroic and open a new approach in the synthesis of light element doped nanocomposites for future energy, sensing, and memory applications.     

Ferroelectric Poling of Methylammonium Lead Iodide Thin Films

Seemingly contradictory reports on polar domains and their origin have surrounded the controversial discussion about the ferroelectricity of the methyl ammonium lead iodide (MAPbI₃) thin films that are commonly employed in perovskite solar cells. In this work, microscopic modulations of the polar domain patterns upon application of an electric poling field are correlated with macroscopic changes to the currents through the MAPbI₃ layer. Piezoresponse force microscopy is used to monitor the widening, narrowing, generation or extinction of polar domains, as well as shifts of the domain walls at room temperature under an in‐plane electric poling field that is applied between two laterally organized electrodes. This poling leads to a net polarization of individual grains and the thin film itself. Macroscopically, this net polarization results in a persistent shift of the diode characteristics that is measured across the channel between the electrodes. Both the modulation of the polar domains upon electric poling and the concurrent persistent shift of the electric currents through the device are the unambiguous hallmarks of ferroelectricity, which demonstrate that MAPbI₃ is a ferroelectric semiconductor.     

Images of a First‐Order Spin‐Reorientation Phase Transition in a Metallic Kagome Ferromagnet

First‐order phase transitions, where one phase replaces another by virtue of a simple crossing of free energies, are best known between solids, liquids, and vapors, but they also occur in a wide range of other contexts, including even elemental magnets. The key challenges are to establish whether a phase transition is indeed first order, and then to determine how the new phase emerges because this will determine thermodynamic and electronic properties. Here it is shown that both challenges are met for the spin reorientation transition in the topological metallic ferromagnet Fe₃Sn₂. The magnetometry and variable temperature magnetic force microscopy experiments reveal that, analogous to the liquid–gas transition in the temperature–pressure plane, this transition is centered on a first‐order line terminating in a critical end point in the field‐temperature plane. The nucleation and growth associated with the transition is directly imaged, indicating that the new phase emerges at the most convoluted magnetic domain walls for the high temperature phase and then moves to self‐organize at the domain centers of the high temperature phase. The dense domain patterns and phase coexistence imply a complex inhomogenous electronic structure, which can yield anomalous contributions to the electrical conductivity.     

Ta2O5-TiO2调制结构和介电性能相关性

本文略述了近来用高分辨电子显微术及其模拟技术,解析Ta2O5和(Ta2O5)1-x(TiO2)x的晶体结构的进展,并揭示了(Ta2O5)1-x(TiO2)x固溶体中由于Ti离子有序占据八面体位置所形成的调制结构和介电性能之间的关联.     

基于频域分析的光学相干显微镜中的色散补偿

提出基于频域分析的色散补偿方法,对光学相干显微镜的干涉信号进行快速傅里叶变换,得到频率幅值极大值对应的平均波数,将提取的解包裹后的相位以平均波数为中心做多项式拟合,得到二阶色散系数。实验中,通过在参考臂中插入不同厚度的色散介质来引入两个干涉臂色散介质的光程差,并求得相应的二阶色散系数。通过最小二乘线性拟合,证实了二阶色散系数和色散介质的相对厚度具有很好的线性关系。根据该线性关系,可以在参考臂中插入适当厚度的色散介质来完全补偿干涉系统的二阶色散。     

改进缺陷,套刻和聚焦性能的第五世代浸没式曝光系统

论述了第五世代双扫描平台浸液式扫描曝光机的性能和进展。表明了在高速扫描状态下有生产价值的套刻和聚焦性能的实现。浸液式设备更多的关键部分与缺陷有关,而且该机的改进是通过有生产价值的缺陷水平方面来体现的。为了保持这种缺陷水平的改进效果,需要在圆片应用中进行专门稳定的测量。特加是边缘空泡除去(EBR)设计和圆片斜面良流线性是很重要的。     

Negative giant surface potential of vacuum-evaporated tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)3] film

Negative giant surface potential was realized in a vacuum-evaporated film of tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)₃]. Electroabsorption response of the film presented an inverted polarity to that of tris(8-hydroxyquinolinolato) aluminum (Alq₃), suggesting opposite noncentrosymmetry of molecular orientation. Asymmetric dice model with molecular geometric effect has been proposed, and propyl substitution at 7 position of the ligands was indicated to affects the molecular posture on the surface to invert the polarity of noncentrosymmetry. Our results opened a new possibility of controlling molecular orientation in a film for device applications.     

中枢神经细胞瘤的超微结构观察

应用光镜检查及免疫标记,对2例中枢神经细胞瘤进行电镜观察.结果显示,中枢神经细胞瘤在电镜下具有一定的结构特征：瘤细胞间可查见桥粒样结构;胞质内有神经分泌颗粒和哑铃状致密核心颗粒;胞突内有丰富的微管和囊泡状结构.在外科病理诊断中,中枢神经细胞瘤难以与少突胶质细胞瘤、透明细胞室管膜瘤等肿瘤鉴别.电镜检查对鉴别诊断有比较重要的意义.肿瘤细胞胞突内的微管和囊泡、胞质内的神经内分泌颗粒等超微结构与免疫组织化学标记一致,同时也提示肿瘤起源于神经元细胞.     

Microdroplet and Atomic Force Microscopy Probe Assisted Formation of Acidic Thin Layers for Silicon Nanostructuring

In this work, an aqueous acidic thin‐layer‐based strategy for fabricating nanostructures on silicon by using atomic force microscopy (AFM) nanolithography is presented. The approach involves the formation of microscale droplets via dilute hydrofluoride (DHF) etching, the conversion of the droplets to acidic thin layers by AFM‐probe scanning, and subsequent lithographic operations using a biased probe in the aqueous layers. By varying the concentration of the acidic DHF layers, the thin layers can facilitate the creation of both positive and negative patterns, such as oxide dots and Si pores, through anodic oxidation and dissolution. In particular, the anodic oxidation in the acidic media is associated with the field‐enhanced nonequilibrium dissociation of the weak electrolyte. The Si pore structure formation is related to the field‐assisted dissolution of anodic oxides and the Si substrate. The acidic‐layer‐based technique allows switching between different lithographic modes by changing the acidity of the DHF layers, and is complementary to bulk solution‐based and local meniscus‐based approaches in AFM nanolithography. In principle, this method can also be extended to other materials that have similar reactions with DHF.