基于单幅扫描电镜图像的三维重建技术

本文提出了一种对黑硅表面进行三维重建的方法．通过对扫描电子显微镜的成像原理进行建模,该方法可以只使用单幅从黑硅表面正上方垂直向下拍摄的扫描电子显微镜图像获得黑硅表面的三维信息．该方法简单易行．本文对这一方法进行了重建测试．测试结果表明该方法能够获得比较理想的重建效果．     

Synthesis and electrochemical performance of LiV3O8/carbon nanosheet composite as cathode material for lithium-ion batteries

To improve the rate capability and cyclability of LiV₃O₈ cathode for Li-ion batteries, LiV₃O₈ was modified by forming LiV₃O₈/carbon nanosheet composite. The LiV₃O₈/carbon nanosheet composite was successfully achieved via a hydrothermal route followed by a carbon coating process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). TEM observations demonstrated that LiV₃O₈/carbon composite has a very flat sheet-like morphology, with each nanosheet having a smooth surface and a typical length of 400-700 nm, width of 200-350 nm, and thickness of 10-50 nm. Each sheet was surrounded by a thick layer of amorphous carbon. Electrochemical tests showed that the LiV₃O₈/carbon composite cathode features long-term cycling stability (194 mAh g⁻¹ at 0.2 C after 100 cycles) and excellent rate capability (110 mAh g⁻¹ at 5 C, 104 mAh g⁻¹ at 10 C, and 82 mAh g⁻¹ at 20 C after 250 cycles). Electrochemical impedance spectra (EIS) indicated that the LiV₃O₈/carbon composite electrode has very low charge-transfer resistance compared with pristine LiV₃O₈, indicating the enhanced ionic conductivity of the LiV₃O₈/carbon composite. The enhanced cycling stability is attributed to the fact that the LiV₃O₈/carbon composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact.     

Observation of crack microstructure in oxides and its correlation to oxidation and hydrogen-uptake by 3D FIB Tomography – case of Zr-ZrO2 in reactor

Abstract

Zirconium based alloys are used as fuel claddings in Light Water Reactors due to their good resistance to degradation and low neutron absorption cross section. However, life limiting processes occur during the service of the cladding such as oxidation and hydrogen-uptake. During the oxidation of the material, hydrogen enters the metal and it precipitates as brittle hydrides. In this study the 3D microstructure of a high burn-up and a low-burnup LK3/L Zircaloy-2 cladding is characterized and compared using FIB Tomography. 3D reconstruction of the oxides of the claddings shows that the crack volume fraction increases with the number of cycles in the reactor, reducing its protectiveness against further corrosion and H-uptake. The visualization of the metal-oxide interface revealed that the oxidation of the hydrides in the metal could induce crack formation in the oxide and therefore it could be one of the causes of the increasing oxidation and H-uptake in this material.     

机器人辅助无框架定位脑外科手术系统

研制了机器人辅助无框架定位脑外科手术系统,该系统可以在CT和MRI图像上实施病灶以及头颅的半自动分割,并将分割结果重构为三维模型,此模型可以进一步应用于虚拟手术规划及手术实施。它提供的三维组织模型清晰准确,手术路径精确稳定,从而提高了手术的效率和质量,降低了手术的费用。该系统在多例临床手术中获得了良好的效果。     

基于图像处理的外螺纹三维模型重构

提出了一种基于多角度序列图像特征实现外螺纹的三维模型重建的方法。首先在旋转平台上采集多角度序列螺纹件图像,然后对每帧图像进行特征点提取,将序列图像的特征点进行三维变换和插值,最终生成三维模型。实验结果表明,此算法能精确高精度地实现外螺纹三维模型重构。     

三维成像声呐图像重建研究

针对成像声呐领域中水下目标探测、识别等问题,基于三维探测声呐2304通道波束形成数据,研究三维成像声呐可视化方法,仿真了三维点云重构算法,并根据实际应用需求,在设备实现中改进了算法,使其在实际环境中可动态调节阈值,优化成像效果。水池、湖试实验表明:以该可视化方法为基础的三维探测声呐可正确显示目标位置、形态;且在混响环境中对复杂探测目标有良好的重构效果;同时通过与二维声呐图像对比,进一步验证了该三维声呐在轮廓识别方面的优越性。     

PEEK composites reinforced with zirconia nanofiller

The present investigation deals with the preparation and characterization of nanocomposites of polyether ether ketone (PEEK) containing nanosized zirconia filler up to 3 wt.% loading. It has been observed that presence of zirconia filler dispersed in polymer matrix enhances various basic and functional properties (e.g., mechanical properties, thermal stability & other physico-mechanical properties). The SEM studies reveal that the dispersion of zirconia nanofiller is uniform throughout the polymer matrix. The thermal stability of the nanocomposites has been studied by TGA. Thermal analysis of the composites shows an increase in the thermal stability with increase of nanofiller content. This may be attributed to strong interaction between polymer chains and filler particles. DMA studies show the significant improvement in storage modulus of the nanocomposites because of better interaction of zirconia particles in PEEK matrix.     

Three dimensional imaging of deformation modes in TiN-based thin film coatings

A TiN thin film coating, approximately 4 μm in thickness, deposited on a ductile steel substrate, was subject to surface deformation via nanoindentation using a spherical indenter, 5 μm in radius, with loads up to 500 mN. Pop-ins were observed during loading, which are characteristic of the onset of cracking and the formation of shear steps at the coating-substrate interface. Focused ion beam microscopy was used to prepare cross-sections through the indentation that revealed the presence of both intercolumnar and inclined cracks. Three-dimensional reconstructions of the deformation zone beneath the indentation were performed using a dual-beam focus ion beam instrument. These constructions provided more detailed images of the morphology of cracks, which were observed to be consistent with theoretical models of plastic deformation of such brittle coatings.     

Electron microscopic tomography: A tool for probing the structure and function of subcellular components

Tomography is a powerful tool for obtaining three-dimensional information from transmission electron microscopy, but its application faces unique challenges. A single-axis tilt geometry for data collection results in anisotropic resolution because full angular coverage is not feasible for most specimen preparations. This effect can be minimized by combining two single-axis tilt series that have been collected orthogonal to each other. Rapid freezing has been successfully used to preserve the native structure of biological specimens in a form that can be visualized in the high-vacuum environment required for electron microscopy; however, these preparations are extremely labile to electron exposure. As a result, application of tomography to frozen-hydrated specimens has only recently become feasible with the development of automatic data collection, and with a renewed appreciation for the principle of dose fractionation. Even with the limitations of traditional specimen preparations and conventional methods of data collection, electron microscopic tomography has been successfully employed to probe the structure and function of several important cellular components. Current efforts include combining electron microscopic tomography and video-enhanced light microscopy to correlate ultrastructural variation with the direction of chromosome motion during mitosis. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 175–187, 1997     

Fast computation for generating CGH of a 3D object by employing connections between layers

An approximate method for generating computer-generated holograms (CGH) of a 3D object with six times faster speed than the conventional algorithm is presented. In the conventional algorithm, a 3D object is sliced into many layers and treated as a collection of self-illuminated point light source. The propagation process of a light ray from every point of an object to all the points on the hologram plane is simulated and interfered with by the reference beam to form a CGH. In our proposed method, under the assumption that the depth of a 3D object is much smaller than the recording distance, we just need to calculate the oblique distance between the first layer and the hologram plane, and then the oblique distances from the other layers to the hologram plane can be obtained from a simple relation, thus the computational time is much reduced. The CGH is optically reconstructed and the quality of the reconstructed image agrees well with that from the conventional algorithm.     

Carbon nanotube (CNT)-based composites as electrode material for rechargeable Li-ion batteries: A review

The ever-increasing demands for higher energy density and higher power capacity of Li-ion secondary batteries have led to search for electrode materials whose capacities and performance are better than those available today. Carbon nanotubes (CNTs), because of their unique 1D tubular structure, high electrical and thermal conductivities and extremely large surface area, have been considered as ideal additive materials to improve the electrochemical characteristics of both the anode and cathode of Li-ion batteries with much enhanced energy conversion and storage capacities. Recent development of electrode materials for LIBs has been driven mainly by hybrid nanostructures consisting of Li storage compounds and CNTs. In this paper, recent advances are reviewed of the use of CNTs and the methodologies developed to synthesize CNT-based composites for electrode materials. The physical, transport and electrochemical behaviors of the electrodes made from composites containing CNTs are discussed. The electrochemical performance of LIBs affected by the presence of CNTs in terms of energy and power densities, rate capacity, cyclic life and safety are highlighted in comparison with those without or containing other types of carbonaceous materials. The challenges that remain in using CNTs and CNT-based composites, as well as the prospects for exploiting them in the future are discussed.     

高性能聚焦离子束技术的应用

叙述了采用液态镓作为离子源的高性能聚焦离子束系统(FIB)在材料科学研究领域中的作用。该系统有三大用途：形貌观察；分辨率高达5nm；微刻蚀以及微沉淀。详细地介绍了利用FIB进行形貌观察、制备TEM样品和表面刻蚀的过程及实验结果。     

On the transition from shear-driven fibre compressive failure to fibre kinking in notched CFRP laminates under longitudinal compression

This paper investigates longitudinal compressive failure in notched unidirectional and cross-ply carbon/epoxy specimens. Dedicated test jigs were developed to observe the failure processes at the microscale. In situ and post-mortem fractography reveals two types of failure mechanisms: (i) shear-driven fibre compressive failure and (ii) kink-band formation. The sequence of events leading to failure and the reasons for shear-driven fibre compressive failure or kink-band formation are investigated and discussed. Those findings are discussed further in a separate paper (Gutkin et al., accepted for publication) [1] where an FE micromechanical model is used to investigate numerically the failure mechanisms found in longitudinal compression.     

扫描电镜纳米尺度测量的标准化研究

本文简要介绍了纳米尺度测量概况和扫描电镜在纳米测量中的主要应用,从扫描电镜测长用标准物质,扫描电镜计量检定规程和长度测量标准方法3个方面简述了纳米尺度测量方法的标准化概况及国内外研究现状,并对纳米尺度测量未来的发展做出了展望。     

Enhanced field emission characteristics of nitrogen-doped carbon nanotube films grown by microwave plasma enhanced chemical vapor deposition process

Nitrogen-doped carbon nanotube (CNT) films have been synthesized by simple microwave plasma enhanced chemical vapor deposition technique. The morphology and structures were investigated by scanning electron microscopy and high resolution transmission electron microscopy. Morphology of the films was found to be greatly affected by the nature of the substrates. Vertically aligned CNTs were observed on mirror polished Si substrates. On the other hand, randomly oriented flower like morphology of CNTs was found on mechanically polished ones. All the CNTs were found to have bamboo structure with very sharp tips. These films showed very good field emission characteristics with threshold field in the range of 2.65-3.55 V/μm. CNT film with flower like morphology showed lower threshold field as compared to vertically aligned structures. Open graphite edges on the side surface of the bamboo-shaped CNT are suggested to enhance the field emission characteristics which may act as additional emission sites.     

有关电子显微技术的几个实验和建议

本文涉及两个和电子显微技术有关的问题：豆．透射电子显微镜试样薄片表面沉淀相颗粒存在状况的实验观察．２．扫描电子显微镜背反射电子象用作定量金相测定的建议。