查看更多>>摘要：We developed high temperature in situ transmission electron microscopy using a high-density laser irradiation device (nominal maximum laser density ~9.4 GW/m(2)) and a corresponding heat shielding sample mount device. The spatial line resolution of the microscope was maintained to be 0.14 nm at ambient temperatures after the installation of the laser irradiation device. The system was applied to the investigation of high temperature structural variation in tungsten plates. When the laser power was increased up to irradiation densities of approximately 61-280 MW/m(2) (laser source output: 130-590 mW) to degrade tungsten plates, the microscope was undamaged. The surface dynamics was observed in situ by lattice imaging at irradiation densities of approximately 61-75 MW/m(2) (laser source output: 130-160 mW); the spatial line resolution of the microscope was maintained to be 0.23 nm at high temperatures. It was expected that high temperature observation is realized using this heating system, which can be applied to the investigation of various advanced heat-resistant materials. We found using this heating system that degradation in tungsten plates started from surfaces and progressed through the preferential generation of characteristic defects, such as atomistic and nanometer holes and rods, and their subsequent evolution in thinner regions during the heating. It was demonstrated that the holes and rod were truncated with {110} sidewalls, i.e., these surfaces were stable in tungsten at high temperatures.
查看更多>>摘要：In this study, ZrMgMo3O12/Al-40Si (ZMMO/Al-40Si) composites with 15 wt% ZrMgMo3O12 were fabricated by ball milling-vacuum hot pressing (VHP) processes. The effect of ball milling processes on the microstructure, compressive properties and coefficient of thermal expansion (CTE) of the composites were investigated. It is found that ball milling treatments of mixed ZMMO/Al-40Si powders refine the particles of ZMMO reinforcements and primary Si in ZMMO/Al-40Si composites and improve the distribution of ZMMO reinforcements in alpha-Al matrix, resulting in the increase of the compressive strength and the decrease of the CTE of ZMMO/Al-40Si composites. The highest compressive yield strength of 430.82 MPa and the lowest CTEs of 5.8 x 10(-6)/C (RT - 400 ?C) are obtained after ball milling for 8 h at 250 rpm, increasing by 145.9% and decreasing by 61.3% respectively compared with the compressive yield strength and CTE of Al-40Si alloy. Among the reinforcements commonly used in aluminum matrix composites, ZMMO reinforcement has the highest reduction efficiency for CTE of ZMMO/Al-40Si composite. The application of high-energy ball milling to refine the microstructure is a promising method that can simultaneously increase the strength and reduce the CTEs of ZMMO/Al-40Si composites.
查看更多>>摘要：Measuring residual aberrations up to second order using a crystalline specimen in transmission electron microscope is challenging. Here, we show by good examples of both experimental and simulated images that it is feasible to measure aberrations up to the second-order, using minimum amplitude contrast criterion for the exit wave function reconstructed. We propose a two-steps strategy for the task: (i) Firstly measuring defocus and twofold astigmatism simultaneously to avoid error accumulation and to reduce the number of dimensions in parameters space. (ii) Then, with minimized misleading effects (or errors) in defocus and two-fold astigmatism, estimations of three-fold astigmatism and coma can be conducted more efficiently and effectively. Influences of other factors such as specimen structure, resolution and specimen thickness on the validity of the method are also discussed in detail. Our study provides a practical procedure for correcting residual aberrations in image wave using crystalline materials, which can then facilitate application of exit wave reconstruction technique to materials research.
查看更多>>摘要：This article addresses a deficit in the cell biology and hematology literature, specifically regarding Antoni van Leeuwenhoek's central role in observing and describing red blood cells and hemocytes. While the existing literature on the history of hematology usually mentions Antoni van Leeuwenhoek, typically, it is an incomplete summary of his contributions. Leeuwenhoek is cited as one of the three individuals who first saw and described red blood cells through their microscope lenses. Jan Swammerdam and Marcello Malpighi also documented red blood cells in human blood before Leeuwenhoek. The literature fails to mention that Leeuwenhoek commented on red blood "globules," as well as arthropod hemocytes, at least thirty-five times in thirty-one letters spanning thirty-nine years of correspondence to The Royal Society and others. Some of his descriptive passages were extensive. His observations on blood circulation are a separate set of observations in his letters and are not covered here. Leeuwenhoek viewed various creatures to see if there were characteristics to their blood cells that he could share with the recipients of his letters. He also would view the cells in different chemical and physical environments to understand their properties. Leeuwenhoek's observations of blood corpuscles are discussed in chronological order. Comments included in footnotes by the Committee of Dutch Scientists, who edited the published seventeen volumes of Leeuwenhoek's Alle de Brieven, are also discussed when their comments are relevant.
查看更多>>摘要：Precision elemental analysis by EELS at a nano-meter scale is a desirable goal for industrial application, as well as basic scientific research on advanced material analysis. However, sample thickness variation leads to a systematic error in element quantification due to electron plural scattering events and prevents it to be a useful quantitative analytic method. In this paper, we compared three methods to minimize thickness effect: Fourier-log deconvolution, Jump ratio, and Si K-edge by quantifying the N/Si ratio versus different thickness on a standard Si3N4 crystal sample. The results indicated that Jump ratio method exceeded other two methods owing to its higher accuracy, short data acquisition time as well as minimum requirement for spectroscopy instrument. The jump ratio method was applied to calculate N/Si ratio in storage nitride layer of 3D NAND trench wafer and blanket wafer, both illustrated that the jump ratio method successfully corrected the thickness effect on EELS composition quantification and largely reduced the relative error compared with the non-corrected result.
NSTL
Elsevier