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用X射线形貌术及光学双折射形貌术对天然绿柱石晶体中的生长区界面进行了研究. 观测发现, 同类生长区的界面在两种形貌中通常不出现可见的衬度; 异类生长区界面中, t-s 界面在x 射线形貌中呈现动力学千涉条纹衬度, 表明它们具有平移型界面的特征, 根据消光规律知其相应的位移矢量很可能与界面垂直; 在双折射形貌中, 异类生长区界面衬度的出现与界面两侧存在不同的长程应变场有关. 实践表明, 两种形貌术互相补充, 互相参证, 在生长区界面的研究中是十分有效.
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一、引 言 大量事实表明,X射线形貌技术对大块近完整晶体内各种类型缺陷的观察是一种很好的方法[1].铁磁、铁电畴和畴壁作为一种形式的面缺陷,其形貌观察的结果同样显示了该方法有着许多独特的优点.早在1960年K.Mexz用X射线反射形貌方法首次成功地显示了铁磁体内畴的一些组态.后来人们又在许多铁磁材料中作过畴的X射线形貌观察,特别是对Fe,Fe-Si中畴的观察结果大大丰富了有关磁畴及畴壁结构和它们在形貌衬度理论方面的研究[2,3].许多反铁磁材料(如 NiO,Cr等)的X射线形貌研究工作也是令人鼓舞的.作为形貌技术对磁畴研究的某些进展似乎表… 相似文献
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同轴X射线相位衬度计算机X射线断层摄影术研究 总被引:2,自引:2,他引:0
基于北京同步辐射装置(BSRF)开展了同轴X射线相位衬度计算机X射线断层摄影术(CT)研究.利用北京同步辐射的14 keV单色X射线作为光源,以高分辨能力的X射线胶片作为探测器,分别开展吸收衬度和同轴相位衬度成像的比较研究以及相位衬度计算机X射线断层摄影术研究.相位衬度计算机X射线断层摄影术重建采用Bronnikov提出的算法.结果显示,与传统的吸收衬度图像相比,相位衬度图像具有更好的衬度和更高的空间分辨力;实验获得人工样品和蝗虫的相位衬度计算机X射线断层摄影术重建图像.重建图像中可见样品的一些结构细节.实验结果表明,相位衬度X射线成像更适合于研究弱吸收或吸收差异很小的材料;利用北京同步辐射开展同轴X射线相位衬度计算机X射线断层摄影术研究是可行的. 相似文献
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晶体缺陷对晶体的许多性能有重要影响,因此研究单晶缺陷的数量、分布、性质及其与晶体性能的关系,对有目的地改进晶体质量有较大的意义。在观测晶体缺陷的方法中较常用的是扫描透射形貌术[1],然而反射形貌术装置简单,摄照时间较短,有许多优点。特别是有两种情况需要用到反射形貌术:其一是研究半导体外延层和分光晶体表面层的晶体缺陷。在这些晶体中,表面层起重要作用。由于反射法X射线穿透深度较小,一般为几微米,故能在形貌图中出现晶体表面薄层的形貌而不反映厚晶体内部状况;另一种情形是当晶体吸收很大,制备符合透射形貌术要求的薄晶体很… 相似文献
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用X射线衍射截面形貌术研究了金刚石晶体中Pendellosung条纹的消衰(fading)现象。实验表明,在尖劈形晶体和平板状晶体以及包含一片层错的晶体中都观察到动力学衍衬干涉条纹的消衰现象。用动力学理论和实验结果进行定量的比较,结果是一致的。
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Dislocation images in X-ray topography of protein crystals such as tetragonal hen egg-white lysozyme crystals were analyzed. Not only extinction but also double contrast of dislocation images are clearly observed on the X-ray topographs. It should be noted that the observed image widths of the dislocation contrasts are much less than those calculated on the basis of the kinematical theory in X-ray topography, which has been successfully applied for inorganic crystals and organic crystals of small molecules so far. Moreover, in tetragonal HEW lysozyme crystals, the rocking curve widths of the perfect crystal related to the kinematical theory are less than the measured ones by two orders of magnitude. This discrepancy is consistent with that in the image width of the dislocation contrast. From this correlation, it is suggested that the larger rocking curve width, or higher mosaicity, is mainly responsible for the observed image width in the grown crystals. 相似文献
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本文叙述邻苯二甲酸氢钾(KAP)晶体内部不完整性(滑移位错等)的同步辐射截面形貌图的衬度研究工作。有关缺陷象衬度随波长增加而提高的实验事实同引用均匀畸变动力学的理论所引入的平均应变梯度参数β和βteff的理论计算结果,相当符合,它为应用同步辐射源来清晰显示单晶中有关缺陷,提供一个波长选择的依据。
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B.K. Tanner M. Safa D. Midgley J. Bordas 《Journal of magnetism and magnetic materials》1976,1(4):337-341
Antiferromagnetic domain wall movements in KNiF3 have been observed directly by X-ray topography using synchrotron radiation. Topographs were taken in fields up to 1.3 T at a temperature of 77 K. In contrast to X-ray topography using conventional sources, the apparatus is simple and it is possible to obtain good resolution topographs despite the geometrical limitations imposed by the cryostat and electromagnet. Exposure times were typically 8 seconds when recording on Ilford L4 Nuclear Emulsion plates. 相似文献
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U. Bonse 《Zeitschrift für Physik A Hadrons and Nuclei》1964,177(5):543-561
The causes of contrast at dislocations on X-ray topographs taken with different techniques are discussed. It is shown that a variety of mechanisms may be important for the image formation and the type of contrast observed. Particular attention is paid to the role which the deflection of wavefield rays in the long reaching strainfield of a dislocation may play in the formation of the dislocation image. For the case of dislocations imaged by the double crystal method paths of wavefield rays have been calculated numerically. Since in this case Braggcase wavefields are involved, the general theory of wavefield propagation in a weakly deformed lattice24 had to be used. The results confirm the assumption that deflection of wavefield rays can contribute considerably to dislocation images obtained in X-ray topography. 相似文献
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As a strange property not explained by existing theories, it has been known from experiment that X‐ray moiré and Pendellösung interference fringes show a small spatial oscillation in the beam path in free space that the diffraction image carrying those fringes is propagated after emerging from the crystal. In connection with the investigation into this strange fringe oscillation, it has been found, by an experiment successively recording Pendellösung‐fringe topographs using an X‐ray CCD camera, that X‐ray Pendellösung fringes also show a small temporal oscillation. Characteristics of this temporal Pendellösung‐fringe oscillation, namely irregularities in the fringe profile, the manner of fringe oscillation and a reciprocal correlation between oscillation amplitude and fringe contrast, are shown to be very similar to those of the previously reported spatial oscillation of moiré and Pendellösung fringes. Therefore this temporal oscillation is supposed to have the same origin as the spatial oscillation, revealing another section of the same phenomenon. This discovery of the temporal oscillation advances a step nearer to the full understanding of this strange phenomenon, while disclosing a new property of Pendellösung fringes. As well as the above, a three‐dimensional profile representation (surface plot) is given of the image of Pendellösung fringes, to make it clear that unidentified fine intensity modulations, called subfringes in this paper, are produced superposed on the main fringe system. Overall inspection of the intensity profiles of the fringe‐imaged topographs suggests that temporal intensity oscillations also occur on a more global scale than the extension of individual fringes, as an unidentified action of the wavefield. 相似文献
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A. A. Shiryaev E. Kh. Mukhamedzhanov A. E. Voloshin A. N. Morkovin M. M. Borisov S. V. Titkov 《JETP Letters》2008,88(10):670-673
The X-ray topographs of diamond crystals of different perfection degrees have been obtained using the quasiforbidden 222 reflection. It has been shown that the use of such reflections in X-ray topography makes it possible to study the distribution of the defects affecting the electron density distribution over the crystal cross section. 相似文献
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