tailieunhanh - Volume 10 - Materials Characterization Part 11

Tham khảo tài liệu 'volume 10 - materials characterization part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | structure. The rings beginning with the innermost index as 111 200 220 311 222 and so on. The lattice parameter can be determined from the radii of the diffraction rings. The microscope was operated at 200 keV. Camera constant ĂL A cm. Courtesy of . Hills Spot patterns arise when the incident electron beam irradiates a portion of a single crystal within the specimen. spot pattern is qualitatively analogous to the single-crystal x-ray diffraction patterns obtained using the Laue techr the diffraction from single crystals is discussed further in Ref 2 and 11 . Figure 10 shows a simple spot pattern frc single-crystal region of pure aluminum. The sample has been tilted such that a simple crystallographic direction 10 aligned parallel to the incident beam. This is often referred to as the 100 zone axis. The transmitted spot appears center and the variouhKI reflections appear at specific distances and angles from the transmitted spot. Fig. 10 Spot diffraction pattern from a single crystal of aluminum. The transmitted and diffracted spots are shown. The spots are indexed in the key. The beam direction B is parallel to the zone axis z. Courtesy of . Hills The transmitted spot corresponds to the point at which the transmitted beam intersects the photographic film and diffracted spot corresponds to the point at which a given diffracted beam intersects the photographic film. The cr structure and orientation of the single-crystal region of the specimen being irradiated can be identified from its pattern. These patterns can be indexed anchttli ep Ịane that produced each diffraction spot determined. The pattern i solved using the modified form of Bragg s law rd L wherer is the radial distance from the transmitted spot to the gfotetyi diffracted spot and is the hkl interplanar spacing. The procedure used to solve a diffraction pattern is discussed further in Example 2 in the section Applicat in this article. Simple crystal structures and orientations can often be .