Ni(fcc)vs NigAl (L12) 200 220 E 利刹西裤 -插250黄 000 020 51/nm B=[001] 200 19440 220 311 60 70 20 6
6 2 (111) (200) (220) (311) Ni (fcc) vs Ni3Al (L12 )
Selected area diffraction (SAD) D 900C/100h 900C/100h B2+O um Ti-23Al-22Nb,a2/B2+O phase 7 Intermetallics 9(2001)1045-1052
Selected area diffraction (SAD) 7 Ti-23Al-22Nb, 2 /B2+O phase Intermetallics 9 (2001) 1045–1052
Selected area diffraction (SAD) Selected area By placing a small aperture Specimen at the image plane,only electrons from the projected aperture at the sample contribute to diffraction Objective lens pattern. Conjugate plane Back focal plane__ Minimum selected area ~0.5 um diameter,which is limited by lens aberrations Image plane SAD aperture 8
Selected area diffraction (SAD) 8 By placing a small aperture at the image plane, only electrons from the projected aperture at the sample contribute to diffraction pattern. Minimum selected area ~0.5 m diameter, which is limited by lens aberrations Conjugate plane Image plane Objective lens Back focal plane Specimen SAD aperture Selected area
Selected area diffraction (SAD) (c) 900C/100h Ti-23Al-22Nb,a2/B2+O phase 9 Intermetallics 9(2001)1045-1052
Selected area diffraction (SAD) 9 Ti-23Al-22Nb, 2 /B2+O phase Intermetallics 9 (2001) 1045–1052
Formation of a diffraction pattern in TEM λL Electron beam Rd=λL,R= d poly-Al specimen Incident Objective lens (hkl) Back-focal plane Specimen Projection lens 20 Ewald sphere Camera g (1八>g) length (L) pattern R R Screen L:15~120 cm in practice 10 p.108 in the textbook p.114 in the textbook
Formation of a diffraction pattern in TEM poly-Al specimen R 𝑅𝑑 = 𝜆𝐿, 𝑅 = 𝜆𝐿 𝑑 L: 15~120 cm in practice 10 pattern Objective lens Projection lens Screen Back-focal plane Electron beam p.108 in the textbook R p.114 in the textbook