32.9 Some Add itional Terminology in Crystal lography 1. Single crystal ver sus polycrystal 1. For single crystals there is only one type of structure with same orientation Single crystals is characterized by anisotropy ov Wl same structure but different orientations. These smal Polycrystal consists of a lot of grain, small single crystals, single crystals are called grains. The boundaries between them are called grain boundaries
§2.9 Some Additional Terminology in Crystallography ◆ Ⅰ. Single crystal versus polycrystal 1. For single crystals there is only one type of structure with same orientation. Single crystals is characterized by anisotropy. 2. Polycrystal consists of a lot of grain, small single crystals, with same structure but different orientations. These small single crystals are called grains. The boundaries between them are called grain boundaries
grain grain boundary single crystal polycrystal
single crystal polycrystal grain grain boundary
◆‖1. Allotropy Same crystal has different crystallographic structure at different condition EXamples: C, graphite, diamond, CNT 910°C 400°C 1540°C a-Fe r-Fe &-Fe q BCC FCC BCC
◆ Ⅱ. Allotropy Same crystal has different crystallographic structure at different condition. Examples: C , graphite , diamond , CNT Liquid 1540 C Fe 1400 C Fe 910 C Fe − − − BCC FCC BCC
Graphite
➢ Graphite
Ceo molecule
➢ C60 molecule
Carbon Nanotubes 岿卢岿灼 3
➢ Carbon Nanotubes
◆Ⅲ. Atomic radi i d e efinition AB 2
◆ Ⅲ. Atomic radii Definition: 2 SAB r =
Examples and Discussions
Examples and Discussions
Exercise
Exercise
Thank you
Thank you ! 7