CBE30361 Lecture Notes - Lecture 7: Carbon Nanotube, Tetragonal Crystal System, Cubic Crystal System
8 Feb 2016
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Polymers tend to be the lightest of the three. Composites also tend to be lighter (but depends on the composite) In general, (cid:2025)(cid:3040)(cid:3032)(cid:3047)(cid:3028)(cid:3039)(cid:3046) < (cid:2025)(cid:3030)(cid:3032)(cid:3045)(cid:3028)(cid:3040)(cid:3036)(cid:3030)(cid:3046) < (cid:2025)(cid:3043)(cid:3042)(cid:3039)(cid:3052)(cid:3040)(cid:3032)(cid:3045)(cid:3046) Difficult to make (and very expensive), but extremely strong. A collection of many small crystals or grains. Each grain is a single crystal (size of 1nm to 2cm) Properties of crystalline materials often related to crystal structure. Example: the modulus of elasticity ( e ) in bcc iron: Properties may or may not vary with direction: In bulk, the random orientations cause the material to be uniform But not nearly as anisotropic as a single crystal. Some materials may exist in more than one crystal structure, this is called polymorphism. If the material is an elemental solid, it is called allotropy. The origin has been arbitrarily selected as the bottom left-back corner of the unit cell. Point: q, r, s q-the distance qa along the x axis.
