Other Hexagonal Ring Structures

Bk ring structure of a-boron nitride. Unlike graphite, the layers sit on top of each other are bonded together by a combination of ionic and covalent bonds to make a very strong and inert structure. 

Layered C7 structure of M02S. The layers consist of S atoms (light spheres) on either side of the Mo atoms (grey spheres) in an hep arrangement. Since all bonds are satisfied, the layers slip over each other, attracted only by van der Walls forces. 

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Although it does not relate to polytype identification, we mention a 14N static and MAS-NMR study of WZ AIN, which revealed a fortuitously small Cq < 10 kHz [167]. For comparison, the 27A1 Cq in the same compound was measured to be 1.913 MHz, and had an unusual positive temperature coefficient that has been seen for other metal nuclei in WZ structures. The 14N MAS-NMR spectrum of BN yielded a Cq of 142 kHz corresponding to an axially-symmetric tensor in the hexagonal ring structure [167]. 

Carbon blacks are synthetic materials which essentially contain carbon as the main element. The structure of carbon black is similar to graphite (hexagonal rings of carbon forming large sheets), but its structure is tridimensional and less ordered. The layers of carbon blacks are parallel to each other but not arranged in order, usually forming concentric inner layers (turbostratic structure). Some typical properties are density 1.7-1.9 g/cm pH of water suspension 2-8 primary particle size 14-250 nm oil absorption 50-300 g/100 g specific surface area 7-560 m /g. 

The benzene molecule is a remarkable structure with six carbons in a hexagonal ring. To satisfy the carbon valence of four, every other carbon-to-... 

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