Periodic surfaces close-packed spheres

The surface of a crystalline solid is strongly correlated to its bulk structure. The atoms of a crystal are arranged in a periodical sequence forming the crystal lattice. Most frequently metals and metal alloys tend to form close-packed sphere (cps) arrangements reflecting the isotropy of the forces of atomic interaction. 

The new mesoporous materials have extremely high surface-to-volume ratios. An example of these materials is MCM41, which was invented by DuPont. A simple structure that can be manufactured in the laboratory is illustrated in Eigure 15.14. The structure initially contained a periodic array of polymer spheres. When close packed, these spheres leave 26% of the volume empty. We can then infiltrate a liquid into these pores, burn out the spheres, and convert the liquid to a polycrystalline ceramic. Another synthesized porous ceramic is the cordierite honeycomb structure used to support the Pt catalyst in automobile catalytic converters. In this case the cylindrical pores are introduced mechanically in the extrusion process. 

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