Cork: a strategic material

Abstract

Silicon is in many respects one of the more important elements in both nature and chemistry. On one hand sili- cates constitute the main material of the earths crust, and on the other hand organo silicon compounds are often used in element organic chemistry or as building blocks in material science. This is reflected also in lit- erature concerning silicon NMR. For example, one of the fastest growing sections in the last years comprises the application to material sciences and here especially the solid state silicon NMR. Of the naturally occurring isotopes 28Si (92.21%), 29Si (4.70%) and 30Si (3.09%), 29Si only has a spin 1/2 and therefore a magnetic moment. This puts it in the same league together with the other elements of 14 group of the periodic table of the elements such as carbon, tin and lead. All of these elements, with the exception of germanium, have at least one isotope with a spin of 1/2 (Table 1).