Silicates And Silicon Carbide

Silicates and Silicon Carbide

Silicates

Since Silicon and Oxygen are the most abundant elements, the silicate minerals are the most common. Silicate minerals form the largest fraction of most crustal rocks and, therefore, receive considerable attention from geologists and mineralogists. With oxygen and silicon comprising approximately 85% of the atoms in Earth’s crust, most minerals in the crust include these two elements, and form the class of minerals called silicates. Nearly all of the silicates have structures based on the [SiO4 ]-4 tetrahedron. Each oxygen atom in a [SiO4 ] –4 tetrahedron has only half of its -2 charge satisfied by the Si-O bond (bond strength = 1) and so must be bonded to other cations. If an oxygen is bonded to two Si atoms, the coordination polyhedra of oxygens around those two Si atoms will share corners and the oxygen in common will have its charge fully balanced by the two Si-O bonds. The fact that [SiO4 ]-4 tetrahedra can share corners and fully balance oxygen charges locally makes a great number of silicate structures possible.

Silicon Carbide

Silicon carbide is a black to green material that is a combination of 70% silicon and 30% carbon. Silicon carbide is an important non-oxide ceramic which has diverse industrial applications. In fact, it has exclusive properties such as high hardness and strength, chemical and thermal stability, high melting point, oxidation resistance, high erosion resistance, etc. In nature, only a small amount exists, where coal and sand have been exposed to each other in the presence of a significant amount of heat. No commercially viable deposits exist, so for practical use, the material is manufactured. All of these qualities make SiC a perfect candidate for high power, high temperature electronic devices as well as abrasion and cutting applications. Quite a lot of works were reported on SiC synthesis since the manufacturing process initiated by Acheson in 1892.


Practise This Question

Which of the following functions is NOT attributed to non-genetic RNA?