Silicon-Based Polymers and Materials

Jerzy J. Chruściel

• Publisher: De Gruyter
• Year: 2022
• ISBN:
  9783110640137
• Edition: 1
• Topic: Technik & Maschinenbau
• Subtopic: Werkstoffwissenschaft

Silicon based materials and polymers are made of silicon containing polymers, mainly macromolecular siloxanes (silicones). This book covers the different kinds of siliconbased polymers: silicones, silsesquioxanes (POSS), and silicon-based copolymers. Other silicon containig polymers: polycarbosilanes, polysilazanes, siloxane-organic copolymers, silicon derived high-tech ceramics: silicon carbide and oxycarbide, silicon nitride, etc. have also a very important practical meaning and a hudge number of practical applications. These materials make up products in a variety of industries and products, including technical and medical applicatons.

Polycrystalline silicon is the basic material for large scale photovoltaic (PV) applications as solar cells. Technical applications of crystalline (c-Si) and amorphous (a-Si) silicon (fully inorganic materials), silicon nanowires are still quickly growing, especially in the fi eld of microelectronics, optoelectronics, photonics. and photovoltaics, catalysts, and different electronic devices (e.g. sensors, thermoelectric devices).

This book is ideal for researchers and as such covers the industrial perspective of using each class of silicon based materials.

Discusses silanes, silane coupling agents (SCA), silica, silicates, silane modified fillers, silsesquioxanes, silicones, and other silicon polymers and copolymers for practical applications as polymeric materials and very useful ingredients in materials science.

Chapter 1 Introduction

Beginning of chemistry of organosilicon compounds gave the work of F.S. Kiping, in the second half of the nineteenth century. Its stormy development occurred in the 1930s. Major achievements in this field were conducted by K.A. Andrianow, and silicone resins were produced in the former Soviet Union (USSR) on a small scale as early as in 1939. However, only independent development by E. Rochow in the United States (in early 1940s) called “direct synthesis method” of methylchlorosilanes, as starting materials (monomers) for the preparation of silicones, was a breakthrough technology. Almost at the same time the technology of the “direct synthesis” was developed in Germany, under the direction of R. Miller. A production of silicones, the first generation of these unique polymers, began during the Second World War in the United States (in Dow Corning Corporation and General Electric) [1]. Soon after the Second World War, the production of silicones started on a small scale in Europe and Asia (first in Germany, France, Great Britain, USSR, and Japan, and later in other countries such as Czechoslovakia, Poland, and Korea) [2].

Silicon is the major ingredient of sand, silicate minerals, and rocks, which are very stable inorganic materials. Over 90% of the Earth’s crust is composed of the silicate minerals, and silicon is a second most abundant element (after oxygen) in the Earth’s crust (with about 28% content by weight) [3]. A technological pathway from the sand to silicon and its compounds is pretty long. On the industrial scale, a metallurgical-grade silicon was prepared by the reaction of high-purity silica with wood, charcoal, and coal in an electric arc furnace using carbon electrodes. At temperatures over 1,900 °C, silica is reduced by carbon from the aforementioned materials according to the following chemical reaction:

(1.1)$\mathrm{S}\mathrm{i}{\mathrm{O}}_2+2\mathrm{C}\stackrel{}{⟶}\mathrm{S}\mathrm{i}+2\mathrm{C}\mathrm{O}$

The metallurgical-grade silicon should be at least 98% pure [3, 4]. The solar-grade silicon has purity of 6N class (99.9999%) [5], while the very pure silicon of 9N class (at least 99.9999999%) is a basic electronic material for a production of computer chips. Single silicon crystals are most often prepared by the Czochralski method [6]. Polycrystalline silicon (commonly called “polysilicon”) has found huge applications for photovoltaic (PV) solar cells. It is the purest synthetic material available on the market. Polysilicon is produced from metallurgical-grade silicon by a chemical purification in the Siemens process, which involves distillation of volatile silicon compounds, and their decomposition into silicon at high temperatures [7, 8].

Similarly to the metallurgical-grade silicon, a silicon carbide (carborundum, SiC) was also produced by the Acheson method, from a sand and an excess of carbon (from coke) [9], at 2,500 °C in the following reactions:

(1.2) $\mathrm{S}\mathrm{i}{\mathrm{O}}_2+\mathrm{C}\stackrel{}{⟶}\mathrm{S}\mathrm{i}\mathrm{O}+\mathrm{C}\mathrm{O}$

(1.3)$\mathrm{S}\mathrm{i}\mathrm{O}+2\mathrm{C}\stackrel{}{⟶}\mathrm{S}\mathrm{i}\mathrm{C}+\mathrm{C}\mathrm{O}$

The sintered silicon carbide forms very hard ceramics which has been widely used as abrasive materials, for fabrication of car brakes, car clutches, and ceramic plates. It can be also applied in electric systems, electronic devices, and...