PRODUCTION of POWDER SILICON CARBIDE from POLY(HYDRIDOCARBYNE) DOPED POLY (SILYNE-CO-CARBYNE) POLYMERS

Industrial ceramics are ceramics such as diamond, diamond-like-carbon (DLC), silicon carbide (SiC), silicon oxycarbide (SiOC), and silicon dioxide (SiO2), the most widely used examples. Controlling the shape, structure, production conditions and morphology of the produced ceramics is an important parameter that is highly desired. As it is known, the physical and chemical properties of these hard ceramic materials make it difficult to process or shape them. In other words, the properties it possesses make it difficult to produce these ceramics as needle-shaped, rod-shaped, fiber-structured or as a film on a surface. Many studies are carried out to overcome these problems with the production of ceramics in various morphologies and forms from some special polymers, and it stands out as a method with a high potential to be applied in the future. Ceramic production from polymers can be made with a special polymer group called ceramic precursors. The most common polymer groups used for this purpose are polycarbyne, polysilane and polysilyne. The chemical structures of ceramic prepolymers are similar to the desired ceramic structure. Poly(hydridocarbyne) (PHC) is a one of the polycarbyne polymer group, which resembles a diamond structure. Poly(silyne-co-carbyne) or polycarbosilane (PSK) polymers are from the polysilyne group, which has similar structure with a SiC. Therefore, they are easily converted into ceramics by heat treatment of polymers in inert atmosphere and under atmospheric pressure. Another advantage of ceramic precursors is that they dissolve in common and inexpensive organic solvents. Thus, these polymers can be produced in any shape and thickness, as a film on the desired surface, or as a fiber. In addition, ceramic prepolymers can be synthesized by a wide variety of production methods. Sonochemical, Grignard and electrochemical methods are common synthesis methods. Since the reagents used in the sonochemical method are explosive (for example, NaK metal alloy that reacts with moisture in the air) and special equipment are needed, thus these limit to use these production methods in industry and other areas. Chemical synthesis with Grignard reagents is a difficult and very low yield method.The electrochemical method is a simple, non-hazardous and highly efficient method that allows large quantities of production. In the thesis, PHC and PSK polymers were produced by the electrochemical method as in previous studies. PHC was synthesized using chloroform and hexachloroethane as monomers under 6V potential. PSK was synthesized using 1,2-bis(trichlorosilyl) ethane monomer under 8V potential. Characterization of polymers was performed using UV/Vis, FTIR and 1H-NMR spectroscopic methods and TGA and DSC thermal analysis methods. Mixtures of polymers were prepared at certain mass ratios and then ceramic production was carried out by sintering them in a tube furnace under argon atmosphere for 24 hours. The morphological structures of the obtained powder materials were illuminated by optical microscope and SEM, the crystal structures of ceramic materials were also made using X-Ray spectroscopy.