Ceramic coatings applications

Chemical vapor deposition (CVD) involves the reaction of gaseous reactants to form solid products. There are two general types of CVD processes (a) the thermal decomposition of a homogeneous gas to form a solid and (b) the chemical reaction of two or more gaseous species to form a solid. Both types of CVD reactions are used industrially to form a variety of important elements and compounds for semiconductor, superconductor, and ceramic coating applications. 

Tetravalent silicon is the only structural feature in all silicon sources in nature, e.g. the silicates and silica even elemental silicon exhibits tetravalency. Tetravalent silicon is considered to be an ana-logon to its group 14 homologue carbon and in fact there are a lot of similarities in the chemistry of both elements. Furthermore, silicon is tetravalent in all industrially used compounds, e.g. silanes, polymers, ceramics, and fumed silica. Also the reactions of subvalent and / or low coordinated silicon compounds normally lead back to tetravalent silicon species. It is therefore not surprising that more than 90% of the relevant literature deals with tetravalent silicon. The following examples illustrate why "ordinary" tetravalent silicon is still an attractive field for research activities Simple and small tetravalent silicon compounds - sometimes very difficult to synthesize - are used by theoreticians and preparative chemists as model compounds for a deeper insight into structural features and the study of the reactivity influenced by different substituents on the silicon center. As an example for industrial applications, the chemical vapor decomposition (CVD) of appropriate silicon precursors to produce thin ceramic coatings on various substrates may be mentioned. 

The carbides and nitrides of vanadium and titanium crystallize in the same face centered cubic (fee) system, and because of the closeness of their cell parameters (Table 15.1) form solid solutions. These ceramic materials exhibit interesting mechanical, thermal, chemical and conductive properties.1,2 Their high melting point, hardness and wide range of composition have therefore attracted considerable attention in the last decade. Moreover, their good abrasion resistance and low friction also make these ceramics attractive for protective coating applications.3-5 Chemical vapor deposition (CVD) is a commonly used technique for the production of such materials. In the conventional thermally activated process, a mixture of gases is used.6-9 In the case of TiC, TiN, VC and VN, this mixture is... 

The priority in this chapter lies in the description of small organosubstituted silanes and of small heterocycles that might be precursors for the production of new materials for high tech applications (e. g. polycrystalline silicon for photovoltaic purposes, thin ceramic coatings from CVD processes). 

Sol-gel chemistry has been extensively studied during the past decade. The basic reactions, hydrolysis, condensation, and complexation, involved in the formation of oxide networks from molecular precursors are now quite well described. The sol-gel process brings new opportunities in the field of materials science. It allows a powderless processing of glasses and ceramics. Coatings can be easily deposited directly from the solution onto a wide variety of substrates. Many patents have been taken and several products are now on the market. Other industrial applications will undoubtedly be developed during the next few years. 

Thus the chemistry leading to the desired ceramic product is quite satisfactory most of the requirements mentioned earlier are met. Initial evaluation of the polysilazane shows that it has promise in three of the main potential applications of preceramic polymers in the preparation of ceramic fibers and ceramic coatings and as a binder for ceramic powders. 

Porosity of Ceramics, Roy W. Rice Intermetallic and Ceramic Coatings, edited by Narendra B. Dahotre and T. S. Sudarshan Adhesion Promotion Techniques Technological Applications, edited by K. L. Mittal and A. Pizzi Impurities in Engineering Materials Impact, Reliability, and Control, edited by Clyde L. Briant Ferroelectric Devices, Kenji Uchino Mechanical Properties of Ceramics and Composites Grain and Particle Effects, Roy W. Rice Solid Lubrication Fundamentals and Applications, Kazuhisa Miyoshi... 

Ceramic coatings may be plasma sprayed onto both metal and non-metal bases. Application of these coatings on metal (steel and also non-ferrous metals) is especially significant since it allows the properties of the metals to be exploited at high temperatures where the unprotected metal would oxidize. Use is simultaneously made of the properties of the non-metallic materials which often cannot be manufactured as an all-ceramic component, in particular when large dimensions are involved. 

New silicon oxide ceramic coatings based on hydrogensilsesquioxane are now finding applications as interlayer dielectrics in new generation of multilayer semiconducting devices. These materials have excellent gap filling characteristics, low dielectric constants and are relatively simple to apply [23],... 

In this chapter we have seen that application of porous ceramic coatings on porous substrates for preparing membrane supports is a complex process. Every step has to be carried out successfully to obtain substrates or membranes themselves which fulfil the requirements. We have seen that models of the coating processes are useful but still far from capable of describing the processes completely. We have seen that specific aspects such as prevention of defect formation still defy quantitative and sometimes also qualitative understanding. We have seen that sccding-up is not a trivial matter and that much work has to be performed to enable successful preparation of large surface areas. 

High velocity suspension flame sprayed (HVSFS) hydroxyapatite coatings for biomedical applications, in Advanced Ceramic Coatings and Materials for... 

We devote a significant part of this chapter to the method of chemical vapour deposition, the development of which has been closely tied to the need to deposit thin films of a range of metals and inorganic materials for use in semiconducting devices, ceramic coatings and electrochromic materials. Table 27.3 lists some applications of selected thin film materials. Part of the challenge of the successful production of thin films is to find suitable molecular precursors, and there is much research interest in this area. 

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