Coatings and Thick Films

The term thick film does not just refer to film thickness but rather to layers or a coating made by certain processing techniques. Most of the methods that we describe in this chapter involve suspending ceramic particles either in a solution or in a mixture of organic solvents (known as the vehicle). It will be necessary to remove all the volatile material from the coating to produce a dense adherent ceramic layer. Many of the processes described in this chapter are relatively inexpensive (at least compared to those used to produce thin films that we describe in Chapter 28) and simple. 

All of these techniques are important in industry and you should know the language of thick films, e.g., slurry, slip, and paste. 

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Kozuka H. Issues on crack formation in sol-gel-derived ceramic coatings and thick film formation. 

Kozuka H., Takenaka S., Tokita H., Hirano T., Higashi Y., Hamatani T. Stress and cracks in gel-derived ceramic coatings and thick film formation. J. Sol-Gel Sci. Technol. 2003 26 681-686... 

Figure 2. Steady-state cyclic voltammograms of Cu electrodes, both bare and coated with thick films (approximately 15 pm) of BTA, PVI-1, or UDI in 0.1 M HCIO, in air, v = 50 mV/s, w = 15 Hz, 25 "C. ...

Another important aspect is the proximity of particle layer and thin or thick films, whereby the border between thin and thick films remains ambiguous. Conventional processing of particle assemblies comprises molding of the particle mass, like dry compression or wet casting. In the case of nanoparticles, to form a film is much more rational than conventional powder processing. In a dry procedure, production of nanoparticles and film formation in most cases take place simultaneously. An assembly of nanoparticles can also be formed in a wet procedure by precipitation on the templates or even by simple dip or spin coating from a sol containing nanoparticles. 

Relatively high dichroic ratio up to 2.3 due to geometry of the molecule (high aspect ratio of Direct Red 80) has been achieved (Advincula et al., 2003). To manufacture these films with PD ADM AC of ca. 100-nm thickness, 100 layers were necessary. Less effective photoorientation of spin-coated and LbL films with other polyelectrolyte (PAH, PEI) was attributed to specific formation of J-aggregates in LbL films. In the LbL films produced from chitosan and Sunset Yellow (dos Santos et al., 2002), spontaneous birefringence of 0.04 for the film of 300-nm thickness was observed however, the value was not affected by the light. This fact underlines the importance of selection of dye and polyelectrolyte. 

The frequency shift predicted from the first term of Equation 1 is proportional to the product of the density of the coating and the film thickness. Since density decreases with temperature and film thickness... 

Uses Rheology modifier for coatings, spray and thick film applies. Features Highly pseudoplastic rheology solvent-free used with Acrysol RM-2020NPR for exc. flow/sag/syneresis balance Properties Vise. 2800-4000 cps nonionic 19% solids in water Acrysol RM-825 [Rohm Haas]... 

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