| Titanium diboride (TiB2) is a refractory ceramic that has unique properties of high hardness, high melting point, and electrical conductivity. It also has excellent corrosion resistance against metallic aluminum and cryolite, which makes it best candidate as a coating material for the inert cathodes in Hall-Heroult cells for aluminum electrolysis. Various coating techniques such as PVD, CVD and plasma spraying, etc. have been studied to form TiB 2 coatings, however, only thin coatings (<700mum) can be obtained and thin TiB2 coating will be worn out in a short time during cell operation.; A simple 'aqueous spraying-drying-sintering' coating process has been developed in this study to produce a highly thick (>1 mm) and functional composite TiB2 coating on carbon substrate, in which, inorganic colloidal alumina sol is initially used as the forming aid as well as sintering aid. The coatings formed by this technique exhibit good mechanical properties and electrical conductivity, strong bond to the substrate, and great thickness capability.; This presentation explains this unique coating process and shows an extensive investigation on the so-called colloidal alumina bonded titanium diboride composite coating. Each stage of coating process has been thoroughly studied in terms of processing parameters, properties and mechanics analysis. Features associated with aqueous coating process, such as viscosity, drying rate, are considered; physical and mechanical properties, such as density and porosity, strength and electrical conductivity, are examined; microstructures throughout the coating matrix and the interface are characterized, and the relationship of critical cracking thickness between materials properties and drying condition is mathematically modeled.; This work results in the clarification on the effectiveness and applicability of colloidal alumina bonded TiB2 coating process from the experimental and theoretical points of view. |
