BigPatents India

Alumina/ alumina, mullite/high alumina porcelains, zirconia/ zirconia, silicon carbide/ silicon carbide, mullite/ zirconia and alumina/ zirconia ceramic joints prepared by using magnesium alumino silicates (MAS), magnesium silicates (MS), calcium silicates (CS), calcium magnesium silicates (CMS) or calcium magnesium alumino silicates (CMAS) as joining media showed higher bending strength and high temperature stability. These ceramic/ ceramic joints are found to 'withstand temperatures >1550oC. Procedure for the preparation of joints is very simple and straightforward. The method of preparation of the joints is as follows: (i) homogenization of source materials for the joining medium using ball milling in presence of a suitable organic liquid medium, (ii) drying, precalcinations followed by annealing of the homogenized mixtures, (iii) surface treatment of the heat- treated powders with wetting agents and deflocculants, (iv) preparation of the slurry of surface treated powders using organic or inorganic binders, (v) adding antifoaming agents to the slurry to avoid bubble formation,(vi) coating of the slurry on the joining parts (alumina substrates) and curing inside a hot air-oven and heat-treating the green joints at a suitable higher temperatures. The joining of ceramic parts, particularly alumina takes place by the liquid phase assisted reaction bonding that sets in between the substrates and the joining medium.