REFRACTORY LAMINATE BASED ON NEGATIVE SOL ORE SILICATE AND POSITIVE SOL

摘要

A rapid process for forming a refractory laminate on the surface of a support structure which comprises dipping the surface alternately, in either order, in (1) a bath comprising a sol of negatively charged colloidal particles and/or a solution of an alkaline ionic silicate and (2) a bath comprising a sol of positively charged colloidal particles, until a laminate of the desired thickness is built up on the surface. In order to increase the rate of laminate build up, particulate refractory material can be included in the baths and/or the coated surface can be stuccoed between dips. Interaction between the negatively charged colloidal particles or silicate and the positively charged colloidal particles results in a setting action which immobilizes the coatings as they are applied, thus making it unnecessary to dry between dips. The process is particularly suited for making expendable, refractory shell molds for precision investment casting of metals by the so-called "lost-wax" technique.