Israeli researchers have begun pilot-scale production of a new high-temperature thermal ceramic insulator that may become a safe substitute for asbestos and other harmful ceramic fibres. The new material is a ceramic foam that contains 94% to 96% air by volume, but can resist temperatures above 1700° C.
The foam is being developed under the direction of chemical engineering professor Gideon Grader at the Technion-Israel Institute of Technology. Professor Grader established a new company, Cellaris, at the Technion’s Entrepreneurial Incubator Company to produce the foam.
The lung ailments, including cancer, which can be caused by asbestos, have led to a search for other high-temperature insulating materials.
But the ceramic fibres that have replaced asbestos also produce needle-shaped dust particles that can be dangerous to the lungs when inhaled. In contrast, the crushing of Cellaris’ ceramic foam produces ordinary dust particles similar in shape to those common in the environment.
The foam is made of aluminium oxide, a common high-temperature ceramic, but derives its insulating powers from the many tiny air bubbles within the material. The foam can be used not only for thermal insulation, but also for a variety of other applications such as acoustic insulation and adsorption of environmental pollutants.
The foam is generated from special crystals that contain the metal components and all the foaming ingredients. Upon heating, the crystals form a solution.
Within this solution a reaction takes place, forming polymer chains. After the chains grow sufficiently, the solution suddenly separates into a pure solvent and the polymer.
At this point, the solvent begins to boil, forming trillions of tiny bubbles that blow the polymer into a foam, stabilised by the polymer chains. Subsequent heating to high temperatures leaves behind the ceramic, metal oxide foam.
‘With only four to five percent of the foam’s volume taken up by the ceramic, the material is an effective insulator that can compete with today’s high-end, state-of-the-art ceramic fibres,’ said Professor Grader. ‘Its low density can be important in applications where weight is at a premium. On a weight-for-weight comparison, the foam can offer safe, cost-effective insulation.’