Tech Briefs

AFRL scientists are developing a new class of inexpensive ceramic-like materials.

The use of ceramics in an ancient culture is one measure of that society's overall technical sophistication. Combining the study of ancient ceramics with modern science and technology has led to the creation of new ceramics with superior properties. Victor Glukhovsky, a scientist working in the Ukraine half a century ago, researched differences in the durability of ancient cements and more modern concretes. His work ultimately led to the synthesis of various aluminosilicate binders from clays, feldspars, volcanic ashes, and slags. These binders exhibited properties superior to those of the cementitious materials in common use at that time. Decades after Glukhovsky's discoveries, Ukrainian builders continued to employ aluminosilicate binders in construction applications, confirming their outstanding durability.

In the 1970s, French Professor Joseph Davidovits investigated the construction of the Great Pyramids of Egypt. He concluded (almost assuredly incorrectly) that they could not have been built from quarried rock, surmising that the large aluminosilicatebased blocks that form the pyramids must have instead been synthesized in place. Prof Davidovits' endeavor to explore the possible mechanisms for producing such blocks led, by 1979, to the practical invention of geopolymers. While these aluminosilicates share much in common with Glukhovsky's building cements, they constitute a new class of materials. They are formed by condensation polymerization and, unlike calcium-based cements, do not incorporate waters of hydration within a crystal structure. Consequently, geopolymers are stronger than cementbased materials, impermeable to water, and far more resistant to degradation by acids or high temperatures.

ImageAlthough geopolymers possess many useful properties and are relatively inexpensive to make, they have not found widespread acceptance as substitutes either for current cements, mortars, or pastes or for conventional ceramics. Materials scientists offer many explanations for the comparatively slow emergence of geopolymers into the marketplace, but from the perspective of AFRL scientists, the geopolymer knowledge base is not yet sufficient to support widespread industrial use of these materials. To expand the use of this promising technology, AFRL is using Small Business Technology Transfer (STTR) contracts and basic research sponsored by the laboratory's Asian Office of Aerospace Research and Development to fund three different research teams in their efforts to explore and advance geopolymer science and technology. Specifically, the goal of these efforts involves developing a better understanding of the chemistry and physics associated with geopolymers, generating geopolymer performance data, and exploring improved geopolymer-based materials.

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