NEW LOW THERMAL EXPANSION STRUCTURAL CERAMICS

OVER THE PAST FEW YEARS, A NEW FAMILY OF MATERIALS CALLED NZP (NAZR2 (PO4)3 AND ITS ANALOGS) HAS BECOME WELL KNOWN FORITS LOW THERMAL EXPANSION BEHAVIOR. RECENTLY, IT HAS BEEN SHOWN THAT ZR4 (PO4)6 AND SRZR4(PO4)6 HAVE OPPOSITE ANISOTROPY IN THERMAL EXPANSION AS WELL AS OPPOSITE BULK THERMAL EXPANSION AND THAT THEIR SOLID SOLUTION RESULTS IN LOWER ANISOTROPY AND NEAR ZERO THERMAL EXPANSION. THESE MATERIALS AND THEIR ANALOGS HAVE GREAT POTENTIAL FOR USE IN HIGH TEMPERATURE APPLICATIONS. THE REDUCED ANISOTROPY REFLECTS THE ADVANTAGE OVER SOME MATERIALS, SUCH AS ALUMINUM TITANATE, CORDIERITE, AND OTHERS, THAT ARE CURRENTLY USED IN HIGH TEMPERATURE APPLICATIONS. THEREFORE,IT IS POSSIBLE TO DEVELOP NEW MATERIALS WITH HIGH THERMAL SHOCK RESISTANCE AND CONTROLLED THERMAL EXPANSION. THE MAJOR ADVANTAGES OF THESE MATERIALS ARE THEIR FLEXIBILITY TOWARDS IONIC SUBSTITUTION, THEIR TAILORABILITY OF THE BULK AND AXIAL THERMAL EXPANSION, AND THEIR ABILITY TO OPERATE SAFELY AND RELIABLY OVER A WIDE RANGE OF SEVERE THERMAL SHOCK AND TEMPERATURE CYCLING. IN ADDITION, THESE MATERIALS ARE EASY TO SYNTHESIZE IN THEIR SINGLE PHASE FORMS USING INORGANIC SOL-GEL SYNTHESIS TECHNIQUES. THE PHASE I EFFORTS SHOULD DEMONSTRATE THE FEASIBILITY OF THE CONCEPT OF FABRICATING DENSE CERAMIC BODIES OF VARIOUS DIFFERENT COMPOSITIONS HAVING LOW THERMAL EXPANSION, HIGH THERMAL SHOCK RESISTANCE, AND ADEQUATE MECHANICAL STRENGTH.