Strong, Low Thermal Expansion Niobate Ceramics

A new family of low thermal expansion niobate ceramics was discovered that sinter to form unusual high permeability microstructures. The coefficient of thermal expansion (CTE) can be tailored from -4 x 10(-7)/degrees C to +40 x 10(-7)/degrees C by control of composition and firing temperature. The inherent vapor-phase transport sintering gives rise to low to negative firing shrinkage, more than 50% porosity, and a microstructure of loosely packed interlocking acicular grains that result in highly permeable porous filters with good strength and low backpressure in clean and soot-loaded conditions. The acicular grains show extensive solid solution with multiple components that enables a large compositional flexibility for engineering properties. The low thermal expansion and high strength coupled with the low structural Young's modulus of the fibrous microstructure give these materials excellent thermal shock resistance. Titanium and zirconium niobates are resistant to potassium-based NOx adsorbers up to 900 degrees C, are chemically durable, thermally stable, and suitable for diesel particulate filters and catalyst supports.