Corrosion resistance of NZP and aluminum titanate

To determine the feasibility of using low thermal expansion ceramics and aluminum titanate in diesel engine applications, the mechanical and thermal properties and corrosion resistance were evaluated. NZP (Ba_1.25Zr₄P_5.5Si_.0.50₂₄ and Ca_0.5 Sr_O.5Zr₄P₆0₂₄) and aluminum titanate (AT) were exposed to a simulated diesel engine environment.

The effects of thermal cycling from room temperature to 700°C, and a combination of alkali corrosion and thermal cycling on the mechanical and thermal properties of these ceramics were examined. It was found that NZP and AT materials demonstrated near zero bulk thermal expansion, good thermal up shock resistance and resistance to Na and V corrosion, because of their porous structure and low density. However, the AT materials exhibited lower flexural strength. This is a direct result of the inherent micro cracking across the AT grains upon cooling from the sintering temperature, which reduces the flexural strength and elastic modulus.