Narrow pore size distribution aluminum titanate body and method for making same

Abstract

This invention relates to an aluminum titanate body having a narrow pore size distribution as characterized by the relation (d50−d10) / d50 being less than 0.50 corresponding to a high degree of interconnected porosity. The body also preferably exhibits a low coefficient of thermal expansion of less than 15×10−7 C−1, high porosity of at least 38% by volume, and at least 0.10% by weight metal oxide, the metal being either yttrium, calcium, bismuth, a lanthanide metal or combinations of thereof. MOR is preferably at least 450 psi. Median pore diameter is preferably at least 8 microns. The inventive ceramic body is particularly useful as a wall-flow filter for a diesel exhaust. A method of fabrication is provided where the sintering temperature is preferably between 1375°-1550° C.

Description

RELATED APPLICATIONS [0001] The present invention is a continuation of U.S. patent application Ser. No. 11 / 193,123 to G. Merkel filed Jul. 28, 2005 entitled “Narrow Pore Size Distribution Aluminum Titanate Body and Method for Making Same,” which is a continuation-in-part application of U.S. patent application Ser. No. 10 / 902,381 to G. Merkel filed Jul. 29, 2004 and entitled “Mullite-Aluminum Titanate Body And Method For Making Same,” now abandoned.FIELD OF THE INVENTION [0002] The present invention relates to an aluminum titanate ceramic body that has improved properties for use in high temperature applications and a method for making the same. BACKGROUND OF THE INVENTION [0003] Porous refractory ceramics have long been used as particulate filters in hot gas or corrosive environments such as advanced coal-based gas turbine cycles, municipal and industrial waste incinerators, and diesel or natural-gas engine exhaust systems. For such applications, ceramic particulate filters must pos...

AI Technical Summary

Benefits of technology

"The present invention relates to ceramic bodies with narrow pore size distribution, high porosity, low thermal expansion, and good thermal shock characteristics. These ceramic bodies are suitable for use in high temperature applications such as wall-flow filters for diesel exhaust filtration. The ceramic body has a coefficient of thermal expansion of less than 15×10−7 C1, a porosity of at least 38% by volume, and a narrow pore size distribution with a relation (d50−d10) / d50 being less than 0.35. The ceramic body also exhibits high strength, with a modulus of rupture of at least 450 psi, and good thermal shock characteristics. The ceramic body can be fabricated at lower sintering temperatures using a metal oxide sintering additive."

Problems solved by technology

However, the relatively low volumetric heat capacity (approximately 2.8 J cm−3° C.−1 at 800 K) and low thermal conductivity of cordierite can result in unacceptably high temperatures during operation when the filters are regenerated under certain conditions.

Further, obtaining a well-interconnected pore microstructure in cordierite filters, in combination with low porosity required for high thermal mass, has been a challenge.

However, silicon carbide is relatively expensive.

Furthermore, the high coefficient of thermal expansion requires silicon carbide filters to be fabricated as cement-bonded segments, adding to manufacturing cost and raising concerns about their long-term thermo-mechanical durability.

However, in the manufacture of AT and MAT bodies, high sintering temperatures greater than 1600° C. are often required to achieve sufficient grain growth for microcracking and low thermal expansion.

Such high heating temperatures add cost to manufacturing and final product.

Nonetheless, such methods often result in a strong sensitivity of the physical properties, including CTE, porosity, or pore size, to the firing temperature, which is undesirable for manufacturability.

Also, desired properties for DPF use are not expected to be achieved.

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