Mullite-aluminum titanate body and method for making same

Inactive Publication Date: 2006-02-02
CORNING INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008] MAT ceramic bodies of the present invention offer low thermal expansion, high thermal shock resistance, a narrow pore size distribution and greater interconnectivity of the porosity, and are fabricated at lower sintering temperatures of between 1375° C.-1550° C. by using a metal oxide sinte

Problems solved by technology

However, the relatively low volumetric heat capacity (approximately 2.8 J cm−3 ° C.-−1 at 800K) 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

Method used

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  • Mullite-aluminum titanate body and method for making same
  • Mullite-aluminum titanate body and method for making same
  • Mullite-aluminum titanate body and method for making same

Examples

Experimental program
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Example

[0038] Examples prefixed by the letter “C” denote comparative (non-inventive) examples. Amounts of phases measured by powder XRD are denoted as major (M), minor (m), very minor (vm), trace (tr), small or very small trace (s.tr. and v.s.tr), or absent (0). Examples in Tables 2 to 19, and 23, were fired in electric furnaces; those in Tables 20-22 utilized either gas or electric furnaces, as indicated in the tables. In Tables 2-23, “MPS” denotes median particle size (diameter) in micrometers. MPS of the inorganic raw materials is equivalent to D50 and is also in micrometers. In the examples of Tables 2 to 23, the MPS of all inorganic raw materials includes contributions from alumina, aluminum hydroxide, titania, kaolin, and quartz.

Example

[0039] Examples C1 and C2 in Table 2 show that, in the absence of a metal oxide addition selected from the inventive group of compounds, ceramic bodies of aluminum titanate+mullite fired at 1400 or 1500° C. have a CTE greater than 15. Comparative examples C3 and C4 show that, although the addition of 2.78% Y2O3 reduces the CTE to less than 15, the median pore size is undesirably less than 8 microns when the weighted average of the median particle sizes of the inorganic raw materials is less than 6 microns.

[0040] Table 3 shows that, even when the weighted average of the median particle sizes of the inorganic raw materials is greater than 6 microns, the CTEs of the aluminum titanate +mullite ceramics are greater than 15 and the median pore sizes are less than 8 microns in the absence of a metal oxide addition selected from the inventive group of compounds, regardless of whether the compositions are fired at 1400° C. or at 1500° C. Furthermore, in the absence of the inventive sinterin...

Example

[0042] Examples 2 and 3 further show that the %porosity of the ceramic bodies is desirably increased by the addition of at least 1.0 wt % MoO3 to the raw materials. FIG. 1 illustrates that the microstructure of Inventive Example 16 consists of “domains” of radiating aluminum titanate crystals. Such domains provide a unique microstructure that may influence the nature of the microcracking in the inventive ceramics. This microstructure is contrasted with that of Comparative Example C5 in FIG. 2, which depicts the lack of domains when an inventive metal oxide additive is absent.

[0043] The examples in Table 5 illustrate that firing the inventive compositions at 1500° C. still yields very low CTE and a median pore size greater than 8 microns while still preserving desirable high porosities. Thus, the inventive sintering additives do not result in excessive densification of the ceramic bodies with increasing temperature, and are therefore conducive to manufacturing processes that do not ...

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Abstract

This invention relates to a mullite-aluminum titanate body having a low coefficient of thermal expansion of less than 15×10−7 C−1, a high porosity of at least 38% by volume, a median pore diameter of at least 8 microns, and 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 inventive ceramic body also contains at least 0.10% by weight metal oxide, the metal being either yttrium, calcium, bismuth, a lanthanide metal or combinations of thereof. The inventive ceramic body is particularly useful as a wall-flow filter for diesel exhaust. A method of fabrication is provided where the sintering temperature is between 1375°-1550° C.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a mullite-aluminum titanate ceramic body that has improved properties for use in high temperature applications and a method for making the same. [0002] 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 possess chemical inertness, thermal shock resistance, high filtration efficiency, low pressure drop, and adequate strength. In particular, a diesel particulate filter (DPF) ideally combines low CTE (for thermal shock resistance), low pressure drop (for engine efficiency), high filtration efficiency (for removal of most particles from the exhaust stream), high strength (to survive handling, canning, and vibration in use), and low cost. [0003] Candidate materials for D...

Claims

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Application Information

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IPC IPC(8): B01D46/00
CPCB01D46/2429B01D46/244B01D46/2444B01D2046/2433B01D2046/2437B01D2046/2496B01D2279/30C04B35/185C04B35/478C04B35/6263C04B35/632C04B38/0006C04B2111/00129C04B2111/00793C04B2235/3205C04B2235/3208C04B2235/3213C04B2235/3217C04B2235/3218C04B2235/322C04B2235/3222C04B2235/3224C04B2235/3225C04B2235/3227C04B2235/3229C04B2235/3231C04B2235/3232C04B2235/3236C04B2235/3244C04B2235/3251C04B2235/3256C04B2235/3258C04B2235/3284C04B2235/3286C04B2235/3293C04B2235/3298C04B2235/3409C04B2235/3418C04B2235/3454C04B2235/3463C04B2235/349C04B2235/445C04B2235/5436C04B2235/5445C04B2235/656C04B2235/6567C04B2235/77C04B2235/80C04B2235/96C04B2235/9607F01N3/022F01N2330/06F01N2330/14Y02T10/20Y10S55/05Y10S264/48Y10S55/30Y10S55/10C04B38/0074C04B38/0009C04B38/0051C04B38/0054Y02T10/12B01D46/24492B01D46/24491B01D46/2498B01D46/24494
Inventor MERKEL, GREGORY A.
Owner CORNING INC
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