Cordierite Honeycomb Microcrack Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Porous cordierite honeycomb ceramics used in catalytic converters and particulate filters face challenges with strength and thermal shock resistance due to the need for microcracking, which limits their utility in applications requiring high thermal shock resistance and low coefficient of thermal expansion.
Innovation Solution
Development of high-porosity cordierite honeycomb bodies with little or no microcracking, achieved through specific composition and firing processes, that maintain high thermal shock resistance and increased coefficient of thermal expansion, allowing for improved strength and reduced microcrack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microcracking is introduced to achieve low coefficient of thermal expansion, then thermal shock resistance is improved, but strength is reduced
Solution Approach 1:
The patent changes the microstructural parameters by controlling the formation and distribution of microcracks through specific firing conditions and composition ratios. By optimizing these parameters, the patent achieves a balance where thermal shock resistance is improved while strength degradation is minimized, resolving the contradiction between these two properties.
Solution Approach 2:
The patent creates a composite microstructure combining cordierite crystals with controlled microcracks and glass phases. This composite structure allows the material to exhibit both low thermal expansion (through the cordierite crystal orientation) and improved thermal shock resistance (through the microcrack network), while the glass phase binds the cracks to maintain strength.
2Productivity
If wall thickness is reduced to meet strength requirements, then productivity is improved, but strength is reduced
Solution Approach 1:
The patent changes the material parameters by optimizing the cordierite crystal orientation and microcrack distribution to achieve higher strength-to-weight ratio. This allows the use of thinner walls while maintaining required strength levels, thereby improving productivity without sacrificing strength.
Solution Approach 2:
The patent exploits thermal expansion differences between the cordierite crystals and the glass phase to create self-healing microcracks during firing. This controlled thermal expansion effect strengthens the overall structure, allowing reduced wall thickness while maintaining strength requirements.
3Speed
If porosity is increased to reduce thermal mass, then light-off speed is improved, but strength is reduced
Solution Approach 1:
The patent optimizes the porosity parameters and microcrack distribution to achieve optimal light-off speed while maintaining structural integrity. By controlling the size, distribution, and connectivity of pores and microcracks, the patent enables higher porosity without excessive strength loss.
Solution Approach 2:
The patent creates a composite structure where the cordierite crystal matrix is reinforced with glass phases and controlled microcracks. This composite approach allows increased porosity for faster light-off while the glass phase binds the microcracks to maintain sufficient strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the production of ceramic honeycombs with enhanced strength and thermal shock resistance, suitable for applications with thin walls and low cell densities, reducing back pressure and thermal mass, while maintaining high porosity and catalyst storage capacity.
Implementation Method 1
the need to secure low CTEs in cordierite ceramic honeycombs has continued to dictate that microcracking necessarily be present
Implementation Method 2
exhibiting high thermal shock resistance and low coefficient of thermal expansion
Implementation Method 3
reaction-sintered cordierite substrates prepared from extruded mixtures of talc, alumina, and kaolin
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed are high-porosity cordierite honeycomb substrates having a narrow pore size distribution, little or no microcracking, and high thermal shock resistance. The porous ceramic honeycomb substrates generally comprise a primary cordierite ceramic phase as defined herein. Also disclosed are methods for making and using the cordierite substrates.