Porous Ceramic Article with Engineered Pore Network
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Solution Overview
Problem
Current porous ceramic articles used in automotive catalytic converters and diesel particulate filters face challenges in achieving high porosity, large pore size, and thermal shock resistance while maintaining filtration efficiency and mechanical strength, especially under stringent emission regulations and thermal cycling conditions.
Innovation Solution
The development of porous ceramic articles using sinter bonded or reaction bonded engineered spheroidal particles with a specific pore network structure, which includes a method of forming green particles, calcining, mixing with a liquid vehicle, and firing to create a ceramic body with high porosity, large pore size, and improved thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high porosity and large pore size are achieved to enable high de-NOx efficiency and low pressure drop, then filtration efficiency and catalyst activity improve, but mechanical strength and thermal shock resistance deteriorate
Solution Approach 1:
The patent employs a porous ceramic microstructure with controlled pore size distribution (median pore size 18 μm or larger) and high porosity (around 60%) to achieve low pressure drop and high de-NOx efficiency while maintaining structural integrity through the specific pore network architecture
Solution Approach 2:
The patent uses composite ceramic materials, specifically cordierite and aluminum titanate, which combine multiple phases with complementary properties to achieve both high porosity and adequate mechanical strength, leveraging the anisotropic thermal expansion characteristics of these materials
2Quantity of substance
If high porosity and large pore size are achieved to enable high de-NOx efficiency, then catalyst loading and activity improve, but thermal shock resistance deteriorates due to microcracking
Solution Approach 1:
The patent addresses thermal shock resistance by utilizing materials with low and anisotropic thermal expansion coefficients (cordierite and aluminum titanate), and by controlling the microstructure to manage stress distribution during thermal cycling, reducing microcrack formation
Solution Approach 2:
The patent optimizes firing conditions (temperature, atmosphere, duration) and raw material composition to control the formation and distribution of pores and crystalline phases, thereby tuning the thermal and mechanical properties to achieve both high porosity and thermal shock resistance
3Stability of the object's composition
If cordierite or aluminum titanate ceramics are used to achieve low thermal expansion and high thermal shock resistance, then thermal stability improves, but microcracking increases due to anisotropy in thermal expansion
Solution Approach 1:
The patent addresses microcracking by controlling the local microstructure, including grain size distribution and phase distribution, to manage stress concentrations. The pore network structure is designed to accommodate thermal stresses and prevent crack propagation
Solution Approach 2:
The patent performs preliminary sintering and phase formation during the firing process to establish a stable microstructure before service, reducing the likelihood of microcrack formation during subsequent thermal cycling
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 achieves high porosity, large pore size, and enhanced thermal shock resistance, enabling efficient filtration and low pressure drop while maintaining mechanical strength, thus meeting stringent emission regulations and extending the lifespan of the ceramic articles.
Implementation Method 1
porous ceramic articles having microstructure including sinter bonded or reaction bonded large pre-reacted particles
Implementation Method 2
porous ceramic articles having microstructure including sinter bonded or reaction bonded large pre-reacted particles
Implementation Method 3
have to be highly porous to allow gas flow through the walls without restricting the engine power
Implementation Method 4
Both materials show anisotropy in their thermal expansion with different crystallographic directions exhibiting positive and negative expansion
Implementation Method 5
have to show high filtration efficiency for emitted particles
Data Source
AI summary
The present disclosure relates to porous ceramic articles and a method of making the same. The porous ceramic articles have microstructure of sinter bonded or reaction bonded large pre-reacted particles and pore network structure exhibiting large pore necks. The method of making the porous ceramic articles involves using pre-reacted particles having one or more phases. A plastic ceramic precursor composition is also disclosed. The composition includes a mixture of at least one of dense, porous, or hollow spheroidal pre-reacted particles and a liquid vehicle.