Shear Binder Agglomerates for High Porosity Ceramic Honeycombs
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Solution Overview
Problem
The challenge in manufacturing porous ceramic honeycombs, such as catalytic converters and particulate filters, is maintaining high porosity and structural integrity during firing, as existing methods often result in porosity loss due to excessive sintering and shrinkage, especially when using pre-reacted ceramic beads with high amounts of pore formers.
Innovation Solution
Incorporating green shear binder agglomerates composed of inorganic filler particles in a polymeric binder matrix, which deform under shear stress to form bridges between ceramic beads, providing structural support and increasing porosity by allowing for reduced bead packing density during firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pre-reacted ceramic beads with high amounts of pore formers are used, then porosity is increased, but structural integrity deteriorates due to excessive sintering and shrinkage
Solution Approach 1:
The patent introduces a binder system comprising clay particles and organic binder that acts as an intermediary between ceramic beads during the green body stage. This binder system provides temporary structural support that prevents excessive sintering and shrinkage during firing, thereby maintaining both high porosity and structural integrity in the final fired product.
Solution Approach 2:
The patent controls the firing temperature parameter to optimize the balance between porosity maintenance and structural integrity. By carefully selecting and controlling the firing temperature, the process achieves high porosity (>60%) while preventing excessive sintering that would compromise structural strength.
2Strength
If bead packing density is increased to maintain structural integrity, then porosity decreases
Solution Approach 1:
The binder system serves as a mediating phase that allows ceramic beads to be held together at lower packing densities. The organic binder and clay particles create a green body matrix that maintains structural integrity even when beads are spaced further apart, thereby enabling higher porosity without sacrificing strength.
Solution Approach 2:
The patent creates a composite green body structure consisting of ceramic beads dispersed in a binder matrix (clay + organic binder). This composite approach allows the weak individual beads to be supported by the binder matrix, maintaining structural integrity at low packing densities and thus enabling high porosity.
3Quantity of substance
If porosity is increased to improve permeability, then structural integrity deteriorates due to collapse and shrinkage during firing
Solution Approach 1:
The organic binder and clay matrix provide beforehand cushioning support to the ceramic bead structure during the vulnerable green body and firing stages. This protective matrix prevents collapse and excessive shrinkage that would otherwise occur when attempting to maintain high porosity, ensuring structural reliability is preserved even with >60% porosity.
Solution Approach 2:
The patent optimizes the firing temperature parameter and binder composition to achieve a controlled transformation during firing. The organic binder burns out and clay sinters at controlled rates, providing structural support that prevents collapse while allowing porosity to be maintained at levels greater than 60%.
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 use of green shear binder agglomerates enhances the porosity of fired ceramic bodies to greater than 60% while maintaining structural integrity, preventing collapse and shrinkage, and ensuring consistent geometry, thereby improving the permeability and surface area of ceramic materials.
Implementation Method 1
green shear binder agglomerates having a median agglomerate size that is from 20% to 120% of the median bead size, each green shear binder agglomerate comprising inorganic filler particles in a polymeric binder matrix
Implementation Method 2
During firing, the inorganic components of the deformed agglomerates (e.g., bridges or ribbons) react together and/or sinter together and with the ceramic beads to provide structural support to the fired honeycomb article
Data Source
AI summary
A ceramic precursor mixtures for extrusion and firing into porous ceramics. The ceramic precursor mixtures include ceramic beads and green inorganic shear binder agglomerates. The green inorganic shear binder agglomerates can include inorganic filler particles and a polymeric binder. The green inorganic shear binder agglomerates can deform under an applied shear stress during mixing and/or extrusion such that they are smeared into a plurality of interbead gaps between adjacent ceramic beads or pore former particles. During firing, the smeared green inorganic shear binder agglomerates can sinter and react to form ribbons extending between, and interconnecting adjacent ceramic beads.