Flow Modulation Member for Ceramic Honeycomb Debindering
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Solution Overview
Problem
The manufacturing of ceramic honeycombs faces significant cracking issues during the debindering process due to uncontrolled burning of organic constituents, leading to thermal gradients and stresses, despite existing approaches like low oxygen atmospheres and reduced heating rates, which still result in significant cracking in fired ceramic honeycombs.
Innovation Solution
A method and apparatus involving a circulating oxygen-containing atmosphere with a flow modulation member to restrict oxygen circulation through the top face of the ceramic green body, maintaining a higher steam concentration and lower oxygen levels, thereby controlling decomposition and oxidation reactions to reduce cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen circulation is unrestricted during debindering, then combustion rate of organics is high and heating efficiency is improved, but thermal gradients increase causing cracking
Solution Approach 1:
The patent applies local quality by creating different oxygen circulation conditions in different regions of the green body. The top face is covered with a flow modulation member (perforated plate or honeycomb structure) that restricts oxygen flow locally, while the bottom and sides maintain normal oxygen circulation. This localized control allows the top region to decompose organics slowly without thermal runaway, while other regions continue efficient combustion, resolving the contradiction between overall debindering rate and prevention of top-face cracking.
Solution Approach 2:
The patent segments the oxygen circulation path by introducing a flow modulation member that divides the atmosphere flow into restricted zones (under the cover) and unrestricted zones (around the edges and bottom). This segmentation allows different parts of the green body to experience different oxygen concentrations, enabling controlled decomposition in the top region while maintaining efficient combustion elsewhere, thus preventing cracking without sacrificing overall productivity.
2Object-affected harmful factors
If heating rate is reduced to prevent thermal gradients, then cracking is reduced, but debindering time increases
Solution Approach 1:
The flow modulation member creates local quality differences in oxygen availability, allowing the top face to be protected from rapid combustion while the rest of the body undergoes efficient debindering. This enables the use of higher overall heating rates without causing thermal runaway at the top, thus reducing total debindering time while preventing cracking.
3Object-affected harmful factors
If oxygen concentration is reduced throughout the body, then combustion control is improved and cracking is reduced, but decomposition efficiency decreases
Solution Approach 1:
The patent segments the oxygen concentration field into two regions: a low-oxygen region under the flow modulation member cover where controlled decomposition occurs, and a normal oxygen concentration region around the edges and bottom where efficient combustion takes place. This spatial segmentation maintains high overall decomposition efficiency while preventing cracking in the critical top region.
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
This approach significantly reduces cracking in ceramic honeycombs by creating a uniform reaction pattern, maintaining lower internal stresses, and improving the firing yield, as evidenced by reduced thermocouple temperature spikes and fewer defects in the fired products.
Implementation Method 1
heating the green body in a circulating oxygen-containing atmosphere to decompose and oxidize organic binding and pore-forming constituents
Implementation Method 2
heating the green body in a circulating oxygen-containing atmosphere to decompose and oxidize organic binding and pore-forming constituents
Implementation Method 3
heating the green body in a circulating oxygen-containing atmosphere
Data Source
AI summary
An apparatus and method for debindering a cellular ceramic green body. The apparatus includes a flow modulation member to selectively restrict circulation of a heated oxygen-containing atmosphere through a top of a cellular core section of the green body. The method includes heating the green body in a circulating oxygen-containing atmosphere while selectively restricting circulation of the atmosphere through the top of the cellular core section of the green body.