Ceramic Honeycomb Bleed-Through Barrier
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Solution Overview
Problem
Ceramic honeycomb bodies in catalytic converter applications experience bleed-through of aqueous catalyst solutions, leading to stains, aesthetic issues, and difficulties in accurately measuring catalyst application, as the solutions diffuse through the ceramic article.
Innovation Solution
Applying a hydrophobic cellulose derivative, such as ethylcellulose, to the exterior surface of the ceramic article creates a non-wettable barrier that limits the bleed-through of aqueous catalyst solutions, using methods like spray deposition or dip coating, and subsequent heating to ensure the derivative is strongly bound to the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aqueous catalyst solution is applied to a ceramic honeycomb body, then the catalyst facilitates pollutant reduction, but the solution diffuses through the honeycomb body and creates visible stains on the exterior surface
Solution Approach 1:
A hydrophobic barrier coating is applied to the exterior surface of the ceramic honeycomb body to act as an intermediary layer. This coating prevents the aqueous catalyst solution from diffusing through the ceramic walls and staining the exterior surface, while allowing the catalyst to remain effective on the interior surfaces where it is needed for pollutant reduction.
Solution Approach 2:
The surface properties of the ceramic exterior are modified by applying a hydrophobic coating that changes the surface energy and wetability parameters. This parameter change prevents the aqueous catalyst solution from penetrating through the ceramic walls, thereby eliminating the bleed-through staining problem while maintaining catalytic functionality.
2Quantity of substance
If the ceramic honeycomb body allows catalyst solution penetration, then catalyst distribution occurs throughout the structure, but accurate measurement of catalyst application becomes difficult
Solution Approach 1:
The hydrophobic barrier coating serves as a containment intermediary that restricts the aqueous catalyst solution to specific zones where it is applied. This prevents uncontrolled diffusion through the ceramic walls, enabling accurate measurement and control of catalyst application quantity and distribution.
Solution Approach 2:
The hydrophobic coating creates localized zones with different wetability properties. By applying the coating selectively or creating a uniform barrier, the catalyst solution is confined to specific regions, allowing precise control and measurement of catalyst distribution without unwanted diffusion to other areas.
3Object-affected harmful factors
If a hydrophobic cellulose derivative coating is applied to the exterior surface, then bleed-through is prevented, but the coating must be strongly bound to the surface through heating
Solution Approach 1:
The coating application process utilizes temperature parameter changes to achieve strong bonding. Heating the coated ceramic honeycomb body at controlled temperatures (e.g., 100-200°C) evaporates the solvent and promotes adhesion of the hydrophobic cellulose derivative coating to the ceramic surface, ensuring the coating remains firmly bound during subsequent catalyst application and handling.
Solution Approach 2:
The heating process induces phase transitions in the coating material, transitioning from a solvent-based applied state to a dried, bonded film state. This phase change ensures strong adhesion of the hydrophobic coating to the ceramic surface, preventing coating detachment while maintaining its bleed-through prevention functionality.
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 hydrophobic cellulose derivative effectively prevents or reduces bleed-through, maintaining the article's aesthetics, allowing accurate catalyst measurement, and ensuring the derivative's removal during calcination does not affect the ceramic's properties.
Implementation Method 1
applying a hydrophobic cellulose derivative to an exterior surface of an outermost peripheral skin of the fired ceramic article... creates a non-wettable surface condition on the exterior surface
Data Source
AI summary
Methods for limiting bleed-through of aqueous catalyst solutions in ceramic articles are described herein. The methods include applying a hydrophobic cellulose derivative, such as ethylcellulose, to an exterior surface of a fired porous ceramic article. The aqueous catalyst solution is applied to the fired porous ceramic article, such that the hydrophobic cellulose derivative limits bleed-through of the aqueous catalyst solution through at least a portion of the ceramic article. Ceramic articles with skins that limit bleed-through of aqueous catalyst solutions are also described herein.