Pore Density、Wall Thickness and Open Porosity
Briefly introduce the relationship between pore density, wall thickness, and porosity.
Pore Density, Wall Thickness, and Open Porosity
In the design and manufacturing of honeycomb ceramics, pore density, wall thickness, and open porosity are three core and closely interdependent technical parameters. They collectively determine the final performance of the product.
Core Definitions
Pore Density: The number of channels per unit cross-sectional area, typically measured in pores per square inch (pores/square inch). It directly determines the geometric specific surface area of the honeycomb ceramic. Higher pore density results in a larger surface area available for reaction or heat transfer per unit volume.
Wall Thickness: The thickness of the partition wall between two adjacent channels. It determines the mechanical strength, heat capacity, and thermal conductivity of the filler. Thicker walls result in higher mechanical strength and stronger heat storage capacity, but also increase weight and thermal resistance.
Open Porosity: The percentage of the open area of all channels to the total cross-sectional area. It directly reflects the smoothness of airflow (or liquid flow) through the honeycomb structure. Higher open porosity results in lower fluid resistance (pressure drop) and stronger throughput.
Interrelationships Among the Three
There is a rigid geometric relationship between these three parameters across the cross-section of the honeycomb ceramic. For a standard square-cell honeycomb structure, the mathematical relationship can be simplified to:
Aperture ratio ≈ (pore diameter)² / (pore diameter + wall thickness)²
Since pore density is directly proportional to 1 / (pore diameter + wall thickness)², we can draw a crucial conclusion: given the material and molding process, the aperture ratio is a function of pore density and wall thickness. When pursuing higher pore density, to maintain a constant aperture ratio, the wall thickness must be reduced; conversely, to increase wall thickness to improve strength, either a decrease in aperture ratio or a reduction in pore density must be accepted. This relationship constitutes the core contradiction in honeycomb ceramic design.
Typical Application Scenarios
Application Scenarios | Core Performance Requirements | Typical Parameter Balancing Strategies |
Automotive Exhaust Catalyst Carrier | Low pressure drop (ensuring power), high specific surface area (enhancing catalytic activity), rapid ignition | Ultra-high pore density + ultra-thin wall thickness |
Diesel Particulate Filter | High collection efficiency, low back pressure, high strength (thermal shock resistance) | Medium pore density + moderate wall thickness, often using silicon carbide |
RTO Heat Regenerator | High heat capacity (energy saving), high strength (thermal shock resistance), low resistance | Medium-low pore density + relatively thick wall thickness, often using cordierite/mullite |
Industrial Catalysis (e.g., SCR) | High specific surface area, certain strength, wear resistance | Medium pore density and wall thickness, seeking the optimal balance |
Summary
The constraints between pore density, wall thickness, and open porosity are the starting point and optimization space for engineering design. Successful honeycomb ceramic products achieve breakthroughs based on a deep understanding of the relationship between these three factors. Therefore, the ability to understand and master these three parameters directly reflects the core technological level of a cellar ceramic manufacturer. The best design is always the optimal solution tailored to the target application under stringent geometric constraints, rather than simply pursuing the limit of a single parameter. We are a Chinese cellar ceramic manufacturer. For more information, please contact us via email at annayu@169chem.net or WhatsApp at +8618909016373.