Honeycomb Structure Bonding Layer Pore Distribution
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Solution Overview
Problem
Conventional honeycomb structures experience an increase in Young's modulus and strength after heat treatment, leading to reduced durability and inability to relax thermal stress, which compromises their functionality in engine drive environments.
Innovation Solution
A honeycomb structure with a bonding layer containing crystalline anisotropic ceramic, featuring a specific pore distribution and porosity, maintains strength and Young's modulus without significant increase after heat treatment, achieved through a manufacturing method involving a bonding slurry with controlled particle sizes and ceramic content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bonding layer is subjected to heat treatment to improve strength, then the strength increases, but the Young's modulus also increases significantly, causing the bonding layer to lose its ability to relax thermal stress
Solution Approach 1:
The bonding layer is designed with a controlled porous structure containing fine pores (10-50 μm) and coarse pores (50-300 μm) in specific volume ratios. This porous structure allows the bonding layer to maintain low Young's modulus even after heat treatment, while achieving sufficient strength through the crystalline anisotropic ceramic content and pore distribution configuration.
Solution Approach 2:
The bonding layer uses a composite material system comprising crystalline anisotropic ceramic particles embedded in a bonding matrix. This composite structure enables the bonding layer to achieve both high strength (through the ceramic reinforcement) and low Young's modulus (through the matrix and pore structure), maintaining thermal stress relaxation capability after heat treatment.
2Reliability
If the bonding layer has high strength after heat treatment, then durability improves, but the ability to relax thermal stress in engine drive environment is compromised
Solution Approach 1:
The bonding layer parameters are precisely controlled: porosity is maintained at 60-70%, fine pore volume is set at 0.15-0.4 cc/g, coarse pore volume at 0.05-0.25 cc/g, and crystalline anisotropic ceramic content is optimized. These parameter configurations enable the bonding layer to achieve both durability and thermal stress relaxation capability after heat treatment.
3Stability of the object's composition
If the pore volume of fine pores is increased to maintain low Young's modulus, then thermal stress relaxation improves, but bonding strength may be reduced
Solution Approach 1:
The pore structure is segmented into two distinct size categories: fine pores (10-50 μm) and coarse pores (50-300 μm), each serving different functions. Fine pores primarily control Young's modulus and thermal stress relaxation, while coarse pores provide structural support and crack propagation resistance. This segmentation allows independent optimization of both strength and flexibility.
Solution Approach 2:
Different pore sizes are distributed throughout the bonding layer to create local functional zones. The fine pores are distributed to maintain overall low Young's modulus, while the coarse pores are positioned to provide localized strength enhancement and crack arrest, achieving both flexibility and strength simultaneously.
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 honeycomb structure maintains low Young's modulus and sufficient shear strength after heat treatment, ensuring durability and effective thermal stress relaxation, thereby preventing structural breakdown.
Implementation Method 1
the bonding layer has a difficulty of performing an originally required function of relaxing a thermal stress in an engine drive environment
Implementation Method 2
after being heated at 600° C. for 30 minutes, and has a Young's modulus of 120 MPa or less after being heated at 900° C. for 300 minutes
Data Source
AI summary
A honeycomb structure includes honeycomb segments each having a porous partition wall defining a plurality of cells, and includes a porous bonding layer containing a crystalline anisotropic ceramic and disposed so as to bond side surfaces of the honeycomb segments to each other. A ratio of a pore volume (cc/g) of a fine pore defined as a pore in the bonding layer having a pore diameter of 10 μm or more and less than 50 μm with respect to a pore volume (cc/g) of a coarse pore defined as a pore in the bonding layer having a pore diameter of 50 μm or more and 300 μm or less is from 2.0 to 3.5, the pore volume of the fine pore is from 0.15 to 0.4 cc/g, and the pore volume of the coarse pore is from 0.05 to 0.25 cc/g.