Honeycomb Structure with Conductive Bonding Layer for Uniform Heating
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Solution Overview
Problem
Existing honeycomb structures used as catalyst carriers for exhaust gas purification face challenges in achieving uniform heat generation and thermal shock resistance due to varying volume resistivities of segments and lack of elasticity in bonding layers, leading to potential breakdown of low-strength partition walls.
Innovation Solution
A honeycomb structure with tubular segments and a conductive bonding layer containing inorganic fibers, where the bonding layer has a volume resistivity between 2 to 2000 Ωcm and includes Al2O3-containing fibers with a mass ratio of 70% or more, providing thermal shock resistance and preventing breakdown under stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bonding layer is made non-conductive to prevent electrical shorting, then electrical insulation is improved, but heat generation uniformity deteriorates
Solution Approach 1:
The bonding layer uses silicon carbide particles (5-50 μm) with specific size ranges and controlled volume ratios (10-40 vol%) to achieve optimal electrical conductivity. This parameter control enables the bonding layer to conduct electricity uniformly while maintaining structural integrity, resolving the contradiction between insulation and heat uniformity.
Solution Approach 2:
The bonding layer is formulated as a composite material containing silicon carbide particles, silicon binder, and inorganic fibers. This composite structure provides both electrical conductivity (through silicon carbide) and mechanical strength (through silicon binder and fibers), allowing simultaneous achievement of heat generation uniformity and structural reliability.
2Stability of the object's composition
If the volume resistivity of honeycomb segments is varied to uniformize heat generation, then heat distribution is improved, but production complexity increases
Solution Approach 1:
Instead of varying the volume resistivity of each honeycomb segment individually, the invention applies local quality by concentrating conductivity control in the bonding layer. The bonding layer's controlled silicon carbide content creates localized conductive paths that uniformize heat generation across segments without requiring individual segment modification.
Solution Approach 2:
The bonding layer acts as an intermediary element between adjacent honeycomb segments. By controlling the electrical properties of this intermediate layer (through silicon carbide particle distribution), the invention achieves uniform heat generation across the entire structure without modifying the segments themselves, thereby simplifying production.
3Reliability
If the bonding layer has high elasticity to relax thermal stress, then thermal shock resistance is improved, but bonding strength decreases
Solution Approach 1:
The bonding layer is designed as a composite material combining silicon carbide particles, silicon binder, and inorganic fibers (alumina, silica, or zirconia). This composite structure provides both elasticity (through the flexible binder matrix) and high strength (through the rigid fiber reinforcement), simultaneously achieving thermal shock resistance and bonding strength.
Solution Approach 2:
The bonding layer incorporates a porous structure with controlled porosity (30-70%). The pores act as stress-absorbing voids that enhance thermal shock resistance by allowing thermal expansion without generating excessive stress, while the remaining solid matrix maintains sufficient bonding strength through the silicon carbide-silicon-inorganic fiber composite.
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 effectively functions as a heater by applying voltage, maintaining structural integrity under thermal stress and ensuring uniform heat distribution, enhancing thermal shock resistance and preventing bonding layer breakdown.
Implementation Method 1
a honeycomb structure capable of being used as a catalyst carrier, which also functions as a heater suitably by applying a voltage
Implementation Method 2
at least a part of the bonding layer is made of a bonding material having conductive property
Implementation Method 3
providing thermal shock resistance and preventing breakdown under stress
Implementation Method 4
when the elasticity of the bonding layer is lowered, the stress is relaxed
Data Source
AI summary
To provide a honeycomb structure capable of using as a catalyst carrier, which suitably functions as a heater by applying a voltage, and where a bonding layer is hard to break; and including a honeycomb segment bonded body where honeycomb segments are bonded by bonding layer, and a pair of electrode members disposed on side surface of the bonded body, wherein the electrode members is formed into a band shape, in a cross section perpendicular to the cell extending direction, the one electrode member is disposed on an opposite side across the center of the bonded body with respect to another electrode member, and in at least a part of the bonding layer, inorganic fibers made of an oxide are included in a porous body where particles of silicon carbide are bound with silicon in a state where pores are held among the particles.