Composite Sintered Body for Electrically Heated Catalyst
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Solution Overview
Problem
The existing honeycomb structures used in electrically heated catalysts for exhaust gas purification have high thermal expansion coefficients, high volume resistivity, and low strength, which makes them unsuitable for high-temperature oxidation environments, leading to reduced performance and dimensional inaccuracies.
Innovation Solution
A composite sintered body composed of a silicon phase, cordierite phase, and an amorphous phase with controlled peak intensity ratios and porosity, along with a mullite phase, is developed, which provides low resistance and high oxidation resistance, formed through a specific manufacturing process involving sintering and oxidation treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a honeycomb structure contains metals and silicide to achieve high thermal expansion coefficient, then thermal expansion resistance is improved, but volume resistivity increases and strength decreases
Solution Approach 1:
The patent uses a composite material system consisting of silicon particles (50-90 mass%), silicon carbide particles (5-40 mass%), and borosilicate glass (1-20 mass%). This composite structure achieves appropriate thermal expansion resistance through the combination of materials with different thermal properties, while maintaining low volume resistivity through the conductive silicon and silicon carbide phases, and sufficient strength through the interconnected particle network bound by glass.
Solution Approach 2:
The patent controls the particle size parameters of silicon particles (D10: 0.5-5 μm, D50: 2-10 μm, D90: 5-20 μm) and silicon carbide particles (D10: 0.5-5 μm, D50: 2-10 μm, D90: 5-20 μm) to optimize the balance between thermal expansion resistance, electrical conductivity, and mechanical strength. The specific particle size distribution affects packing density, contact points for electrical conduction, and overall structural integrity.
2Temperature
If porosity is increased to reduce heat capacity and increase thermal diffusivity, then thermal response speed is improved, but volume resistivity increases and strength decreases
Solution Approach 1:
The patent employs a controlled porous structure with porosity of 30-50% to achieve rapid thermal response. The pores are distributed throughout the honeycomb structure to reduce heat capacity and increase thermal diffusivity, enabling quick temperature changes for effective exhaust gas heating. The porous structure is maintained while ensuring sufficient mechanical strength through the particle-glass matrix framework.
Solution Approach 2:
The composite of silicon particles, silicon carbide particles, and borosilicate glass creates a matrix that can accommodate porosity while maintaining structural integrity. The glass phase binds the particles together in the porous structure, preventing collapse and maintaining electrical conductivity pathways even with 30-50% porosity.
3Reliability
If surface bonding of silicon particles is performed to reduce electric resistance, then electrical conductivity is improved, but oxidation resistance decreases in high temperature atmosphere
Solution Approach 1:
The borosilicate glass (1-20 mass%) acts as an intermediary phase that bonds silicon particles together while providing oxidation protection. The glass forms a protective matrix around the silicon particles, preventing direct oxidation of silicon surfaces at high temperatures, while still allowing electrical conductivity through the silicon particle network.
Solution Approach 2:
The patent controls the particle size parameters of silicon particles (D10: 0.5-5 μm, D50: 2-10 μm, D90: 5-20 μm) to optimize the balance between electrical conductivity and oxidation resistance. Smaller particles provide more contact points for conduction but greater surface area for oxidation, so the specified range achieves the optimal balance.
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 composite sintered body achieves a balanced low resistance and high oxidation resistance, ensuring efficient heat generation and prolonged catalyst performance in high-temperature conditions while maintaining dimensional accuracy.
Implementation Method 1
a conductive catalytic converter is connected to a pair of electrodes and causes itself to generate heat by energization
Implementation Method 2
obtaining a sintered body by molding and sintering raw material powder containing a silicon raw material and a cordierite raw material
Implementation Method 3
obtaining a composite sintered body by performing an oxidation treatment on the sintered body
Data Source
AI summary
A composite sintered body contains a silicon phase which is a main phase, a cordierite phase, and an amorphous phase containing Si. Further, the volume resistivity thereof at a room temperature is not lower than 0.1 Ω·cm and not higher than 2.5 Ω·cm.