Honeycomb Structure Electrode Members Boron Silicon Composite
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Solution Overview
Problem
Existing honeycomb structures used as catalyst carriers and heaters face issues with electrode member durability and thermal shock resistance, particularly due to local oxidation and increased resistance when subjected to periodic thermal loads, leading to potential peeling and deterioration.
Innovation Solution
A honeycomb structure with pillar-shaped body and electrode members made of silicon carbide containing metal silicon and boron, where the electrode members have a composite material with a high volume ratio of boron, low electric resistivity, and specific thermal expansion coefficients, along with a conductive intermediate layer, to enhance energization durability and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrode members are made of conventional materials (Ni-Cr alloy, Si, oxide minerals) and formed by thermal spraying, then the honeycomb structure can function as a heater, but the electrode members suffer from local oxidation and increased resistance under periodic thermal loads
Solution Approach 1:
The electrode member is constructed as a composite material comprising metal silicon (5-50 mass%), boron (0.1-5 mass%), and a binder (5-50 mass%). This composite structure provides both excellent electrical conductivity for heat generation and superior oxidation resistance, particularly at high temperatures. The boron component forms protective boride layers that prevent oxidation of the silicon, while the binder matrix holds the structure together and provides mechanical strength.
Solution Approach 2:
The invention changes the chemical composition parameters of the electrode material by incorporating specific amounts of boron (0.1-5 mass%) alongside metal silicon. This compositional parameter change fundamentally alters the material's oxidation behavior, creating a surface layer that resists oxidation even under periodic thermal cycling conditions. The specific ratio of silicon to boron is optimized to balance conductivity and oxidation resistance.
2Power
If electrode members contain high比例的 metal silicon for low resistance, then heat generation efficiency improves, but oxidation resistance deteriorates under thermal loads
Solution Approach 1:
Boron acts as an intermediary element that protects the highly reactive metal silicon from direct oxidation. When exposed to oxygen, boron preferentially reacts to form stable boride layers (such as SiB6 or B2O3) on the surface, creating a protective barrier that prevents oxygen from attacking the silicon. This intermediary mechanism allows the electrode to maintain low resistance through high silicon content while achieving oxidation resistance through the boron protective layer.
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 structure effectively prevents electrode member peeling and deterioration under thermal loads, maintaining low electric resistivity and improved oxidation resistance, ensuring efficient heat generation and prolonged service life.
Implementation Method 1
Such a honeycomb structure generates heat due to Joule heat when a current is passed through the honeycomb structure
Data Source
AI summary
The honeycomb structure includes a pillar-shaped honeycomb structure body having porous partition walls 1 defining a plurality of cells and a circumferential wall, and a pair of electrode members disposed on the side of a side surface of the honeycomb structure body. The pair of electrode members contain metal silicon and boron, at least a part of the electrode member is made of a composite material including, as a main component, silicon containing 100 to 10000 ppm of boron in silicon. In the composite material which is comprised the electrode member, a volume ratio of the silicon containing 100 to 10000 ppm of the boron in the composite material is 70 volume % or more. An electric resistivity of the electrode member made of the composite material is from 20 μΩcm to 0.1 Ωcm.