Oxide-Bonded SiC Honeycomb Structure for High-Temperature Exhaust
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Solution Overview
Problem
The existing honeycomb structures used as filters and catalyst carriers for purifying vehicle exhaust gas face issues of insufficient wettability between silicon carbide and metallic silicon, leading to low strength and thermal conductivity, and are prone to damage under high-temperature conditions.
Innovation Solution
A honeycomb structure with a porous body partition wall composed of refractory aggregates bonded by an oxide material, where the bonding material occupies 20-35% of the mass proportion, and refractory aggregates with diameters of 5 µm or more are densely packed, enhancing strength and thermal conductivity while reducing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silicon carbide and metallic silicon are used as aggregate materials in honeycomb structure, then the structure can be formed with refractory particles, but the wettability between silicon carbide and metallic silicon is insufficient, resulting in low strength
Solution Approach 1:
An oxide material is introduced as an intermediary bonding agent between silicon carbide and metallic silicon aggregates. The oxide material forms a bonding network that connects the aggregate particles, improving the overall wettability and interfacial adhesion within the honeycomb structure, thereby enhancing strength without requiring direct contact between incompatible silicon carbide and metallic silicon surfaces.
Solution Approach 2:
The honeycomb structure employs a composite material system consisting of silicon carbide aggregates, metallic silicon aggregates, and oxide bonding material. This multi-phase composite approach allows each component to contribute its unique properties: silicon carbide provides refractory stability, metallic silicon provides thermal conductivity, and the oxide material provides bonding capability, collectively achieving high strength through synergistic combination.
2Temperature
If silicon carbide and metallic silicon are used as aggregate materials, then the honeycomb structure can be formed, but the thermal conductivity is insufficient, generating large temperature gradients at high temperatures
Solution Approach 1:
The oxide bonding material is strategically positioned at the interfaces between aggregates and in the interstices of the honeycomb structure, creating local regions of enhanced thermal management. This localized distribution of bonding material facilitates heat transfer pathways while maintaining structural integrity, addressing thermal conductivity issues at critical interfaces without compromising overall strength.
3Reliability
If the wettability between silicon carbide and metallic silicon is improved by adding alkaline earth metal assistant, then the interface area increases, but the improvement is limited to material bonding only, failing to achieve sufficient effect
Solution Approach 1:
The invention changes the fundamental parameter of bonding mechanism from direct aggregate-to-aggregate contact to aggregate-to-bonding-material-to-aggregate indirect bonding. By introducing the oxide material as an intermediate phase, the system transforms the bonding interface characteristics, enabling improved wettability and adhesion that extends beyond limited direct contact zones to create a comprehensive bonding network throughout the honeycomb structure.
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 achieves high strength and thermal conductivity, is less likely to be damaged under high-temperature conditions, and exhibits low pressure loss, making it suitable for use in high-temperature environments as both a filter and catalyst carrier.
Implementation Method 1
the improvement of the above-described wettability increases an interface area between the silicon carbide and the metallic silicon
Implementation Method 2
high thermal conductivity of materials constituting the honeycomb structure are ensured
Data Source
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AI summary
There is provided a honeycomb structure that has high strength and high thermal conductivity. Further, the honeycomb structure is made of a material that is less likely to be damaged even for usage under high-temperature environment. A honeycomb structure 100 includes a honeycomb structure body 4 that has a partition wall 1. The partition wall 1 is constituted of a porous body. The porous body includes a refractory aggregate and a bonding material. The bonding material has a main constituent of an oxide material. The porous body constituting the partition wall 1 includes the bonding material at a mass proportion of 20 to 35 mass %. In an observation of a cross section of the partition wall 1 with an electron microscope, when observing any given ten visual fields meeting a following condition (1), the number of refractory aggregates meeting a following condition (2) is five pieces or more in all of the ten visual fields. Condition (1): the visual field is 100 µm square, and in the visual field, a proportion of an area occupied by the bonding material to a total area of the refractory aggregate and the bonding material in the visual field is 30% or more. Condition (2) : the refractory aggregate has a particle diameter of 5 µm or more, and 60% or more of an outer circumference of the refractory aggregate is surrounded by the bonding material.