Silicon Carbide Honeycomb Structure Nitrogen Layer Resistivity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional honeycomb structures for exhaust gas treatment face challenges in maintaining appropriate electrical resistivity across varying temperatures, leading to difficulties in proper heating due to temperature-dependent changes in electrical resistivity.
Innovation Solution
A honeycomb structure with a nitrogen-containing layer on the surfaces of silicon carbide particles, where the nitrogen atoms are concentrated to control temperature dependence of electrical resistivity, and optionally a silica layer is added for protection, formed through specific firing and heat treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a honeycomb structure has low electrical resistivity at room temperature, then it can be heated effectively, but the electrical resistivity decreases sharply with temperature increase, causing heating problems at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the honeycomb structure by incorporating specific metal elements (Fe, Co, Ni, Cu, or Mn) at controlled concentrations (0.1-5 wt%). This compositional modification alters the electrical resistivity-temperature relationship, enabling the structure to maintain appropriate resistivity across a wide temperature range (room temperature to 500°C) for reliable heating performance
Solution Approach 2:
The patent creates a composite material system by combining silicon carbide-based honeycomb structure with specific metal elements. This composite approach allows the material to exhibit optimized electrical properties that balance low resistivity at room temperature with stable resistivity at elevated temperatures, resolving the contradiction between heating effectiveness and temperature stability
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 controls temperature dependence of electrical resistivity, ensuring consistent heating performance across a wide temperature range and maintaining long-term stability, thereby addressing the heating challenges faced by conventional structures.
Implementation Method 1
a nitrogen-containing layer having a thickness in a range of 100 nm to 600 nm is formed on surfaces of the silicon carbide particles... the temperature change dependence of electrical resistivity is controlled
Implementation Method 2
by supplying the honeycomb structure with electric current via a pair of electrodes, it is possible to subject the honeycomb structure to resistance heating
Implementation Method 3
obtaining a honeycomb fired body by firing the honeycomb molded body for 1 hour to 5 hours at 2000°C to 2200°C in an inert atmosphere containing no nitrogen
Implementation Method 4
heating the honeycomb fired body for 2 hours to 8 hours at a temperature in a range of 1800°C to 2200°C in an environment containing nitrogen
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A honeycomb structure includes a pillar-shaped honeycomb unit having cells defined by cell walls. The cell walls contain silicon carbide particles, and a nitrogen-containing layer is formed on surfaces of the silicon carbide particles.