SiC Honeycomb Structure with Resistivity Gradient for Uniform Heating
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Solution Overview
Problem
Conventional honeycomb structures used as catalyst carriers and heaters face issues with uneven temperature distribution and mechanical strength due to high voltage usage, excessive current flow, and difficulty in loading catalysts, particularly when made of metal and having high electrical resistance.
Innovation Solution
A honeycomb structure made of silicon carbide with a designed electrical resistivity gradient, where the outer peripheral region has a lower resistivity than the central region, allowing even current flow and heat generation, and a manufacturing method involving silicon-based particles to create this resistivity gradient, ensuring uniform heating and mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heater is used in a honeycomb structure, then heating function is improved, but electrical resistance is too low causing excessive current flow and power source circuit damage
Solution Approach 1:
The invention changes the electrical resistance parameter of the heating element by using a ceramic material with controlled resistivity (10^-5 to 10^-3 Ω·m) instead of metal, and further optimizes the current path length parameter to achieve appropriate electrical resistance and prevent excessive current flow
Solution Approach 2:
The invention uses a composite structure combining ceramic heating element with conductive material (such as platinum or conductive ceramic) for electrodes, creating a material system that provides both heating function and appropriate electrical resistance characteristics
2Temperature
If a metal heater is used in a honeycomb structure, then heating function is improved, but catalyst loading becomes difficult
Solution Approach 1:
The invention changes the material parameter from metal to ceramic, which provides surface properties more suitable for catalyst loading and integration, allowing catalyst to be easily applied onto the heating element surface
Solution Approach 2:
The invention merges the heater and catalyst carrier into a single integrated component, where the ceramic heating element serves dual purposes as both heat source and catalyst support, eliminating the need for separate metal heater and catalyst loading
3Temperature
If current flows from terminals to electrodes in conventional honeycomb structure, then heating is achieved, but temperature distribution becomes uneven
Solution Approach 1:
The invention applies local quality by creating a controlled electrical resistivity gradient within the ceramic heating element, where the resistivity varies spatially to ensure uniform current density and temperature distribution throughout the honeycomb structure
Solution Approach 2:
The invention changes the electrical resistivity parameter distribution within the heating element to optimize current flow patterns, ensuring that current distributes evenly across the structure rather than concentrating at electrode ends
4Manufacturing precision
If partition wall thickness is adjusted to achieve even heating, then temperature distribution improves, but mechanical strength deteriorates due to formation of brittle portions
Solution Approach 1:
The invention changes the material parameter from metal to ceramic with controlled electrical resistivity, which allows achieving even temperature distribution through electrical resistance heating without requiring partition wall thickness adjustments that would compromise mechanical strength
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 solution effectively inhibits uneven temperature distribution and enhances mechanical strength, allowing for efficient heat generation and catalyst loading, while preventing excessive current flow and maintaining structural integrity under high voltage conditions.
Implementation Method 1
a power source for use in an electric system of the car is used in common, for example, a power source of as high voltage as 200 V is used. However, the heater made of the metal has a low electric resistance. Therefore, when the power source of such a high voltage is used, a current excessively flows
Implementation Method 2
A honeycomb structure made of silicon carbide with a designed electrical resistivity gradient, where the outer peripheral region has a lower resistivity than the central region, allowing even current flow and heat generation
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
There is disclosed a honeycomb structure which is a catalyst carrier and also functions as a heater when a voltage is applied thereto and which can inhibit an unevenness of a temperature distribution when the voltage is applied thereto. A honeycomb structure 100 includes a tubular honeycomb structure body 4 having porous partition walls 1 to define and form a plurality of cells 2 and an outer peripheral wall 3, and a pair of electrodes 21 disposed on a side surface 5 of the honeycomb structure body 4. An electrical resistivity of the honeycomb structure body 4 is from 1 to 200 Ωcm, each of the pair of electrodes 21 is formed into a band-like shape extending in an extending direction of the cells 2 of the honeycomb structure body 4, one electrode 21 in the pair of electrodes 21 is disposed on a side opposite to the other electrode 21 in the pair of electrodes 21 via a center of the honeycomb structure body 4, the honeycomb structure body 4 is constituted of an outer peripheral region 6 and a central region 7, and an electrical resistivity of a material constituting the outer peripheral region 7 is lower than an electrical resistivity of a material constituting the central region 6.