Base-Metal Detecting Electrode with Passivation Film
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Solution Overview
Problem
Platinum-based detecting electrodes in exhaust gas sensors catalytically decompose soot particulates, leading to inaccurate detection due to dispersed particles, resulting in a lower measured content than actual.
Innovation Solution
A sensor board with a detecting electrode formed from a catalytically inactive base-metal material, such as iron, aluminum, or nickel, coated with a passivation film to prevent oxidation and decomposition of soot particulates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If platinum is used as the detecting electrode material, then the electrode is resistant to oxidation at high temperatures, but the platinum catalytically decomposes soot particulates leading to detection inaccuracy
Solution Approach 1:
The patent extracts and removes platinum from the detecting electrode material composition, replacing it with base-metal based materials that lack catalytic activity toward soot decomposition. This extraction eliminates the harmful catalytic effect while maintaining the electrode's structural integrity and oxidation resistance through alternative material selection.
Solution Approach 2:
The patent employs base-metal based materials that are less expensive and sufficiently durable for the application, replacing expensive platinum. These materials achieve the required service life without exhibiting the harmful catalytic properties of platinum, thereby resolving both the cost and performance issues.
2Stability of the object's composition
If platinum is used in the detecting electrode, then the electrode maintains structural stability at high temperatures, but the catalytic action causes soot particulates to decompose and disperse
Solution Approach 1:
The patent converts the situation by selecting materials that inherently lack the harmful catalytic property. Instead of trying to eliminate catalysis from platinum, the solution uses base-metal based materials where catalytic decomposition of soot does not occur, thereby transforming a harmful effect into a beneficial non-reactive state that preserves soot integrity for accurate detection.
3Measurement precision
If the detecting electrode is made of base-metal based material, then catalytic decomposition of soot is prevented, but the electrode surface is prone to oxidation
Solution Approach 1:
The patent introduces an intermediary protective layer or surface treatment on the base-metal based electrode that prevents direct oxidation while allowing the underlying material to maintain its catalytically inactive properties. This intermediary layer protects the electrode surface from oxidation harm while preserving the beneficial non-catalytic characteristics for accurate soot detection.
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 ensures high accuracy in detecting soot content by preventing catalytic decomposition and oxidation, maintaining the integrity of the detected particles on the electrode, thereby enhancing detection reliability and precision.
Implementation Method 1
an exposed surface of the detecting electrode being covered by a passivation film of the first metallic material
Implementation Method 2
in association with adhesion of a to-be-detected substance contained in the exhaust gas to the detecting electrode
Data Source
AI summary
A sensor board includes: an insulating substrate having a principal surface; and a detecting electrode disposed on the principal surface of the insulating substrate, the detecting electrode being formed mainly of a first metallic material composed of a base-metal based material which is catalytically inactive with respect to a decomposition reaction of particulates, an exposed surface of the detecting electrode being covered by a passivation film of the first metallic material.