Gas Sensor Electrode Porous Structure Optimization
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Solution Overview
Problem
Conventional gas sensor electrodes formed by metal pastes with a core/shell structure exhibit insufficient electrode activity due to a lack of three-phase boundaries and excessive resistance, which hampers their performance in detecting gases effectively.
Innovation Solution
A gas sensor electrode with a porous structure and finely dispersed conductive and ceramic particles, achieved by adjusting the particle diameters of conductive particles with a core/shell structure and incorporating ceramic powder to create a void ratio and dispersion state that optimizes reaction fields and conductivity, while minimizing the use of precious metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic powder is mixed into metal paste to correct shrinkage rate difference and improve adhering property, then formation property of electrode film is ensured, but resistance value of electrode film increases to higher level than bulk metal electrode
Solution Approach 1:
The patent applies a porous structure to the electrode film, allowing ceramic particles to be dispersed within the metal matrix while maintaining interconnected void spaces. This porous configuration reduces the tortuosity of electron pathways and minimizes the blocking effect of ceramic particles, thereby maintaining low resistance while ensuring good adhering property and formation property through the ceramic component.
2Ease of manufacture
If ceramic powder is added to metal paste to ensure formation property, then electrode can be produced simultaneously with substrate, but resistance value increases and requires optimization of mixing amounts
Solution Approach 1:
The patent optimizes the particle size distribution of ceramic powder and its mixing ratio with metal particles. By controlling the size parameters of ceramic particles and their concentration in the metal paste, the invention achieves a balance where sufficient ceramic content ensures formation property and simultaneous production capability, while the optimized particle size and distribution prevent excessive resistance increase.
3Object-affected harmful factors
If core/shell structure with ceramic particles covering precious metal core is used to disperse ceramic finely during firing, then electrode becomes closely packed and resistance is reduced, but electrode activity is insufficient due to lack of three-phase boundaries
Solution Approach 1:
The patent transitions from a fully dense closely-packed structure to a controlled porous structure. By incorporating porosity into the electrode film, three-phase boundaries (metal-ceramic-gas interfaces) are created and distributed throughout the electrode. These porous pathways allow gas diffusion and reaction sites while maintaining electrical connectivity through the metal phase, thus achieving both low resistance and high electrode activity.
Solution Approach 2:
The patent employs a composite material structure combining conductive metal particles, ceramic particles, and a porous matrix. This composite configuration allows the metal phase to provide electrical conductivity (low resistance) while the porous structure with ceramic components creates numerous three-phase boundaries for electrochemical reactions (high electrode activity).
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 results in a gas sensor electrode with low resistance and high activity, allowing for thin film formation and reduced precious metal usage, thereby enhancing the performance and cost-effectiveness of gas sensors.
Implementation Method 1
with the conductive particle having the core/shell structure, ceramic particles are dispersed finely during the step of firing the metal paste
Implementation Method 2
A gas sensor electrode with a porous structure and finely dispersed conductive and ceramic particles, achieved by adjusting the particle diameters of conductive particles with a core/shell structure and incorporating ceramic powder to create a void ratio and dispersion state that optimizes reaction fields
Data Source
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AI summary
A gas sensor electrode including a conductive particle phase made of Pt or Pt alloy and a ceramic particle phase being mixed and dispersed, wherein a rate of content of the ceramic particle phase is 6.0 to 22.0 mass%, and a void ratio is 2.5 to 10.0%, and a dispersion degree of the conductive particle phase per length of 25 µm on the electrode surface is 0.60 to 0.85 µm, and a dispersion degree of the conductive particle phase in the electrode cross section per length of 100 µm in a direction parallel to the electrode surface is 2.0 to 4.0 µm.