Gas Sensor Electrode Pore Size Ratio for Poisoning Resistance
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Solution Overview
Problem
Conventional gas sensor elements face reduced sensitivity and pore clogging due to poisoning substances, especially when the gas contains water, as the measurement electrode protective layer struggles to trap substances effectively, leading to deterioration and clogging of the measurement electrode.
Innovation Solution
A gas sensor element with a base member comprising laminated solid electrolyte layers and a porous measurement electrode covered by a measurement electrode protective layer, where the average pore size ratio between the measurement electrode and the protective layer satisfies 0.05≤B/A≤0.9, ensuring effective prevention of poisoning substance ingress and maintaining sensor durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the measurement electrode protective layer uses a larger pore size to allow gas diffusion, then the diffusion-controlled capability is improved, but the poisoning substance-containing solution can penetrate into the measurement electrode pores causing clogging and sensitivity reduction
Solution Approach 1:
The protective layer is divided into multiple layers with different pore sizes: a first protective layer with larger pores (0.5-5 μm) for gas diffusion and a second protective layer with smaller pores (0.01-0.5 μm) for trapping poisoning substances. This segmentation allows each layer to perform its specific function effectively.
Solution Approach 2:
Different regions of the protective structure have different pore size characteristics tailored to their specific functions. The first protective layer has larger pores optimized for gas permeability, while the second protective layer has smaller pores optimized for substance trapping, creating local quality variations that resolve the contradiction.
2Reliability
If the measurement electrode protective layer uses a smaller pore size to trap poisoning substances, then the trapping capability is improved, but the gas diffusion capability is reduced
Solution Approach 1:
The protective layer is divided into multiple layers with different pore sizes: a first protective layer with larger pores (0.5-5 μm) for gas diffusion and a second protective layer with smaller pores (0.01-0.5 μm) for trapping poisoning substances. This segmentation allows each layer to perform its specific function effectively.
Solution Approach 2:
Different regions of the protective structure have different pore size characteristics tailored to their specific functions. The first protective layer has larger pores optimized for gas permeability, while the second protective layer has smaller pores optimized for substance trapping, creating local quality variations that resolve the contradiction.
3Duration of action of stationary object
If the pore size of the measurement electrode is smaller to prevent clogging, then the durability is improved, but the capillary force increases causing solution penetration into the pores
Solution Approach 1:
The second protective layer with smaller pores is placed over the measurement electrode before the poisoning substance-containing solution can penetrate into the electrode pores. This preliminary protective barrier prevents the solution from reaching the measurement electrode, eliminating the capillary force problem.
Solution Approach 2:
The second protective layer acts as an intermediary barrier between the poisoning substance-containing solution and the measurement electrode. It intercepts the solution before it can enter the measurement electrode pores, preventing both clogging and capillary force effects.
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 prevents poisoning substance-induced deterioration and clogging, maintaining high sensor sensitivity and durability by optimizing the pore size ratio and porosity of the measurement electrode and protective layer, ensuring reliable gas component concentration measurement.
Implementation Method 1
The measurement electrode protective layer of such a gas sensor element traps an electrode poisoning substance contained in the gas to be measured so that the poisoning substance does not adhere to the measurement electrode
Implementation Method 2
the measurement electrode protective layer... functions as a diffusion-controlled section that limits the amount of a specific gas component (i.e., target gas component whose concentration is to be measured) contained in the gas to be measured that reaches the measurement electrode
Implementation Method 3
the poisoning substance-containing solution that has adhered to the measurement electrode protective layer reaches into the pores in the measurement electrode having smaller pore size due to a capillary force
Data Source
Figure 1
AI summary
A gas sensor element (100) includes a base member (101) comprising a plurality of laminated solid electrolyte layers, and having a space that communicates with the outside of the gas sensor element and allows introduction of the gas to be measured into the gas sensor element, and a porous measurement electrode (44) that is formed on a surface of the space inside the base member (101), and is covered with a porous measurement electrode protective layer (45), wherein an average pore size A of the measurement electrode (44) and an average pore size B of the measurement electrode protective layer (45) satisfy the relationship "0.05≤B/A≤0.9", the measurement electrode (44) has an average pore size of 0.5 to 15 µm, and the measurement electrode protective layer (45) has an average pore size of 0.05 to 9 µm, a porosity of 5 to 50%, and a thickness of 10 to 200 µm.