Gas Sensor Element Porous Protective Layer Thermal Shock
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas sensors with sensor elements exposed to high temperatures are prone to cracking due to rapid cooling when moisture adheres to their surfaces, which compromises their moisture resistance.
Innovation Solution
A sensor element design featuring an elongate rectangular parallelepiped shape with solid electrolyte layers and a protective layer that includes exposed spaces to block heat conduction, allowing for controlled cooling and reducing the risk of cracking by maintaining a stable temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed on the sensor element surface, then moisture resistance is improved, but heat dissipation is enhanced causing rapid cooling and cracking
Solution Approach 1:
The protective layer is designed with a porous structure containing multiple spaces, allowing it to maintain moisture resistance while reducing heat conduction. The pores trap air which acts as a thermal insulator, preventing rapid heat dissipation from the sensor element when moisture adheres to the surface.
Solution Approach 2:
The spaces within the protective layer act as pre-established thermal buffers that cushion against rapid temperature changes. When moisture adheres to the outer surface, the air-filled spaces prevent direct thermal contact between the moisture and the sensor element, cushioning the element from abrupt cooling.
2Strength
If the protective layer is made dense to improve strength, then cracking resistance improves, but heat conduction increases causing rapid cooling
Solution Approach 1:
The protective layer utilizes a porous structure where air-filled spaces provide thermal insulation. The porous architecture maintains structural integrity while the trapped air prevents efficient heat conduction, thereby reducing the cooling rate when moisture is present on the surface.
Solution Approach 2:
The protective layer functions as a composite structure combining the solid protective material with air-filled spaces. This composite architecture provides both mechanical strength from the solid matrix and thermal insulation from the air pockets, achieving a balance between cracking resistance and cooling rate control.
3Measurement precision
If the sensor element operates at high temperature, then detection performance improves, but susceptibility to moisture-induced cracking increases
Solution Approach 1:
The protective layer with its porous structure serves as an intermediary between the high-temperature sensor element and the moisture in the environment. It allows the element to maintain high operating temperature for optimal detection performance while the air-filled pores mediate thermal interactions, reducing the element's susceptibility to moisture-induced thermal shock and cracking.
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 design enhances the moisture resistance of the sensor element by preventing abrupt temperature drops and reducing stress from thermal expansion differences, thereby minimizing the risk of cracking and improving overall performance.
Implementation Method 1
heat conduction in a direction of thickness of the protective layer can be blocked off
Implementation Method 2
cooling of the element body is suppressed when moisture adheres to the surface of the protective layer
Data Source
AI summary
A sensor element includes an element body having an elongate rectangular parallelepiped shape and including solid electrolyte layers with oxygen ion conductivity, an outer pump electrode disposed on a first surface of the element body, and a protective layer covering at least a part of a second surface of the element body on a side opposite to the first surface and including one or more exposed spaces (a lower space) to which the second surface is exposed.