Prismatic Gas Sensor Alumina Coating Soot Prevention
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Solution Overview
Problem
Carbon or soot accumulation on the lateral surfaces of prismatic multilayer ceramic gas sensor elements causes deoxidization of the zirconia solid electrolyte layer, leading to reduced insulation resistance, malfunctioning gas sensing mechanisms, and weakened mechanical strength due to brittleness.
Innovation Solution
A prismatic multilayer gas sensor element with a non-porous alumina layer coating on the lateral surfaces of the posterior lead portion, featuring a multilayer structure to prevent carbon intrusion, and a ceramic heater to maintain the gas sensing cell portion at a temperature above 600°C for effective soot burning, while keeping the posterior lead portion below 600°C to prevent deoxidization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the gas sensor element is operated at high temperature to burn off carbon soot, then the gas sensing cell portion can maintain clean surfaces, but the posterior lead portion experiences deoxidization of the solid electrolyte layer
Solution Approach 1:
The gas sensor element is divided into two distinct temperature zones: the gas sensing cell portion is heated to high temperature (above 600°C) to burn off carbon soot, while the posterior lead portion is maintained at lower temperature (below 600°C) to prevent deoxidization of the solid electrolyte layer. This spatial segmentation of temperature control resolves the contradiction between soot removal and composition stability.
Solution Approach 2:
Different thermal conditions are applied to different parts of the gas sensor element. The gas sensing cell portion receives high temperature treatment for soot combustion, while the posterior lead portion receives low temperature treatment to preserve the oxidation state of the solid electrolyte layer. This local differentiation of thermal quality enables simultaneous achievement of both cleaning and composition protection.
2Ease of manufacture
If a single insulating layer is applied to protect the solid electrolyte layer, then the manufacturing process is simple, but carbon soot can penetrate through the layer
Solution Approach 1:
A multilayer coating structure is implemented where multiple insulating layers are nested on the lateral surfaces of the gas sensor element. Each layer provides additional barrier function against carbon soot penetration. The nested multilayer structure enhances protection effectiveness while maintaining manufacturing feasibility through sequential coating processes.
Solution Approach 2:
The insulating protective layer is constructed as a composite multilayer structure combining different insulating materials or configurations. This composite approach provides superior resistance to carbon soot penetration compared to single-layer structures, while the layered architecture allows for optimized manufacturing processes for each individual layer.
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 deoxidization of the zirconia solid electrolyte layer, ensuring accurate gas measurement over a long period by maintaining insulation resistance and mechanical integrity, and preventing carbon accumulation on the sensor surfaces.
Implementation Method 1
a heating resistor (12a) sandwiched by insulating layers (7, 10) and positioned in the vicinity of the gas-sensing portion (2) so as to heat the gas-sensing portion (2) to a temperature of more than 600° C.
Implementation Method 2
the temperature of the gas-sensing cell portion is elevated to a temperature that is high enough to burn off carbon-like soot
Implementation Method 3
longitudinal lateral surfaces of the posterior lead portion (3), which lateral surfaces are substantially perpendicular to top and bottom planer surfaces of the prismatic multilayer gas sensor element (1), and which lateral surfaces are heated by the heating resistor (12a) to a temperature not exceeding 600° C., are each coated with a third non-porous alumina layer (11)
Data Source
AI summary
A prismatic multilayer gas sensor element and method of making the same, the prismatic multilayer gas sensor element (1) having a substantially rectangular cross section, and including a gas-sensing cell portion (2) formed at a distal end portion of the prismatic gas sensor element (1); and a posterior lead portion (3) adjoining the gas-sensing cell portion (2). The longitudinal lateral surfaces of the posterior lead portion (3) are coated with a non-porous alumina layer (11), the non-porous alumina layer (11) having a multilayered structure including at least a joining layer (11a) and a surface layer (11b). The longitudinal lateral surface of the gas-sensing portion (2) is not coated with a non-porous alumina layer.