Strain-Sensitive Element Using Metal-Ceramic Composite for High-Temperature Stability
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Solution Overview
Problem
Conventional strain gauge materials fail to maintain high-temperature stability and precise resistance measurements due to irreversible property changes and oxidation at elevated temperatures, and existing high-temperature strain gauges have high temperature coefficients of resistance (TCR) that are difficult to manage.
Innovation Solution
A strain-sensitive element composed of XAlOyN1-y thin films, where X is a high-melting-point metal like Ti, Ta, or Pt, with a controlled oxygen fraction to minimize TCR and maximize the K factor, applied using PVD or CVD processes, and integrated within a sealed sensor atmosphere to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain gauge materials (CrNi) are used, then the sensor can measure mechanical strain with high precision, but the materials show irreversible property changes and strong oxidation tendency at high temperatures
Solution Approach 1:
The patent uses composite materials consisting of metal particles (Pt, Pd, Ir, Rh, or Ru) dispersed in a ceramic matrix (SiO2, Al2O3, or ZrO2). This composite structure combines the electrical conductivity and strain sensitivity of metals with the high-temperature stability and oxidation resistance of ceramics, enabling the strain gauge to maintain both measurement precision and reliability at temperatures up to 700°C
Solution Approach 2:
The patent changes the material parameters by selecting specific metal types and ceramic matrix compositions, controlling particle size distribution, and adjusting the metal-to-ceramic ratio. These parameter changes optimize the balance between electrical properties (for strain measurement) and thermal stability (for high-temperature operation), achieving both high measurement precision and temperature stability
2Temperature
If high-melting-point metallic materials (Pt) are used, then the sensor can operate up to 700°C, but the temperature coefficient of electrical resistance (TCR) becomes very high requiring extremely precise temperature measurement
Solution Approach 1:
The patent employs composite materials where metal particles (Pt, Pd, Ir, Rh, or Ru) are dispersed in a ceramic matrix (SiO2, Al2O3, or ZrO2). The ceramic matrix provides a stable thermal background with low TCR, while the metal particles provide the necessary electrical conductivity and strain sensitivity. This composite structure significantly reduces the overall TCR compared to pure metals, enabling accurate resistance measurements at high temperatures without requiring extremely precise temperature compensation
Solution Approach 2:
The patent optimizes the concentration and size of metal particles within the ceramic matrix to achieve the desired electrical properties. By carefully controlling the metal particle content and distribution, the material achieves adequate electrical conductivity for strain measurement while maintaining a low temperature coefficient of resistance, thus resolving the contradiction between high-temperature operation and measurement accuracy
3Measurement precision
If Ni:a-C:H thin films are used, then the TCR is close to zero and K factor is high, but the films are only stable up to approximately 300°C
Solution Approach 1:
The patent replaces the organic Ni:a-C:H thin film material with an inorganic composite material consisting of metal particles in a ceramic matrix. This material substitution maintains the desirable electromechanical properties (low TCR and high K factor) while dramatically improving temperature stability, allowing operation up to 700°C. The ceramic matrix provides thermal stability whereas the metal particles provide the necessary piezoresistive effect
Solution Approach 2:
The patent changes the fundamental material composition from organic (Ni:a-C:H) to inorganic (metal-ceramic composite). This parameter change in material chemistry enables the sensor to maintain stable electromechanical properties at much higher temperatures, as the inorganic composite structure is inherently more thermally stable than organic thin films, while preserving the low TCR and high gauge factor through appropriate material selection and composition control
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 provides a strain-sensitive element with minimal TCR and high K factor, ensuring stable performance over extended high-temperature periods by controlling the oxygen fraction and using a nickel base material to bind residual oxygen, thereby maintaining precise resistance measurements.
Implementation Method 1
sensor element which includes a substrate having a strain-sensitive element preferably applied by means of thin-film technology, which element is used for measuring the deformation of the substrate when pressure is applied or a force is introduced
Implementation Method 2
The strain-sensitive element preferably consists of a composite layer which is applied with the PVD process (e.g. sputtering or vapour-deposition process) or CVD process
Implementation Method 3
The strain-sensitive element preferably consists of a composite layer which is applied with the PVD process (e.g. sputtering or vapour-deposition process) or CVD process
Data Source
AI summary
A sensor element (1) includes a substrate (2) and a strain-sensitive element (3) which is preferably applied to the substrate by means of thin-film technology and is used for measuring the deformation of the substrate (2) when pressure is applied or a force is introduced, the strain-sensitive element (3) including XAlOyN1-y, wherein X is a metal with a high melting temperature in the range of greater than 1400° C. and 0<y<0.4 applies. A passivation layer (5) can be applied to the strain-sensitive element (3).