RTD for Ceramic Matrix Composites Using Diffusion Barriers
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Solution Overview
Problem
Existing resistance temperature detectors (RTDs) face challenges in accurately monitoring temperature and strain in harsh environments of gas turbine engines due to surface roughness and stability issues at elevated temperatures, particularly with ceramic matrix composite (CMC) components.
Innovation Solution
A resistance temperature detector (RTD) utilizing a ceramic matrix composite (CMC) substrate with a conductive material like platinum, integrated with oxygen and silicide diffusion barriers, and an environmental barrier coating, allowing for high-temperature operation and strain measurement without adhesives, and enabling the RTD to function as both a temperature and strain sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thin film sensors are deposited directly onto the CMC surface, then surface measurement capability is achieved, but surface roughness due to SiC fiber weaves degrades measurement accuracy and device stability
Solution Approach 1:
A planarizing layer is introduced as an intermediary between the rough CMC surface and the thin film sensor. This layer fills in the surface irregularities caused by SiC fiber weaves, creating a smooth substrate for sensor deposition that maintains both measurement accuracy and thermal stability.
Solution Approach 2:
The sensor structure employs composite material layers including the planarizing layer and environmental barrier coating integrated with the CMC substrate. This composite approach combines materials with complementary properties to achieve both surface smoothness and high-temperature stability.
2Reliability
If thin film sensors are used on CMC components, then low mass and fast response time are achieved, but interdiffusion at elevated temperatures degrades sensor stability
Solution Approach 1:
Environmental barrier coatings and diffusion barrier layers are introduced as intermediary protective layers between the thin film sensor and the CMC substrate. These barrier layers prevent harmful interdiffusion of atoms at elevated temperatures while allowing the sensor to maintain its low mass and fast response characteristics.
Solution Approach 2:
The environmental barrier coating creates a protective environment around the sensor elements, isolating them from the harsh high-temperature oxidation and interdiffusion conditions in the gas turbine engine environment.
3Duration of action of stationary object
If conventional RTD instrumentation is installed on CMC engine components, then temperature monitoring is achieved, but the harsh environment and rotational forces reduce operational duration
Solution Approach 1:
The RTD instrumentation is merged with the CMC component structure itself, using the CMC substrate as the active sensing element. This integration eliminates separate instrumentation that would be vulnerable to harsh environments and rotational forces, allowing the component to monitor its own temperature and strain conditions.
Solution Approach 2:
The CMC component serves itself by having embedded sensors that utilize the component's own structure and properties for sensing. The CMC substrate's inherent piezoresistive and thermal properties are exploited for self-monitoring, eliminating the need for external instrumentation that would reduce operational duration.
4Ease of operation
If thin film sensors are deposited on CMC surfaces, then gas flow path interference is minimized, but adhesive requirements and manufacturing complexity increase
Solution Approach 1:
The planarizing layer serves as an intermediary that enables direct deposition of thin film sensors onto the rough CMC surface without requiring adhesives. This layer provides a smooth substrate that simplifies the manufacturing process while maintaining the low-profile characteristic necessary for gas flow compatibility.
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 RTD achieves stable temperature measurements up to 1600°C and effective strain monitoring by maximizing thermoelectric power through fiber orientation, with improved high-temperature stability and reduced interdiffusion effects, enabling prolonged operation in extreme conditions.
Implementation Method 1
A resistance temperature detector (RTD) is a resistive device that measures the electrical resistance of a component and relates this resistance to temperature
Implementation Method 2
The RTD comprises an oxygen diffusion barrier deposited on the conductive material in a vicinity of the openings
Implementation Method 3
The RTD comprises a silicide diffusion barrier between the conductive material and the CMC substrate
Implementation Method 4
the CMC itself as the active sensor element... capable of accurately monitoring the temperature and strain of CMC engine components
Data Source
AI summary
A resistance temperature detector (RTD) that uses a ceramic matrix composite (CMC), such as a silicon carbide fiber-reinforced silicon carbide matrix, as an active temperature sensing element, which can operate at temperatures greater than 1000° C. or even 1600° C. Conductive indium tin oxide or a single elemental metal such as platinum is deposited on a dielectric or insulating layer such as mullite or an environmental barrier coating (EBC) on the substrate. Openings in the layer allow etching of the CMC surface in order to make high quality ohmic contacts with the conductive material, either directly or through a silicide diffusion barrier such as ITO. The RTD can measure both temperature and strain of the CMC. The use of an EBC, which typically is deposited on the CMC by the manufacturer, as the insulating or dielectric layer can be extended to other devices such as strain gages and thermocouples that use the CMC as a sensing element. The EBC can be masked and etched to form the openings. A conductive EBC can be used as the silicide diffusion barrier.