Performance and Durability of Thin Film Thermocouple Array on a Porous Electrode

Abstract

Management of solid oxide fuel cell (SOFC) thermal gradients is vital to limit thermal expansion mismatch and thermal stress. However, owing to harsh operation conditions of SOFCs and limited available space in stack configuration, the number of techniques available to obtain temperature distribution from the cell surface is limited. The authors previously developed and studied a thermocouple array pattern to detect surface temperature distribution on an SOFC in open circuit conditions. In this study, the performance in terms of mechanical durability and oxidation state of the thin film thermoelements of the thermocouple array on the porous SOFC cathode is investigated. A thin-film multi-junction thermocouple array was sputter deposited using a magnetron sputter coater. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) characterisation techniques were carried out to understand characteristics of the thin film before and after temperature (20 °C–800 °C) measurement. Temperature readings from the sensor agreed well with the closely placed commercial thermocouple during heating segments. However, a sensor failure occurred at around 350 °C during the cooling segment. The SEM and XPS tests revealed cracks on the thin film thermoelements and oxidation to the film thickness direction.

The Seebeck Coefficient of Sputter Deposited Metallic Thin Films: The Role of Process Conditions

“…Thin film sensing applications, such as thin film thermocouples, can be very attractive for lightweight structures, small devices or applications in need of a high temporal, or spatial resolution as they have a very low mass, reduced dimensions, and a very fast response time [1][2][3][4][5]. For example, thin film thermocouples are used for nanoscale thermometry [6][7][8], for monitoring local temperature distributions on integrated-circuits [9,10], in solid oxide fuel cells [11], and turbine engines [12], or for monitoring sudden temperature changes in cutting tools for machining explosive materials [13]. Furthermore, thin film sensors can be embedded inside composite materials without affecting the structural integrity of the material by their dimensional extent, enabling local and in situ sensing without compromise.…”

Spring Based Connection of External Wires to a Thin Film Temperature Sensor Integrated Inside a Solid Oxide Fuel Cell

“…For those sensors including resistance temperature detectors (RTD), thermistors, resistance strain gauges (RSG), and TCs used in the thin film form, external wire connection plays a key role as a step in the determinant pathway for accurate and constant signal collection 21 . Additionally, the intrusions to signal properties, especially due to aging, parasitic thermal voltages and internal resistance, all have direct correlation with the connection mechanism; furthermore, these mechanisms typically occur slowly and not are hence not easily noticeable, resulting in ‘drift’ and inaccurate sensor readings 29,30 . Therefore, it is paramount to have a mechanically stable and electronically conductive connection.…”

Development of a Novel Multi-Channel Thermocouple Array Sensor for In-Situ Monitoring of Ice Accretion

“…MCTCA and commercial TCs measurements were recorded with a mean frequency of 0.320 Hz using an NI 9213 data logger and a proprietary LabVIEW based data logging software developed by J.-S. Kim et al [42][43][44][45][46][47][48][49][50].…”

“…To this end, this study suggests a novel ice detection sensor by using a proprietary multi-channel thermocouple array (MCTCA) technology [42][43][44][45][46][47][48][49][50] by measuring the latent heat of fusion, which is the unique physical characteristic when liquid water turns into ice. Thermoelements can be arranged in an array or grid configuration with each node spot-welded or soldered to produce a thermocouple (TC) junction.…”