Development of thin film heat flux sensor based on transparent conductive oxide thermopile with antireflective coating

Abstract

Purpose The measurement of heat flux is of importance to the development of aerospace engine as basic physical quantities in extreme environment. Heat radiation is one of the basic forms of heat transfer phenomenon. The structure optimizing can improve the performance and infrared absorptivity of the thin film sensor. Design/methodology/approach This paper designed one kind of thin film heat flux sensor (HFS) with antireflective coating based on transparent conductive oxide thermopile. The introduced membrane structure is so thin that it has little impact on sensor performance. Fabrication of thin film sensors were fabricated by physical vapor deposition (PVD) process. Findings The steady-state and dynamic response characteristics of the HFS were investigated by calibration platform. The experimental results shown that the absorptivity of the membrane structure (for1070nm) improved compared with that before optimization. The sensitivity of heat flux gauge was 48.56 µV/ (kW/m2) and its frequency response was determined to be about 1980 Hz. Originality/value The thin film HFS uses thermopile based on Indium Tin Oxid and In2O3. The antireflective coating is introduced to hot endpoint of HFS to improve sensitivity on laser thermal source. The infrared optical properties of membrane layer structure were investigated. The steady-state and the transient response characteristics of the heat flux sensor were also investigated.

High Temperature Heat Flux Sensor With ITO/In2O3 Thermopile for Extreme Environment Sensing

“…The substrates are mainly made of two materials, ceramic or metal, with ceramic substrate Al2O3 2,17,22,25,28,29 predominating and to a lesser extent AlN ceramics 18, 27. The sensitive layer is mainly made of metals, metal oxides, most of which are platinum rhodium precious metals Pt-Pt/Rh 17,19,22,23,29 and ITO-In2O3 2,21,24,28 ，and some are other precious metals, such as constantan 25 and tungsten rhenium thermocouples 18 . Among them, ITO-In2O3, as a transparent conductive oxide, has the advantages of high-temperature resistance, high output, and strong oxidation resistance in hightemperature environments, which can be used as a substitute for precious metal thermopiles 28 . The main materials for the thermal resistance layer are alumina 2,19 , silicon dioxide 19,20,[23][24][25]27,29 , YSZ 28 , etc.…”

“…Among them, ITO-In2O3, as a transparent conductive oxide, has the advantages of high-temperature resistance, high output, and strong oxidation resistance in hightemperature environments, which can be used as a substitute for precious metal thermopiles 28 . The main materials for the thermal resistance layer are alumina 2,19 , silicon dioxide 19,20,[23][24][25]27,29 , YSZ 28 , etc. Li et al 2 fabricated an ITO-In2O3 thermoelectric stack thin film heat flux meter using magnetron sputtering method on a nickel alloy substrate, with a sensitivity of 61.93 uV/(kW/m 2 ) and a maximum operating temperature of 888 ℃.…”

“…Among all kinds of thin film HFSs, thermoelectric stack type thin film HFSs stand out due to their large output, high sensitivity, and fast response [19][20][21] . Researchers have carried out systematic and extensive research on thermoelectric stack type thin film HFSs, which are mainly composed of three parts, substrate, thermoelectric stack sensitive layer and thermal resistance layer [22][23][24][25][26][27][28][29] . The substrates are mainly made of two materials, ceramic or metal, with ceramic substrate Al2O3 2,17,22,25,28,29 predominating and to a lesser extent AlN ceramics 18, 27. The sensitive layer is mainly made of metals, metal oxides, most of which are platinum rhodium precious metals Pt-Pt/Rh 17,19,22,23,29 and ITO-In2O3 2,21,24,28 ，and some are other precious metals, such as constantan 25 and tungsten rhenium thermocouples 18 .…”

“…Researchers have carried out systematic and extensive research on thermoelectric stack type thin film HFSs, which are mainly composed of three parts, substrate, thermoelectric stack sensitive layer and thermal resistance layer [22][23][24][25][26][27][28][29] . The substrates are mainly made of two materials, ceramic or metal, with ceramic substrate Al2O3 2,17,22,25,28,29 predominating and to a lesser extent AlN ceramics 18, 27. The sensitive layer is mainly made of metals, metal oxides, most of which are platinum rhodium precious metals Pt-Pt/Rh 17,19,22,23,29 and ITO-In2O3 2,21,24,28 ，and some are other precious metals, such as constantan 25 and tungsten rhenium thermocouples 18 . Among them, ITO-In2O3, as a transparent conductive oxide, has the advantages of high-temperature resistance, high output, and strong oxidation resistance in hightemperature environments, which can be used as a substitute for precious metal thermopiles 28 .…”

Highly sensitive flexible heat flux sensor based on a microhole array for ultralow to high temperatures

“…However, existing studies focus more on HFSs used at high temperatures 21 and less on devices that are flexible, bendable, and easy to attach and install. Li et al 22 , 23 studied HFSs for aeroengines with a sensitivity of 0.06193 μV/(W/m 2 ), which could measure 236.4 kW/m 2 at 888 °C through an anti-emission coating, ultimately achieving a sensitivity of 0.04856 μV/(W/m 2 ). Fu et al 24 developed an HFS able to survive 1 h in 1000 °C air with a sensitivity of 0.0038 μV/(W/m 2 ).…”