Zhongkai Zhang

Tungsten-rhenium thin film thermocouples for SiC-based ceramic matrix composites

A tungsten-rhenium thin film thermocouple is designed and fabricated, depending on the principle of thermal-electric effect caused by the high temperature. The characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. The working mechanism and thermo-electric features of the thermocouples are analyzed depending on the simulation results. Then the thin film thermocouples are fabricated and calibrated. The calibration results show that the thin film thermocouples based on the tungsten-rhenium material achieve ideal static characteristics and work well in the practical applications.

Range Analysis of Thermal Stress and Optimal Design for Tungsten-Rhenium Thin Film Thermocouples Based on Ceramic Substrates

A thermal stress range analysis of tungsten-rhenium thin film thermocouples based on ceramic substrates is presented to analyze the falling off and breakage problems caused by the mismatch of the thermal stresses in thin film thermocouples (TFTCs) and substrate, and nano-indentation experiments are done to measure and calculate the film stress to compare with the simulation results. Optimal design and fabrication of tungsten-rhenium TFTCs based on ceramic substrates is reported. Static high temperature tests are carried out, which show the optimization design can effectively reduce the damage caused by the thermal stress mismatch.

High Temperature High Sensitivity Multipoint Sensing System Based on Three Cascade Mach–Zehnder Interferometers

A temperature multipoint sensing system based on three cascade Mach–Zehnder interferometers (MZIs) is introduced. The MZIs with different lengths are fabricated based on waist-enlarged fiber bitapers. The fast Fourier transformation is applied to the overlapping transmission spectrum and the corresponding interference spectra can be obtained via the cascaded frequency spectrum based on the inverse Fourier transformation. By analyzing the drift of interference spectra, the temperature response sensitivities of 0.063 nm/°C, 0.071 nm/°C, and 0.059 nm/°C in different furnaces can be detected from room temperature up to 1000 °C, and the temperature response at different regions can be measured through the sensitivity matrix equation. These results demonstrate feasibility of multipoint measurement, which also support that the temperature sensing system provides new solution to the MZI cascade problem.

Measurement study of residual stress on tungsten-rhenium thin film thermocouples by nanoindentation technology

In this paper, Nano-indentation technology is used to test the mechanical property of the tungsten-rhenium thin film, including hardness, elastic modulus and residual stress. The effects of different heat treatment temperature and different substrates on the hardness and elastic modulus of tungsten-rhenium films were studied. We research three substrates which are silicon carbide ceramic, aluminum oxide ceramic and zirconium oxide ceramic. Test results show that the tungsten-rhenium films on aluminum oxide ceramic shows the biggest values of elastic modulus and the smallest on silicon carbide ceramic. However, value of hardness is biggest on zirconium oxide ceramic and smallest on aluminum oxide ceramic. Besides, the heat treatment temperature has high influence on hardness and elastic modulus of tungsten-rhenium film. And under different substrates, the hardness and elastic modulus of film on zirconium oxide ceramic is the most sensitive to heat treatment temperature. By contrast, silicon carbide ceramic is the least.

A protected tungsten-rhenium thin film thermocouples sensor

A tungsten-rhenium thin film thermocouples is designed and fabricated, and the characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. Protective film was presented to prevent from the oxidation and evaporation of tungsten-rhenium TFTCs at high temperature. The experiment shows TFTCs sensor with protective film have an acceptable linearity up to 1370K with a suitable voltage output and can work for half an hour at 1370K, however the TFTCs without protective films break after high temperature constant at 900K.

A Fabry-Perot interferometer for high temperature measurement based on mode analysis

A fourier analysis applied to the Fabry-Perot interferometer(FPI) transmission spectrum for temperature measurement is proposed and experimentally demonstrated in this paper. In the fast Fourier transform (FFT) spectrum of the FPI transmission spectrum, a higher order model is separated from the transmission spectrum and the spatial frequency spectra of the higher order model is detected. As the temperature change, the shifts of the spatial frequency spectrum will be observed. The sensitivity of the temperature is 0.00012/(nm · °C). The proposed sensor features the advantages of easy fabrication, compact structure and stable chemical property, and it exhibits great potential in high temperature measurement.