Measurement And Research Of Spectral Of Sintering Process Of High Temperature Ceramic

High-temperature resistant ceramic is widely used in many special high-temperature fields such as aviation,aerospace and power systems et al.With a deeper understanding of high-temperature ceramic material thermal physical properties,the research work of the relationship of the ceramic real temperature and its emissivity is more important.In this paper,based on Planck’s Law,the multispectral radiation thermometry is used to compute the real temperature and emissivity of the ceramic in the wavelength range of 400-900 mm.Firstly,the thermal radiation spectrum of the material during the sintering process can be obtained by setting up the experimental platform for the in-situ spectra.Based on the thermal radiation spectrum,the thermal radiation energy of the material was analyzed in the heating zone,the detection area and the internal transmission characteristics of the spectrometer.The spectral data pretreatment method was studied.Using the way of the background data and the background noise are eliminated by background removal and noise reduction,and corrected of the transmitted signal of the instrument,the ideal spectral data is obtained.This provides a data base for further inversion calculation of true temperature and emissivity of the material.Secondly,the inversion algorithm of the real temperature and emissivity of the material is studied based on the spectral data.By using different emissivity models（different function relations between wavelength and emissivity）,the thermal radiation spectra of the materials at different temperatures are simulated.By using the Newton iterative method and the slowly changing characteristic of emissivity,the underdetermined problem of n equations and n + 1 unknowns is solved.Respectively,the theoretical methods and experimental methods are used to verify the model,the result show that the inversion results are in agreement with the actual emissivity,while the simulated temperatureresults are close to the set temperature.Finally,the thermal radiation spectrum of the three typical silicon-based high-temperature ceramic materials,SiC,SiO₂ and Si₃N₄,were collected at a set temperature of 1273 K,1373K,1473 K and 1573 K respectively.The above two algorithms were used to derive the real temperature and emissivity spectrum.The emissivity of the two algorithms is much closed.When the changing rate of emissivity is large,the inversion result of the slowly changing method is better,and the temperature difference is small and the calculation result of the emissivity is low.The research results can provide reference for the temperature control of ceramic materials during sintering process.The emissivity inversion algorithm and the results can be applied to the microstructural evolution analysis of ceramic sintering process.Inversion algorithm is also suitable for other materials,and provides an effective way for the establishment of various materials at different temperatures emissivity database.