Lithium Corrosion Resistance Analysis Of Er₂O₃ Coating Based On The Calibration-free Method Of Laser-induced Breakdown Spectroscopy

Nuclear fusion is considered to be the solution to human energy problem.The Tokamak device is the promising device to achieve nuclear fusion.Its internal blanket structure faces deuterium-tritium penetration,MHD effect,and liquid metal lithium corrosion after application.Studies have shown that Er₂O₃ coating can be used as a protective coating to solve the above problems.This article emphasizes on the preparation process of Er₂O₃ coating by sol-gel method and its lithium corrosion resistance,and investigates the influence of preparation process parameters on the coating itself and lithium corrosion resistance.The laser induced breakdown spectroscopy(LIBS) free calibration method,which is more advantageous than the traditional weightless method,is proposed for the penetration analysis of lithium in depth profile that can be used to realize the analysis of the corrosion resistance.The main research contents are as follows:XRD patterns of Er₂O₃ coatings of the sol-gel spin-coating process at different annealing temperatures were investigated and found that the Er₂O₃ coatings are cubic phases.The grain size and internal residual compressive stress increase with the annealing temperature.It is considered that it's hard to prepare Er₂O₃ coatings with dense-coating,none-cracks and larger grain size by sol-gel method at the same annealing temperature simultaneously.The thickness of the coating has a good linear correlation with the number of spin-coating.Combined with the research results of the coating resistivity,it can be proved that the coating has the ability to resist tritium penetration and the MHD effect.The SEM and EDS characterization results of the lithium corrosion of Er₂O₃coating confirmed the existence of lithium corrosion products and explained the mechanism of corrosion products.In order to study the accuracy of the free calibration method of laser induced breakdown spectroscopy under the experimental conditions,the time-resolved spectrum of the S18 alloy prepared by the tablet method was investigated.The continuous radiation intensity of the elements is relatively low under the experimental conditions,and the delay time has a greater influence on the signal intensity and signal-to-noise ratio.About 0.4?s is considered the best delay time for spectrum acquisition.The plasma electron temperature and electron number density are calculated to be about 10010 K and1.05×10²³ m^-3 through the free calibration method modified by the Saha-Boltzman method and the Stark broadening method.The element content obtained by quantitative analysis is compared with the content of the standard sample.It is found that the error of the main element analysis by CF-LIBS is less than 15%.The error may come from instrument error,non-stoichiometric ablation,deviation of local thermodynamic equilibrium conditions or uncertainty of A_ki.The relationship between the number of laser pulses and the depth of ablation pits was studied using a three-dimensional optical profiler,and it was proved that the number of laser pulses and the depth of ablation pits showed a well linear relationship under the experimental conditions.The content ratio of erbium and lithium is used to semi-quantitatively analyze the lithium permeation distribution,which eliminates the error of the instrument response parameter in the normalized equation and simplifies the calculation of the CF-LIBS to analyze the lithium penetration in Er₂O₃ coating.Analysis of lithium penetration of Er₂O₃ coatings prepared at three annealing temperatures found that the resistance of large grains of coatings prepared at high temperature to corrosion penetration was eliminated by internal pores,which showed poor resistance to lithium penetration.The lithium content of the coating prepared by annealing at 650? and 800?is less than 1% at 0.42?m,and it is believed that the penetration of lithium in these coatings not exceed 0.5?m.