The Research On Matrix Effect Caused By Binary Alloy Phase Transformation In LIBS Composition Detection

Laser-induced breakdown spectroscopy technology is a composition analysis technology based on the principle of laser-substance interaction and plasma spectroscopy,and has been widely used in the field of alloy composition analysis.However,the spectral signal is dependent on the target material matrix,and the sample characteristics such as the alloy phase composition will affect the spectral data,making it difficult for us to construct a unified composition detection standard.This phenomenon is called the Matrix effect.Understanding the mechanism of Matrix effect is extremely important for improving the accuracy of LIBS analysis.To this end,this topic will take the Matrix effect caused by binary alloy phase transformation as the research object,combine experiments,theoretical analysis,and numerical simulation to analyze the mechanism of Matrix effect,and explore the influence of laser pulse width and energy density on Matrix Effect.Finally,a method to overcome the Matrix effect is proposed.The specific research content and results are as follows:First of all,this paper builds the LIBS component detection system,constructs the calibration curve of 3 groups of samples and the spectral line intensity ratio of 2 groups of samples,and analyzes the influence of binary alloy phase transformation on the LIBS detection calibration curve and spectral line intensity ratio.It is found that the phase change will cause a sudden change of the calibration curve.When the composition is the same,the change of the phase composition will cause the change of the spectral line intensity ratio.Secondly,this paper studies the influence of the laser pulse width on the phase change Matrix effect,and finds that reducing the laser pulse width can effectively overcome the Matrix effect.The method of numerical simulation combined with ablation characteristic detection and theoretical analysis are used to explain the reason:under the same energy density input,compared with ns laser,the ablation temperature reached by the lattice under ps laser ablation conditions is higher,which suppresses The non-stoichiometric ablation phenomenon,and the difference in ablation characteristics caused by the different phase composition under low energy density is eliminated,thereby overcoming the Matrix effect.Furthermore,this paper studies the influence of laser energy density on the phase change Matrix effect,and finds that increasing the laser energy density can effectively overcome the Matrix effect.The method of numerical simulation combined with the detection of ablation characteristics and theoretical analysis explains the reason: the higher the laser energy density,the higher the ablation temperature reached by the sample,and the phases that are difficult to ablate can also be fully ablated.All samples are fully ablated,the element composition of the plasma cloud generated by erosion is the same as that of the target,and the spectral line intensity ratio can reflect the concentration ratio of the elements in the target,thereby overcoming the Matrix effect caused by the difference in phase composition.Finally,this article summarizes and analyzes the mechanism of the phase change Matrix effect.The conclusion is as follows: due to the different stability of different phases,there are differences in the ablation characteristics of alloy samples composed of different phases at low energy densities.Samples composed of phases with low stability are more likely to be ablated.The element composition in the plasma cloud is the same as that in the target material.The spectral line intensity ratio can reflect the concentration ratio of the elements in the target material.The samples with high stability phase composition are more difficult to be ablated,showing the characteristics of non-stoichiometric ablation.The spectrum line intensity ratio cannot truly reflect the element concentration ratio in the target material,which leads to a sudden change in the calibration curve at the phase transition point.