Rapid Quantitative Analysis of Hydrogen in Titanium Alloys by Laser Sputtering Ionization Time-of-flight Mass Spectrometry

Titanium alloy is an important structural material with many advantages of high strength, excellent corrosion resistance, good biocompatibility, and good processing performance, which has been widely used in aerospace, medical devices, automobile manufacturing and various other fields. However, the presence of hydrogen in titanium alloys can lead to hydrogen embrittlement, which degrades the mechanical properties. Due to its high ionization energy, high reactivity, and high diffusivity, quantitative analysis of hydrogen in metal or alloy materials faces enormous challenge. Accurately and quickly detecting the hydrogen content in titanium alloys is of great significance for optimizing material design and controlling product quality. Traditional methods for determining the hydrogen in titanium alloys require complicated sample pretreatment, which greatly prolong the analysis time. The self-built high irradiance laser ablation and ionization time-of-flight mass spectrometry (LAI-TOF MS) has many advantages such as high sensitivity, high resolution, multi-element simultaneous detection, and simple sample pretreatment. It introduces helium into the ion source as a buffer gas to cool the high kinetic energy ions and reduce the multi-charged ion interferences, and has been successfully applied to the determination of metallic and nonmetallic elements in solid samples. In this study, a direct quantitative analysis method of LAI-TOF MS was established for detecting hydrogen in titanium alloys. The calibration curve of intensities and contents for hydrogen has a correlation coefficient of 0.991 3, the limit of detection (LOD) is calculated to be 0.000 4%, and the atomization and ionization efficiency of hydrogen can reach 13.4%. This method was applied to the analysis of hydrogen in other titanium alloy samples. The relative standard deviations (RSDs) of hydrogen signals are less than 14%. The relative errors of the quantitative results are less than 5% compared with values obtained by the pulsed heating-infrared method. The analysis time for a single titanium alloy sample is only a few minutes, significantly shorter than the 2-4 h required for the pulsed heating-infrared method. The spectrum obtained by LAI-TOF MS enables qualitative and semi-quantitative determination of trace elements of Be, C, Al, Si, P, Ca, Cr, Fe, Zr, Mo, Pd, In and Sn in the titanium alloy samples. Considering the advantages of less sample preparation, simplicity, rapidness, and high sensitivity, the method based on LAI-TOF MS can be used to the directly quantitative analysis of hydrogen in titanium alloys and can be further extended to the quantitative analysis of hydrogen in other materials, such as hydrogen storage materials, metal materials, ceramic materials and other related materials.