Depth Profile And Element Analysis Of NdFeB Permanent Magnetic Material By Glow Discharge Mass Spectrometry

NdFeB permanent magnet material has become an indispensable material of modern industry owing to its excellent magnetism. Due to electrochemical corrosion and oxidation easily, coatings are often used to protect the magnet; elements of different types and contents are often added to improve magnetic performance, corrosion resistance, and cost-effect of the material. Rapid and accurate detection of the coating and element has important significance for the development, production and quality control of the material. Compared with other depth profile methods, glow discharge mass spectrometry (GD-MS) has advantages such as rapid analytical speed, large sampling range and easy sample preparation, but the sputtering rate of fast flow glow discharge ion source is too fast, so depth profile of thin coatings needs to be explored; compared with wet analysis, GD-MS has no sample pretreatment, avoids dissolved reagent contamination and environment pollution, and also avoids spectral interference among rare earth elements, but it is currently mainly used in the semi-quantitative analysis of high purity materials, so under the circumstance of lacking standard samples quantitative analysis of macro and micro elements of materials needs to be tried.In this paper, GD-MS was used for depth analysis of coating and quantitative analysis of macro and micro elements in the interior of NdFeB. Zn coating, Al coating and Ni-Cu-Ni coating were experimented respectively, the problems such as how to identify coatings, to control the sputtering rate, to improve the accuracy of the content, to obtain a sufficient information and to obtain a flat pit of the sputtering were solved. By full element determination or physical testing, coating specie was determined; by reducing the discharge current appropriately, the sputtering rate was reduced; by shortening the time of the test method, the ingredient information was collected as much as possible; by replacing the corresponding electrical parameters of the lens, the accuracy of multi-coatings was improved; by optimizing discharge conditions, the relatively flat sputtering pit was obtained; by measuring reference samples different sputtering rates of coatings were obtained and transformation between time and depth was completed, the final results of depth profile coincided with scanning electron spectroscopy. Six control samples were developed to solve the problem of lacking standard samples for quantitative analysis. Referring production process of standard samples such as the component design, preparation and processing of materials, homogeneity test and verifying the element content, six control samples were prepared, the instrument conditions were optimized, the correlation coefficients of working curves were all above 0.99, two samples were measured at last and the results were compared with inductively coupled plasma atomic emission spectrometry, the accuracy and precision of the method was satisfied, so the quantitative analysis of macro and micro elements by GD-MS was achieved.The results of this experiment show that depth profile can be carried out accurately by properly controlling the sputtering rate and optimizing discharge conditions to obtain flat sputtered pit; this method expands the scope of the instrument application and provides reference for longitudinal design and test of elements in the materials. By establishing control samples the macro and micro elements including RE are determined; this method avoids the matrix and spectral interference between RE elements and provides reference for quantitative analysis of solids injection without standard samples.