研究目的
Investigating the detection of copper particle contamination in transformer oil using laser-induced breakdown spectroscopy (LIBS) technology.
研究成果
The research focuses on the detection of copper particle contaminants in transformer oil using LIBS technology. The quantitative analysis method was determined by LIBS signal of the effective laser spots in analysis area. More specifically, by analyzing the absolute intensity and normalized intensity of the characteristic lines of Cu element, the normalized intensity Cu I 324.75 nm/ CN 358.6 nm shows the best linear correlation with Cu particle mass concentration, and the LOD of Cu particle concentration calculated from the fitting curve is sub-ppm level (0.77 μg/g) and less than the critical value of the particle contaminant standard, which proves that the method is suitable for the detection of particle contaminants in transformer oil.
研究不足
The RSD value of the relative intensity at 0.54 μg/g is still above 15%, to improve experiment repeatability, some methods for improving the RSD of LIBS analysis, such as auto-focus system and LIBS-LIF could be used for further research. And signal enhancement methods such as DP-LIBS, RE-LIBS and optimization of substrate material might improve the LOD for the robust application prospect.
1：Experimental Design and Method Selection:
A Q-switched laser with 1064 nm wavelength was used for ablation. The laser energy and pulse frequency were 60 mJ and 1 Hz, respectively. A lens with 100 mm focal length was used to focus the laser on the sample surface. An X-Y-Z translation stage was used to provide a fresh oil layer for each laser pulse during the measurements. Plasma emission was collected by a lens and the fiber entrance was centered at 2 mm above the sample surface. The fiber delivered the plasma emission into a multichannel spectrometer.
2：Sample Selection and Data Sources:
Oil samples with different Cu particle concentrations in the range from
3：54 μg/g to 4 μg/g were studied. List of Experimental Equipment and Materials:
Q-switched laser (Brilliant Eazy, Quantel, France), lens (NBK-7 plano-CX, Thorlabs, America), multichannel spectrometer (AvaSpec-ULS2048-3-USB2, Avantes, Holland), ultrasonic cleaner (CP-3515DTH-360).
4：0). Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The oil samples were prepared by adding a certain amount of dispersant and copper powder into the bottle with pretreated oil. The bottle was placed in an ultrasonic cleaner for stable dispersion of copper particles in oil. Then, 100 μL oil was dropped onto a 4 cm×4 cm square filter paper. The oil spread area was roughly of circular shape with a diameter of approximately 20 mm.
5：Data Analysis Methods:
The plasma emission spectra in the range of 200-1015 nm were recorded and stored in the computer by use of the spectrometer's software package (AvaSoft). Five replicate measurements were carried out for each oil sample to improve repeatability.
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