User Benefits
- The HPV-X3 high-speed video camera enables high-speed imaging of up to 20 Mfps.
- The camera is capable of capturing high-resolution images of the high-frequency oscillations of microbubbles and the
shape changes during their contraction process.
Introduction
Lithium-ion batteries play an important role in various electronic devices due to their high energy density and excellent charging efficiency. To improve battery performance, battery materials and processing methods are actively being developed. One of the evaluation methods for mechanical properties is strength measurement. The metal (current collector) used in the electrodes of lithium-ion batteries is subjected to tensile force during the manufacturing process. Evaluation of temperature dependence is required because the metal is also subjected to heat during manufacturing. This Application News introduces a workflow consisting of tensile strength evaluation of metal foil used as lithium-ion battery electrodes. The tests were performed under various temperatures to evaluate the temperature dependence of tensile strength. The apparatus used is also described.
Measurement System
The observation setup, the microscope section, and a schematic diagram of the microscope section are shown in Fig. 2, 3, and 4, respectively. Fig. 3 is an enlarged view of the white-framed area in Fig. 2. A glass cell containing the substrate and degassed water was set in the microscope. The laser was focused from the back of the glass substrate to generate bubbles. The generated bubbles were observed using the HPV-X3 from a horizontal directive relative to the substrate surface. A laser light source with a wavelength of 640 nm (Cavilux) was used for illumination.
Measurement System
The observation setup, the microscope section, and a schematic diagram of the microscope section are shown in Fig. 2, 3, and 4, respectively. Fig. 3 is an enlarged view of the white-framed area in Fig. 2. A glass cell containing the substrate and degassed water was set in the microscope. The laser was focused from the back of the glass substrate to generate bubbles. The generated bubbles were observed using the HPV-X3 from a horizontal directive relative to the substrate surface. A laser light source with a wavelength of 640 nm (Cavilux) was used for illumination.
Observation Results
Initially, the entire phenomenon of water vapor microbubbles vibrating was captured at a speed of 1 Mfps, and it was
confirmed that the microbubbles undergo repeated expansion and contraction. The process from bubble generation to
disappearance is shown in Fig. 5. As seen in Fig. 5(14) and (15), the behavior of the bubbles just before disappearance cannot be captured in detail at 1 Mfps. Next, the image capture speed was changed to 20 Mfps. The results are shown in Fig. 6. The shape of the bubble tip during the contraction process appears arc-shaped in Fig. 5 and 6(1) and (2). However, as contraction progresses, this changes, and in Fig. 6(5), it can be seen that the tip shape momentarily becomes sharp.
Conclusion
Using the HPV-X3 high-speed video camera, the repeated expansion and contraction of water vapor microbubbles
generated by laser irradiation was captured. The HPV-X3 is capable of high-speed imaging at up to 20 Mfps, and by
recording at this maximum speed, it was possible to observe the high-frequency oscillations of the bubbles as well as the shape changes during the contraction process.
References
1) Namura, K., Okai, S., Kumar, S., Nakajima, K., Suzuki, M.:
Advanced Materials Interfaces, 7 (18) (2020) 2000483.
Related Applications
1. Oscillation Analysis of Water Vapor Bubbles Using High-Speed
Video Camera – High-Speed Imaging of Sub-MHz-Order
Oscillations –, Application Note No. 84
Photography cooperation:
Department of Micro Engineering, Graduate School of Engineering,
Kyoto University
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