10:45 〜 12:15
[MIS14-P11] 航空機で得られる微小重力環境下での低温ガス中蒸発法による氷ナノ粒子の核生成実験
キーワード：核生成、微小重力、ナノ粒子、氷
The gas evaporation method has long been known as a simple method to produce nanoparticles from the gas phase [1-3]. In this method, nanoparticles are produced via homogeneous nucleation during the cooling process of high-temperature vapor generated by heating and evaporating refractory materials in a room-temperature environment. We extended the method for materials with low melting points and have established a low-temperature gas evaporation method that can produce ice nanoparticles. To understand the nucleation process of ice nanoparticles, it is necessary to determine two physical quantities of ice nanoparticles, surface free energy and sticking probability. It is also necessary to know the nucleation process of ice nanoparticles formed from its vapor. The two physical quantities can be determined by observing the nucleation environment in situ with an interferometer and using nucleation theory. The nucleation process can be determined based on the time evolution of the infrared spectrum from the gas phase to the formation of nanoparticles.
In order to obtain accurate physical quantities necessary for modeling nucleation, nucleation experiments must be performed in a homogeneous environment obtained in microgravity [4-6], which is also necessary to observe the infrared spectrum during nucleation process over a long period of time. Therefore, we have developed a small nucleation chamber that can be onboard an aircraft or sounding rocket , which can provide a microgravity environment. In order to obtain accurate data necessary for understanding nucleation, experiments using sounding rockets that can obtain a microgravity environment of about 10-4 G will eventually be necessary. Here we report preliminary results of a microgravity experiment using an aircraft (MU-300, Diamond Air Service) as a preliminary experiment for this purpose.
The low-temperature nucleation chamber was constructed as a double-tube structure, and the chamber was cooled by a refrigerant in the outer tube. The temperature of the evaporation source and argon gas, which is introduced into the chamber as a buffer gas, in the chamber is also cooled by the refrigerant, and at the beginning of the experiment, both are in thermal equilibrium.
The water vapor generated by heating and sublimating ice in the developed low-temperature nucleation chamber is cooled by argon gas. Nanoparticles are formed through homogeneous nucleation after supersaturation. This process was observed in situ using a double-wavelength Mach-Zehnder type laser interferometer and an infrared spectrometer. The interferometer can quantitatively determine the temperature and concentration fields from evaporation to nucleation, and the infrared spectra can study the changes in the crystal structure of water and ice particles during the nucleation process.
Since there is a limit to the amount of refrigerant that can be carried on board an aircraft, a refrigerant with a melting point of -51°C was used in this experiment. As a result of the experiment, we succeeded in capturing the moment of nucleation by interferometer, and also succeeded in capturing the temporal change in the intensity of infrared absorption. This means that the nucleation process of ice nanoparticles from water vapor was captured. This achievement is expected to lead to the construction of a nucleation model that can predict the state of ice dust formation that repeatedly sublimated and condensed in the primordial solar nebula 4.6 billion years ago.
[1] K. Kimoto et al. Japanese Journal of Applied Physics, 2 (1963) 702.
[2] R. Uyeda Morphology of crystals, Part B, Ed. I. Sunagawa, p. 369, Terra, Tokyo, 1987.
[3] C. Kaito Japanese Journal of Applied Physics, 17 (1978) 601.
[4] Y. Kimura, et al. Science Advances, 3 (2017) e1601992.
[5] Y. Kimura, et al. The Astrophysical Journal Letters, 934 (2022) L10.
[6] Y. Kimura, et al. Science Advances, 9 (2023) eadd8295.
This experiment was partially supported by the Sumitomo Foundation Basic Science Research Grant, the Core Facility Project "R&T Collaboration Project" of Hokkaido University, and the Special Committee on Space Environment Utilization Front Loading Research of the ISAS, JAXA.
In order to obtain accurate physical quantities necessary for modeling nucleation, nucleation experiments must be performed in a homogeneous environment obtained in microgravity [4-6], which is also necessary to observe the infrared spectrum during nucleation process over a long period of time. Therefore, we have developed a small nucleation chamber that can be onboard an aircraft or sounding rocket , which can provide a microgravity environment. In order to obtain accurate data necessary for understanding nucleation, experiments using sounding rockets that can obtain a microgravity environment of about 10-4 G will eventually be necessary. Here we report preliminary results of a microgravity experiment using an aircraft (MU-300, Diamond Air Service) as a preliminary experiment for this purpose.
The low-temperature nucleation chamber was constructed as a double-tube structure, and the chamber was cooled by a refrigerant in the outer tube. The temperature of the evaporation source and argon gas, which is introduced into the chamber as a buffer gas, in the chamber is also cooled by the refrigerant, and at the beginning of the experiment, both are in thermal equilibrium.
The water vapor generated by heating and sublimating ice in the developed low-temperature nucleation chamber is cooled by argon gas. Nanoparticles are formed through homogeneous nucleation after supersaturation. This process was observed in situ using a double-wavelength Mach-Zehnder type laser interferometer and an infrared spectrometer. The interferometer can quantitatively determine the temperature and concentration fields from evaporation to nucleation, and the infrared spectra can study the changes in the crystal structure of water and ice particles during the nucleation process.
Since there is a limit to the amount of refrigerant that can be carried on board an aircraft, a refrigerant with a melting point of -51°C was used in this experiment. As a result of the experiment, we succeeded in capturing the moment of nucleation by interferometer, and also succeeded in capturing the temporal change in the intensity of infrared absorption. This means that the nucleation process of ice nanoparticles from water vapor was captured. This achievement is expected to lead to the construction of a nucleation model that can predict the state of ice dust formation that repeatedly sublimated and condensed in the primordial solar nebula 4.6 billion years ago.
[1] K. Kimoto et al. Japanese Journal of Applied Physics, 2 (1963) 702.
[2] R. Uyeda Morphology of crystals, Part B, Ed. I. Sunagawa, p. 369, Terra, Tokyo, 1987.
[3] C. Kaito Japanese Journal of Applied Physics, 17 (1978) 601.
[4] Y. Kimura, et al. Science Advances, 3 (2017) e1601992.
[5] Y. Kimura, et al. The Astrophysical Journal Letters, 934 (2022) L10.
[6] Y. Kimura, et al. Science Advances, 9 (2023) eadd8295.
This experiment was partially supported by the Sumitomo Foundation Basic Science Research Grant, the Core Facility Project "R&T Collaboration Project" of Hokkaido University, and the Special Committee on Space Environment Utilization Front Loading Research of the ISAS, JAXA.