P22
分割型ノズルを用いたガスジェット法による白金融体の密度計測
Density Measurement of Liquid Platinum by
Aerodynamic Levitation with Split Nozzle
高橋勇太 1, 白鳥英 2, 清宮優作 1, 加藤蒼 1, 小畠秀和 3, 杉岡健一 4, 石川毅彦 5, 小澤俊平 1
Yuta TAKAHASHI1, Suguru SIRATORI2, Yusaku SEIMIYA1, Sora KATO1, Hidekazu KOBATAKE3
Ken-ichi SUGIOKA4, Takehiko ISHIKAWA5, and Shumpei OZAWA1
千葉工業大学， Chiba Institute of Technology
東京都市大学，Tokyo City University
3 同志社大学， Doshisha University
4 富山県立大学， Toyama Prefectural University
5 宇宙航空研究開発機構，Japan Aerospace Exploration Agency (JAXA)
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1. Introduction
Simulating a phase transition, such as crystallization and vitrification, requires highly accurate density,
which is used as one of fundamental order parameters. However, with the conventional container method, it
is difficult to measure accurate density of melt for high melting point materials, because the sample is usuallycontaminated from the supporting materials at elevated temperatures. To avoid any contamination during thedensity measurement of high-temperature melt, containerless techniques such as electromagnetic levitation(EML) and electrostatic levitation (ESL) have employed in recent years. In the EML technique, only conductive
materials can be accommodated. Meanwhile, in the ESL technique, measuring samples with high vapor
pressure poses challenges.
In this study, we attempt to use an aerodynamic levitator (ADL) equipped with a split nozzle to measure
the density of high-temperature liquid platinum. While capturing the entire image of a levitated droplet ischallenging using a standard aerodynamic levitator, splitting the nozzle after levitating the droplet enables us
to observe it during its free fall.

2. Experimental procedure
Figure 1 shows a schematic diagram of the experimental setup of the ADL equipped with a split nozzle. Ahigh-purity platinum cube with a mass of 38 mg was melted on a copper hearth by irradiating it with asemiconductor laser, forming an almost spherical shape with a diameter of 1.5 mm. This spherical sample waspositioned on the ADL nozzle and levitated by a jet of Ar gas, injected from the bottom at a flow rate of
approximately 400 mL/min. The levitated sample was heated and melted by irradiating it with asemiconductor laser beam from above. The temperature of the droplet was controlled by adjusting the laser
power output with a monochromatic pyrometer. After the indicated temperature became constant, the ADL
nozzle was horizontally split into two, allowing the droplet to fall freely. The entire image of the droplet during
its free fall was captured from the side by a high-speed video (HSV) camera. To delineate the accurate contourof the sample, a semiconductor blue laser was used as a backlight, combined with a high-pass filter placed in
front of the camera.
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The contour of the free-falling droplet, immediately after the nozzle was split, was numerically fitted using
Legendre polynomials. The volume of the droplet was calculated from the fitted data under the assumptionthat the droplet maintained rotational symmetry in alignment with the gravitational direction. The density ofthe droplet was calculated from the volume and the sample mass after experiment.

semiconductor
laser beam

Split nozzle

Pyrometer

l=1.95～2.5 mm
Back Light

Laser Beam
Expanderhigh-pass filter

HSV camera

Figure. 1 schematic setup of ADR equipped with split nozzele

3. Results and Discussion
Figure 2 shows the density of liquid platinum measured in this study, along with some HSV images of thefree-falling droplet corresponding to the measurement plots. For comparison, the literature data measured byIshikawa et al.1) using ESL and Watanebe et al.2) using EML are also presented. The calculated density values
for liquid platinum show significant scatter, lacking consistency in relation to temperature. This inconsistency
can be attributed to two factors: (a) the unexpected formation of an unknown protuberance on the melt surface
in certain measurements, and (b) the misalignment of the rotational symmetry axis with the gravitational
direction. Due to these factors leading to an overestimation of the calculated volume, the resulting density
value inevitably increases.
When obtaining a nearly spherical shape of the droplet image as shown in (c), the calculated density valuesalign closely with the data reported by Ishikawa et al. and Watanebe et al. The unexpected appearance of theprotuberance, even when using high-purity platinum, remains unexplained. Splitting the nozzle may causesa slight asymmetry in the gas pressure applied to the droplet, which in turn might affect its rotation axis.
Further research is required to refine and improve the density measurements of high-temperature melts usingADL.
protrusion(a)Density ρ, kg m-3

25000
24000

rotational axis

This Work(ADL)

23000

(b)

22000

21000
20000
(c)

19000
18000

Ishikawa et al.,ESL
Watanabe et al.,EML

17000
1500

2000

2500

3000

1mm

Temperature, T, K
Figure.2 Density of liquid platinum results for different droplet shapes.
2 of 3References1)
2)

T. Ishikawa, P. F. Paradis, and N. Koike. Non-contact thermophysical property measurements of liquid andsupercooled platinum. J. Appl. Phys, 45 (2006) 1719, DOI: https://doi.org/10.1143/JJAP.45.1719
M. Watanabe, M. Adachi, and M. Uchikoshi, H. Fukuyama.: Densities of Pt-X(X: Fe, Co, Ni and Cu) binary melts andthermodynamic correlations. Fluid Phase Equilib, 515 (2020) 1, DOI: https://doi.org/10.1016/j.fluid.2020.112596© 2023 by the authors. Submitted for possible open access publication under theterms and conditions of the Creative Commons Attribution (CC BY) license(http://creativecommons.org/li censes/by/4.0/

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