PS23
3 方向ノズルを用いたガスジェット浮遊法によるPt 融体の高精度密度計測
High-Precision Density Measurement of Molten Pt
Using Aerodynamic Levitation Method with a ThreeDirectional Nozzle
加藤蒼 1, 高橋勇太 1, 清宮優作 1, 白鳥英 2, 小畠秀和 3, 杉岡健一 4, 石川毅彦 5, 小澤俊平 1
So KATO1, Yuta TAKAHASHI1, Yusaku SEIMIYA1, Suguru SHIRATORI2, Hidekazu KOBATAKE3
Ken-ichi SUGIOKA4, Takehiko ISHIKAWA5, and Shumpei OZAWA1
千葉工業大学， Department of Advanced Materials Science and Engineering, Chiba Institute of Technology
東京都市大学， Department of Mechanical Systems Engineering, Tokyo City University
3 同志社大学， Organization for Research Initiatives & Development, Doshisha University
4 富山県立大学，Department of Mechanical Systems Engineering, Toyama Prefectural University
5 JAXA，Institute of Space and Astronautical Science, JAXA
121Introduction
Accurate and precise measurements of the density of high-temperature melts are crucial for simulating phase transitions,such as crystallization and vitrification. These values serve as fundamental ordering parameters. To avoid sample
contamination from the container during density measurements, containerless techniques such as electrostatic levitation(ESL) and electromagnetic levitation (EML) are commonly employed. However, ESL faces challenges with high-vaporpressure samples due to its requirements for high-vacuum conditions. Meanwhile, EML can only be used with conductive
samples and necessitates the application of a strong static magnetic field to a levitated droplet to suppress its deformation.
In the present study, we employed an aerodynamic levitation (ADL) to control the rotation of levitated droplets using
three different gas jet nozzles: a standard conical nozzle (SCN), a tri-directional converging nozzle (TDCN) and a tridirectional non-intersecting nozzle (TDNIN). The aim of this study was to develop and establish a novel method formeasuring the density of high-temperature melts using ADL.

2Experimental procedure

Figure 1 shows schematics of the three types of gas jet nozzles(SCN, TDCN, and TDNIN) used in this study. In the TDCN
(Fig. 1 (b)), three gas jets converge into a single point at thetop of the nozzle, levitating a droplet at this convergence. Inthe TDNIN (Fig. 1 (c)), the three gas jets do not directlyintersect, creating a valley between the gas jets where a droplet
is levitated.

Gas(a) SCN(b) TDCN(c) TDNIN

Fig.1 Schematic diagram of the gas jet nozzle
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To eliminate the effects of oxidation and adsorption of the sample by atmospheric oxygen, chemically stable platinum
was selected as the sample in this study. A spherical sample with a diameter of 1.6 to 2.0 mm was placed on the nozzle
and levitated using argon gas jets. A semiconductor laser beam was irradiated from above to heat and melt the sample.
The sample temperature was recorded with a monochromatic pyrometer. The sample image was continuously observedfrom the horizontal direction using a high-speed video camera (1000 fps for 5 seconds) in conjunction with temperature.
The rotation axis of the droplet was confirmed using aluminum powder as a tracer. To determine the accurate sample
contour, backlight from a semiconductor laser was employed along with a high-pass filter placed in front of the camera.
The volume of the droplet was calculated from each numerically fitted contour, assuming rotational symmetry. The
density of the droplet was calculated by dividing the sample mass, measured after the experiment, by its calculated volume.

3Results and discussion
When observing a levitated droplet with the SCN from the(a) SCN(b) TDCN

ZZ(c) TDNIN
Z

horizontal direction, the nozzle obscures almost the entire
bottom half of the droplet, as shown in Fig.1 (a). The droplet
wasobserved

rotatinghorizontally,

asYY

X

Y

X

X

schematically
Horizontal Axis

Horizontal Axis
+Yawing

illustrated in Fig. 2 (a).
0sWith the TDCN, the visible area of the droplet is increased,
as shown in Fig. 2 (b). Furthermore, the droplet was rotatedChangeovertime0s

X

Using the TDNIN, the visible area of the droplet is0ºZ

XY

X

Different shape90º

X

Different shapeX

Same shape0º90º

Z

Z

ZXs
ZX

Different shape90º

Z0sZX

X

0ºChangewithangle

Xs
ZZ

Z

Same shapequickly horizontally and slowly vertically at the same time as
schematically in Fig. 2 (b).

Xs

Z

Virtical Axis

ZY

X

Y

Different shapeFig.2 Shape change of a rotating droplet

significantly increased; only 6 % of the projection area isobscured by the nozzle. Moreover, the rotation of the droplet could be controlled only around the vertical axis.
Figure 3 illustrates the relationship between the calculated

at 2000 K. The volume of the levitated droplets using the SCNand TDNIN was calculated assuming rotational symmetryaround their respective axes; it is the horizontal axis for theSCN sample and the vertical axis for the TDNIN sample. For
the droplet levitated using the TDCN, the volume wascalculated under the assumption of symmetry around thehorizontal axis, reflecting its rapid rotation.

Density ρ, kg・m-3density and the elapsed time for platinum droplets maintained

20000

TDCN

19500

2150±40 K

TNDIN

19000
18500

Ishikawa et al_ESL

18000

SCN

17500
17000

0123Time t, s

45Fig.3 The relationship between the density of a Ptdroplet and elapsed time

The calculated density of the droplets using the SCN
remains comparatively constant, regardless of the elapsed time. However, it is lower than the data reported by Ishikawa
et al. using the ESL technique. This discrepancy could be attributed to the limited visible area of the droplet, potentiallyleading to inaccuracies in determining the correct contour of the droplet image.
The calculated density of the droplet using the TDCN gradually decreases over time until the levitation time reaches
3.8 seconds, after which it begins to increase. This trend correlates with variation in the apparent volume of the droplet
due to its slow vertical rotation co-existing with its rapid horizontal rotation. The slow vertical rotation causes the apparent
volume of the droplet to oscillate slowly when assuming only horizontal symmetry.
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When using the TDNIN, the calculated density of the droplet aligns well with the data by Ishikawa et al. This is attributed
to the significantly enlarged visible area and the controlled rotation axis on the vertical. A small oscillation of thecalculated results at 5 Hz was attributed to a translational oscillation of the levitated droplet. The droplet image appears
smaller or larger as it moves away from or closer to the HSV camera.
From these results, it is clear that the method for measuring the density of high-temperature melts using AerodynamicLevitation (ADL) with the tri-directional non-intersecting nozzle (TDNIN) has been successfully developed andestablished.

4Summary

This study explores the development of a novel method for measuring the density of high-temperature melts using
Aerodynamic Levitation (ADL) with three different gas jet nozzles: a standard conical nozzle (SCN), a tri-directional
converging nozzle (TDCN), and a tri-directional non-intersecting nozzle (TDNIN). Experiments conducted withchemically stable platinum samples revealed that while the SCN and TDCN had limitations in terms of visible area androtational dynamics affecting density measurements, the TDNIN showed significant improvements. It provided a larger
visible area and controlled rotation, resulting in density measurements that aligned well with established data.

Acknowledgement
This research was partially funded by the Japan Society for the Promotion of Science (JSPS) KAKENHI
under Grant No. P20H02453, and by the Grant-in-Aid for Front Loading Research, which is supported by theAdvisory Committee for Space Utilization Research in the Institute of Space and Astronautical Science, Japan
Aerospace Exploration Agency (ISAS/JAXA).

References1)

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© 2024 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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