PS18
音波浮遊法を用いた濃厚電解質の X 線解析
X-ray analysis of concentrated electrolytes using thesonic levitation method
家後賢太郎 1, 對馬和音 1, 正木匡彦 1,Kentaro YAGO1, Kazune TSUSHIMA1, Tadahiko MASAKI1
1

芝浦工業大学，Shibaura institute of technology,

1. Introduction
An acoustic levitation method is a non-contact method of levitating an object to a specific position byutilizing acoustic radiation pressure due to standing waves. It is suitable for handling highly corrosive liquidsamples such as concentrated electrolytes because it is not affected by the container. In this study, X-ray
analysis of water and concentrated electrolytes suspended by the acoustic levitation method was performed
to clarify the differences in liquid structure depending on the type and concentration of cations.
2. Experimental method
Water, sodium hydroxide solution, and potassium hydroxide solution were used as samples. Sodiumhydroxide solutions were prepared at molar ratios of H2O/NaOH = 1/0.2, 1/0.4, and 1/0.6, and potassiumhydroxide solutions were prepared at molar ratios of H2O/KOH = 1/0.1, 1/0.2, 1/0.3, and 1/0.4, respectively,and were suspended at 2 mm diameter via the acoustic levitator. This experiment was conducted using an Xray diffraction facility (RIGAKU RINT-2000) with the acoustic levitator of our own design. The Mo-K wasused as the X-ray source, and the diffraction angles were measured from 3° to 60° at intervals of 0.1°.
Corrections were made to the measured X-ray intensities for polarization and absorption factors, andnormalized to account for coherent and incoherent scattering factors. The normalized intensities were Fouriertransformed to derive a radial distribution function. The relationship between the absolute scattering intensity
required to obtain the interference function and the absolute scattering intensity is established in Equation 1.
𝛼𝑁 𝐼 𝑜𝑏𝑠 (𝑄)𝑐𝑜ℎ (𝑄)𝑖𝑛𝑐 (𝑄)
𝑚𝑢𝑙= 𝐼𝑒𝑢
+ 𝐼𝑒𝑢
+ 𝐼𝑒𝑢
(𝑄),
𝑃𝐴

(1)

Where 𝐴 is the absorption factor, 𝑃 is the polarization factor, and 𝛼𝑁 is the normalization constant. Theinterference function for the multicomponent system is shown in Equation 2.

𝑖(𝑄) =𝐼𝑒𝑢 /𝑁 − 〈𝑓 2 〉〈𝑓〉2(2)

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Figure 1. X-ray diffraction patterns of water and sodium hydroxide solution.

Figure 2. X-ray diffraction patterns of water and potassium hydroxide solutions.

Since the sample was a liquid, continuous and broad peaks were observed, unlike the sharp peaks observedin the crystalline system. In both water and sodium hydroxide solution, a shoulder was observed on the highangle side of the first peak. The peak position of sodium hydroxide solution was found to be shifted about 2°
to the high angle side compared to that of water. The amount of change in peak position for the potassiumhydroxide solution was smaller than that for the sodium hydroxide solution.

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Figure 3. RDF of water and sodium hydroxide solution.

Figure 4. RDF of water and potassium hydroxide solution.

The first peak appeared at 2.75 Å in the RDF of water. The first peak appeared at 2.6 Å in the RDF of sodiumhydroxide solution. The peak position of potassium hydroxide solution was the same as that of water.
4. Conclusion
Hydrogen atoms have electrons only in the 1s orbital, then the diffraction pattern cannot be obtained
because of the small scattering of X-rays. Therefore, the diffraction pattern of water provides only informationon oxygen. In solid ice, when we focus on oxygen, it forms a tetrahedron. Similarly, for silicon with tetrahedralstructure, it is known that a shoulder appears on the right side of the first peak 2). The first peak of the radial
distribution function of water is located very close to 2.76 Å 3), which is the distance between oxygen atoms insolid ice. Thus, the liquid structure of water indicates that the short-range order of solid state has remained. It
can be assumed that the peak position of the sodium hydroxide solution has changed due to the coordinationof the hydrated water to Na+. In the potassium hydroxide solution, the water of hydration is coordinatedaround K+ in the same way, but the peak position remains unchanged. This might be because the hydration
bonds around K+ are weaker than those around Na+ and did not affect the o-o distance.
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2)
3)

Yoshio Waseda and Eiichiro Matsubara : Materials Science Series X-ray Structure Analysis, Uchida Rokakuho, (1998)
Yoshio Waseda:THE STRUCTURE OF NON-CRYSTALLINE MATERIALS Liquids and Amorphous Solids,
McGraw-Hill Inc.(1980)p258
Saburo Nagakura : Structural Chemistry of Water, The chemical Society of Japan,11(1963)p377© 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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