実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF Experimental Report

提出日 Date of Report
11 May 2013

課題番号 Project No.

装置責任者 Name of responsible person

2012B0223

Kazuya Aizawa, Stefanus Harjo

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Guest storage capacity into dense methane hydrate

TAKUMI/BL19

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Shigeo Sasaki

28 Nov. 2012 – 1 Dec. 2012

所属 Affiliation
Dept. of Materials Science and Technology, Gifu University
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
1. Fully deuterated methane hydrate, CD4-nD2O in sapphire anvil cell
2. Methane deuterohydrate, CH4-nD2O in sapphire anvil cell
3. Vanadium rod, V
4. NIST alumina powder in V can, Al2O3

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

The aim of this continuing proposal is to measure the neurton diffraction of the structure H of methane
deuterohydrate (CH4-nD2O) and fully deuterated methane hydrate (CD4-nD2O) in order to find out the possible
structural difference (especially for the guest methane storage capacity in large cages) between the two methane
hydrate species by fully utilizing the advantages of high resolution and low background of BL19 “TAKUMI”.
Two kinds of methane hydrates were prepared by the following procedure. D2O ice powder with ~5 μm in
diameter was made by spraying water into a cooled chamber. This powder ice was put into a high pressure vessel
where CH4 or CD4 gas at 8 MPa was filled at 263 K. After ~20 hours, the powder ice almost transformed intostructure I hydrate (CH4-5.75 D2O or CD4-5.75 D2O). Then it was loaded into large sample chamber (1.5 mm x2.0 mm) of the anvil cell cooled at 80 K in order to prevent the grain growth. Structure H hydrate suitable forpowder diffraction was obtained by quick compression of the structure I hydrate into above the structure I structure H phase transformation pressure of 0.9 GPa while keeping the cell at low temperature. Due to increaseof methane capacity in dense hydrate, some D2O is segregated to form ice VI phase, which means that thespecimen of structure H methane hydrate is coexistent with ice VI.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
Neutron diffraction measurements were performed for the twostructure H methane hydrate samples (fully deuterated methane
hydrate: CD4-nD2O, methane deuterohydrate: CH4-nD2O) in thesapphire anvil cell prepared by the above procedure (Fig. 1), andwe successfully obtained their powder diffraction patterns.
Figures 2a and 2b show the obtained raw diffraction patterns as afunction of TOF for fully deuterated methane hydrate(CD4-nD2O) at P = 1.46 GPa, and methane deuterohydrate(CH4-nD2O) at P = 1.23 GPa, respectively. These diffraction
patterns show the very strong and sharp peaks of target methaneFig. 1. Sapphire anvil cell including
methane hydrate sample at TAKUMI.

hydrate samples. These peaks are obviously distinguishable fromthose of surrounding ice VI and aluminum gasket. In addition, the quality of these powder diffraction patterns
were confirmed by mapping spectra (Intensity-TOF-pixel). Although the incoherent scattering from 1H of CH4(Fig. 2b) affects the diffraction pattern of methane deuterohydrate, these fine diffraction patterns are thought tobe able to analyze the guest methane (CD4 or CH4) storage capacity in large cage of the structure H.

Fig. 2. Neutron powder diffraction patterns for a. fully deuterated methane hydrate (CD4-nD2O) at P = 1.46
GPa and b. methane deuterohydrate (CH4-nD2O) at P = 1.23 GPa. Solid circles and solid diamonds stand forthe peaks from aluminum gasket and ice VI, respectively.
Moreover, the neutron diffraction for a vanadium rod, NIST alumina powder in V can, and empty anvil cells
were also measured for normalizing the intensity of diffraction patterns, the d-value calibration, and theabsorption and background corrections for anvils, gaskets, and other surroundings. The Rietveld analysis ofguest methane storage capacity in large cages of the two kinds of structure H methane hydrates are now inprogress, taking account of the above calibrations.

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