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
課題番号 Project No.

提出日 Date of Report
装置責任者 Name of responsible person

2014A0322

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
12 June 2014 – 15 June 2014

Shigeo Sasaki
所属 Affiliation
Dept. of Electrical, Electronic & Computer Engineering, 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 powder in a diamond anvil cell, CD4-nD2O
2. Fully deuterated methane hydrate powder in a sapphire anvil cell, CD4-nD2O
3. Vanadium bulk 1.5 mm x 2.0 mm, V
4. Vanadium bulk 1.5 mm x 1.5 mm, V
5. Vanadium rod 5 mm, V
6. NIST lanthanum hexaboride powder in V can, LaB6

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.

In the previous experiments (2012A0059, 2012B0223), we have carried out the high pressure neutron
diffraction measurements for fully deuterated methane hydrate (CD4-nD2O) and methane deuterohydrate(CH4-nD2O), in order to determine the cage occupancy of methane molecules in the large water cage of structure
H (sH) methane hydrate. Although we obtained the excellent and unprecedented neutron powder diffraction
pattern up to 5 Å in d-value for sH phase of CD4-nD2O, the existence of diffractions of ice-VI which invariably
appears at the sI to sH phase transformation disturbed the detailed Rietveld analysis. The aim of this continuing
proposal is, therefore, to obtain the neutron diffraction pattern of ice-VI-free sH CD4-nD2O and to determine theprecise storage capacity of methane molecules in the large cage of sH by fully utilizing the advantages of highresolution and low background of BL19 “TAKUMI”. In addition, the results of the proposed experiments willcontribute to the more detailed Rietveld analysis for the neutron diffraction patterns previously obtained at“TAKUMI”.
In this experiment, we prepared two CD4-nD2O samples as follows: (a) D2O ice powder with ~5 μm in
diameter was put into a sample chamber (2.0 mm x 1.5 mm) of a diamond anvil cell (DAC) (Fig. 1), and then12. 実験方法及び結果（つづき） Experimental method and results (continued)
liquefied deuterated methane (CD4) was loaded into the chamber byspraying CD4 gas on it cooled at ~80 K near the liquid nitrogentemperature. The sH CD4-nD2O was synthesized at 1 GPa and room
temperature over several days, and then was pressurized up to 1.65
GPa. (b) The sI CD4-nD2O powder and liquid CD4 were loaded intoa sample chamber (2.0 mm x 2.0 mm) of a sapphire anvil cell(SAC) in the same manner of (a). After loading, the sample waswarmed to room temperature and was pressurized up to 1.30 GPa.
The high intensity mode Neutron diffraction measurements were
performed for the above two samples of sH CD4-nD2O at“TAKUMI”, using the focusing device and the 2 mm radial

Fig. 1. Diamond anvil cell (DAC)
including fully deuterated methane
hydrate powder at TAKUMI.

collimator. Figure 2 shows the obtained diffraction patterns as afunction of TOF, which are roughly normalized by the incoherent scattering spectrum from V-Ni rod (5 mm).
The intensities of the diffraction peaks from ice-VI are obviously diminished in comparison with the previousresults. Especially for the sample (CD4-nD2O + liq. CD4) in SAC [Fig. 2 (b)], we can estimate the pure
diffraction peaks from sH CD4-nD2O by comparing with the previous experiments, because the peaks fromice-VI are very weak. However, we could not fully remove the ice-VI peaks. Moreover, the very broad peakwhich probably comes from liquid CD4 appears at around 47000 s. These results suggest that the excess water
generated at the sI to sH transformation of CD4-nD2O does not sufficiently react with liquid CD4 at ~1.3 GPa
within several days.
Furthermore, the neutron diffraction measurements for NIST LaB6 powder in V can, vanadium bulk chips,and empty anvil cells were also performed for the d-value calibration, normalizing the intensity of diffraction
patterns, and the absorption and background corrections for anvils, gaskets, and other surroundings. The
Rietveld analysis of guest methane storage capacity in large cages of sH CD4-nD2O is now in progress, taking
account of the above calibrations and the previous neutron diffraction patterns.

CD4-nD2O sH in DAC

Intensity (arb. unit)

P = 1.65 GPa
Date : 2014.6.12
Double frame
Proton beam power = 300 kW
Accumulation time = 5 h

Ice VIAldiamond

30000

40000

50000

60000

CD4-nD2O sH in SAC(b)P = 1.30 GPaDate : 2014.6.12
Double frame
Proton beam power = 300 kW
Accumulation time = 8.5 h

Intensity (arb. unit)

(a)

70000

Ice VI
Al
Al2O3

30000

TOF (us)

40000

50000

60000

70000

TOF (us)Fig. 2. Neutron powder diffraction patterns of fully deuterated methane hydrate (CD4-nD2O) (a) in a diamondanvil cell (DAC) at P = 1.65 GPa and (b) in a sapphire anvil cell (SAC) at P = 1.30 GPa. Blue, grey, green, andred solid circles stand for the diffraction peaks from ice-VI, aluminum gasket, diamond anvils, and sapphireanvils, respectively.

2