Photon Factory Activity Report 2014 #32 (2015) B

BL-4C/2014G117

X-ray Crystal Truncation Rod Measurements ofCalcite/Water Interfaces at Elevated Temperature
Hiroshi Sakuma1,* Henning O. Sørensen2, Jun Kawano3, Naoki Nishiyama1, and Hironori Nakao4
1
National Institute for Materials Science, Tsukuba 305-0044, Japan
2
University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark3
Hokkaido University, N21 W10 Kitaku, Sapporo, Hokkaido 001-0021, Japan
4
Condensed Matter Research Center and Photon Factory, Tsukuba 305-0801, Japan
1 Introduction
The structure of mineral/liquid interfaces can be
modified at elevated temperatures by adsorption ofdissolved ions on the mineral surface. Structural changes
may alter the wettability of mineral surfaces from water
wet to oil wet [1], and are therefore especially importantfor enhanced oil recovery. We have determined thestructure of mineral/liquid interfaces using the technique
X-ray crystal truncation rod (CTR) scattering. Thismethod is a powerful tool for observing the electron
density profile vertical to the interface.
In this study we measured the CTR profiles of thecalcite {10.4} surface in a NaCl solution at 298 and 358
K. Calcite (CaCO3) is the main constituent of chalk andother limestone rocks.
2 Experiment
Calcite spar single crystals were cleaved prior to themeasurements and were immediately immersed in CaCO3
saturated 0.5 M NaCl aqueous solution for a few hours.
The liquid was degassed before the measurements toavoid bubble formation in the sample cell at elevatedtemperature. We have developed a thin-film sample cellfor controlling the temperature of the sample up to 373 K.
This cell reduced the evaporation of liquid compared toour previous sample cell [2]. The cell was covered using apolyimide film 7.5 μm thick to prevent the solution fromevaporating.
Specular X-ray CTR scattering measurements wereperformed at the BL-4C beamline at the Photon Factory,
KEK, Japan. A monochromatic X-ray beam of 11.0 keV
was used. The specular X-ray CTR profile was measured
for the natural cleavage plane {10.4}. The integrated andbackground corrected scattering intensities weresubsequently corrected for Lorentz, polarization,attenuation, area factors, and rod interception effect. Theintensities were converted to structure factors, |F|. Theanalysis was performed using in-house program based on
the ANA-ROD code [3].
3 Results and Discussion
The specular CTR profiles of calcite/0.5 M NaClsolution interface measured at 298 and 358 K are plottedin Fig.1. No significant difference can be seen between
the profiles determined at 298 and 358 K, indicating thatthe interfacial structure at 358 K was similar to the one at
298 K. This is consistent with the experimental results,

where no difference in oil recovery was found by theimbibition of NaCl solution into a porous chalk rock [4].
Our results also imply that the sample cell can holdaqueous solution during the CTR measurements atelevated temperature.
The effect of temperature under various salt
concentrations and chemical compositions will be
investigated using this sample cell in future experiments.

Fig. 1: Specular X-ray CTR profiles of calcite/0.5 M
NaCl solution interface at 298 and 358 K.
Acknowledgement
This research was partially supported by a Grant-inAid for Young Scientists (B) (23740390) from theMinistry of Education, Culture, Sports, Science andTechnology (MEXT), Japan.
References[1] H. Sakuma, M. P. Andersson, K. Bechgaard, and S. L.
S. Stipp, J. Phys. Chem. C 118, 3078 (2014).
[2] H. Sakuma et al., KEK Photon Factory Activity
Report 2013, #31 B (2014).
[3] E. Vlieg, J. Appl. Crystallogr. 33, 401 (2000).
[4] P. Zhang, M. T. Tweheyo, and T. Austad, Colloid surf.,
A 301, 199 (2007).
* SAKUMA.Hiroshi@nims.go.jp