Document Type
Thesis
Abstract
This study obtained data by using micro-Raman spectroscopy and synchrotron radiation based techniques to evaluate the effect of NaCl on the bonding structure and unit cell parameters of Ice VII up to 20 GPa. Although physical properties of Ice VII have been studied in depth, no data is presently available on how salts are incorporated in the structure of Ice VII, which could have potential implications in the modeling of planetary interiors. Raman spectroscopy was used to analyze samples of pure H2O, 5 wt% NaCl, and 15 wt% NaCl at pressures from 3-20 GPa at increments of 1-2 GPa. The relative OH stretching frequency of Ice VII was measured to observe the bond structure in Ice VII formed from the NaCl-H2O solutions at set pressure intervals. All results show a negative linear decrease in OH stretching frequency as pressure increases. Ice VII formed from pure water and the 5 wt% NaCl solution have a similar slope of approximately —-23 cm’'/GPa while the Raman shift is systematically 15 rel cm’! higher for 5 wt% NaCl for each pressure reading. The 15 wt% NaCl-H20 solution shows larger variations that are difficult to interpret with the present data. Synchrotron-based X-ray diffraction patterns, obtained with the Advanced Photon Source at Argonne National Laboratory, were used to obtain unit cell volume parameters for Ice VII formed from 5 and 10 wt. % NaCl solutions. The diffraction data indicate that the Ice VII formed from a 5 wt.% NaCl-H2O solution has a unit cell volume that is systematically depressed at any given pressure relative to the volume of Ice VII formed from pure H,O. The incorporation of NaCl into Ice VII decreases the measured volume relative to “pure” Ice VII, thereby increasing the density of Ice VII formed from NaCl rich solutions. A zero-pressure volume, bulk modulus, and pressure derivative were calculated from this data and compared with pure Ice VII data reported by Frank et al. (2004). The 5 wt% NaCl-solution yielded a bulk modulus of 23.6 + 1.2 GPa in comparison to 21.3 + 1.3 GPa calculated by Frank et al. (2004). An increase in bulk modulus with the addition of 5 wt% NaCl into Ice VII verifies that the incorporation of NaCl results in a density increase and an effective stiffening of the Ice VII structure. The 10 wt% NaCl-solution produced largely variable results that are difficult to interpret and compare with the behavior of Ice VII over this pressure range.
Date Awarded
2004
Department
Geology
Recommended Citation
Runge, Claire Elizabeth, "Determining the Incorporation of NaCl into Ice VII by Raman Spectroscopy and Synchrotron Radiation" (2004). Geology Senior Theses. William & Mary. Paper 140.
https://scholarworks.wm.edu/geologyseniors/140
