Evaluation of data for ice formed from pure water and analysis of ice crystal structures in crystallized fructose aqueous solutions

Abstract

X-ray diffraction (XRD) patterns of hexagonal ice (I_h) and/or stacking-disordered ice (I_sd) have been observed for ice formed in various aqueous systems. Ice I_h and ice I_sd exhibit a diffraction peak at XRD angle of 2θ ≈ 40 deg, but I_h uniquely shows additional peaks at 2θ ≈ 34 deg and 44 deg, which are absent in ice I_sd. We consider that the XRD peak areas at 34, 40, and 44 deg in crystallized aqueous solution can be utilized to estimate the fraction of ice I_h and ice I_sd in crystallized aqueous solutions. To analyze the crystal structure of ice in aqueous solutions, X-ray diffraction measurements of ice formed from pure water as a reference of ice I_h were conducted at 213 K and 188 K at various cooling rates in a range of 0.67 − 150 K/min. Assuming that the ice from pure water is the ice I_h, and variation of the peak areas at 2θ ≈ 34, 40, and 44 deg were evaluated. X-ray diffraction measurements were conducted on crystallized fructose aqueous solutions with fructose concentrations of 20 and 40 wt.%. Based on the results of pure water ice, ice in the fructose aqueous solutions up to 40 wt.% of fructose were identified as ice I_h.