X-ray diffraction and ice nucleation studies of AgIAgCl solid solutions

Ice nucleation efficiency of AgI: review and new insights

“…Experiments with AgI yielded a freezing temperature of 270.62 K and a lattice match of 1.77 %. AgCl has a large misfit of 12.86 %; never-theless, nucleation was observed at a threshold temperature of 269.13 K (Palanisamy et al, 1986a). A superior ice nucleation ability of AgI-AgCl compared with AgI particles has also been observed by DeMott (1995) for experiments in the Colorado State University (CSU) isothermal cloud chamber.…”

“…While freezing occurred with an average nucleation time of 1 s at 264 K, it took more than 10 000 s to nucleate the sample at 270 K. This shows the stochastic nature of ice nucleation and that nucleation time has to be considered together with freezing temperature and surface area for comparisons between different studies. Palanisamy et al (1986a) investigated bulk samples in test tubes cooled at a rate of 0.1 K min −1 and observed freezing of pure AgI particles at 270.62 K and freezing of AgI-AgCl cubic solid solutions at an even higher temperature of 271.97 K. Davis et al (1975) reported freezing of water in contact with 3AgI q NH 4 I q 6H 2 O films at 272 K compared with freezing at 269 K for AgI films. Nagare et al (2015Nagare et al ( , 2016 presented contact freezing experiments performed with the ETH CoLlision Ice Nucleation CHamber (CLINCH) using 80 µm diameter droplets, which were exposed to 200 nm and 400 nm diameter AgI particles.…”

“…Namely, heterogeneous ice nucleation on films of this compound occurred at 272 K for 3AgI q NH 4 I q 6H 2 O compared with 269 K for AgI. Palanisamy et al (1986a) determined ice nucleation threshold temperatures of bulk samples of AgI-AgCl solid solutions with different AgI : AgCl mixing ratios and compared them with lattice constants from X-ray powder diffraction. The 65 : 35 mol % combination of AgI and AgCl showed the best lattice match of 0.44 % and the highest nucleation temperature of 271.97 K in bulk experiments.…”

“…Coprecipitation with AgBr and AgCl leads to a contraction of the AgI lattice due to the smaller ionic radii of Br − and Cl − ions compared with I − (Vonnegut and Chessin, 1971;Palanisamy et al, 1986a, b). X-ray powder diffraction of AgI-AgCl solid solutions has shown that even small impurities with AgCl lead to cubic solid solutions (Palanisamy et al, 1986a). In the presence of ammonium, the complex compound 3AgI q NH 4 I q 6H 2 O may form, which has a better epitaxial fit with respect to ice than has silver iodide.…”

Synthesis of AgIAgClCuI solid solutions for ice nucleation studies

“…It is reported PALANISAMY et al 1986c) that at room temperature the "AgI-CuI" and "Aig-AgCl" systems form cubic solid solutions. Hence, it is expected that the AgI-AgCl-CuI system may also form continuous solid solutions.…”