@article {2064,
	title = {Ice nucleation on mineral dust particles: Onset conditions, nucleation rates and contact angles},
	journal = {Journal of Geophysical Research-Atmospheres},
	volume = {113},
	year = {2008},
	note = {ISI Document Delivery No.: 375WPTimes Cited: 16Cited Reference Count: 62Eastwood, Michael L. Cremel, Sebastien Gehrke, Clemens Girard, Eric Bertram, Allan K.},
	month = {Nov},
	pages = {9},
	type = {Article},
	abstract = {An optical microscope coupled to a flow cell was used to investigate the onset conditions for ice nucleation on five atmospherically relevant minerals at temperatures ranging from 233 to 246 K. Here we define the onset conditions as the humidity and temperature at which the first ice nucleation event was observed. Kaolinite and muscovite were found to be efficient ice nuclei in the deposition mode, requiring relative humidities with respect to ice (RHi) below 112\% in order to initiate ice crystal formation. Quartz and calcite, by contrast, were poor ice nuclei, requiring relative humidities close to water saturation before ice crystals would form. Montmorillonite particles were efficient ice nuclei at temperatures below 241 K but were poor ice nuclei at higher temperatures. In several cases, there was a lack of quantitative agreement between our data and previously published work. This can be explained by several factors including the mineral source, the particle sizes, the surface area available for nucleation, and observation time. Heterogeneous nucleation rates (J(het)) were calculated from the measurements of the onset conditions (temperature and RHi) required from ice nucleation. The Jhet values were then used to calculate contact angles (theta) between the mineral substrates and an ice embryo using classical nucleation theory. The contact angles measured for kaolinite and muscovite ranged from 6 degrees to 12 degrees, whereas for quartz and calcite, the contact angles ranged from 25 degrees to 27 degrees. The reported Jhet and q values may allow for a more direct comparison between laboratory studies and can be used when modeling ice cloud formation in the atmosphere.},
	keywords = {AFRICAN DUST, AMMONIUM-SULFATE PARTICLES, CIRRUS CLOUDS, CUBIC ICE, GENERATED LIQUID AEROSOLS, HETEROGENEOUS NUCLEATION, MICROPHYSICS, NUCLEI, SOOT, WATER},
	isbn = {0148-0227},
	url = {<Go to ISI>://000261144800007},
	author = {Eastwood, M. L. and Cremel, S. and Gehrke, C. and Girard, E. and Bertram, A. K.}
}
@article {2198,
	title = {Inhibition of solute crystallisation in aqueous H+-NH4+-SO42{\textendash}H2O droplets},
	journal = {Physical Chemistry Chemical Physics},
	volume = {10},
	number = {22},
	year = {2008},
	note = {ISI Document Delivery No.: 304MXTimes Cited: 7Cited Reference Count: 68Murray, Benjamin J. Bertram, Allan K.},
	pages = {3287-3301},
	type = {Article},
	abstract = {Ice clouds in the Earth{\textquoteright}s upper troposphere can form via homogeneous nucleation of ice in aqueous droplets. In this study we investigate the crystallisation, or lack of crystallisation, of the solute phase and ice in aqueous (NH4)(3)H(SO4)(2)/H2O and NH4HSO4/H2O droplets. This is done using in situ X-ray diffraction of emulsified solution droplets mounted on a cold stage. From the diffraction patterns we are able to identify the phases of crystalline solute and ice that form after homogeneous freezing in micrometer sized droplets. An important finding from this study is that crystallisation of the solute does not always occur, even when crystallisation is strongly thermodynamically favoured. The nucleation and growth of solute phase crystals becomes inhibited since the viscosity of the aqueous brine most likely increases dramatically as the brine concentration increases and temperature decreases. If ice nucleates below a threshold freezing temperature, the brine appears to rapidly become so viscous that solute crystallisation is inhibited. This threshold temperature is 192 K and 180 K, in ( NH4) 3H( SO4) 2 and NH4HSO4, respectively. We also speculate that the formation of cubic ice within a highly viscous brine blocks the solvent mediated cubic to hexagonal phase transformation, thus stabilising the metastable cubic ice in the most concentrated solution droplets.},
	keywords = {CUBIC ICE, GLASS-TRANSITION, H2SO4/NH3/H2O AEROSOL-PARTICLES, HOMOGENEOUS ICE NUCLEATION, LIQUID WATER, LOW-TEMPERATURES, NH4HSO4, PHASE-TRANSITIONS, solutions, SULFURIC-ACID, SUPERCOOLED WATER},
	isbn = {1463-9076},
	url = {<Go to ISI>://000256114700013},
	author = {Murray, B. J. and Bertram, A. K.}
}
