scholarly journals Effect of Graphene on Ice Polymorph

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1134
Author(s):  
Chuanbao Zheng ◽  
Hao Lu ◽  
Quanming Xu ◽  
Tianyi Liu ◽  
Aniruddha Patil ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Heterogeneous Nucleation ◽  
Lattice Structure ◽  
Primary Source ◽  
Freezing Process ◽  
Free Energy Barrier ◽  
Dynamic Simulations ◽  
Basal Face ◽  
Hexagonal Ice ◽  
Ice Nuclei

Recently, ice with stacking disorder structure, consisting of random sequences of cubic ice (Ic) and hexagonal ice (Ih) layers, was reported to be more stable than pure Ih/Ic. Due to a much lower free energy barrier of heterogeneous nucleation, in practice, the freezing process of water is controlled by heterogeneous nucleation triggered by an external medium. Therefore, we carry out molecular dynamic simulations to explore how ice polymorphism depends on the lattice structure of the crystalline substrates on which the ice is grown, focusing on the primary source of atmospheric aerosols, carbon materials. It turns out that, during the nucleation stage, the polymorph of ice nuclei is strongly affected by graphene substrates. For ice nucleation on graphene, we find Ih is the dominant polymorph. This can be attributed to structural similarities between graphene and basal face of Ih. Our results also suggest that the substrate only affects the polymorph of ice close to the graphene surface, with the preference for Ih diminishing as the ice layer grows.

scholarly journals Effect of Graphene on Ice Polymorph

2021 ◽  
Author(s):  
Chuanbao Zheng ◽  
Hao Lu ◽  
Quanming Xu ◽  
Tianyi Liu ◽  
Aniruddha Patil ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Lattice Structure ◽  
Freezing Process ◽  
Free Energy Barrier ◽  
Dynamic Simulations ◽  
Nucleation Stage ◽  
Basal Face ◽  
Hexagonal Ice ◽  
Ice Nuclei ◽  
Stacking Disorder

Recently, ice with the stacking disorder structure, consisting of random sequences of cubic ice (Ic) and hexagonal ice (Ih) layers, is reported to be more stable than pure Ih/Ic. While, due to a much lower free energy barrier of heterogeneous nucleation, in practice, the freezing process of water is usually controlled by heterogeneous nucleation which is triggered by an external medium. Herein, molecular dynamic simulations were carried out to explore the polymorph dependence of ice on the lattice structure of substrates. It turns out that, during the nucleation stage, the polymorph of ice nuclei can be severely altered by the graphene substrate, on which the Ih was found to occupy an absolute majority in new-formed ice. This can be attributed to the structure similarity between graphene and basal face of Ih. Besides the nucleation stage, our results suggest that the substrate can not affect the polymorph of ice which is far from the graphene surface. The polymorph selectivity of graphene to Ih will diminish with the growth of ice layer.

scholarly journals Growth of atmospheric nano-particles by heterogeneous nucleation of organic vapor

2013 ◽  
Vol 13 (13) ◽  
pp. 6523-6531 ◽  
Author(s):  
J. Wang ◽  
R. L. McGraw ◽  
C. Kuang
Keyword(s):  
Atmospheric Aerosols ◽  
Heterogeneous Nucleation ◽  
Particle Formation ◽  
Nano Particles ◽  
High Rate ◽  
Vapor Concentration ◽  
Strong Increase ◽  
Initial Growth ◽  
New Particle Formation ◽  
Cluster Number

Abstract. Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosols is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (~3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here, the contribution of organics to the initial cluster growth is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size leads to positive cluster number flux. This positive flux drives the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered the minimum particle size that can be grown through condensation. The conventional approach neglects the contribution from the cluster concentration gradient, and underestimates the cluster survival probabilities by a factor of up to 60 if early growth of clusters is due to both condensation of sulfuric acid and heterogeneous nucleation of organic vapors.

scholarly journals Identification of secondary fatty alcohols in atmospheric aerosols in temperate forests

2019 ◽  
Vol 16 (10) ◽  
pp. 2181-2188
Author(s):  
Yuzo Miyazaki ◽  
Divyavani Gowda ◽  
Eri Tachibana ◽  
Yoshiyuki Takahashi ◽  
Tsutom Hiura
Keyword(s):  
Atmospheric Aerosols ◽  
Deciduous Forest ◽  
Growing Season ◽  
Fatty Alcohols ◽  
Forest Site ◽  
Cloud Droplets ◽  
Ice Nuclei ◽  
Forest Sites ◽  
Molecular Tracer ◽  
First Time

Abstract. Fatty alcohols (FAs) are major components of surface lipids (waxes) and can act as surface-active organic aerosols in the atmosphere, influencing chemical reactions, particle lifetimes, and the formation of cloud droplets and ice nuclei. However, studies on the composition and source of the FAs in atmospheric aerosols are very limited. In this study, we identified five secondary FAs (SFAs) with C27 and C29 from aerosol samples collected throughout 1 year at two different deciduous forest sites in Japan. Fatty diols, such as n-heptacosan-5,10-diol, were identified in atmospheric aerosols for the first time. Among the identified SFAs, n-nonacosan-10-ol was the most abundant compound, followed by n-nonacosan-5-10-diol at both of the forest sites. Concentrations of the SFAs exhibited distinct seasonal variation, with pronounced peaks during the growing season at each forest site. The SFAs showed significant correlation with sucrose, which is used as a molecular tracer of pollen. A significant fraction of the SFAs was attributed to the submicrometer particles in the growing season. The results indicate that they originated mostly from plant waxes and could be used as useful tracers for primary biological aerosol particles.

Lignin's ability to nucleate ice via immersion freezing

2020 ◽  
Author(s):  
Sophie Bogler ◽  
Nadine Borduas-Dedekind
Keyword(s):  
Structural Changes ◽  
Dominant Role ◽  
Mixed Phase ◽  
Freezing Process ◽  
Radiative Balance ◽  
Ice Nuclei ◽  
Atmospheric Processing ◽  
Immersion Freezing ◽  
Mixed Phase Clouds ◽  
The Impact

<p>Uncertainties in current predictions for the atmosphere’s radiative balance are dominated by the impact of clouds. Ice nucleating particles (INPs) play a dominant role in the formation of mixed-phase clouds, however there is still a lack of understanding of how INPs interact with water in the freezing process. Detailed elucidations of the organic aerosol chemical composition from IN active atmospheric samples are scarce which is due to the analytical challenge of resolving their high complexity. We chose to reduce sample complexity by investigating the IN activity of a specific sub-component of organic aerosols, the biopolymer lignin. This approach facilitates connecting ice nucleating abilities to molecular properties. Ice nucleation experiments were conducted in our home-built Freezing Ice Nuclei Counter (FINC) to measure freezing temperatures in the immersion freezing mode which is the dominant IN mechanism in mixed-phase clouds. We find that lignin acts as an INP at temperatures relevant for mixed-phase cloud processes (e.g. 50% activated fraction at – 20 °C concentrated 20 mg C/L). Photochemistry and ozonation experiments were subsequently conducted to test the effect of atmospheric processing on lignin’s IN activity. We discovered that this activity was not susceptible to change under environmentally relevant conditions even though structural changes were introduced by monitoring UV/Vis absorbance. Additionally to atmospheric processing, laboratory treatments including heating, sonication and oxidation with hydrogen peroxide were done, where only the heating experiments had a decreasing effect on lignin’s IN activity.  Based on these results, we present a thorough INP characterization of lignin, a specific organic matter subcomponent, and contribute to the understanding of how organic material present in the atmosphere can nucleate ice.</p>

Heterogeneous nucleation on rough surfaces: implications to atmospheric aerosols

2000 ◽  
Vol 55 (2) ◽  
pp. 103-113 ◽  
Author(s):  
Mihalis Lazaridis ◽  
Øystein Hov ◽  
Kostas Eleftheriadis
Keyword(s):  
Atmospheric Aerosols ◽  
Heterogeneous Nucleation ◽  
Rough Surfaces

Heterogeneous nucleation capability of conical microstructures for water droplets

RSC Advances ◽  
2015 ◽  
Vol 5 (2) ◽  
pp. 812-818 ◽  
Author(s):  
Wei Xu ◽  
Zhong Lan ◽  
Benli Peng ◽  
Rongfu Wen ◽  
Xuehu Ma
Keyword(s):  
Free Energy ◽  
Nucleation Rate ◽  
Heterogeneous Nucleation ◽  
Energy Barrier ◽  
Free Energy Barrier ◽  
Water Droplets

Micro cavities with narrower cone angles can reduce the free energy barrier and improve the nucleation rate of water droplets.

Frost Heave and Water Uptake Relations in Variably Saturated Aggregate Base Materials

2003 ◽  
Vol 1821 (1) ◽  
pp. 13-19 ◽  
Author(s):  
W. Spencer Guthrie ◽  
åke Hermansson
Keyword(s):  
Base Material ◽  
Primary Source ◽  
Frost Heave ◽  
Soil Conditions ◽  
Freezing Process ◽  
Freezing Front ◽  
Base Materials ◽  
Additional Water ◽  
Initial Freezing ◽  
Aggregate Base

The occurrence of frost heave in soils and aggregates can be attributed to the redistribution of water in the soil profile. Frost heave testing performed in this study on 71 variably saturated specimens of aggregate base material indicates that although the uptake of new water from outside the soil body is a primary source of moisture in the formation of segregation ice, internal water residing within the soil or aggregate structure can serve as an important supply of water to the freezing front. Frost heave concepts relating to unsaturated soil conditions were reviewed, and a laboratory methodology was employed to study the relationships between the physical properties of the specimens and their frost heave behavior. Degrees of saturation ranging from 45% to 84% were evaluated, and heave–uptake ratios as high as 2.24 were calculated. Ratios less than 1.09 suggest that sufficient porosity exists in the sample matrix to allow the formation of ice without causing frost heave; higher ratios designate samples that are nearly saturated and that undergo substantial upward redistributions of existing water during the initial freezing process, which gives rise to measurable heave even before additional water is imbibed by the sample. The entry of air into freezing soils and aggregates can play an important role in their frost heave behavior.

scholarly journals A Novel 2D Model for Freezing Phase Change Simulation during Cryogenic Fracturing Considering Nucleation Characteristics

2020 ◽  
Vol 10 (9) ◽  
pp. 3308
Author(s):  
Chengyu Huang ◽  
Wenhua Wang ◽  
Weizhong Li
Keyword(s):  
Multiphase Flow ◽  
Phase Change ◽  
Heterogeneous Nucleation ◽  
Initial Distribution ◽  
Freezing Process ◽  
Computational Domain ◽  
Comparison Results ◽  
Fracturing Process ◽  
Cryogenic Fracturing ◽  
Ice Phase

A 2D computational fluid dynamics (CFD) model in consideration of nucleation characteristics (homogeneous/heterogeneous nucleation) using the volume of fluid (VOF) method and Lee model was proposed. The model was used to predict the process of a multiphase flow accompanied by freezing phase change during cryogenic fracturing. In this model, nucleation characteristic (homogeneous and heterogeneous nucleation) during the freezing process and the influence of the formed ice phase on the flowing behavior was considered. Validation of the model was done by comparing its simulation results to Neumann solutions for classical Stefan problem. The comparison results show that the numerical results are well consistent with the theoretical solution. The maximum relative differences are less than 7%. The process of multiphase flow accompanied by the freezing of water was then simulated with the proposed model. Furthermore, the transient formation and growth of ice as well as the evolution of temperature distribution in the computational domain was studied. Results show that the proposed method can better consider the difference between homogeneous nucleation in the fluid domain and heterogeneous nucleation on the wall boundary. Finally, the main influence factors such as the flow velocity and initial distribution of ice phase on the fracturing process were discussed. It indicates that the method enable to simulate the growth of ice on the wall and its effect on the flow of multiphase fluid.

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