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 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.

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 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.

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.

scholarly journals Sensitivity studies of dust ice nuclei effect on cirrus clouds with the Community Atmosphere Model CAM5

2012 ◽  
Vol 12 (24) ◽  
pp. 12061-12079 ◽  
Author(s):  
X. Liu ◽  
X. Shi ◽  
K. Zhang ◽  
E. J. Jensen ◽  
A. Gettelman ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Ice Nucleation ◽  
Number Concentration ◽  
Cirrus Clouds ◽  
Dust Aerosol ◽  
Global Perspective ◽  
Ice Crystal ◽  
Cloud Forcing ◽  
Ice Nuclei

Abstract. In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0 ± 0.1 W m−2 (1σ uncertainty) and 2.4 ± 0.1 W m−2, respectively due to the presence of dust IN, with the net cloud forcing change of −0.40 ± 0.20 W m−2. Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205–230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190–205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (> 200 L−1) and underestimate the frequency of low ice crystal number concentration (< 30 L−1) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 2: Nucleation of ice on synoptic scales

2013 ◽  
Vol 13 (21) ◽  
pp. 10769-10785 ◽  
Author(s):  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Temperature Fluctuations ◽  
Ice Nucleation ◽  
Solid Particles ◽  
Small Scale ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Ice Nuclei ◽  
Scale Temperature ◽  
Stratospheric Clouds

Abstract. This paper provides compelling evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (polar stratospheric clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~1000 km dimension). CALIPSO observations also showed widespread PSCs containing NAT (nitric acid trihydrate) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the entire Arctic winter 2009/2010.

scholarly journals Re-evaluating the Frankfurt isothermal static diffusion chamber for ice nucleation

2015 ◽  
Vol 8 (12) ◽  
pp. 12525-12557
Author(s):  
J. Schrod ◽  
A. Danielczok ◽  
D. Weber ◽  
M. Ebert ◽  
E. S. Thomson ◽  
...  
Keyword(s):  
Detection System ◽  
Diffusion Chamber ◽  
Free Energy Barrier ◽  
Initial Development ◽  
Spontaneous Nucleation ◽  
Ice Nuclei ◽  
Heterogeneous Formation ◽  
Ambient Measurements ◽  
Made In

Abstract. Recently significant advances have been made in the collection, detection, and characterization of ice nucleating particles (INP). Ice nuclei are particles that facilitate the heterogeneous formation of ice within the atmospheric aerosol by lowering the free energy barrier to spontaneous nucleation and growth of ice from atmospheric water and/or vapor. The Frankfurt isostatic diffusion chamber (FRIDGE) is an INP collection and offline detection system that has become widely deployed and shows additional potential for ambient measurements. Since its initial development FRIDGE has gone through several iterations and improvements. Here we describe improvements that have been made in the collection and analysis techniques. We detail the uncertainties inherent in the measurement method, and suggest a systematic method of error analysis for FRIDGE measurements. Thus what is presented herein should serve as a foundation for the dissemination of all current and future measurements using FRIDGE instrumentation.

scholarly journals Heterogeneous formation of polar stratospheric clouds – Part 2: Nucleation of ice on synoptic scales

2013 ◽  
Vol 13 (4) ◽  
pp. 8831-8872 ◽  
Author(s):  
I. Engel ◽  
B. P. Luo ◽  
M. C. Pitts ◽  
L. R. Poole ◽  
C. R. Hoyle ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Temperature Fluctuations ◽  
Ice Nucleation ◽  
Solid Particles ◽  
Small Scale ◽  
Synoptic Scale ◽  
Polar Stratospheric Clouds ◽  
Ice Nuclei ◽  
Scale Temperature ◽  
Stratospheric Clouds

Abstract. This paper provides unprecedented evidence for the importance of heterogeneous nucleation, likely on solid particles of meteoritic origin, and of small-scale temperature fluctuations, for the formation of ice particles in the Arctic stratosphere. During January 2010, ice PSCs (Polar Stratospheric Clouds) were shown by CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) to have occurred on a synoptic scale (~ 1000 km dimension). CALIPSO observations also showed widespread PSCs containing nitric acid trihydrate (NAT) particles in December 2009, prior to the occurrence of synoptic-scale regions of ice PSCs during mid-January 2010. We demonstrate by means of detailed microphysical modeling along air parcel trajectories that the formation of these PSCs is not readily reconciled with expectations from the conventional understanding of PSC nucleation mechanisms. The measurements are at odds with the previous laboratory-based understanding of PSC formation, which deemed direct heterogeneous nucleation of NAT and ice on preexisting solid particles unlikely. While a companion paper (Part 1) addresses the heterogeneous nucleation of NAT during December 2009, before the existence of ice PSCs, this paper shows that also the large-scale occurrence of stratospheric ice in January 2010 cannot be explained merely by homogeneous ice nucleation but requires the heterogeneous nucleation of ice, e.g. on meteoritic dust or preexisting NAT particles. The required efficiency of the ice nuclei is surprisingly high, namely comparable to that of known tropospheric ice nuclei such as mineral dust particles. To gain model agreement with the ice number densities inferred from observations, the presence of small-scale temperature fluctuations, with wavelengths unresolved by the numerical weather prediction models, is required. With the derived rate parameterization for heterogeneous ice nucleation we are able to explain and reproduce CALIPSO observations throughout the entire Arctic winter 2009/2010.

scholarly journals On the transition between heterogeneous and homogeneous freezing

2003 ◽  
Vol 3 (2) ◽  
pp. 437-446 ◽  
Author(s):  
K. Gierens
Keyword(s):  
Air Pollution ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Narrow Range ◽  
Ambient Pressure ◽  
Soot Concentration ◽  
Model Simulations ◽  
Critical Concentrations ◽  
Ice Nuclei ◽  
Homogeneous Freezing

Abstract. Box model simulations of an uplifting and adiabatically cooling cloud of aerosol have been performed in order to study the transition between cirrus formation dominated by homogeneous nucleation of ice to that dominated by heterogeneous nucleation. The aerosol was assumed to consist of an internal mixture of sulfuric acid solution droplets with inclusions of soot. The parametrisation of De Mott et al. (1997) was used to simulate the heterogeneous nucleation of ice in such droplets with soot inclusions. The simulations show that the transition from heterogeneous to homogeneous nucleation occurs over a narrow range of soot concentration. Thus it seems to be possible to fix critical concentrations of heterogeneous ice nuclei which must be exceeded if heterogeneous freezing dominates cirrus formation. A formula has been derived that allows to compute the critical concentrations of heterogeneous ice nuclei as a function of temperature, updraft speed, ambient pressure, and supersaturation at which heterogeneous freezing occurs. Generally, homogeneous nucleation dominates in regions with updrafts stronger than 20 cm s -1, with the exception of heavily polluted areas which could be common in the northern hemisphere due to air traffic, where updrafts of the order 1 m s-1 may be necessary to render heterogeneous nucleation unimportant. According to the present results it cannot be excluded that heterogeneous nucleation plays a more important role for cirrus formation in the northern midlatitudes than anywhere else. A possible consequence of these results is that air pollution may lead to a higher coverage of cirrus clouds, but then these clouds will be optically thinner than clouds formed by homogeneous freezing, with the exception of regions where condensation trails are frequent.

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