scholarly journals Quasi-Liquid Layer on Ice and Its Effect on the Confined Freezing of Porous Materials

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 250 ◽  
Author(s):  
Qiang Zeng ◽  
Kefei Li
Keyword(s):  
Porous Materials ◽  
Liquid Layer ◽  
Intermediate Phase ◽  
Elastic Model ◽  
Ice Growth ◽  
Pore Pressures ◽  
Quasi Liquid Layer ◽  
Porous Frame ◽  
Physical Principles

Freezing of the water confined in thin pores can be destructive to the porous frame, but the effect of the quasi-liquid layer (QLL) between the confined ice and the pore walls remains still far from being fully understood. In the present study, the physical origins of the intermediate phase of QLL were discussed by thermodynamic analyses. Different interactions on QLL bring different models to estimate its thickness, which generally decays with temperature decreasing. Four representative models of QLL thickness were selected to unveil its effect on the growing rates and extents of ice in a concrete. The engineering consequences of the confined freezing were then discussed in the aspects of effective pore pressures built from the confined ice growth and deformations framed by a poro-elastic model. Overall, thickening QLL depresses ice growing rates and contents and, consequentially, decreases pore pressures and material deformations during freezing. The QLL corrections also narrow the gaps between the predicted and measured freezing deformations. The findings of this study contribute to profound understandings of confined freezing that may bridge over physical principles and engineering observations.

scholarly journals Plasmon-Enhanced Photothermal and Optomechanical Deformations of a Gold Nanoparticle

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1881
Author(s):  
Jiunn-Woei Liaw ◽  
Guanting Liu ◽  
Yun-Cheng Ku ◽  
Mao-Kuen Kuo
Keyword(s):  
Gold Nanoparticle ◽  
Liquid Layer ◽  
Viscoelastic Model ◽  
Dynamics Simulation ◽  
Photothermal Effect ◽  
Continuous Heating ◽  
Heating Process ◽  
Elastic Model ◽  
Linearly Polarized ◽  
Quasi Liquid Layer

Plasmon-enhanced photothermal and optomechanical effects on deforming and reshaping a gold nanoparticle (NP) are studied theoretically. A previous paper (Wang and Ding, ACS Nano 13, 32–37, 2019) has shown that a spherical gold nanoparticle (NP) irradiated by a tightly focused laser beam can be deformed into an elongated nanorod (NR) and even chopped in half (a dimer). The mechanism is supposed to be caused by photothermal heating for softening NP associated with optical traction for follow-up deformation. In this paper, our study focuses on deformation induced by Maxwell’s stress provided by a linearly polarized Gaussian beam upon the surface of a thermal-softened NP/NR. We use an elastic model to numerically calculate deformation according to optical traction and a viscoelastic model to theoretically estimate the following creep (elongation) as temperature nears the melting point. Our results indicate that a stretching traction at the two ends of the NP/NR causes elongation and a pinching traction at the middle causes a dent. Hence, a bigger NP can be elongated and then cut into two pieces (a dimer) at the dent due to the optomechanical effect. As the continuous heating process induces premelting of NPs, a quasi-liquid layer is formed first and then an outer liquid layer is induced due to reduction of surface energy, which was predicted by previous works of molecular dynamics simulation. Subsequently, we use the Young–Laplace model to investigate the surface tension effect on the following deformation. This study may provide an insight into utilizing the photothermal effect associated with optomechanical manipulation to tailor gold nanostructures.

scholarly journals 1-D Air-snowpack modeling of atmospheric nitrous acid at South Pole during ANTCI 2003

2008 ◽  
Vol 8 (23) ◽  
pp. 7087-7099 ◽  
Author(s):  
W. Liao ◽  
D. Tan
Keyword(s):  
Liquid Layer ◽  
Molecular Diffusion ◽  
Volume Ratio ◽  
Critical Factor ◽  
Snow Surface ◽  
High Concentration ◽  
Nitrite Concentration ◽  
Mechanical Dispersion ◽  
Quasi Liquid Layer ◽  
D Model

Abstract. A 1-D air-snowpack model of HONO has been developed and constrained by observed chemistry and meteorology data. The 1-D model includes molecular diffusion and mechanical dispersion, windpumping in snow, gas phase to quasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate and interstitial air HONO photolysis. Photolysis of nitrate is important as a dominant HONO source inside the snowpack, however, the observed HONO emission from the snowpack was triggered mainly by the equilibrium between quasi liquid layer nitrite and firn air HONO deep down the snow surface (i.e. 30 cm below snow surface). The high concentration of HONO in the firn air is subsequently transported above the snowpack by diffusion and windpumping. The model uncertainties come mainly from lack of measurements and the interpretation of the QLL properties based on the bulk snow measurements. One critical factor is the ionic strength of QLL nitrite, which is estimated here by the bulk snow pH, nitrite concentration, and QLL to bulk snow volume ratio.

scholarly journals Multiphase modeling of nitrate photochemistry in the quasi-liquid layer (QLL): implications for NO<sub>x</sub> release from the Arctic and coastal Antarctic snowpack

2008 ◽  
Vol 8 (16) ◽  
pp. 4855-4864 ◽  
Author(s):  
C. S. Boxe ◽  
A. Saiz-Lopez
Keyword(s):  
Gas Phase ◽  
Liquid Layer ◽  
Solar Spectrum ◽  
The Arctic ◽  
Transfer Model ◽  
Multiphase Model ◽  
Gas Phase Reactions ◽  
One Dimensional ◽  
Quasi Liquid Layer ◽  
Summer Range

Abstract. We utilize a multiphase model, CON-AIR (Condensed Phase to Air Transfer Model), to show that the photochemistry of nitrate (NO3−) in and on ice and snow surfaces, specifically the quasi-liquid layer (QLL), can account for NOx volume fluxes, concentrations, and [NO]/[NO2] (γ=[NO]/[NO2]) measured just above the Arctic and coastal Antarctic snowpack. Maximum gas phase NOx volume fluxes, concentrations and γ simulated for spring and summer range from 5.0×104 to 6.4×105 molecules cm−3 s−1, 5.7×108 to 4.8×109 molecules cm−3, and ~0.8 to 2.2, respectively, which are comparable to gas phase NOx volume fluxes, concentrations and γ measured in the field. The model incorporates the appropriate actinic solar spectrum, thereby properly weighting the different rates of photolysis of NO3− and NO2−. This is important since the immediate precursor for NO, for example, NO2−, absorbs at wavelengths longer than nitrate itself. Finally, one-dimensional model simulations indicate that both gas phase boundary layer NO and NO2 exhibit a negative concentration gradient as a function of height although [NO]/[NO2] are approximately constant. This gradient is primarily attributed to gas phase reactions of NOx with halogens oxides (i.e. as BrO and IO), HOx, and hydrocarbons, such as CH3O2.

scholarly journals 1-D air-snowpack modeling of atmospheric nitrous acid at South Pole during ANTCI 2003

2008 ◽  
Vol 8 (3) ◽  
pp. 9731-9759
Author(s):  
◽  
D. Tan
Keyword(s):  
Liquid Layer ◽  
Molecular Diffusion ◽  
Volume Ratio ◽  
Critical Factor ◽  
Snow Surface ◽  
High Concentration ◽  
Nitrite Concentration ◽  
Mechanical Dispersion ◽  
Quasi Liquid Layer ◽  
D Model

Abstract. A 1-D air-snowpack model of HONO has been developed and constrained by observed chemistry and meteorology data. The 1-D model includes molecular diffusion and mechanical dispersion, windpumping in snow, gas phase to quasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate and interstitial air HONO photolysis. Photolysis of nitrate is important as a dominant HONO source inside the snowpack, however, the observed HONO emission from the snowpack was triggered mainly by the equilibrium between quasi liquid layer nitrite and firn air HONO deep down the snow surface (i.e. 30 cm below snow surface). The high concentration of HONO in the firn air is subsequently transported above the snowpack by diffusion and windpumping. The model uncertainties come mainly from lack of measurements and the interpretation of the QLL properties based on the bulk snow measurements. One critical factor is the ionic strength of QLL nitrite, which is estimated here by the bulk snow pH, nitrite concentration, and QLL to bulk snow volume ratio.

Capillarity in Soft Porous Solids

2020 ◽  
Vol 52 (1) ◽  
pp. 263-284 ◽  
Author(s):  
Jonghyun Ha ◽  
Ho-Young Kim
Keyword(s):  
Porous Media ◽  
Porous Materials ◽  
Porous Solids ◽  
Resurrection Plants ◽  
Wetting And Drying ◽  
Practical Applications ◽  
Capillary Interactions ◽  
Soft Porous Media ◽  
Experimental Findings ◽  
Physical Principles

Soft porous solids can change their shapes by absorbing liquids via capillarity. Such poro-elasto-capillary interactions can be seen in the wrinkling of paper, swelling of cellulose sponges, and morphing of resurrection plants. Here, we introduce physical principles relevant to the phenomena and survey recent advances in the understanding of swelling and shrinkage of bulk soft porous media due to wetting and drying. We then consider various morphing modes of porous sheets, which are induced by localized wetting and swelling of soft porous materials. We focus on physical insights with the aim of triggering novel experimental findings and promoting practical applications.

Facetting Growth of Low Temperature Polycrystalline Silicon by Ecr-Cvd with Hydrogen Dilution Method

1998 ◽  
Vol 507 ◽  
Author(s):  
H.-L. Hsiao ◽  
A.-B. Yang ◽  
H.-L. Hwang
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Liquid Layer ◽  
Polycrystalline Silicon ◽  
Diffusion Processes ◽  
Crystalline Silicon ◽  
Dark Field ◽  
Dilution Method ◽  
Hydrogen Dilution ◽  
Quasi Liquid Layer

ABSTRACTThe polycrystalline silicon films with grain size of 1 μ m have been successful deposited on glass substrates using ECR-CVD with hydrogen dilution method at 250°C and without any thermal annealing. The deposited poly-Si films exhibit severe “hill and valley” surface roughness and facets structures. The X-ray diffraction spectra show that the dominant crystal textures are <220> and <111> orientations. The leaf-like two-fold symmetrical grain shape and the corresponding crystallography diffraction pattern indicate the orientation of largest grain is <110>. The dark field TEM image also shows the upside octahedral facets shape. Considering the effect of orientation on deposition rate and symmetry, the possible facets orientation should be <311>. Moreover, the grain sizes of poly-Si thin films deposited on bare Si wafer and on oxidized Si substrates or glass are almost the same. The facetting and textural structures can be attributed to the surface free energy change induced by the adatom quasi-liquid layer which is composed by the radicals and energetic atomic hydrogen. This adatom quasi-liquid layer would dramatically change the surface diffusion processes of adsorbed precursors and surface free energy of low index planes. Therefore, the SiHn radicals and SinHm molecular precursors with enhanced surface mobility would relax to their stable sites and form the crystalline silicon clusters.

Orientation dependence of the quasi-liquid layer on tin and indium crystals

1994 ◽  
Vol 314 (3) ◽  
pp. 341-352 ◽  
Author(s):  
A. Pavlovska ◽  
D. Dobrev ◽  
E. Bauer
Keyword(s):  
Liquid Layer ◽  
Orientation Dependence ◽  
Quasi Liquid Layer

scholarly journals Modeling of deformation and fracture of porous media taking into account their morphological composition

2020 ◽  
pp. 175-187
Author(s):  
A. S Shalimov ◽  
M. A Tashkinov
Keyword(s):  
Porous Materials ◽  
Numerical Models ◽  
Aluminum Matrix ◽  
Cell Types ◽  
Plastic Behavior ◽  
Elastic Model ◽  
Open Cell ◽  
Representative Volume ◽  
Closed Cell ◽  
Representative Volume Elements

This paper investigates the mechanical behavior and fracture of porous materials with an aluminum matrix. The purpose of the work was to create numerical models of failure of representative volume elements of such materials and to reveal the dependences of the nature of the failure processes on their structural morphology. Representative volume elements of these materials are random non-uniform structures of closed-cell and open-cell types. To create three-dimensional geometric models of the closed-cell structures, methods of sequential synthesis the possibility of their mutual intersection were used. For creation of models of interpenetrating structures of the open-cell type, methods based on the analytical determination of surfaces separating the two phases are used. In this paper, three approaches to fracture mechanics of representative volume elements of porous materials were studied and implemented. The first approach is an implementation of the elastic model and damage accumulation based on elastic properties degradation in accordance with the criterion of maximum stresses with reduction of the stiffness matrix coefficients in individual elements. The second approach is an implementation of the same model, but with removal of the failed elements. The third approach is based on the Johnson-Cook elastic plastic behavior and fracture model. Numerical modeling of the representative volumes was carried out with finite element analysis using each of the above approaches. The influence of the internal structure of the representative volumes of the porous materials on the processes of deformation and failure was studied on the example of several structures of open-cell and closed-cell types. The influence of stress concentrators on the distribution of stresses in representative volumes and character of their subsequent failure has been studied.

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