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Density gradient theory combined with the PC-SAFT equation of state used for modeling the surface tension of associating systems
Vinš, Václav ; Planková, Barbora ; Hrubý, Jan ; Celný, D.
The density gradient theory (GT) combined with a SAFT-type (Statistical Associating Fluid Theory) equation of state has been used for modeling the surface tension of associating fluids represented by a series of six alkanols ranging from methanol to 1-pentanol. The effect of nonzero dipole moment of the selected alkanols on the predicted surface tension was investigated in this study. Results of the GT + non-polar Perturbed Chain (PC) SAFT equation of state were compared to predictions of GT combined with the PC-polar-SAFT, i.e. PCP-SAFT, equation. Both GT + PC-SAFT and GT + PCP-SAFT give reasonable prediction of the surface tension for pure alkanols. Results of both models are comparable as no significant difference in the modeled saturation properties and in the predicted surface tension using GT was found. Consideration of dipolar molecules of selected alkanols using PCP-SAFT had only minor effect on the predicted properties compared to the non-polar PC-SAFT model.
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Modelling of Sulfuric Acid Nanoparticles Growth
Škrabalová, Lenka ; Brus, D. ; Antilla, T. ; Ždímal, Vladimír ; Lihavainen, H.
Aerosol particles influence global radiative balance and climate directly through scattering and absorbing solar radiation and indirectly by acting as condensation cloud nuclei. The atmospheric nucleation is often followed by a rapid growth of freshly formed particles. The initial growth of aerosol is the crucial process determining the fraction of nucleated particles growing into cloud condensation nuclei sizes (~ 50 nm and larger). The subject of this study is modelling of growth behaviour of sulfuric acid nanoparticles produced by nucleation of water and sulfuric acid under wet and dry conditions.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_C22013101814581 - PDF
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Influence of Size Effect on Evaporation of Aerosol Nanoparticles
Levdansky, V.V. ; Smolík, Jiří ; Ždímal, Vladimír
Evaporation of nanoscale particles plays a significant role in many branches of nanotechnology and also in the atmospheric physics and chemistry. The classical approach to the description of evaporation of small (nanoscale) aerosol particles is usually based on the Kelvin equation. The mentioned equation was used in (Nanda et al., 2003) to interpret the results of experiments related to evaporation of free Ag nanoparticles. The authors of the above-mentioned paper assume that the surface tension of free Ag nanoparticles can be significant greater than the mentioned value for bulk matter. It is worth noting that this assumption is in contradiction with the Tolman theory (Tolman, 1949). Below we consider the influence of the size dependence of the cohesive energy in the nanoparticle on its evaporation.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22013101814594 - PDF
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Size Dependence of Incorporation of Gas Molecules into Aerosol Nanoparticles
Levdansky, V.V. ; Smolík, Jiří ; Ždímal, Vladimír ; Moravec, Pavel
The influence of size effects on the physicochemical transformations and transfer phenomena in the heterogeneous systems with nanoobjects attracts increasing attention of researchers. These problems are of interest for nanotechnology and atmospheric physics. Size effects can influence the cohesive energy as well as the activation energies of vacancy formation and diffusion of atoms in the nanoscale particles (Vanithakumari and Nanda, 2008). Phase transitions in aerosol systems with nanoscale particles (clusters) also depend on the nanoparticle size (Levdansky et al., 2010). Hear we discuss the size dependence of the mass accommodation coefficient in the aerosol system with nanoparticles.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22013091912290 - PDF
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Reducing the Edge Chipping for Capillary End Face Grinding and Polishing
Hošek, Jan ; Studenovský, K.
This paper presents results of glass capillary end face grinding and polishing by approach that reduces the edge chipping. Brittle materials have natural tendency for edge chipping what leads to beveling the sharp edges. Not beveled sharp edges on glass capillary are important for special applications like surface tension measurement of small liquid samples. We use common grinding and polishing process for capillary end face machining modified with gradual decreasing of grinding load based on the relation of the critical chipping load. Achieved surface roughness is measured using atomic force microscopy (AFM). Capillary inner edge quality is checked both with optical microscopes and electron microscope too. We achieved a non-chipped capillary inner edge with radius down to 100 nm.
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Reducing the Edge Chipping for Capillary End Face Grinding and Polishing
Hošek, Jan ; Studenovský, K.
This paper presents results of glass capillary end face grinding and polishing by approach that reduces the edge chipping. Brittle materials have natural tendency for edge chipping what leads to beveling the sharp edges. Not beveled sharp edges on glass capillary are important for special applications like surface tension measurement of small liquid samples. We use common grinding and polishing process for capillary end face machining modified with gradual decreasing of grinding load based on the relation of the critical chipping load. Achieved surface roughness is measured using atomic force microscopy (AFM). Capillary inner edge quality is checked both with optical microscopes and electron microscope too. We achieved a non-chipped capillary inner edge with radius down to 100 nm.
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Size Dependence of Reactive Uptake Coefficient in Chemical Reactions on Aerosol Nanoparticles
Levdansky, Valerij Vladimirovič ; Smolík, Jiří ; Ždímal, Vladimír ; Moravec, Pavel
Chemical reactions in aerosol systems play a significant role in formation of new aerosol particles and their growth in the atmosphere and in various areas of nanotechnology. In the case of nanoscale aerosol particle the size effects can sufficiently affect the rate of chemical reactions both inside the particle and on its surface. The size dependence of a chemical reaction occurring on the nanoparticle surface can be related to the size dependence of the intrinsic activation energy for a chemical reaction and the adsorption kinetics of reactant molecules. Here we consider some aspects of the possible influence of the mentioned effects on the reactive uptake coefficient in the Eley-Rideal mechanism of a chemical reaction.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22012102615344 - PDF
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Mass Accomodation Coefficient for Nanoscale Aerosol Particles
Levdansky, Valerij Vladimirovič ; Smolík, Jiří ; Ždímal, Vladimír ; Moravec, Pavel
The influence of size effects on physicochemical transformations and transfer processes in the heterogeneous systems with nanoobjects attracts increasing attention of researchers. These problems are of interest for nanotechnology and atmospheric physics. Size effects can influence the cohesive energy as well as the activation energies of vacancy formation and diffusion of atoms in the nanoscale particles (Vanithakumari and Nanda, 2008). Phase transitions (including nucleation) in aerosol systems with nanoscale particles (clusters) also depend on the nanoparticle size (Levdansky et al., 2010). Hear we discuss the size dependence of the mass accommodation coefficient gama in the gas–nanoparticle system.
Fulltext: content.csg - PDF
Plný tet: SKMBT_C22012102615343 - PDF
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