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William R. Smith - One of the best experts on this subject based on the ideXlab platform.
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Computer simulation studies of a square-well fluid in a slit pore. Spreading Pressure and vapor–liquid phase equilibria using the virtual-parameter-variation method
The Journal of Chemical Physics, 2000Co-Authors: Horst L. Vörtler, William R. SmithAbstract:We study model square-well fluids with well-width parameter λ=1.5 confined to hard planar slits. We derive a general computer simulation method for numerically calculating an arbitrary first derivative of the canonical ensemble partition function with respect to a simulation parameter, which we call the virtual-parameter-variation method. Two special cases of this approach are the Widom test-particle insertion method for calculating the excess chemical potential, and a method for calculating the Pressure due to Eppenga and Frenkel [Mol. Phys. 52, 52, 1303 (1984)]. We use this approach to calculate the volume derivative parallel to the slit walls of the Helmholtz free energy in an (N,V,T) Monte Carlo simulation, and show that this Spreading Pressure is numerically consistent with the thermodynamic Pressure obtained by integration of the Gibbs–Duhem equation using the simulated chemical potentials of the confined fluid as a function of density. We obtain new simulation results for the Spreading Pressure and...
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computer simulation studies of a square well fluid in a slit pore Spreading Pressure and vapor liquid phase equilibria using the virtual parameter variation method
Journal of Chemical Physics, 2000Co-Authors: Horst L. Vörtler, William R. SmithAbstract:We study model square-well fluids with well-width parameter λ=1.5 confined to hard planar slits. We derive a general computer simulation method for numerically calculating an arbitrary first derivative of the canonical ensemble partition function with respect to a simulation parameter, which we call the virtual-parameter-variation method. Two special cases of this approach are the Widom test-particle insertion method for calculating the excess chemical potential, and a method for calculating the Pressure due to Eppenga and Frenkel [Mol. Phys. 52, 52, 1303 (1984)]. We use this approach to calculate the volume derivative parallel to the slit walls of the Helmholtz free energy in an (N,V,T) Monte Carlo simulation, and show that this Spreading Pressure is numerically consistent with the thermodynamic Pressure obtained by integration of the Gibbs–Duhem equation using the simulated chemical potentials of the confined fluid as a function of density. We obtain new simulation results for the Spreading Pressure and...
Horst L. Vörtler - One of the best experts on this subject based on the ideXlab platform.
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Computer simulation studies of a square-well fluid in a slit pore. Spreading Pressure and vapor–liquid phase equilibria using the virtual-parameter-variation method
The Journal of Chemical Physics, 2000Co-Authors: Horst L. Vörtler, William R. SmithAbstract:We study model square-well fluids with well-width parameter λ=1.5 confined to hard planar slits. We derive a general computer simulation method for numerically calculating an arbitrary first derivative of the canonical ensemble partition function with respect to a simulation parameter, which we call the virtual-parameter-variation method. Two special cases of this approach are the Widom test-particle insertion method for calculating the excess chemical potential, and a method for calculating the Pressure due to Eppenga and Frenkel [Mol. Phys. 52, 52, 1303 (1984)]. We use this approach to calculate the volume derivative parallel to the slit walls of the Helmholtz free energy in an (N,V,T) Monte Carlo simulation, and show that this Spreading Pressure is numerically consistent with the thermodynamic Pressure obtained by integration of the Gibbs–Duhem equation using the simulated chemical potentials of the confined fluid as a function of density. We obtain new simulation results for the Spreading Pressure and...
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computer simulation studies of a square well fluid in a slit pore Spreading Pressure and vapor liquid phase equilibria using the virtual parameter variation method
Journal of Chemical Physics, 2000Co-Authors: Horst L. Vörtler, William R. SmithAbstract:We study model square-well fluids with well-width parameter λ=1.5 confined to hard planar slits. We derive a general computer simulation method for numerically calculating an arbitrary first derivative of the canonical ensemble partition function with respect to a simulation parameter, which we call the virtual-parameter-variation method. Two special cases of this approach are the Widom test-particle insertion method for calculating the excess chemical potential, and a method for calculating the Pressure due to Eppenga and Frenkel [Mol. Phys. 52, 52, 1303 (1984)]. We use this approach to calculate the volume derivative parallel to the slit walls of the Helmholtz free energy in an (N,V,T) Monte Carlo simulation, and show that this Spreading Pressure is numerically consistent with the thermodynamic Pressure obtained by integration of the Gibbs–Duhem equation using the simulated chemical potentials of the confined fluid as a function of density. We obtain new simulation results for the Spreading Pressure and...
Silvia G. De Bussetti - One of the best experts on this subject based on the ideXlab platform.
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The surface properties of sepiolite
Applied Surface Science, 2008Co-Authors: A. K. Helmy, Silvia G. De BussettiAbstract:Abstract Some surface properties of sepiolite were determined for a natural sample and after surface charge saturation with sodium cations. The values obtained are: water/solid contact angle 70.9° and 71.4°, Spreading Pressure at monolayer coverage 119.2 and 120.3 mJ m −2 , Spreading Pressure at saturation 144.1 and 142.4 mJ m −2 amounts of water adsorbed at monolayer coverage 74.48 and 78.06 mg g −1 , surface energy 243.3 and 241.4 mJ m −2 , water/solid interfacial energy 7.4 and 7.4 kJ mol −1 , enthalpy of water adsorption 52.4 and 52.24 kJ mol −1 respectively. These values are similar to those reported in the literature for palygorskite which is the other member of the clay mineral group.
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The water–silicas interfacial interaction energies
Applied Surface Science, 2007Co-Authors: A. K. Helmy, Silvia G. De Bussetti, E. A. FerreiroAbstract:Abstract The water–silicas interfacial interaction energies were calculated for samples of quartz, silicas and silicas outgassed at high temperatures using own and published data of the Spreading Pressure of water, its surface tension, its contact angle and using formulas obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for 18 different samples were in the range 7.80–6.92 kJ mol−1. Lower values of energies are for samples that contain relatively less amounts of water at P/P0 = 0.25 and are characterized also by relatively low values of surface Pressures.
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The surface energy of palygorskite
Powder Technology, 2007Co-Authors: A. K. Helmy, Silvia G. De Bussetti, E. A. FerreiroAbstract:Abstract An average value for the surface energy (γ¯S) of palygorskite was determined from experimental data of Spreading Pressure, the surface tension of water and its contact angle using a formula based on the combination of the Young equation with a general equation of pair interaction. The value found is 226.6 mJ m− 2. Some factors that affect the determination of surface energy via solid–liquid interaction are exposed. The backgrounds of previous formulas for the calculation of the surface energy of palygorskite are also critically examined.
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The water/graphitic-carbon interaction energy
Applied Surface Science, 2007Co-Authors: A. K. Helmy, E. A. Ferreiro, Silvia G. De BussettiAbstract:Abstract The water/graphitic-carbon interaction energy was obtained for a sample having a water surface site adsorption density of 13.3 μmol m −2 . The interaction energy was determined from the Spreading Pressure of water, its surface tension and the water contact angle and using a formula obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for contact angles 42° and 86° are 7.63 and 7.18 kJ mol −1 of water are similar to the water binding energies obtained from molecular dynamic simulations of water droplets on a graphite surface: 6.7–8.33 kJ mol −1 .
A. K. Helmy - One of the best experts on this subject based on the ideXlab platform.
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The surface properties of sepiolite
Applied Surface Science, 2008Co-Authors: A. K. Helmy, Silvia G. De BussettiAbstract:Abstract Some surface properties of sepiolite were determined for a natural sample and after surface charge saturation with sodium cations. The values obtained are: water/solid contact angle 70.9° and 71.4°, Spreading Pressure at monolayer coverage 119.2 and 120.3 mJ m −2 , Spreading Pressure at saturation 144.1 and 142.4 mJ m −2 amounts of water adsorbed at monolayer coverage 74.48 and 78.06 mg g −1 , surface energy 243.3 and 241.4 mJ m −2 , water/solid interfacial energy 7.4 and 7.4 kJ mol −1 , enthalpy of water adsorption 52.4 and 52.24 kJ mol −1 respectively. These values are similar to those reported in the literature for palygorskite which is the other member of the clay mineral group.
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The water–silicas interfacial interaction energies
Applied Surface Science, 2007Co-Authors: A. K. Helmy, Silvia G. De Bussetti, E. A. FerreiroAbstract:Abstract The water–silicas interfacial interaction energies were calculated for samples of quartz, silicas and silicas outgassed at high temperatures using own and published data of the Spreading Pressure of water, its surface tension, its contact angle and using formulas obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for 18 different samples were in the range 7.80–6.92 kJ mol−1. Lower values of energies are for samples that contain relatively less amounts of water at P/P0 = 0.25 and are characterized also by relatively low values of surface Pressures.
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The surface energy of palygorskite
Powder Technology, 2007Co-Authors: A. K. Helmy, Silvia G. De Bussetti, E. A. FerreiroAbstract:Abstract An average value for the surface energy (γ¯S) of palygorskite was determined from experimental data of Spreading Pressure, the surface tension of water and its contact angle using a formula based on the combination of the Young equation with a general equation of pair interaction. The value found is 226.6 mJ m− 2. Some factors that affect the determination of surface energy via solid–liquid interaction are exposed. The backgrounds of previous formulas for the calculation of the surface energy of palygorskite are also critically examined.
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The water/graphitic-carbon interaction energy
Applied Surface Science, 2007Co-Authors: A. K. Helmy, E. A. Ferreiro, Silvia G. De BussettiAbstract:Abstract The water/graphitic-carbon interaction energy was obtained for a sample having a water surface site adsorption density of 13.3 μmol m −2 . The interaction energy was determined from the Spreading Pressure of water, its surface tension and the water contact angle and using a formula obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for contact angles 42° and 86° are 7.63 and 7.18 kJ mol −1 of water are similar to the water binding energies obtained from molecular dynamic simulations of water droplets on a graphite surface: 6.7–8.33 kJ mol −1 .
Derun Zhang - One of the best experts on this subject based on the ideXlab platform.
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a novel method for measuring surface free energy of highly wettable mineral powders
Construction and Building Materials, 2019Co-Authors: Derun ZhangAbstract:Abstract This paper develops a novel method to measure the surface free energy for the highly wettable mineral powders by means of the capillary rise measurements. In this method, a generalized modified Washburn equation is first derived to capture the Spreading wetting mechanism of the probe liquid into the mineral powders with high wettability. A series of apolar liquids are then selected to conduct the capillary rise test to generate a plot of the measured test results against the square root of the liquid surface tension. Fitting such a plot with a parabolic function, the resultant effective capillary radius and the powder apolar surface energy component can be solved. Then the Spreading Pressure of two independent liquids is calculated from their capillary rise test results. The polar acid and polar base surface energy components of the highly wettable powders can be finally determined by substituting the calculated Spreading Pressure values into the Good-van Oss-Chaudhury model. The proposed method has been successfully applied to measure the surface free energy for four typical types of mineral powders. The measured surface free energies of the selected powders are found to be approximately the same as those obtained from a previous method with different principle. In this regard, the proposed method is validated to be capable of accurately measuring the surface free energy for highly wettable mineral powders.
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characterization of surface free energy of mineral filler by Spreading Pressure approach
Construction and Building Materials, 2019Co-Authors: Derun Zhang, Rong Luo, Zhe ZengAbstract:Abstract Surface free energy of mineral filler plays an important role in evaluating the adhesion of asphalt mastic (mineral filler plus asphalt binder), which is usually measured through the capillary rise approach. However, this approach has been verified to hold only for the low energy materials, which does not apply to the high energy mineral filler. To overcome this limitation, the paper devises a new approach for measuring the surface free energy of the mineral filler based on a generalized Washburn equation. First, a reference liquid is selected to conduct the vapor adsorption test on the mineral filler to measuring its Spreading Pressure, in which a modified Brunauer-Emmett-Teller (BET) model is employed to determine the filler specific surface area. This reference liquid is again used to perform the capillary rise measurement to calculate the resultant effective capillary radius of the filler bed. Three independent liquids are subsequently selected to conduct the capillary rise test to measure their Spreading Pressure values with respect to the same mineral filler. By substituting the measured Spreading Pressure values of the three liquids into the Good-van Oss-Chaudhury (GvOC) equation, the surface free energy components of the mineral filler are finally determined. This newly developed approach is then successfully applied to measure the surface free energy for four typical types of the mineral filler. The moisture susceptibility rankings obtained from the energy ratios of the proposed approach are experimentally found to be consistence with those measured from a standard moisture susceptibility test for the corresponding asphalt mastics. In this regard, the proposed approach is believed to be capable of accurately characterizing the surface free energy of the mineral filler.
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Development of a method to determine surface energy components of mineral fillers
Construction and Building Materials, 2017Co-Authors: Derun Zhang, Rong LuoAbstract:Abstract The surface energy components of the mineral fillers in asphalt mixtures are of significant importance to the fatigue and healing properties of the asphalt mastic. However, the Washburn equation did not apply to mineral fillers when using the column wicking method because mineral fillers can hardly form a non-zero contact angle with any probe liquid. This paper developed a new model for mineral fillers wicking a probe liquid; this model established a relationship among the mass of the wicked liquid, the wicking time and the Spreading Pressure of the probe liquid on the mineral fillers. Based on the developed model, an experimental protocol was designed to determine the Spreading Pressure of three probe liquids on five types of mineral fillers, respectively. The Gravimetric Sorption Analyzer was employed to perform the vapor adsorption tests to determine the Spreading Pressure of toluene on each type of mineral fillers; the Tensiometer System was utilized to measure the mass of probe liquids rising into the filler samples, respectively. Based on the test results, the Spreading Pressure of every probe liquid on each filler sample was determined, which was then used to solve for the surface energy components of the mineral fillers. The surface energy components of the fillers were compared with those of the coarse aggregates from the same quarry. Significant variations were identified in each component between the fillers and the corresponding coarse aggregates, which demonstrated the importance of the geometric characteristics of the aggregates to their surface energy components. Furthermore, an asphalt binder was selected to evaluate its adhesive bond energies with the fillers and the corresponding coarse aggregates, respectively. With the same asphalt binder, the nonpolar components of the fillers were smaller than those of the corresponding coarse aggregates, while the polar components and the total adhesive bond energies of the fillers were larger than those of the corresponding coarse aggregates. The differences among the components of the cohesive bond energy and the adhesive bond energies suggested that cracking and healing per unit length would need different energies in the three media, asphalt film, asphalt mastic and asphalt-aggregate interface. These differences would significantly influence the cracking development in asphalt mixtures because cracks would always grow along the easiest path that would need the lowest energy to create crack surfaces.