Tension Of Droplets Research Articles

Molecular basis for calculating the surface tension of binary droplets

A procedure for calculating the surface tension of droplets consisting of two components in the vapor phase is considered. The calculations are performed using the lattice gas model in the quasi-chemical approximation with allowance for the correlation effects of the nearest interacting molecules. A layered model of the structure of a vapor–liquid interface is used. Ways of calculating the surface tension of droplets with different radii are considered. They are based on different thermodynamic definitions of reference surfaces. Typical dependences of the surface tension of metastable and equilibrium droplets on the droplets’ radii are analyzed for four types of phase diagram. It is found that if the energy of interaction between the components of one type exceeds by 150% the energies of interaction between components of another type and between particles of different types, and if the component with the highest energy of interaction predominates in a droplet, this results in a nonmonotonic profile of the component with the lowest energy of interaction in the region of transition. Mixture components are distributed in the region of transition such that the component with the highest energy of interaction is concentrated on the liquid side and the other component is concentrated on the vapor side. The surface tension of equilibrium droplets is less than that of metastable droplets.

Stable deformation of droplets surface subjected to a high-voltage electric field in oil

Abstract Electro-demulsification is widely applied to the dehydration of emulsified oil. A droplet exposed to an electric field is polarised in oil and then stretched to a prolate sphere. The internal electric field distributions of prolate-sphere and spherical droplets are analysed in this work. The expressions of force acting on the droplets surface are obtained by establishing a model of stable droplet stretching deformation. An experiment is conducted to determine the draw ratio of water droplets subjected to a high electric field and exposed in four types of base oil. Comparison of the results of the experiment and model shows that the stable deformation of droplets is well predicted by the model. System parameters, such as electric field strength, droplet initial radius, interfacial tension of droplet – oil, permittivity and effect on the deformation of droplets, are also discussed.

Effect of nanoparticle enwrapping on the static and dynamic behavior of water droplet

We studied the static and dynamic properties of water droplet and the droplet coated with silica nanoparticles. The water droplet changes from wetting on the quartz substrate to superhydrophobic state with the enwrapping of particles. The impact dynamics of the droplets impinging on the superhydrophobic surface has been monitored by a high speed camera. The coated layer on the droplet surface damps the violent oscillation and accelerates its decay, shortens the contact time and oscillation period. The results suggest that the adsorption of nanoparticles on droplet surface increases the effective surface tension of droplet. The viscoelastic properties of the enwrapping particle layer play an important role in the decay of droplet oscillation.

Microstructure and Properties of Fe–Al/Cr<sub>3</sub>C<sub>2</sub>RE Composite Coating Produced by HVFS

Fe–Al/Cr3C2composite coatings produced from high-velocity flame spraying (HVFS) are Fe–Al intermetallic composite coatings with remarkable room-temperature and high-temperature properties. However, Fe–Al/Cr3C2composite coatings have a Cr3C2content of 50%. This causes the coatings to become porous and limits its room-temperature and high-temperature properties. In order to improve microstructure and properties of Fe–Al/Cr3C2composite coatings, Fe–Al/Cr3C2RE, including Fe–Al/Cr3C2and CeO2, is sprayed by HVFS technology onto AISI 1020 steel. The properties including bonding strength and high-temperature corrosion-resistance of Fe–Al/Cr3C2RE composite coating are tested at 25°C and 650 °C. For comparison, two other materials, substrate AISI 1020 steel and Fe–Al/Cr3C2composite coating, are tested under the same experimental conditions. The microstructures of the coatings are analyzed by scanning electronic microscopy (SEM), the cross-section morphology of Fe–Al/Cr3C2RE composite coating is analyzed by energy-dispersive spectroscopy (EDS), and the existing states of oxides are analyzed by transmission electron microscopy (TEM). The phases of the composite coating after corrosion are analyzed by X-ray diffraction (XRD). The results demonstrate that the properties of Fe–Al/Cr3C2RE composite coatings is better than that of either AISI 1020 steel or the Fe–Al/Cr3C2composite coating. CeO2is a surface-active agent, and it significantly improves the microstructure and properties of Fe–Al/Cr3C2RE composite coating. CeO2improves the bonding strength of Fe–Al/Cr3C2RE composite coating by reducing the surface tension of droplet and enhancing its fluidity as well as wetting capacity on the surface of the substrate, decreasing the internal stress of coating.Adding CeO2to the coating produces Al2O3and Cr2O3oxide films, which protect the substrate AISI 1020 steel from corrosion more efficiently.