Effect of Relative Humidity on the Thickness of Assembled Silica Colloidal Crystal Films

In order for the colloidal crystal films to be better applied, the influence of relative humidity on the preparation of silica colloidal crystal (SCC) films was systematically studied to solve the problem of different thicknesses of SCC films prepared by different batches under the conditions with the same temperature, concentration of suspension and diameter of the particles. SCC films with 190 nm particles were prepared by static vertical deposition method under different humidity regulated by saturated salt solutions, and the thickness of the films was obtained by an interferometric method. The results showed that the increase in humidity would reduce the thickness of the prepared films, which was believed to be caused by the decrease in evaporation rate after the wetting film absorbs water vapor. A new formula for calculating film thickness was proposed and verified from a series of experiments. With the control of humidity, high-quality SCC films with controlled thickness can be repeatedly prepared.

APPLICATION OF THE JET SCHEME AND FLOTATION MODE WITH A VAPOR-AIR MIXTURE DURING GOLD-BEARING ORES ENRICHMENT

Increasing the economic efficiency of enrichment of refractory gold-bearing ores is possible by reducing the cost of opening sulphide gold-bearing concentrates by reducing the yield of flotation concentrate sent to pyro- or hydrometallurgical processing. It is important to maintain the achieved level of gold recovery into concentrate with a lower concentrate yield. In order to achieve this goal, the gold content in the main flotation operation is increased by mixing the rough concentrate separated from ½ part of the ore feed with another ½ part of it. Mixing in the flotation operation of products with a high level of wash ability (ability to separate) – initial feed and rough concentrate – is identical to an increase in the content of the extractable component in the original ore. In accordance with the new regime of flotation, the process is carried out in cold slurry with bubbles filled with hot steam. The physical basis of the new flotation regime is the dependence of the surface properties of air bubbles and surface forces that determine the stability of the liquid film separating the bubble and the particle on the temperature, which increases due to the heat of the vapor-liquid phase transition. Radial oscillations of the bubble surface as a result of pressure pulsations during condensation and vapor evaporation and surface thermal flows of liquid in the wetting film are factors that provide an increase in the completeness of gold recovery and the selectivity of flotation adhesion obtained in ore flotation experiments. In laboratory conditions, a comparison was made of the indicators obtained during the dressing of gold-bearing ores according to the factory and new schemes. It was revealed that the use of the developed technology allows, with a lower concentrate yield, to obtain an increase of 7.06% abs. extraction of gold into a concentrate of the best quality. A decrease in gold losses with flotation tailings is a consequence of an increase in the number of particles reaching the bubble surface due to radial oscillations of its surface and a weakening of the stability of the wetting film by the thermo-capillary mechanism. An increase in adhesion selectivity can be interpreted using the concept of surface forces of structural origin – an increase in the forces of hydrophobic attraction and hydrophilic repulsion with increasing temperature. The interaction of vapor bubbles with nanobubbles on the surface of the solid phase (wetting by the Cassie-Baxter mechanism) ensures efficient particle recovery by the coalescence mechanism of flotation.

Effect of Dodecane-Oleic Acid Collector Mixture on the Evolution of Wetting Film between Air Bubble and Low-Rank Coal

The wetting film evolution process is essential for flotation, especially in bubble–particle attachment. A mixed collector has been proved effective in promoting flotation. In this paper, the effect of a mixed collector (MC) composed by n-dodecane (D) and oleic acid (OA) on wetting film evolution was investigated using the extended Derjagin–Landau–Verwey–Overbeek (EDLVO) theory, the Stefan–Reynolds model, induction time, and zeta potential measurement. The hydrophobic force constant between bubble and coal treated by different collectors was analyzed. The results showed that MC was superior in reducing the induction time and increasing the zeta potential. When bubbles interacted with coal treated by MC, they had relatively low interaction energy, high critical film thickness, and high drainage rate. The order of hydrophobic force constant was no reagent < D < OA < MC. It indicated that the hydrophobic interaction between bubbles and coal particles treated by MC was the strongest because of the synergistic effect of D and OA.

Wetting of a solid surface by active matter

Kinetic Monte Carlo simulations of an active lattice gas model indicate that the wetting film diverges in the whole range of activities considered, i.e. that the solid surface is always wet at the MIPS phase boundary.

Inhibiting the Segregation of Germanium in Silver Nanolayers

It is generally acknowledged that using germanium as a wetting film for silver nanolayers decreases the surface roughness of the metal. However, germanium atoms also tend to segregate towards the surface of silver films, increasing ohmic losses in the structure. Here we propose an Au/Ge/Ag based structure where the segregation of germanium in silver is inhibited. X-ray photoelectron spectroscopy (XPS) results show that for the Au/Ge/Ag system, the surface concentration of germanium drops by an order of magnitude relative to multilayers containing only one type of metal (Ag or Au). We have also observed that the time-dependent decrease in the reflectivity due to localized surface plasmon excitation is less prominent in the case of the Au/Ge/Ag structure than in the case of Ag/Ge/Ag. We provide XPS as well as optical reflectometry results to support that claim.

Turning autophobic wetting on biomimetic surfaces into complete wetting by wetting additives

Autophobicity or pseudo partial wetting, a phenomenon of a liquid not spreading on its own monolayer, is characterized by an energy barrier that prevents the growth of a wetting film beyond the monolayer thickness, which additionally may have an impact on the conditioning performance of films.