Plateau boundary blocking effect of Nano-SiO2 on foam properties of Gemini fluorocarbon and hydrocarbon surfactant mixed solution

To explore the effect of nanoparticles on the foam performances of mixed surfactant solution, nano-SiO2 particles (NPs) were added to Gemini short-chain fluorocarbon (Gemini) and hydrocarbon (LAMC) surfactants to prepare the mixed dispersion of nanoparticles and surfactants. The surface activity, dynamic viscosity, electrical con-ductivity, foamability, and foam stability of mixed dispersions with different concentrations of NPs were studied. The results showed that with increasing NPs concentration, the electrical conductivity and foamability gradually decreased, whereas the surface activity and dynamic viscosity increased slightly. The effect of NPs on the foam stability depends on their filling and blocking mechanisms in the plateau boundaries formed by the liquid films. When the NPs concentration is lower than 1 %, adding NPs reduces the foam's electrostatic energy, while the NP network structure cannot be formed in the plateau boundary. Consequently, the foam drainage and coarsening are accelerated, resulting in a decrease in foam stability of up to 142.4 %. When the NPs concentration is higher than 1 %, many NPs form the NP network, which fills and blocks the plateau boundary. The blockage restrains the foam drainage and coarsening, thus increasing foam stability up to 64.2 % in the current set of experiments.