Tailored Silica Macrocellular Foams: Combining Limited Coalescence‐Based Pickering Emulsion and Sol–Gel Process

Abstract

Solid‐sate monolithic macrocellular foams are synthesized by mineralizing the continuous phase of oil‐in‐water Pickering emulsions, used as templates, with the sol–gel process. For the first time, taking advantage of the limited coalescence phenomenon occurring in emulsions stabilized by solid particles, concentrated emulsions with calibrated drop size are produced, leading to the synthesis of monolithic foams with nearly monodisperse macroscopic voids. Such a strategy allows independent tuning of the macrocellular void diameters from 20 to 800 μm and the diameter of the windows connecting adjacent cells. The obtained macrocellular foams also bear micro‐ and mesoporosity, leading to Brunauer, Emmet and Teller (BET) surface area values between 700 and 900 m2 g−1 with a good mesopores monodispersity.

Colloidal processing: enabling complex shaped ceramics with unique multiscale structures

“…In addition to filters and membranes for separation processes and engineered thermal and acoustic insulation, porous ceramics are gaining attention in the medical field to encapsulate and release substances in the human body, grow cells and tissues in tailored scaffolds, or act as microfiltration membranes for viruses . The other growing applications are in catalysis, chemical sensors, and electrodes for fuel cells and lithium air batteries and other dielectrical and optical applications …”

“…The emulsion can be shaped into a component by solvent drying or in combination with a quick setting technique such as gelcasting or freeze casting. Typically, emulsion templating is combined with sol‐gel routes to create a dual template process that results in porous structures of Al 2 O 3, ZrO 2 and SiO 2, with narrow pore size distributions in the lower ranges of the macroporosity spectrum, between 2 and 5 μm. This approach has also been used with mixtures of polysiloxanes and polycarboxylosanes to generate a porous scaffold that after calcination leads to SiOC or SiC ceramics.…”

Porous shape memory polymers: Design and applications

“…Surfactant‐free pickering HIPES are stabilized at the oil/water interface by solid amphiphilic particles that migrate and self‐assemble at the boundary layer . These emulsions approach monodisperse void sizes, and resist coalescence due to higher nanoparticle desorption energies when compared to traditional surfactants . Additional information on PolyHIPEs and Pickering HIPEs can be found in comprehensive reviews by Silverstein …”

Thermomagnetically Responsive γ‐Fe2O3@Wax@SiO2 Sub‐Micrometer Capsules

“…Assuming that all NPs were adsorbed, we defined the surface coverage C by a geometrical relation linking the amount of particles and droplets size where m particles is the mass of particles, d p is their diameter, ρ p is their density, D [3, 2] is the surface‐averaged diameter of droplets, and V d is the total dispersed‐phase volume. More precisely, C corresponds to the ratio between the interfacial area that the particles may cover and the total interfacial area originating from the emulsion, S inter , which is defined as S inter = 6 V d / D [3, 2] with D [3, 2] = / . Then we can estimate the average amount of particle layers n by n = C /0.9, where 0.9 corresponds to the coverage for a dense monolayer .…”