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Compressive strength is one of the most important mechanical properties for ceramic foams but the dependence of compressive strength of highly porous ceramic foams on porosity remains unclear up to now, especially for the ceramic foams with porosity above 94%. In this paper, the relationship between compressive strength and porosity of ceramic foams with high porosity in the range of 79–98% was studied for the first time. The alumina ceramic foams and zirconia foams were prepared by particle-stabilized foaming method using sodium dodecyl sulfonate (SDS) as foaming agent. It was found that the function relation between compressive strength and porosity depended on porosity level. Specifically, compressive strength of ceramic foams fitted well with Rice Model when the porosity ranged from 79% to 94%. When the porosity increased above 95%, compressive strength of ceramic foams showed linear relation to porosity, which was probably due to the characteristic of highly porous ceramic foams with thin and lamellate cell wall. [ABSTRACT FROM AUTHOR]

Ultralight ceramics with striking mechanical properties and improved pore connectivity could have wide applications in areas ranging from catalyst support to hot gas filtration. However, creating such materials has proven to be a challenging target. This work demonstrated a novel methodology to prepare porous MgAl 2 O 4 ceramics by calcining gelled MgO–Al 2 O 3 –SiO 2 particle-stabilized foams. The striking green strength of dried foams can be achieved as a consequence of MgO hydration and subsequent formation of gelled Mg(OH) 2 and MgO–SiO 2 –H 2 O skeleton. The decomposition of colloidal substance at elevated temperature resulted in the formation of small pores on the cell wall, thus forming the hierarchical porous architecture and improving the pore connectivity. The highly porous MgAl 2 O 4 ceramics fired at 1600°C possessed the integrated properties of ultrahigh porosity (87.0%), improved pore connectivity and satisfactory compressive strength (7.93 MPa), showing great potential to be used in multiple industrial fields. [ABSTRACT FROM AUTHOR]

Abstract In the present work, Al 2 O 3 -Si 3 N 4 porous ceramics with a cactus-like architecture were fabricated by calcining Al 2 O 3 -Si binary particle-stabilized foams in the nitrogen atmosphere. A large number of acicular Si 3 N 4 nanobelts were constructed on the surface of cell walls as a consequence of CVD process to achieve an interlaced network. Such structure was beneficial to realize a high capture efficiency of particulate matters (PM) during filtration. Resultant products having a bulk density of 0.38 g/cm3 at an apparent porosity of 86% can potentially be applied as the air filters in environment field. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Aqueous ceramic particle-stabilized foams with UV light response are prepared. • Photocurable particle-stabilized emulsions with controllable structure are achieved. • The colloid foams/emulsions demonstrate excellent stability and photocuring ability. • Rapid and scalable synthesis of ceramic capsules is developed based on the emulsions. Abstract We herein report the design and preparation of ceramic particle-stabilized emulsions/foams with distinct ultraviolet light (UV) response, which can be used for the rapid fabrication of ceramic foams with complex shape, for synthesis of ceramic hollow spheres, and can potentially be used for 3D printing lightweight and hierarchical ceramics with porous skeleton. Photocurable foams/emulsions stabilized by ceramic particles are achieved for the first time using photosensitive oligomer as oil phase and/or using photosensitive aqueous solution containing acrylamide monomer as water phase. Four kinds of photocurable emulsions are demonstrated by adjusting emulsion structure and photosensitive phase. We further synthesize internal multiple-pore structured capsules and lightweight nanoparticle-assembled capsules in micron-scale based on the photocurable particle-stabilized, by separating emulsion into small droplets via diluting and stirring, followed by rapid curing under UV. This new strategy may potentially open opportunities for the rapid and cost-effective synthesis of high-output ceramic capsule materials. The synthesized thin-shell alumina capsules exhibit large specific area surface of 323.18 m2/g as well as uniform mesoporous structure in shell with average pore diameter of 3.4 nm, which has potential application in the fields of adsorption, load and release of materials and thermal insulation. [ABSTRACT FROM AUTHOR]

Abstract We reveal that zeta potential has a notable effect on properties of foamed suspension, which remains poorly explored. It is demonstrated low zeta potential is beneficial for foam stability, and the experimental results show that absolute value of zeta potential of 30–40 mV is the boundary between stable foams and unstable foams. High zeta potential above 40 mV gives rise to instability of foamed colloidal suspension, owing to strong interparticle repulsion force that prevents particles from forming a closely packed particle network at liquid/air interfaces. Besides, it is found that high zeta potential leads to low foamability of foamed colloidal suspension. It is also demonstrated herein that stable and uniform foams with thin and homogeneous-thickness wall without agglomerates can be prepared at the isoelectric point (IEP) using long-chain surfactant, which generates weak agglomerated particles that can be re-separated to monodisperse particles due to the steric hindrance effect of surfactant. [ABSTRACT FROM AUTHOR]