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Porous materials with wrinkled surfaces could have broad applications in catalysis and adsorption. However, designing cellular ceramics with similar structures is challenging. Herein, we demonstrated the binary colloidal self-assembly of γ-Al 2 O 3 nanoparticle/silica gelation network for constructing such materials. The competitive effect between volume shrinkage and surface bend during water evaporation of silica gel contributed to wrinkled aperture surface. During calcination, silica nanoparticles were highly active to react with alumina to form mullite nanocrystals, bringing about high compressive strength at low relative densities. After calcining at 1350 °C, resultant products with hierarchical structure exhibited an outstanding compressive strength of 4.2 MPa, a relatively high surface area of 7.23 m2/g at a porosity level of 83.3%. The current strategy provides a feasible and affordable approach for producing high performance ceramic foams towards practical application fields in catalysis and adsorption. [ABSTRACT FROM AUTHOR]

Engineering highly porous SiC foams with interconnected cellular architecture and satisfactory compressive strength for the practical applications remains a challenging task. In the current work, SiC foams bonded by in-situ formed mullite phase were fabricated via polyurethane foaming using boehmite sol-coated SiC powder as the raw material. The strategy in the current work endowed the resultant products with ultrahigh porosity, interconnected pore structure, and a robust mullite bonding phase among the SiC particles. The resulting products with this cellular architecture possessed a high porosity level of 88.5% and maintained a robust compressive strength of 2.56 MPa. Our results showed that as-prepared products are promising for practical applications in the filtration, adsorption and catalytic areas. [ABSTRACT FROM AUTHOR]

Engineering high performance cellular ceramics with both ultralow density and satisfactory compressive strength for practical applications still represents a grand challenge. Herein, alumina-based cellular ceramics bonded by in-situ formed mullite phase were constructed by Al 2 O 3 –Si-boehmite particle-stabilized foams. The gelation of boehmite sol improved the stability and harnessed the deformation of dried Al 2 O 3 –Si composite foam. The oxidation of silicon and further generation of in-situ mullite phase enhanced the chemical bond between alumina particles on cell walls, resulting in the superior mechanical properties. As an exemplar, the resulting cellular ceramic possessed the robust compressive strength of 2.26 MPa at a high porosity of 87.8%. The gelation-assisted Al 2 O 3 –Si particle-stabilized foams provide a facile and convenient strategy for construction of composite ceramic foams with high porosity and robust strength. [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]

Constructing high-performance air filters for high-temperature particulate matter (PM) removal is of great importance but remains challenging. Here we demonstrate the ceramic foam-based filters via polyurethane (PU) foaming using diatomite and kaolin powder as the starting materials. Diatomite was grafted by dodecanedioic acid (DA) to improve the dispersity in the PU slurry. The calcined products demonstrated a hierarchical pore structure with multiple well-controlled micron-sized window pores on the cell wall of the sub-micron bubble. The resulting products exhibited a high removal efficiency (96.3%) at a pressure drop of 33 Pa. This research showed that as-prepared ceramic foams can be potentially used as new high-temperature filters for high-temperature PM removal. [ABSTRACT FROM AUTHOR]

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]