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Ultralight ceramic foam materials with high porosity play an important role in increasingly hi‐tech areas due to the combinative merit of ceramic material and highly porous structure. So far, it remains challenging to fabricate alumina ceramic foams with extremely high porosity and high specific surface area that are comparable to aerogel materials by employing a low cost, eco‐friendly and convenient approach. For the first time, we propose the preparation of aerogel‐like ceramic foams with nanoscale cell wall and unprecedentedly high porosity using boehmite sol as both ceramic source and bubble interface stabilizer, based on sol nanoparticles stabilized foams using sodium lauryl sulfate (SDS) as modifier. The obtained ultra‐stable sol foams allow for the achievement of bulk foams with ultrathin cell wall with thickness in the range of 30‐90 nm, super‐high porosity up to 99%, and large specific surface area of 280 m2/g, which is attributed to the well‐organized assembly of nanoparticles at the liquid/air interfaces. This novel foam material demonstrates excellent adsorption ability for polar volatile organic gases (VOCs) due to its extremely high porosity and large specific surface area. Ultralgiht cellular ceramic foams composed of uniformly assembled nanoparticles with nanoscale cell wall. [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]

An innovative approach for fabricating porous alumina ceramics (PACs) with improved mechanical and thermal properties using walnut shell powders as pore-forming agent combined with alumina sol impregnation is reported in the present work. It is demonstrated that uniform distribution of spherical pores can be observed in as-prepared PACs by using above technical route. The decrease of walnut shell powder sizes significantly promotes the enhancement of crushing strength and reduction of thermal conductivity of the PACs. Meanwhile, the impregnated alumina sol is favoring for the formation of spherical micro-pores, then further improves their mechanical and thermal insulation performances. The lowest thermal conductivity and highest crushing strength of resulting sample reach 0.16 W/m K and 29.2 MPa, respectively. This novel method offers new possibilities to fabricate high-quality PACs. [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]

Abstract: A novel method for fabrication of highly porous barium strontium titanate (BST) ceramic foams based on particle‐stabilized foaming method was developed for the first time, in which propyl gallate (PG) was employed as BST particle modifier. The results showed that the stability of wet BST foams closely depends on the pH value and PG concentration, which could be explained by the adsorption behavior of PG on BST particle surface. BST ceramic foams with dense, uniform, and closed pore and defect‐free wall were obtained. The pore size and porosity can be well controlled by adjusting solid loading and sintering temperature. It was revealed that not only sintering temperature but also solid loading significantly influenced the growth of BST grain. The BST ceramic foams exhibited high porosity in the range of 81%‐95%, low dielectric constant in the range of 47‐150, and low dielectric loss below 0.0025. The BST ceramic foams with higher porosity presented a tendency of lower dielectric constant and the fitting results indicated that the natural logarithm of dielectric constant was linear correlated with porosity. [ABSTRACT FROM AUTHOR]

In order to reduce thermal conductivity but to exhibit better mechanical properties of porous alumina ceramics (PACs), a novel approach, based on the modification of pore structures (i.e. mean pore size, micro-pore proportions and pore shape factor) by impregnation of alumina sol, is reported in the present work. The properties of as-impregnated samples were compared with commercial alumina hollowsphere bricks. Results show that impregnation of alumina sol in PACs has a positive influence on pore structures, leading to a superior strength and a lower thermal conductivity. In particular, when 8 wt% alumina sol solid content is impregnated, the crushing strength (35.3 MPa) and thermal conductivity (0.15 W/m K at 200 °C) of sample are much better than that of the commercial alumina hollowsphere bricks. This novel method for excellent PACs provides promising applications as insulating lining materials in the fields of industrial furnace. [ABSTRACT FROM AUTHOR]

Dense silicon carbide ceramics using chemical treated powder by DCC via dispersant reaction method and liquid phase sintering was reported. Ammonium peroxydisulfate ((NH 4 ) 2 S 2 O 8 ) and ammonium carbonate ((NH 4 ) 2 CO 3 ) were used as acid and base solutions to treat the silicon carbide powder, respectively. Influence of silicon carbide powder with chemical treatment on the preparation of silicon carbide suspension was studied. It was indicated that 50 vol% and 52 vol% silicon carbide suspensions with viscosities of 0.71 Pa s and 0.80 Pa s could be prepared using acid and base treated powders. Influence of silicon carbide powder with chemical treatment on the coagulation process and properties of green bodies and sintered ceramics were studied. It was indicated that silicon carbide green bodies with compressive strength of 1.13 MPa could be prepared using base treated powder. Dense silicon carbide ceramics with relative density above 99.3% and flexural strength of 697 ± 30 MPa had been prepared by DCC via dispersant reaction and liquid phase sintering using Al 2 O 3 and Y 2 O 3 as additives at 1950 °C for 2 h. [ABSTRACT FROM AUTHOR]

We prepared porous Si 3 N 4 ceramics with highly ordered and unidirectionally aligned channels by the self-organization method using an alginate template. The obtained samples show uniform pore distribution, high cell density, good mechanical strength and hierarchical pore structure. A great number of long fibrous β-Si 3 N 4 grains protrude into channels, and other short length fibrous β-Si 3 N 4 grains interlock within channel walls forming a peculiar hierarchical pore structure. The pore size, thickness of channel walls, cell density, porosity and mechanical properties of the sintered porous Si 3 N 4 ceramics could be controlled by choosing different solid loadings, whereas β-Si 3 N 4 grains growth could be controlled by adopting different sinter temperatures. [ABSTRACT FROM AUTHOR]