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We herein report a novel hierarchically porous ceramic foams derived from boehmite gel foams, which possess both high porosity and superior strength. The gel foams show excellent printability due to its predominant stability, high yield stress and storage modulus, which endows such foam material ideal ink for 3D printing lightweight and complex-shape materials via direct ink writing approach. The 3D printed ceramic foams possess programmable architecture assembled by porous filaments, uniform macro-pores with tunable size in the range of 4∼70 μm, as well as nanoscale pores in cell wall, after sintering at relatively low temperature of 1200–1300 °C. In this way, ceramic foams with high strength were achieved, attributed to the tiny grains, large amount of grain boundaries, uniform pores and hierarchical pore structure. Notably, the foams sintered below 1200 °C have significant advantage on specific surface area, which could reach up to 300-400 m2/g. [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]

A novel approach to fabricate mullite ceramic foams with high porosity and mechanical strength using fly ash hollow spheres (FAHSs) as the only raw material was reported for the first time, in which FAHSs served as both matrix and pore-forming agent. It was demonstrated that uniform FAHS ceramic foams without cracks could be fabricated by both direct stack sintering method and gel-casting route. The effect of sintering temperature on linear shrinkage, porosity, phase composition and mechanical properties was investigated. With the increase of sintering temperature from 1200 °C to 1350 °C, the fracture mechanism changed from fracturing along FAHSs to fracturing across FAHSs, and the compressive strength of the FAHS ceramic foams increased from 4.4 MPa to 33.4 MPa. The FAHS ceramic foams exhibited high porosity in the range of 73–81% and high mechanical strength, which benefited from the dense assembling of small FAHSs with natural diameter distribution and excellent wall-thickness uniformity. [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]