Strength enhancement of ultralight alumina‐dried foams from particle‐stabilized foams with assistance of agar and PVA

Abstract

The weak compressive strength of dried ceramic foams is a disadvantage of fabricating ultralight ceramic foams, especially for the ceramic foams with porosity exceeding 95%. In this study, dried alumina foams were enhanced by agar and PVA‐freezing‐thawing using sodium dodecyl sulfate as surfactant. It is found that the two additives have no negative influence on adsorption of sodium dodecyl sulfate on alumina particles as well as the hydrophobic character of alumina particles. Stable alumina particle‐stabilized foams were prepared with less than 0.5 wt% agar and 1.0 wt% PVA. High additive concentration above the critical values weakens stability of wet foams, which is probably due to the aggregate of alumina particles caused by long‐chain molecules connecting. The compressive strength of dried alumina foams has a significant improvement with the employment of agar and PVA‐freezing‐thawing. The dried foams prepared with 1wt% PVA assisted by freezing‐thawing has porosity of 97.1% and compressive strength of 0.16 MPa, which could maintain integrity of dried foams without destruction in the fabricating process.

Ultrahigh‐strength alumina ceramic foams via gelation of foamed boehmite sol

“…The porosity and compressive strength of dried foams prepared by different techniques are compared in Table . The method in present work can achieve splendid compressive strength of dried foams through gelation, thus meeting the requirement for mechanical processing, transportation and industrial production.…”

Controlling the Pore Size and Connectivity of Alumina-Particle-Stabilized Foams Using Sodium Dodecyl Sulfate: Role of Surfactant Concentration

“…According to Table S1, the Hamaker constant of alumina, air, and water was confirmed as A 11 = 5.30 × 10 –20 J, A 22 = 0 J, and A 33 = 4.38 × 10 –20 J, respectively. − The combined Hamaker constant, A 132 , was found to be −4.38 × 10 –21 J for the alumina–water-bubble system; A 132 value is negative because the Hamaker constant for air is zero. The F vdW of the alumina particle–air bubble could be calculated using eq .…”

Ceramic foams with highly open channel structure from direct foaming method in combination with hollow spheres as pore-former.

“…As illustrated in Figure 1, the foams are subjected to solidification with the assistance of agar molecules in the case of ZrO 2 based foams [11,12], and rapid gelation of boehmite nanoparticles was triggered by decreasing pH in the case of Al 2 O 3 based foams [13]. Therefore, the dried foams exhibit favorable strength, that keeps the whole porous green body holding together and be free of breaking.…”