ADSORPTION OF DODECYLBENZENESULFONIC ACID ON THE ALUMINA PARTICLES IN THE PREPARATION OF ALUMINA FOAM

Partially hydrophobized particles of α-Al₂O₃ were used to prepare the alumina foams. Dodecylbenzenesulfonic acid (DBSA) was applied to the hydrophobized surface of alumina particles. The infrared spectroscopy provided the evidence of the interaction (adsorption) of DBSA on the alumina surface. The quantity of DBSA adsorbed on the alumina particles was determined using Lambert-Beer law by measuring UV-VIS spectra. The mechanisms of DBSA adsorption on the surface of alumina particles may be attributed to (1) electrostatic interactions or (2) specific chemical reactions between the surfactant and the surface hydroxyl groups. Adsorption of DBSA on the alumina particles is strongly influenced by the pH of suspensions. The quantity of DBSA is not sufficient to hydrophobize alumina particles at pH up to about pH 9.5, as the electrostatic repulsion forces between the sulfonic group of DBSA and the alumina surface prevailed and the DBSA acts only as a surfactant. The foams were sintered at 1400 °C, 1450 °C, 1500 °C, 1550 °C and 1600 °C. The optimal sintering temperature was found to be 1550 °C. The maximal compressive strength of the alumina foams was ∼ 300 kPa while its porosity was relatively high (96.7 %)

PROPERTIES OF Al2O3 FOAMS OPTIMIZED BY FACTORIAL DESIGN

Alumina foam was prepared by the direct foaming method. The foam was stabilized by in situ partially hydrophobized particles of Al2O3. Dodecylbenzenesulphonic acid was used for hydrophobization and it also acted as a foaming agent. The composition of the starting suspensions (Al2O3, boehmite, dodecylbenzenesulphonic acid and water) were varied according to factorial design. The resulting properties observed were: foam ratio, foam shrinkage on drying and sintering, bulk density and porosity of ceramic foams, average pore size and compressive strength. The final properties of foams dependent on statistically significant factors (boehmite, dodecylbenzenesulphonic acid) were evaluated by common software. The foam ratio decreased and the bulk density of the alumina foams increased with increasing quantity of the dodecylbenzenesulphonic acid (0.1-0.2 wt.%). Bulk density of alumina foams ranged from 88 to 155 kg/m3 and average pore size reached 111 μm to 215 μm depending on the quantity of the dodecylbenzenesulphonic acid. The microstructure of ceramic foams reached high porosities ranging from 96 to 98 %. The compressive strength of the alumina foams increased with increasing quantity of boehmite (1-3 wt.%) and it reached values of 333 kPa