Effects of Surfactants on the Microstructure Characteristics of Alumina Microfibers

Abstract

Alumina microfibers were synthesized using different types of surfactants (rosin-based quaternary ammonium salt, sodium dodecyl sulphate and triblock copolymer P123 as directing agents. Their structures were characterized with X-ray diffraction, N₂ adsorption and desorption, field-emission scanning electron microscope and transmission electron microscopy to investigate the effects of surfactants on the microstructure characteristics of alumina microfibers. The surfactants can not change the intrinsic crystal structure of the as-syntheiszed ammonium aluminium carbonate hydroxide with the composition (NH₄[Al(OH)₂CO₃]) (AACH), but they will alter the way of the growth of the AACH nanocrystals. Because of the strong electrostatic interaction between AACH nanocrystals and ionic surfactants (rosin-based quaternary ammonium salt and sodium dodecyl sulphate), the AACH microfibers grew too fast on the surfactant micelles to form regular fibrous morphologies. When the non-ionic surfactant P123 was used as the template, due to the weak hydrogen bond interaction, the AACH microfibers grew at an appropriate speed to form a uniform fibrous morphology.