Deposition of Aluminium Oxide Modified Core-shell Silica Particles onto Silica Surfaces

Abstract

Modification of surfaces is of great interest to fundamental research and industrialapplication. Inorganic particles such as silica are of direct relevance to home andpersonal care industry. Although particles already enjoy a wide range of applications,there are ongoing studies to develop new applications based on novel surfacefunctionalities and particle interactions with other particles and substrate surfaces.Manipulation of surface charge properties is one of foremost handles in tuning particlesystem behaviour.In this study, the deposition of modified core-shell silica particles (Ludox CL) onto aflat silica surface was studied with increasing concentration of the particles in thedispersion and the results were compared with bare silica particles (Ludox HS). LudoxCL particles were silica spheres with their surfaces modified by reacting withaluminium chloride to form an outer coating of aluminium oxide. The modified silicaparticles were first characterised under different solvent conditions. Measurements ofparticle size and surface charge were performed and tracked with changes in pH andelectrolyte concentration. Particle deposition onto silica surface was then investigated atincreasing concentrations under changing pH and electrolyte conditions. Themorphology and amount of deposited material were observed and relevant techniqueswere used in order to shed light on the observed phenomena. In aqueous solution, thecoated silica particles manifested the surface properties of colloidal alumina with a highcationic Zeta potential at low pH values and an isoelectric point around pH 8.5-9.Increasing pH caused a steady process of leaching of aluminium ions, leading topreferential adsorption of the solvated cations to anionic silica surfaces and thusimpeding the deposition of silica particles. As a result of leaching of aluminium ions,the silica substrate was modified and this in turn influenced the morphology of thedeposited clusters.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jian Lu (Supervisor)