Colloidal suspensions of mesostructured silica

Licentiatavhandling, 2007

Mesoporous silica is a porous material with walls made of silica and pores in the size range of 2-50 nm. Since the silica most often is amorphous, the material lacks short range order but the pores may be arranged in different structures generating a long-range order. The main objective of this project has been to study and develop syntheses of mesoporous silica suitable for large scale applications. Therefore this licentiate thesis focuses on the development of a new synthesis of mesoporous silica based on a sodium silicate solution and a commercially available non-ionic surfactant. The synthesis results in a stable colloidal suspension of hexagonally mesostructured silica and the particle size of the material can be controlled within the range of 50-300 nm by the electrolyte concentration. Since the synthesis is based on near neutral conditions and cheap starting materials, it is also a suitable synthesis route for development towards industrial production and applications. Another important objective of the project is to obtain a better understanding of the formation of mesostructured materials and of the interaction between silica and non-ionic surfactants. This has been studied by changing several variables in the synthesis procedure and a mechanism for the particle formation is proposed. The mechanism is based on a burst nucleation process followed by growth through aggregation. The mesoorder of the particles is then achieved by reorganization within the particles.