Factors influencing the formation of hollow ceramic microspheres by water extraction of colloidal droplets

Abstract

Hollow ceramic microspheres of A1 2 O 3 , SiO 2 , and mullite have been prepared by the combination of an emulsion technique with a water extraction sol-gel method. Concentration of sol, initial droplet size, and water extraction rate of the system are found to be the important process parameters controlling the size and wall thickness of the hollow microspheres, and their influences are shown. A model that correlates the morphology of microspheres to concentration and water extraction rate is proposed and is in good agreement with the experimental observations. The capability and limitation of this process for forming hollow microspheres are demonstrated. It was shown that hollow microspheres with sizes greater than 5 fim could be readily prepared, while a limitation was met for sizes less than 1 /xm, in which case solid microspheres were normally formed.

Characterization of hydrated silicate glass microballoons

“…[6][7][8][9][10][11][12] Vitreous hollow microspheres, generally called glass microballoons, have been widely used as fillers. 14 Recently, an advanced electric insulation technology 16 has required ceramic/glass microballoons with maximum diameter of less than 10 mm. 14 Recently, an advanced electric insulation technology 16 has required ceramic/glass microballoons with maximum diameter of less than 10 mm.…”

Preparation of Anatase Hollow TiO2 Spheres and Their Photocatalytic Activity in the Photodegradation of Chlorpyrifos

“…This is because of their immense potential, owing to the favorable characteristics of having low density, large specific area, good mechanical and thermal stability, surface permeability. [1][2][3][4][5][6] In recent times, considerable efforts have been made to fabricate hollow titania (TiO 2 ) structures due to their potential applications in photocatalysis, 7 drug delivery, catalyst support and so on. Methods such as templating, 8,9 polymer-induced, 10 sol-gel 11 and hydrothermal 12,13 have been used for the production of hollow TiO 2 spheres.…”

Thermal and Structural Characterization of TiO2 and TiO2/Polymer Micro Hollow Spheres

“…Soft templates include emulsion droplets and vesicles whereas hard templates are organic or inorganic particles. Emulsion droplets as templates are used in such applications as the emulsion extraction method [4] and the hydrolyzation of alkoxides from the inside of oil-in-water emulsions [5]. In template sacrificial methods, different hard template coating processes such as layer-by-layer techniques, sol-gel methods, liquid phase deposition, and forced hydrolysis have all been investigated [6][7][8][9][10][11].…”