Content area
Full text
ABSTRACT
This study is focused on synthesis of nano-colloidal silica via alkaline water glass solution. Sodium ions of water glass were removed by cation exchanging in a resin column to obtain the silicic acid which was titrated to the solution of sodium silicate. Concentration of the colloidal silica and pH value of the solutions were controlled using different concentrations of alkaline sodium silicate and silicic acid solutions in constant temperature and titration rate. The synthesized colloidal silica was characterized by Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), X-Ray powder Diffraction (XRD), Accelerated Surface Area and Porosimetry analyzer (ASAP) and Gravimetric method. The results showed that the average particle size of colloids and their stability were also influenced by various important factors such as pH, Temperature, Concentrations of alkaline sodium silicate and silicic acid solutions. The results showed that the synthesized nano-colloidal silica suspensions in concentration up to 25 wt.% of SiO^sub 2^ with average particle sizes in range of 23 to100 nm are stable more than one year. Also, surface area and pore volume of the prepared spherical colloidal silica particles were160 m^sup 2^/g and 0.27 cm^sup 2^/g, respectively.
Keywords: Nano-colloidal silica; Water glass solution; particle size; Silicic acid; Sodium silicate.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION
Colloidal silica is the dispersion of fine amorphous SiO2 and typically spherical silica particles in a liquid phase. There are many grades of colloidal silica, but all of them are composed of silica particles ranging in size from about 3 nm up to about 150 nm. They have been known as stable suspensions in water, even at a very dilute concentration, that lasts for more than one-half year. These products are often called precipitated silica or silica sols. Today, colloidal silica dispersions are available in a variety of grades determined by particle size, structure, concentration, pH, surface charge and surface modification[1].
Colloidal silica is one of the few materials that can enhance glass adhesion in a resin base coating[2]. They are one of the most promising candidates that can be used as high temperature binder for inorganic paint, abrasive particles for mechanical polishing of silicon wafers[3-4], drainage aid in paper making [5] and abrasion-resistant coatings[6]. They can also be applied in model making for investment...