Synthesis of silicon dioxide nanoparticles by sol-gel method for application in geopolymer composites

The advent of nanotechnology has revolutionized the majority of the sectors of science and technology [1]. Nanotechnology was introduced by Richard P Feynman in 1959 through a lecture on “There is plenty of room at the bottom”. It is the re-engineering of materials and devices by monitoring matter at an atomic scale [2].  Synthesis of pure and nano-sized particles is still a challenge despite many pre-established processes. The size of the nanoparticle is of prime importance as the finer nanoparticles exhibit quicker reactions due to increased surface area. A pure material is essential to produce a good end product without any impurities. Specific properties of nanoparticles can be monitored at the nanoscale and it is influenced by the synthesis procedure. Nanoparticles are synthesized by various methods such as gas condensation, vacuum deposition & vaporization, chemical vapor deposition & condensation, mechanical attrition, chemical precipitation, sol-gel synthesis, and electrodeposition [3]. The sol-gel method of synthesis can control the size and morphology of nanoparticles. It is one of the simplest ways to produce nano-sized particles in the pure form via a bottom-up approach. The sol-gel method of synthesis has added advantages over other methods because of its versatility, homogeneity, and modification of particle properties by modifying the parameters of synthesis [4]. Nano silica has gained importance because of its low density, mechanical and chemical stability. The use of nano-silica in cement/geopolymer composites would enhance the workability, strength, density, and durability. It also reduces setting time and porosity [5]. In this study, silica nanoparticles were synthesized by the sol-gel method. Sodium Silicate was used as precursor with ethanol as solvent. CTAB and Ammonia were used as surfactant and reducing agent respectively. It was characterized using Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), Energy dispersive X-ray analysis (EDAX), and Particle size distribution (PSD). The SEM and EDAX data are shown in figure 1. The silica nanoparticles obtained were mostly spherical with an average particle size distribution of 26nm and 99% purity. The synthesized silica nanoparticles were incorporated in geopolymer composites to study the impact of nanoparticles on the properties of the composites.