Synthesis and Characterization of Ag and Silica (SiO2) Coated Ag Based Nanofluids

Abstract

The main objective of this thesis is to prepare stable nanofluids using Silver nanoparticles (SNPs)/water and silica coated silver nanoparticles/water system. Nanofluids have been prepared by single-step chemical reduction method starting with silver nitrate as a metal precursor. Controlled experimental conditions have been established to synthesize spherical shape SNPs. By using polyvinylpyrrolidone (PVP) as a surfactant, sterically stabilized distilled water based nanofluids is being prepared. As synthesized SNPs were coated with silica (SiO2) to obtain silica coated silver nanoparticles based silver nanofluids. SNPs and silica coted SNPs were characterized by X-ray diffraction (XRD), UV-visible spectroscopy, Dynamics light scattering (DLS), transmission electron microscopy (TEM), Fourier transform Infrared spectroscopy (FTIR). From the X-ray analysis it is clear that nanoparticles crystallized into face centered cubic (FCC) crystal structure. The peak broadening is a clear indicative of the formation of SNPs, which was further confirmed by TEM. UV-visible study confirms the formation of SNPs. DLS study revealed the hydrodynamics size for both the sample. TEM micrograph shows that the nanoparticle are polydisperse and spherical in shape. Formation of PVP and silica shell on the surface of silver nanoparticles was confirmed by FTIR spectroscopy. Thermal conductivity of both samples was measured at room temperature and variations of thermal conductivity with temperature were measured using KD2 pro thermal property analyzer. Thermal conductivity of both the nanofluids decreases with increasing temperature. The synthesized nanofluids may find applications in industrial cooling systems.