The Synthesis Technology, Structure And Forming Mechanism Of Solvent-Free Nanofluids

Solvent-free nanofluids are actually nanoparticle suspensions without solvents, according to which they are named self-suspended nanoparticles. At or near room temperature, these nanofluids can exhibit liquid-like behavior in the absence of any solvent. The unexpected nature of solvent-free nanofluids originates from the inherent structure of their building blocks, each of which is comprised of a rigid nanoparticle core and a soft organic shell. Since the organic moieties are covalently grafted to the nanoparticle core, and the core/shell structure remains stable under physical interfering, the whole system is macroscopically single-component.In this work, CaCO3 nanoparticles were attached with-OH groups via adjusting the pH value, and then covalently grafted with a quaternary ammonium organosilane (DC5700) to render CaCO3 nanoparticles cationic. When the ionically modified CaCO3 nanoparticles were electrostaticlly combined with a poly(ethylene glycol)(PEG)-tailed sulfonate anion (NPES), the solvent-free CaCO3 nanofluids were prepared. The rheological results confirmed the liquid-like behavior of the as-prepared solvent-free CaCO3 nanofluids, and the TEM images revealed the essence of the especial rheological property of this hybrid nanostructure by presenting an organic shell of 6nm in thickness that enabled the solid inorganic core to move smoothly.Synthesis techniques of solvent-free nanofluids were optimized. Solvent-free SiO2 nanofluids prepared via ion extraction process and acid-base reaction process were investigated. Fourier-transform Infrared spectrum (FTIR), X-ray Diffraction (XRD), Thermal gravimetric analysis (TG), Transmission Electron Microscopy (TEM) and rheological property measurement were employed to characterize solvent-free SiO2 nanofluids prepared via ion extraction process. The results showed that the complete ion exchange can be achieved, and properties of the product were excellent. FTIR, XRD, TEM and rheological property measurement were employed to characterize solvent-free SiO2 nanofluids prepared via acid-base reaction process. The results showed that properties of the product were excellent as well.FTIR, Raman, TG, TEM and rheological property measurement were employed to characterize two types of solvent-free Multi-walled carbon nanotubes (MWCNTs) fluids prepared via ion extraction process and acid-base reaction process respectively. The results showed that:a) particle size and surface functional groups of nanostructures were both key factors to the property of solvent-free nanofluids; b) all the as-prepared solvent-free MWCNTs fluids samples exhibited soft glassy rheology that determined by the 1-dimentional shape of MWCNTs as well as the grafted organic moieties; c) organic shell with different shell thickness were observed in different samples; d) solvent-free MWCNTs fluids with different organic shell thickness showed different rheological properties, and the relationship between shell thickness and rheological property reflected the function of the organic moieties in the solvent-free nanofluids system.