1D magnetic resonance imaging and low-field nuclear magnetic resonance relaxometry of water-based silica nanofluids

Abstract

The purpose of this research is to investigate 1-D Magnetic Resonance Imaging (MRI) and low-field Nuclear Magnetic Resonance (NMR) relaxation characteristics of silica nanofluids. The results show that presence of silica nanoparticles increases the MRI signal intensity and influences the NMR relaxation by shifting the relaxation peaks toward faster times compared to deionized water (DIW). Additionally, inversion recovery sequences show that nanoparticles reduce longitudinal relaxation time. For the tested nanofluid of EOR-12, signal intensity, longitudinal relaxation rate and transverse relaxation rate show a strong linear dependence on nanoparticle concentration with the highest enhancement of 1.75-fold, 2.57-fold and 3.20-fold, respectively compared to DIW. Additionally, investigation of the effect of nanoparticle size shows that below an optimal size, the MRI signal intensity and the NMR relaxation rates show a positive correlation with nanoparticle size but above the optimal size, the behavior reverses. For the nanoparticle with the optimal diameter, signal intensity, longitudinal relaxation rate and transverse relaxation rate enhancement was 2.21-fold, 4.44-fold and 4.45-fold, respectively compared to DIW. Application of the observed improvement in signal intensity to obtain the profile of the aqueous phase volume fraction in a Pickering emulsion shows a maximum error of 8% which indicates that the proposed technique can be applied for emulsion characterization with good accuracy.