▎ 摘　　要

The dynamic viscosities of nanofluids containing oxygen-functionalized graphene nanoflakes (O-GNFs) were measured for concentrations ranging from 0.1 to 10 ppm under pressures from 0 to 30 MPag and temperatures from 0 to 10 degrees C. Water's viscosity dependence on temperature was not affected by the presence of O-GNFs, though the effective viscosity of the solution was reduced (termed non-Einsteinian viscosity) against common expectations. Hydrogen bond strength may have been reduced at the hydrophobic part of the O-GNF surface, whereas density fluctuations were enhanced. Therefore, larger sites of free volume may have formed, and weaker intermolecular interactions could allow for less-restricted diffusion into those sites, reducing the effective viscosity. The internal friction that would otherwise raise the solution viscosity could be overcome by these surface effects. Water's viscosity dependence on pressure was also not affected by O-GNFs, except at 10 ppm, where the shuttle effect may have increased the presence of hydrophobic methane bubbles in the solution. Under high pressures, the relative viscosity of the system remained non-Einsteinian at all temperatures except 2 degrees C. This may have been because the density anomaly of water was shifted to a colder temperature as the hydrogen bonding network was weaker. The phase transition from liquid to hydrate was identical to that of pure water, indicating that the presence of different stages of growth was not affected by the presence of O-GNFs. However, the times to reach a maximum viscosity were faster in O-GNF systems compared to pure water. This said, the hydrate formation limitations inherent to the measurement system were not overcome by the addition of O-GNFs. The times to application-relevant viscosity values were maximized in the 1 ppm system at 49.75% (200 mPa.s) and 31.93% (500 mPa.s) faster than the baseline. Therefore, the presence of O-GNFs allowed for shorter times to desired viscosities at lower driving forces than the baseline, improving the viability of the hydrate technologies to which they can be added.