Nanofluid Al₂O₃-H₂O evaporation: Energy and deposition patterns?

This study experimentally investigated the deposition patterns of Al2O3-H2O nanofluid droplets with mass concentration of 0.05%, 0.2%, 1% and 3% after evaporating on transparent glass substrate with temperature of 30 °C, 40 °C, 50 °C and 60 °C, obtaining three typical kinds of patterns: the peripheral ring, the thin uniform layer with a thicker ring at the periphery and the concentric circular respectively. With the increase of concentration, the uniform pattern embedded in the peripheral ring changes into a concentric circular pattern gradually. The flow velocities corresponding to the three typical forces were solved and the results are 10^-3<Vma/Vrad-a<10^-2 and 10^-28<VDLVO+/Vrad-a<10^-5 (Marangoni, Vma, the integral mean value of the entire radius Vrad-a and the velocity caused by DLVO force VDLDO+). This indicated that the radial flow played a dominant role in the formation of the deposition pattern.