Mostly, when I measure the viscosity of liquid material at constant shear rate for 10 min , the value does not change with time . But, during the measurement of viscosity of nanocomposite fluid at constant shear rate, I noticed the viscosity changes between two values in the regular pattern.
Howdy Pashupati Pokharel,
I suggest that you consider the shape of your nanocomposite particles and their behavior in a shear flow. If the particles are "tumbling" in the shear they might be affecting momentum transfer. The observation that the viscosity changes between two values may be due to changing shear stress as the particles tumble and align in different orientations.
Your observation is a surprise, it was unexpected, an opportunity for a larger awareness. My offering is a speculation based on extensive study of shear in fluids and near-total ignorance of nanocomposite fluids. I hope it opens a line of inquiry worth pursuing.
Happy Trails, Len
is your nano particles in the form of nano tube...then the forces affects the orientation of the nano tubes, good study for creating good lubricants or hydraulic fluids
I am suspecting that you are close to the yield stress. I do not know your rheometer, but when it is stress controlled it is better to measure these materials at constant stress. What may be happening is that you are close to the yield stress and you are breaking down and building up your networkstructure. When your rheometer is stress controlled it can not put directly a shear rate on your sample, but needs to do a guess. This guess may be over the yield stress, causing your sample structure to break down. My advice, when your rheometer is stress controlled, is to apply constant stress, in this way you can also measure the viscosity as a function of the shear rate, but the machine is better controlled.
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