Geometry of the shear flow with an optical micrograph of a sheared semidilute suspension that shows typical MWNT shape.
Diffuse nanotube clusters formed under weak shear in PIB, where the scale bar is .
Steady shear viscosity as a function of time for controlled strain cone-and-plate measurements at a shear rate of and three different nanotube concentrations.
Shear stress as a function of shear rate for controlled strain cone-and-plate measurements at different nanotube loadings; , , , , , , and by mass, from bottom to top.
(a) Shear viscosity of the MWNT suspensions as a function of and , and (b) linear viscoelastic response as a function of and , where the solid and dashed curves are storage and loss moduli, respectively. Measurements are controlled-strain in a cone-and-plate geometry.
Scaled linear viscoelastic response as a function of reduced frequency.
Scaled shear stress as a function of dimensionless shear rate deduced from the data in Fig. 4.
Composition dependence of the viscoelastic shear modulus, , as a function of , where the black makers are those used to reduce the storage modulus and the gray markers are those used to reduce the loss modulus. Error bars correspond to two standard deviations in total experimental uncertainty and are the size of the markers. The black line is a power law fit as described in the text. Also shown are the two separate measures of yield stress ( from controlled-strain and from controlled-stress) with a power law fit shown as a dashed line.
(a) as a function of for MWNT. (b) Strain hardening at MWNT in response to a slow square-wave stress of amplitude 1.5 Pa in a cone-and-plate geometry, where denotes the initial displacement. (c) Response of a MWNT suspension to a slow square-wave stress of amplitude 10 Pa in a parallel-plate geometry with a 1 mm gap.
Scaled “network” shear viscosity as a function of reduced shear rate.
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