2020
DOI: 10.1021/acs.analchem.9b03216
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High Field MicroMRI Velocimetric Measurement of Quantitative Local Flow Curves

Abstract: Performing rheo-microMRI velocimetry at a high magnetic field with strong pulsed field gradients has clear advantages in terms of (chemical) sensitivity and resolution in velocities, time, and space. To benefit from these advantages, some artifacts need to be minimized. Significant sources of such artifacts are chemical shift dispersion due to the high magnetic field, eddy currents caused by the pulsed magnetic field gradients, and possible mechanical instabilities in concentric cylinder (CC) rheo-cells. These… Show more

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Cited by 9 publications
(20 citation statements)
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“…The SNR obtained in the 500-μm-gap CC is 120 ± 5, as given by the ratio of mean signal intensity to the standard deviation of the noise, which is comparable with that of wider gap geometries. [15,30] Here, modeling the confined flow behavior of the FCD would have required accounting for the observed microstructural rearrangements and temperature effects, which was beyond the scope of this work.…”
Section: Case Study: Local Flow Behavior Of a Fcdmentioning
confidence: 99%
See 1 more Smart Citation
“…The SNR obtained in the 500-μm-gap CC is 120 ± 5, as given by the ratio of mean signal intensity to the standard deviation of the noise, which is comparable with that of wider gap geometries. [15,30] Here, modeling the confined flow behavior of the FCD would have required accounting for the observed microstructural rearrangements and temperature effects, which was beyond the scope of this work.…”
Section: Case Study: Local Flow Behavior Of a Fcdmentioning
confidence: 99%
“…Such wobbling limits the achievable spatial resolution typically to only about 50 μm, not sufficient for submillimeter geometries, and causes unstable shear flow as well as a fluctuating gap size during shear. [15] F I G U R E 1 Schematic representation of a complex fluid, with particles of average diameter l, being sheared in a Couette cell (CC) made of polyether ether ketone (PEEK) (dark gray) with gap size d. (a) Top view of the CC; cup filled with the complex fluid (light gray) and bob filled with a reference fluid (white). (b) Zoom-in of a gap-filling fluid exhibiting cooperative flow: when d ≤ 100 Á l, plastic rearrangements (empty black circles) of particles can cause stress modulations throughout the gap (red arrows) resulting in additional correlated plastic rearrangements at neighboring sites (dashed black circles) Due to both its inherent complex phenomenology and the lack of versatile submillimeter flow setups, cooperativity is still poorly understood at the fundamental level and not yet quantified with a unique model.…”
Section: Introductionmentioning
confidence: 99%
“…The overlap of such curves (see Figure 4) then proves the consistency of the constitutive equation obtained in this way, as this indeed means that a single local rheological behavior is obtained for a given shear stress. Local rheometry by MR velocimetry made it possible to determine the effective rheological behavior of Newtonian fluids (Nikolaeva et al 2020), simple yield stress fluids such as Carbopol gels (Coussot et al 2009, Nikolaeva et al 2020) and emulsions (Ovarlez et al 2008). In that case, the consistency of these data with the flow curve determined from standard rheometry could also be checked (see Figure 4).…”
Section: "Local Rheometry"mentioning
confidence: 99%
“…To go deeper into the analysis of the time-dependent behavior of EY and MEY emulsions, conventional rheology measurements are combined with localized 1D flow profiles recorded using rheo-MRI. This technique has been extensively applied in the study of structure formation and degradation of complex systems, as well as in the investigation of transient flow in Newtonian and non-Newtonian fluids [ 16 , 23 , 24 , 25 ]. By combining rheology stress ( ) measurements with shear rate (r) profiles calculated from rheo-MRI velocity data, with being the position along the cell gap, a local flow curve (LFC) can be constructed as a function of time during shear treatment.…”
Section: Resultsmentioning
confidence: 99%
“…In order to obtain in situ local flow curves, we combined the results from conventional rheology with those from localized flow measurements performed by rheo-MRI. This approach was successfully validated for the quantitative assessment of time-dependent yield stress behavior in complex systems, such as micronized fat crystals dispersions undergoing structural degradation [ 16 ]. The results shown in the present work indicate that EY and MEY emulsion formulations exhibit a decay of the apparent viscosity under constant shear, caused by an irreversible decrease of the emulsion’s yield stress value.…”
Section: Introductionmentioning
confidence: 99%