Dynamic viscosity measurement in non-Newtonian graphite nanofluids.
Fei Duan1, Ting Foong Wong, Alexandru Crivoi
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798, Singapore. feiduan@ntu.edu.sg.
Nanoscale Research Letters
|July 4, 2012
Summary
Graphite nanoparticle aggregation in water-based nanofluids increases dynamic viscosity. Higher concentrations and longer holding times enhance this effect, with significant viscosity boosts observed due to particle clumping.
Area of Science:
- Materials Science
- Fluid Dynamics
- Nanotechnology
Background:
- Nanofluids, suspensions of nanoparticles in base fluids, offer enhanced thermal and physical properties.
- Understanding the rheological behavior of nanofluids is crucial for their application in various engineering fields.
- Graphite-based nanofluids are of interest due to graphite's unique properties.
Purpose of the Study:
- To investigate the dynamic viscosity of graphite water-based nanofluids.
- To analyze the influence of particle concentration and holding time on viscosity.
- To correlate rheological properties with nanoparticle aggregation and structural changes.
Main Methods:
- Measurement of effective dynamic viscosity under shear.
- Determination of viscosity at zero and infinite shear rates.
- Transmission electron microscopy (TEM) for nanoparticle morphology analysis.
- Raman spectroscopy to characterize graphite structure (D and G peaks).
Main Results:
- Shear-thinning non-Newtonian behavior was observed.
- Effective dynamic viscosity increased with higher particle volume concentration and longer holding times.
- Maximum viscosity enhancement exceeded 24 times at 4% concentration after 3 days.
- TEM revealed significant, irregular nanoparticle aggregation in aged nanofluids.
- Raman spectra indicated increasing nanoparticle aggregation with concentration and time.
Conclusions:
- The enhanced dynamic viscosity of graphite nanofluids is directly linked to graphite nanoparticle aggregation.
- Particle concentration and fluid holding time are critical factors influencing aggregation and rheology.
- These findings provide insights into the stability and flow behavior of graphite nanofluids.
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