Experimental Study of Heat Conduction in Aqueous Suspensions of Aluminum Oxide Nanoparticles

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
Y. Sungtaek Ju ◽  
Jichul Kim ◽  
Ming-Tsung Hung
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Average Particle Size ◽  
Oxide Nanoparticles ◽  
Average Particle ◽  
Aluminum Oxide Nanoparticles ◽  
Aqueous Suspensions ◽  
Effective Medium Model ◽  
Transient Hot Wire Technique ◽  
Different Temperatures

We report measurements of the thermal conductivity of aqueous suspensions of aluminum oxide nanoparticles with nominal diameters of 20nm, 30nm, and 45nm and at volume concentrations up to 10%. Potential complications in the pulsed transient hot-wire technique for characterizing nanofluids are examined, which motivate the development of a microhot strip setup with a small thermal time constant. The average particle size is monitored for samples subjected to different durations of sonication and the thermal conductivity is determined at two different temperatures for each of the samples. The present data do not reveal any anomalous enhancement in the thermal conductivity previously reported for comparable nanofluids. The concentration dependence of the thermal conductivity can be explained using the conventional effective medium model with a physically reasonable set of parameters.

Experimental Study of Heat Conduction in Aqueous Suspensions of Aluminum Oxide Nanoparticles

2007 ◽  
Author(s):  
Y. Sungtaek Ju ◽  
Jichul Kim ◽  
Ming-Tsung Hung
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Particle Size ◽  
Heat Conduction ◽  
Aluminum Oxide ◽  
Oxide Nanoparticles ◽  
Average Particle ◽  
Temperature Inhomogeneity ◽  
Aluminum Oxide Nanoparticles ◽  
Aqueous Suspensions

We perform a systematic experimental study of heat conduction in aqueous suspensions of aluminum oxide nanoparticles at volume concentrations up to 10%. We develop a micro-hotwire device to reduce experimental errors resulting from spatial or temporal temperature inhomogeneity within a sample. The volume concentration dependence of the thermal conductivity can be explained using the effective medium model with a physically reasonable set of parameters. The average particle size as well as the thermal conductivity is measured as a function of sample sonication time and temperature. The size of particles/aggregates in our nanofluid samples is much greater than the nominal particle size reported by the manufacturers and does not change appreciably with sonication for up to 24 hours. Our data do not reveal any anomalous enhancement in the thermal conductivity or strong temperature dependence reported in other previous studies. The discrepancy may reflect subtle differences in nanopowders or nanofluid preparation procedures that result in drastic difference in the size or shape of suspended particles/aggregates.

Experimental Investigation of Temperature Dependent Thermal Conductivity of Aluminum Oxide and CNT Heat Transfer Fluids

2016 ◽  
Author(s):  
David Calamas ◽  
John Willis ◽  
Zachary Wilkes ◽  
Mosfequr Rahman ◽  
Daniel Dannelley
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Base Fluid ◽  
Experimental Methodology ◽  
Oxide Nanoparticles ◽  
Outer Diameter ◽  
Aluminum Oxide Nanoparticles ◽  
Heat Transfer Fluids ◽  
Multi Walled Carbon Nanotubes

Nanofluids often exhibit superior heat transfer characteristics when compared with conventional heat transfer fluids. The increase in thermal conductivity due to the presence of various nanoparticles was experimentally examined using commercially available equipment that utilizes the two thickness method. The thermal conductivity of 10 and 30 nm aluminum oxide nanoparticles suspended in distilled water at concentrations of 2% and 5% was measured for a temperature range of 15°C to 70°C in increments of 5°C. For a 2% concentration of 10 nm aluminum oxide the experimentally derived thermal conductivity deviated from the theoretical thermal conductivity predicted by Maxwell by an average of 1.55%. The average percent increase in the thermal conductivity of the base fluid due to the presence of 10 nm aluminum oxide nanoparticles was found to be 4.17 and 4.90% for concentrations of 2 and 5% respectively. The presence of 30 nm nanoparticles resulted in a greater discrepancy with the theoretical model developed by Maxwell, regardless of concentration. In addition, the presence of 10 nm aluminum oxide nanoparticles resulted in a greater increase in thermal conductivity when compared with 30 nm aluminum oxide nanoparticles. In addition, the thermal conductivity of a base fluid dispersed with multi-walled carbon nanotubes (MWNTs) with an outer diameter ranging from 13–18 nm and a length ranging from 3–30 micrometers (μm) was examined. The presence of a 0.2% concentration of MWNTs resulted in an average increase in thermal conductivity of 0.31%. Unfortunately, there was a large standard deviation in the results for the MWNTs and significant fluctuations with temperature. While this experimental methodology may be sufficient for metal based nanofluid particles it may be undesirable for fluids enhanced by MWNTs.

scholarly journals Influence of Cu on the Improvement of Magnetic Properties and Structure of L10 FePt Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1097
Author(s):  
Luran Zhang ◽  
Xinchen Du ◽  
Hongjie Lu ◽  
Dandan Gao ◽  
Huan Liu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Annealing Temperature ◽  
Reduction Method ◽  
Solid Phase ◽  
Average Particle Size ◽  
Fept Nanoparticles ◽  
Average Particle ◽  
Phase Reduction ◽  
Different Temperatures ◽  
One Step

L10 ordered FePt and FePtCu nanoparticles (NPs) with a good dispersion were successfully fabricated by a simple, green, one-step solid-phase reduction method. Fe (acac)3, Pt (acac)2, and CuO as the precursors were dispersed in NaCl and annealed at different temperatures with an H2-containing atmosphere. As the annealing temperature increased, the chemical order parameter (S), average particle size (D), coercivity (Hc), and saturation magnetization (Ms) of FePt and FePtCu NPs increased and the size distribution range of the particles became wider. The ordered degree, D, Hc, and Ms of FePt NPs were greatly improved by adding 5% Cu. The highest S, D, Hc, and Ms were obtained when FePtCu NPs annealed at 750 °C, which were 0.91, 4.87 nm, 12,200 Oe, and 23.38 emu/g, respectively. The structure and magnetic properties of FePt and FePtCu NPs at different annealing temperatures were investigated and the formation mechanism of FePt and FePtCu NPs were discussed in detail.

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