Showing papers on "Nanofluid published in 2001"

Anomalously increased effective thermal conductivities of ethylene glycol-based nanofluids containing copper nanoparticles

Abstract: It is shown that a “nanofluid” consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol % Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity.

Gas-Phase Synthesis of Single-wall Carbon Nanotubes from Colloidal Solution of Metal Nanoparticles

Abstract: Metal nanoparticles play an important role in chemical vapor deposition (CVD) synthesis of carbon nanotubes because nanoparticles not only catalyze the nanotube growth but also determine the structural characteristics of the nanotubes. We report on the synthesis of single-wall carbon nanotubes (SWNTs) on the basis of the gas-phase reaction of colloidal solutions of metal nanoparticles containing Co and Mo. The colloidal solution of the nanoparticles is prepared by a reverse micelle method and injected into a furnace, where the solvent serves as the carbon source while the nanoparticles act as the catalyst. We have found that addition of a small amount of thiophene leads to formation of the SWNTs. The formation mechanism of the SWNTs is discussed by comparing the present CVD and laser-ablation methods.

Nanofluids for Vehicle Thermal Management

Abstract: Applying nanotechnology to thermal engineering, ANL has addressed the interesting and timely topic of nanofluids. We have developed methods for producing both oxide and metal nanofluids, studied their thermal conductivity, and obtained promising results: (1) Stable suspensions of nanoparticles can be achieved. (2) Nanofluids have significantly higher thermal conductivities than their base liquids. (3) Measured thermal conductivities of nanofluids are much greater than predicted. For these reasons, nanofluids show promise for improving the design and performance of vehicle thermal management systems. However, critical barriers to further development and application of nanofluid technology are agglomeration of nanoparticles and oxidation of metallic nanoparticles. Therefore, methods to prevent particle agglomeration and degradation are required.

In-situ fluid experiments in carbon nanotubes

Abstract: Closed-end multi-wall carbon nanotubes, which contain an encapsulated aqueous multi-phase fluidunder high pressure, have been produced by hydrothermal synthesis. These nanotubes are leak-tight by virtue of holding the fluid at the high vacuum of a transmission electron microscope (TEM) and can be used as a testplatform for unique in-situ nanofluidic experiments in TEM. They form an experimental apparatus, which is at least two orders of magnitude smaller than the smallest capillaries used in fluidic experiments so far. Excellent wettability of the carbon tube walls by the liquid and a dynamic behavior similar to that in micro-capillaries demonstrates the possibility of use of nanoscale (<100 nm) tubes in nanofluidic devices.However, complex interface behavior that can potentially create hurdles to fluid transport is also demonstratedherein.