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Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids.

White SB, Shih AJ, Pipe KP - Nanoscale Res Lett (2011)

Bottom Line: Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied.Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions.These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA. sbwhite@umich.edu.

ABSTRACT
Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids.

No MeSH data available.


Related in: MedlinePlus

Schematic of Kuwabara's cell model with particle radius, a, electrical double layer thickness, κ-1, and surrounding shell of liquid medium with outer radius b.
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Figure 1: Schematic of Kuwabara's cell model with particle radius, a, electrical double layer thickness, κ-1, and surrounding shell of liquid medium with outer radius b.

Mentions: Kuwabara's cell model [18], shown in Figure 1, is used to analyze the electrokinetic properties of colloidal suspensions. Each particle of radius, a, is surrounded by a virtual shell of the salt-free medium with of radius, b, such that the volume fraction, ϕ, equals (a/b)3. This model simplifies the electro-hydrodynamic interactions between the particles by representing an average particle and surrounding medium. This model does not account for overlapping EDLs and is commonly used to investigate the electrophoresis and sedimentation of colloidal suspensions of spherical particles. Based on this cell model, Ohshima [16] derived separate analytical expressions for the electrical conductivity K of a salt-free suspension that apply when the particle surface charge Q = 4πεrε0aζ is either less than or greater than a critical surface charge given by:(1)


Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids.

White SB, Shih AJ, Pipe KP - Nanoscale Res Lett (2011)

Schematic of Kuwabara's cell model with particle radius, a, electrical double layer thickness, κ-1, and surrounding shell of liquid medium with outer radius b.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211435&req=5

Figure 1: Schematic of Kuwabara's cell model with particle radius, a, electrical double layer thickness, κ-1, and surrounding shell of liquid medium with outer radius b.
Mentions: Kuwabara's cell model [18], shown in Figure 1, is used to analyze the electrokinetic properties of colloidal suspensions. Each particle of radius, a, is surrounded by a virtual shell of the salt-free medium with of radius, b, such that the volume fraction, ϕ, equals (a/b)3. This model simplifies the electro-hydrodynamic interactions between the particles by representing an average particle and surrounding medium. This model does not account for overlapping EDLs and is commonly used to investigate the electrophoresis and sedimentation of colloidal suspensions of spherical particles. Based on this cell model, Ohshima [16] derived separate analytical expressions for the electrical conductivity K of a salt-free suspension that apply when the particle surface charge Q = 4πεrε0aζ is either less than or greater than a critical surface charge given by:(1)

Bottom Line: Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied.Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions.These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA. sbwhite@umich.edu.

ABSTRACT
Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids.

No MeSH data available.


Related in: MedlinePlus