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Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

Zheng R, Gao J, Wang J, Chen G - Nat Commun (2011)

Bottom Line: Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature.With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C.The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.

ABSTRACT
Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

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The electrical conductivity of three other suspensions.(a) 1% graphite/water suspension. The electrical conductivity decreases about 24 times from −0.5 to 0.5 °C. (b) 1% carbon nanotube/hexadecane suspension. The electrical conductivity decreases about 40 times from 17.5 to 18.5 °C. (c) 0.4% graphite/polyethylene glycol 400 suspension. Polyethylene glycol 400 (Alfa Aesar) has a melting point between 4 and 8 °C and does not form a crystalline solid. Consequently, no large variation in the electrical resistivity was observed.
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f4: The electrical conductivity of three other suspensions.(a) 1% graphite/water suspension. The electrical conductivity decreases about 24 times from −0.5 to 0.5 °C. (b) 1% carbon nanotube/hexadecane suspension. The electrical conductivity decreases about 40 times from 17.5 to 18.5 °C. (c) 0.4% graphite/polyethylene glycol 400 suspension. Polyethylene glycol 400 (Alfa Aesar) has a melting point between 4 and 8 °C and does not form a crystalline solid. Consequently, no large variation in the electrical resistivity was observed.

Mentions: The strategy demonstrated with a graphite-hexadecane suspension is general. Both the fluids and the particulates can be changed to optimize for specific applications. The base fluid should be a material that is crystalline in the solid state. The particulates could be any material with high electrical and/or thermal conductivity that can form a stable suspension when the host material is in the liquid state. Figure 4a,b shows similar behaviour in the temperature-dependent electrical conductivity variation of graphite/water suspensions and carbon nanotube/hexadecane suspensions. Figure 4c presents experimental results on a non-crystalline-forming suspension, made from polyethylene glycol 400 and graphite flakes, which shows no sharp change in the electrical conductivity during phase transition, further confirming the importance of a crystalline forming liquid host.


Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

Zheng R, Gao J, Wang J, Chen G - Nat Commun (2011)

The electrical conductivity of three other suspensions.(a) 1% graphite/water suspension. The electrical conductivity decreases about 24 times from −0.5 to 0.5 °C. (b) 1% carbon nanotube/hexadecane suspension. The electrical conductivity decreases about 40 times from 17.5 to 18.5 °C. (c) 0.4% graphite/polyethylene glycol 400 suspension. Polyethylene glycol 400 (Alfa Aesar) has a melting point between 4 and 8 °C and does not form a crystalline solid. Consequently, no large variation in the electrical resistivity was observed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104514&req=5

f4: The electrical conductivity of three other suspensions.(a) 1% graphite/water suspension. The electrical conductivity decreases about 24 times from −0.5 to 0.5 °C. (b) 1% carbon nanotube/hexadecane suspension. The electrical conductivity decreases about 40 times from 17.5 to 18.5 °C. (c) 0.4% graphite/polyethylene glycol 400 suspension. Polyethylene glycol 400 (Alfa Aesar) has a melting point between 4 and 8 °C and does not form a crystalline solid. Consequently, no large variation in the electrical resistivity was observed.
Mentions: The strategy demonstrated with a graphite-hexadecane suspension is general. Both the fluids and the particulates can be changed to optimize for specific applications. The base fluid should be a material that is crystalline in the solid state. The particulates could be any material with high electrical and/or thermal conductivity that can form a stable suspension when the host material is in the liquid state. Figure 4a,b shows similar behaviour in the temperature-dependent electrical conductivity variation of graphite/water suspensions and carbon nanotube/hexadecane suspensions. Figure 4c presents experimental results on a non-crystalline-forming suspension, made from polyethylene glycol 400 and graphite flakes, which shows no sharp change in the electrical conductivity during phase transition, further confirming the importance of a crystalline forming liquid host.

Bottom Line: Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature.With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C.The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.

ABSTRACT
Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

Show MeSH