Nanotechnology News

news of the Center for Nanotechnology and Molecular Materials at Wake Forest University




PowerFelt (TM)















Organic thermoelectric materials based on heterogeneous conducting composites are well known.  Carbon nanotube composites can have a high electrical conductivity (10^5 S cm) but a thermal conductivity around 0.1 W/m^2K. This leads to Seebeck coeffs. ~ 100 microV/K or so.  But the Power Factors of such materials are typically poor.  To get more power from such materials, typically modules are produced: P(module) = n x P(leg) where n is the number of p-type and n-type legs in the TEG module.  But can this be done with heterogeneous materials?  The answer is yes! And the WFU team has demonstrated a novel “origami” style module together with a new  approach to the formation of n-type and p-type carriers in carbon nanotube composites. The result is flexible, and fabric-like, allowing for the formation of large scale coverings.  The advantage of such a footprint becomes clear when one realizes that most heat sources are finite sized objects from which maximum heat extraction and collection would involve a covering.  To see recent publications about these amazing materials see the references below:


Y.-M. Choi, D.-S. Lee, R. Czerw, N. Grobert, M. Terrones, M. Reyes-Reyes, H. Terrones, P.M. Ajayan,  D. L. Carroll, S. Roth, and Y.-W. Park, “Nonlinear behavior in the thermopower of doped carbon nanotubes due to strong localized states” Nanoletters, 3 (6) Jun (2003) 839 – 842.


Hewitt, C. A., Kaiser, A. B., Roth, S., Craps, M., Czerw, R., Carroll, D. L., Varying the concentration of single walled carbon nanotubes in thin film polymer composites, and its effect on thermoelectric power, APPLIED PHYSICS LETTERS  Volume: 98   Issue: 18   Article Number: 183110   DOI: 10.1063/1.3580761   Published: MAY 2 2011


Hewitt, Corey A.; Kaiser, Alan B.; Roth, Siegmar; Craps, Matt; Czerw, Richard; Carroll, David L. Multilayered Carbon Nanotube/Polymer Composite Based Thermoelectric Fabrics NANO LETTERS 1530-6984 MAR 2012 12 3 1307 1310 10.1021/nl203806q


C.A. Hewitt, D.L. Carroll, Extrinsic properties affecting the thermoelectric power output of few layer graphene/polyvinylidene fluoride composite thin films, Synthetic Metals 162 (2012) 2379– 2382.


C. A. Hewitt, A. B. Kaiser, M. Craps, R. Czerw, S. Roth, and D. L. Carroll, Temperature dependent thermoelectric properties of freestanding few layer graphene/polyvinylidene fluoride composite thin films, Synthetic Metals 165, 56-59 (2013) **cover article for SM vol 165


C. A. Hewitt, A. B. Kaiser, M. Craps, R. Czerw, and D. L. Carroll, Negative thermoelectric power from large diameter multiwalled carbon nanotubes grown at high chemical vapor deposition temperatures, Journal of Applied Physics 114, 083701 (2013)


C. A. Hewitt and D. L. Carroll, The effects of acid treatment on the thermoelectric power of multiwalled carbon nanotubes synthesized by chemical vapor deposition, Chemical Physics Letters 580, 67-72 (2013)


C. A. Hewitt, M. Craps, R. Czerw, and D. L. Carroll, The effects of high energy probe sonication on the thermoelectric power of large diameter multiwalled carbon nanotubes synthesized by chemical vapor deposition, Synthetic Metals 184, 68-72 (2013) **cover article for SM vol 184


C. A. Hewitt, D. L. Carroll, Temperature dependent thermoelectric properties of single and multi- walled carbon nanotube based polymer composites, Journal of Nano Energy and Power Research, in review 2013


C. A. Hewitt, David S. Montgomery, Ryan Barbalace, Rowland Carlson, and David L. Carroll, Improved Thermoelectric Power Output from Multilayered Polyethylenimine Doped Carbon Nanotube Based Organic Composites, submitted 2013


C. A. Hewitt and D. L. Carroll, Temperature dependent thermoelectric properties of polyethylenimine doped single walled carbon nanotube based polymer composites, submitted 2013



FIPEL (TM)






 

The Field Induced Polymer Electroluminescent Lamp (FIPEL) is a light emitting device unlike any other lamp used in room lighting.  The light is generated within an active conjugated polymer emitter by an applied AC field. So the current that the lamp uses is actually a polarization current and the internal quantum efficiency of the device is how well such a current is converted into excitons and then how well those excitons decay into photons. The amazing thing about these plastic lamps is that they can be really bright - over 10,000 Cd/m^2, any CIE coordinate desired, and very efficient (not yet published). To learn more about what we have already published see:


Y Chen, Y Xia, GM Smith, Y Gu, C Yang, DL Carroll Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices, , Applied Physics Letters 102 (1), 013307-013307-4


Yonghua Chen, Gregory M. Smith, Eamon Loughman, Yuan Li, Wanyi Nie, David L. Carroll, Effect of multi-walled carbon nanotubes on electron injection and charge generation in AC field-induced polymer electroluminescence, Organic Electronics, Volume 14, Issue 1, January 2013, Pages 8–18








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