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Thermal Transport Properties in Metal Nanowires (Application for Thermoelectric Power generation)

Due to increase of world demand and decrease of natural fuel supply, there will be a problem to supply sustainable energy in 21st century. So there is need to think some different way to generate energy.

Thermo electric (TE) phenomena are the conversion of heat energy to electricity and also it heats or cools the materials depending upon how you can use/make them for application. This heat energy to electricity could be the essential method to use the waste heat to convert to usable energy. Thermoelectric materials can be characterized by dimensionless thermoelectric figure of merits (ZT):

ZT = S2σT/κ

Where S, Seebeck coefficient, σ, electrical and κ, thermal conductivity.

To increase ZT one has to increase thermal power S2σ and decrease the thermal conductivity. In bulk materials (σ/κ) is constant according to Weidmann Franz low, means electrical conductivity of a materials increases with thermal conductivity. So it is difficult to control these two parameters independently. In low dimensional materials such as nanowires, thermo power can be enhanced due to quantum confinement effect and thermal conductivity can be reduced more than the electrical conductivity because of internal reflection of phonon wave or scattering much more due to defect produced in nanostructure. Knowledge of nanowire thermal and thermoelectric properties is critical for the thermal management of nanowire devices and essential for the design of nanowire thermoelectric devices.

Cobalt is a magnetic material and Co nanowires (Co NWs) have distinctive magnetic properties and also displaying promising use in applications such as recording media, nanosensors and nanodevices. We studied thermal conductivity of Co NWs as a function of temperature on composite samples containing Co NWs from 300 to 400 K. Measurements of specific heat and thermal conductivity was studied over randomly oriented Co NWs and parallel to the long axis of Co NWs by AC Calorimetry method.

 

Thermoelectric Device

Thermoelectric p-n junction Module shows the direction

Of charge flow on both cooling and power generation

Fabrication of Co NWs

3D Cartoon of thermal measurement along the long axis

Thermal measurement along the nanowire along the long axis and on randomly oriented mat sample

Fabrication of MWCNTS

Thermal conductivity of SW/MW CNTs & graphites

 

 

Heat Transport Properties of Carbon Nanotubes for Heat removal and other High Thermal conductivity Application

Ever rising power densities and smaller transistor dimensions are increasing the challenge of thermal management within integrated-circuit chips and their surrounding packaging. Theoretical investigations have indicated that single-wall CNTs (SWCNT) have the highest thermal conductivity along the long axis of the nanotube, predicted to be as high as 6600 W/mK at room temperature; three times that of diamond. The experimentally measured thermal conductivity of an individual multi-wall CNT (MWCNT) is reasonably consistent and was found to be 3000 W/mK.

 

We measured the thermal conductivity of free standing MWCNTs arrays and also randomly oriented MWCNTs and SWCNTs mat sample. The effective thermal conductivity of the anisotropic MWCNTs increases smoothly with increasing temperature and is indicative of the one-dimensional nature of the heat flow. Whereas the effective thermal conductivity of randomly oriented MWCNTs and SWCNTs is similar to that of powder graphite, exhibiting a maximum value near 364 K indicating the onset of boundary phonon scattering.

 

Thermal Heat Transopr Properties of Carbon Nanotubes / Polymer Composites for High strength Light weight materials