Application of the thermal flash technique for low thermal diffusivity micro/nanofibers

Abstract

The thermal flash method was developed to characterize the thermal diffusivity of micro/nanofibers without concern for thermal contact resistance, which is commonly a barrier to accurate thermal measurement of these materials. Within a scanning electron microscope, a micromanipulator supplies instantaneous heating to the micro/nanofiber, and the resulting transient thermal response is detected at a microfabricated silicon sensor. These data are used to determine thermal diffusivity. Glass fibers of diameter 15 microm had a measured diffusivity of 1.21x10(-7) m(2)/s; polyimide fibers of diameters 570 and 271 nm exhibited diffusivities of 5.97x10(-8) and 6.28x10(-8) m(2)/s, respectively, which compare favorably with bulk values.

Thermal Transport Measurement Techniques for Nanowires and Nanotubes

“…In comparison, it is feasible to determine the heating in the cantilever rather conveniently and accurately if the heating is provided by electrical heating of a doped Si or Pt-C resistor fabricated at the end of a cantilever. 49,50 This type of resistance thermometer can achieve 3 mK temperature sensitivity with the use of lock-in detection combined with a Wheatstone bridge. The resistance of the thermometer can also be calibrated readily as a function of the cantilever temperature, and the method is free of the complication caused by thermal drifting of the laser beam as well as cantilever deflection caused by mechanical strain applied by the nanofiber.…”

“…Resistance thermometer cantilever sensors have been explored for thermal diffusivity measurements of polymer fibers by Demko et al 49 The thermal sensor is a Si cantilever with two heavily doped beams connected by a lightly doped Si region that acts as the resistance thermometer (see Fig. 11).…”

“…In addition, because the lightly doped resistance thermometer sensor has a finite size, l RT , the thermal time constant of the sensor needs to be considerably smaller than that of the fiber, that is, l 2 RT /α s 2 f /α f , in order to establish sufficient transient response of the sensor. In the work of Demko et al, 49 the samples were glass fibers and polyimide fibers with considerably lower thermal diffusivity than the Si sensor. For extending this method to a high-thermal diffusivity carbon nanotube of a finite length, the size of the resistance thermometer may need to be reduced to be considerably smaller than the length of the nanotube sample.…”

The thermal flash technique: The inconsequential effect of contact resistance and the characterization of carbon nanotube clusters

“…This article focuses on the mathematical formalism behind a technique developed on the thermal flash principle 12,13 to facilitate direct characterization of the true conductivity of the material without being influenced by the presence of interfacial or contact resistances. While the thermal flash method has been presented previously by the authors as a technique employed to measure thermal diffusivity/conductivity at the nanoscale, 13 this is the first attempt at substantiation that no a) Author to whom correspondence should be addressed.…”

Note: Thermal conductivity measurement of individual poly(ether ketone)/carbon nanotube fibers using a steady-state dc thermal bridge method

“…The reliability and accuracy of this method were, to a large extent, limited by the thermal contact resistance between the sample and the hot wire and the uncertainty related to the geometry. Inspired by the laser flash method, Demko et al 5 proposed a thermal flash method that utilized a micromanipulator to supply heat and a microfabricated sensor to determine the temperature response. This approach, however, was only suitable for fibers with low thermal diffusivity.…”