Anisotropic thermal properties of nanochanneled alumina templates

Abstract

A composite photothermal technique for the measurement of thermal properties of solids J. Appl. Phys.Anodic porous alumina templates contain highly ordered nanochannels that are frequently used for fabrication of thermoelectric nanowires. Thermal properties of the templates are of high interest in thermoelectric device applications. This paper reports the temperature-dependent, anisotropic thermal conductivity and thermal diffusivity of 55 µm thick anodic template Anodisc from Whatman, Inc. of 0.02 µm pore diameter and ϳ30% porosity. The 3 technique was employed to carry out measurements of the effective thermal conductivity and thermal diffusivity in the direction parallel to the nanochannels axis, while thermal anisotropy of the sample was estimated theoretically using the Maxwell model. Measured effective thermal conductivity is between 0.54 W/mK at 80 K and 1.3 W/mK at 300 K. Measured thermal diffusivity decreases from 2.1ϫ 10 −6 m 2 s −1 at 80 K to 1.08ϫ 10 −6 m 2 s −1 at 300 K. A photothermoelectric technique was employed to measure independently the components of the thermal diffusivity along the direction parallel to the nanochannels axis and in the plane perpendicular to this direction. Reasonable agreements were found between the results provided by the two characterization techniques.

Enhanced in-plane thermoelectric figure of merit in p-type SiGe thin films by nanograin boundaries

“…By changing the input heating power, a series of T and U were obtained and the Seebeck coefficient of the film was then fitted according to S-S m = -U/T, where S m is the Seebeck coefficient of the metal (Cu) electrodes. The thermal conductivities of SiGe films were measured using the two-wire differential 3ω method [14][15][16][17][18] . Two Pt line heaters with linewidths of 2 m and 20 m respectively were deposited on the sample but electrically insulated from the film by a 50-nm Al 2 O 3 layer deposited with atomic layer deposition (ALD).…”

Highly Ordered Anodic Porous Alumina Formation by Self‐Organized Anodizing

“…The thermal characteristics of highly ordered porous alumina structures formed on aluminum have been studied widely [299][300][301][302][303][304][305][306], with thermal analyses being performed in order to collect data on chemical resistance [299,300], structural and optical properties [292,[300][301][302][303], thermal conductivity and diffusivity along the channel axis [304], self-repair rearrangement of ordered nanopore arrays induced by long-term heat treatment [305], and mechanical properties [306]. The fracture mechanism, Youngs modulus, hardness, fracture toughness [306] and fracture behavior in cylindrical ordered porous alumina [307] were also investigated.…”

Thermal diffusivity of nonfractal and fractal nickel nanowires

“…The thermal diffusivity of NCA20 templates was found to be 1 ϫ 10 −6 m 2 s −1 at 300 K, which is the same value reported by Borca-Tasciuc and Chen, measured by photothermoelectric technique. 17 To avoid error in the thickness measurements, squared as in Eq. ͑2͒, the sample thicknesses were measured from the cross sections by using scanning electron micrograph.…”