Thermoelectric characterization of nickel-nanowires and nanoparticles embedded in silica aerogels

Sherko Ghaderi,Jiabin Wang,Xiao Han,Khalil T Hassan,Sarah H Olsen,Lidija Šiller

doi:10.1063/1.5027889

Abstract

Embedded nickel nanowires (NiNWs) and nickel nanoparticles (NiNPs) in silica aerogels at three different concentrations are characterized by scanning thermal microscopy, a Hot disk method and four probe measurements to consider them as potential thermoelectric materials. NiNW samples exhibit 9 orders of magnitude improvement in thermoelectric figure of merit while the embedded NiNPs samples show a 6 orders of magnitude improvement when the concentrations are increased from 0 to 700 ppm. The electrical resistivity is highly sensitive to the concentration of NiNWs and NiNPs in the silica aerogels, while the thermal conductivity remains largely unchanged over temperature range 300 to 420 K. The electrical conductivity σ follows a percolation scaling law of the form σ ∝ (W − Wc)t with critical weight fraction (Wc) to form a conductive network at range 0.04-0.06 Wt% and 0.08-0.1 Wt% for embedded NiNWs and NiNPs, respectively. The investigation suggest that further optimization of the concentration of nanomaterials in aerogels could yield promising thermoelectric properties.

Highlights

The challenge in creating high-performance thermoelectric materials lies in simultaneously achieving a high electrical conductivity, high Seebeck coefficients, and a low thermal conductivity
The thermoelectric properties of silica aerogels with different concentrations of nickel nanoparticles (NiNPs) and nickel nanowires (NiNWs) were examined
Very low lattice thermal conductivity was achieved which appeared relatively insensitive to NiNP and NiNW concentration

Summary

INTRODUCTION

The challenge in creating high-performance thermoelectric materials lies in simultaneously achieving a high electrical conductivity, high Seebeck coefficients, and a low thermal conductivity. These parameters are temperature dependent and are closely associated in such a way that by enhancing one parameter the other parameter changes and most often deteriorates.[1]. This paper describes the characterization of nickel nanowires (NiNWs) and nickel nanoparticles (NiNPs) embedded in silica aerogels at various temperatures with the aim of evaluating key thermoelectric properties. The work shows that by optimizing the concentration of NiNWs or NiNPs, a silica aerogel composite may be potentially considered as a valuable thermoelectric material

Experimental details

Electrical resistivity measurement

Thermal conductivity measurement

CONCLUSION