Evidence of Universal Temperature Scaling in Self-Heated Percolating Networks

Abstract

During routine operation, electrically percolating nanocomposites are subjected to high voltages, leading to spatially heterogeneous current distribution. The heterogeneity implies localized self-heating that may (self-consistently) reroute the percolation pathways and even irreversibly damage the material. In the absence of experiments that can spatially resolve the current distribution and a nonlinear percolation model suitable to interpret them, one relies on empirical rules and safety factors to engineer these materials. In this paper, we use ultrahigh resolution thermo-reflectance imaging, coupled with a new imaging processing technique, to map the spatial distribution ΔT(x, y; I) and histogram f(ΔT) of temperature rise due to self-heating in two types of 2D networks (percolating and copercolating). Remarkably, we find that the self-heating can be described by a simple two-parameter Weibull distribution, even under voltages high enough to reconfigure the percolation pathways. Given the generality of the phenomenological argument supporting the distribution, other percolating networks are likely to show similar stress distribution in response to sufficiently large stimuli. Furthermore, the spatial evolution of the self-heating of network was investigated by analyzing the spatial distribution and spatial correlation, respectively. An estimation of degree of hotspot clustering reveals a mechanism analogous to crystallization physics. The results should encourage nonlinear generalization of percolation models necessary for predictive engineering of nanocomposite materials.

Electrical Mapping of Silver Nanowire Networks: A Versatile Tool for Imaging Network Homogeneity and Degradation Dynamics during Failure

“…This induces the presence of hotspots close to the percolation threshold that disappear progressively at higher network density. Also recently, thermoreflectance imaging has been successfully used to detect the presence of hotspots and study the local degradation mechanisms in either pristine AgNW networks, 16 hybrid graphene−AgNW networks, 17 or polymer assisted-templated Ag networks. 18 All these studies provided interesting information regarding current distribution in AgNW networks at the microscale.…”

Direct Imaging of the Onset of Electrical Conduction in Silver Nanowire Networks by Infrared Thermography: Evidence of Geometrical Quantized Percolation

“…LiT can be compared to the thermo-reflectance (TR) imaging technique, which has also recently proven efficient for detecting hot spots in percolating nanocomposites. 49 Here, we have also evaluated the effect of electrode geometry and the nanowire dimensions on the quantized percolation phenomenon. Finally, we demonstrate for the first time that the breakdown of the networks can also happen in a quantized manner.…”

“…In a more general way, such technique can be used to map the heat generated locally by Joule effect across the network to reveal how electric current is distributed through the percolating pathways. LiT can be compared to the thermo-reflectance (TR) imaging technique, which has also recently proven efficient for detecting hot spots in percolating nanocomposites . Here, we have also evaluated the effect of electrode geometry and the nanowire dimensions on the quantized percolation phenomenon.…”

Transparent Heaters: A Review

“…Das et al investigated scaling in self‐heated percolating networks and concluded that hotspot clustering appears to be a mechanism analogous to crystallization physics. [ 89 ] The potential presence of hotspots will be discussed in this review, since their presence can lead to TH instability. In brief, the thermal stability of the TH can be limited to the TH itself (e.g., degradation of the conductive polymer or morphological instability of silver nanowires [ 90 ] ) or to the substrate as well.…”