Simulation study of the electrical tunneling network conductivity of suspensions of hard spherocylinders

Atashpendar, Arshia; Arora, Sarthak; Rahm, Alexander; Schilling, Tanja

doi:10.1103/physreve.98.062611

Cited by 5 publications

(4 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For electrical percolation in polymeric nanocomposites, λ is equivalent to an effective tunneling distance of charge carriers through the host medium. [13,14,24,33,34] If the solution is aqueous and charge-stabilized, then the charge carriers are mobile ions, and λ must arguably correspond to the Debye length. [20,35] It is important to note that the connectivity range, λ, is a material property determined by both the nanofiller and the host fluid, and is in principle controllable.…”

Section: Theoretical Modelmentioning

confidence: 99%

Unusual geometric percolation of hard nanorods in the uniaxial nematic liquid crystalline phase

et al. 2019

Self Cite

View full text Add to dashboard Cite

We investigate by means of continuum percolation theory and Monte Carlo simulations how spontaneous uniaxial symmetry breaking affects geometric percolation in dispersions of hard rodlike particles. If the particle aspect ratio exceeds about twenty, percolation in the nematic phase can be lost upon adding particles to the dispersion. This contrasts with percolation in the isotropic phase, where a minimum particle loading is always required to obtain system-spanning clusters. For sufficiently short rods, percolation in the uniaxial nematic mimics that of the isotropic phase, where the addition of particles always aids percolation. For aspect ratios between twenty and infinity, but not including infinity, we find re-entrance behavior: percolation in the low-density nematic may be lost upon increasing the amount of nanofillers but can be re-gained by the addition of even more particles to the suspension. Our simulation results for aspect ratios of 5, 10, 20, 50 and 100 strongly support our theoretical predictions, with almost quantitative agreement. We show that a new closure of the connectedness Ornstein-Zernike equation, inspired by Scaled Particle Theory, is more accurate than the Lee-Parsons closure that effectively describes the impact of many-body direct contacts.

show abstract

Section: Theoretical Modelmentioning

confidence: 99%

Unusual geometric percolation of hard nanorods in the uniaxial nematic liquid crystalline phase

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…For sufficiently small connectivity ranges, the percolation transition can even be pre-empted by the isotropic-nematic phase transition. [43,44] Next to their liquid-crystalline behaviour, anisometric particles may get aligned during the processing of the nanocomposite in its liquid state. Depending on the application, alignment may actually be desired and intentionally induced.…”

Section: Introductionmentioning

confidence: 99%

“…Applying electric or magnetic fields, [45][46][47][48][49][50][51][52][53] or using a thermotropic liquid-crystalline host medium, [54][55][56][57] for instance, can result in (tunable) anisotropic mechanical or transport properties of the nanocomposite. [44,[58][59][60][61] Anisometric filler particles may also align due to flow fields, [61][62][63][64][65] which arise during processing steps like extrusion, drawing, spin coating or slot die coating. If the liquid is not allowed to relax before solidification, the aligned structure is then frozen in in the final composite.…”

Section: Introductionmentioning

confidence: 99%

Geometric percolation of hard nanorods: The interplay of spontaneous and externally induced uniaxial particle alignment

2020

View full text Add to dashboard Cite

We present a numerical study on geometric percolation in liquid dispersions of hard slender colloidal particles subjected to an external orienting field. In the formulation and liquid-state processing of nanocomposite materials, the alignment of particles by external fields such as electric, magnetic or flow fields is practically inevitable, and often works against the emergence of large nanoparticle networks. Using continuum percolation theory in conjunction with Onsager theory, we investigate how the interplay between externally induced alignment and the spontaneous symmetry breaking of the uniaxial nematic phase affects cluster formation within nanoparticle dispersions. It is known that the enhancement of particle alignment by means of a density increase or an external field may result in the breakdown of an already percolating network. As a result, percolation can be limited to a small region of the phase diagram only. Here, we demonstrate that the existence and shape of such a "percolation island" in the phase diagram crucially depends on the connectivity length -a critical distance defining direct connections between neighbouring particles. Deformations of this percolation island can lead to peculiar re-entrance effects, in which a system-spanning network forms and breaks down multiple times with increasing particle density. arXiv:1910.00621v1 [cond-mat.soft]

show abstract

“…Another important aspect of anisotropic fillers such as * arshia.atashpendar@physik.uni-freiburg.de rods or platelets is their ability to intrinsically form liquid crystalline phases: upon increasing the concentration of the particles, they undergo a first order transition from an isotropic (I) to a nematic (N) phase [18,19] where the particles become orientationally ordered. For rodlike particles, the effect of the so-induced alignment on the tunneling conductivity has been previously studied in simulations [20], using theoretical percolation-based approaches in [21,22] for various degrees of orientational order, and more extensively in cases of externally induced alignment in [23][24][25][26][27]. However for platelets, the percolation and conductivity behaviour across the intrinsic liquid-crystalline phases has remained largely unexplored.…”

mentioning

confidence: 99%

Shape, connectedness percolation and electrical conductivity of clusters in suspensions of hard platelets

Atashpendar,

Ingenbrand,

Schilling

2020

Preprint

Self Cite

View full text Add to dashboard Cite

Using Monte Carlo simulations, we investigate how geometric percolation and electrical conductivity in suspensions of hard conducting platelets are affected by the addition of platelets and their degree of spontaneous alignment. In our simulation results for aspect ratios 10, 25 and 50, we consistently observe a monotonically decreasing percolation threshold as a function of volume fraction, i.e., the addition of particles always aids percolation. In the nematic phase, the distribution of particles inside the percolating clusters becomes less spherically symmetric and the aspect ratio of the clusters increases. However, the clusters are also anisotropically shaped in the isotropic phase, although their aspect ratio remains constant as a function of volume fraction and is only weakly dependent on the particle aspect ratio. Mapping the percolating clusters of platelets to linear resistor networks, and assigning unit conductance to all connections, we find a constant conductivity both across the isotropic-nematic transition and in the respective stable phases. This behaviour is consistent with the other observed topological properties of the networks, namely, the average path length, average number of contacts per particle and the Kirchhoff index which all remain constant and unaffected by both the addition of particles and the degree of alignment of their suspension. On the contrary, using an anisotropic conductance model that explicitly accounts for the relative orientation of the particles, the network conductivity decreases with increasing volume fraction in the isotropic, and further diminishes at the onset of the nematic while preserving the same trend deep in the nematic. Hence, our observations consistently suggest that unlike for rod-like fillers, the network structures that arise from platelet suspensions are neither very sensitive to the particle aspect ratio nor to alignment. Hence platelets are not as versatile as fillers for dispersion in conductive composite materials as rods.

show abstract

Simulation study of the electrical tunneling network conductivity of suspensions of hard spherocylinders

Cited by 5 publications

References 66 publications

Unusual geometric percolation of hard nanorods in the uniaxial nematic liquid crystalline phase

Unusual geometric percolation of hard nanorods in the uniaxial nematic liquid crystalline phase

Geometric percolation of hard nanorods: The interplay of spontaneous and externally induced uniaxial particle alignment

Shape, connectedness percolation and electrical conductivity of clusters in suspensions of hard platelets

Contact Info

Product

Resources

About