Search results for "Percolation"

Coarsened Lattice Model for Random Granular Systems

1998

In random systems consisting of grains with size distributions the transport properties are difficult to explore by network models. However, the concentration dependence of effective conductivity and its critical properties can be considered within coarsened lattice model proposed that takes into account information from experimentally known size histograms. For certain classes of size distributions the specific local arrangements of grains can induce either symmetrical or unsymmetrical critical behaviour at two threshold concentrations. Using histogram related parameters the non-monotonic behaviour of the conductor-insulator and conductor-superconductor threshold is demonstrated.

Anisotropic and non-heterogeneous continuum percolation in titanium oxynitride thin columnar films

2002

International audience; We report the percolation behaviour of the conductivity of titanium oxynitride films grown by low-pressure metal-organic chemical vapour deposition, composed of TiNxOy mixed with TiO2. The usual DC parameters (t, s and Φc), obtained from the effective media theory equations, are compared to the universal values (s = sun while t < tun because of the film anisotropy). This is the first example of an electrical continuum percolation applied to columnar films with chemically similar conducting and insulating units (non-heterogeneous percolation) whose mixing is based upon the growth temperature during the film growth.

Surfactant effect of Sb on the growth of Ag films on a sapphire substrate

1996

It is shown that a very thin layer of Sb may be used as a surfactant to modify the growth of silver films on an insulating substrate. The conduction (percolation) current flowing through a dispersed Ag film appears at a significantly smaller thickness due to the change in the growth mode of silver islands. Some practical applications are indicated.

Depletion-induced percolation in networks of nanorods.

2006

Above a certain density threshold, suspensions of rod-like colloidal particles form system-spanning networks. Using Monte Carlo simulations, we investigate how the depletion forces caused by spherical particles affect these networks in isotropic suspensions of rods. Although the depletion forces are strongly anisotropic and favor alignment of the rods, the percolation threshold of the rods decreases significantly. The relative size of the effect increases with the aspect ratio of the rods. The structural changes induced in the suspension by the depletant are characterized in detail and the system is compared to an ideal fluid of freely interpenetrable rods.

Gas transport through polymer membranes and free volume percolation

1998

We consider the influence of structural and dynamical properties of a polymer membrane on the gas transport through this matrix. The diffusant and the polymer only interact through repulsive interactions. In the case of a glassy polymer, when one can consider the matrix as frozen, the gas particle diffusion is determined by the free volume structure of the system. We show how the percolation properties of the free volume show up in a subdiffusive behavior of the diffusant. When one takes matrix mobility into account the ideal percolation transition vanishes but its trace can still be found in a subdiffusive regime in the gas particle mean square displacement. In the statically non-percolati…

Spontaneous symmetry-breaking pathways: time-resolved study of agarose gelation

1996

Abstract Extensive time-resolved studies of self-assembly of agarose gels, performed with the use of a variety of techniques allowed identification of the initial break of symmetry and the actual path leading to self-assembly at concentrations well below the random percolation threshold. The overall process is seen to occur through the following sequence: (i) break of symmetry in the sol, causing the spontaneous generation of mesoscopic polymer-rich and solvent-rich regions; (ii) percolation, or nearly percolation [see (iv) below], of polymer-rich regions through the sample, still in the sol state; (iii) start of polymer cross-linking within polymer-rich regions; (iv) progress of cross-link…

Irreversible gelation of thermally unfolded proteins:structural and mechanical properties of lysozyme aggregates

2010

The formation of protein aggregates is important in many fields of life science and technology. The morphological and mechanical properties of protein solutions depend upon the molecular conformation and thermodynamic and environmental conditions. Non-native or unfolded proteins may be kinetically trapped into irreversible aggregates and undergo precipitation or gelation. Here, we study the thermal aggregation of lysozyme in neutral solutions. We characterise the irreversible unfolding of lysozyme by differential scanning calorimetry. The structural properties of aggregates and their mechanisms of formation with the eventual gelation are studied at high temperature by spectroscopic, rheolog…

Alternating-Current Properties of Elastomer-Carbon Nanocomposites

2004

Controlling electrical percolation in multicomponent carbon nanotube dispersions

2011

Carbon nanotube reinforced polymeric composites can have favourable electrical properties, which make them useful for applications such as flat-panel displays and photovoltaic devices. However, using aqueous dispersions to fabricate composites with specific physical properties requires that the processing of the nanotube dispersion be understood and controlled while in the liquid phase. Here, using a combination of experiment and theory, we study the electrical percolation of carbon nanotubes introduced into a polymer matrix, and show that the percolation threshold can be substantially lowered by adding small quantities of a conductive polymer latex. Mixing colloidal particles of different …

The percolation phase transition and statistical multifragmentation in finite systems

2020

The cumulant ratios up to fourth order of the $Z$ distributions of the largest fragment in spectator fragmentation following $^{107,124}$Sn+Sn and $^{124}$La+Sn collisions at 600 MeV/nucleon have been investigated. They are found to exhibit the signatures of a second-order phase transition established with cubic bond percolation and previously observed in the ALADIN experimental data for fragmentation of $^{197}$Au projectiles at similar energies. The deduced pseudocritical points are found to be only weakly dependent on the $A/Z$ ratio of the fragmenting spectator source. The same holds for the corresponding chemical freeze-out temperatures of close to 6 MeV. The experimental cumulant dist…