300 research outputs found
Two-step percolation in aggregating systems
The two-step percolation behavior in aggregating systems was studied both
experimentally and by means of Monte Carlo (MC) simulations. In experimental
studies, the electrical conductivity, , of colloidal suspension of
multiwalled carbon nanotubes (CNTs) in decane was measured. The suspension was
submitted to mechanical de-liquoring in a planar filtration-compression
conductometric cell. During de-liquoring, the distance between the measuring
electrodes continuously decreased and the CNT volume fraction
continuously increased (from up to % v/v). The two
percolation thresholds at and can reflect the interpenetration of loose CNT aggregates and
percolation across the compact conducting aggregates, respectively. The MC
computational model accounted for the core-shell structure of conducting
particles or their aggregates, the tendency of a particle for aggregation, the
formation of solvation shells, and the elongated geometry of the conductometric
cell. The MC studies revealed two smoothed percolation transitions in
dependencies that correspond to the percolation through the
shells and cores, respectively. The data demonstrated a noticeable impact of
particle aggregation on anisotropy in electrical conductivity
measured along different directions in the conductometric cell.Comment: 10 pages, 6 figure
Jamming and percolation of parallel squares in single-cluster growth model
This work studies the jamming and percolation of parallel squares in a
single-cluster growth model. The Leath-Alexandrowicz method was used to grow a
cluster from an active seed site. The sites of a square lattice were occupied
by addition of the equal size squares (E-problem) or a mixture of
and () squares (M-problem). The larger
squares were assumed to be active (conductive) and the smaller squares were assumed to be blocked (non-conductive). For equal size
squares (E-problem) the value of was
obtained for the jamming concentration in the limit of .
This value was noticeably larger than that previously reported for a random
sequential adsorption model, . It was observed that the
value of percolation threshold (i.e., the ratio of the area of
active squares and the total area of squares in the
percolation point) increased with an increase of . For mixture of and squares (M-problem), the value of
noticeably increased with an increase of at a fixed value of and
approached 1 at . This reflects that percolation of larger
active squares in M-problem can be effectively suppressed in the presence of
smaller blocked squares.Comment: 11 pages, 9 figure
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