Computer Simulation of Percolation Structure in Composites

Abstract

Two-dimensional computer simulations were conduct ed on percolative structure in which second phases of various aspect ratios were arranged in a matrix phase. The second phases were randomly arranged in an array with two different computational programs; one pro hibiting an overlap among second phases and the other allowing the overlap. From the simulation prohibiting the overlap, it was predicted that a continuous path was formed at less amounts of the second phase with higher aspect ratios.In the simulation allowing the overlap, a continuous path throughout the array was formed by arranging the second phase of an aspect ra tio of 100 with less than 4% in the array. These results agreed well with the conduction path formation in hot pressed ceramic composites consisting of an insulator matrix and electrically conductive whisker additives.

Effects of TIG surface treating on microstructural characteristics and mechanical properties of Al2O3–TiB2 coating by APS

“…Due to TiB 2 oxidisation during atmosphere plasma spraying, TiB 2 content in as sprayed coating is 24·2 wt-, decreased by about 5 wt- than that in spraying powder according to XRD quantitative analysis. By SEM image analysis, TiB 2 volume fraction in as sprayed coating can be evaluated and reaches 19–21, which greatly approaches the percolation limit about the electroconductive ceramic composites described by Ishida et al 16 This probably is one of the reasons that the as sprayed coating has an certain electroconductibility. In addition, TiB 2 particles dispersedly distribute in the lamellar matrix of the coating and may contact each other resulting in the formation of a conductive network, i.e.…”

Effect of Microstructure on the Thermal Conductivity of Hot‐Pressed Silicon Nitride Materials

“…10 for thermal conductivity in the studied composites is then in agreement with the limits given for percolation in three-dimensional models. Other authors 23 have shown that this critical concentration decreased with the aspect ratio of the second phase, therefore, in Si 3 N 4 materials, the critical concentration for large grain percolation, i.e., for getting a thermal conduction continuous path along high-conductivity grains, should diminish as the aspect ratio of these elongated grains increases.…”

Stability and electrical properties of MoSi2‐ and WSi2‐oxide electroconductive composites

“…These results imply that particle distribution in the composite systems is highly influenced by matrix/reinforcement particle size ratio and particle size of reinforcement itself, which could also affect the electrical properties. It is reported that improved distribution, particles with large aspect ratios and also lower size ratio of conductive to insulating particles could provide significant advantage for formation of continuous percolating network and also for lowering the percolation concentration . Therefore, achieving highly homogeneous microstructures is very important to lower the critical percolation concentration and to fabricate metal silicide‐refractory oxide composites that are electrically conductive even at low metal silicide contents.…”