a coating composite is provided for a platform surface of an antenna array for , when applied to the platform , affording isolation of radiating and receiving antennas of the array . the coating composite includes a plurality of conductively coated elongate tubes dispersed in an insulating polymer matrix at a volume loading density approaching that at which the composite begins to conduct electrically over macroscopic distances , i . e ., close to the percolation threshold . the tubes are preferably comprised of microtubules comprised of biologically - derived , high - aspect rod - shaped particles of microscopic dimensions having an electroless plated metal coating thereon .