Abstract: Exfoliated graphite/coke composites modified by ZrO₂ nanoparticles were produced using two different techniques and characterized by means of X-ray diffraction, scanning and transmission electron microscopy. In the first, low-density exfoliated graphite/coke blocks were dipped repeatedly and alternately in ZrO(NO₃)₂ and NH₄OH solutions and subsequently heat treated at 1200℃ in nitrogen to deposit thin layers of ZrO₂ nanoparticles on the free surfaces of the carbon matrix. In the second, a mixture of expandable graphite, phenol-formaldehyde resin powder, and ZrOC₂O₄-modified fibrous cellulose in a sealed container was submitted to thermal shock at 900℃ followed by heat treatment at 1200℃ in nitrogen to obtain the modified composites. The ZrO₂ nanoparticles formed in the second technique were incorporated into the composites in three length scales: 6-30nm-isolated nanoparticles and small blobs, 200-1000nm-lengthy dendrite-like structures, and thin layer adhering to the surface of the 1-40μm long cellulose carbon fibers.