A nanomatrix carbon composite is disclosed. The nanomatrix carbon composite includes a substantially-continuous, cellular nanomatrix comprising a nanomatrix material. The composite also includes a plurality of dispersed particles comprising a particle core material that comprises an allotrope of carbon dispersed in the nanomatrix and a bond layer extending throughout the nanomatrix between the dispersed particles. The nanomatrix carbon composites are uniquely lightweight, high-strength, high thermal conductivity materials that also provide uniquely selectable and controllable corrosion properties, including very rapid corrosion rates, useful for making a wide variety of degradable or disposable articles, including various downhole tools and components.