US Patent 7214430 Composite material

A composite material includes a matrix and carbon fibrous structures. The carbon fibrous structure has a three dimensional network of carbon fibers, each having an outside diameter of 15–100 nm, and has a granular part with which carbon fibers are bound in a state such that the carbon fibers extend outwardly from the granular part, and the granular part being produced in a growth process of the carbon fibers. The additive amount of the carbon fibers is in the range of 0.1 to 30% by weight of total weight of the composite material.