The mortise and tenon structure enabling lamellar carbon composites of ultra-high bending strength

Abstract

• A novel approach is reported to produce carbon/carbon fiber composites of super bending strengths from nano diamonds and carbon fibers via a phase transformation by spark plasma sintering. • The unique “mortise and tenon structure” bestows the composite bulks with excellent mechanical properties. • The current composites possess the highest specific bending strength of all current high temperature structural materials reported so far. Carbon materials are important but find little application in bending components due to their unsatisfying bending strength (300-500 MPa). To fabricate carbon composites of high bending strength is a tough task, even using carbon fibers (CFs) structures as reinforcements. Here we report lamellar carbon composites of ultra-high bending strength (> 1.2 GPa) produced from CFs cloths coated with nano-diamond (ND) particles by spark plasma sintering (SPS). When NDs are sandwiched between CFs cloths, some ND particles penetrate into interstices between CFs. During the sintering, the ND particles are transformed into graphite onions; this transformation is associated with an active state of carbon atoms participating in the change. As a result, the carbon onions strongly bond the CFs together, helping consolidate the compacts into strong lamellar carbon composite bulks. The produced graphite onions from the NDs located at crossings of CFs tows form a robust mortise and tenon structure, which helps the bending strength of the lamellar composite from the compact of 40 wt.% NDs exceed 1.2 GPa. The as-prepared composite possesses the highest specific bending strength of all current high temperature structural materials reported so far. This work may pave a new way for high performance carbon materials.