High density carbon-carbon friction materials

A method for making a carbon-carbon composite brake disc, the method comprising:

• pyrolyzing a pitch in a preform using a controlled pressure and temperature ramp rate to control a growth of optical textures formed as the pitch is pyrolyzed to a coke matrix, wherein the preform comprises carbon fibers or carbon-precursor fibers, wherein the pitch comprises at least one isotropic pitch, and wherein pyrolyzing the pitch using the controlled pressure and temperature ramp rate comprises:
• heating the pitch and the preform in a vessel at a first pressure less than about 2000 pounds per square inch (psi) at a first temperature ramp rate between about 5 degrees Celsius per hour (5° C./hr) and about 50° C./hr to a first target temperature less than about 450 degrees Celsius (° C.) to convert at least some of the pitch to the coke matrix, wherein the coke matrix includes at least one optical texture;
• increasing a pressure in the vessel from the first pressure to a second pressure between 2000 psi and about 15,000 psi;
• and
• heating the pitch and the preform in the vessel at the second pressure, at a second temperature ramp rate between about 5° C./hr and about 50° C./hr to covert the remaining pitch to the coke matrix.

An assembly for making a carbon-carbon composite comprising:

• a vessel;
• a pitch-infiltrated preform in the shape of the carbon-carbon composite disposed in the vessel, wherein the pitch-infiltrated preform comprises:
• an isotropic pitch, and
• a preform derived from:
• a plurality of layers comprising carbon fibers or carbon-precursor fibers, and
• needled fibers comprising carbon fibers or carbon-precursor fibers;
• and
• a pressure and heat source, wherein the pressure and heat source are configured to apply a first pressure less than about 500 pounds per square inch (psi) to the pitch-infiltrated preform deposited in the vessel and heat the pitch-infiltrated preform over a first range of temperatures at a first temperature ramp rate between about 5 degrees Celsius per hour (5° C./hr) and about 50° C./hr to initiate pyrolysis of the isotropic pitch to a coke matrix, and then apply a second pressure greater than about 10,000 psi to the pitch-infiltrated preform deposited in the vessel and heat the pitch-infiltrated preform over a second range of temperatures at a second temperature ramp rate between about 5° C./hr and about 50° C./hr to complete pyrolyze the isotropic pitch to coke matrix.