Disclosed are techniques and methods for producing silicon carbide and ceramic matrix composites from hydrocarbons. In one aspect, a method includes preforming a shape using silicon carbide fibers placed into a chamber, evacuating the chamber causing a silicon and polymer slurry to enter the chamber, and pressurizing the chamber causing the silicon and polymer slurry to permeate the silicon carbide fibers. The method includes heating the chamber to cause pyrolysis of the polymer and a hydrocarbon passed into the chamber into carbon and hydrogen gas. The carbon from the pyrolyzed polymer and hydrocarbon provide a coating of carbon on the silicon in the silicon and polymer slurry. The method includes heating the chamber to a higher temperature causing the silicon to melt and react with the carbon to form silicon carbide. The formed silicon carbide and the silicon carbide fibers form the ceramic matrix composite.