SiC/ZrC/C ultra-thin composite fibers were fabricated by high-temperature pyrolysis treatment of as-electrospun fibers from polycarbosilane and polyzirconoxane blend solution. The phase transition during pyrolysis process was investigated and the results revealed that polycarbosilane was converted to amorphous SiC and extra carbon, while polyzirconoxane was converted to t-ZrO2 at 1200 degrees C. Then, amorphous SiC was converted to cubic SiC and extra carbon from polycarbosilane served as carbon source for the carbothermal formation of cubic ZrC at 1600 degrees C. Meanwhile, the carbon oxide generated during the carbothermal reduction process led the ceramic fibers to form mesoporous structure. The obtained mesoporous fibers are highly crystalline SiC/ZrC/C ternary composite fibers. (C) 2014 Elsevier B.V. All rights reserved.