heat resistant carbide so as to make a carbide ceramic layer at the fiber surface portion alone or together with part of the fiber inner layer the term heat resistant carbide as used herein includes sic zrc tic hfc b 4 c nbc and wc of which sic zrc tic and hfc are preferred the term compound capable of forming a heat resistant carbide includes halides hydrides and organometallic compounds of si zr ti hf b nb and w such as for example sicl 4 sih 4 zrcl 4 ticl 4 and hfcl 4 these compounds are reacted normally in gaseous phase with carbon fiber the carbide forming reaction is carried out preferably in the presence of hydrogen the amount of which depends upon reaction temperature gas feed rate fiber quantities type of furnace and other parameters hydrogen is added usually in an amount less than five times preferably 0 1 5 times the amount of the carbide forming compound the reaction is effected at atmospheric or in vacuum normally at 0 1 760 mmhg preferably 10 760 mmhg more preferably 50 760 mmhg and with or without addition of an inert gas such as n 2 nh 3 ar he ne kr xe and rn for dilution of the reaction mixture the carbide forming reaction temperature is 800 u00b0 c 1 700 u00b0 c preferably 1 000 u00b0 c 1 500 u00b0 c lower temperatures than 800 u00b0 c would fail to give a carbide fiber with adequate thickness while higher temperatures than 1 700 u00b0 c would result in a carbide film lacking uniformity and fine texture the manner of heating the carbon fiber is not particularly restricted it may be heated by joule 39 s effect or with induction.