ROLE OF SULFUR IN THE PRODUCTION OF CARBON-FIBERS IN THE VAPOR-PHASE

Iron particles do not grow filaments in a methane atmosphere profusely enough to make a continuous reactor practical. Adding small quantities of sulfur to the iron vastly increases filament formation. We show that this is because the sulfur liquefies the iron particle, enhancing filament nucleation. With continued increases in sulfur, the number of filaments produced continues to increase, but quality, measured by length and straightness, decreases. We attribute this to higher sulfur concentration in the catalyst particle moving the melting point above the eutectic, thus decreasing the efficiency of filament lengthening.