Method of preparing carbon fibers
A method of producing carbon fiber, yarns, and nonwoven carbon fiber cloths, includes forming suitable polymeric precursor microfibers and/or nanofibers using a centrifugal spinning process and decomposing at least a portion of the polymeric precursor fibers to form carbon fibers. The decomposition may be accomplished by treating the polymeric precursor fibers with acid vapor from an aqueous acid solution at a temperature of less than 250° C.
1. A method of producing activated carbon fibers and/or carbon fiber cloths, comprising:
placing a polymer into a body of a fiber producing device, the body comprising one or more openings, wherein the polymer comprises a carbon backbone having hydroxyl (—OH) pendant groups;
rotating the fiber producing device at a speed of at least about 500 rpm, wherein rotation of the fiber producing device causes the polymer in the body to be passed through one or more openings to produce microfibers and/or nanofibers comprising the polymer;
collecting at least a portion of the produced microfibers and/or nanofibers as fibers, yarns or self-standing nonwoven fine fiber cloths;
placing the polymeric fibers in a chamber comprising aqueous sulfuric acid vapors produced from an aqueous sulfuric acid composition at a temperature of less than 250° C. for a time sufficient to dehydrate at least a portion of the polymer fibers to produce partially carbonized polymer fibers.
2. The method of claim 1 , wherein the microfibers and/or nanofibers are created without subjecting the fibers, during their creation, to an externally applied electric field.
3. The method of claim 1 , wherein the polymer is a water soluble polymer.
4. The method of claim 1 , wherein the polymer is polyvinyl alcohol.
5. The method of claim 1 , further comprising dissolving and/or suspending the polymer in water prior to placing the polymer into the body of the fiber producing device.
6. The method of claim 5 , wherein the concentration of polymer in water is at least 5% by weight.
7. The method of claim 1 , further comprising positioning a substrate under the fiber producing device, wherein the produced microfibers and/or nanofiber mats are deposited onto a substrate or clamped at the edges for stand-alone nonwoven carbon fiber cloths.
8. The method of claim 7 , further comprising positioning the substrate in the chamber comprising aqueous sulfuric acid vapors.
9. The method of claim 1 , further comprising:
washing the fibers after the fibers have been treated with sulfuric acid vapors;
drying the fibers.
10. The method of claim 1 , further comprising placing the partially carbonized polymer fibers into a furnace and heating from 200 to 800° C. at a ramping rate between 2-10° C./min to convert the partially carbonized polymer fibers to activated carbon.
11. The method of claim 1 , further comprising placing the partially carbonized polymer fibers into a furnace and heating at a temperature between 800-2500° C. to produce carbon fiber.