A fiber pre-oxidization device of the present disclosure basically has a transmitting unit and a microwave processing unit. The microwave processing unit is installed with at least one magnetron and a gas supplying unit, wherein the magnetron is disposed at an oven body of the transmitting unit, and the gas supplying unit is connected to the oven body. By focusing the microwave, an ultra-fast pre-oxidization process is applied on a fiber yarn bunch which continuously passes the oven body, and thus the fiber yarn bunch is processed to form an oxidation fiber yarn bunch. Thus, not only an oxidization time of an oxidation fiber can be reduced, but also the shell-core structure of the oxidation fiber can be reduced. Even, the oxidation fiber has no obvious shell-core. Accordingly, relatively positive and reliable means for increasing the performance of carbon fiber are provided.

Examples of a flexible pyrolysis system are provided that include at least one reaction chamber capable of pyrolyzing a combination of coal in a supercritical carbon dioxide (CO.sub.2) atmosphere. The system includes a recuperating and condensing circuit that removes dissolved pyrolysis products from the supercritical CO.sub.2 atmosphere and then recovers CO.sub.2 for reuse in the reaction chamber. The recuperating and condensing circuit includes multiple stages of recuperators and collectors that can be independently controlled in order to selectively fractionate the pyrolysis products. In addition, the pyrolysis reaction may be controlled to alter the pyrolysis products generated.

An example oven for heating fibers includes a chamber having upper and lower portions and a supply structure between first and second ends of the chamber, wherein the supply structure is in communication with a first heating system and is configured to direct first heated gas from the first heating system into the upper portion of the chamber to heat fibers in the upper portion at a first temperature, and wherein the supply structure is in communication with a second heating system and is configured to direct second heated gas from the second heating system into the lower portion of the chamber to heat fibers in the lower portion at a second temperature different than the first temperature such that the upper and lower portions of the chamber maintain the different temperatures without a physical barrier between the upper and lower portion.

An example oven for heating fibers includes a chamber having upper and lower portions and a supply structure between first and second ends of the chamber, wherein the supply structure is in communication with a first heating system and is configured to direct first heated gas from the first heating system into the upper portion of the chamber to heat fibers in the upper portion at a first temperature, and wherein the supply structure is in communication with a second heating system and is configured to direct second heated gas from the second heating system into the lower portion of the chamber to heat fibers in the lower portion at a second temperature different than the first temperature such that the upper and lower portions of the chamber maintain the different temperatures without a physical barrier between the upper and lower portion.

One embodiment is directed to an oven for heating fibers. The oven comprises a plurality of walls forming a chamber and a supply structure disposed within the chamber between first and second ends of the chamber. The supply structure is in communication with a first heating system and is configured to direct heated gas from the first heating system into a first portion of the chamber. The supply structure is in communication with a second heating system and is configured to direct heated gas from the second heating system into a second portion of the chamber.

Pitch compositions suitable for spinning may comprise: a pitch having a softening point (SP) below 400 C. and is capable of achieving a radial Hencky strain prior to break of about 0.7 to about 10, at spinning temperature (T.sub.s) ranging from about SP30 C. to about SP+80 C. Methods for producing a carbon fiber from a pitch composition at a temperature within a spinning temperature (T.sub.s) range may comprise determining a temperature range wherein the maximum radial Hencky strain (.sub.R) lies above a minimum process radial Hencky strain, and wherein the minimum process radial Hencky strain is within a range of about 0.7 to about 10. The spinning temperature (T.sub.s) range may be determined by measuring a maximum radial Hencky strain (.sub.R) prior to break at a series of different temperatures and strain rates. Carbon fiber composites may comprise of the said carbon fiber.