High-temperature tensile cell forin situreal-time investigation of carbon fibre carbonization and graphitization processes

A new high-temperature fibre tensile cell is described, developed for use at the Advanced Photon Source at Argonne National Laboratory to enable the investigation of the carbonization and graphitization processes during carbon fibre production. This cell is used to heat precursor fibre bundles to temperatures up to ∼2300°C in a controlled inert atmosphere, while applying tensile stress to facilitate formation of highly oriented graphitic microstructure; evolution of the microstructure as a function of temperature and time during the carbonization and higher-temperature graphitization processes can then be monitored by collecting real-time wide-angle X-ray diffraction (WAXD) patterns. As an example, the carbonization and graphitization behaviour of an oxidized polyacrylonitrile fibre was studied up to a temperature of ∼1750°C. Real-time WAXD revealed the gradual increase in microstructure alignment with the fibre axis with increasing temperature over the temperature range 600–1100°C. Above 1100°C, no further changes in orientation were observed. The overall magnitude of change increased with increasing applied tensile stress during carbonization. As a second example, the high-temperature graphitizability of PAN- and pitch-derived commercial carbon fibres was studied. Here, the magnitude of graphitic microstructure evolution of the pitch-derived fibre far exceeded that of the PAN-derived fibres at temperatures up to ∼2300°C, indicating its facile graphitizability.

Denitrification with ɛ-caprolactam by acclimated mixed culture and by pure culture of bacteria isolated from polyacrylonitrile fibre manufactured wastewater treatment system

The aim of this study is to isolate denitrifying bacteria utilizing ɛ-caprolactam as the substrate, from a polyacrylonitrile fibre manufactured wastewater treatment system. The aim is also to compare the performance of PAN (polyacrylonitrile) mixed bacteria cultures acclimated to ɛ-caprolactam and isolated pure strain for treating different initial e-caprolactam concentrations from synthetic wastewater under anoxic conditions. The result showed that the PAN mixed bacteria cultures acclimated to e-caprolactam could utilize 1538.5 mg/l of ɛ-caprolactam as a substrate for denitrification. Sufficient time and about 2200 mg/l of nitrate were necessary for the complete ɛ-caprolactam removal. Paracoccus thiophilus was isolated from the polyacrylonitrile fibre manufactured wastewater treatment system and it could utilize 1722.5 mg/l of ɛ-caprolactam as a substrate for denitrification. About 3500 mg/l of nitrate was necessary for the complete removal of ɛ-caprolactam. When the initial ɛ-caprolactam concentration was below 784.3 mg/l, the removal efficiency of ɛ-caprolactam by Paracoccus thiophilus was better than that for the PAN mixed bacteria cultures. The growth of Paracoccus thiophilus was better. However, when the initial ɛ-caprolactam concentration was as high as 1445.8 mg/l, both the ɛ-caprolactam removal efficiency by Paracoccus thiophilus and Paracoccus thiophilus specific growth rate were similar to the PAN mixed bacteria cultures.