Evaluating multi‐step oxidative stabilization behavior of coal tar pitch‐based fiber

Abstract

Oxidative stabilization is an important step for isotropic pitch-based carbon fiber preparation; coal tar pitch-based fiber is treated by multi-step oxidative stabilization under various conditions to investigate the oxidative stabilization mechanism. The chemical structure changes of isotropic pitch-based fiber during the oxidative stabilization and carbonization stage are systematically characterized by In-situ diffuse reflectance infrared Fourier transform, elemental analysis, mass spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance, scanning electron microscope with an energy dispersive X-ray spectrometer. These results show that the oxygen distribution gradient in oxidative stabilized fiber radial direction become homogeneously with the increasing of oxidation temperature and time under multi-step oxidative stabilization. The resultant carbon fiber shows tensile strength of 942 ± 42 MPa and Young's modulus of 42.8 ± 3.1 GPa due to appropriate oxygen content, homogeneous oxygen distribution, more cross-link bond (C-O-C) content, higher aromaticity and lower weight loss introduced in multi-step oxidative stabilized pitch fiber. The multi-step oxidative stabilization provides synergy effect between reaction rate and the oxygen diffusion rate as well as eliminates the oxygen concentration gradient, it provides an time-saving and energyeffective method for the oxidative stabilization of isotropic pitch-based carbon material (pitch fiber, pitch microsphere, etc.) and improve the resultant carbon material performance.

Synthesis of Carbon Nanofibers Film from Coal Liquefaction Residues: Effect of HNO3 Pretreatment

“…According to Figure S3, the L-CLRPA/PAN film has a higher O and N content and a lower C and H content than that of the CLRPA/PAN film. The C 1s and O 1s peaks can be devalued into five and four peaks, respectively, as shown in Figure a,b. , The specific peak site and corresponding groups are shown in Table S1. , The L-CLRPA/PAN film shows higher contents of peak 4 (carbonyl group, CO) and peak 5 (carboxyl group, COOH) (Figure d) than the CLRPA/PAN film. Conversely, peaks 1 and 4 of the O 1s exhibit a similar variation tendency (Figure e).…”

“…Yang et al, for example, created a high SP (268 °C) pitch from coal pitch using hydrogenation, polymerization, vacuum, and other processes, resulting in good spinnability . To improve the oxidizing stability of SP pitch-based CFs, optimization of the start temperature, heating rate, or multistep has been employed. ,, Although the aforementioned methods can improve the preparation of low SP pitch-based CF, spinnability is reduced and the cost is greatly increased. Previous research has found that high oxidizing conditions, such as in the presence of iodine, chlorine, or a stronger oxidizing agent, , can accelerate polymerization.…”

“…To improve the oxidizing stability of SP pitch-based CFs, optimization of the start temperature, heating rate, or multistep has been employed. ,, Although the aforementioned methods can improve the preparation of low SP pitch-based CF, spinnability is reduced and the cost is greatly increased. Previous research has found that high oxidizing conditions, such as in the presence of iodine, chlorine, or a stronger oxidizing agent, , can accelerate polymerization. Because of its strong oxidizing property and solution controllability, HNO 3 solution has been frequently chosen as the oxidizing agent to improve the stabilization process and avoid fiber melting …”

“…15 temperature, heating rate, or multistep has been employed. 14,16,17 Although the aforementioned methods can improve the preparation of low SP pitch-based CF, spinnability is reduced and the cost is greatly increased. Previous research has found that high oxidizing conditions, such as in the presence of iodine, 12 chlorine, 17 or a stronger oxidizing agent, 18,19 can accelerate polymerization.…”

Transcrystalline growth of PLLA on carbon fiber grafted with nano-SiO 2 towards boosting interfacial bonding in bone scaffold

“…Fiber-reinforced technique is regarded as an effective method to enhance the mechanical properties of polymers because of the many advantages of fiber materials such as high strength, modulus and stiffness [ 1 , 2 ]. Among various fibers, carbon fiber (CF) with high strength and modulus which can reach 942 MPa and 42.8 GPa, respectively, is considered as the most promising fiber material acting as reinforcement phase [ 3 , 4 ]. The reinforcement effect of CF can be achieved by means of that CF bears the loading transferred from polymer matrix and absorbs partial fracture energy.…”