Effects of co-carbonization of medium and low temperature refined pitch and high temperature refined pitch on the structure and properties of needle coke

Abstract

Needle coke has attracted much attention as a high-quality raw material for high-power graphite electrodes and other advanced functional materials. In this study, needle coke was prepared by co-carbonization of medium and the low temperature coal tar refined pitch (RCTP) and the high temperature coal tar refined pitch (RHCTP). The effect of co-carbonization of blended refined pitches with different proportions on the structure and properties of needle coke was studied. Elemental analysis, 1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry revealed the effect of changes in the key components of the blended refined pitch on the structure of needle coke. In addition, the structure and properties of needle coke were analyzed by polarized light microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and powder resistivity. The results showed that adding RHCTP to RCTP can increase the content of aromatic hydrocarbons and reduce the content of heterocyclic compounds in the blended refined pitch, which was beneficial to the evolution and growth of carbonaceous structures. The fiber content of needle coke (N-R-C-15) prepared by adding 15 wt% RHCTP to RCTP was 50 wt%, the optical texture index (OTI) of the coke was 63.04, Lc= 8.387 nm, La= 18.17 nm, d002 = 0.3427 nm, the content of well-aligned carbon microcrystals was 91.17 wt%, and the content of perfect graphite crystals reached 24.37 wt%. As the ratio of RHCTP in RCTP increased, the needle coke exhibited more fibrous structures, the degree of defects in graphite crystals decreasing, and the degree of graphitization increasing. In addition, with the increasing proportion of RHCTP in RCTP, the average resistivity of needle coke decreased from 167.55 μΩ·m to 144.5 μΩ·m, and the average powder compaction density increased from 1.065 g/cm3 to 1.206 g/cm3.