Thermal-Treated Pitches as Binders for TiB2/C Composite Cathodes |
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Authors: | Xiao-Jun Lü Jian Xu Jie Li Yan-Qing Lai Ye-Xiang Liu |
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Affiliation: | (1) School of Metallurgical Science and Engineering, Central South University, Changsha, 410083, P.R. China; |
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Abstract: | The effect of thermal treatment on the microstructure and properties of pitches and thermal-treated, pitch-based TiB2/C composite cathodes were investigated. Thermal treatments were performed at 473 K, 523 K, 573 K, 623 K, and 673 K (200 °C,
250 °C, 300 °C, 350 °C, and 400 °C), respectively. The results show that the aromaticity of the treated pitches increases
with an increasing thermal treatment temperature, and subsequently, the coking value and quinoline-insoluble (QI) content
increase from 60.62 wt pct to 79.09 wt. pct and from 8.97 wt pct to 32.54 wt pct when the treatment temperature increases
from 473 K to 623 K (200 °C to 350 °C). The volume fraction of coalesced mesophase in semicoke decreases with an increasing
thermal treatment temperature, and after 673 K (400 °C) is reached, the coalesced mesophase is almost invisible. The bulk
density and compressive strength of modified pitch-based cathodes increase with an increasing thermal treatment temperature
from 2.24 g cm−3 to 2.39 g cm−3 and from 24.21 MPa to 54.85 MPa, whereas open porosity decreases from 34.62 pct to 27.06 pct. Both electrical resistivity
and electrolysis expansion ratio first decrease and then increase with an increasing thermal treatment temperature, and the
lowest values (45.63 μΩ m and 0.65 pct) are achieved at 573 K (300 °C). Compared with those of the parent pitch-based cathode, the properties of
the modified pitch-based cathodes had improved significantly. The mechanisms of the improvements are discussed in the text. |
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