Study On Pitch-binder Modification Of TiB₂/C Composite Cathode By Thermosetting Resin For Aluminum Electrolysis

Funded by the National High-Tech Research and Development Program ("863"project) of China and the National Science & Technology Pillar Program of China, modification technology of pitch by thermosetting resin were studied, and then using TiB2 as functional materials, thermosetting resin-modified pitch as binder system, carried out the material research and development of TiB2/C composite cathode with high-strength, high conductivity, and anti-penetration to electrolyte leakage. Main work and results are as follows:(1) Single phenolic resin, furan resin, epoxy resin were used to modify pitch, some conventional properties such as softening point, viscosity, coking value of modified pitch binder were test, the ablation performance, molecular structure, charring behavior, semicoke structure of pitch before and after modified by thermosetting resin were studied. The results showed that after adding an appropriate amount of furan resin or epoxy resin, the pitch binder had improved cohesion and flexibility, the degree of aromatization of the binder enhanced.(2) In consideration of the characteristic of epoxy resin that it could not self-cure and the requirement of aluminum electrode material for higher binder residual carbon, proposed the idea that using composite resin (phenolic/epoxy resin, furan/epoxy resin) which is consist of epoxy resin and high residual carbon curing agent for epoxy resin to modify pitch. The results showed that there was a synergistic effect between furan resin (curing agent for epoxy resin) and epoxy resin when used for pitch modification, The high-temperature carbon yield of furan/epoxy modified pitch was higher than that of single furan resin or epoxy resin modified pitch, the degree of aromatization of the molecular, the cohesion and flexibility of pitch binder were further enhanced comparing to single resin modified pitch.(3) Determined the basic ingredient and preparation process of modified pitch bonded TiB2/C composite cathode, the effects of pitch modification by thermosetting resin on the physical properties of TiB2/C composite cathode material such as bulk density, porosity, resistivity, and compressive strength were studied, the optimal resin dosage and the optimal ratio of epoxy resin and curing agent were determined too. Furthermore, the electrolysis expansions of thermosetting resin modified pitch bonded TiB2/C composite cathodes were studied. When the total content of resin additive was 12wt%, the ratio of epoxy resin and furan resin (epoxy resin curing agent) was 1:1, the furan/epoxy modified pitch based TiB2/C composite cathode showed better physical properties and electrolysis expansion resistance, compared to the original pitch bonded TiB2/C composite cathode material, the resistivity and electrolysis expansion rate decreased by 26.2% and 25.9%, the bulk density and compressive strength increased by 1.6% and 54.5%, respectively.