Investigation of fabrication of Ti_4O_7 by carbothermal reduction in argon atmosphere and vacuum

摘要

High quality Ti_4O_7 powder was synthesized by carbothermal reduction in flowing argon atmosphere and in vacuum. Phase evolution sequences during reaction and influence of main technological parameters such as compacting pressure, different heating temperature and reducing time and carbon black mole ratio in flowing argon atmosphere were investigated by X-ray diffraction and scanning electron microscope. Concluding the effect of main technological parameters, the carbothermal reaction was mainly controlled by solid phase-boundary reaction between the TiO_2 and carbon black particles at the first stage. As the reduction progresses and the particle size increased, the contacting area between TiO_2 and carbon particles decreased. The indirect reactions reduced by CO gas proceeding through gaseous intermediates subsequently accelerate the rate of the whole reaction at the second stage. The Rietveld (R) plot result showed that high quality of 98.5 % content Ti_4O_7 powders were obtained at 1100 ℃ in flowing argon atmosphere for 2.5 h and they were mainly in regular cylindrical morphology with an average diameter of 5 um. The high quality of 87.5 % content Ti_4O_7 powders were obtained by reduced at 1025 ℃ in vacuum for 2 h and they were mainly in irregular spherical morphology with an average particle size of 2.10 μm. The resistance of the Ti_4O_7 powders and ceramics prepared by SPS showed that the good dispersed cylindrical Ti_4O_7 particles produced in argon atmosphere was good to fabricate Ti_4O_7 electrode.