Changes in physical properties with varying impregnation temperatures and compression times during fabrication of carbon blocks using needle cokes and pitch

Abstract

Abstract Impregnation was conducted to decrease the pores formed during the carbonization process after manufacturing carbon blocks using needle cokes and coal tar pitch. This was carried out in the order of heating, subjecting to vacuum, and compression, and changes in mechanical and electrical properties before and after impregnation were analyzed with impregnation temperature and compression time as variables. The impregnation temperatures were 150, 200, and 250°C, and compression times were 30, 60, and 90 min. The optimal impregnation temperature was 200°C, resulting in a 12.5% increase in bulk density and a 26.0% decrease in porosity after impregnation of the carbon blocks. The optimal compression time was 60 min, leading to a 14.3% increase in bulk density and a 24.0% decrease in porosity after impregnation. Under the selected optimal conditions, after three impregnation cycles, the bulk density increased by 33.8% compared to the initial state (0 cycles 1.259 g/cm³ → 3 cycles 1.685 g/cm³), and porosity decreased by 56.8% (0 cycles 39.1% → 3 cycles 16.9%). According to the performance evaluation of carbon blocks, electrical resistivity decreased by 52.0% (72.5 µΩm → 34.8 µΩm) and flexural strength increased by 368.3% (6.0 MPa → 28.1 MPa). The substantial increase in flexural strength was attributed to the reduction in porosity.