Study On Preparation Of Carbon Black/Calcium Aluminate Cement And Its Applications In Refractory Castables

In order to improve the water wettability/dispersion of carbon materials,and improve the corrosion resistance of carbon-containing castables.Therefore,the casting ladle can be amorphous and the construction of the ladle is more convenient.Carbon black/calcium aluminate cement was prepared by carbon-bed sintering with aluminium source（alumina,aluminium sol,boehmite）,Ca O and carbon black as raw materials,polyvinylpyrrolidone（PVP）as a dispersant.The effects of the concentration of PVP aqueous solution,the type of aluminium source and carbon content on the phase composition and microstructure of the products was investigated by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry.The water wettability/dispersion and oxidation resistance of carbon black/calcium aluminate cement were analyzed by sedimentation test and thermogravimetry respectively.The hydration rate of carbon black/calcium aluminate cement was studied by using the hydration heat curve.Furthermore,the mechanical properties and corrosion resistance of corundum castables bond with secar71 cement,carbon black/calcium aluminate cement prepared by mechanical mixing and carbon-bed sintering（CB content 5 wt%,10wt%）were compared.The main results of the present paper are as follows:The dispersibility of carbon black in water can be improved when the concentration of PVP solution was 50g/L.After sintering at 1400℃for 4 h,the content of Ca O·Al₂O₃and Ca O·2Al₂O₃（CA₂）in the product is similar to that of commercial cement secar71,and the carbon black is evenly distributed between calcium aluminate particles.When the concentration of PVP solution was increased to 75 g/L and 100 g/L,the dispersion of carbon black was worse.When alumina is used as aluminium source,the phases of the sintered products are CA and CA₂,and their phase content is close to that of Secar71 cement.When boehmite is used as aluminium source,the product phases are CA,CA₂and a small amount of C₁₂A₇.When aluminium sol is used as aluminium source,the product phases are CA and CA₂,and the intensity of CA₂diffraction peak is obviously enhanced.The carbon black in the product can be uniformly mixed between calcium aluminate particles with alumina,aluminium sol and boehmite as aluminium sources.The addition of carbon black has no significant effect on the phase composition and morphology of the sintered products,but with the increase of carbon content,the growth of calcium aluminate particles is inhibited.Compared with the carbon black/calcium aluminate cement prepared by mechanical mixing,the carbon black/calcium aluminate cement prepared by carbon-bed sintering has better dispersion in water and higher oxidation resistance（oxidation rate reduced by 2%）.According to the analysis of the hydration heat curve,the carbon black/calcium aluminate cement prepared by carbon-bed sintering has a faster hydration rate.After drying at 110℃for 24 h,the cold crushing strength（CCS）and cold modulus of rupture（CMOR）of the castable bonded with Secar71 cement are the highest.After sintering at 1100℃and 1500℃for 3 h,the strength of the castables decreased with the increase of carbon content.Carcon black/calcium aluminate cement bonded corundum castable by carbon-bed sintering has the strongest slag erosion resistance.