Graphene oxide and multi walled carbon nanotubes introduced in AL2O3-SIC-SIO2-C refractory castable used in blast furnace trough: effects on rheology and high-temperature properties

Reference	Presenter	Authors (Institution)	Abstract
14-091	Norval Rodrigues de Oliveira Jr	Oliveira Jr, N.R.(rhimagnesita); Brito, M.A.(rhimagnesita); Ribeiro, F.A.(Centro de Desenvolvimento de Tecnologia Nuclear); Furtado, C.A.(Centro de desenvolvimento de Tecnologia Nuclear); Santos, A.P.(Centro de Desenvolvimento da Tecnologia Nuclear); Fernandes, M.R.(Universidade Católica de Minas Gerais); Dutra, P.(Centro de desenvolvimento de tecnologia nuclear);	Al2O3-SiC-SiO2-C based refractory castables are mostly used with success to build up troughs to transport hot metal and slag during the blast furnace pouring. Some sources of carbon are welcome in its composition, mainly solid pitch, but there are some limitation regarding to increase the carbon amount, mainly because the difficulty of carbon incorporation in aqueous medium. In this work, hydrophilic nanocarbons, such hydroxyl-functionalized multi-walled carbon nanotubes (MWCNT-OH), purchased from Cheap Tubes and graphene oxide (GO), bought from Nacional de Grafite Ltda, were selected in order to evaluate their effects on the rheology, workability and properties after firing of Al2O3-SiC-SiO2-C based refractory castables. MWCNT-OH material (0.15 wt% in relation to the castable mass) was introduced directly in the castable before water addition and GO (0.03% and 0.05%) after being dispersed in water with ultrasonication. The nanocarbons were characterized by TGA, SEM, TEM and Raman spectroscopy. The composites were evaluated regarding fresh workability and properties after firing at 1400 °C, such as apparent density, apparent porosity, cold strength (CS) and porous size. It is noteworthy that none of the nanocarbons have a relevant influence on the fresh rheology of the castables. In relation to the original castable properties after firing, the introduction of nanocarbons reduced the average pore size and increased the CS modulus. The best results were observed for GO addition. While MWCNT-OH showed tendency to increase the CS modulus in more than 10%, an increase by 1.5 times was observed at a GO amount three times smaller
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