1 EFFECT OF CHEMICAL DISPERSING BY COLLOIDAL SILICA ON WATER WETTABILITY AND OXIDATION RESISTANCE OF FLAKE GRAPHITE Ahmad Reza Abbasian and Mohamad Hassan Amin * Materials and Energy Research Centre, Karaj, Iran ABSTRACT Surface treatment is one of the most effective techniques to improve the water wettability and oxidation resistance of graphite being used in castable refractories. In this work, the above characterizations of treated graphite using colloidal silica via chemical dispersing method were investigated. The results showed the water wettability of the flake graphite greatly improved when the minimum concentration of colloidal silica was more than 0.0025 g(SiO 2 )/cm 3 (water). The effect of surface treated graphite on rheology and mechanical properties of alumina-silicon carbide-graphite castable refractory has been investigated. The addition of surface treated graphite as an additive to alumina-silicon carbide-graphite significantly influenced the consistency performance and strength of castable refractory. INTRODUCTION Carbon containing refractories have been attracting great attention because of their unique properties such as high thermal conductivity, low thermal expansion, high resistance to thermal shock and chemical inertness to the slag (Mohamed & Ewais, 2004). However, trying to incorporate carbon/graphite in castables introduces many new problems arising from, e.g. its poor water wettability and oxidation resistance, which have hindered the development and application of graphite containing castable refractories (Zhang & Lee, 2003). To overcome the above drawbacks, various methods have been investigated. Zhang and Lee (2002) have reviewed the advantages and disadvantages of these methods. In recent years, coating the surface of graphite via sol gel method with materials such as ZrO 2 (Sunwoo et al., 2000), Al 2 O 3 (Bahlawane, 2001), Al 2 O 3 -based metal oxides (Kawabatak et al., 2001) SiO 2 , Al 2 O 3 –SiO 2 (Zhang & Lee, 2003) and MgAl 2 O 4 spinel (Saberi et al., 2009) have been reported. However, expensive raw materials and complex process in sol gel technique makes it unacceptable by the refractory industries. Therefore, in this study, we have chosen a type of commercially colloidal silica, as hydrophilic agent, which is selected by considering cheap and economic material and coat it on the surface of flake graphite by chemical dispersing which is a cheap and simple technique for industrial application. The aim of this work is to minimise the negative effects associated with the hydrophobicity of flake graphite on graphite containing castables. Improved knowledge on the effects of chemical dispersing of colloidal silica on the water wettability and oxidation resistance * Corresponding author. Industrial Chemistry & Advanced Materials Group, School of Applied Sciences, RMIT University, Melbourne, Australia. Tel. +61422101904; Email: mohamadhassan.amin@rmit.edu.au