Influence of MWCNT distribution in alumina prepared by colloidal processing for EDM applications

Ceramics are known for their high temperature stability, hardness, wear resistance and chemical inertness which make them an ideal choice in designing devices for extreme conditions. Machining of ceramics using conventional methods are ruled out owing to their extreme hardness and brittleness. Non-traditional machining techniques, such as electrical discharge machining (EDM), can precisely shape these ceramics with exceptional resolution without direct contact, provided the ceramics possesses a minimum electrical conductivity of 1 S/m. A common approach to machine ceramics is to prepare ceramic composites by reinforcing conducting elements in a ceramic matrix followed by thermal treatment such as spark plasma sintering or hot pressing. In this research work, electrically conductive alumina composites were prepared by reinforcing multi-walled carbon nanotubes (MWCNT) using an aqueous slip casting route followed by pressure-less sintering. Significant changes were observed in rheological, electrical and mechanical properties of the sintered alumina composites upon reinforcement of MWCNT. Thus, alumina with 2 wt.% of MWCNT has an electrical conductivity of 1.9549 S/m which is sufficient to process the composites in EDM. The successful machining of alumina-MWCNT composites in EDM also confirmed sustainable slip casting route for MWCNT in alumina matrix along with adequate electrical conductivity for EDM.