Mechanical and Electrical Properties of Multiwalled <scp>CNT</scp> ‐Alumina Nanocomposites Prepared by a Sequential Two‐Step Processing of Ultrasonic Spray Pyrolysis and Spark Plasma Sintering

Abstract

The high tensile strength and electrical conductivity as well as high aspect ratio of carbon nanotube ( CNT ) are known to effectively improve the brittleness and electrical properties of ceramic materials; however, the agglomeration of CNT s during in the synthetic process and the poor interfacial bonding between CNT s and matrix materials still present challenges. Herein, multiwalled carbon nanotube ( MWNT )‐alumina composites were prepared, with homogeneously dispersed MWNT s in an alumina matrix, using a sequential two‐step process via ultrasonic spray pyrolysis followed by a spark plasma sintering process. To mix these two materials at the molecular level, MWNT ‐alumina composites were prepared using a precursor solution containing Al ions instead of solid aluminum oxide particles as the starting material. The agglomeration of MWNT s at high concentration, which is a main obstacle to solution processing, was minimized using ultrasonic spray pyrolysis. The dc conductivity of pure α‐alumina, possessing substantial insulating properties, was increased to 12.2 S/m by incorporating 2.48 wt% of MWNT s with a low percolation threshold under 0.18 wt%. With the same amount of MWNT , the fracture toughness of the composite was increased 2.5 times. The improved electrical and mechanical properties of the composites are discussed based on the microstructural characteristics of the composites.