Preparation of carbon nanotube doped ceramic powders for plasma spraying using heterocoagulation method

Incorporation of carbon nanotubes (CNT) in thermally sprayed ceramic coatings is expected to improve its properties. However, it is difficult to disperse CNT in the thermal spray feedstock homogeneously since they tend to form agglomerates. Homogeneous dispersion of CNT is possible using a colloidal processing technique known as heterocoagulation. This paper deals with three ceramic powders heterocoagulated with CNT, namely, agglomerated alumina, crushed alumina and crushed titania. These powders have been compared with similar powders prepared by mixing the ingredients mechanically in a ball mill either in dry condition or in alcohol. The heterocoagulated powder shows a much better dispersion of CNT as observed from the X-ray dot maps. While all powders have shown reasonably good flowability as measured using a standard powder feeder, the heterocoagulated powder has shown a superior flow characteristic.