Bulk ceramic nanocomposites, having one of the phases in the nanosized dimensions, can be classified into two broad categories, viz. Â‘nano-particulate reinforced ceramic compositesÂ’ and Â‘nano-fibre reinforced ceramic compositesÂ’. Idealized microstructural features for the former consists of nanoparticles of a second ceramic phase dispersed within the ceramic matrix (possessing coarser grains) (Figure 1a), while for the later, fibres possessing diameters in the nanosized regime (typically carbon nanotubes; CNT) are present within the ceramic matrix. Typically powder metallurgical route, which involves physical mixing of the matrix and reinforcement (nano) powders/(nano)fibres followed by sintering, is adopted for development of such bulk ceramic nanocomposites. However, more recently few other routes, such as solid-state precipitation or infiltration of nano-sized pores of bulk mesoporous ceramics have been explored. Irrespective of the processing route adopted, it has been routinely demonstrated that the nano-reinforcements contribute towards improving the mechanical, thermo-mechanical, tribological and physical (especially for CNT-reinforced ceramics) properties. However, for inching closer towards achieving the full potency of such reinforcements and for improving the feasibility of Â‘commercial takeupÂ’ of such high performance nanomaterials necessitates identification of the pertaining issues and taking-up further research to address them. Accordingly, some of the on-going works in our research group at IIT Bombay are focussed on achieving both the objectives by trying to identify and addressing such issues on a finer scale for both the classes of ceramic nanocomposites. The objective of this commentary is primarily to bring to light some of these major unresolved issues, which are related to the processing of the ceramic nanocomposites via the usual powder metallurgical route.
Last date updated on June, 2014