Ceramic nanopowders could also be used in parts for medical technology, micro-reactors and micro-sensors.

The European researchers supported by funding of the ‘Cutting tools and miniaturised parts with complex geometry based on nano powders’ (Nanoceram) project started by developing plasma chemical technology for nanopowder manufacture and new technologies for surface modifications of the powders for use in standard gel casting, injection moulding and pressing. They also wanted to develop sintering methods for producing dense materials with nano-sized microstructure.

In particular, researchers focused on the use of silicon nitride (Si3N4) for wood cutting tools and yttria (Y)-stabilised zirconium oxide (ZrO2) for parts in medical technology and micro-devices. Investigators successfully produced four batches of plasma-processed Si3N4 powders of required quality and quantity. They also carried out surface modifications of the nano-sized powders to achieve good particle dispersion and high solid loads.

A gel casting procedure was developed for manufacture of parts from pure Si3N4 plasma powder or mixtures of it. The manufactured plates had good bending strength, hardness and fracture toughness.

Parts shaped from Si3N4 plasma powder or mixtures of it via gel casting, metal powder injection moulding (MPIM) and cold isostatic pressing (CIP) were then sintered to optimise sintering regimes.

Milling cutters produced from Si3N4 were tested against hard metal cutters. Although the ceramic cutters produced flakes or fragments, field emission scanning electron microscopy of the edges detected no damage after grinding.