3D-printed super strong ceramics in the offing

Los Angeles :Researchers have developed a new 3D printing technique to create flexible ceramic structures of high strength with low porosity and cracking.

The technique – which leverages polymer chemistry and UV light in some novel ways – could find use in high-temperature settings at scales ranging from microelectromechanical devices to jet engines, researchers said.

Three-dimensional printing of ceramics holds some big potential advantages, owing to its ability to create complex shapes that are difficult to create using conventional methods.

The most common additive-manufacturing techniques for ceramics, involving layer-by-layer, selective curing of powder-based precursors, have been painfully slow, and have created products with unacceptably high porosity and a tendency towards strength-reducing cracks.

Looking for a better, faster approach, researchers at the HRL Laboratories in California built on previous developments in two areas: ceramic polymer chemistry and the details of UV light control in the additive-manufacturing process.

The researchers tweaked the chemistry of inorganic preceramic monomers, which have been used for decades to synthesise ceramic fibres and similar materials, to make the monomers build into polymer chains when exposed to UV light.

Next, they experimented with several approaches to spatial control of additive manufacturing using a resin of these UV-curable preceramic monomers.

In one particularly interesting technique, the monomer additives were selected so that they not only facilitate polymerisation, but create a change in the index of refraction of the resin as it polymerises – such that the UV light is internally reflected and concentrated within the ceramic polymer as it is built.

In essence, the growing ceramic chain becomes a waveguide that facilitates and controls further polymerisation by collimated UV light at the tip.

A final pyrolysis step at the end, which involves heating the printed polymer to 1,000 degrees Celsius in inert argon gas, drives off any remaining volatiles, leaving behind a pure ceramic part.

The result of the process is flexible, strong 3D printed components consisting of cross-linked ceramic networks.

Electron microscopy confirmed that the ceramic material contains little or no porosity and cracking.

Other tests suggest that the material can withstand temperatures of some 1,400 degrees Celsius without degradation and shows mechanical strength “10 times as high as commercially available ceramic foams of similar density.”