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Ceramics are nonetheless used in a huge range of advanced applications. Generally defined as non-metallic and inorganic materials, they stop spacecraft from disintegrating and burning across the sky as they re-enter the atmosphere, replace ageing and damaged bones and one variant protects soldiers in bulletproof vests.
“I think the biggest issue with the ceramics industry is ceramics largely go unseen in day-to-day parts and objects,” says Dr Tom Wasley, a senior research engineer in additive manufacturing at the Manufacturing Technology Centre. “They are treated like a last resort material, which means that you very rarely know they are there, but without ceramics almost nothing would function.”
Wasley is discussing additive manufacturing (AM) of ceramics amid the whirr of 3D printers at the TCT Show in Birmingham. But despite the materials’ ubiquity in everything from microwaves to nuclear reactors, the machines are not extruding or depositing ceramics. Instead, their incremental progress yields structures made of polymer resins, or – more rarely – metal.
Immature technology
A 2017 report by industry analyst SmarTech Publishing said 3D printing of ceramics could leap from a $160m market to over $3bn in 10 years, but several factors are preventing it from reaching its full potential in a “huge” number of sectors, says Wasley. “The technology is relatively immature, the supply chain is also relatively immature, so you pay high cost for materials from OEMs and… there’s a limited range.”
That needs to change for the market to progress in a similar fashion to polymer resin printing, says Wasley. After bursting into the public consciousness several years ago, 3D-printed plastics are now having a huge impact in diverse areas such as aerospace, biomedical engineering and animated films.
“If you look at companies that were in AM very early, back in the 1990s, it was very much a case of ‘You buy our materials for our machines,’ and there wasn’t a lot of other availability. Obviously in the last 10 years we’ve seen the supply chain grow massively, with companies specialising in polymer resin materials for stereolithography, or powder metals, and I think the same thing will happen with ceramics.”
He adds: “What we’re trying to encourage is that that happens earlier… [slow diversification] has proven to be a bit of a limitation in the metals market. So what I’m trying to push is that we learn our lessons from metals, which are probably 10 years ahead of where ceramics are, so that we can get ceramics to that position more rapidly.”
Altering post-printing treatments such as sintering – heating a material to strengthen and compact it – and debinding, where binding agents are removed from between ceramic layers, can lead to diverse and useful material properties, says Wasley. Porous printed ceramics might be useful for filters or catalytic parts, while hard-wearing and dense structures are useful in medicine.
Dodgy pottery
Radical new processes could also create more complex, useful shapes. A team at the City University of Hong Kong recently developed a new kind of ceramic ‘ink’, a mixture of polymers and ceramic nanoparticles. Printed structures using the ink are soft, allowing them to be stretched and folded.
With precursors printed on to the structures, they ‘morph’ into desired shapes over time before being heated and solidified, creating so-called '4D-printed' ceramics. “With the versatile shape-morphing capability of the printed ceramic precursors, its application can be huge,” said mechanical engineer Professor Lu Jian. The lead researcher said the innovation could be particularly useful for aerospace heat shields or electromagnetic transmitters.
As new processes develop and supply chains mature, Dr Wasley says many more applications for 3D-printed ceramics will emerge. “The more we see awareness of the technology increase, the more these applications will come out of the woodwork.”
One day soon, then, complex 3D-printed structures might always come to mind before dodgy pottery.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.