Ceramics that hold their own in ‘stressful’ situations
Ceramics and metals have been used by humans for thousands of years to make objects from vases and tools to structural components. While we typically think of metals as being more durable and ceramics more fragile, ceramic materials are very hard and strong in the face of compression. However, they are brittle, meaning that they are minimally deformable and so can break quite suddenly. Metals, on the other hand, are malleable and ductile – they can be pressed or pulled into various shapes without breaking. The EU-funded SISCERA project has levelled the playing field, bringing the world’s first ceramics with predictable transformation-induced plasticity to market.
Knowing when enough is enough
Critical defects randomly distributed in ceramics during manufacturing result in brittleness, causing failures. The benefits of using a ceramic are often counterbalanced by the need to reduce the presence of defects via expensive and time-consuming manufacturing and testing procedures. With SISCERA’s ceramic composites, failure is minimised and much more predictable. SISCERA coordinator Nicolas Courtois of Anthogyr explains: “Our ceramic composites are unique because they can be deformed significantly before failure at a defined and tuneable stress level. In addition, the failure is unrelated to defects, making conventional design and processing methods appropriate, and thus, simplifying adoption for designers, while increasing the ceramic’s added value. Taken together, our innovative ceramic composites combine the benefits of metals with the advantages of ceramics, such as chemical stability, inertness and wear and abrasion resistance.” This means they can be an attractive alternative to metals for many engineering applications.
From bones to industry and consumer goods
Jérôme Chevalier, Deputy Director of Research at INSA Lyon in charge of Health and Bio-engineering, states: “Early in the project, we were forced to re-enter development to meet new design expectations. Thanks to this initial challenge, we delivered a material ‘portfolio’ that can be tailored to the application rather than the single solution we planned at the start.” The primary market targeted by the SISCERA team was that of biomedical implants, particularly where bone ingrowth (osseointegration) is desired, such as with dental and joint implants. The team followed a rational ‘material-by-design’ approach to address the specific requirements of a dental implant, such as strength, toughness, stability and surface modification. The ceramics demonstrate enhanced osseointegration. Results showed that the combination of material and surface modification outperforms the current titanium implant surfaces, allowing implants to establish stronger adhesion to bone faster – twice as strong at four weeks. The dental implant has now entered the preclinical validation phase. According to Courtois and Chevalier, there are plenty of uses yet to be discovered for these unique materials. “We showed at the very end of the project that the plastic transformation was reversible. In this sense, we have a ceramic shape-memory material,” they add. One ceramic composite is already available for industrial use and a potential large-scale application in consumer goods is currently being tested. These revolutionary composite ceramics that deform significantly without breaking will be a game changer in applications from biomedicine to engineering.
Keywords
SISCERA, ceramic, metals, composites, dental implant, osseointegration, brittleness, deformable, shape-memory, plasticity
