Graphene reinforced alumina tougher and more conductive than plain alumina

Graphene can reinforce ceramics, simultaneously making them conductive – at least that's what Graphenea's most recent scientific work demonstrates.

The team of researchers found that when a bit of graphene is added to the ceramic alumina, the material becomes up to 50% less likely to break under strain, a feature highly desired for many end uses of ceramics. Furthermore, the method is simple, fast, and upscalable, making it virtually ready for industrial application. The team believes that the same method could be used for reinforcing other ceramic materials, such as silicon carbide, silicon nitride, titania, and zirconia. What's more, the addition of graphene makes alumina a hundred million times more conductive to electricity.

Graphene, a single layer of carbon atoms connected in a two-dimensional “carpet”, was first made in a lab in Manchester in 2004. Six years later, its discoverers received the Nobel prize in physics for finding the material and demonstrating many of its unique properties. For example, graphene is one of the most electrically conductive materials known to mankind. It is also, given its thickness, stronger than steel, yet flexible. Graphene is transparent, making it ideally suited as a transparent conducting layer for the next generation of flexible touchpanels. Graphene is also a good conductor of heat, having been shown to guide heat away from electronic circuits.

After an initial explosion of scientific interest in graphene, time has come to explore technological and industrial applications. To this end, the European Union has selected graphene as one of its two flagship research directions, meaning that graphene research will receive a billion euros worth of funding in the next ten years. The funding rules insist on the inclusion of businesses as well as academic institutions. Graphenea is the biggest supplier of graphene on board of the flagship.

Graphene sheets are aligned along one spatial direction

Graphenea's new process, published in the Journal of the European Chemical Society, starts with graphene oxide, a commercially-available bottled graphene solution. After mixing with aluminium oxide (alumina), a process known as spark plasma sintering (SPS) is applied to homogenize the graphene/alumina mixture. SPS drives a large electrical current through the mixture, having the final product ready in minutes.

Graphenea found that the addition of as little as 0.22 percent of graphene to alumina made it 50 percent more resistant to the propagation of cracks under strain. Other mechanical properties stayed on par with untouched alumina, while electrical conductivity increased by a factor of a hundred million. Ceramics such as alumina are widely used in many industries, including aerospace, automotive, medical, thermal management, and semiconductor processing. The short propagation of cracks in ceramics is one of the most desired properties of this class of materials.

In words of Alba Centeno, the lead author of the paper, “the main advantage of graphene incorporation, at very low loadings, to an Al2O3 matrix, is that graphene makes Al2O3 electroconductive and, at the same time, improves mechanical properties and toughness. This is very important because sometimes when a second phase is incorporated in order to improve one specific property, the other properties are adversely affected.”

A single graphene sheet bridges a crack in alumina, making the entire material more resistant

Graphene sheets in Graphenea's advanced material align perpendicular to the direction of the SRS current (figure 1). The graphene sheets then act as shields, stopping any cracks that propagate along that direction. Figure 2 depicts a sheet of graphene bridging a crack, holding together the two edges of the hybrid material that try to pull apart. This novel approach could prove as a groundbreaking method of improving ceramic materials, and serve as a springboard for the mass use of graphene.

Graphenea is a leading graphene company that manufactures, produces and supplies graphene for industrial and research needs. The company has developed a synthesis and transfer process to obtain high uniformity monolayer graphene films on any substrate, over a large area. Other than high-quality large-area graphene on a variety of substrates, Graphenea markets graphene oxide and reduced graphene oxide in solution.