Combining nanosized elementary building blocks of soft and hard matter to create strong, damage resistant materials

Nanoarchitected composites and hybrid materials are promising candidates for the next generation of multifunctional materials. The combination of nanosized elementary building blocks and their long-range order arrangement in a superlattice lead to nanocomposites with applications in areas such as optoelectronics, magnetics and batteries. What still needs to be understood and optimized is the mechanical behavior of these kinds of materials.

Bor et al. demonstrate an approach to combine soft matter consisting of oleic acid or oleyl phosphate with hard matter such as iron oxide to produce strong materials with a better-than-expected damage resistance.

“We showed, for the first time, that despite the crosslinking of the organic molecules at 325 degrees Celsius, which stiffens and strengthens the nanocomposite by roughly a factor of 10, the oleic acid-based nanocomposites behave almost a factor of 3 stiffer under tension compared to compression,” said co-author Gerold Schneider.

The researchers produced strong materials at 325 degrees Celsius, very low temperatures compared to the typical sintering temperatures of ceramics beyond 1,200 degrees Celsius. This is possible if the size of the particles is in the nanometer range, because only then are the short-range surface forces able to arrange them perfectly in supercrystals, a process called self-assembly.

In addition, since the oleic acid and oleyl phosphate molecules are grafted to the solid iron oxide nanoparticles as monoatomic or biatomic layers, they feature a much stiffer behavior than in their bulk state.

“Our approach is very general in the sense that the nanoparticles can consist of any material, and thus, one can tailor thermal, electrical, magnetic or optical properties,” said Schneider. “This offers the possibility to design sustainable functional materials with very good mechanical properties.”

Source: “Constitutive and fracture behavior of ultra-strong supercrystalline nanocomposites,” by Busra Bor, Diletta Giuntini, Berta Domenech, Alexander Plunkett, Michael Kampferbeck, Tobias Vossmeyer, Horst Weller, Ingo Scheider, and Gerold A. Schneider, Applied Physics Reviews (2021). The article can be accessed at https://doi.org/10.1063/5.0056616 .