[Image above] Researchers at Los Alamos National Lab have discovered some interesting secrets lying at the interfaces within nanocomposite oxide ceramics—secrets that help open the door to better batteries, fuel cells, nuclear materials, and more. Credit: LANL
Sometimes, one just isn’t enough.
Although many ceramic materials are quite amazing on their own, certain applications require just that special mix of properties that one material alone cannot provide.
But mixing several ceramic materials together can yield a composite with unique combinations of properties that move beyond each individual material’s contribution. Nanocomposite oxide ceramics are one such example—these interesting mashups of oxide materials often have novel properties due to the interfaces between the different materials they contain.
Despite the boom of research into these materials—which could find use in batteries, fuel cells, radiation-tolerant materials, electronics, and more—little is known about how nanocomposite components atomically say hello to one another at their interfaces.
Researchers at Los Alamos National Lab are trying to change that. “The interfaces separating the different crystalline regions determine the transport, electrical, and radiation properties of the material as a whole,” says LANL researcher Pratik Dholabhai in an LANL press release. “It is in the chemical makeup of these interfaces where we can improve features such as tolerance against radiation damage and fast ion conduction.”
Dholabhai, along with ACerS members Ghanshyam Pilania and Blas Uberuaga and some additional LANL colleagues, recently published the results of their foray into the molecular happenings at oxide nanocomposite interfaces in Nature Communications.
The researchers relied on simulation modeling to get their results. In the paper, they explain why: “…As this information is not easily accessible experimentally due to buried interfaces and metastable heterostructures encountered during synthesis, theoretical frameworks providing insight into the structure and stability of nanocomposite oxides are valuable for designing next generation oxide-based materials.”
So the team busted out some pretty sophisticated simulations, giving them the ability to model where each atom was located in a nanocomposite of SrTiO3 and MgO. With these high-res models, the scientists then could predict how molecules and defects in the interface would affect the properties of the nanocomposite as a whole.
In the model, SrTiO3 was built like a cake with alternating layers of SrO and TiO2, according to the release.
The team’s calculations show that depending on which layer—SrO or TiO2—is in contact with the other material (here, MgO), the entire nanocomposite will have different functional properties.
Because the molecules within each layer of material don’t line up perfectly, those molecular imperfections create dislocation networks—so each material creates a different dislocation network, which directly influences the composite’s properties.
This means that characterization of a material is crucial to be able to predict and understand how a composite material will behave. And understanding what affects the functional properties opens the possibility of tailoring materials’ properties by tweaking these parameters.
“We believe that this discovery, that the interface structure is sensitive to the chemistry of the interface, will open the door for new research directions in oxide nanocomposites,” senior author Blas Uberuaga says in the press release.
The paper is “Termination chemistry-driven dislocation structure at SrTiO3/MgO heterointerfaces” (DOI: 10.1038/ncomms6043).