Kameoka Lab. | Institute of Multidisciplinary Research for Advanced Materials Tohoku University

About Kameoka Lab.

Creation of catalytic materials in terms of metallurgy and exploration of alloys with novel structures

We focus on creation of catalytic materials with excellent properties in terms of metallurgy and exploration of alloys with novel structures.

fields・keyword
metallurgy for catalytic materials / microstructure control / electronic structure control / intermetallics / quasicrystals / hypermaterials

Design and fabrication of bulk-type metallic catalysis materials

Our target catalytic materials are not conventional catalysts such as nanoparticles but bulk-type metallic catalysts. Compared to metal and/or alloy nanoparticles catalyst, bulk-type metals and alloys as catalysts have not been fully investigated so far. In addition, the advantage of bulk-type metallic materials is that they can clarify various thermodynamic parameters that are the basis of metallurgy can be greatly reflected in preparation and microstructure control of alloys.
Research on precious metals alternative alloys

It is well known that precious metals (e.g., Pt, Pd, Rh etc.) show high catalytic performance in various reaction systems. Recently, precious metal–free and development of precious metal alternative alloy catalysts have become the most important issues. We are developing precious metals alternative catalytic materials in terms of electronic structures and microstructural control of alloys.

Creation of novel catalytic materials using intermetallic compounds and their microstructure control

Recently, intermetallic compounds (IMCs) are attracting attention as new metallic catalysis materials because they are a well-defined alloy group in which each constituent metal atom is regularly arranged at a specific site in the crystal lattice with a stoichiometric composition. There are many types, and we design and prepare catalytic materials with unique properties using IMCs with excellent catalytic functions.
Metallurgy for structured metallic catalysts

Foil-type metallic catalysts have high processability, thermal conductivity and material mobility. Therefore, it is possible that their catalytic functions by incorporating structural control and microstructure control unique to bulk-type metallic materials that cannot be realized with conventional nanoparticle-based metallic catalysts. We are investigating the foil-type metallic materials with unique catalytic properties that makes full use of microstructure control and processing processes.

Fabrication methods, structure analysis and physical property assessments of quasicrystalline alloys

Quasicrystals and related intermetallic compounds present a uique part of our research topics. Apart from basic studies such as the exploration of new quasicrystalline alloys, structure analysis of quasicrystalline approximants, elucidation of structure transformation mechanisms and mathematics of quasicrystalline structures, more application oriented studies to develop new metal catalysts using quasicrystals as precursors or quasicrystal reinforced Mg alloys.

Fabrication methods, structure analysis and physical property assessments of quasicrystalline alloys

"Quasicrystals" are solid state materials that exhibit both long-range quasiperiodic order and non-crystallographic (i.e., crystallographically forbidden) rotational symmetries. They are known to form mainly in metallic alloy systems, but have also been found in other systems such as soft-matter, nano-particle aggregates and crytalline-surface adlayers.

Among the most frequently seen are icosahedral, decagonal and dodecagonal quasicrystals named after the respective point symmetries.

Although periodicity is absent in any quasicrystal, there often exist in its compositional vicinity crystalline phases so-called "approximants", in which the local building units of the quasicrystal are arranged periodically.
Quasicrsytal geometry and structure stabilization

We combine mathematical studies on quasiperiodic tilings and crystallographic analysis of related compounds to elucidate the structure of real quasicrsytalline compounds, whereby the acquired knowledge can be applied to understand the origin of the structure stability and unique physical properties.

Quasicrsytal geometry and structure stabilization

A quasicrystal and related approximants generally have markedly complex atomic structures.

In fact, their structures allow a unified description in which both the structures are represented as different cuts through a given "hyper-crystal", namely a hypothetical periodic structure defined in a higher-dimensional space (called the hyperspace). This is why researchers recently call them "hypermaterials".

Whereas the higher-dimensional crystallography (developed since 1990s) serves as a proper language to describe their symmetries, the theory of quasiperiodic tiling plays an important role in describing atomic arrangement.

We have recently been focusing on the structure of thermodynamically stable icosahedral quasicrsytals and related approximants in alminium-transition metal alloy systems. For instance, we used single-crystal X-ray diffraction data to perform a structure analysis of a novel high-order approximant in the Al-Pd-Cr-Fe system. It turned out that that the atomic structure is well described using a three-dimensional tiling decorated with atomic clusters. By generalizing this knowledge we have proposed a new framework applicable to more general approximants and also quasicrystals.

Apart from this particular example, several other structural investigations are also under way, aiming to gain essential insight into the structural complexity for understanding the structure stability and physical properties.