Quasi-ordered C60 molecular films grown on the pseudo-ten-fold (1 0 0) surface of the Al13Co4 quasicrystalline approximant

A Critical Review on Al-Co Alloys: Fabrication Routes, Microstructural Evolution and Properties

Al-Co alloys is an emerging category of metallic materials with promising properties and potential application in various demanding environments. Over the years, different manufacturing techniques have been employed to fabricate Al-Co alloys, spanning from conventional casting to rapid solidification techniques, such as melt spinning, thus leading to a variety of different microstructural features. The effect of the fabrication method on the microstructure is crucial, affecting the morphology and volume of the precipitates, the formation of supersaturated solid solutions and the development of amorphous phases. In addition, the alloy composition has an effect on the type and volume fraction of intermetallic phases formed. As a result, alloy properties are largely affected by the microstructural outcomes. This review focuses on highlighting the effect of the fabrication techniques and composition on the microstructure and properties of Al-Co alloys. Another goal is to highlight areas in the field that are not well understood. The advantages and limitations of this less common category of Al alloys are being discussed with the scope of future prospects and potential applications.

The role of three-dimensional bulk clusters in determining surface morphologies of intermetallic compounds: Quasicrystals to clathrates

Nanostructured alloy surfaces present unique physical properties and chemical reactivities that are quite different from those of the close-packed low-index surfaces. This can be beneficial for the design of new catalysts and electronic and data-storage devices. However, the growth of such surface nanostructures is not straightforward at the atomic scale. The cluster-based bulk structure of intermetallic compounds presents an original alternative to build surfaces with specific morphologies, in comparison to more traditional methods based on mechanical, chemical, or plasma treatments. It relies on their specific electronic structures-built from a network of bonds with a combination of ionic, covalent-like, and metallic characters, and also depends on the experimental conditions. In this paper, a few surface structures of cluster-based intermetallics are reviewed, with a special emphasis on quasicrystals and clathrates. We show how the intrinsic electronic properties of such compounds, as well as the surface preparation conditions, impact their surface morphologies, which can further influence the growth of atomic and molecular thin films at their surface.

Fullerene adsorption on intermetallic compounds of increasing structural complexity

Compared to elemental crystals (Al, Cu, Ag, etc.), the local atomic arrangement within Al-based complex intermetallics is usually best described by highly symmetric clusters decorating the unit cell. With the latter containing tens to several thousand atoms (or an infinite number for the case of quasicrystals), this translates to structurally complex surfaces exhibiting unique potential energy landscapes. This review will focus on the different studies reporting the adsorption of C60 molecules on such complex metallic alloy surfaces, aiming to benefit from this complexity to create exotic molecular nanostructures. First, we will recall the main adsorption mechanisms and surface phases that have been identified when fullerene adsorption is carried out on single crystal surfaces. Second, we will discuss how surfaces of increasing structural complexity impact the film properties. The presence of five-fold symmetric adsorption sites is another intrinsic property of these complex intermetallic surfaces. As will be presented in this review, this leads to specific molecular orientations to maximize substrate–adsorbate symmetry matching, hence introducing another degree of freedom to create new 2-D molecular architectures. The local electronic interactions at the adsorption site interface will also be introduced. Furthermore, the different fullerene structures formed upon adsorption on aperiodic surfaces of varying chemical composition and on Bi allotropes will be discussed. Finally, suggestions will be given for future work along with the foreseen area of interests.