29 Sep

Direct measurement of individual phonon lifetimes in the clathrate compound Ba7.81Ge40.67Au5.33

Understanding how the heat propagates in a material is a key issue in many different fields. For application such as nano and micro technology, heat dissipation is a key element. For thermoelectric materials, which can transform heat into electricity, researchers design new materials and try to reduce as much as possible their thermal conductivity, a key parameter in the efficiency equation in these materials. However an understanding of the deta... [...]

26 Sep

Building 2D quasicrystals from 5-fold symmetric corannulene molecules

A comparative study has been performed on the adsorption of structurally related but stereochemically different C60 and C20H10 molecules on the 5-fold surface of the icosahedral i-Ag-In-Yb quasicrystal. Both molecules have similar lateral dimensions and have the same pentagonal carbon ring surrounded by five phenyls. However, while C60 molecules have 2-, 3- and 5-fold rotational symmetries, C20H10 only have C5v symmetry. Therefore both organic mo... [...]

22 Jul

Atomic structure and phason modes of the Sc–Zn icosahedral quasicrystal

Tsunetomo Yamada, Hiroyuki Takakura, Holger Euchner, Cesar Pay Gómez, Alexei Bosak, Pierre Fertey and Marc de Boissieu    IUCrJ (2016) 3, 247-258 (link) The detailed atomic structure of the binary icosahedral i-ScZn7.33 quasicrystal has been investigated by means of high-resolution synchrotron single-crystal X-ray diffraction and absolute scale measurements of diffuse scattering. The structure is isomorphous to the i-C... [...]

27 Nov

Preparation, Crystal Structure and Physical Properties of the Superconducting Cage Compound Ba3Ge16Ir4

The cage compound Ba3Ge16Ir4 crystallizes with the Ba3Ge16Rh4 type of crystal structure, which represents a hierarchical derivative of the BaAl4 type. The crystal structure [Pearson symbol tI46, space group I4/mmm; a = 6.5312(2) Å, c = 22.2845(6) Å] was refined from single-crystal X-ray diffraction data. The phase was obtained after 10 d at 910 °C with small impurities of  clathrate-I, BaGe7Ir2 and α-Ge remaining at the grain boundaries.... [...]

25 Aug

Real space crystallography of a complex metallic alloy: HAADF STEM of o-Al4(Cr,Fe)

 Roberto Gaspari (1a,2), Rolf Erni (3), Yadira Arroyo (3), Magdalena Parlinska-Wojtan (3), Julia Dshemuchadse (4), Carlo A. Pignedoli (1a), Daniele Passerone (1a), Patrik Schmutz (1b), Alessandra Beni (1b,*) (1a) nanotech@surfaces and (1b) Joining Technology and Corrosion Laboratories, Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, Duebendorf, 8600, Switzerland. (2) D3- Computation, It... [...]

25 Aug

Hard X –Ray Photoelectron Spectroscopy (HAXPES) characterisation of electrochemical passivation oxide layers on Al-Cr-Fe Complex Metallic Alloys (CMA)

Alessandra Beni (1,*), Noémie Ott (1), Magdalena Pawelkiewicz (1), Micheline Wardé (2), Kirsty Young (3), Birgitta Bauer (4), Parasmani Rajput (5), Blanka Detlefs (5), Jörg Zegenhagen (5), Ronan McGrath (3), Marie-Geneviève Barthés-Labrousse (2), Lars P. H. Jeurgens (1), Patrik Schmutz (1,*) (1) Empa, Swiss Federal Laboratories for Materials Science & Technology, Ueberlandstrasse 129, 8600, Duebendorf, Switzerland. (2) ICMMO, CNRS U... [...]

03 Apr

Self-Organized Molecular Films With Long-Range Quasiperiodic Order

Vincent Fournée†*, Émilie Gaudry†, Julian Ledieu†, Marie-Cécile de Weerd†, Dongmei Wu‡, Thomas Lograsso‡ † Institut Jean Lamour, UMR 7198 CNRS-Université de Lorraine, Parc de Saurupt, 54042 Nancy Cedex, France. ‡ The Ames Laboratory, Iowa State University, Ames IA 50011, USA. * vincent.fournee@univ-lorraine.fr DOI link: http://pubs.acs.org/doi/abs/10.1021/nn500234j Self-organized molecular films with long-... [...]

06 Jan

Surface-driven, one-step chemical vapor deposition of gamma-Al4Cu9 complex metallic alloy film

A paradigm for the one-step formation of complex intermetallic coatings by chemical vapor deposition has recently been published by CNRS in Toulouse. The work genuinely addresses the challenge of depositing an intermetallic coating with comparable contents of Cu and Al. Depending on processing conditions, a pure  gamma-Al4Cu9 and multi-phaseAl-Cu films are grown with wetting properties of the former being similar to its bulk counterpart. The... [...]

21 Nov

Templated Three Dimensional Growth of Quasicrystalline Pb

An international collaboration led by the University of Liverpool has discovered an exotic film of the element lead (Pb), in which the atoms are arranged in pentagonal and decagonal structures rather than in the usual cubic fashion.  Quasicrystals, the discovery of which led to the award of the 2011 Nobel Prize in Chemistry to Dan Shechtman of the Technion Institute, Israel, were first observed in alloyed systems comprising several elements.... [...]

17 Apr

Electrodeposition of thermoelectric materials

PhD-research report Hai P. Nguyen   Organizations: • KU Leuven, Department of Metallurgy and Materials Engineering (MTM), Heverlee, Belgium • imec / Holst centre, Eindhoven, The Netherlands   Abstract Thermoelectric devices can directly convert thermal energy to electricity or pump heat up a temperature gradient. They are increasingly used as low-power power generators or coolers. Bismuth telluride (Bi2Te3) and antimony telluri... [...]

12 Mar


PHONONIC FILTER EFFECT IN THE BA-GE-NI CLATHRATE SYSTEM  Intermetallic clathrates are so called cage compounds. Their structure can be described by a host framework, consisting of large cages, which enclose heavy guest atoms (see Fig. 1). While clathrates exhibit a crystal-like electrical conductivity, their thermal conductivity is strongly reduced making them promising materials for thermoelectric application. So far, the microscopic me... [...]

28 Nov

The quasicrystal approximant Zn6Sc: a surprising dynamical flexibility

The quasicrystal approximant Zn6Sc: a surprising dynamical flexibility Quasiscrystals are materials in which the atoms are arranged in such a manner that long range order is maintained, however, without periodicity, and thus in contrast to conventional crystals. To better understand the structure and the way atoms move inside a quasicrystal, an international team of European and Japanese scientists (European C-MAC network, www.eucmac.eu)... [...]

08 Oct

Iron cuts at precious metal

An iron-aluminium compound could replace a palladium catalyst, reducing the cost of plastic production Chemists don't like precious metals – at least not when they need the expensive materials as catalysts to accelerate reactions or guide them in a particular direction. And this is often the case, as in an important step in the production of polyethylene, a substance that makes plastic bags light, flexible and stable. However, an international... [...]

09 May

Dynamic Structure Mediated by Graphitelike Al Nets on the Al2Cu (001) Surface

A detailed study of the (001) surface of the Al2Cu crystal using both experimental and ab initio computational methods is presented in this work. The combination of both approaches gives many arguments to match the surface plane with a bulk truncated surface model terminated by incomplete Al planes. The missing rows of Al atoms lead to a 2 root2 x root2 R 45° surface reconstruction with two domains rotated by 90 from each other. Ab initio calcu... [...]

06 Mar

Janus-headed ZnPd – CO or CO2 from methanol

Methanol steam reforming (MSR, CH3OH + H2O à 3H2 + CO2) is considered as one of the most promising routes to produce high purity hydrogen for mobile fuel cell applications. However, the main drawback is the formation of CO as a byproduct, which has to be kept at a level of about 10 ppm to prevent poisoning of fuel cell catalysts. MSR on single-phase samples of the intermetallic compound ZnPd, all possessing the CuAu type of crystal structure, p... [...]

15 Jun

Anomalous vibration dynamics in Zn11Mg2

We have extensively studied Mg2Zn11, a compound which shows interesting vibrational properties and exhibits intermediate structural complexity in between the Laves phase MgZn2 and alloys of higher complexity or quasicrystals . The structure can be described as a cubic packing of a triacontahedron whose center is partially occupied by a Zn atom. This partially occupied site turned out to play a major role in understanding the lattice dynamics. Th... [...]

16 Feb

Nanodomains due to Phason Defects at a Quasicrystal Surface

Among the three coexisting types of terraces found on the twofold surface of the d-Al-Cu-Co quasicrystal, nanodomains are essentially observed on the transition-metal rich ones, with a coherent interface boundary. Both clean surface and Ag growth analyses, demonstrate that nanodomain surfaces are structurally identical to one of the two other terraces, which contains 85 at. % Al. We provide evidence that the nanodomains are a manifestatio... [...]