Quasicrystals of synthetic fluoromagnesian smectite (FMS) in dodecyltrimethylammonium chloride (DTAC) solutions were investigated as a function of the DTAC concentration by wet type X-ray diffraction (XRD) ζ potential measurements, and dispersion and coagulation (DC) tests. The FMS had an electronegative potential and it was dispersed randomly in an aqueous suspension without DTAC. When the DTAC concentration was 0.002 mol/dm3, FMS tactoids started to develop a structure in which the layer thickness was 1.85 nm. At the isoelectric point, the DTAC concentration was 0.012 mol/dm3 and the FMS tactoid formed a regular stacked structure with a 2.25 nm layer thickness. As the ζ potential of FMS changed from negative to positive, the DC test and XRD measurement showed that the FMS association gradually changed from coagulation to dispersion, which indicates that the formation of the bilayer of surfactants on the surface of FMS produces a repulsion between DTA+ adsorbed on the silicate layer of the FMS surfaces. When the equilibrium concentration of DTAC in solution exceeded the critical micelle concentration (CMC), the ζ potential of FMS became greater than the previous values. The XRD analysis of this suspension showed that there were two kinds of rational FMS stackings; one has a layer thickness of 3.20 nm, and the other has a layer thickness of 5.45 nm due to an interstratified structure composed of 3.20 and 2.25 nm layers. The interstratified structure was confirmed by the calculated XRD profiles.

Quasicrystalline alloys and their composites have been extensively studied due to their complex atomic structures, mechanical properties, and their unique tribological and thermal behaviors. However, technological applications of these materials have not yet come of age and still require additional developments. In this review, we discuss the recent advances that have been made in the last years toward optimizing fabrication processes and properties of Al-matrix composites reinforced with quasicrystals. We discuss in detail the high-strength rapid-solidified nanoquasicrystalline composites, the challenges involved in their manufacturing processes and their properties. We also bring the latest findings on the fabrication of Al-matrix composites reinforced with quasicrystals by powder metallurgy and by conventional metallurgical processes. We show that substantial developments were made over the last decade and discuss possible future studies that may result from these recent findings.

The Ti-Zr-Ni quasicrystal alloys have prospected to be one of the promising materials for hydrogen storage. This is because this type of quasicrystal contains 140 interstitial sites (T-sites) constituted in the Bergman Cluster that could accommodate hydrogen. The number of available sites is far greater than the number found in regular crystals, therefore the improvement of hydrogen storage capacity could be expected. For this study, we focus on the effect of substitution of Cr, in place of Ni in Ti-Zr-Ni amorphous and quasicrystal alloys. The studied samples are synthesized by the combination of mechanical alloying and sintering process. The subsequent measurements of electrochemical hydrogenation and dehydrogenation are carried out by a three-electrode cell at room temperature. The studied samples are structurally characterized by X-ray diffraction and their morphology is analyzed by scanning electron microscope and transmission electron microscope. The influence of the 4th substituted element on the possibility of a new-formed Cr quasicrystalline phase and the potential improvement of hydrogenation and dehydrogenation kinetics for both amorphous and quasicrystalline phase is evaluated. Our measurements showed the maximum discharge capacity achieved by Ti45Zr38Ni7Cr10 amorphous and Ti45Zr38Ni12Cr5 i-phase electrodes at a current density of 15 mA·g-1 to be 9.8 mAh·g-1and 55.2 mAh·g-1 respectively. The maximum estimated H/M value for the Ti45Zr38Ni12Cr5 i-phase electrode reached 1.36. These results are encouraging and show the merit of the usage of quasicrystals as hydrogen storage materials.

This paper reports the results of preparing alloy nanoparticles by mechanical grinding followed by filtration to sort the particles according to size. Although the long-term goal of this work is to prepare icosahedral quasicrystalline nanoparticles, the alloy used in this study is of Al65Cu25Fe15 composition and multi phases, under the assumption that the established procedure is applicable to future quasicrystalline nanoparticle fabrication. The obtained particle size and elemental information were investigated using scanning electron microscopy and energy dispersive x-ray spectroscopy. Problems with filter fragment fall-out and salt contamination were encountered and procedures to address the problems have been suggested and tested. The study is successful in obtaining alloy particles with reduced sizes.

Positron annihilation spectroscopy and differential scanning calorimetry were used to evaluate the changes of the atomic configurations in Zr-based metallic glasses (MGs) due to alloying and plastic deformation. The correlation between the atomic configurations of MGs and the amorphous-to-icosahedral phase transition due to heating was investigated. The results indicate that the free volume frozen in the as-cast Zr60Al15Ni25, Zr65Al7.5Ni10Cu17.5, and Zr65Al7.5Ni10Cu17.5Ag5 MGs substantially decreases in sequence. More excess free volume is introduced in Zr65Al7.5Ni10Cu17.5Ag5 MG due to cold rolling and milling. The annihilation of free volume due to alloying considerably stabilizes the icosahedral structure of MGs, which enhances the nucleation and growth of quasicrystals upon heating. However, the nucleation and growth of quasicrystals are considerably suppressed in Zr65Al7.5Ni10Cu17.5Ag5 MG due to cold rolling and milling, during which the more introduced excess free volume results in substantial destruction of short-range order with 5-fold symmetry. The present work further provides direct evidence for the prevalence of icosahedral short-range order in MGs.

Ti-based quasicrystals are well known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. This fact is due to that TiZrNi contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemical affinity with hydrogen. TiZrNi quasicrystal absorbs hydrogen up to host metal ratio (H/M) value near to 2.0. The disadvantage is due to the low equilibrium pressure. To solve this problem, we substituted Ti with a small amount of vanadium (V), with the nominal composition Ti45−x VxZr38Ni17 (x = 5, 10, 15) and synthesized by mechanical alloying. The subsequent annealing in vacuum conditions converted the amorphous into an icosahedral quasicrystal (I-phase) with face-centered cubic (FCC) Ti2Ni-type crystal. As the results, we investigated the discharge capacity for both amorphous and quasicrystal electrodes using three electrodes system (working, reference and counter electrodes) at room temperature. The highest discharge capacities obtained were 81.45 mAh/g recorded for amorphous electrode and 318.4 mAh/g for quasicrystal whose compositions is Ti35V10Zr38Ni17 at discharge current density of 15 mA/g. X-ray diffraction measurement was performed to provide the structural information on materials before and after hydrogenation. Microstructures of the materials were studied using an electron scanning microscope and the chemical compositions were confirmed using an EDX-analysis.

Thermoelectric properties of segmented nanowires and nanobelts are studied by means of the Kubo-Greenwood formula and a real-space renormalization plus convolution method. The tight-binding and Born models are respectively used for the calculation of electronic and lattice thermal conductivities. In particular, we investigate the thermoelectric figure of merit (ZT) of periodic and quasiperiodically segmented nanowires with two different cross sections, where the segments of the quasiperiodic one are ordered following the Fibonacci sequence. The results show an increase of ZT when the cross section area of nanowires diminishes. In addition, we present results of ZT in segmented nanobelts with an inhomogeneous cross section. For both nanowires and nanobelts, the quasiperiodicity seems to be an important enhancing factor of ZT.

Multilayered thin films of Al/Cu/Fe have been prepared by magnetron sputtering and annealed into quasicrystalline and approximant phases on Al2O3 and Si substrates, respectively. The nanomechanical and nanotribological properties, such as hardness, elastic modulus, friction, and toughness, have been measured using a triboindenter and analytical methods. The approximant phase was proved to be slightly harder than the quasicrystalline phase with a hardness of about 15.6 GPa, and with a similar elastic modulus of about 258 GPa. These values however decreased rapidly with an increasing amount of Si in the approximant. The indentation toughness of the approximant, <0.1 MPa/m½, was however inferior to that of the quasicrystals with 1.5 MPa/m½. Friction coefficients were measured in a range of 0.10–0.14 for both the quasicrystalline and approximant thin films.

In this presentation, results of our recent investigations on the role of Ga on Al site in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax metallic glass compositions will be discussed. Ga like Al is normally expected to be in trivalent state. However, it may go in monovalent state depending on other alloying elements. The rapidly solidified melt spun ribbons of above two alloys gave rise to two important conclusions. The Zr69.5Al7.5-xGaxCu12Ni11 system displayed metallic glass formation in the range of x=0 to 7.5. In this process, we have come out with a new composition of glass without Al corresponding to x=7.5. In contrast to the above, for Ce-Al(Ga) system, we have observed phase separation in glass after dilute substitution of Ga. It seems that such a phase separation in this system cannot be understood in terms of summation of enthalpy of mixing of the various possible binaries in this system. The substitution of Ga in different valence states might have created chemical pressure leading to creation of two types of distinct major clusters. The phase separation may be due to this. This has also given rise to excursion of Ce 4f-states of the alloy. This and aforesaid ‘chemical pressure’ will be corroborated based on results of binary Ce-Al system under pressure by other investigators.

Based on the Kubo-Greenwood formula, the thermoelectric effects in periodically and quasiperiodically segmented nanowires are studied by means of a real-space renormalization plus convolution method, where the electrical and lattice thermal conductivities are respectively calculated by using the tight-binding and Born models; the latter includes central and non-central interactions between nearest-neighbor atoms. The results show a significant enhancement of the thermoelectric figure-of-merit (ZT) induced by the structural disorder and/or the reduction of nanowire cross-section area. In addition, we observe a maximum ZT in both the chemical-potential and temperature spaces.

Three-dimensional (3D) morphological evolution and growth mechanisms of primary I-phase particles have been investigated in directionally solidified Al–6Mn–2.5Be (wt%) alloy at a wide range of growth rates (100–1500 μm/s). At relatively low growth rates (100–600 μm/s), the I-phase particles exhibit faceted growth with strong anisotropy, forming a hierarchical flower-like aggregate with icosahedral morphological symmetry composed of several attached irregular polyhedrons or pentagonal dodecahedrons. At higher growth rates (e.g., 1000 μm/s), the interface of the I-phases becomes unstable along the edges and corners of the pentagonal dodecahedron, thereby arousing growth perturbations. Correspondingly, a transition from faceted to nonfaceted growth occurs with increasing growth rate. Further increase of the growth rate leads to the formation of I-phase columnar dendrites' preferential growth along the 3-fold axis. The configurations of the flower-like aggregates can be adequately illustrated by a geometrical model in terms of the perfect and elongated pentagonal dodecahedrons. A growth mechanism for the flower-like aggregates has been proposed based on the clear understanding of the 3D morphological evolution of the I-phase particles.

We investigated theoretically the transmission spectra in one-dimensional photonic quasicrystals (1DPQ) made up from dielectric materials organized in accordance to a discrete varying electric permittivity profile that obeys an analogous of the quasiperiodic potential in the so-called Audry-André (AA) model, in order to modulate the refraction index. Our results show that due to the incommensurate dielectric distribution, the spectrum splits into a fractal set of pass- and forbidden-band structure. By studying the transmission spectra as a function of the modulation phase ϕ, we found boundary states lying within the gaps localized either on the left or on the right boundary of the system, characterizing the so-called topological states.

Transport properties (thermal conductivity, electrical resistivity and thermopower) of decagonal quasicrystal d-AlCoNi, and approximant phases Y-AlCoNi, o-Al13Co4, m-Al13Fe4, m-Al13(Fe,Ni)4 and T-AlMnFe have been reviewed. Among all presented alloys the stacking direction (periodic for decagonal quasicrystals) is the most conductive one for the charge and heat transport, and the in/out-of-plane anisotropy is much larger than the in-plane anisotropy. There is a strong relationship between periodicity length along stacking direction and anisotropy of transport properties in both quasicrystals and their approximants suggesting a decrease of the anisotropy with increasing number of stacking layers.

The influence of oxygen content on containerless solidification of Zr80Pt20 alloy has been studied by using conical nozzle levitation (CNL) technique. The doping level of oxygen from 41 to 5450 ppm mass oxygen (PMO) affects the undercooling of the liquid Zr80Pt20 alloy. Time-resolved synchrotron x-ray diffraction revealed that the quasicrystalline (QC) phase precipitated as a primary phase during solidification of the Zr80Pt20 alloy. The amount of the QC phase depends on the oxygen content in the alloy. This indicates that the doping level of oxygen in Zr80Pt20 alloy can be related to the metastable phase formation as well as the glass-formation ability.

Metadislocations are highly complex and pivotal defects mediating plastic deformation in complex metallic alloys. Here, we review recent results on the structure of metadislocations in the phases T-Al-Mn-Pd, T-Al-Mn-Fe and o-Al13Co4. In these materials, metadislocation motion is of particular interest as it takes place by pure glide in contrast to most other complex metallic alloys. Recently, novel metadislocations were found in the T-phase [1]. They have Burgers vectors ${\rm{\vec b}} = \pm \tau ^{ - n} c\left( {\matrix{ 0 & 0 & 1 \cr } } \right)$ (n = 2, 3, 4) and are associated to two, four and six planar defects, respectively. The type of planar defect depends on the deformation geometry. Metadislocation glide creates (1 0 0) stacking faults and climb creates (0 0 1) phason planes. Metadislocation glide was observed in the o-Al13Co4 phase, as well [2]. The close structural relation of metadislocations in the phases T-Al-Mn-Pd, T-Al-Mn-Fe, Al13Co4 and ε6-Al-Pd-Mn is discussed.

In this paper, we report new phase of crystalline silicon, quasicrystalline silicon thin-film on glass substrate. The surface topography of these films reveal simultaneous existence of sixfold and fivefold symmetry. We found an array of quasi-unit cell in 2-D that formed quasicrystalline solid. This is first time demonstration of quasicrystalline for single element, silicon (Si). Raman spectra suggests that we found crystalline silicon structure on glass substrate that is not single-crystal silicon (c-Si) but very close to c-Si.

Complex Metallic Alloys (CMAs) are metallic solids of high structural complexity, consisting of large numbers of atoms in their unit cells. Consequences of this structural complexity are manifold and give rise to a variety of exciting physical properties. The impact that such structural complexity may have on the lattice dynamics will be discussed. The surprising dynamical flexibility of Tsai-type clusters with the symmetry breaking central tetrahedron will be addressed for Zn6Sc, while in the Ba-Ge-Ni clathrate system the dynamics of encaged Ba guest atoms in the surrounding Ge-Ni host framework is analysed with respect to the experimentally evidenced strong reduction of lattice thermal conductivity. For both systems experimental results from neutron scattering are analyzed and interpreted on atomistic scale by means of ab initio and molecular dynamics simulations, resulting in a picture with the respective structural building blocks as the origin of the peculiarities in the dynamics.

Strategies are described for modeling the kinetics of non-equilibrium film growth during deposition of metals on quasicrystalline substrates. We review previous atomistic-level lattice-gas modeling and Kinetic Monte Carlo simulation for pseudomorphic (or commensurate) submonolayer growth based on a “disordered or irregular bond-network” (DBN) of neighboring adsorption sites. We describe extensions to treat strain effects and multilayer growth, and discuss a type of commensurate-incommensurate transition expected around 2-3 layers. We also describe a coarse-grained “step dynamics” modeling which tracks the dynamics of island edges in each layer rather than individual atoms. Step dynamics models can also include key aspects of the physics such as layer-dependent energetics, including quantum size effects, and strain effects.

The structure of the (100) surface of the orthorhombic Al13Co4quasicrystalline approximant is described based on a combined scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density functional theory (DFT) study. We discuss the interplay between the surface structure and the cluster substructure of this approximant as well as possible off-stoichiometry effects that could explain the discrepancies found in the literature on possible surface models.

Based on X-ray photoelectron spectroscopy, Gd5Ge4(010) does not show evidence of surface segregation. Scanning tunneling microscopy reveals two types of terraces which alternate laterally on the surface. From the step heights, these two surface terminations are assigned as dense, Gd-pure layers in the bulk structure. There is evidence of reconstruction on one type of terrace.