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Objectives: The inhibition of the initial bacterial implant colonization by supportive antimicrobial agents such as silver is a strategy to reduce implant-related infections. A rapid and time-limited oxidative Ag ion (Ag+) release can be achieved by silver nanoparticles (AgNP) due to their high[for full text, please go to the a.m. URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019)

OA Förderung 2019 A comparative X-ray powder diffraction study on poly(N-vinyl pyrrolidone) (PVP)-stabilized palladium and gold nanoparticles and bimetallic Pd–Au nanoparticles (both types of core–shell nanostructures) was performed. The average diameter of Au and Pd nanoparticles was 5 to 6 nm. The two types of core–shell particles had a core diameter of 5 to 6 nm and an overall diameter of 7 to 8 nm, i.e. a shell thickness of 1 to 2 nm. X-ray powder diffraction on a laboratory instrument was able to distinguish between a physical mixture of gold and palladium nanoparticles and bimetallic core–shell nanoparticles. It was also possible to separate the core from the shell in both kinds of bimetallic core–shell nanoparticles due to the different domain size and because it was known which metal was in the core and which was in the shell. The spherical particles were synthesized by reduction with glucose in aqueous media. After purification by multiple centrifugation steps, the particles were characterized with respect to their structural, colloid-chemical, and spectroscopic properties, i.e. particle size, morphology, and internal elemental distribution. Dynamic light scattering (DLS), differential centrifugal sedimentation (DCS), atomic absorption spectroscopy (AAS), ultraviolet-visible spectroscopy (UV-vis), high-angle annular dark field imaging (HAADF), and energy-dispersed X-ray spectroscopy (EDX) were applied for particle characterization.

In several complex crystals, like Al13Co4, metadislocations have been shown to facilitate plastic flow at high temperature. Consistent deformation has been revealed in small scale testing down to room temperature, but until now, no high resolution studies of the underlying dislocation core structures have been conducted to confirm the presence of metadislocations where diffusion slows down towards room temperature. Here, we used microcompression and high resolution TEM to reveal that room temperature plasticity in the monoclinic Al13Co4 phase does indeed occur by motion of metadislocations and that these are closely related to those reported previously in the orthorhombic Al13Co4 phase.

International audience; The atomic and electronic structures of the 010 surface of the T-Al 3 Mn,Pd complex metallic alloy is investigated by means of low-energy electron diffraction LEED, scanning tunneling microscopy STM, x-ray and ultraviolet photoelectron spectroscopy XPS and UPS, x-ray photoelectron diffraction XPD, and ab initio calculations. While structural imperfections are observed at the surface and out of the various possible terminations, the puckered P2 layer is identified as the only surface termination, thus pointing out the existence of a well-defined minimum in the surface energy landscape. The measured step heights correspond to distances between identical planes along the 010 direction in the bulk model, i.e., b / 2. A bias dependency of the STM topography is found. The XPD and LEED patterns confirm the pseudotenfold symmetry of the sample. XPS and UPS show a more metallic signature of the T phase compared to Al-based quasicrystalline phases.

Transport properties (electrical resistivity, thermoelectric power, and thermal conductivity) of the monoclinic Y-Al-Co-Ni[1], orthorhombic o-Al13Co4[2], monoclinic m-Al13Fe4 and m-Al13(Fe, Ni)4[3], which belong to the Al13TM4 (TM=transition metal) class of approximants to decagonal phases have been investigated. They are characterized by a very large unit cell size and with the large structural complexity. Common to all investigated intermetallics is strong anisotropy of the transport properties which is qualitatively similar to the decagonal quasicrystals d-Al-Ni-Co[4]. The approximants to decagonal phases and decagonal quasicrystals have similar structural details on the atomic scale and one set of the atomic planes that is stacked periodically with the same periodicity length. The stacked-layer structure appears to be origin of the anisotropic transport properties of the Al13TM4 complex intermetallics, whereas the in-plane structural details seem to be of marginal importance. The results for Al13TM4 are compared with the recently obtained results for the single crystal of structurally similar Taylor phase T-Al11(MnFe)4[5] and single crystal of decagonal quasicrystal d-Al77Co6Ni17 [6]. [1] A. Smontara, et al. ; Phys. Rev. B, 78 (2008) 104204. [2] J. Dolinšek, et al. ; Phys. Rev. B, 79 (2009) 184201. [3] P. Popčević, et al. ; Phys. Rev. B, 81 (2010) 184203. [4] S. Martin, et. al. ; Phys. Rev. Lett. 67 (1991) 719. [5] M. Heggen, et al. ; Phys. Rev. B, 81 (2010) 184204. [6] P. Popčević, K. Velebit and A. Smontara, unpublished results.

The atomic and electronic structures of the (010) surface of the T-Al-3(Mn,Pd) complex metallic alloy is investigated by means of low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), x-ray photoelectron diffraction (XPD), and ab initio calculations. While structural imperfections are observed at the surface and out of the various possible terminations, the puckered P2 layer is identified as the only surface termination, thus pointing out the existence of a well-defined minimum in the surface energy landscape. The measured step heights correspond to distances between identical planes along the [010] direction in the bulk model, i.e., b/2. A bias dependency of the STM topography is found. The XPD and LEED patterns confirm the pseudotenfold symmetry of the sample. XPS and UPS show a more metallic signature of the T phase compared to Al-based quasicrystalline phases.

We have investigated anisotropic physical properties (the magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient and the thermal conductivity) of the single-crystalline Taylor-phase T-Al72.5Mn21.5Fe6.0 complex intermetallic that is an orthorhombic approximant to the d-Al-Mn-Pd decagonal quasicrystal. The measurements were performed along the a, b, and c directions of the orthorhombic unit cell, where (a, c) atomic planes are stacked along the perpendicular b direction. The T-Al72.5Mn21.5Fe6.0 shows spin-glass behavior below the spin-freezing temperature T-f approximate to 29 K with a small anisotropy in the magnetic susceptibility. The anisotropic electrical resistivities are rather large and show negative temperature coefficient. The resistivity is lowest along the stacking direction, which appears to be a common property of the decagonal-approximant phases with a stacked-layer structure. The temperature-dependent resistivity was theoretically reproduced by the quantum transport theory of slow charge carriers. The thermopower is positive for all three crystallographic directions, indicating that holes are the majority charge carriers, and no anisotropy can be claimed within the experimental precision. The same conclusion on the holes being the dominant charge carriers follows from the Hall-coefficient measurements, which is a sum of the (positive) normal Hall coefficient and the anomalous term, originating from the magnetization. The anisotropy of the thermal conductivity is practically negligible. The T-Al72.5Mn21.5Fe6.0 Taylor phase can be considered as a "close-to-isotropic" complex intermetallic. The relation of the anisotropic physical properties of the Taylor phase to other families of decagonal-approximant phases with the stacked-layer structure is discussed.

Taylor-phase (T‑Al72.5Mn21.5Fe6.0), an orthorhombic approximant to the decagonal quasicrystalline phase, unlike the other decagonal approximant phases exhibits unusual PTC behavior of the electrical conductivity, s, from 2 K up to room temperature. Transport properties (electrical resistivity r, thermopower S and thermal conductivity k) of the single crystalline T‑Al72.5Mn21.5Fe6.0 along three crystallographic directions reveal minor anisotropy. Thermopower is positive suggesting holes as majority charge carriers. Electrical conductivity and thermopower analyzed in the Kubo-Greenwood formalism provided electronic contribution to the thermal conductivity enabling us examination of the lattice thermal conductivity for the further analysis and checking the validity of the Wiedemann-Franz law.

We present a detailed study of the (100) surface of the orthorhombic Al13Co4 crystal using both experimental and ab initio computational methods. This complex metallic alloy is an approximant of the decagonal Al-Ni-Co quasicrystalline phase. After sputter-annealing preparation of the surface at 1073 K, the low-energy electron diffraction pattern recorded exhibits a pseudotenfold symmetry with lattice parameters consistent with those of the bulk model. At this stage, scanning tunneling microscopy (STM) measurements reveal two different types of surface terminations. A comparison between these two surface structures and the bulk planes indicate that the terminations correspond either to an incomplete puckered layer (P) or to an incomplete flat layer (F). At 1173 K, the majority of the surface consists of P layer terminations. STM images calculated from our proposed surface model are in good agreement with experimental images. X-ray photoelectron diffraction patterns and single scattering cluster calculations further confirm that the local atomic arrangements present in the bulk model are preserved within the near-surface region.

The Hall coefficient RH of the triclinic Al73Mn27 and Taylor-phase Al73Mn27-xPdx (x = 0, 2, 4 and 6) complex metallic alloys has been measured from 90 to 400 K.