Atomic Transport in Dense, Multi-Component Metallic Liquids

Pd43Ni10Cu27P0 has been investigated in its equilibrium liquid state with incoherent, inelastic neutron scattering. As compared to simple liquids, liquid PdNiCuP is characterized by a dense packing with a packing fraction above 0.5. The intermediate scattering function exhibits a fast relaxation process that precedes structural relaxation. Structural relaxation obeys a time-temperature superposition that extends over a temperature range of 540K. The mode-coupling theory of the liquid to glass transition (MCT) gives a consistent description of the dynamics which governs the mass transport in liquid PdNiCuP alloys. MCT scaling laws extrapolate to a critical temperature Tc at about 20% below the liquidus temperature. Diffusivities derived from the mean relaxation times compare well with Co diffusivities from recent tracer diffusion measurements and diffsuivities calculated from viscosity via the Stokes-Einstein relation. In contrast to simple metallic liquids, the atomic transport in dense, liquid PdNiCuP is characterized by a drastical slowing down of dynamics on cooling, a q^{-2} dependence of the mean relaxation times at intermediate q and a vanishing isotope effect as a result of a highly collective transport mechanism. At temperatures as high as 2Tc diffusion in liquid PdNiCuP is as fast as in simple liquids at the melting point. However, the difference in the underlying atomic transport mechanism indicates that the diffusion mechanism in liquids is not controlled by the value of the diffusivity but rather by that of the packing fraction

Diffusion and isotope effect in bulk-metallic glass-forming Pd-Cu-Ni-P alloys from the glass to the equilibrium melt

We report on radiotracer diffusion measurements in metallic bulk-glass-forming Pd-Cu-Ni-P alloys. The Pd-Cu-Ni-P system, with its high stability against crystallization, allows diffusion measurements from the glassy state to the equilibrium melt for the first time. Serial sectioning was performed by grinding and ion-beam sputtering. The time and temperature as well as mass dependence, expressed in terms of the isotope effect E, of codiffusion were investigated. In the glassy state as well as in the deeply supercooled state below the critical temperature Tc, where the mode-coupling theory predicts a freezing-in of liquidlike motion, the measured very small isotope effects indicated a highly collective hopping mechanism. Below T c, the temperature dependence showed Arrhenius-type behavior. Above Tc, the onset of liquidlike motion was evidenced by a gradual drop of the effective activation energy, resulting from the decay of hopping barriers, and by the validity of the Sto kes-Einstein equation, which was found to break down below Tc. This strongly supports the mode-coupling scenario. Isotope effect measurements, which have never been carried out near Tc in any material, showed atomic transport up to the equilibrium melt to be far away from the hydrodynamic regime of uncorrelated binary collisions. The latter appears to be a prerequisite of excellent glass-forming abilities

INKtelligent printing® for sensorial applications

Purpose The purpose of this paper is to highlight INKtelligent printed sensor structures using maskless depositition technologies. Design/methodology/approach This paper begins with a general introduction to INKtelligent printing (R). Starting with layout and ink development, the fabrication of printed sensors is described in detail. Findings Printed strain gauges, thermopiles and gas sensitive films are successfully fabricated with maskless deposition technologies, offering advantages for continuous non-destructive measurement compared to conventional sensors. Originality/value This paper shows a new approach for customized sensor structures. The application of a resource efficient and flexible printing technique for sensor fabrication is demonstrated

Isotope effect of

The time dependence and the isotope effect $E = (D_\alpha / D_\beta - 1)/(\sqrt{m_\beta /m_\alpha} - 1)$ of Co diffusion have been measured in amorphous \ab{Co}_{51}\ab{Zr}_{49} during structural relaxation. The radiotracer technique in conjunction with serial sectioning using ion-beam sputtering was employed to observe diffusion on a nanometer scale. A drastic drop of diffusivity during structural relaxation in these thin films was found which is of the same order of magnitude observed in much thicker \ab{Co}_{89}\ab{Zr}_{11} glasses(Dörner W. and Mehrer H

Photocatalysis on silver-layer silicate/titanium dioxide composite thin films at solid/vapour interface

Silver-montmorillonite/TiO2 composites were prepared using various mixing ratios. The optical properties of the catalyst composites were evaluated DR-UV-vis spectrophotometry. Their photocatalytic efficiencies were tested in the degradation of ethanol vapour at a relative humidity of similar to 70% in a closed circulating reactor. Light sources used were 15 W lamps, one rich in UV (lambda >= 254 nm) and one emitting visible light (lambda >= 435 nm). The course of photodegradation of ethanol vapour was monitored by gas chromatography. By incorporating silver ions into clay minerals/TiO2 mixtures with different ratio, we obtained composites capable of degrading ethanol in the visible wavelength range about twice as fast as the reference photocatalyst, type P25. The synergistic effect is interpreted as the result of the excellent adsorption capabilities of layer silicates combined with the advantageous effect of silver nanoparticles and silver oxides on light absorption in the visible range

INKtelligent printing of metal and metal alloys for sensor structures

INKtelligent printing denotes the fabrication of functional structures, e.g. conductive paths and sensor structures, with the help of maskless printing technologies like inkjet and aerosol printing. The main objective for this research is a surface or component with improved performance due to better and new properties like crack detection or temperature measurement. The application areas for INKtelligent printing are multifaceted comprising automotive, aerospace and life science. An important requirement for the use of printing technologies is the availability of a suitable base material, in this case a suspension containing nanosized particles, so called functional ink. Such inks can be printed on planar and even non-planar surfaces with resolutions down to ten microns or even below. The printing process is followed by a thermal treatment e.g. in a furnace or with a laser to achieve dense functionalized structures. This paper highlights the development and processing of metal inks based on Ag and a Cu/Ni alloy. Both materials are fabricated with a physical sputter process called Vacuum Evaporation on Running Liquids (VERL) technology where particles are directly sputtered into fluids. Among the fabrication process the printing on different surfaces with an aerosol printing technology called M3D (Maskless Mesoscale Material Deposition) as well as different sintering methods of Ag and Cu/Ni structures are demonstrated. Results are discussed in view of possible use for sensor applications. Nanosized Ag ink produced by the VERL process could be successfully printed by using the M3D technology. Electrical characterization of printed and sintered structures shows low resistivity down to twice the bulk value. Furthermore metal alloy ink (Cu/Ni) could be successfully developed and printed. Both materials are interesting for sensor structures like strain gauges or temperature sensors. Especially Cu/Ni alloy offers advantages as sensor material due to its small temperature coefficient

Novel multifunctional nanocomposites from titanate nanosheets and semiconductor quantum dots

A novel synthesis for a titanate nanosheets loaded nanocomposite has been developed. On this basis, a multifunctional material for optical applications has been fabricated with tunable refractive index, improved processing behavior and luminescent properties imparted by the incorporation of semiconductor quantum dots. Titanate synthesis, host material choice and quantum dots functionalization have been here addressed to obtain films with good optical quality and stable photoluminescence. In order to assess the potential application of the obtained nanocomposites, imprinting lithography and aerosol-based deposition techniques have been applied with promising results. The obtained nanocomposites have been characterized by UV-Vis, photoluminescence and FT-IR spectroscopy, X-ray diffraction and Transmission Electron Microscopy. The optical properties of the nanocomposite film have been tested by spectroscopic ellipsometry and M-line technique