To explain the unusual stability of undercooled liquids against crystallization, Frank hypothesized that local structures contain a significant degree icosahedral short-range order, which is incompatible with long-range periodicity. We present here first direct experimental demonstration Frank's complete hypothesis, showing correlation between nucleation barrier and growing order decreasing temperature in Ti39.5Zr39.5Ni21 liquid. A new facility, BESL (Beamline Electrostatic Levitation), was...

The state of the art in condition monitoring wind turbines, and related technologies currently applied practice under development for aerospace applications, are reviewed. Condition systems estimate current a machine from sensor measurements, whereas prognosis give probabilistic forecast future projected usage conditions. Current turbine rotors involves tracking rotor imbalance, aerodynamic asymmetry, surface roughness overall performance offline online measurements stress strain. Related...

New short-range order data are presented for equilibrium and undercooled liquids of Ti Ni. These were obtained from in situ synchrotron x-ray diffraction measurements electrostatically levitated droplets. While the liquid Ni is icosahedral, consistent with Frank's hypothesis, significantly distorted icosahedral observed Ti. This first experimental observation any liquid, although this has been predicted by theoretical studies on atomic clusters.

Levitation techniques have been applied to a staggering range of materials, from liquid helium aqueous solutions proteins, metals, ceramics, glasses and semiconductors. These experiments encompassed temperatures cryogenic greater than 2500 °C, samples micrograms tens kilograms. It should come as no surprise that wide variety levitation principles employed for processing these samples, including electromagnetic (EML), electrostatic (ESL), aerodynamic gas film, acoustic dia- or paramagnetic...

Evidence for rapid ordering in a supercooled Cu${}_{46}$Zr${}_{54}$ liquid, obtained from high-energy x-ray diffraction containerless processing environment, is presented. Relatively sudden changes were observed the topological and chemical short-range order near 850 \ifmmode^\circ\else\textdegree\fi{}C, temperature that 75 \ifmmode^\circ\else\textdegree\fi{}C below liquidus 465 above glass transition temperature. A peak specific heat was with supercooling, an onset (the same as of ordering)...

The crystallization kinetics of Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 were studied in an electrostatic levitation (ESL) apparatus. measured critical cooling rate is 1.75 K/s. the first bulk-metallic-glass-forming liquid that does not contain beryllium to be vitrified by purely radiative ESL. Furthermore, sluggish enable determination time-temperature-transformation (TTT) diagram between liquidus and glass transition temperatures. shortest time reach isothermal experiment; i.e., nose TTT 32 s. at 900...

Comprehensive undercooling experiments on a large number of simple crystalline, polytetrahedral, and icosahedral quasicrystalline phase forming compositions in $\mathrm{Ti}\text{\ensuremath{-}}\mathrm{Zr}\text{\ensuremath{-}}\mathrm{Ni}$ alloys have been carried out using electrostatic levitation (ESL) techniques for containerless processing. Consistent with Frank's hypothesis, direct correlation was found between the reduced...

Determinations of the phase formation sequence, crystal structures and thermo-physical properties materials at high temperatures are hampered by contamination from sample container environment. Containerless processing techniques, such as electrostatic (ESL), electromagnetic, aerodynamic, acoustic levitation, most suitable for these studies. An adaptation ESL in situ structural studies a wide range using energy (30–130keV) x rays synchrotron source is described here. This beamline (BESL)...

Recently, we reported the results of experimental in situ high-energy x-ray diffraction studies electrostatically levitated equilibrium and supercooled metallic elements alloy liquids, showing evidence for icosahedral short-range ordering (ISRO). In this paper, these are extended to binary Ti-Zr ternary Ti-Zr-Ni alloys. From a cluster-based analysis structure factors, it is concluded that ISRO alloys becomes progressively more dominant, coherence length order longer, with addition Ni,...

Under terrestrial conditions, liquids are stirred by Marangoni and gravity-induced flows. A nucleation model that couples the stochastic fluxes of long-range diffusion interfacial attachment [the Coupled-Flux Model (CFM)] predicts kinetics in metallic should be faster with increased stirring for cases where is required due to an additional mechanism transportation atoms nucleating cluster. Unfortunately, few experimental studies effects exist liquids. Here, effect on hundreds cycles...

Employing the technique of electrostatic levitation, coupled with high-energy x-ray diffraction and rapid data acquisition methods, we have obtained high quality structural more deeply into supercooled regime liquid silicon than has been possible before. No change in coordination number is observed this temperature region, calling question previous experimental claims evidence for existence a liquid-liquid phase transition.

By combining the best practices in optical dilatometry with numerical methods, a high-speed and high-precision technique has been developed to measure volume of levitated, containerlessly processed samples subpixel resolution. Containerless processing provides ability study highly reactive materials without possibility contamination affecting thermophysical properties. Levitation is common used isolate sample as it being processed. Noncontact measurement properties very important traditional...

Molecular dynamics (MD) simulations were performed of the structural changes occurring through liquid–glass transition in Cu–Zr alloys. The total scattering functions (TSF), and their associated primary diffuse peak positions (K p), heights h) full-widths at half maximum FWHM) used as metrics to compare high-energy X-ray data. residuals difference between model experimental TSFs are ∼0.03 for liquids about 0.07 glasses. Over compositional range studied, Zr1− x Cu (0.1 ≤ 0.9), K p, h FWHM...

A bstract : Different containerless processing techniques have different strengths and weaknesses. Applying more than one technique allows various parts of a problem to be solved separately. For two research projects, on phase selection in steels the other nucleation growth quasicrystals, combination experiments using electrostatic levitation (ESL) electromagnetic (EML) is appropriate. In both experiments, convection an important variable. The convective conditions achievable with each...

High-energy x-ray diffraction and ab initio molecular-dynamics simulations demonstrate that the short-range order in deeply undercooled ${\text{Zr}}_{2}\text{Ni}$ liquid is quite nuanced. The second diffuse scattering peak total structure factory sharpens with supercooling, revealing a shoulder on high-$Q$ side often taken to be hallmark of increasing icosahedral order. However, Voronoi tessellation indicates only approximately 3.5% all atoms are an or icosahedral-like environment. In...

Surface tension is an essential thermophysical property of liquids, and the oscillating droplet method particularly effective for investigations involving reactive molten alloys. The Rayleigh equation commonly used to evaluate surface from measurements damping frequency response with small deformation, but non-linear effects are expected arise larger deformation. This work describes improved interpreting analysis validates previous numerical simulation theoretical analyses which predict a...

Electromagnetic levitation techniques are used in a microgravity environment to allow materials research under containerless conditions while limiting the influence of gravity. The induced advective flow inside levitated molten alloy droplet is key factor affecting solidification phenomena potentially influencing measurement thermophysical properties metallic alloy. It thus important predict velocity various operation during melt processing. In this work, magnetohydrodynamic model applied...

Abstract Oscillating droplet experiments are conducted using the Electromagnetic Levitation (EML) facility under microgravity conditions. The of molten metal is internally stirred concurrently with pulse excitation initiating shape oscillations, allowing viscosity measurement liquid melts based on damping rate oscillating droplet. We experimentally investigate impact convection droplet’s behavior. effective arises and increases as internal convective flow becomes transitional or turbulent,...