Atomic diffusion mechanisms in a binary metallic melt

Voigtmann, Thomas; Meyer, Andreas; Holland‐Moritz, D.; Stüber, S.; Hansen, Thomas C.; Unruh, Tobias

doi:10.1209/0295-5075/82/66001

Cited by 67 publications

(27 citation statements)

References 26 publications

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“…The latter requirement is fulfilled in metallic melts containing, e.g., Ni, Co, or Ti. So far, QNS on levitated samples has been, in particular, used to measure the self-diffusion coefficients of Ni in pure Ni, 15 Zr-Ni, 16,17 and silicon-rich Si-Ni. 18 The QNS measurement of the self-diffusion constant of Ti, D Ti , was performed at the neutron time-of-flight spectrometer TOFTOF ͑Ref.…”

Section: Experimental Techniquesmentioning

confidence: 99%

Improvement of computer simulation models for metallic melts via quasielastic neutron scattering: A case study of liquid titanium

et al. 2009

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A combination of quasielastic neutron scattering ͑QNS͒ and molecular-dynamics ͑MD͒ simulation is used to modify an embedded atom method ͑EAM͒ potential for Ti with respect to the description of melt properties and crystallization from the melt. In the MD simulation, the EAM model is optimized such that agreement with accurate data of self-diffusion coefficients from QNS is achieved. As a result the density and the melting temperature are in good agreement with experiment.

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Section: Experimental Techniquesmentioning

confidence: 99%

Improvement of computer simulation models for metallic melts via quasielastic neutron scattering: A case study of liquid titanium

et al. 2009

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“…However, NDIS requires good counting statistics due to the sample sizes (∼2-3 mm diameter) and is thus limited by the available flux at neutron sources. NDIS has previously been used to measure the full set of partial structure factors of levitated liquid and supercooled Ni 36 Zr 64 [15] and Ni-Si alloys [16], although these measurements benefit from the large scattering length contrast of 23.1 fm between the 58 Ni and 62 Ni isotopes. Natural calcium is composed mainly of 40 Ca (96.941% abundance) and 44 Ca (2.086% abundance) that have coherent neutron-scattering lengths of 4.80(2) fm and 1.42(6) fm, respectively [17].…”

Section: Introductionmentioning

confidence: 99%

Structure of liquid tricalcium aluminate

et al. 2017

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This is the final published version of the article (version of record). It first appeared online via APS at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.064203. Please refer to any applicable terms of use of the publisher. University of Bristol -Explore Bristol Research General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. The atomic-scale structure of aerodynamically levitated and laser-heated liquid tricalcium aluminate (Ca 3 Al 2 O 6 ) was measured at 2073(30) K by using the method of neutron diffraction with Ca isotope substitution (NDIS). The results enable the detailed resolution of the local coordination environment around calcium and aluminum atoms, including the direct determination of the liquid partial structure factor, S CaCa (Q), and partial pair distribution function, g CaCa (r). Molecular dynamics (MD) simulation and reverse Monte Carlo (RMC) refinement methods were employed to obtain a detailed atomistic model of the liquid structure. The composition Ca 3 Al 2 O 6 lies at the CaO-rich limit of the CaO:Al 2 O 3 glass-forming system. Our results show that, although significantly depolymerized, liquid Ca 3 Al 2 O 6 is largely composed of AlO 4 tetrahedra forming an infinite network with a slightly higher fraction of bridging oxygen atoms than expected for the composition. Calcium-centered polyhedra exhibit a wide distribution of four-to sevenfold coordinated sites, with higher coordinated calcium preferentially bonding to bridging oxygens. Analysis of the MD configuration reveals the presence of ∼10 % unconnected AlO 4 monomers and Al 2 O 7 dimers in the liquid. As the CaO concentration increases, the number of these isolated units increases, such that the upper value for the glass-forming composition of CaO:Al 2 O 3 liquids could be described in terms of a percolation threshold at which the glass can no longer support the formation of an infinitely connected AlO 4 network.

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“…For liquid Al 80 Ni 20 a value of E A (Al-Ni) = 0.36 eV is reported [7]. The determination of partial structure factors of molten Zr 64 Ni 36 by elastic neutron scattering by isotopic substitution [8,9] indicates a short-range order different from the icosahedral short-range order observed for a large variety of metallic melts [10]. The short-range order in liquid Zr 64 Ni 36 is characterized by a large local density of packing as indicated by high nearest neighbor coordination number of Z ≈ 13.9.…”

Section: Introductionmentioning

confidence: 99%

Ni self-diffusion in Zr-Ni(-Al) melts

Holland‐Moritz¹,

Stüber²,

Hartmann³

et al. 2009

J. Phys.: Conf. Ser.

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Abstract. We report on investigations on the atomic dynamics in melts of different binary ZrNi alloys and of the ternary glass-forming Zr 60 Ni 25 Al 15 alloy. The liquids are containerlessly processed in an electromagnetic levitator that is combined with quasielastic neutron scattering at the time of flight spectrometer TOFTOF of the FRM II. Ni self-diffusion coefficients are determined that exhibit an Arrhenius-type temperature dependence with comparatively large activation energies ranging between 0.64 and 0.90 eV. Although glass forming abilities and melting temperatures for these alloys exhibit large differences, the absolute values of the selfdiffusion coefficients are similar at same temperature. IntroductionAmong numerous multi-component alloys forming (bulk) metallic glasses [1], one important class of alloys is based on the binary Zr-Ni system. The solidification behaviour of melts and consequently the glass formation process is strongly affected by the the atomic dynamics in the liquid. While for glassforming Pd-(Ni-Cu-)P melts the viscosity is coupled with the diffusivity by the Stokes-Einstein relation above the critical temperature T c of mode-coupling theory [2], for Zr-Ti-Cu-Ni-Be melts viscosity and diffusivity are decoupled above T c and the liquidus temperature T L [3]. Moreover these liquids exhibit considerably smaller values of the Ni self-diffusivity as Pd-(Ni-Cu-)P alloys at similar temperatures. In this work we present investigations on the Ni self-diffusion in melts of different binary Zr-Ni alloys and of the ternary glass forming alloy Zr 60 Ni 25 Al 15 by quasielastic neutron scattering. In order to avoid reactions of the Zr-based melts with crucible materaials and in order to cover a large temperature range including the metastable regime of undercooled liquids at temperature below the melting temperature, the samples are containerlessly processed by application of the electromagnetic levitation technique.

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Atomic diffusion mechanisms in a binary metallic melt

Cited by 67 publications

References 26 publications

Improvement of computer simulation models for metallic melts via quasielastic neutron scattering: A case study of liquid titanium

Improvement of computer simulation models for metallic melts via quasielastic neutron scattering: A case study of liquid titanium

Structure of liquid tricalcium aluminate

Ni self-diffusion in Zr-Ni(-Al) melts

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