Search results for "Eutectic system"
showing 10 items of 44 documents
Binary alloys of Ge and Te: order, voids, and the eutectic composition
2008
The liquid and amorphous structures of ${\mathrm{Ge}}_{0.15}{\mathrm{Te}}_{0.85}$ and GeTe alloys are characterized using combined density functional/molecular dynamics simulations. Te is threefold coordinated, in contrast with predictions of the ``8-$N$ rule,'' and Ge atoms (fourfold coordinated) show octahedral and tetrahedral bonding angles. Cubic local environment occurs in both materials, and GeTe shows a pronounced alternation of atomic types. Tetrahedral Ge coordination is more common in the eutectic ${\mathrm{Ge}}_{0.15}{\mathrm{Te}}_{0.85}$, which comprises corner- and edge-sharing ${\mathrm{GeTe}}_{4}$ units surrounded by Te. There is no Te segregation, and the material resembles …
Density functional simulations of structure and polymorphism in Ga/Sb films.
2013
Thin films of gallium/antimony alloys are promising candidates for phase change memories requiring rapid crystallization at high crystallization temperatures. Prominent examples are the stoichiometric form GaSb and alloys near the eutectic composition GaSb(7), but little is known about their amorphous structures or the differences between the 'as-deposited' (AD) and 'melt-quenched' (MQ) forms. We have generated these structures using 528-atom density functional/molecular dynamics simulations, and we have studied in detail and compared structural parameters (pair distribution functions, structure factors, coordination numbers, bond and ring size distributions) and electronic properties (dens…
Polymer-enforced crystallization of a eutectic binary hard sphere mixture
2010
We prepared a buoyancy matched binary mixture of polydisperse polystyrene microgel spheres of size ratio 0.785 and at a volume fraction of 0.567 just below the kinetic glass transition. In line with theoretical expectations, a eutectic phase behavior was observed, but only a minor fraction of the samples crystallized at all. By adding a short non-adsorbing polymer we enforce inter-species fractionation into coexisting pure component crystals, which in turn also shows signs of intra-species fractionation. We show that in formerly inaccessible regions of the phase diagram binary hard sphere physics is made observable using attractive hard spheres. Ancillary files: Correction to Soft Matter 20…
Systematic Synthesis and Properties Evaluation of Dicationic Ionic Liquids, and a Glance Into a Potential New Field
2018
Dicationic ionic liquids (DILs), a subset of the ionic liquid (IL) family, have attracted growing interest in recent years, and the range of applications within which they are investigated is constantly expanding. However, data which allows structure to property correlation of a DIL is still limited, and thus selecting an appropriate salt to address a specific challenge can be problematic. In comparison to traditional ILs, DILs physico-chemical properties can be tuned by changing the length and type of spacer which connects the cationic heads as well as the type of cation. This in turn could give rise to symmetrical or asymmetrical DILs. In this work, a systematic study of a homogeneous cla…
The use of microcapillary techniques to study the corrosion resistance of AZ91 magnesium alloy at the microscale
2011
Abstract The AZ91 alloy is composed of Mg 17 (Al, Zn) 12 precipitates, an eutectic phase around these precipitates, AlMn intermetallic particles and an α-Mg solid solution (matrix). The corrosion behaviour of AZ91 was investigated at the microscale by means of the electrochemical microcell technique, which uses extremely small capillaries (diameters between 5 and 10 μm). Experiments were conducted in 0.1 M NaClO 4 at 25 °C. The β-Mg 17 (Al, Zn) 12 precipitates were found to have the highest corrosion resistance, whereas the eutectic phase was very active (pitting potential of approximately −1400 mV vs. Ag/AgCl). The α-Mg solid solution displayed better corrosion resistance than the eutectic…
Study of tritium and helium generation and release from lead-lithium eutectics Li15.7Pb under neutron irradiation
2019
Abstract This paper describes the experiments on study of tritium and helium generation and release processes from lead-lithium eutectics Li15.7Pb. The irradiation was performed at the IVG.1M research reactor at 6 MW of thermal power. The irradiation temperature increased step by step from 225 to 550 °C. A qualitative assessment of the experimental results showed that as the temperature rises above 390 °C, the tritium flux from the sample consisting of T2 and HT molecules decreases. It was concluded that the observed effect is similar to the previously observed one for lead-lithium eutectics with Li17Pb83 composition.
Crystallization kinetics of colloidal binary mixtures with depletion attraction.
2014
In this work the crystallization kinetics of colloidal binary mixtures with attractive interaction potential (Asakura–Oosawa) has been addressed. Parameters such as fraction of crystals, linear crystal dimension and crystal packing have been quantified in order to understand how the crystal formation is driven in terms of the depth of the attractive potential and the composition of the binary mixture (described by the number ratio). It was found that inside the eutectic triangle, crystallization is mainly governed by nucleation and the crystal packing is close to the close-packing of hard spheres. Moving out from the eutectic triangle towards small component results in the crystallization o…
Natural eutectogels: sustainable catalytic systems for C–C bond formation reactions
2021
Natural eutecto gels were prepared combining properties of amino acids with the ones of deep eutectic solvents. Soft materials obtained were fully characterised determining the gel-sol transition temperatures and analysing mechanical and morphological features through rheological measurements and polarised optical microscopy. All eutecto gels were tested as catalytic reaction media for the enantioselective aldol reaction and, the best performing one was also used to carry out the Michael addition. In both cases, eutecto gels proved to have a great potential as sustainable reaction media, allowing to perform processes under mild conditions, obtaining excellent yields and, in some cases, also…
Development of a liquid Pb-Bi target for high-power ISOL facilities
2016
Abstract This paper describes some R&D activities conducted in support of the design and safe operation of a high-power liquid Pb-Bi target within the LIEBE (Liquid Eutectic Lead Bismuth Loop Target for EURISOL) project. The target material is lead bismuth eutectic (LBE) which also acts as a primary coolant. As a consequence of interaction of the highly pulsed 1.4-GeV protons at ISOLDE with the target, heat powers of the order of 2 GW would be instantaneously deposited in the target during a bunch. Considerable R&D effort is thus required to demonstrate its continued coolability and structural integrity. This paper mainly reports on the conjugate flow (CFD) and heat deposition (Monte Carlo)…
Lead–gold eutectic: An alternative liquid target material candidate for high power spallation neutron sources
2011
Abstract One of the main technical concerns of Megawatt-class spallation neutron sources is the removal of the heat deposited in the target station. A way to overcome it is to use targets consisting of flowing liquid metals, but the already tested materials – mercury and lead–bismuth eutectic (LBE) – are not unproblematic. We show here that another eutectic alloy containing lead and gold (LGE) could be a suitable alternative. Besides a chemical toxicity lower than mercury, this low melting-point alloy has the advantage of being solid at RT. Moreover, it combines a neutron production similar to mercury and LBE with smaller amounts of alpha-emitting nuclides, relieving safety and environmenta…