Microscopic Structure of the Wetting Film at the Surface of Liquid Ga-Bi Alloys

Tostmann, H.; DiMasi, Elaine; Shpyrko, Oleg; Pershan, Peter S.; Ocko, B. M.; Deutsch, Moshe

doi:10.1103/physrevlett.84.4385

Cited by 60 publications

(46 citation statements)

References 14 publications

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“…In temperature regime II, the high density, Bi-rich phase wets the free surface by intruding between the low density phase and the Bi monolayer, in defiance of gravity. 8 Considering that pure Bi has a significantly lower surface tension than pure Ga, the segregation of the Bi-rich phase at the surface is not too surprising. In fact, the thickness of the wetting layer in such a geometry is believed to be limited only by the extra gravitational potential energy paid for having the heavier phase at the top 10 .…”

Section: Bulk and Surface Structurementioning

confidence: 99%

Wetting behavior at the free surface of a liquid gallium–bismuth alloy: an X-ray reflectivity study close to the bulk monotectic point

Huber

Shpyrko

Pershan

et al. 2002

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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We present x-ray reflectivity measurements from the free surface of a liquid gallium-bismuth alloy (Ga-Bi) in the temperature range close to the bulk monotectic temperature Tmono = 222• C. Our measurements indicate a continuous formation of a thick wetting film at the free surface of the binary system driven by the first order transition in the bulk at the monotectic point. We show that the behavior observed is that of a complete wetting at a tetra point of solid-liquid-liquid-vapor coexistance.PACS numbers:

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Section: Bulk and Surface Structurementioning

confidence: 99%

Wetting behavior at the free surface of a liquid gallium–bismuth alloy: an X-ray reflectivity study close to the bulk monotectic point

Huber

Shpyrko

Pershan

et al. 2002

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…We demonstrated here that this method allows visualizing and examining on a macroscopic scale rheological aspects of microscopic structured surfaces, in particular the interesting case of a change of the shear-stress boundary condition at a liquid's surface from the generic, free-slip one to a no-slip one, characteristic of a wetted solid wall [33]. We hope that this study will stimulate further experiments focusing on how the surface hydrodynamics is affected by microscopic modifications of the structure of surfaces or interfaces, e.g., experiments on wetting transitions which have been proven to allow for a precise control of liquid surface microstructure as a function of temperature [34]. This method could also extend the wavelength and frequency ranges of established semi-microscopic and microscopic techniques like light scattering [25] and surface x-ray photon correlation spectroscopy [35] towards macroscopic hydrodynamic length scales.…”

Section: ∼4mentioning

confidence: 99%

Faraday Instability in a Surface-Frozen Liquid

et al. 2005

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Faraday surface instability measurements of the critical acceleration, ac, and wavenumber, kc, for standing surface waves on a tetracosanol (C24H50) melt exhibit abrupt changes at Ts = 54 • C, ∼4 • C above the bulk freezing temperature. The measured variations of ac and kc vs. temperature and driving frequency are accounted for quantitatively by a hydrodynamic model, revealing a change from a free-slip surface flow, generic for a free liquid surface (T > Ts), to a surface-pinned, no-slip flow, characteristic of a flow near a wetted solid wall (T < Ts). The change at Ts is traced to the onset of surface freezing, where the steep velocity gradient in the surface-pinned flow significantly increases the viscous dissipation near the surface.PACS numbers: 47.20.Ma, 61.25.Em, 64.70.Dv Spatial confinement of a liquid often changes its properties markedly. For example, superheating above the equilibrium melting temperature [1] and order quenching upon freezing [2] were observed under confinement only. In particular, flow under confinement is important for processes ranging from tribology to protein folding to transport through ion channels in cell membranes [3]. A transition from a liquid-like to a granular-solid-like shear response was observed at nano-scale confinements [4]. The surface freezing (SF) effect [5], where a solid monolayer forms at the surface of a pure normal-alkane (C n H 2n+2 ) melt, provides a unique system for studying semi-confined flow at a solid-liquid interface. The abrupt onset of SF at T s allows one to switch on (and off) the solid phase by a small temperature variation. Understanding such interfaces would also elucidate the role of flow in nucleation and growth processes of crystals from melts, which are dominated by such interfaces [6].SF occurs in melts of several chain molecules (alkenes, alcohols, semi-fluorinated alkanes, diols, C i E j ) [7], and at both liquid/liquid [8] and liquid/solid [9] interfaces. Related surface ordering effects were observed in melts of polymers comprising alkyl chains in the backbone or as side chains [10], in liquid alloys [11], and in several liquid crystals [12]. While the structural and thermodynamic aspects of SF have been studied in great detail [13], the influence of surface ordering on macroscopic near-surface flows has received little attention to date in this sizable, technologically-important class of materials.To study this issue, we employ the Faraday instability, which forms standing wave patterns (SWP) at the free surface of a vertically-vibrated liquid [14]. By virtue of its simplicity, this instability is outstanding among pattern-forming systems and a detailed theoretical description has been achieved. The SWP formed depend sensitively on, and allow a detailed study of, the changes in the surface hydrodynamics upon SF. As this study of SF demonstrates, the instability can therefore be employed to explore physical processes which are difficult to access by other, classical means. It also exemplifies the more general class of parametric inst...

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“…For the Ga-Bi system, the high density phase (Bi) was confined to the bottom of the container when the temperature was lower than the characteristic wetting temperature T crit = 262 o C; see Fig. 1(a) [11,12]. Above the critical temperature, the low surface tension component, Bi, was present at the interface of the binary mixture.…”

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confidence: 97%

Rapid synthesis of high purity GaN powder

Wu¹,

Hunting

DiSalvo

et al. 2005

phys. stat. sol. (c)

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High purity, strong luminescent gallium nitride (GaN) powders were synthesized by direct reaction of gallium (Ga) and ammonia (NH 3 ) using bismuth (Bi) as a catalyst in a vertical furnace. The reaction rate and yield from metal Ga were improved dramatically in the presence of Bi. In this simple apparatus, 25g Ga can be fully, stoichiometrically converted into GaN within 5 hours. The optimum temperature, NH 3 flow rate and reaction time in this hot wall tube furnace were 1000 o C, 500 standard cubic centimetres per minute (sccm) and 5 hours, respectively. X-ray diffraction demonstrates that the material has a high purity and a single crystalline structure. Electron microscopy was used to characterize the morphology of the powder particles. Powder purity was analyzed by utilizing Glow Discharge Mass Spectrometry (GDMS). Cathodoluminescence (CL) data showed strong luminescence from the powder.

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Microscopic Structure of the Wetting Film at the Surface of Liquid Ga-Bi Alloys

Cited by 60 publications

References 14 publications

Wetting behavior at the free surface of a liquid gallium–bismuth alloy: an X-ray reflectivity study close to the bulk monotectic point

Wetting behavior at the free surface of a liquid gallium–bismuth alloy: an X-ray reflectivity study close to the bulk monotectic point

Faraday Instability in a Surface-Frozen Liquid

Rapid synthesis of high purity GaN powder

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