Superheating and supercooling of lead precipitates in aluminum

Gråbæk, L.; Bohr, Jakob; Johnson, E.; Johansen, Å.; Sarholt-Kristensen, L.; Andersen, H. H.

doi:10.1103/physrevlett.64.934

Cited by 162 publications

(93 citation statements)

References 18 publications

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“…who measured superheating of about 60K [12] and even higher [13] for particles about 14nm in size in alloys made by ion implantation. Similar behavior with superheating up to 40K was also found by Zhang and Cantor in material with somewhat larger particles made by melt spinning [14].…”

Section: Introductionmentioning

confidence: 99%

Equilibrium shape and interface roughening of small liquid Pb inclusions in solid Al

et al. 2001

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The shape of liquid Pb inclusions embedded in a solid Al matrix was investigated at temperatures between 300 and 500°C using in-situ electron microscopy. Inclusion shapes in the size range from a few nanometers to about 150 nanometers were found to depend on size, temperature and thermal history. During isothermal annealing after melting, small inclusions rounded off while larger inclusions remained faceted until the temperature was raised to about 500°C. During subsequent cooling, inclusions refaceted, although less strongly than during heating. The shape hysteresis between heating and cooling cycles was found to be due to the barrier of ledge nucleation necessary to advance the faceted interfaces. It is shown that this kinetic barrier can explain the observed dependence on size and temperature, and that the {111} interface undergoes a roughening transition at about 550°C. Even under conditions of kinetic limitation it was possible to measure local equilibrium by modeling kinetically limited inclusions as a droplet in a crevice. For this type of measurement, the hysteresis between heating and cooling cycles disappeared, and the true equilibrium shape could be derived. The anisotropy of interfacial energy was shown to be significantly smaller than previously reported, and at about 2 %, similar to the anisotropy of the surface energy for fcc metals.From the width of facets on the equilibrium shape, the step energy was determined to be at 350°C. ε = 1.9⋅10 -11 J / m 1 9/29/00

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Section: Introductionmentioning

confidence: 99%

Equilibrium shape and interface roughening of small liquid Pb inclusions in solid Al

et al. 2001

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“…Ec, 74.60.Ge, 74.72.Hs Melting of heterogeneous systems, and in particular of nanocrystals embedded in porous rigid matrices, is a complex process with many uncontrolled parameters. Metal and semiconductor nanocrystals with free surfaces, for example, usually show a decrease in their melting temperature with decreasing size [1], whereas nanocrystals encapsulated in a porous matrix often display an increase in melting temperature [2]. Although the contribution of the different factors is still a matter of debate, the melting process is known to depend on the size, dimensionality, material properties of the nanocrystals and the matrix, as well as the interface energies between the materials [1,2].…”

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confidence: 99%

“…Metal and semiconductor nanocrystals with free surfaces, for example, usually show a decrease in their melting temperature with decreasing size [1], whereas nanocrystals encapsulated in a porous matrix often display an increase in melting temperature [2]. Although the contribution of the different factors is still a matter of debate, the melting process is known to depend on the size, dimensionality, material properties of the nanocrystals and the matrix, as well as the interface energies between the materials [1,2]. In this work we investigate an analogous, but a more controllable composite system, which is a 'porous' vortex matter consisting of vortex nanocrystals encapsulated in a matrix of strongly pinned vortices.…”

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confidence: 99%

Melting of “Porous” Vortex Matter

et al. 2003

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Bitter decoration and magneto-optical studies reveal that in heavy-ion irradiated superconductors, a 'porous' vortex matter is formed when vortices outnumber columnar defects (CDs). In this state ordered vortex crystallites are embedded in the 'pores' of a rigid matrix of vortices pinned on CDs. The crystallites melt through a first-order transition while the matrix remains solid. The melting temperature increases with density of CDs and eventually turns into a continuous transition. At high temperatures a sharp kink in the melting line is found, signaling an abrupt change from crystallite melting to melting of the rigid matrix.PACS numbers: 74.60. Ec, 74.60.Ge, 74.72.Hs Melting of heterogeneous systems, and in particular of nanocrystals embedded in porous rigid matrices, is a complex process with many uncontrolled parameters. Metal and semiconductor nanocrystals with free surfaces, for example, usually show a decrease in their melting temperature with decreasing size [1], whereas nanocrystals encapsulated in a porous matrix often display an increase in melting temperature [2]. Although the contribution of the different factors is still a matter of debate, the melting process is known to depend on the size, dimensionality, material properties of the nanocrystals and the matrix, as well as the interface energies between the materials [1,2]. In this work we investigate an analogous, but a more controllable composite system, which is a 'porous' vortex matter consisting of vortex nanocrystals encapsulated in a matrix of strongly pinned vortices. As shown below, this system is present in the commonly heavy-ion irradiated superconductors when the vortices outnumber the columnar defects (CDs). The rigid matrix is created by vortices localized on the network of random CDs, while the softer nanocrystals are formed within the 'pores' of this matrix by the interstitial vortices. The size of the nanocrystals can be readily varied from several hundred down to a few vortices by changing the applied field or the density of CDs. We find that this composite vortex matter reveals a number of intriguing mechanisms: Similarly to the metallic nanocrystals in a matrix, we observe for the first time a pronounced upward shift in the vortex melting temperature T m , while preserving the first-order nature of the transition (FOT). With increasing density of CDs, the size of the pores decreases, resulting in a larger shift in T m . We also find a critical point at which the FOT changes into a continuous melting. Moreover, the crystallites can melt while the matrix remains rigid. As a result, at high temperatures we find an abrupt breakdown in the upward shift of T m and a sharp kink in the FOT line, which apparently result from the collapse of the matrix due to vortex depinning from the CDs.The reported findings were obtained using Bitter decoration and differential magneto-optical (MO) [3] techniques. High quality Bi 2 Sr 2 CaCu 2 O 8 (BSCCO) crystals (T c ≈ 89 K) were covered by various patterned masks and irradiated at GANIL by 1 Ge...

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“…However, in most experiments, superheating of solids was achieved by epitaxial confinement of the solids with semicoherent interfaces, in which heterogeneous nucleation of melting at surfaces and interfaces is effectively suppressed. This type of semicoherent-interface-induced superheating has been frequently obtained in particle-matrix systems, for example embedded solid particles in a high-melting-point matrix with an epitaxial (semicoherent) particle-matrix interface [7][8][9][10][11][12]. Superheating of Pb thin films confined *Corresponding author.…”

Section: Introductionmentioning

confidence: 94%

The kinetic limit of superheating induced by semicoherent interfaces

Mei¹,

Jin²,

Lu³

2005

Philosophical Magazine Letters

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The superheating behaviour of embedded particles induced by semicoherent interfaces has been observed in many circumstances. In this paper, a phenomenological model for melt nucleation on misfit dislocations at a semicoherent interface is proposed. A kinetic limit for semicoherent-interface-induced superheating, which is in good agreement with the results of experiments and computer simulations, is derived from this model. Calculations and analyses based on the model reveal that melting prefers to initiate at the semicoherent interface and that superheating of embedded particles is possible for a melt nucleation contact angle less than 90. Among the matrix-dependent parameters, the contact angle and the shear modulus of the matrix are found to be dominant in determining the superheating of embedded particles.

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Superheating and supercooling of lead precipitates in aluminum

Cited by 162 publications

References 18 publications

Equilibrium shape and interface roughening of small liquid Pb inclusions in solid Al

Equilibrium shape and interface roughening of small liquid Pb inclusions in solid Al

Melting of “Porous” Vortex Matter

The kinetic limit of superheating induced by semicoherent interfaces

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