Medium-range structure in glasses and low-Q structure in neutron and X-ray scattering data

Gaskell, Philip

doi:10.1016/j.jnoncrysol.2005.01.011

Cited by 63 publications

(24 citation statements)

References 28 publications

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“…Moreover, it has been found that this model fails to describe metal-metalloid-based alloys with pronounced chemical short-range order. In light of this, Gaskell proposed a stereochemically defi ned model that stipulates that the local unit of nearest neighbors in amorphous metal-metalloid alloys should have the same type of structure as the corresponding crystalline compounds with a similar composition [21][22][23]. However, this model has not been found to be supported in metal-metal based metallic glasses.…”

Section: Structural Origins Of Metallic Glass Formationmentioning

confidence: 99%

A brief overview of bulk metallic glasses

2011

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Bulk metallic glasses, formed at very low critical cooling rates, are fundamentally diff erent from traditional amorphous alloys, which are usually formed at very high cooling rates in order to suppress the nucleation of crystalline phases. Th e high cooling rates required for the formation of traditional glassy alloys restrict the range of possible structures that can be prepared to powders, fi lms and ribbons. Of the extensive family of glasses, BMGs are probably the youngest, possessing a number of characteristics, such as amorphicity and high strength, that are shared by other glasses, including the most familiar window (oxide) glasses. However, the most important feature of BMGs that, along with other glasses, distinguish them from general amorphous materials is the glass transition that transforms supercooled liquids into a glassy state when cooled from high to low temperature and vice versa. Metallic glasses are therefore scientifi cally defi ned as amorphous alloys that exhibit a glass transition, from which derives their unique properties of extreme strength at low temperature and high fl exibility at high temperature, along with thermodynamic and physical properties that change abruptly at the glass transition temperature (T g ).Research on metallic glasses is closely related to that on metallic liquids. It is known that the atomic confi gurations of molten metals and alloys are disordered. Th e noncrystalline structure is expected to be retained if the liquids can be quenched at a suffi ciently high cooling rate to suppress the formation of equilibrium crystalline phases. Th e critical cooling rate required to freeze the liquid structure is estimated to be on the order of 10 5 -10 6 K s -1 for alloys. Th is assumption was proved experimentally in 1959 by a research group at Caltech, who reported the fi rst glassy alloy with a composition of Au 75 Si 25 produced by splat quenching [1]. In this pioneering work, the Au 75 Si 25 melt was quenched using a cold metal plate instead of the water or oil used traditionally. Th e good contact between liquid droplets and the cold metal avoids the formation of gaseous layers that limit the heat release during solidifi cation. Moreover, the droplets spread into a thin layer for rapid thermal diff usion when striking the solid, cold metal plate. X-ray diff raction analysis revealed the disappearance of all crystalline structure and the formation of a noncrystalline structure in the resultant micrometer-sized fl akes. Following this discovery, a large number of metallic glasses were found in various alloy systems, and rapid research progress was made in the search for new metallic glasses. Th is research was accelerated by the invention of a melt spinning method [2], a rapid cooling technique that can routinely quench liquid alloys as 10-50 μm thick ribbons at cooling rates of 10 3 -10 6 K s -1 by impinging a melt stream on a spinning copper wheel. Most glass-form alloys reported at that time were binary alloys, and their glass-forming ability was found to be strongl...

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Section: Structural Origins Of Metallic Glass Formationmentioning

confidence: 99%

A brief overview of bulk metallic glasses

2011

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“…As regards the two pre-peaks, they are generally attributed to medium-range order in liquids and amorphous solids [24,25], and are related to effective Bragg distances (2π/q) occurring in the partially ordered system, that correspond to 18.48 Å and 22.44 Å in distance space, respectively. Qualitatively speaking, all features seem to indicate that the insertion of even smaller quantities of bromine (1%) into CB structure causes the system to enlarge, if not to swell.…”

Section: Resultsmentioning

confidence: 99%

Brominated carbon black: An EDXD study

Carbone¹,

Gontrani

2014

AIP Conference Proceedings

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Abstract. An energy dispersive X-Ray study of pure and brominated carbon black was carried out. The analysis of the diffraction patterns reveals that the low bromine load (ca.1% mol) is trapped into the structure, without significantly modifying it. This allows the application of the difference methods, widely tested for electrolyte solutions, inorganic matrices containing metals and isomorphic substitutions.

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“…Medium range order has been detected in a wide variety of amorphous materials, including tetrahedral semiconductors (Ge and Si), [14][15][16] oxides (SiO 2 and GeO 2 ) 17 and even ternary 18 and quaternary glasses. 19 Indeed, the degree of such ordering can be controlled in a-Si with considerable precision through appropriate processing methods.…”

Section: Concept Of the Methodsmentioning

confidence: 99%

Directed self‐assembly by photostimulation of an amorphous semiconductor surface

Kondratenko

Seebauer

2010

AIChE Journal

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A method for nanoscale directed self-assembly is demonstrated that employs an amorphous semiconductor containing subcritical nuclei for crystallization. This strategy combines attractive features of top-down and bottom-up approaches by exploiting the self-organization capabilities latent in amorphous materials, but in a way that can be controlled by optical or electron beam exposure tools. The method was demonstrated with amorphous TiO 2 deposited on silicon, heated to 270 C, and exposed to low-level ultraviolet light.

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Medium-range structure in glasses and low-Q structure in neutron and X-ray scattering data

Cited by 63 publications

References 28 publications

A brief overview of bulk metallic glasses

A brief overview of bulk metallic glasses

Brominated carbon black: An EDXD study

Directed self‐assembly by photostimulation of an amorphous semiconductor surface

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