Shock synthesis of silicides—II. Thermodynamics and kinetics

Meyers, Marc A.; Yu, Li-Hsing; Vecchio, Kenneth S.

doi:10.1016/0956-7151(94)90269-0

Cited by 59 publications

(42 citation statements)

References 12 publications

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“…Figures 3͑b͒ and 3͑c͒ show regions of mixing and reaction. Propagation of the reaction appears to be by the production of a liquid phase product (TiSi 2 ) at the solid Ti liquid Si interface, the formation of spherical nodules of this product, and subsequent solidification as described by Meyers et al 8 One of these regions appears to be a quenched liquid mixture of liquid Si and TiSi 2 ͓Fig. 3͑c͔͒.…”

Section: Resultsmentioning

confidence: 96%

“…Microstructural evidence of melting has been observed in a number of nonreacting shock compacted powders, typically in regions where voids collapsed on melt which flowed from deformation-heated surfaces. 7,8,[15][16][17] Therefore it is questionable that shock-induced reactions in powders, where the equilibrium shock temperature is below the melting points of the reactants, necessarily indicates solid-state reaction as stated in Ref. 9.…”

Section: Discussionmentioning

confidence: 99%

“…Evidence for solid-state reactions and possible evidence for the suppression of reaction under conditions which produce Si melting are discussed. Vecchio et al 7,8 studied reactions in shocked MoϩSi and NbϩSi and proposed that the threshold shock energy which was observed produces a critical melt pool size of Si. Recovered samples show evidence of a liquid phase reaction forming ϳ2 m spherical nodules of silicide which were injected into liquid Si.…”

Section: Introductionmentioning

confidence: 99%

“…Recovered samples show evidence of a liquid phase reaction forming ϳ2 m spherical nodules of silicide which were injected into liquid Si. Myers et al 8 proposed that the metal-Si interface grows from the dissolution of the metal into molten Si, producing the molten intermetallic, followed by spheroidization, solidification, and expulsion into the surrounding liquid silicon melt. Reaction rates could not be obtained from the observations, but their analysis shows that full reaction can occur in times comparable to the duration of a 1 s shock pulse for a constant reaction rate of 25 m/s in 50 m particles.…”

Section: Introductionmentioning

confidence: 99%

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Shock wave initiation of the Ti5Si3 reaction in elemental powders

Vreeland

Montilla

Mutz

1997

Journal of Applied Physics

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Elemental powder mixes were subjected to plane-wave shock processing which reduced the initial porosity to essentially zero. Two powder mixes in a 5:3 Ti:Si atomic ratio were used: Ϫ325 mesh Ti and Si ͑Ͻ45 m͒, and Ϫ100 mesh Ti and Si ͑Ͻ150 m͒ with shock pressures up to 7.3 GPa and shock energies up to 671 J/g. Shock pressures were calculated using hugoniot parameters for porous elemental powder mixtures and shock energies were taken to be the work done by the shock ( P⌬V/2). Shock energy thresholds for complete reaction of the elemental powders were found which depend upon powder particle size and the initial porosity of the powder. The threshold energy for the larger powder mix was found to be ϳ80% larger than that for the smaller powder. A decrease in initial porosity from 0.49 to 0.40 caused an increase in threshold shock energy of about 75% for both powders. At shock energies slightly below the threshold energy, evidence for the reaction of solid Ti and liquid Si was observed in small isolated regions. These regions contained spherical micronodules with the composition of TiSi 2 in Si. The results are compared to those of previous studies reported in the literature, and mechanisms for reaction initiation and the observed threshold values are proposed.

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Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shock wave initiation of the Ti5Si3 reaction in elemental powders

Vreeland

Montilla

Mutz

1997

Journal of Applied Physics

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“…This paper (in conjunction with its companion paper [27]) presents experimental results coupled with characterization and analysis of two metal silicides formed by shock synthesis directed at providing an answer to these questions. It is shown that the mechanism of shock-induced reaction is quite different than conventional solid-state reaction mechanisms for the silicides.…”

Section: Introductionmentioning

confidence: 99%

Shock synthesis of silicides—I. experimentation and microstructural evolution

Vecchio

Meyers

1994

Acta Metallurgica et Materialia

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Abstract--Niobium and molybdenum silicides were synthesized by the passage of high-amplitude shock waves through elemental powder mixtures. These shock waves were generated by planar parallel impact of explosively-accelerated flyer plates on momentum-trapped capsules containing the powders. Recovery of the specimens revealed unreacted, partially-reacted, and fully-reacted regions, in accord with shock energy levels experienced by the powder. Electron microscopy was employed to characterize the partiallyand fully-reacted regions for the Mo-Si and Nb-Si systems, and revealed only equilibrium phases. Selected-area and convergent beam electron diffraction combined with X-ray microanalysis verified the crystal structure and compositions of the reacted products. Diffusion couples between Nb and Si were fabricated for the purpose of measuring static diffusion rates and determining the phases produced under non-shock condition. Comparison of these non-shock diffusion results with the shock synthesis results indicates that a new mechanism is responsible for the production of the NbSi2 and MoSi2 phases under shock compression. At the local level the reaction can be rationalized, for example, in the Nb-Si system under shock compression, through the production of a liquid-phase reaction product (NbSi2) at the Nb-particle/Si-liquid interface, the formation of spherical nodules (~2/zm diameter) of this product through interfacial tension, and their subsequent solidification.

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Materials Issues in Shock-Compression-Induced Chemical Reactions in Porous Solids

Thadhani¹,

Aizawa²

1997

High-Pressure Shock Compression of Solids IV

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Shock synthesis of silicides—II. Thermodynamics and kinetics

Cited by 59 publications

References 12 publications

Shock wave initiation of the Ti5Si3 reaction in elemental powders

Shock wave initiation of the Ti5Si3 reaction in elemental powders

Shock synthesis of silicides—I. experimentation and microstructural evolution

Materials Issues in Shock-Compression-Induced Chemical Reactions in Porous Solids

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