Shock Compression Processing of Powders

Thadhani, Naresh N.

doi:10.1080/10426918808953217

Cited by 19 publications

(6 citation statements)

References 23 publications

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“…Those with a final relative density of 78% were compacted by dynamic magnetic implosion, 11 and those with relative densities of 85% and 95% were compacted by shock-wave implosion techniques. 12 The powders for these samples were 99.999% pure Mo, and 99.999% pure amorphous Si (Cerac) and all were −325 mesh. The dynamic magnetic implosion method utilizes pressures generated from pulsed electromagnetic fields to densify the powders.…”

Section: Experimental Materials and Methodsmentioning

confidence: 99%

Initiation of Self‐Propagating Combustion Waves in Dense Mo + 2Si Reactants through Field‐Activation

Xue

Vandersall

Carrillo-Heian

et al. 1999

Journal of the American Ceramic Society

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Because of kinetic limitations, self-sustaining combustion synthesis reactions cannot be initiated in dense powder compacts. In compacts of Mo + 2Si, self-propagating waves can be initiated in samples with less than 78% relative density. At this and higher densities, no waves could be initiated without field-activation. In the presence of an electric field (at values of 7 and 13 V⅐cm −1 ), reactant compacts with densities up to 95% could sustain a combustion wave to produce MoSi 2 . In the absence of a field (for lowerdensity samples) the wave propagated in a non-steady-state (pulsating) mode, while under the influence of a field the wave propagated in a steady-state mode. The dependences of wave velocity and combustion temperature on the relative density of the reactants were qualitatively similar, showing maxima at a relative density of about 65%. These observations are explained in terms of the contribution of a liquid phase in the MoSi 2 -Mo 5 Si 3 binary to the synthesis kinetics. Although not detected by X-ray diffraction analysis, small amounts of Mo 5 Si 3 were discerned at the grain boundaries of the MoSi 2 product. The particle size of the silicide synthesized from 95% dense reactants was significantly smaller than those synthesized from reactants with lower densities, but the reason for this observation is not well understood at this time.

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Section: Experimental Materials and Methodsmentioning

confidence: 99%

Initiation of Self‐Propagating Combustion Waves in Dense Mo + 2Si Reactants through Field‐Activation

Xue

Vandersall

Carrillo-Heian

et al. 1999

Journal of the American Ceramic Society

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“…The set-up used for the synthesis experiments consists of a steel flyer plate which is explosively accelerated over a lO-20mm stand-off distance and impact powders contained in steel capsules embedded in the cavities of a steel recovery fixture. Impact planarity is achieved via the use of a plane wave shock lens arrangement (Thadhani 1988). The precursor powders were packed at typically ca.…”

Section: Experimental Aspectsmentioning

confidence: 99%

“…Shock waves produced in a gas gun or in an explosive detonation front provide dynamic pressures ranging from 1 to 100 GPa with durations of a few microseconds. Local temperatures in the solid can rise by a few thousand degrees as indicated by two-dimensional simulations for different packing densities (Thadhani 1988). This is followed by extremely fast quench rates of up to 106 K/s which allows the fabrication of metastable or non-equilibrium structures.…”

Section: Introductionmentioning

confidence: 99%

Shock wave synthesis and processing of high temperature superconductors with defect microstructures

et al. 1991

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The tetragonal (T, = 55 KI and orthorhombic (non-superconducting) T12Ba2CuOo (T1220l) phases have been synthesized by a ca 20GPa planar shock wave in a microsecond time frame. Because of local rapid quench rates (up to 106 K/s) defects related to metastable phases are frozen in the sample. In the 2201 phase the predominant defect identified by high resolution lattice imaging corresponds to a TI-Ba-Cu-TI-Cu (TI 1212) phase which is metastable but can be synthesized via a low temperature reaction. Defects of this type may account for the enhanced flux trapping observed in the material using field modulated microwave absorption. Attempts at shock synthesizing the more complex T12Ba2CaCuEO s and TI2Ba2Ca2Cu3Olo phases are also discussed. Shock processing pre-synthesized YBa2Cu30 v powder in the radial geometry followed by an 02 anneal at 890C produces neartheoretical density cylinders that sustain inter-grain critical currents at zero field of 1350 and 750amps/cm 2 at 60 and 77 K respectively. The magnetic field dependence of the critical current and the magnitude of flux-pinning in this material relative to sintered pellets are enhanced by a factor of 2-3. Preliminary investigations of the defect microstructure of this material are discussed.

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“…This stress wave, characterized by a short duration (typically < 1 s), propagates through the material, leading to the compaction and bonding of the powder particles. Thadhani (1988) has demonstrated that the bonding mechanisms in shock compaction involve the rapid and intense concentration of shock energy, preferentially in interparticle regions, resulting in extensive plastic deformation. Although the Split Hopkinson Pressure Bar (SHPB) is usually dedicated to the characterization of solid materials at high strain rates, Häggblad et al (2005) with metallic powder and Trecant et al (1995) with ceramic powder have already tried to use it for cold powder compaction.…”

Section: Introductionmentioning

confidence: 99%

Development of the Dynamic Compaction Resistance Sintering (DCRS): A new process for powder consolidation combining electric current and dynamic loading

Acquier

Lemonnier²,

Allain-Bonnasso³

et al. 2015

Journal of Materials Processing Technology

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Shock Compression Processing of Powders

Cited by 19 publications

References 23 publications

Initiation of Self‐Propagating Combustion Waves in Dense Mo + 2Si Reactants through Field‐Activation

Initiation of Self‐Propagating Combustion Waves in Dense Mo + 2Si Reactants through Field‐Activation

Shock wave synthesis and processing of high temperature superconductors with defect microstructures

Development of the Dynamic Compaction Resistance Sintering (DCRS): A new process for powder consolidation combining electric current and dynamic loading

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