Effect of shock pressure and plastic strain on chemical reactions in NbSi and MoSi systems

Time-resolved measurements of the shock-compression response of Mo+2Si elemental powder mixtures

“…1,[3][4][5]7 Thermochemical mechanisms including liquidphase reactions, founded on the observation of localized melts ͑or ''hot spots''͒ at interparticle regions have also been proposed. 14 Consequently, the observation of reaction products in recovered compacts, during post mortem microstructural analysis ͑similar to those observed by Meyers et al, 8,13 Marquis and Batsanov, 9 Montilla, 12 and Aizawa 15 ͒, cannot provide information on whether the observed reaction may have occurred due to ''shock-assisted'' or ''shock-induced'' conditions. In such highly exothermic powder mixtures, ''shock-assisted'' chemical reactions can also occur in shock-compressed powder compacts because of bulk shock temperature increases in the time scales of temperature equilibrium.…”

“…6 Shock initiation of chemical reactions in highly reactive powder mixtures has been proposed to occur as a consequence of mechanochemical effects, via processes involving solid-state configurational changes and structural rearrangements. [8][9][10][11][12][13] The highly exothermic nature of Mo-Si powder mixtures (⌬H R ϭϪ31.5 kcal/mol for MoSi 2 ; Ϫ74.5 kcal/mol for Mo 5 Si 3 ) and the large differential in flow strength, density, and melt temperature between Mo and Si (⌬ y ϳ230 MPa, ⌬ϭ7.9 g/cm 3 , and ⌬T m ϭ800°C) make this an ideal system for investigating the effects of shock compression. [8][9][10][11][12][13] The highly exothermic nature of Mo-Si powder mixtures (⌬H R ϭϪ31.5 kcal/mol for MoSi 2 ; Ϫ74.5 kcal/mol for Mo 5 Si 3 ) and the large differential in flow strength, density, and melt temperature between Mo and Si (⌬ y ϳ230 MPa, ⌬ϭ7.9 g/cm 3 , and ⌬T m ϭ800°C) make this an ideal system for investigating the effects of shock compression.…”

Sensing of shock-wave velocity and pressure using shock-wave induced mechanoluminescence of crystals

“…This term is relatively broad and it covers any type of shock-induced change such as phase-transformations, formation of lattice defects, decomposition reactions and resultant changes in physical and chemical properties of materials. Using spectroscopic techniques, X-ray diffraction, and optical microscopy a great diversity of natural shock effects has been reported till now [1][2][3][4][5][6][7][8][9][10]. The physical nature of some of the effects was not completely understood and others were not even known to researchers until transmission electron microscope (TEM) was used to characterize the mineralogical effects at the nanometer range .…”

Investigation of “shock-induced” and “shock-assisted” chemical reactions in Mo + 2Si powder mixtures

“…Hence, the threshold conditions, kinetics, and mechanisms corresponding to each type of reaction can be studied by correlating the observed reaction products with calculated shock loading conditions. Shock synthesis studies on MoSi performed by Meyers et at., [7,22] Marquis and Batsanov, [8] Montilla, [11] and Aizawa and Yen [23] have eluded to various reaction mechanisms based on characteristics of observed reaction products. In experiments performed by Meyers et al [7,22] on Mo-Si powders using the double cylinder implosion geometry, a central fully reacted region (of eutectic microstructure) surrounded by both partially reacted (MoSi 2 spherules) and unreacted regions was observed.…”