Mechanical activation assisted self-propagating high- temperature synthesis of Si/Al2O3composites

In situ synchrotron studies of structure and phase formation dynamics in mechanically activated (t = 7 min, power density 40 g) and mechanically activated with subsequent irradiation by γ-quanta 60Co powder mixture (Ti 64 wt% + Al) during high-temperature synthesis by the method of thermal explosion using induction heating are described. In situ high-temperature synthesis was carried out on the created experimental complex adapted for synchrotron X-ray diffraction methods. The sequence of formation and time–temperature interval of the metastable and main phases were determined. The impact of preliminary mechanical activation and of γ-irradiation on the macrokinetic parameters of the synthesis were studied experimentally in situ. It has been established that the impact of γ-irradiation on the mechanically activated powder mixture of the composition Ti 64 wt% + Al leads to a change in the thermal parameters of combustion: the maximum synthesis temperature and the burning rate decrease. The heating rate for the non-irradiated mixture is 204.8 K s−1 and that for the irradiated mixture is 81.6 K s−1. The dependences of mass fractions of the synthesized compounds on time and temperature were calculated from the stage of preheating until completion of the thermal explosion. A single-phase equilibrium product of the composition γ-(TiAl) is formed in γ-irradiated mechanically activated mixture when the system reaches maximum temperature. The synthesized product of the mechanically activated mixture without γ-irradiation contains 72% γ-(TiAl); TiAl3 (26%) and residual Ti (2%) are also observed.

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Ultrafine Si/Al2O3 composites obtained by combining methods of mechanical activation and self-propagating high-temperature synthesis

Combustion Explosion and Shock Waves ◽

10.1007/s10573-010-0006-8 ◽

2010 ◽

Vol 46 (1) ◽

pp. 36-40 ◽

Cited By ~ 1

Author(s):

T. F. Grigorieva ◽

T. L. Talako ◽

M. R. Sharafutdinov ◽

Yu. D. Kaminskii ◽

I. A. Vorsina ◽

...

Keyword(s):

High Temperature ◽

Mechanical Activation ◽

Temperature Synthesis ◽

High Temperature Synthesis ◽

Combining Methods

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On the Physicochemical Mechanism of the Influence of Preliminary Mechanical Activation on Self-Propagating High-Temperature Synthesis

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.138.159 ◽

2008 ◽

Vol 138 ◽

pp. 159-164 ◽

Cited By ~ 6

Author(s):

Boris B. Khina ◽

Boleslaw Formanek

Keyword(s):

High Temperature ◽

Mechanical Activation ◽

Cold Work ◽

Temperature Synthesis ◽

High Temperature Synthesis ◽

State Diffusion ◽

Physicochemical Mechanism ◽

Charge Mixture ◽

Phase Intermetallic ◽

A Charge

The analysis of physicochemical mechanism of the influence of mechanical activation (MA) of a charge mixture on the subsequent self-propagating high-temperature synthesis (SHS) of intermetallic compounds is performed. Numerical estimates have revealed an insignificant role of the energy stored in solid reactants due to cold work during MA. The characteristic time of relaxation of non-equilibrium vacancies, which were generated in metals by MA, during heating in the SHS wave is estimated, and their insignificant influence on the reaction kinetics at high temperatures is demonstrated. It is shown that a strong effect of preliminary MA on SHS can be attributed only to deformation-enhanced solid-state diffusion during MA, which can lead to the formation of a supersaturated solid solution and thus affect the conditions for nucleation of a product phase (intermetallic compound) upon heating.

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Mechanical Activation as a New Method for SHS

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.45.979 ◽

2006 ◽

Vol 45 ◽

pp. 979-988 ◽

Cited By ~ 10

Author(s):

Frédéric Bernard ◽

Sébastien Paris ◽

Eric Gaffet

Keyword(s):

High Temperature ◽

Mechanical Activation ◽

Combustion Front ◽

Front Velocity ◽

Thermal Heating ◽

Temperature Synthesis ◽

High Temperature Synthesis ◽

End Products ◽

Elemental Powder Mixture ◽

Short Time

The use of mechanical activation (the elemental powder mixture is milled for a short time at given frequency and impact energy) as a precursor to self-propagating high-temperature synthesis (SHS) results in the formation of nanostructured porous materials. The mechanical activation step was found necessary (i) to modify the thermal parameters of the combustion front (i.e. combustion front velocity, thermal heating rate…) in the cases of Mo-Si, Fe-Al, Ni-Si (ii) to initiate a combustion front in the case of systems having a low exothermicity. Nevertheless, the control of the mechanically activated mixture characteristics and, the understanding of the mechanical activation role on the SHS parameters are essential to produce end-products with expected microstructure.

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