SYSTEMS%20FOR%20SHOCK-ASSISTED%20AND%20DETONATION-DRIVEN%20SYNTHESIS:%20REACTIVITY%20OF%20Ti

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SYSTEMS FOR SHOCK-ASSISTED AND DETONATION-DRIVEN
SYNTHESIS REACTIVITY OF Ti? POWDER MIXTURES
V. A. Veretennikov
Institute of Structural Macrokinetics and
Materials Science, Chernogolovka, Moscow, 142432
Russia e-mail veret_at_ism.ac.ru
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• As is known 1,2, a prerequisite for gasless
  detonation in media with positive coefficient of
  thermal expansion is either a non-zero
  isobaric-isochoric thermal effect of reaction
  (QP,V ? 0) or physically equivalent positive
  volume change at constant pressure P and enthalpy
  H (?VP,H ? 0). However the reaction rate also
  becomes a necessary condition for detonation when
  we deal with charges of finite dimensions.
• This work aimed at elaborating a method for
  reliable estimation of reactivity (reaction rate)
  of metalnonmetal powder mixtures as candidate
  systems for self-sustained gasless detonation.
• The experimental data 3 on high-temperature
  reaction of Ti pow-der (mean particle size 65 µm)
  with crystalline flake graphite were obtained by
  the technique of current-induced thermal
  explosion 4,5. Upon reaction ignition at 1300
  K, the evolution of the sample temperature has
  been recorded with a high time resolution. Within
  the temperature range 15002000 K, the reaction
  rate was found to change by as much as a factor
  of ten.

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• The reaction rate (dT/dt) was found to be
  proportional (in terms of the approach suggested
  in 6) to a set of structural characteristics of
  flake graphite that can be determined
  experimentally (see the Table). The empirical
  expression for this set of structural parame-ters
  Kr can be written in the form
• where Cg is the extent of graphitization, ? the
  fraction of graphite-like carbon, ?x the
  texturization factor (ordering of crystallites in
  a flake), La and Lc the size of crystallites
  along the ? and ? axes, d002 the interlaminar
  separation in a crystallite, dg1 and dg2 the
  interpla-nar spacing in ideal graphite and
  turbostratic pyrocarbon (3.354 and 3.44 Å,
  respectively).

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Brand dT/dt, K s1 Cg M Tx La, Å Lc, Å d002, Å Kr
P-514 6.3?104 0.80 0.76 6.85 57 24 3.64 10.08
267-Thermox 3.6?104 0.93 0.74 5.33 68 26 3.64 8.58
P-603 1.1?104 0.83 0.75 6.10 65 26 3.62 8.35
268-Thermox 4.8?103 0.29 0.31 10.3 73 12 3.77 7.41
Cg extent of graphitization ?
fraction of graphite-like carbon ?x
texturization factor (ordering of crystallites in
a flake) La, Lc size of crystallites along
the ? and ? axes d002 interlaminar
separation in a crystallite dg1, dg2 interplanar
spacing in ideal graphite and turbostratic
pyrocarbon (3.354 and 3.44 Å, respectively)
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Figure shows the linear interpolation plot
ln(dT/dt)Kr. In essence, this plot reflects the
exponential dependence of reation rate on the
structure of carbon material. Physical meaning of
this observation still remains unclear.
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References

• A.S. Shteinberg, V.A. Knyazik, V.E. Fortov. 1994.
  On the Feasibility of Gasless Detonation in
  Condensed Systems. Dokl. Akad. Nauk 336(1) 71.
• Yu.A. Gordopolov, V.S. Trofimov, A.G. Merzhanov.
  1995. On the Feasibility of Gasless Detonation in
  Condensed Systems. Dokl. Akad. Nauk 341(3) 327.
• V.A. Veretennikov, S.E. Zakiev, V.T. Popov, K.V.
  Popov. 2002. Mesostructure of carbon black and
  reactivity of TiC mixtures. Probl. Materialoved.
  1(29) 403.
• V.A. Knyazik, A.E. Denisenko, E.A.
  Chernomorskaya, A.S. Shteinberg. Automated
  Apparatus for Investigating SHS Kinetics. 1991,
  Prib. Tekh. Eksper., (4) 164.
• K.V. Popov, V.A. Knyazik, A.S. Shteinberg. 1993.
  High-temperature reaction of Ti with B as studied
  by current-induced thermal explosion technique.
  1993. Fiz. Goeniya Vzryva 29(1) 82.
• A.A. Zenin, Yu.M. Korolev, V.T. Popov, Yu.V.
  Tyurkin. 1986. Non-isothermal carbonization of
  titanium. Dokl. Akad. Nauk SSSR 287(1) 111.