COMBUSTION SYNTHESIS UNDER MICROGRAVITY CONDITIONS (COSMIC)
Research Area: Combustion Science
Expedition(s): 5
Principal Investigator(s): ● Ludo Froyen, Katholike Universiteit, Leuven, Belgium
RESEARCH OBJECTIVES
COmbustion Synthesis Under
MIcrogravity Conditions
(COSMIC) studies the
microstructure formation of
aluminum-titanium-boron (Ti-Al-
B) compressed powder samples
during self-propagating high-
temperature combustion
synthesis (SHS). Within the
combustion zone, a number of
gravity-dependent phenomena
occur including the convection of
molten components, buoyancy of
inert solid particles, droplet
coalescence, and densification of liquid products. Under certain conditions, gravity-dependent
secondary processes may also occur in the heat-affected zone several minutes after
combustion.
RESULTS
COSMIC focused on the synthesis of intermetallic matrix composites (IMCs) based on the Al-Ti-B
system. Depending on the composition, different intermetallic compounds (TiAl and TiAl 3 ) can
be formed as matrix phase while TiB 2 represents the reinforcing particulate phase. During the
International Space Station mission, all 6 sample reactors with a relatively high “green,” or
unreacted, density of 65% theoretical density (TD) were successfully processed. It was
concluded that reaction depths increased as the molar ratio of intermetallic component (Ti-Al)
over the boride component (Ti-B) was increased. X-ray analyses showed that in some cases, the
samples consisted of a reacted (liquefied) zone and a sintered (charred but not molten) part.
Combustion front propagated relatively slower as the amount of aluminum in the mixture
increases. This result confirmed the corresponding decrease in self-generated heat and system
reactivity relative to the higher aluminum content in the mixture.
PUBLICATION(S)
Orru R, Licheri R, Locci A.M, et al. Self-propagating combustion synthesis of intermetallic matrix
composites in the ISS. Microgravity Science and Technology. 2007;19(5-6):85-89. doi:
10.1007/BF02919459.
This investigation is complete and all results are published.
Snapshots of a combustion synthesis process, including the ignition
stage and the movement of the combustion wave through the formed
pellet. Institute of Structural Macrokinetics, Russian Academy of
Sciences image.