2 research outputs found
UHTC composites for hypersonic applications
A dream for
many scientists,
engineers and sci-fi
enthusiasts is of an aerospace
vehicle that can
take off from an airport,
fly through the atmosphere
and travel to the
other side of the earth
at hypersonic speeds,
and then return through
the atmosphere to the
same or another airport.
Thanks to programs
like DARPA’s Falcon
Hypersonic Technology
Vehicle 2 program
(Figure 1), the dream is
taking form
Screw dislocation assisted spontaneous growth of HfB2 tubes and rods
The mechanism of anisotropic growth of HfB2 rods has been discussed in this study. HfB2 powder has been synthesized via a sol–gel-based route using phenolic resin, hafnium chloride, and boric acid as the source of carbon, hafnium, and boron
respectively, though a small number of comparative experiments involved amorphous boron as the boron source. The effects of calcination dwell time and Hf:C and Hf:B molar ratio on the purity and morphology of the final powder have been studied and the mechanism of anisotropic growth of HfB2
has been investigated. It is hypothesized that imperfect oriented attachment of finer HfB2 particles results in screw dislocations
in the coarser particles. The screw dislocation facilitates dislocation-driven growth of particles into anisotropic
HfB2 rods