ISSN:
1551-2916
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Shock synthesis of cubic BN (c-BN) was accomplished using high-velocity thermal spray. Al-8Si-20BN (hexagonal BN, h-BN) composite powders were injected into a high-energy flame where the particles partially melted and accelerated to impact on steel substrates. The shock wave generated by the sudden impact of the droplets propagated through the underlying deposit, which experienced a polymorphic transition to high-pressure forms. Transmission electron microscopy revealed that the deposits contained platelike c-BN embedded in h-BN. The c-BN formed with a specific orientation relation, with (0001) h-BN parallel to (111) c-BN and [11–20] h-BN nearly parallel to [2–20] c-BN. As a result of shock propagation, a number of half-Frank loops with Burgers vector ½[0001] were introduced and thin (∼3 nm) layers of amorphous BN (a-BN), parallel to the (0002) plane, were formed. Significant shearing of the (10–10) plane with respect to the c-axis, delamination, and kink bands were also observed in most of the h-BN grains. The Hugoniot pressure calculation suggested that the impact pressure was sufficient to trigger the nucleation of c-BN.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1151-2916.2002.tb00477.x
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