High resolution transmission electron microscopy of the planar defect structure of hexagonal boron nitride

Abstract

Basal plane stacking disorder, delamination cracks, misorientation bands and low angle (0001) twist boundaries are observed by high resolution transmission electron microscopy in small, highly defective, boron nitride inclusions introduced unintentionally in silicon nitridesilicon carbide composites during the fabrication process. The delamination cracks are produced as a consequence of the magnitude of the thermal stresses introduced during cooling from the consolidation temperature and the layered nature of the hexagonal boron nitride crystal structure. Detailed consideration of the misorientation bands shows that, while the majority can be safely described as kink bands, there are a number of examples where the geometry is strikingly similar to the geometry of deformation twinning in hexagonal boron nitride.

Review of advances in cubic boron nitride film synthesis

“…In nanocrystalline specimens such as cBN films, the tilt orientation of individual crystallites is quite difficult to experimentally control. As an example, a tilt rotation as small as 20 mrad about the c axis of hBN is sufficient to obliterate the ( lOi0) contrast [82] leaving only the (0002) fringes visible. Additional image artifacts may arise from overlapping crystallites and variations in specimen thickness5 For many geometries.…”

“…For the graphitic boron nitride material, the basal plane fringes (d= 3.3 A) are easily resolved. Additionally, if graphitic material is oriented along a (2]iO)-type direction it is often possible to resolve the in-plane periodicities corresponding to the zigzagging chains of alternating boron and nitrogen atoms that run parallel to this direction and which are spaced by 2.17 A [81,82]. For hBN, the resulting intensity peaks are directly aligned above each other and correspond to { 1010) fringes; in rBN the peaks are staggered in an A B C... sequence and correspond to { lOi } fringes.…”

Investigation of the Physical and Mechanical Properties of Hot‐Pressed Boron Nitride/Oxide Ceramic Composites

“…These improvements may be due to microcracks that exist between basal planes in h-BN. [9][10][11] h-BN can also be used as a weak interface between layers 12 or filaments 13,14 of silicon nitride. However, recent research has shown that interfaces created with BN powders often include a secondary phase.…”

Micro-Kinking of the Long-Period Stacking/Order (LPSO) Phase in a Hot-Extruded Mg₉₇Zn₁Y₂ Alloy

“…4(a). 21) In fact, such microcracks have been frequently observed for several kink-deformed materials, e.g., hexagonal-BN, 22) SiC 23) and Ti 3 SiC 2 . 24) For the LPSO crystals, however, occurrence of microcracks seem to be effectively suppressed by generating the arrays of cA-dislocation, as illustrated in Fig.…”