Boron nitride cones: structure determination by transmission electron microscopy.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Turbostratic boron nitride (BN) is a material with unique structural properties.
• Micrometre-size conically shaped particles are present in certain forms of turbostratic BN.
• Understanding the atomic arrangement in these conical structures is crucial for potential applications.

Purpose of the Study:

• To investigate the structure of turbostratic boron nitride with conical particles.
• To determine the distribution of cone apex angles.
• To propose a structural model explaining the observed morphology.

Main Methods:

• Transmission electron microscopy (TEM) was employed for high-resolution imaging.
• Electron diffraction patterns were analyzed to understand layer correlations.
• Cone apex angles were measured from TEM images.

Main Results:

• Correlations between adjacent boron nitride layers were observed.
• Cone apex angles showed a broad distribution (84–130 degrees) with a peak around 93 degrees.
• A helical structure model with layers wound around a disclination axis was proposed.

Conclusions:

• The helical structure model successfully accounts for the observed conical shapes and angle distributions.
• The clustering of apex angles near 93 degrees is attributed to square ring formation during nucleation.
• This nucleation mechanism appears to be specific to the boron nitride system.