White Graphene

 


2D hexagonal boron nitride (hBN) is called white graphene. It is an important two dimensional material, with exceptional properties as compared to other two dimensional materials.

hBN is a multi-layered material whose structure is kindred to graphene. Inside each layer, it is composed of alternating boron and nitrogen atoms. These atoms are arranged in a sp(2) bonded network. The known bond length between boron and nitrogen is 1.44  A°. The known bond length between carbon atoms in graphene  is 1.42 A °. 

Inside each layer, the boron and nitrogen atoms are held together with strong covalent bonds. However, the layers themselves are held together by a somewhat weak Van Der Waals force. 

Graphene is a semiconductor with a zero-band gap. hBN is an insulator with a large gap band of 5.97 eV. This indicates its potential as a high quality dielectric material. The mismatch of hBN and graphene is only 1.7%. For some reason (yet unknown) hBN opens the bandgap in graphene when it's used as a growth medium. 

hBN displays almost no optical absorption in the visible spectrum. This allows for high transparency, but hBN has absorption spectroscopy in the ultraviolet region. hBN at room temperature displays thermal conductivity of 751 W/mk. This makes it a promising filler for thermal management and heat absorption in electronic devices.  The elastic modulus of hBN is .8 TPa. It has a high strength of about 100GPa. This is comparable to graphene!

It’s exceptional mechanical characteristics has allowed for use in some polymer films. hBN is stable in the air up to 1000°C. It does not react with most chemicals. It is one of the most thinnest coatings ever shown to endure harsh environments!!!


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