Wednesday, July 26, 2017

White Graphene: It is white but not graphene

White #graphene is the trivial name given to a material called hexagonal boron nitride (hBN). It occurs in several forms, the hexagonal form is the one of primary interest to us. Think of the basic unit of a hexagon that repeats creating a flat sheet, just like graphene, it is another two-dimensional (2D) material. There are some differences though, read on to find out more… Structure In graphene there is a carbon atom at each of the six corners, in hBN there are three boron atoms and three nitrogen atoms alternating at each of the six corners.This hexagonal structure is made possible by a special type of atomic bond called sp2 hybridisation, you can find out more here. This sp2 bonding is very stable and gives the flat sheet its strength and also flexibility. hBN is nearly as strong as graphene. These bonds also allow the transmission of heat through the material and hBN is a very good conductor of heat as a result. Properties As well as conducting heat, graphene and hBN also have very high melting points. Graphene has the highest melting point at over 4000 degrees centigrade and hBN is not far behind at 2800 degrees centigrade. In fact neither material actually melts, they both decompose rather than go through the liquid phase as water would do.Like its sister material, graphene, hBN is a flat sheet of tightly bound atoms that are connected together so closely that they form an impenetrable barrier to gases and liquids. This means that hBN is resistant to chemical attack making it a good candidate material for corrosion resistant coatings. Applications Graphene is permeable to hydrogen ions and it turns out that hBN is too as this research shows. Being permeable to ions is a rather useful property for the electric battery business so it should come as no surprise to find that researchers have found that white graphene electrolytes have found a niche application in batteries where high temperatures would decompose lesser alternatives.

https://investorintel.com/sectors/technology/technology-intel/white-graphene-white-not-graphene/

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