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By Dr.Zhang from Nanjing Normal University | 13 June 2019 | 0 Comments

The boron nitride  perhaps can beat the heat in electronics!

The boron nitride  perhaps can beat the heat in electronics!
What is boron nitride?
Boron nitride is a refractory compound of boron and nitrogen, whose chemical formula is BN. It exists in different crystal forms, with electrons like carbon lattices that have similar structures. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorph, so it is used as lubricant and cosmetic additive. Cubic (sphalerite structure) similar to diamond is called c-BN; it is softer than diamond, but it has superior thermal and chemical stability. The rare wurtzite BN modification is similar to lonsdaleite and may even be harder than cubic form.
Boron nitride ceramics have traditionally been used as high temperature equipment components due to their good thermal and chemical stability. Boron nitride has potential applications in nanotechnology. BN nanotubes can be similar in structure to carbon nanotubes, i.e. self-rolled graphene (or BN) sheets, but with very different properties.
Three common crystal forms of boron nitride
  • Wurtzite Boron Nitride(w-BN)
Wurtzite boron nitride is even harder than diamond and can only be produced by shock compression, such as explosion or static compression at high pressure.Because of the high hardness of w-BN material, it is suitable for producing knives and blades, grinding tools and polishing.
  • Cubic Boron Nitride (CBN)
Cubic boron nitride, commonly known as boron nitride, is a man-made synthetic abrasive. CBN is made of cubic boron nitride particles bonded by ceramic materials. It is as hard as diamond on the Mohs scale and is well suited to the black material used in grinding operations because it does not carbonize when interacting with iron (Fe), while diamond abrasive materials may carbonize. In general, CBN is used to grind 52100 bearing steel, cast iron, die steel, tool steel, stellite, super alloy, and in some cases ceramic materials.
  • Hexagonal Boron Nitride(HBN)
Having a graphene-like sp2 covalent bond honeycomb structure, hexagonal boron nitride also known as "white graphene". The h-BN monolayer has a layered structure which is also similar to graphene.
The hexagonal crystal structure of boron nitride is one of the three crystal forms of boron nitride. At room temperature and pressure, BN crystals are hexagonal. It is the most stable of the three crystal forms. At higher temperature and pressure, h-BN is converted to wurtzite structure.
The h-BN is generally considered as an insulator and is used as a sub-layer material for any other two-dimensional electronic device. However, it has exotic photoelectronic properties, mechanical robustness, high thermal conductivity and chemical inertness. It was later confirmed to have an indirect band gap, so it is also seen as a semiconductor.
Latest research shows that boron nitride can beat the heat in electronics
A nanocomposite developed at Rice University’s brown school of engineering promises to be a high-temperature dielectric material for flexible electronics, energy storage and electronic devices.
The nanocomposite consists of one-dimensional polymer nanofibers and two-dimensional boron nitride nanosheets. Nanofibers enhance the properties of self-assembled materials, while nanosheets, "white graphene", provide a heat-conducting network that can withstand heat from breaking down ordinary media, polarized insulators in batteries, and other devices that separate positive and negative electrodes.
"When we combine polymer nanofibers with boron nitride, we have a material that has excellent mechanical properties, thermal stability and chemical stability," the researcher lachman said. He says boron nitride is an electrical insulator, but it disperses heat well.
Researchers say the material, which is 12 to 15 microns thick, can efficiently absorb heat up to 250 degrees Celsius (482 degrees Fahrenheit). Experiments show that polymer nanofibre-boron nitride composites can dissipate heat four times more efficiently than single polymers.


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