Synthesis And Surface Physico-Mechanical Properties Of Hexagonal Boron Nitride And Graphene

Two dimensional atomic crystals have attracted intensive research attentions because of their layered planer structure and unique physico-mechanical properties.The growth and transfer of large area and high quality monolayer graphene and hexagonal boron nitride(h-BN)are the prerequisitefor investigatingtheir macroscopic properties and applications.Here we focus on the functional applications of graphene and h-BN,systematically investigated the controlled growth,coating performance and wettability of h-BN,the gas flow induced voltage in graphene and wave potential in zinc oxide nanofilm.The corresponding findings are briefly summarized as following:1.Controlled growth of monolayer h-BN and its coating performance against friction and oxidation.We systematically investigated the chemical vapor deposition of monolayer h-BN on copper twin crystals.It is found that h-BN prefers to nucleate and grow on twin crystal strips.Introducing oxygen can efficiently suppressthe selectivity,due to the reduced dehydrogenation barrier of precursor molecules with the assistance of oxygen as revealed by density functional theory calculations.Also,we demonstrate that a chemical vapor deposited h-BN monolayer of large area and high quality can serve as a perfect coating to significantly improve friction,oxidation and electric resistance of the substrates.Combining with the exceptional high thermal and chemical stability,the excellent coating performance make the h-BN monolayer a promising coating material of only one atomic thickness.2.Unified wettability of supported monolayer hexagonal boron nitride and graphene in air.We show that the water contact angle of freshly grown h-BN film is nearly independent of the underlying materials as well as the h-BN layer number.First-principles calculations and molecular interaction modeling confirm that a monolayer h-BN can efficiently tune the interaction of a water molecule with different substrates to a converging level.Due to the spontaneously adsorption of airborne hydrocarbon,the contact angle of h-BN and graphene exposed to air increases gradually to a saturated stable value.This saturated value is robust against the variation of several factors,including the material of substrates,layer number of h-BN and ions in solution,facilitating its practical applications.3.Seebeck coefficient and gas-flow-induced voltage of multilayer graphene and waving potential of zinc oxide nanofilms.We revealed that the Seebeck coefficients of 1-8 layered graphene fabricated through transfer-stacking method reach the maximum at hexalayer,which is 1.8 times that of monolayer.The gas flow-induced voltage reaches the maximum at pentalayer,which is 1.9 times that of monolayer.We also demonstrate that moving a transparent flexible Zn O nanofilm across the surface of ionic solutions can generate electricity.It is the first time that waving potential is observed in materials beyond graphene.The generated electricity increases linearly with the moving velocity with an open-circuit voltage up to tens of millivolt and a short-circuit current at the order of microampere.The harvested electricity can be efficiently scaled up through series and parallel connections.Theoretical simulations show that it is the low carrier density and mobility that endow the Zn O nanofilm with the outstanding capacity in harvesting the wave energy.