Carbon nanotubes and related nanostructures, including nanosheets have attracted tremendous attention for their unique structures and intriguing properties. These nanomaterials have been widely investigated—from theory, synthesis, and characterization to applications in electronic devices, energy generation and storage, biological and chemical sensors, etc. In addition, non-carbon nanostructures such as nanotubes and nanosheets of boron nitride (BN) have gained increasing interest. To facilitate scientific interaction among students and researchers on the latest advancements in this area, Symposium MM – Nanotubes and Related Nanostructures, was organized and held on Apr. 21–25 at the 2014 MRS Spring Meeting in San Francisco, California. The symposium organizers were Don Futaba (National Institute of Advanced Industrial Science and Technology), Annick Loiseau (Laboratoire d’Etude des Microstructures), Yoke Khin Yap (Michigan Technological University), and Ming Zheng (National Institute of Standards and Technology). This proceedings volume consists of peer-reviewed papers presented in the symposium, including invited and contributed presentations. These papers represent a snapshot of topics discussed in both theoretical and experimental aspects. We hope this publication will contribute toward productive research in the area of nanotubes and related nanostructures.
Category: Boron Nitride
Boron nitride nanotubes grown just like carbon nanotubes
Boron nitride nanotubes (BNNTs) have extraordinary mechanical properties ideal as reinforcements in composites and offer the possibility of a tunable band gap for electronic applications. But synthesizing BNNTs has proven difficult, with current methods requiring high temperatures, special-ized instrumentation and producing nanotubes of low quality contaminated with impurities. Now researchers from Michigan Technological University believe they have changed all this using an approach that makes the growth of BNNTs as simple and convenient as carbon nanotubes [C.H. Lee et al., Chem. Mater. (2009), doi:10.1021/cm903287u]. Using catalytic chemical vapordeposition (CCVD) at 1200 ◦C with MgO, Ni or Fe catalysts, Yoke Khin Yap and his team have achieved patterned growth of BNNTs directly on Si substrates for the first time
Diameter-Dependent Bending Modulus of Individual Multiwall Boron Nitride Nanotubes
The mechanical properties of individual multi-wall boron nitride nanotubes (MWBNNTs) synthesized by a growth-vapor-trapping chemical vapor deposition method are investigated by a three-point bending technique via atomic force microscopy. Multiple locations on suspended tubes are probed in order to determine the boundary conditions of the supported tube ends. The bending moduli (EB) calculated for 20 tubes with diameters ranging from 18 to 58 nm confirm the exceptional mechanical properties of MWBNNTs, with an average EB of 760 ± 30 GPa. For the first time, the bending moduli of MWBNNTs are observed to increase with decreasing diameter, ranging from 100 ± 20 GPa to as high as 1800 ± 300 GPa. This diameter dependence is evaluated by Timoshenko beam theory. The Young’s modulus and shear modulus were determined to be 1800 ± 300 and 7 ± 1 GPa, respectively, for a trimmed data set of 16 tubes. The low shear modulus of MWBNNTs is the reason for the detected diameter-dependent bending modulus and is likely due to the presence of interwall shearing between the crystalline and faceted helical nanotube structures of MWBNNTs.
First-principles study of strain-induced modulation of energy gaps of graphene/BN and BN bilayers
First-principles calculations based on density functional theory are performed on graphene/BN and BN bilayers to investigate the effect of the strain on their energy gaps. For the graphene/BN bilayer, the bands have characteristic graphenelike features with a small band gap at K. Application of strain modulates the band gap, whose magnitude depends on the strength of interaction between constituent monolayers. For the BN bilayer, on the other hand, a large band gap is predicted, which remains nearly the same for small strains. The increased inhomogeneity in charge density of different carbon sublattices due to a stronger interplanar interaction is the cause of the predicted variation in the band gap with strains applied along the perpendicular direction in the graphene/BN bilayer.
Field emission and strain engineering of electronic properties in boron nitride nanotubes
FE-and-Electronic-strains-Nanotech2012
The electrical properties of boron nitride (BN) nanostructures, particularly BN nanotubes (NTs), have been studied less in comparison to the counterpart carbon nanotubes. The present work investigates the field emission (FE) behavior of BNNTs under multiple cycles of FE experiments and demonstrates a strain-engineering pathway to tune the electronic properties of BNNTs. The electrical probing of individual BNNTs were conducted inside a transmission electron microscope (TEM) using an in situ electrical holder capable of applying a bias voltage of up to 110 V. Our results indicate that in the first cycle a single BNNT can exhibit the current density of ∼1 mA cm−2 at 110 V and the turn-on voltage of 325 V μm−1. However, field emission properties reduced considerably in subsequent cycles. Real-time imaging revealed the structural degradation of individual BNNTs during FE experiments. The electromechanical measurements show that the conductivity of BNNTs can be tuned by means of mechanical straining. The resistance of individual BNNTs reduced from 2000 to 769 M and the carrier concentration increased from 0.35 × 1017 to 1.1 × 1017 cm−3 by straining the samples up to 2.5%.
Functionalization, Dispersion, and Cutting of Boron Nitride Nanotubes in Water
High-quality boron nitride nanotubes (BNNTs) were functionalized for the first time with water-soluble and biocompatible PEGylated phospholipid [methoxy-poly(ethylene glycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N conjugates (mPEG-DSPE)]. We found that BNNTs can be suspended in water for more than 3 months without precipitation. By comparing the dispersion stability of mPEG-DSPE/BNNTs in various solvents and the related Hansen solubility parameters, we found that polarized and hydrogen bonds between water and the hydrophilic mPEG play important roles in maintaining stable dispersion of BNNTs and preventing aggregation of mPEG-DSPE/BNNTs in the solutions. This has led to the formation of composite films with well-dispersed BNNTs and the coating of self-assembled monolayer (SAM) BNNTs. Furthermore, the lengths of these functionalized BNNTs can be shorterned, for the first time, from >10 μm to ∼500 nm by ultrasonication. Experiments suggest that effective dispersion of BNNT in solution is necessary for such cutting, where effective energy transfer from the sonicator to nanotubes is achieved. Our results will form the basis for stable functionalization, dispersion, and effective cutting of BNNTs with water-soluble and biocompatible PEGylated phospholipid, which are important for biomedical and composite applications.
Growth of adhesive cubic phase boron nitride films without argon ion bombardment
Previously, in situ bombardment of massive ions (Ar+, Kr+, etc.) was considered to be necessary for the formation of c-BN films. Because of
the accumulated stress, bombardment of massive ions has led to the formation of c-BN films with poor adhesion. Here we show that c-BN films
can be grown without involving bombardment of massive ions. This is achieved by using plasma-assisted pulsed-laser deposition (PLD) in pure
N2 RF plasma. Furthermore, we show that c-BN films can be grown in a vacuum ( ̈105 mbar during growth) by PLD without auxiliary ion
source. We show that these are possible at a reduced deposition rate. Energetic growth species initiated by PLD and the pure N2 plasma is
sufficient to form adhesive c-BN films at moderate deposition rate as long as the energy transfer rate per growth species is sufficient.
D 2005 Elsevier B.V. All rights reserved.
Superhydrophobicity of Boron Nitride Nanotubes Grown on Silicon Substrates
BNNTs-Superhydrophopicity-Langmuir2009
Langmuir, good images, SEM, Scanning Electron Microspy
Effective growth of boron nitride nanotubes by thermal chemical vapor deposition
good images, quartz, coating
Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates
Electron Microscopy, Argonne National Laboratory, good images, coating