Temperature-dependent frictional properties of ultra-thin boron nitride nanosheets (original) (raw)
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Adhesion and size dependent friction anisotropy in boron nitride nanotubes
Nanotechnology, 2012
The frictional properties of individual multiwalled boron nitride nanotubes (BN-NTs) synthesized by chemical vapor deposition (CVD) and deposited on a silicon substrate are investigated using an atomic force microscope tip sliding along (longitudinal sliding) and across (transverse sliding) the tube's principal axis. Because of the tube transverse deformations during the tip sliding, a larger friction coefficient is found for the transverse sliding as compared to the longitudinal sliding. Here, we show that the friction anisotropy in BN-NTs, defined as the ratio between transverse and longitudinal friction forces per unit area, increases with the nanotube-substrate contact area, estimated to be proportional to (LNT ·RNT ) 1/2 , where LNT and RNT are the length and the radius of the nanotube, respectively. Larger contact area denotes stronger surface adhesion, resulting in a longitudinal friction coefficient closer to the value expected in absence of transverse deformations. Compared to carbon nanotubes (C-NT), BN-NTs display a friction coefficient in each sliding direction with intermediate values between CVD and arc discharge C-NTs. CVD BN-NTs with improved tribological properties and higher oxidation temperature might be a better candidate than CVD C-NTs for applications in extreme environments.
Mechanical properties of atomically thin boron nitride and the role of interlayer interactions
Nature communications, 2017
Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example...
Collision and dynamic frictional properties of boron nitride nanotubes
Applied Physics Letters, 2013
Collision and dynamic frictional properties of boron nitride nanotubes (BNNTs) are of importance to their structural applications related to impact protection. In this paper, we present an experimental study of the lateral collision between moving atomic force microscopy probe tips and individual standstill BNNTs. Our results reveal that increasing the impact velocity results in a more prominent increase of the collision force at low velocity levels. This observation is ascribed to the opposite influences of the impact velocity on the dynamic frictional force and the contact angle on the tip-tube collision contact. V
Thermal-induced irreversible straining of ultrathin boron nitride nanosheets
Applied Physics Letters
We investigate the thermal-induced mechanical deformations in mono-and few-layer hexagonal boron nitride nanosheets (BNNSs) on flat silicon dioxide substrates by using atomic force microscopy and Raman spectroscopy techniques. The measurements reveal that the deformation of thin BNNS follows the reversible expansion/contraction of the substrate at relatively low temperatures. Irreversible deformations in BNNS are observed at elevated temperatures, which are attributed to interfacial sliding on the BNNS-substrate interface that is caused by the temperature-dependent thermal expansion mismatch of BN and substrate materials. Monolayer BNNS is found to possess the highest onset temperature of irreversible straining, which decreases with an increase in the BNNS thickness. The interfacial load transfer characteristics of the BNNS-substrate interface are quantitatively investigated using a micromechanics model. The analysis reveals that monolayer BNNS possesses a maximum interfacial shear strength of about 28.38 MPa on its binding interface with substrates at about 525 C. The findings are useful to better understand the fundamental structural and mechanical properties of BNNS and in pursuit of its applications, in particular, those involved with high temperature processing and/or working environments.
Negative Friction Coefficients in Superlubric Graphite–Hexagonal Boron Nitride Heterojunctions
Physical Review Letters
Negative friction coefficient, where friction is reduced upon increasing normal load, is predicted for superlubric graphite/hexagonal boron nitride heterojunctions. The origin of this counterintuitive behavior lies in the load-induced suppression of the moiré superstructure out-of-plane distortions leading to a less dissipative interfacial dynamics. Thermal induced enhancement of the out-of-plane fluctuations leads to unusual increase of friction with temperature. The highlighted frictional mechanism is of general nature and is expected to appear in many layered materials heterojunctions.
Bending and interlayer shear moduli of ultrathin boron nitride nanosheet
Journal of Physics D: Applied Physics
We investigate the bending rigidity of ultrathin hexagonal boron nitride nanosheet (BNNS) through quantifying its self-folded conformations on flat substrates by using atomic force microscopy and atomistic simulations. The bending stiffness of two to six layers of BNNS is found to follow a power function of its thickness with a power index of ~2.35 and is substantially higher than that of comparable graphene. In contrast, monolayer graphene possesses a higher stiffness than its h-BN counterpart. We attribute the high bending stiffness of multilayer BNNS to its partially ionic B-N bondings and corrugated electronic structures, which result in one order of magnitude stronger interlayer shear interaction in h-BN than in graphene. The higher out-of-plane bending and interlayer shear rigidities suggest that unlike graphene, BNNS is less prone to interlayer delamination-induced structural inhomogeneities (e.g. shearing, rippling and kinks) and thus is suitable as a building block for atomically thin electronics and a reinforcing filler for nanocomposites.
2021
The interlayer adhesion in the multilayered micro-devices is of significant importance for their electronic properties. The scratch adhesion test is applied here using a micro-blade sliding under a linearly increased load, combined with optical and SEM visualization, to study the Al2O3/GR/SiO2/Si and Al2O3/hBN/GR/SiO2/Si stacks. The failure of the interlayers is determined by the critical load at which a sudden change in the coefficient of friction or a jump in the contact acoustic emission signal is observed during the scratch. It was found that the hBN/GR bilayer deposited on SiO2 enhanced significantly (~30%) the critical load of the GR/SiO2 interfacial failure compared to that of the GR monolayer. The adhesion at the upper Al2O3/hBN, hBN/GR and Al2O3/GR layers in the stack was improved by 11–15%, due to the thermal annealing, associated with enhanced solid-state diffusion at the interfaces. While the annealing has insufficient effect on the adhesion at the substrate SiO2/Si laye...
A quantitative study of the nano-scratch behavior of boron and carbon nitride films
Diamond and Related Materials, 2003
The nano-scratch tests of amorphous boron and carbon nitride films prepared by r.f. magnetron sputtering onto c-Si (0 0 1) substrates, at room temperature, were performed by a Nano Indenter XP system with a lateral-force measuring attachment. The films' hardness and elastic modulus were determined by nanoindentation employing continuous stiffness measurements. Low load (2-20 mN) scratch tests were used to evaluate the scratch resistance and the friction coefficient of the films. The scratch process was analyzed into two regimes, that is fully elastic recovery and plastic deformation of the films, depending on the increase of the ramping load and the maximum normal load applied during test. A load dependent transition was found in both the scratch and friction responses. A mixed elastic-plastic behavior was identified for both the BN and CN films, with the elastic x x deformation to be dominant. No delamination of the films tested in this work was observed supporting their potentiality in applications where both wear resistance and elasticity are required. ᮊ
Atomic-force-microscope study of contact area and friction on NbSe_ {2}
1997
We have used an ultrahigh vacuum atomic-force microscope to study the variation in contact radius and friction with applied force between a silicon tip and a NbSe 2 sample. The data are compared to the Maugis-Dugdale theory, which is the appropriate continuum mechanics model for the properties and size of the tip-sample contact. The lateral stiffness of the tip-sample contact is related to the radius of the tip-sample contact through the shear moduli of the materials and we have used this relationship to measure directly the variation in contact radius with applied load. The contact radius measured in this way is found to be in agreement with the Maugis-Dugdale theory using the bulk values of the shear moduli. We also measured the variation in friction force with applied load using the same silicon tip. The variation in friction force with applied normal force is found to follow the variation of the contact area as predicted by the Maugis-Dugdale theory ͓D. Maugis, J. Colloid Interface Sci. 150, 243 ͑1992͔͒, which supports the hypothesis that for a single asperity contact, the frictional shear stress is constant. The value of the shear stress is found to be Ϸ6ϫ10 8 N/m 2 , which is comparable to the estimated theoretical shear strength of NbSe 2. ͓S0163-1829͑97͒05916-X͔
Scientific Reports, 2017
The origin of ultra-low friction exhibited by heterogeneous junctions of graphene and hexagonal boron nitride (h-BN) is revealed. For aligned interfaces, we identify a characteristic contact size, below which the junction behaves like its homogeneous counterparts with friction forces that grow linearly with the contact area. Superlubricity sets in due to the progressive appearance of Moiré patterns resulting in a collective stick-slip motion of the elevated super-structure ridges that turns into smooth soliton-like gliding with increasing contact size. Incommensurability effects are enhanced in misaligned contacts, where the friction coefficients further drop by orders of magnitude. Our fully atomistic simulations show that the superlubric regime in graphene/h-BN heterostructures persists up to significantly higher loads compared to the well-studied twisted homogeneous graphene interface. This indicates the potential of achieving robust superlubricity in practical applications using...