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High-Efficient Production of Boron Nitride Nanosheets via an Optimized Ball Milling Process for Lubrication in Oil

View Article: PubMed Central - PubMed

ABSTRACT

Although tailored wet ball milling can be an efficient method to produce a large quantity of two-dimensional nanomaterials, such as boron nitride (BN) nanosheets, milling parameters including milling speed, ball-to-powder ratio, milling ball size and milling agent, are important for optimization of exfoliation efficiency and production yield. In this report, we systematically investigate the effects of different milling parameters on the production of BN nanosheets with benzyl benzoate being used as the milling agent. It is found that small balls of 0.1–0.2 mm in diameter are much more effective in exfoliating BN particles to BN nanosheets. Under the optimum condition, the production yield can be as high as 13.8% and the BN nanosheets are 0.5–1.5 μm in diameter and a few nanometers thick and of relative high crystallinity and chemical purity. The lubrication properties of the BN nanosheets in base oil have also been studied. The tribological tests show that the BN nanosheets can greatly reduce the friction coefficient and wear scar diameter of the base oil.

No MeSH data available.


(a) TEM Images of the BN sheets produced by 0.1–0.2 mm balls; (b) the corresponding SAED pattern; (c) and (d) high-magnification TEM images; (e) and (f) TEM images of few-layer BN nanosheets (g) EELS spectra of the BN nanosheet.
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f5: (a) TEM Images of the BN sheets produced by 0.1–0.2 mm balls; (b) the corresponding SAED pattern; (c) and (d) high-magnification TEM images; (e) and (f) TEM images of few-layer BN nanosheets (g) EELS spectra of the BN nanosheet.

Mentions: The crystallinity, thickness and chemical composition of the BN nanosheets produced by ball milling using the 0.1–0.2 mm balls were investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Figure 5a shows a BN nanosheet suspended over a holey carbon supporting film on a TEM grid. Similar to many other investigated BN nanosheets, folds and partial exfoliation are observed. The electron diffraction pattern in Figure 5b shows one set of bright dots and several sets of weaker dots both of a six-fold symmetry. This suggests that the BN nanosheet is still crystalline and the in-plane structure is not damaged, consistent with the XRD results. However, the presence of the sets of weaker diffraction dots discloses that either the stacking of the BN nanosheet is twisted or the existence of folds or incomplete exfoliation. High-resolution TEM image in Figure 5c show the edge of part of the BN nanosheet, indicating a thickness of 2 nm (~6 layers). The highly crystalline nature of the BN nanosheet is confirmed by the HRTEM image in Figure 5d, showing a pattern of lattice dots with a distance of 0.25 nm representing the distance between two adjacent BN hexagonal rings. So the distance between B and N atoms is calculated to be 0.144 nm, typical for hBN crystals. We also found few-layer BN, as shown in Figure 5e and f. The EELS spectrum in Fig. 5g shows the domination of B and N, along with a small amount of carbon. The carbon could come from the residue of benzyl benzoate which is not fully evaporated during TEM sample preparation.


High-Efficient Production of Boron Nitride Nanosheets via an Optimized Ball Milling Process for Lubrication in Oil
(a) TEM Images of the BN sheets produced by 0.1–0.2 mm balls; (b) the corresponding SAED pattern; (c) and (d) high-magnification TEM images; (e) and (f) TEM images of few-layer BN nanosheets (g) EELS spectra of the BN nanosheet.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384281&req=5

f5: (a) TEM Images of the BN sheets produced by 0.1–0.2 mm balls; (b) the corresponding SAED pattern; (c) and (d) high-magnification TEM images; (e) and (f) TEM images of few-layer BN nanosheets (g) EELS spectra of the BN nanosheet.
Mentions: The crystallinity, thickness and chemical composition of the BN nanosheets produced by ball milling using the 0.1–0.2 mm balls were investigated by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Figure 5a shows a BN nanosheet suspended over a holey carbon supporting film on a TEM grid. Similar to many other investigated BN nanosheets, folds and partial exfoliation are observed. The electron diffraction pattern in Figure 5b shows one set of bright dots and several sets of weaker dots both of a six-fold symmetry. This suggests that the BN nanosheet is still crystalline and the in-plane structure is not damaged, consistent with the XRD results. However, the presence of the sets of weaker diffraction dots discloses that either the stacking of the BN nanosheet is twisted or the existence of folds or incomplete exfoliation. High-resolution TEM image in Figure 5c show the edge of part of the BN nanosheet, indicating a thickness of 2 nm (~6 layers). The highly crystalline nature of the BN nanosheet is confirmed by the HRTEM image in Figure 5d, showing a pattern of lattice dots with a distance of 0.25 nm representing the distance between two adjacent BN hexagonal rings. So the distance between B and N atoms is calculated to be 0.144 nm, typical for hBN crystals. We also found few-layer BN, as shown in Figure 5e and f. The EELS spectrum in Fig. 5g shows the domination of B and N, along with a small amount of carbon. The carbon could come from the residue of benzyl benzoate which is not fully evaporated during TEM sample preparation.

View Article: PubMed Central - PubMed

ABSTRACT

Although tailored wet ball milling can be an efficient method to produce a large quantity of two-dimensional nanomaterials, such as boron nitride (BN) nanosheets, milling parameters including milling speed, ball-to-powder ratio, milling ball size and milling agent, are important for optimization of exfoliation efficiency and production yield. In this report, we systematically investigate the effects of different milling parameters on the production of BN nanosheets with benzyl benzoate being used as the milling agent. It is found that small balls of 0.1–0.2 mm in diameter are much more effective in exfoliating BN particles to BN nanosheets. Under the optimum condition, the production yield can be as high as 13.8% and the BN nanosheets are 0.5–1.5 μm in diameter and a few nanometers thick and of relative high crystallinity and chemical purity. The lubrication properties of the BN nanosheets in base oil have also been studied. The tribological tests show that the BN nanosheets can greatly reduce the friction coefficient and wear scar diameter of the base oil.

No MeSH data available.