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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.


SEM images of the sample ball milled with different ball sizes (a) 0.1–0.2 mm (b) 0.6–0.8 mm, (c) higher magnification of selected area (indicated as box) from image “a”, and (d) normalized XRD spectra of the initial hBN particles and the sheets ball milled with different ball sizes without centrifugation.
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f4: SEM images of the sample ball milled with different ball sizes (a) 0.1–0.2 mm (b) 0.6–0.8 mm, (c) higher magnification of selected area (indicated as box) from image “a”, and (d) normalized XRD spectra of the initial hBN particles and the sheets ball milled with different ball sizes without centrifugation.

Mentions: The effect of ball size (1.0, 0.6–0.8 and 0.1–0.2 mm) on the extent of exfoliation was also studied by keeping other milling parameters the same (milling time of 10 h, ball-to-powder ratio of 10:1 and speed of 800 rpm). SEM analyses reveal that the 0.6–0.8 mm balls produce similar amounts of BN nanosheets (Figure 4b). However, when the 0.1–0.2 mm balls are used, the yield of BN nanosheets dramatically increases and their thickness is smaller and more homogeneous (Figure 4a and c). The size of the BN nanosheets produced by the 0.1–0.2 mm balls is estimated from the SEM images and about 1/3 of the nanosheets has a diameter less than 1 μm and about 2/3 is between 1.0 and 1.5 μm (see Supplementary Information, Figure S2). This result is not surprising by considering the more surface area and lighter in weight of the 0.1–0.2 mm balls compared to those of the 0.6–0.8 and 1.0 mm balls. The larger surface area can create more chance of ball-to-ball or ball-to-vial interaction/impact and therefore more shearing on the BN crystals. Their lighter weight makes the shear force gentler so that damage on BN nanosheets can be minimized. The XRD patterns from the samples produced by balls of different sizes are compared in Figure 4d. The Raman spectrum of the BN produced using the 0.1–0.2 mm balls is shown in the Supplementary Information (Figure S1).


High-Efficient Production of Boron Nitride Nanosheets via an Optimized Ball Milling Process for Lubrication in Oil
SEM images of the sample ball milled with different ball sizes (a) 0.1–0.2 mm (b) 0.6–0.8 mm, (c) higher magnification of selected area (indicated as box) from image “a”, and (d) normalized XRD spectra of the initial hBN particles and the sheets ball milled with different ball sizes without centrifugation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: SEM images of the sample ball milled with different ball sizes (a) 0.1–0.2 mm (b) 0.6–0.8 mm, (c) higher magnification of selected area (indicated as box) from image “a”, and (d) normalized XRD spectra of the initial hBN particles and the sheets ball milled with different ball sizes without centrifugation.
Mentions: The effect of ball size (1.0, 0.6–0.8 and 0.1–0.2 mm) on the extent of exfoliation was also studied by keeping other milling parameters the same (milling time of 10 h, ball-to-powder ratio of 10:1 and speed of 800 rpm). SEM analyses reveal that the 0.6–0.8 mm balls produce similar amounts of BN nanosheets (Figure 4b). However, when the 0.1–0.2 mm balls are used, the yield of BN nanosheets dramatically increases and their thickness is smaller and more homogeneous (Figure 4a and c). The size of the BN nanosheets produced by the 0.1–0.2 mm balls is estimated from the SEM images and about 1/3 of the nanosheets has a diameter less than 1 μm and about 2/3 is between 1.0 and 1.5 μm (see Supplementary Information, Figure S2). This result is not surprising by considering the more surface area and lighter in weight of the 0.1–0.2 mm balls compared to those of the 0.6–0.8 and 1.0 mm balls. The larger surface area can create more chance of ball-to-ball or ball-to-vial interaction/impact and therefore more shearing on the BN crystals. Their lighter weight makes the shear force gentler so that damage on BN nanosheets can be minimized. The XRD patterns from the samples produced by balls of different sizes are compared in Figure 4d. The Raman spectrum of the BN produced using the 0.1–0.2 mm balls is shown in the Supplementary Information (Figure S1).

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.