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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 (a) starting hBN particles; (b, c) partially exfoliated hBN particles after 2 h milling; (d) more exfoliated particles after 5 h milling; (e) completely exfoliated particles after 10 h milling; and (f) normalized XRD spectra of the initial hBN particles and the sheets ball milled for different periods of time without centrifugation.
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f1: SEM images of (a) starting hBN particles; (b, c) partially exfoliated hBN particles after 2 h milling; (d) more exfoliated particles after 5 h milling; (e) completely exfoliated particles after 10 h milling; and (f) normalized XRD spectra of the initial hBN particles and the sheets ball milled for different periods of time without centrifugation.

Mentions: The starting hBN particles have a typical disc-like shape with diameters of 10–20 μm and thickness in the order of 100 nm, as shown by the scanning electron microscopy (SEM) image in Figure 1a. Different from traditional ball milling technique which normally causes dramatic damage to the sample212223, ball milling in a liquid agent was chosen to reduce impact. The study of milling time effect on BN peeling was based on 1 mm steel balls with a ball-to-powder weight ratio of 10:1 at a milling speed of 800 rpm in benzyl benzoate. According to SEM studies, most of the hBN particles become delaminated after 2 h milling. Figure 1b and c show partially exfoliated hBN particles caused by the impact of the milling balls which predominantly produced shear force during the milling. Under the shearing force, the weak interplanar bonds broke and thinner BN sheets could be produced. However, the yield of few-layer BN was still low at this stage (2 h). With the extension of milling time to 5 h, the exfoliation was more complete, as shown in Figure 1d that there were more BN nanosheets than hBN particles. After 10 h milling, the yield of BN nanosheets further increased, but the size of the BN nanosheets slightly reduced compared to the product from the 5 h milling. This indicates that certain milling time is required to allow the full exfoliation of BN, but extended milling should be avoided to minimize damage to the BN nanosheets. In this particular case, the best milling time is 10 h.


High-Efficient Production of Boron Nitride Nanosheets via an Optimized Ball Milling Process for Lubrication in Oil
SEM images of (a) starting hBN particles; (b, c) partially exfoliated hBN particles after 2 h milling; (d) more exfoliated particles after 5 h milling; (e) completely exfoliated particles after 10 h milling; and (f) normalized XRD spectra of the initial hBN particles and the sheets ball milled for different periods of time without centrifugation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: SEM images of (a) starting hBN particles; (b, c) partially exfoliated hBN particles after 2 h milling; (d) more exfoliated particles after 5 h milling; (e) completely exfoliated particles after 10 h milling; and (f) normalized XRD spectra of the initial hBN particles and the sheets ball milled for different periods of time without centrifugation.
Mentions: The starting hBN particles have a typical disc-like shape with diameters of 10–20 μm and thickness in the order of 100 nm, as shown by the scanning electron microscopy (SEM) image in Figure 1a. Different from traditional ball milling technique which normally causes dramatic damage to the sample212223, ball milling in a liquid agent was chosen to reduce impact. The study of milling time effect on BN peeling was based on 1 mm steel balls with a ball-to-powder weight ratio of 10:1 at a milling speed of 800 rpm in benzyl benzoate. According to SEM studies, most of the hBN particles become delaminated after 2 h milling. Figure 1b and c show partially exfoliated hBN particles caused by the impact of the milling balls which predominantly produced shear force during the milling. Under the shearing force, the weak interplanar bonds broke and thinner BN sheets could be produced. However, the yield of few-layer BN was still low at this stage (2 h). With the extension of milling time to 5 h, the exfoliation was more complete, as shown in Figure 1d that there were more BN nanosheets than hBN particles. After 10 h milling, the yield of BN nanosheets further increased, but the size of the BN nanosheets slightly reduced compared to the product from the 5 h milling. This indicates that certain milling time is required to allow the full exfoliation of BN, but extended milling should be avoided to minimize damage to the BN nanosheets. In this particular case, the best milling time is 10 h.

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.