Black phosphorus quantum dots: A new-type of water-based high-efficiency lubricant additive

Abstract

Black phosphorus quantum dots (BPQDs), obtained via a typical solution-based top-down method, were used as water-based lubricant additives. BPQDs exhibited remarkable friction reduction and anti-wear properties even at the ultra-low concentration of 0.005 wt%, which reduced the friction coefficient and wear volume of the base liquid by 32.3% and 56.4%, respectively. In addition, the load-supporting capacity of the base liquid increased from 120 N to over 300 N. BPQDs-based additives exhibited a relatively long lifetime at a relatively high load of 80 N. The performance of BPQDs considerably exceeded that of the BP; this may be attributed to their small and uniform particle size, good dispersion stability in water, and high reactivity at the frictional surfaces. The results of the surface wear resistance analysis demonstrated that a robust tribochemical film with a thickness of approximately 90 nm was formed on the rubbing surface lubricated with 0.005 wt% of BPQDs dispersion. Moreover, the film served as a direct evidence of the excellent tribological performance of BPQDs.

A Comprehensive Review of Water-Based Nanolubricants

“…Using this technology, the metal surface can become hardened by sintering and filling NPs into macroscopic cracks [236], as shown in Figure 15c. A mending effect has been observed in numerous studies [16,21,27,66,92,117,121]. Many results reveal that NPs act with a mending effect by filling in the surface defects, thereby improving the surface quality [247][248][249].…”

“…The literature demonstrates that very little research has been conducted on some rare NPs, such as black phosphorus and hydroxides. Tang et al [92] synthesised 3.9 nm black phosphorus quantum dots (BPQDs) by adding N-methyl-2-pyrrolidone (NMP) under ultrasonic treatment for 8 h. The as-prepared BPQDs with 0.1 wt.% concentration were dispersed into 2.0 wt.% Triethanolamine (TEA) aqueous solution by another 10 min ultrasonic treatment. The BPQDs dispersion showed good stability with no precipitates even after 2 weeks.…”

“…Furthermore, the best tribological properties were obtained using SiO 2 /graphene (0.1:0.4) combination in water compared to only 0.5 wt.% graphene in water, presenting decreases in COF and wear volume by 48.5% and 79%, respectively. Moreover, black phosphorus quantum dots served as a high-efficient nanoadditive in water-based lubricant with an ultra-low concentration of 0.005 wt.%, not only exhibiting remarkable wear reduction by 56.4%, COF reduction by 32.3%, but also indicating an increment in load-carrying capacity from 120N to 300 N [92]. In recent years, ball-on-plate tribometer has been used consistently for various nanoadditivies including GO, nanodiamond, copper, ionic liquids, and naphthalene (listed in Table 3).…”

“…Some scholars have revealed that these NPs themselves might roll or embed into surfaces [236][237][238]. Moreover, many scholars have mentioned the ball bearing effect in lubrication mechanism analysis of the water-based nanoadditives including metal and non-metal oxide [54,59,100], composite [86,119], and many more [68,78,92,124,137,159]. In the past few years, it has been noted that due to their spherical shape, metal and non-metal oxides such as SiO 2 [59,100] and TiO 2 [15,25,29] generate a ball bearing effect between sliding surfaces, converting the friction mechanism from sliding to rolling and thus causing friction reduction.…”

Applications of carbon quantum dots in lubricant additives: a review

“…The polishing effect, also termed the smoothing effect, has been proven to be a promising approach to reduce the friction and wear of the contact area since it provided excellent ability in reducing the roughness of the rubbing surfaces (Fig. 13) [113,[180][181][182][183][184][185][186]. On the microcosmic, the nanoscale CQDs-based lubricant additives can easily enter into the rubbing surface and be filled up the gaps of the rough asperities, which might be acted as reservoirs of CQDs-based lubricant additives within the contact area, and this process is referred to as the smoothing out process.…”