Modification of POSS and their tribological properties and resistant to space atomic oxygen irradiation as lubricant additive of multialkylated cyclopentanes

Developing functional additive resistant to space atomic oxygen(AO)irradiation through simple molecular design and chemical synthesis to enhance the lubricating performance of multialkylated cyclopentanes(MACs)oil is a significant challenge.Herein,sulfur-containing polyhedral oligomere silsesquioxane(POSS)were synthesize via a click-chemistry reaction of octavinyl polyhedral oligomeric with alkyl sulfide.The reduce-friction(RF),anti-wear(AW)properties and anti-AO irradiation of POSS-S-R as MACs base oil additives in atmospheric and simulated space environments were systematically investigated for the first time.Results demonstrate that POSS-S-R not only possesses outstanding anti-AO irradiation capacity but also effectively improves the RF and AW of MACs in atmospheric or simulated space surroundings.This improvement is due to the excellent anti-AO irradiation properties of the POSS structure itself and the high load-carrying ability of silicon-containing and sulfur-containing compounds generated by tribo-chemical reactions,which effectively separates the direct contact of the friction interface.We believe that this synthesized POSS-S-R is a promising additive for space lubricants.

Progress in MXene-based materials for microwave absorption

Due to the rapid development of radar technology,the demand for absorbing stealth materials is increas-ing,and ultra-broadband absorption(effective absorption bandwidth>8 GHz)has become an inevitable requirement.As a new type of two-dimensional material,MXene material possesses the characteristics of excellent wave absorbing material due to its easy preparation,easy modulation of defects and sur-face functional groups,and high conductivity.This work summarizes the absorbing theory and research progress on MXene-based absorbing materials in recent years,including pure MXene absorbing materials and MXene-based magnetic or dielectric composite materials with multiple losses.Some shortcomings and research directions of MXene-based materials were pointed out.Currently,research on MXene-based absorbent materials is thriving and in a state of vigorous development.Excellent absorbent materials have been reported,but their shortcomings are also apparent.The factors that affect the performance of MXene-based absorbent materials are complex,and the absorption mechanism is relatively simple.Further systematic and detailed research is needed to clarify these influencing mechanisms,broaden the absorption bandwidth,and reduce the matching thickness to meet practical usage requirements in the future.

A novel polyionic liquid with lubricity and viscosity-increasing dual functionalities as the additive in aqueous lubrication system

The polyionic liquid poly-PEGMA-r-METAC(PPM)with quaternary ammonium has been synthesized and evaluated as additive in aqueous lubricating fluids.The rheological behavior of aqueous lubricating fluids with PPM has been characterized to confirm PPM’s function as a viscosity modifier.The tribological behavior of aqueous lubricating fluids with PPM has been investigated on SRV-V and MTM testing machines.It was found that PPM has excellent viscosity-increasing,lubricating,and anti-wear properties as an additive for aqueous,which can be attributed to the ability of PPM to form the protective film and boundary tribofilm generated from complex tribochemical reaction on rubbing surface.The obtained PPM with dual functions of anti-corrosion additives and viscosity index improver can play an important role in diverse lubrication regimes.

Oil-soluble ionic liquids as antiwear and extreme pressure additives in poly-α-olefin for steel/steel contacts

To enhance the lubricating and extreme pressure(EP) performance of base oils, two types of oil-soluble ionic liquids(ILs) with similar anion albeit dissimilar cations were synthesized. The physical properties of the prepared ILs were measured. The anticorrosion properties of ILs were assessed by conducting corrosion tests on steel discs and copper strips, which revealed the remarkable anticorrosion properties of the ILs in comparison with those of the commercial additive zinc dialkyldithiophosphate(ZDDP). The tribological properties of the two ILs as additives for poly-α-olefin-10(PAO10) with various mass concentrations were investigated. The tribological test results indicate that these ILs as additives are capable of reducing friction and wear of sliding contacts remarkably as well as enhance the EP performance of blank PAO10. Under similar test conditions, these IL additives exhibit higher lubricating and anti-wear(AW) performances than those of ZDDP based additive package in PAO10. Subsequently, X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS) were conducted to study the lubricating mechanism of the two ILs. The results indicate that the formation of tribochemical film plays the most crucial role in enhancing the lubricating and AW behavior of the mixture lubricants.

超分子凝胶润滑材料的研究进展

开发高性能润滑材料对于降低摩擦磨损带来的能量损失,以及避免严重的机械故障和关节损伤均具有重要意义.超分子凝胶润滑材料可以实现对液体润滑剂的高效捕获,因其良好的触变性能,解决了传统润滑材料易爬移、泄漏及润滑效率低等问题.超分子凝胶润滑材料具有性能动态可调和可逆相转变等特点,使其具有发展为智能润滑材料的天然优势.通过功能化设计可以赋予超分子凝胶润滑材料减摩、抗磨、抗腐蚀、自修复及高承载能力等特性,在机械润滑和生物润滑领域均表现出潜在的应用前景.本文综述了基于不同液体润滑剂(润滑油、水及离子液体)的超分子凝胶润滑材料的发展现状,并讨论了其在不同润滑领域的发展前景.

Physicochemical and tribological properties of gemini-type halogen-free dicationic ionic liquids

A series of new halogen-free dicationic ionic liquids(ILs)with different alkyl chain lengths were prepared,and the relationship between the alkyl chain length,physicochemical and tribological properties of ILs,and their role as neat lubricant for steel–steel friction pairs,was investigated.Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts,due to the halogen-free anions.The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties,especially at high temperatures.Based on the surface three-dimensional(3D)profiles,electrical contact resistance,scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),and the X-ray photoelectron spectrometry(XPS)analysis of the worn surfaces of steel discs,we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films.

Physicochemistry aspects on frictional interfaces

Friction exists wherever relative motion occurs and is the main source of energy consumption.Lubrication plays a significant role in improving fuel efficiency,reducing emissions,and prolonging the service life of machines.Surface interactions between two moving solid surfaces or the flow of a fluid (and/or environment) on a solid surface are the primary causes of friction.Apart from the mechanical design of moving parts,surface physicochemistry is of crucial importance to lubrication.This review deals with the frontier research on controlling friction and lubrication,highlights the importance of physicochemistry aspects,and enumerates the state-of-the-art chemistry solutions to tribological issues.It aims at inspiring talented young scientists from different fields to make significant contributions to the area.

Stable dispersibility of bentonite-type additive with gemini ionic liquid intercalation structure for oil-based drilling

In this study,the direct intercalation of gemini ionic liquids(ILs)with different alkyl chains into the bentonite(BT)interlayer as a high-performance lubricating additive for base oil 500SN was investigated.The purpose of modifying BT with an IL is to improve the dispersion stability and lubricity of BT in lubricating oil.The dispersibility and tribological properties of IL–BT as oil-based additives for 500SN depend on the increase in interlamellar space in BT and improve as the chain length is increased.More importantly,the IL–BT nanomaterial outperforms individual BT in improving wear resistance,owing to its sheet layers were deformed and sprawled in furrows along the metal surface,thereby resulting in low surface adhesion.Because of its excellent lubrication performance,IL-modified BT is a potential candidate for the main component of drilling fluid.It can be used as a lubricating additive in oil drilling and oil well construction to reduce equipment damage and ensure the normal operation of equipments.

Lignin composite ionic liquid lubricants with excellent anti-corrosion,anti-oxidation,and tribological properties

A new type of lubricating material(BTA-P_(4444)-Lig)was synthesized by combining lignin with tetrabutylphosphorus and benzotriazole.The tribological properties,corrosion resistance,and anti-oxidation properties of BTA-P_(4444)-Lig as a lubricant were investigated.The lubricating material exhibits excellent friction reduction and wear resistance,as well as good thermal stability and excellent oxidation resistance.Mechanistic analysis reveals that the active elements N and P in the lubricating material react with the metal substrate,and the reaction film effectively blocks direct contact between the friction pairs,affording excellent friction reduction and wear resistance.At the same time,the phenolic hydroxyl group in lignin reacts with oxygen free radicals to form a resonance-stable semi-quinone free radical,which interrupts the chain reaction and affords good anti-oxidant activity.