原子级制造的关键基础科学问题

人类的制造技术逐步向原子级推进,原子作为化学反应中的最小粒子,虽然它可以分成更小的原子核、电子等,但是从制造的角度看,原子级制造可以说是人类制造的最底层技术,也是继微纳制造之后新的制造范式,可将制造精度以及产品性能推向极致水平,代表着人类对物质世界认知和制造能力发展的新阶段,是引领未来产业变革发展的战略性技术,也是保障国家安全和推动国计民生重大装备跨代升级的重要前沿方向。本文基于第330期双清论坛总结了原子级制造的研究现状、发展趋势及机遇挑战,凝练出未来5~10年原子级制造的焦点问题和亟需解决的关键科学问题,探讨了相关领域的前沿发展方向和科学基金资助战略。

Discussion on the application prospect of the transient electromagnetic method based on the dual launcher and mine advanced detection

The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is rarely reported in the detection of pipelines in urban geophysical exploration and the application of coal mines. Based on this, this paper realizes the equivalent anti-magnetic flux transient electromagnetic method based on the dual launcher. The suppression effect of this method on the blind area is analyzed by physical simulation. And the detection experiment of underground pipelines is carried out outdoors. The results show that the dual launcher can significantly reduce the turn-off time, thereby effectively reducing the impact of the blind area on the detection results, and the pipeline detection results verify the device’s effectiveness. Finally, based on the ground experimental results, the application prospect of mine advanced detection is discussed. Compared with other detection fields, the formation of blind areas is mainly caused by the equipment. If the dual launcher can be used to reduce the blind area, the accuracy of advanced detection can be improved more effectively. The above research results are of great significance for improving the detection accuracy of the underground transient electromagnetic method.

Adsorption limitation investigation on olefins for Cu–BTC

To utilize Cu-benzene-1,3,5-tricarboxylate(Cu-BTC)adsorbed lubricant oils in the self-lubricating field,the adsorption properties of Cu-BTC on different 1-olefins must be clarified.In this work,1-hexene,1-octene,1-nonene,1-decene,1-undecene,and 1-dodecene were studied by the Monte Carlo method and experimentally.The adsorption limit of Cu-BTC for n-olefins was determined as 1-undecene by the adsorption isotherms.This suggested a limit for even straight-chain molecules to the adsorption of Cu-BTC.The maximum ratio of the olefin length of the largest pore diameter(L/D)of Cu-BTC was approximately 1.57.Furthermore,theoretical calculations(radial distribution function(RDF))and experiments(infrared(IR)spectra)confirmed the interaction of n-olefin adsorbates and the Cu-BTC framework occurred between the-CH=of olefins and the Cu and O atoms of the Cu-BTC framework.This work adds to the understanding and investigation of the adsorption of liquid lubricants using Cu-BTC as a metal-organic framework(MOF).

基于摩擦伏特效应的超滑表征技术

Friction occurs in our daily lives, and statistics have shown that it consumes approximately 1/3 of the primary energy. In addition,mechanical interface friction significantly impacts the efficiency,noise, accuracy, corrosion, reliability, and operational lifespans of equipment. Several studies have revealed various methods for reducing the coefficient of friction (COF) to the superlubricity state(COF <0.01) through efficient lubrication technology.

Superlubricity induced by partially oxidized black phosphorus on engineering steel

Macroscale superlubricity has attracted increasing attention owing to its high significance in engineering and economics.We report the superlubricity of engineering materials by the addition of partially oxidized black phosphorus(oBP)in an oleic acid(OA)oil environment.The phosphorus oxides produced by active oxidation exhibit lower friction and quick deposition performance compared to BP particles.The H-bond(–COOH…O–P,or–COOH…O=P)formed between P–O bond(or P=O)and OA molecule could benefit the lubricating state and decrease the possibility of direct contact between rough peaks.The analysis of the worn surface indicates that a three-layer tribofilm consisting of amorphous carbon,BP crystal,and phosphorus oxide forms during the friction,which replaces the shear interface from the steel/steel to carbon–oBP/carbon–oBP layer and enables macroscale superlubricity.

Black phosphorus as a new lubricant

In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.

A review on tribology of polymer composite coatings

Self-lubricating polymer composite coatings,with tailorable tribological and mechanical properties,have been widely employed on mechanical parts to reduce friction and wear,which saves energy and improves the overall performance for applications such as aerospace satellite parts,shafts,gears,and bushings.The addition of functional fillers can overcome the limitations of single-polymer coatings and extend the service life of the coatings by providing a combination of low friction,high wear resistance,high load bearing,high temperature resistance,and high adhesion.This paper compares the heat resistance,and the tribological and mechanical properties of common polymer matrices,as well as the categories of functional fillers that improve the coating performance.Applicable scopes,process parameters,advantages,and limitations of the preparation methods of polymer coatings are discussed in detail.The tribological properties of the composite coatings with different matrices and fillers are compared,and the lubrication mechanisms are analyzed.Fillers reduce friction by promoting the formation of transfer films or liquid shear films.Improvement of the mechanical properties of the composite coatings with fillers of different morphologies is described in terms of strengthening and toughening mechanisms,including a stress transfer mechanism,shear yielding,crack bridging,and interfacial debonding.The test and enhancement methods for the adhesion properties between the coating and substrate are discussed.The coating adhesion can be enhanced through mechanical treatment,chemical treatment,and energy treatment of the substrate.Finally,we propose the design strategies for high-performance polymer composite coating systems adapted to specific operating conditions,and the limitations of current polymer composite coating research are identified.

Electrical bearing failures in electric vehicles

In modern electric equipment,especially electric vehicles,inverter control systems can lead to complex shaft voltages and bearing currents.Within an electric motor,many parts have electrical failure problems,and among which bearings are the most sensitive and vulnerable components.In recent years,electrical failures in bearing have been frequently reported in electric vehicles,and the electrical failure of bearings has become a key issue that restricts the lifetime of all‐electric motor‐based power systems in a broader sense.The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles.The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents,as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures,have been discussed.The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed,and corresponding countermeasures have been proposed.Finally,a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed.

Mechanical and tribological properties of nanocomposites incorporated with two-dimensional materials

In recent years, attempts to improve the mechanical properties of composites have increased remarkably owing to the inadequate utilization of matrices in demanding technological systems where efficiency, durability, and environmental compatibility are the key requirements. The search for novel materials that can potentially have enhanced mechanical properties continues. Recent studies have demonstrated that two-dimensional (2D) nanomaterials can act as excellent reinforcements because they possess high modulus of elasticity, high strength, and ultralow friction. By incorporating 2D nanomaterials in a composite, 2D nanomaterial-based composites (2DNBCs) have been developed. In view of this, a critical review of recent mechanical and tribological studies based on 2DNBCs has been undertaken. Matrices such as polymers, ceramics, and metals, as well as most of the representative 2D nanomaterial reinforcements such as graphene, boron nitride (BN), molybdenum disulfide (MoS2), and transition metal carbides and nitrides (MXenes) have been included in this review. Their preparation strategies, intrinsic mechanical properties, friction and lubrication performances, strengthening mechanisms, influencing factors, and potential applications have been comprehensively discussed. A brief summary and prospects are given in the final part, which would be useful in designing and fabricating advanced 2D nanocomposites in the future.

Ultralow friction polymer composites incorporated with mono-dispersed oil microcapsules

Ultralow friction polymer composites were prepared by adding oil-loaded microcapsules into epoxy(EP)resin.Mono-dispersed polystyrene(PS)/poly alpha olefin(PAO)microcapsules with a diameter of~2μm and a shell thickness of~30 nm were prepared by solvent evaporation method in an oil-in-water emulsion.The lubrication behaviors of the EP resin composites with oil-loaded microcapsules have been investigated under different loads and sliding speeds.As compared with the pure EP resin,the friction coefficient of the composite could be reduced to 4%(from 0.71 to 0.028)and the wear rate could be decreased up to two orders of magnitude.It was demonstrated that the released PAO oil from the microcapsules during the friction process produced a boundary lubricating film,which could prevent the direct contact of two rubbing surfaces,and thus leading to an extremely low friction coefficient and wear rate.Moreover,the composites with microcapsules could achieve comparable lubrication properties to the case under the external lubrication condition,while the former case could effectively minimize the lubricant leakage and improve the lubrication efficiency.

Mechanical model of nanoparticles for material removal in chemical mechanical polishing process

Chemical mechanical polishing (CMP) is the most effective method for surface planarization in the semiconductor industry. Nanoparticles are significant for material removal and ultra-smooth surface formation. This research investigates the mechanical effects of the material removal in the CMP process. The various contact states of pad, individual particle, and wafer caused by the variations of working conditions and material properties are analyzed. Three different mechanical models for the material removal in the CMP process, i.e., abrasive wear, adhesive wear, and erosive wear are investigated, with a focus on the comparison of the results for different models. The conclusions and methods obtained could potentially contribute to the understanding and evaluation of the CMP process in further work.

Effects of nano thickener deposited film on the behaviour of starvation and replenishment of lubricating greases

The mechanism of grease replenishment in and around a starved point contact was studied in this work.Greases made of different thickeners and same base oil were tested and compared.Disappearing and re-formation of a dynamic grease reservoir during operation revealed that grease bled oil to replenish contact.However,the replenishment process was slow because of the presence of grease fingers along the track and thickener-deposited film inside the track.The contact angles of base oil on the chromium-coated surface and thickener-deposited surfaces were measured.Results proved that the contact angle on the deposited film remarkably increased compared with that on the chromium-coated surface from 25° to more than 40°.However,the deposited film could be consumed with continuous rolling,and replenishment was then enhanced.

Guest editorial:Special Issue on Biomedical Tribology

Biomedical tribology has developed rapidly with the joint efforts of medical and tribological researchers,and it concerns various kinds of friction that existed inside and out side the body,such as the friction of joints,the friction between skin and clothing,and the friction in the lumen(blood vessels,trachea,digestive tube,and excretory tube),which causes maiiy physiological changes and diseases in the human body.Besides,many medical devices have been used to treat or alleviate various diseases.Biomedical tribology plays a vital role in solving the widespread tribological issues in the medical devices field,aiming to improve the performance of medical devices and prolong the service life.