科创中国

In this paper, the tribological properties of La(OH)₃ nanocluster modified by compound containing nitrogen as additive in liquid paraffin were investigated using four-ball machine. The results show that La(OH)₃ nanocluster modified by compound containing nitrogen as additive in liquid paraffin has high load-carrying capacity, good antiwear and friction reduction properties. The lubricating mechanisms were studied by using EPM-810Q model electron probe microanalyzer (EPMA) and PHI-5702 multi-technique surface X-ray photoelectron spectrometer (XPS). The results show that the boundary film on the worn surface is made of physically adsorbing film (N-containing organic compound) and tribochemical reaction film (lanthanum oxide). The physically adsorbing film and tribochemical reaction film formed during friction contributed to good tribological properties of La(OH)₃ nanocluster modified by compound containing nitrogen as additive in liquid paraffin.

Zefu Zhang;维民 刘;群基 薛

Wear

1998-7

PbS nanoparticles of average diameter about 5 nm, which were surface-modified with dialkyldithiophosphate (DDP), were prepared by chemical synthesis. The synthesized DDP-coated PbS nanoparticles were characterized by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron diffraction (ED). The antiwear ability of the coated PbS nanoparticles as additive in liquid paraffin was investigated using a four-ball machine. The worn surfaces were analysed with XPS also. It was found that the dispersion capacity and oxidative stability of PbS nanoparticles could be improved effectively by surface modification with DDP. Meanwhile, DDP-coated PbS nanoparticles could improve the antiwear ability of liquid paraffin even at an extremely low concentration. This was attributed to the formation of a chemical reaction boundary film consisting of PbS, PbO, FeS, Fe₂O₃, SO₄^2- and PO₄^3-.

Shuang Chen;维民 刘;Laigui Yu

Wear

1998-7

A series of W and Al co-doped hydrogenated amorphous carbon flms (a-C:H(Al, W) films) were deposited on n(100) Si substrates by medium frequency magnetron sputtering W-Al composite target (area ratio 1:1) in argon and methane gas mixture atmosphere. The effect of CH₄ flow rate on the composition, structure and surface morphology of films were analyzed, and the mechanical and tribological properties of films were also characterized. The results demonstrate that with the increase of CH₄ flow rate, the contents of carbon of films increased while the contents of W and Al decreased gradually, and the metallic target could be poisoned due to the overhigh CH₄ flow rate. The contents of sp²C and sp³C could be controlled by the W, Al and H implantation. The surfaces of all films were rather smooth, with the Root Mean Square surface roughness between 0.386 nm and 0.480 nm. The nano-hardness (H) and elastic modulus (E) of films were between 9.98 GPa and 11.37 GPa, 71GPa and 93.36 GPa, respectively. And all samples exhibited elastic recovery rate higher than 70%. The film containing 3.74% of W and 2.37% of Al showed favorable antifriction and wear-resistant properties in ambient air with a H/E ratio of 0.141 and a H³/E² ratio of 0.198. The good tribological property of film can be attributed to moderate ratio of sp³C/sp²C, excellent elastic deformation property and the transfer layer on counter body.

Qiu Yu Gong;Jun Ying Hao;Xiao Qiang Liu;维民 刘

Mocaxue Xuebao/Tribology

2013-11

The tribological performance of room-temperature ionic liquid of alkylimidazolium tetrafluoroborate was evaluated using an Optimol SRV oscillating friction and wear tester in air and a CZM vacuum friction tester in vacuum (1 × 10^-3Pa) using a steel/steel (SAE52100) contact. From the results, the ionic liquid exhibits excellent friction-reduction, antiwear proprieties, both in air and vacuum, which are superior to phosphazene (X-1P) and perfluoropolyether (PFPE). During friction, the ionic liquid forms a surface protective film mainly composed of FeF₂ and B ₂O₃, which contributes to low friction and wear.

维民 刘;Chengfeng Ye;Qingye Gong;Haizhong Wang;Peng Wang

Tribology Letters

2002

Using plasma-based ion implantation, two types of gradient layers have been prepared on 2024 Al alloy. One is prepared by N-implantation then C-deposition, the other adds an interlayer composed of a Ti layer and a Ti-N layer between N-implantation and C-deposition. C-deposition is carried out at various implanting voltages or C₂H₂/H₂ ratios. The composition depth profiles of these layers were characterized by x-ray photoelectron spectroscopy. The structure, morphologies and microstructure of the C layers were studied using Raman spectroscopy, atomic force microscope and transmission electron microscope, respectively. The surface hardness was measured with a Knoop tester and a mechanical property microprobe. The dry ball-on-disc wear tests were performed in ambient air. The gradient layer without interlayer is composed of an N-implanted layer rich in AlN and a diamond-like carbon (DLC) layer (film), and the two layers are connected with a C-Al transition layer containing Al₄C₃. The Ti layer rich in α-Ti and the N-implanted layer are connected by a Ti-Al transition layer containing TiAl₃, while the Ti-N layer rich in TiN and the DLC film are connected by a C-Ti transition layer containing TiC, TiCN, etc. Thus, the gradient layer with interlayers has optimized the gradient structure. DLC films are compact and amorphous, contain high sp³/sp² ratios and depend on the implanting voltage and the C₂H ₂/H₂ ratio. Similarly, these gradient layers exhibit significant improvement in morphologies, surface hardness and tribological properties; the interlayer, the implanting voltage and the C₂H ₂/H₂ ratio all have prominent effects on these properties.

J. X. Liao;L. F. Xia;M. R. Sun;维民 刘;T. Xu;群基 薛

Journal Physics D: Applied Physics

2004-2-7

Compared with dry sliding, all water solutions of polyols reduce the friction coefficient, but increase its wear volume. The pure polyols not only reduce the friction coefficient significantly, but also reduce the wear volume of (Ca, Mg)-sialon apparently (1-2 order) and the lowest friction coefficient of 0.06 can be approached, when it is lubricated by ethanediol. The order of wear volume of (Ca, Mg)-sialon in four different polyols is as follows: ethanediol, 1.4-butanediol, 1.3-butanediol, propanetiol. The longer the carbon chains and/or the more the number of hydroxy, the smaller the wear volume of (Ca, Mg)-sialon. The FT-IR analysis shows that the tribochemical reactions between (Ca, Mg)-sialon and polyols lead to the formation of anti-wear and friction-reducing tribo-film, which in turn reduce the wear volume and friction coefficient of (Ca, Mg)-sialon.

Wengguang Zhang;Huiwen Liu;维民 刘;群基 薛;Cheng Zhang;Peiling Wang;Weiying Sun

Cailiao Yanjiu Xuebao/Chinese Journal of Materials Research

1999-6

The science and technique of nanoscale materials have been focased on the important potential applications, such as electricity, optics, chemistry industry, ceramic, medicine and so on. The porous anodic aluminum oxide film has received significant attention due to its application in the preparation of one-dementional nanostructured materials. This process involves synthesizing desired materials within the pores of the porous anodic aluminum oxide film. The structural features and pore formation theories of porous aluminum oxide templates have been reviewed. The recent progress in the fabrication of the nano-scale materials, such as conductive polymers, metals, semiconductors, composites and carbon tube, using the anodic aluminum oxide film as the template, is also concerned. The importance of porous alumina template for the synthesis of novel nanomaterials has been exhibited.

Yanchun Zhao;Miao Chen;Tao Xu;维民 刘;Xiang Liu

Chinese Journal of Chemical Physics

2004-8

A self-assembled MoS₂/Mo-S-C multilayer film prepared by r.f. co-sputtering of MoS₂ and graphite targets was tribotested in diverse sliding atmospheres, and the lubricant mechanism and its correlations to the selective releasing behavior of non-lubricant component were analyzed in detail. Based on the analysis of composition and structural transformation of transferred materials by Raman and HRTEM characterizations, selective releasing behavior according to the sliding atmospheres were found to be particularly apparent in vacuum and dry inert atmospheres. Under these conditions, a-C in graphitic form was selectively released outwards from the topmost surfaces of contacts, leaving MoS₂ layers finely reordered in (002) orientation playing a lubricant role. Composition and structural transformation were observed not only on the topmost surface of wear track but also on the underlying layer at a thickness of tens of nanometers. Moreover, it was found that the selective releasing of a-C initiated from the center of contacts with higher pressure, and then developed toward the edges, resulting in a gradual change in the composition and microstructure of the transferred materials from the well-aligned MoS₂ layers in the center to the graphitic a-C dominant composites at the edges. The short running-in periods and low-friction performance in all the tribotests suggested that the initial preference of MoS₂-riched sublayers in (002) orientation may facilitate the formation of shearless tribofilms and therefore provide a feasible way of structural tailoring in the MoS₂-based lubricant films for an improved triboactive response.

J. Xu;T. F. He;L. Q. Chai;L. Qiao;X. Q. Zhang;P. Wang;维民 刘

Physical Chemistry Chemical Physics

2017

A salt-free cationic and anionic (catanionic) surfactant system was formed by mixing a double-tailed di-(2-ethylhexyl) phosphoric acid (DEHPA, commercial name P204), which is an excellent extractant of rare earth metal ions, with a single-tailed cationic trimethyltetradecylammonium hydroxide (TTAOH) in water. With the mole ratio (r) of DEHPA to TTAOH varying from 0.9 to 1, the phase transition occurred from a densely stacked vesicle phase (L_αv) to a lamellar phase (L_α1). Macroscopic properties, such as polarization and rheology, were measured and changed greatly during the course of the phase transition. When r was 0.96 or 0.98, the steady state shear curves exhibited two yield stress values, indicating the coexistence of the L _αv phase and the L_α1 phase. The L _α1 phase formed in the salt-free and zero-charged system (r = 1.0) is defective and undulating, which was confirmed by cryogenic transmission electron microscopy (cryoTEM). The deuterium nuclear magnetic resonance spectra (²H NMR) showed that a single peak (singlet) split into two symmetric peaks (doublet) gradually, indicating the phase transition from the L _αv phase to the L_α1 phase. Correspondingly, phosphorus nuclear magnetic resonance spectra (³¹P NMR) presented changes in both the chemical shift and the peak width, indicating that these two types of bilayer structures are of different anisotropy degrees and different viscosities. When the L_α1 phase is subjected to a certain shear force, it can be reversed to a L_αV phase again, which was proved by rheological, ²H NMR, and ³¹P NMR measurements. Furthermore, a theoretical consideration about the formation of the defective and undulating L_α1 phase was taken into account from a viewpoint of energy.

Zaiwu Yuan;Shuli Dong;维民 刘;京诚 郝

Langmuir

2009-8-18

To clarify the lubricating mechanism, two kinds of oil-soluble ionic liquids (ILs) with the same cation but different anions are synthesized, and then they are added into PAO10 as additives with different mass concentration. The tribological results indicate that the mixtures perform better lubricating performance than neat PAO10 for steel/steel contacts. Then quartz crystal monitor (QCM), X-ray photoelectron spectroscopy (XPS), plasma treatment, and external potential are introduced to clarify the lubricating mechanism of ILs as additives. The lubricating mechanism of the kind of ILs can be attributed to the good adsorptivity of cations and tribochemical films on the sliding surfaces.

Guowei Huang;Qiangliang Yu;Zhengfeng Ma;Meirong Cai;维民 刘

Tribology International

2017-3-1