科创中国

A new organic complex thin film of tetrathiofulvalene/m-nitrobenzylidene propanedinitrile (TTF/m-NBP) with electrical bistable properties has been fabricated by using a hot-wall deposition method. The films were analyzed by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscope (TEM). Data recording experiments on the film were realized by applying voltage pulses between the scanning tunneling microscope (STM) tip and the substrate. The small recording dot was 1.2 nm in diameter. The width of the pulse voltage has influence upon the diameter of the recording marks. The current-voltage (I-V) curves of the film showed a conductive behavior for the recorded region, while a high resistance behavior for the unrecorded region. The possible conductive mechanism was also discussed. (C) 2000 Elsevier Science B.V.

Li JianChang;Xue ZengQuan;Liu WeiMin;Hou ShiMin;Li XiuLan;Zhao XingYu

Physics Letters Section A General Atomic and Solid State Physics

2000

A thin film of 1,1-dicyano-2,2-(4-dimethylaminophenyl) ethylene (DDME) has been grown by a modified vacuum deposition. The films were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning tunneling microscopy (STM). Highly ordered parallel molecular stacks were repeatedly observed with STM under ambient conditions. The dc current-voltage (I-V) characteristics of device Au/DDME/Au were measured, and the film was found to possess good electrical bistability and electrochromic properties. Nanometer-scale recording was realized on the film by applying pulse voltage between the STM tip and substrate. The possible switching mechanism is discussed. © 2000 American Institute of Physics.

Li J. C.;Xue Z. Q.;Li X. L.;Liu W. M.;Hou S. M.;Song Y. L.;Jiang L.;Zhu D. B.;Bao X. X.;Liu Z. F.

Applied Physics Letters

2000

The tests were carried out by using Si3N4ball as well as M50 tool steel ball on three Si3N4discs at a load of 98N and temperature of 370°C. The results indicate that (1) the mineral oil provides effective lubrication for steel-on-Si3N4system; whereas for the combination of mineral oil with TCP or TMPTH, the wear can even be reduced; (2) in comparison with the steel-on-Si3N4system, the wear of Si3N4discs is greater for the Si3N4-on-Si3N4system; (3) the X-ray photoelectron spectroscopy (XPS) analyses on the rubbed surface reveal the existence of transfer of iron or iron compounds to the surface of silicon nitride disc and the formation of a film containing carbonaceous deposits and iron compounds such as iron phosphate.

Liu Weimin;Klaus E. E.;Duda J. L.

Mocaxue Xuebao Tribology

1995

The nanometer Si3N4 filled polyetheretherketone (PEEK) composite blocks were prepared by compression molding. The friction and wear properties of nanometer Si3N4 filled PEEK were investigated on a block-on-ring machine by running the PEEK composite block against a plain carbon steel (AISI 1045 steel) ring. The morphologies of the wear traces and the transfer film were observed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It was found that nanometer Si3N4 filled PEEK composite exhibits considerably lower frictional coefficient and wear rate than pure PEEK. Especially, the lowest wear rate is obtained with the composite containing 7.5 wt.% Si3N4. The SEM pictures of the wear traces indicate that with the frictional couple of carbon steel ring/composite block, a thin, uniform, and tenacious transfer film was formed on the ring surface, while XPS results show that Si3N4 was partly oxidized into SiO2 during the rubbing process. Thus the improvement in the tribological behavior of nanometer Si3N4 filled PEEK composite is closely related to the improved characteristics of the transfer film.

Wang Qi-Hua;Xu Jinfen;Shen Weichang;Liu Weimin

Wear

1996

A ball-on-three-disc modification of the four-ball wear tester was utilized to evaluate the wear property of Si3N4 lubricated with mineral oil, containing additives such as oleic acid, stearic acid and zinc dialkyldithiophosphate (ZDP). For comparison, the wear of a steel ball on Si3N4 discs and an Si3N4 ball on Si3N4 discs was investigated for identical test conditions, and the worn surfaces of the discs were analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The study indicates that the steel ball-on-Si3N4 disc system usually gives less wear of the Si3N4 disc compared with the Si3N4 ball-on-Si3N4 disc system. Among the three tested additives, ZDP shows best antiwear property even at a load of 396 N in the Si3N4 ball-on-Si3N4 disc system. XPS results reveal that a protective surface film containing the products of degraded ZDP was formed on the rubbed surfaces.

Liu Weimin;Duda J. L.;Klaus E. E.

Wear

1996

The tribological properties of K2Ti4O9 whisker reinforced A1-20Si aluminum matrix composites were investigated in a mode of low amplitude reciprocal sliding. The ball-on-disk tests were performed at applied loads of 20-100 N and sliding velocity of 0.09 m s^-1. The water lubricated composites demonstrated higher wear resistance and friction coefficient than the tetradecane lubricated composites did. The main wear mechanism is microgrooving at low applied loads and tribochemical wear at high applied loads for the pairs lubricated with water, microgrooving at all test loads for the pairs lubricated with tetradecane.

Bai Mingwu;Xue Qunji;Liu Weimin;Yang Shengrong

Wear

1996

A 2-ethyl hexoic acid (EHA) surface-modified TiO2 nanoparticle with an average diameter of 5 nm was chemically synthesized. The friction-reduction and antiwear behaviors of the prepared EHA-TiO2 as an oil additive in liquid paraffin were evaluated with a four-ball wear tester. The rubbed surfaces after friction tests were investigated with X-ray photoelectron spectroscopy (XPS). Friction tests indicate that EHA-TiO2 exhibits good performance in friction and wear reduction as well as in load-carrying capacity. Results of XPS analysis show that a boundary film mainly composed of TiO2 and titanates was formed on the rubbed surfaces. © 1997 Elsevier Science S.A.

Xue Qunji;Liu Weimin;Zhang Zhijun

Wear

1997

Deposition conditions may strongly affect the photoelectron emission characteristics of Ag-BaO thin films. Two sets of Ag-BaO thin films are grown by cold deposition and warm deposition respectively. When the films are illuminated by ultra-short laser pulse with a wavelength of 0.53μm, no obvious difference between the photoelectron emission of the two sets of films is observed. If 1.06μm laser pulse is used, the photoelectron emission difference is significant. The ultra-short laser pulses are produced by bi-photon photoelectron emission for the two sets of films.

Dai Zhiyong;Wu Jinlei;Liu Weimin;Xue Zengquan;Wu Quande

Zhenkong Kexue Yu Jishu Xuebao Vacuum Science and Technology

1997

The wear property of Si3N4 under vapor phase lubrication of oleic acid and tricresyl phosphate (TCP) in both steel-on-Si3N4 and Si3N4-On-Si3N4 systems were investigated. The used oleic acid and TCP were fed into the evaporator simultaneously with two syringe pumps, and the vaporized lubricants were delivered by the carrier gas of nitrogen to the ball pot of a modified four-ball wear tester. Tests were made using M50 tool steel ball or Si3N4 ball against Si3N4 discs at a load of 98 N and temperature of 370°C. Oleic acid, TCP and the combination of oleic acid with TCP as the vapor lubricants were evaluated for test time from 30 min to 3 h. Results indicate that the oleic acid provides effective lubrication for steel-on-Si3N4 system, and for the combination of oleic acid with TCP, the wear can be even reduced. The wear of Si3N4 disc in steel-on-Si3N4 system is always lower as compared to that of in Si3N4-On-Si3N4 system. X-ray photoelectron spectroscopy (XPS) analyses of the rubbed surfaces suggest the formation of a film containing carbonaceous deposits, iron phosphate, N-containing compounds and silicon oxides due to the oxidation of Si3N4. © 1998 Elsevier Science S.A.

Liu Weimin;Klaus E. E.;Duda J. L.

Wear

1998

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.

Zhang Zefu;Liu Weimin;Xue Qunji

Wear

1998