科创中国

Carbon nanotubes on highly orientated pyrolytic graphite (HOPG) were studied with a scanning tunneling microscope (STM) operated at room temperature in ambient conditions. The atomic structure, I-V properties and the surface profiles of aggregation are carried out. The surface profiles correspond with the images through transmission electron microscopy (TEM). Aggregating nanotubes are immersed in ethanol and ultrasonically agitated to separate the individual tubes because of the weaker hydrophobic proximity effect between the nanotubes.

Liu Hongwen;Xue Zengquan;Liu Weimin;Shi Zujin;Wu Jinlei

Pan Tao Ti Hsueh Pao Chinese Journal of Semiconductors

2000

The tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were investigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under water lubrication. The wear rate of the coating linearly increases with the load. At high sliding speed, the wear rate of the coating is dramatically increased and a large amount of the counterpart material is transferred to the coating worn surface. The low friction of the coating under water lubrication is due to the oxidizing of the worn surface in the wear. The wear mechanism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microploughing at high load with low sliding speed, and oxidation wear at high sliding speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load.

La Peiqing;Xue Qunji;Liu Weimin

Tribology International

2000

The friction behavior of SiO 2 /GCr 15 in dry air and lubricated with distilled water, 1-butanol, 1-decanol and octanoic acid was investigated by using SRV ball-on-disk test rig and a Kyowa DF·PM one-way reciprocating friction tester. The reactivity between the lubricants and SiO 2 surface was simulated by differential scanning calorimetry. As the results, the order of the friction coefficient under oscillating condition can be ranked as dry air>distilled water>1-butanol>1-decanol≈octanoic acid, and that under one-way reciprocating condition can be ranked as distilled water>1-butanol>1-decanol>dry air≈octanoic acid. The order of the reactivity between the lubricants and SiO 2 surface is distilled water>1-butanol>1-decanol>octanoic acid. Thus the higher the reactivity between the lubricants and SiO 2 surface is, the higher the friction coefficient will be. The characteristics of the tribochemical reaction film play an important role in governing the friction behavior of SiO 2 ceramic.

Zhang Wenguang;Yang Shengrong;Liu Weimin;Xue Qunji;Liu Chengye

Mocaxue Xuebao Tribology

2000

High quality polycrystalline polyaniline/7,7,8,8-tetracyanoquino-dimethane (PANI-TCNQ) complex thin films have been grown by vacuum evaporation. A scanning tunneling microscope, transmission electron microscopy and high resolution scanning electron microscopy characterized the films. The films showed totally different optical and electrical properties from both of PANI and TCNQ films. Unusual two-dimensional aggregates were observed in the films. A charge transfer phenomenon, from the PANI chains to the TCNQ molecules, was observed from the Fourier transfer infrared spectrum. Compared with that of PANI and TCNQ thin films, the structural and electrical properties of the PANI-TCNQ thin films are discussed.

Li J. C.;Xue Z. Q.;Zeng Y.;Liu W. M.;Wu Q. D.;Song Y. L.;Jiang L.

Thin Solid Films

2000

A coating on carbon steel was fabricated by a self-propagating high temperature synthesis (SHS) casting route. The process is described in detail. The phases in the coating were examined using X-ray diffraction (XRD). The microstructures of the coating and the substrate were analysed using electron probe microanalysis (EPMA) and optical microscopy, respectively. The wear behaviour and microhardness of the coating were determined. The experimental results show that the coating was composed of Ni3Al and Cr7C3phases and had a dense microstructure. Metallurgical bonding had formed between the coating and the substrate. The grain size of the substrate near the interface was coarsened. The wear resistance of the coating is better than that of a bearing steel or a Ni3Al coating. The microhardness of the coating is higher than that of a Ni3Al coating or the substrate. © 2000 IoM Communications Ltd.

La P. Q.;Bai M. W.;Xue Q. J.;Liu W. M.;Yu L. G.

Materials Science and Technology

2000

LaF3 nanocluster modified with succinimide was prepared. The effect of the modified LaF3 nanocluster on the lubricating performance of liquid paraffin for steel-on-steel sliding system was investigated on a four-ball machine. The morphology of LaF3 and its lubricating mechanisms as additive in liquid paraffin were studied by means of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that LaF3 nanocluster modified with succinimide as an additive in liquid paraffin increased the load-carrying capacity and had good antiwear and friction-reduction behaviour. The XPS analysis of the worn steel surfaces indicated that a boundary lubricating film consisting of physically adsorbing film (succinimide) and tribochemically reacting film (lanthanum oxide and ferrous fluoride) was generated during the friction process. This contributed to improving the lubricating performance of liquid paraffin.

Zhang Zefu;Yu Laigui;Liu Weimin;Xue Qunji

Tribology International

2001

Nanometer Si3N4 filled poly(ether ether ketone) (PEEK) composite blocks with different filler proportions were prepared by compression molding. Their friction and wear properties under distilled water lubrication, as well as under ambient dry conditions, were investigated on a block on ring machine by running a plain carbon steel (AISI 1045 steel) ring against the PEEK composite block. The worn surfaces of nanometer Si3N4 filled PEEK and the transfer film were observed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results showed that distilled water could reduce the friction coefficient of nanometer Si3N4 filled PEEK but with the sacrifice of a large reduction in wear resistance. The SEM and EPMA pictures of the worn surfaces indicated that the wear mechanisms of nanometer Si3N4 filled PEEK under distilled water lubrication and ambient dry rubbing conditions were different. Under water lubrication, the dominant wear mechanism of the filled PEEK was severe abrasive wear with surface fracture.

Wang Qi-Hua;Xue Qun-Ji;Liu Wei-Min;Chen Jian-Min

Journal of Applied Polymer Science

2001

Tribological properties of Ni3Al-Cr7C3 coatings without and with 0.2 wt.% boron doping at room temperature under dry sliding were measured by using a ball-on-disc reciprocating tribotester for investigating effect of boron doping on the tribological properties. Microhardness of the coatings was measured. The worn surfaces of the coatings were examined by scanning electron microscopy (SEM). The results showed that hardness of the coatings was decreased with boron doping. Wear of the coatings decreased a lot at intermediate sliding speed with boron doping. But the wear increased a little at low sliding speed and did not change at high sliding speed with boron doping. Sensitivity of coatings wear to load and sliding speed at intermediate sliding speed had a significant decrease with boron doping. Friction of the coatings at low sliding speed was increased but that at high sliding speed was not changed with boron doping. Wear mechanism of the coatings was changed from brittle fracture to surface cracking with boron doping. © 2001 Elsevier Science B.V. All rights reserved.

La Peiqing;Xue Qunji;Liu Weimin

Wear

2001

With the aid of baffle movement, a technique named masking pretreatment and the method of vacuum deposition have been used to fabricate the Ag-O-Cs photoemissive thin films with internal field-assisted structure for the first time. The internal field-assisted photoemission characteristics of Ag-O-Cs thin films show that the photoelectric sensitivity is increased when the internal electric field is applied to the thin films, which indicates that the electric field has been effectively provided to the thin films by the above-mentioned internal field-assisted structure. Such an enhanced photoemission is attributed to the variations in energy-band structure of Ag-O-Cs thin films, and which are considered to induce the lower-energy electrons to participate in the photoemission.

Zhang Q.;Liu W.;Xue Z.;Wu J.

Beijing Daxue Xuebao Ziran Kexue Ban Acta Scientiarum Naturalium Universitatis Pekinensis

2001

A LaF3 nanoparticle surface coated by organic compounds containing S and P was synthesized by the chemical surface modification method. The particle size and structure were characterized using a transmission electron microscope (TEM) and electron diffraction (ED), their tribological behaviors were evaluated on a four-ball machine. The results showed that LaF3 nanoparticles as an oil additive can strikingly improve the load-carrying capacity and antiwear property of the base oil and had better friction-reduction when compared to that of ZDDP. The rubbed surfaces were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscope (XPS). It can be found that the boundary film on the worn surface was composed of LaF3 nanoparticles depositing film and tribochemical reaction film of the elements of S and P, which contributed to excellent tribological properties of LaF3 nanoparticle modified by compound containing S and P as an additive in liquid paraffin. © 2001 Elsevier Science B. V. All rights reserved.

Zhou Jingfang;Wu Zhishen;Zhang Zhijun;Dang Hongxin;Liu Weimin

Wear

2001