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794 results on '"Zhou, Huidi"'

252. POSS-Grafted PAI/MoS2Coatings for Simultaneously Improved Tribological Properties and Atomic Oxygen Resistance

Author

Yu, Chuanyong, Ju, Pengfei, Wan, Hongqi, Chen, Lei, Li, Hongxuan, Zhou, Huidi, and Chen, Jianmin

Abstract

Polyamide-imide (PAI) is extensively used in onboard spacecraft mainly as a surface-protective material owing to its inherent excellent mechanical strength, chemical inertness, irradiation resistance, high-temperature stability, and high wear resistance. Nevertheless, PAI in the low earth orbit (LEO) is severely eroded by the presence of atomic oxygen (AO). To solve this problem, in this work, the octa- and mono-amino polyhedral oligomeric silsesquioxane (OMPOSS) were incorporated into the PAI matrix by covalent grafting, and the lubricating coatings were prepared using molybdenum disulfide (MoS2) as the solid lubricant. Additionally, the effects of AO exposure on pure PAI/MoS2and POSS-reinforced PAI/MoS2coatings were investigated. More importantly, the results indicated that the coatings exhibited outstanding tribological properties and anti-AO performance owning to the addition of octa-amino POSS (OPOSS) monomers into the main chain and mono-amino POSS (MPOSS) as the end-capping reagent of the polymer. The cooperation of OPOSS and MPOSS significantly improved the AO resistance resulting from the formation of a connected and networked silicon dioxide passivating layer on the surface. As a result, the PAI-based lubricating coating modified by OMPOSS possessing excellent tribological properties and anti-AO performance would be a novel space-suitable material in LEO.

Published
2024
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261. Effects of pulse bias duty cycle on fullerenelike nanostructure and mechanical properties of hydrogenated carbon films prepared by plasma enhanced chemical vapor deposition method.

Author

Ji, Li, Li, Hongxuan, Zhao, Fei, Quan, Weilong, Chen, Jianmin, and Zhou, Huidi

Subjects
CARBON nanotubes, MICROSTRUCTURE, MECHANICAL behavior of materials, PLASMA-enhanced chemical vapor deposition, INDUCTIVELY coupled plasma spectrometry, TRANSMISSION electron microscopy, RAMAN spectroscopy
Abstract

Fullerenelike hydrogenated carbon films were produced by pulse bias-assisted rf inductively coupled plasma enhanced chemical vapor deposition (ICPECVD). The effects of pulse duty cycle on the microstructure and mechanical properties of the resultant films were investigated by means of high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, nanoindentation, and stress measurement. The low pulse duty cycle was found the key in the formation of fullerenelike structure in hydrogenated carbon films, and thus increased the hardness, elasticity, and internal stress of the films. The role of pulse duty cycle in evolution of fullerenelike structure was also discussed in terms of ion bombardment, hydrogen removal, and "annealing" effects. [ABSTRACT FROM AUTHOR]

Published
2009
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262. Mechanical and tribological properties of Cr/Cr2O3 multilayer films.

Author

Wang, Feifei, He, Nairu, Li, Hongxuan, Ji, Li, Liu, Xiaohong, Ye, Yinping, Zhou, Huidi, and Chen, Jianmin

Abstract

Cr/Cr2O3 multilayer and single-layer films were deposited through multiple arc ion plating technique. The influence of modulation ratio on the mechanical and tribological properties was also investigated. Results show that the multilayer design of Cr/Cr2O3 films could improve the toughness of films, but a certain degree of hardness loss is also observed. The hardness and adherence strength are improved with the increase of Cr2O3 layer thickness. Furthermore, alternating layers of ductile soft metals and hard ceramics could suppress the propagation of microcracks and brittle fracture. However, the decrease of modulation ratio could causes a decline in the mechanical properties. The film with appropriate modulation ratio (Cr2O3:Cr ratio 10:1) exhibits better comprehensive properties than other films, this film also exhibits an excellent wear resistance with a high load of 10 N. Consequently, the wear life is improved from 6 m of the single-layer Cr2O3 film to 835 m of the multilayer film. [ABSTRACT FROM AUTHOR]

Published
2018
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271. SYNTHESIS OF POLY (BIBENZIMIDAZOLE-P-PHENYL- BENZOBISOXAZOLE)

Author

Zhou Huidi, Lu Yan-Hua, Chen Jianmin, and Cui Hai-xia

Subjects
chemistry.chemical_compound, Monomer, Diaminobenzidine tetrahydrochloride, Polymerization, Chemistry, Polymer chemistry, Proton NMR, Thermal stability, General Chemistry, Carbon-13 NMR, Fourier transform infrared spectroscopy, High molecular weight polymer
Abstract

A diacid monomer of benzobisoxazole 2, 6-di(p-phenylene-carboxylic) acid (BBODPA) was synthesized in a simple procedure, and characterized by means of FTIR, 1H NMR and 13C NMR. The resulting BBODPA was polymerized with 3, 3'-diaminobenzidine tetrahydrochloride (DAB) to prepare poly (bibenzimidazole-p-phenyl-benzobisoxazole) (PBBIBBO) in polyphosphonc acid. The inherent viscosities values of PBBIBBO indicated that it was a kind of high molecular weight polymer. The structure of PBBIBBO was confirmed by 1H NMR, 13C NMR and FTIR. Thermal properties and dissolubility of PBBIBBO were also investigated. These results showed that PBBIBBO exhibited good thermal stability.

Published
2009

273. Preparation and high-temperature tribological properties of CrAlVYN-Ag nanocomposite coatings.

Author

Fu, Yingying, Li, Hongxuan, Ji, Li, Liu, Xiaohong, He, Nairu, Zhou, Huidi, and Chen, Jianmin

Subjects
CHROMIUM alloys, HIGH temperatures, TRIBOLOGY, NANOCOMPOSITE materials, SURFACE coatings, METAL microstructure
Abstract

CrAlVYN-Ag coatings were successfully deposited by introducing the elements of V and Ag into CrAlYN hard coatings. Their microstructure and mechanical property as a function of the annealing temperature were investigated from room temperature (RT) (∼25°C) to 800°C. Besides, the worn surfaces were analyzed after combined effects of temperature and friction to figure out the wear mechanisms at different temperatures. The coatings exhibited special surface morphologies and Ag diffusion after annealing at different temperatures. In addition, the x-ray diffraction results showed that the coatings suffered obvious oxidation once the temperature exceeded 600°C; as a result of this, the coating hardness decreased sharply. The friction coefficients were relatively high during the tribological tests from RT to 400°C because the abrasive wear mechanisms played a dominant role. The lower friction coefficients obtained at 600 and 700°C were mainly due to the self-lubricating mechanisms. However, the coating exhibited higher friction coefficient at 800°C, which was mainly ascribed to the severe oxidation wear of the coating. [ABSTRACT FROM PUBLISHER]

Published
2017
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284. Mechanical and tribological properties of Cr/Cr2O3multilayer films

Author

Wang, Feifei, He, Nairu, Li, Hongxuan, Ji, Li, Liu, Xiaohong, Ye, Yinping, Zhou, Huidi, and Chen, Jianmin

Abstract

Cr/Cr2O3multilayer and single-layer films were deposited through multiple arc ion plating technique. The influence of modulation ratio on the mechanical and tribological properties was also investigated. Results show that the multilayer design of Cr/Cr2O3films could improve the toughness of films, but a certain degree of hardness loss is also observed. The hardness and adherence strength are improved with the increase of Cr2O3layer thickness. Furthermore, alternating layers of ductile soft metals and hard ceramics could suppress the propagation of microcracks and brittle fracture. However, the decrease of modulation ratio could causes a decline in the mechanical properties. The film with appropriate modulation ratio (Cr2O3:Cr ratio 10:1) exhibits better comprehensive properties than other films, this film also exhibits an excellent wear resistance with a high load of 10 N. Consequently, the wear life is improved from 6 m of the single-layer Cr2O3film to 835 m of the multilayer film.

Published
2018
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293. Insight into Al existing form and its role on microstructure and properties of Cr1-xAlxN films.

Author

Fu, Yingying, Li, Hongxuan, Ji, Li, Liu, Xiaohong, Liu, Liu, Zhou, Huidi, and Chen, Jianmin

Subjects
CRYSTAL defects, MICROSTRUCTURE, MAGNETRON sputtering, PHYSICAL vapor deposition, THIN films
Abstract

A series of Cr1-xAlxN (where x denotes the atom fraction of Al in Cr1-xAlxN film) films with different Al contents have been deposited by unbalanced reactive magnetron sputtering technique. The chemical composition, microstructure, surface morphology, cross-sectional structure, mechanical properties, thermal stability and tribological properties of the deposited films were studied by means of different techniques. It is found that with the increase of Al doping, the Al atoms either substitute the Cr atoms or occupy the interstitial sites in the CrN crystal lattice firstly, and when the Al doping content exceeds the solid solubility, superfluous Al atoms then exist in the form of amorphous or nanocrystal state in the films. Meanwhile, the grain size becomes smaller, and the microstructure gets denser because the Al doping leads to multiple crystal orientations and inhibits the grain growth. The Al doping induced solid solution hardening and grain boundary effects contribute to the high hardness of CrAlN films, and the dense structure as well as interstitial solid solution of Al, which can block the diffusion channel, endows the CrAlN films good oxidation resistance. Besides, a small amount of free Al existing in the films is favorable to improve the thermal stability without obvious loss of hardness. Finally, the relatively high hardness and good thermal stability make the Cr0.29Al0.71N film has relatively good tribological properties than CrN film under a wide temperature range, which extends the operating temperature of the CrN films in some fields. [ABSTRACT FROM AUTHOR]

Published
2016
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