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Qi Z.B.,Xiamen University | Sun P.,Xiamen University | Zhu F.P.,Xiamen University | Wu Z.T.,Xiamen University | And 4 more authors.
Surface and Coatings Technology | Year: 2013

In this study, Ti0.34Al0.66N coatings were fabricated by arc ion plating (AIP) process on ceramic carbide substrates. The tribological tests were carried out by using a ball-on-disc tribometer with different temperatures from 25°C to 900°C in air. After high-temperature testing, the microstructure, chemical composition, oxidation behavior and mechanical properties were investigated using X-ray diffraction, Auger electron spectroscopy, X-ray photo-electron spectroscopy, scanning electron microscopy and nanoindentation tests. Phase separation and crystallization of oxide layer occurred at 900°C. The decrease of surface hardness and significant improvements on wear resistance were obtained at high temperatures, which were connected to the oxidation behavior of Ti0.34Al0.66N coatings. The results showed that the formation of oxide layer determined the contacting state between the slider and coatings at elevated temperatures, and was responsible for the changes in wear mechanisms. © 2012 Elsevier B.V. Source

Qi Z.B.,Xiamen University | Zhu F.P.,Xiamen University | Wu Z.T.,Xiamen University | Liu B.,Xiamen University | And 3 more authors.
Surface and Coatings Technology | Year: 2013

ZrYN coatings with various yttrium contents (0 to 15. at.% in the targets) are deposited from zirconium yttrium composite targets using DC magnetron sputtering. The effect of varying amounts of yttrium addition on the microstructure and mechanical properties of ZrN coatings has been studied. The results reveal that yttrium atoms substitute zirconium atoms in Zr-N lattice forming the solid solution ZrYN coatings. The preferred orientation changes from (200) to (111) with yttrium addition, while the grain sizes are approximately the same. The indentation hardness of the ZrYN coatings first increases from 19.7. GPa to 24.1. GPa with increasing yttrium content up to 5. at.% and is followed by a decrease to 20.9. GPa with a further increase in yttrium content. Scratch test shows that yttrium addition has a beneficial effect on the adhesion of the ZrYN coatings with the critical load increasing from 2.8. N for the ZrN coating to 7.6. N for the ZrYN coating (yttrium content 10. at.%). © 2012 Elsevier B.V. Source

Wu C.H.,National R and nter for Tungsten Technology | Chen S.S.,National R and nter for Tungsten Technology | Nie H.B.,National R and nter for Tungsten Technology | Lin G.A.,National R and nter for Tungsten Technology | Wu Q.S.,National R and nter for Tungsten Technology
International Journal of Self-Propagating High-Temperature Synthesis | Year: 2012

Ultrafine cobalt oxide (Co3O4) powders were prepared by bubbling bed technique, an efficient and low energy consuming process of combustion synthesis technology. In this paper, discussed are the thermal decomposition of cobalt(II) oxalate dihydrate (CoC2O 4·2H2O), stability of a bubbling layer, air flow velocity, and heat distribution in the system under consideration. Key factors for regulating the process parameters are (a) reaction heat of cobalt oxalate decomposition, (b) air flow velocity and (c) reaction temperature. The optimum combustion temperature of 320-450 C and air velocity larger than the critical velocity by a factor of 1.5-2.0 can be achieved through variation in the ratio of material supply to air flow velocity. © 2012 Allerton Press, Inc. Source

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