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Research on the Preparation and Performance of Ti Film Sputtered on Gd

Author: LiLi
Tutor: WuWei
School: West China University
Course: Materials Processing Engineering
Keywords: Ti film magnetron supptering surface topography microstructure macro performance Gd
CLC: TB383.2
Type: Master's thesis
Year: 2009
Downloads: 75
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Abstract

Magnetic refrigerating technique is widely paid attention to energy conservation and Environmental protection. At room temperature, Gd is one of the important magnetic refrigerant material in magnetic refrigerators, for it exhibits large magnetocaloric effect, perfect toughness and easy processed. However, it is easy to be corroded in the exchange heat liquid of magnetic refrigerator during working, which impairs its service life seriously. So, it is significantly important to protect Gd. According to theoretical analyses and practical experience, we found Ti film has excellent corrosion resistance deposited on Gd. Based on the above, this paper made a deep research on the preparation and performance of Ti film sputtered on Gd.The research on the relationship between the microstructure of Ti films and its various properties were rarely reported. Therefore this thesis focuses on the regular relationship between microstructure and properties in order to reinforce the application research foundation and supply beneficial reference for preparing Ti films with better properties.The work of Ti film, prepared by means of DC magnetron sputtering technology is described in this paper. Three parameters of DC magnetron sputtering machine were adjusted respectively to check how the parameters influence the deposition and microstrutures of Ti film, which were deposition time, sputtering power as well as working pressure of argon. Atomic force microscopy(AFM) was used to study film thickness and microstructure of Ti films. Based on the above work, Ti was coated on the surface of Gd to examine how the microstructure of the Ti which controlled by each working parameter affect the four macro performance. The adhesion between the films and the substrate was checked by a tension test. The adiabatic temperature changes of samples were studied by an adiabatic temperature changes test devices. The polarization curve of the samples coated Ti films were assayed by a potentiostat to evaluate the ability of Ti films on resisting electrochemical corrosion. The corrosion rate test shows the different effectiveness of the Ti films prepared under different parameters as compared with pure Gd.The result of the experiment proves that Ti films with flat surface in the resolution of nm can be achieved with the method of DC magnetic sputtering technique.The surface is compact without pinhole, and the structure is even. The Ti films grow from the atom piles distributed to the form of island. When the film is growing, its surface is rough correspondingly, and the crystal particles show the form of thin fibre. In the three parameters, the sputtering current plays the most significant role influencing on the film microstructure. When the current is small (1A～1.5A), the film are in the state of non-crystal. In this phase, because the particles remain out of order, the macro performances of the film do not change obviously. When the current goes up to 2A, the out-of-order state of the particles are gone, and the macro performance shows great improvement. When the current reaches 3A, the crystal particles get large rapidly, and the shape becomes hexagon with flag top. This kind of micro structure endows the Ti films with more excellent macro performance. In the system of water-corrosion, it can well resist the corrosion. Compared with pure Gd, the corrosion rate falls obviously. From the analysis, the sputtering time affect the water-corrosion rate of the Ti films a little. The increase of sputtering current can slow down the corrosion speed of the samples dramatically. The intensity of working pressure of argon during sputtering Ti film does not show any relationship with the corrosion speed. However, under the pressure of 1.1Pa, after corrosion experiment carried through for about twenty days, the film begins to break off, which severely weakens the protection function of the film to the substrate. The polarization curves of the Ti films sputtering on Gd show that the film boosts the corrosion potential effectively, which make a great contribution to the Gd endurance of electrochemical erosion. From the tension of film-substrate, the change of the sputtering time does not influence the combination quality of film-Gd too much. The combination quality improves with the increase of the sputtering current. At the same time, the adiabatic temperature change of the samples during magnetization and demagnetization is close to that of Gd. So the Ti films hardly affect the magnetocaloric property of Gd.

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