| A new kind of silicon oxidic film was prepared on aluminum and aluminum alloy with SiHj/Oi/Ni system by ambient pressure chemical vapor deposition(APCVD), which was processed in an open bell-like reactor. The surface reaction was assumed as below:while N2 was dispensed to dilute the gases. The process was operated in 3 80 癈 -420 癈, with the flow rate ratio of 02 to SitU about 1:20~30. The substrates were made of different materials like pure Al, Al-Mg alloy, YZL etc, which were pretreated by different process before deposition, like degreasing by organic solvent, chemical process, polish and the combination.After the deposition, the chemical composition, microstructure, and the morphology of the film was studied by XPS, TEM, XRD and SEM. The XPS result showed that the film was composed of silicon and oxide, while the ratio of the two element was 1:1.6-1.80, below the normal stoichiometry. The TEM diffraction image was composed of homocentric extensive circles, which indicated amorphous structure. With high resolution observation, it was showed that the structure of the film was mostly amorphous, with partly ordered regions distributed on it. In aid of XRD result it was concluded that the microstructure of the film was amorphous/ crystallitic low-temperature silicon oxide. There were two characteristic morphology of the film in SEM observation, the accumulation of globular/ cystiform structure and the comparably plain surface, the latter of which was left behind after the shedding of partial surface. In addition to this, the original surface of the film was highly affected by the CVD temperature, the composition of the substrate, and the pretreatment process. The film represented uniformity in the TEM observation, which was characteristic in amorphous materials.Some important physical parameter of the film was measured and calculated, like the density and the porosity. The density of the film was about 2.58g/cm3, obtained as definition. After comparing with other scholar's results of the similar materials the result was fairly good considering the comparably simple method. The porosity of the film was 9.27% by buoyancy method, which was fairly large compared with other porous films. The hardness of the film was not obtained because of the thickness and the brittleness of the film.The tribological property of the film was tested on MMW-1 pin-disk tribology machine, with polyfluortetraethylene(PFTE) as pin material. The influences of the parameters in the experiment was examined, which showed that with the increase of the hardness of the pin and the thickness of the substrate the friction coefficient u of the material was increased. The pretreatment on the substrate before deposition influenced u . The composition of the substrate and the latter polish treatment of thefilm had little effect on u in the research. With the compare of the friction coefficients of the metal substrates deposited by CVD and those without deposition, the CVD process could reduce u and its application is feasible. A new kind of wear machine was designed and used to test the sliding wear property of thin films, especially those with different electronic property from the substrates. The pin in this test was quenched GCrlS. The results showed that the process could be divided to two different period, the steady wear period and the severe wear period. The behavior of the films on the Al-Mg alloy substrates was better than those on the pure Al. By chemical pretreatment on the substrates, the wear property of the films could be improved. Compared with the films prepared by several chemical oxidization methods, the silicon oxidic films represented excellent wear property. The resistance of the film was measured by multimeter in dry and humid conditions. When dry, the film was dielectric, but as the water included the dielectric property of the film was damaged, which proved that the film was porous. In order to improve the dielectric property of the film under humid conditions, CoSCu and Na2SiC>4 was used to seal up the small... |
PDF Full Text Request