纯铝/铝合金基底上SiO_x陶瓷膜层的CVD制备及其性能研究

【作者】 刘立；

【导师】 郦剑； 沈复初；

【作者基本信息】 浙江大学 ， 材料加工工程， 2002， 硕士

【摘要】 本研究在金属铝及其合金的基底上，以硅烷和氧气为气源，氮气为载气，在自制的开管式筒型反应器里，通过常压化学气相沉积（APCVD）的方法制备了硅氧化物（SiO_x）陶瓷膜层。在金属铝上制备硅氧化物陶瓷膜层的源料区反应为： SiH₄+O₂—旦2些匹些呻SiO_x+H₂O。 APCVD制备的温度为380℃～400℃，O₂:SiH₄（流量比）约为1:20～30，基底材料包括工业纯铝、铝镁合金、YZL等。沉积前，基底经过不同的表面预处理，预处理方式为有机溶剂处理、化学处理和打磨的不同组合。 本研究通过XPS测定了膜层的化学组成，利用TEM和XRD研究了其显微结构，并通过SEM和TEM对其形貌进行了考察。XPS测定结果表明，膜层是由硅、氧两种元素构成的，两者的化学计量比为1:1.60～1.80，是缺氧的。通过TEM衍射分析发现，衍射花样为宽泛的同心圆环；对膜层高分辨观察表明，该膜层主要为非晶结构，但又存在着局部有序的区域；通过XRD测试，进一步证实了TEM的结果，并且说明膜层为低温氧化硅的非晶／微晶结构。通过SEM观察，发现膜层的特征形貌有两种：一是表面膜层片状／舌状脱落后留下的较平坦的区域；二是球状／胞状堆积。另外，膜层的原始形貌还受到温度、基底、表面预处理等制备参数的影响。在TEM下观察到膜层具有均匀形貌，未发现质量衬度和衍射衬度，表现出典型的非晶形貌。 本研究对膜层的典型物理参数进行了测量。通过简单的方法测得膜层的密度约为2.58g／cm³；采用浮力法测试计算得孔隙率为9.27％，与其它多孔涂层的孔隙率比较，该膜层的孔隙率较大，比较疏松。由于膜层厚度及本征脆性的影响，我们无法准确测量膜层的硬度。 本研究采用聚四氟乙烯作为销试样，在MMW-1型销盘式摩擦磨损实验机上进行了摩擦实验。研究表明，销试样的硬度、基底材料的厚度对摩擦系数有正作用；基底的表面预处理也会影响摩擦系数。基底成分和膜层的后续处理对摩擦系数的影响不明显。通过CVD沉积和未沉积膜层的铝材的摩擦比较实验，发现CVD沉积可以减小摩擦系数，因而具有应用的可行性。 在本研究中，我们自行设计了一台测定膜层耐磨性的磨损机，用于与基底具有不同电性的膜层的耐磨性测量，使用中的对磨材料为淬火后的GCr15。膜层的磨损一时间曲线表明，磨损在开始阶段较为平稳，后来逐渐加剧。通过对不同试样加以比较，对相同条件下沉积的膜层，镁铝合金为基底时具有更好的耐磨性；经过表面化学预处理的膜层的耐磨性好于未处理的试样；CVD制备的陶瓷膜层的耐磨性优于铝表面的化学氧化膜。 在本研究中，膜层的电阻测试是在干燥和潮湿两种条件下进行的。干燥时膜层具有非常好的介电性；有水存在时，膜层的介电性降低，这证明了膜层是疏松多孔的。为了提高膜层在潮湿条件下的介电性能，对多孔膜层进行了封闭实验。封闭实验采用了两种方案，其中用水解硫酸钴水解封闭的膜层，在潮湿条件下的电阻没有提高：采用硅酸钠生成原硅酸封孔后的膜层，电阻有所提高，并且当环境偏碱性时，封孔效果较好。此外，我们还对以后进一步的实验提出了设想。 本研究通过机械拉伸实验、划痕实验以及弯曲实验对膜层与基底的结合性能进行了测试和评价。拉伸实验中，膜层未从基底上脱开，膜基结合强度大于粘接剂环氧树脂的最大剪切强度（SMPa）。弯曲实验的结果表明，膜基间有良好的结合性能和相互配合变形的能力。热冲击实验中，膜层没有与基底脱开，再次印证了上述结论，而且表明铝基氧化硅陶瓷膜层具有良好的抗热冲击性能，膜／基之间有好的热变形匹配能力。更多还原

【Abstract】 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更多还原