【作者】 刘天伟；

【导师】 董闯； 邓新绿； 武胜；

【作者基本信息】 大连理工大学 ， 材料物理与化学， 2006， 博士

【摘要】 金属铀具有独特核性能而广泛应用于国防和核能工程等领域。但铀材料化学性质十分活泼,在自然环境中容易腐蚀且腐蚀速度极快。由于腐蚀总是从表面开始的,因此以表面技术来延缓乃至克服铀的腐蚀一直受到关注。 铀的腐蚀最终会使得部件失效,因此在铀表面获得耐磨抗蚀薄膜成为了本论文研究的核心问题。在这众多的表面技术中,磁控溅射和电弧离子镀技术是目前应用最广泛的两种薄膜沉积方法。而微波-ECR等离子体增强沉积是磁控溅射和微波源的结合产物,它具有:沉膜速度快;所得薄膜致密;低温成膜,对基体影响很小等优点。电弧离子镀具有离化率高;膜基结合力强等特点。因此本论文选用了微波-ECR等离子体增强沉积和电弧离子镀技术作为研究手段,其主要结论如下: 本论文利用微波-ECR等离子体增强沉积装置先在模拟材料45^#钢上沉积Zr-N、Ti-N薄膜,主要研究N₂分压和偏压的影响。结果表明:Zr-N薄膜结构受N₂分压和偏压的影响较大,而Ti-N薄膜则不明显。随N₂分压增加,Zr-N薄膜硬度在19.8～26.3GPa之间变化,先增加后降低,Ti-N薄膜硬度一直增加,在23.0～28.2GPa之间变化。随偏压的增加,Zr-N、Ti-N薄膜硬度均呈先增加后降低趋势,Zr-N薄膜硬度在20.0～26.0GPa之间变化,Ti-N薄膜硬度在22.5～28.4 GPa之间变化。在0.5 mol/LNaCl溶液中的阳极极化实验表明:与基体材料相比,Zr-N薄膜E_corr最多升高大约118mV,基体I_corr为9.036μA,镀制薄膜后最小降至0.142μA。Ti-N薄膜E_corr最多升高大约111mV,I_corr降低约2个数量级。在实验工艺参数范围内,接近1:1化学配比的2^#ZrN和2-1^#TiN在-80V偏压下显示出最好的耐磨抗蚀综合性能。选择这两种工艺在45^#钢半球壳表面制备了ZrN和TiN薄膜,大气中存放至今已有2年,样品没有明显变化,获得了较好的抗腐蚀保护。 铀基表面Ti/TiN多层薄膜制备在电弧离子镀设备上完成。薄膜表面平整、致密,仍然存在大颗粒和圆坑,随偏压的增加大颗粒逐渐减少。所得的多层膜呈层状、柱状结构生长,随偏压的增加,柱状晶结构细化,薄膜致密。随偏压的升高,摩擦系数有所降低,耐磨性能增强。由于所制备的多层膜为软/硬交替沉积Ti/TiN,且每层较厚,使得其硬度,耐磨性能稍低于单层膜,但刻划实验表明:多层膜具有更好的结合力,结合力最好的-800V脉冲偏压下的Ti/TiN多层膜结合力为72N。 Ti/TiN多层薄膜抗腐蚀性能良好,Cl^-腐蚀和极化实验表明:性能最好的-800V脉冲偏压下样品在50μg/gCl^-溶液中,E_corr升高了约714mV,I_corr降低了约2个数量级。更多还原

【Abstract】 Uranium is widely used in the national defense and nuclear energy engineering fields for its unique properties. However, Uranium has rather active chemical properties, which includes corroding quickly in a natural environment. As a result much attention has been paid to the surface technology of uranium. Minimizing the corrosion of Uranium by using some proper techniques have been studied by scientists all over the world.The corrosion of uranium eventually causes inactivation of components, so it is most important to construct anti-wear and anti-corrosion films on the uranium surface. In the many surface modification techniques, magnetron sputtering and arc ion plating are the most widespread. The former has the following advantages: fast deposition rate, compact films, and low deposition temperature. The latter method has the advantage of: high ionized rate, and good cohesion between the film and substrate. Thus for our experiments we have chosen the two techniques to deposit films.We have utilized an MW-ECR plasma enhanced deposition method to deposit ZrN and TiN films on a simulation material #45 steel. The study mainly involved the change of the bias voltage and the N₂ partial pressure. The results show that the Zr-N structure is influenced by the bias voltage and the partial pressure of N₂, however the influence is not obvious on the Ti-N structure. As the partial pressure of N₂ changes, the hardness values of ZrN films on #45 samples vary between 19.8²6.3GPa, first increasing then decreasing. The hardness values of the TiN films are between 23.0²8.2 GPa, and increase as the partial pressure of N₂ increases. With a bias voltage increase, the hardness of ZrN and TiN films shows the trend of first increasing then decreasing, and the hardness values of the ZrN films are between 20.0 26.0GPa, while the TiN films are between 22.5 28.4 GPa. The anodic polarization experiments in 0.5mol/L NaCl solution indicate that, compared to the substrate, Ecorr of ZrN films can increase to approximately 118mV; the Icorr of the substrate is 9.036uA, and it can decrease to a minimum of 0.142μA after the films are deposited. While the Ecorr TiN films can increase to approximately 111mV, Icorr decreases about 2 orders of magnitude. Within the parameters chosen for the experiments, samples #2 ZrN and 2-#l TiN which have a close chemical ratio have displayed the best combination of wear- and corrosion- resisting properties. We deposited ZrN and TiN films with same the chemical ratio to sample #2 ZrN and 2-#l TiNon hemisphere shells of #45 steel, and exposed them to the atmosphere for about 2 years. At the time of the end of the experiment there was no obvious corrosion.The multi-layered Ti/TiN films, compared to TiN, deposited on Uranium substrates was done by arc ion plating. The results show that the film surfaces are smooth, dense, but have big grains and circular pits. The number of big grains decreases as the bias voltage increases. The multi-layer films also grow layer by layer or by island expansion. As the bias voltage is increased, the directional crystals become fine, and the films become denser. Also, the friction coefficient decreases, while the wear-resistance is enhanced. Each layer of the multi-layer films is a little thicker than the single layer film, the hardness and wear-resistance are slightly less than a single layer film. But the dividing experiments indicate that multi-layer films have better adhesion, and the best adhesion is 72N, which is obtained at a pulse bias of-800V.The anodic polarization experiments in 50ug/g CV solution indicate that Ecorr of the sample at a pulse bias of-800V increases to about 714mV, and Icorr decreases about 2 orders of magnitude. The XPS analyses indicate that the corroded multi-layer films display better anti humidity and thermal corrosion properties in a 50"C, 75%RH humidity and thermal environment. The study on electrochemical corrosion mechanisms indicates that single layer films and gradient films become inactive by deficiency penetration through the substrate and resulting in less corrosion-resistance; while the inactivation of multi-layer films is due to layer malfunction, which makes it difficult for corrosive substances to reach the substrate. In this way the corrosion resistance is enhanced.In our research, we also outline a series of experimental procedures. We have specially designed the clamping fixture and rotational structure and overcome the barrier effect of a hemisphere, which improves the deposition uniformity. According to our results, we have introduced a plasma immersion ion-implantation and deposition system. We have also developed a process of baking and sputtering to clean the samples at the same time, which solves the problem of the oxidation of films/substrate interface. The increasing temperature does not cause acceptable deformation of thin-walled samples. After optimizing the parameters, we have obtained good corrosion resisting protective films. Exposing in moist heat for the duration of the experiment, about 10 months, we observe excellent corrosion resisting properties. It is a promising technique for some engineering components.更多还原