【作者】 马国佳；

【导师】 林国强；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2013， 博士

【摘要】 钛合金因具有强度高、耐蚀性好、耐热性高等特点而被广泛用于各个领域,但由于具有较高的表面自由能,显示为亲水性,不具备自清洁性能,长期在潮湿空气中会发生腐蚀现象,并且一些装备中的钛合金部件容易产生结冰等现象,这在一定程度上限制了钛合金的进一步应用。自然界中以荷叶为代表的生物表皮超疏水和自清洁现象给了我们重要启示,研究发现荷叶自清洁功能是由表面疏水的蜡状低表面能材料和微纳复合结构的乳突共同引起的,如果能够按照这种疏水原理研发出超疏水表面技术,并将其应用于钛合金等金属材料上,则可以起到自清洁、抑制表面腐蚀和氧化,增强防潮和防冰功能。目前除日常用品外,一些行业也急需长寿命超疏水表面技术,如航空领域,发动机进气道口处的防冰,用以防止发动机性能损失及可能引发的故障,另外还可用于大气数据传感器及机翼前缘等处的防冰,用以解决阻力增加等问题,而在电子元器件及医疗器械领域这种需要也很明显。目前,超疏水涂层多采用化学法制备,虽然工艺简单、易操作,但是制备的涂层结合力差、不耐冲击、环境适应性差,常面临涂层粉化、起泡、开裂以及疏水功能下降等失效行为。类金刚石膜(Diamond Like-carbon, DLC)具有优异力学性能,但是由于其表面能较高,因此疏水性能较差,如果通过元素对DLC薄膜的掺杂,将其表面能降低,在提高其疏水性能的同时,保障其具有良好的环境适应能力和使用寿命,将大大提高其可应用性,本文中将主要进行金属Ti和非金属F元素掺杂DLC薄膜研究,以揭示元素掺杂对薄膜疏水性能和力学性能的影响,同时注意到超疏水和良好综合性能表面的获得,通常是低表面能材料和粗糙表面形貌协同的结果,因此本文还研究了以超音速火焰喷涂(Supersonic Flame Spraying, HVOF) WC和纳秒激光制造的微盲孔为底层微结构,然后用低表面能掺杂DLC进行修饰的仿生疏水表面,具体研究内容及结果如下：(1)采用微波电子回旋共振(Microwave Electron Cyclotron Resonance, MW-ECR)等离子体反应磁控溅射技术制备Ti-DLC薄膜,研究了薄膜的化学结构及成分变化,重点考察了不同制备条件对薄膜力学性能和疏水性能的影响规律。制备的薄膜被证明是-种TiC纳米晶镶嵌的纳米复合结构薄膜,其纳米硬度最高达到33GPa,磨损量最小达到12μm3,临界载荷最大达50N,水接触角达到最大值106.5。,分析结果显示Ti-DLC膜的表面能随着Ti元素百分比含量的增加先减小后增加。分析表明薄膜疏水性能的改善,主要是由于化学键结构和成分发生了变化。(2)采用微波ECR等离子体化学气相沉积技术制备了F-DLC薄膜,主要研究不同能量、不同百分比的F元素掺杂对薄膜表面形貌和组织结构的影响,重点调查在此种变化下薄膜的疏水性能和力学性能变化规律。通过分析表明薄膜主要包含C-Fx(x=1,2,3)和C=C(F,H)交联结构,这种化学键结构导致其力学性能变差,如：纳米硬度一般在2-3GPa之间,临界载荷最高可达31N,而疏水性能大为提高,在优化工艺参数下,F-DLC薄膜最高水接触角可达159.2°。 F元素原子百分比含量对薄膜表面能有重要影响,含量的增加将使其逐渐降低,当含量为32.6%时,表面能降到最低(14.74mJ/m2)。(3)采用离子轰击、超音速火焰喷涂及纳秒激光加工三种手段对样品进行了表面微纳结构的制造,研究了不同形貌对样品疏水性能的影响,同时将微纳米结构制造与低表面能薄膜沉积工艺复合,制备了具有微纳二级结构的超疏水表面。测试结果表明：离子束轰击作用下,钛合金基体的接触角随轰击能量的增加,总体呈现逐渐升高趋势；超音速喷涂WC涂层为底层的系列样品接触角,随样品表面形貌复杂化的提高而不断升高,对WC涂层样品进行F-DLC修饰后,水接触角达到最高166°；周期性微盲孔为底层微结构的系列样品接触角变化趋势与WC涂层类似,F-DLC膜修饰后,水接触角达到165.60。(4)基于分形几何理论,采用投影覆盖法,利用Matlab软件,对以WC涂层为底层微结构的样品进行实际表面积和分形维数模拟计算,并对样品的实测接触角和模拟接触角进行对比分析。基于Wenzel和Cassie理论,建立了周期性微盲孔的数学物理模型,用于实际表面积和接触角计算,重点分析了微盲孔结构对钛合金表面疏水性能的影响。模拟结果表明采用上述两种微结构可以提高样品表面的实际表面积和分形维数,从使其疏水性能得到进一步提高。更多还原

【Abstract】 Ti alloy has been widely used in various fields, according to high strength, good corrosion resistance and high heat resistance, but it has the high surface energy, shows a hydrophilic, and does not have self-cleaning performance. Ti alloy corrosion can occur in moist air for a long time, and some Ti alloy parts in equipment are easy to produce the icing phenomenon, which limits its application in some fields. Creature skin represented by the lotus leaf in nature shows super-hydrophobic and self-cleaning properties, which offers us an important idea. It is found that a waxy material with low surface energy and the mastoid with micro-and nano-composite structure result in the hydrophobicity and self-cleaning function of the lotus leaf. If the manufacturing technology of hydrophobic surface can be developed according to the hydrophobic theory, and can be applied in the titanium alloy and other metal materials, it will make them have self-cleaning, inhibition of corrosion and oxidation, moistureproof and anti-icing functions. Besides the daily items, at present, other fields also need the surface technology with long life, for example aviation, it can be applied for anti-icing of the engine intake, to prevent loss of engine performance and the failure, it also can be used for other parts such as air data sensors and wing leading edge for anti-icing, to solve the increased resistance. The need in the field of electronic components and medical equipment is also very obvious.Currently, super-hydrophobic coating usually is prepared by chemical method. Although the method is simple and easy to operate, the coating has some bad properties such as low adhesion strength, poor environmental adaptability and impact resistance, often produce some failure behaviors including powdering, blistering, cracking, etc. Diamond like-carbon (DLC) films possesses excellent mechanical propertis, but has higher surface energy and poor hydrophobic performance. If the surface energy of it could be reduced by the element doping, it will improve the hydrophobicity. At the same time, if the environmental adaptability and service life of the film could be enhanced, it will greatly improve the applicability. In this thesis, Ti metal and nonmetal F doped DLC films will mainly be studied, to reveal the element doping effect on hydrophobic performance and mechanical properties. It is noticed the super-hydrophobic surface and good comprehensive performance are usually the result of a low surface energy material combinded with the rough surface morphology. So, in this thesis, WC coating prepared by supersonic flame spraying (HVOF) and micro blind holes prepared by nanosecond laser manufacturing are used to generate the microstructure of super-hydrophobic surface. Finally the doped DLC film with low surface energy is deposited on the coarse surface.The concrete research contents and results are as follows:(1) Ti-DLC film was prepared by the microwave electron cyclotron resonance (MW-ECR) plasma reactive magnetron sputtering. The film’s chemical structure and composition changing were studied, the effect of the different preparation conditions on the mechanical properties and hydrophobicity were focused on. The results showed the film was a nano-composite DLC film with TiC crystal, its nanohardness up to33GPa, abrasion losss down to12μm3, critical loading up to50, and water contact angle at a maximum of106.5°. It was found that the surface energy of Ti-DLC film increased firstly and then decreased with the increase of Ti element percentage, and the improving of the hydrophobicity was mainly owing to the changing of the chemical structure and composition.(2) The F-DLC film was prepared by the MW-ECR plasma chemical vapor deposition technique. The effect of different energy and percentage of F element on the surface morphology and chemical structure of F-DLC film was mainly studied. The change rules of the hydrophobic property and mechanical properties were focused on. The results showed that the film was composited of C-Fx (x=1,2,3) and C=C (F, H) crosslinking structure, which resulted in worse mechanical properties. For instance, the nano-hardness was generally between3GPa and2GPa, the maximal critical load was about31N, but the hydrophobic performance was greatly improved, under the optimized processing parameters, the water contact angle increased to159.2°. It was noticed that F atomic percentage content of the film had an important influence on the surface energy. With the increasing of F content, the surface energy gradually became low, when the content was32.6%, the surface energy achieved a minimum of14.74mJ/m2.(3) The influence of different morphology on the hydrophobic property was studied by three methods including ion bombardment, supersonic flame spraying and nanosecond laser processing. The super-hydrophobic surface with micro-nano secondary structure was fabricated by the micro-nano manufacturing combining with the film with low surface energy deposition. The results showed that the contact angle of the substrate showed a trend of rising with bombardment energy increasing. WC coating prepared by supersonic spraying was used as the bottom of the hydrophobic surface, and with complexity increasing of the surface morphology, the wacter contact angle of the sample gradually rose. After the microstructure was modified by the F-DLC film, the water contact angle of the sample reached the highest value of166°. The changing trend of the sample with periodic micro blind holes used as the underlying microstructure was similar to WC coating, after the modification of F-DLC film, the water contact angle reached165.6°.(4) Based on the fractal geometry theory, by projective covering method and Matlab software, the actual surface area and fractal dimension of WC coating was calculated, and the simulation value and the measured value of the water contact angle were compared and analyzed. Based on the theory of Wenzel and Cassie, the mathematical physics models of periodic micro blind hole were established, and were used for the actual surface area and water contact angle calculation. It was principally analyzed that the effect of micro blind hole structure on the hydrophobic properties of Ti alloy surface. Simulation results showed that the above microstructures could increase the actual surface area and fractal dimension of the samples, so the hydrophobic performance was further improved.更多还原