【作者】 李启征；

【导师】 左禹；

【作者基本信息】 北京化工大学 ， 材料学， 2009， 博士

【摘要】 本文采用了三种方法（水滑石前驱法前处理铝基体、阳极氧化液中添加稀土盐以及稀土盐封闭氧化膜）来制备稀土改性铝阳极氧化膜,利用动电位极化和电化学阻抗谱（EIS）研究了阳极氧化膜的腐蚀行为,利用扫描电子显微镜（SEM）观察了阳极氧化膜的表面形貌,用能谱（EDXA）和X射线光电子能谱仪（XPS）分析了氧化膜的表面成分。利用水滑石前驱法分别在含有稀土盐（Ce（NO₃）₃、Nd（NO₃）₃）的MgCl₂和Ni（NO₃）₂溶液中对高纯铝Al-05进行前处理,在铝表面生成二元（AlMg和AlNi）双羟基金属氧化物,再经过阳极氧化制备得到稀土改性铝阳极氧化膜。研究了稀土盐浓度、处理时间、处理温度和pH值对水滑石前驱法产物中稀土含量的影响,在1mol/L MgCl₂溶液前处理中,处理时间1小时,温度80℃,pH=9,50g/L Ce（NO₃）₃和50g/L的Nd（NO₃）₃,在形成的水滑石金属氧化物中,稀土的含量均能接近最大;在1mol/L Ni（NO₃）₂溶液前处理中,处理时间1小时,温度90℃,pH=8,75g/L Ce（NO₃）₃和85g/L的Nd（NO₃）₃,在形成的水滑石金属氧化物中,稀土的含量均能接近最大。对铝阳极氧化膜研究发现氧化膜的生长速度提高了10%左右,氧化膜更加致密,多孔层孔洞直径从80nm～90nm减小到40nm左右,氧化膜中含有稀土化合物,它们分别是CeO₂、Ce₂O₃和Nd₂O₃,但是氧化膜的晶态没有因此改变,仍然是非晶态,极化曲线结果表明改性氧化膜在中性（pH=7）、酸性（pH=2）和碱性（pH=12）NaCl溶液中的耐蚀性都明显提高,交流阻抗发现改性氧化膜的阻挡层和多孔层的阻抗都增大。过改性以后氧化膜的半导体特性从n型转变为p型。研究了在硫酸电解液中添加稀士盐以后,对高纯铝Al-05进行阳极化处理,通过分析阳极氧化膜的成分和显微结构,结合电化学测试结果,分析了稀土元素在铝阳极氧化过程中的作用。结果发现稀土元素能够加快氧化膜的生长速度,改性氧化膜的膜厚提高了5%左右,同时氧化膜孔洞变小,显微硬度提高,最高达到132,是普通硫酸氧化膜的1.6倍,电化学分析表明复合稀土改性对耐蚀性提高的作用最大,单一Ce盐比单一Nd盐的效果要好。采用一种简单的封闭工艺将稀土元素引入铸铝201阳极氧化膜,利用铈盐和钕盐的协同效应,提高了铝阳极氧化膜的耐蚀性,开发了一种环保,操作简单的绿色封闭方法。更多还原

【Abstract】 In this paper,three methods（pre-treatment by precursor method, anodic oxidation solution containing rare earth（RE） salt and rare earth sealing） to the preparation of rare earth modified anodized aluminum alloy.Potentiodynamic polarization and electrochemical impedance spectroscopy（EIS） were used to study the corrosion behavior of rare earth modified anodic oxide film.The anodic film surface was observed by scanning electron microscopy（SEM）,the composition of the oxide film was analized by energy dispersive X-ray analysis（EDXA） and X-ray diffraction（XRD）.By the precursor method in MgCl₂ solution containing rare earth salts,rare earth was introduced into AlMg-LDHs hydrotalcite on the high purity aluminum surface,which was then anodized,Al-Mg-RE complex anodic oxide films were got.The influences of rare earth concentration, processing time,processing temperature and pH value on rare earth content in hydrotalcite were studied.Highest content of RE was found in the AlMg-LDHs hydrotalcite on the aluminum surface,which was treated in 1 mol/L MgCl₂ solution（80℃and pH=9） with 50g/L Ce（NO₃）₃ and 50g/L的Nd（NO₃）₃ for 1 hour.Using the same method,highest content of RE was found in the AlNi-LDHs hydrotalcite on the high purity aluminum surface,which was treated in 1mol/L Ni（NO₃）₂ solution（90℃and pH=8） containing 75g/L Ce（NO₃）₃ and 85g/L Nd（NO₃）₃,for 1 hour. RE complex anodic oxide films display better performance in chemical properties and mechanical properties.It was found that the rare earth modified oxide film were more compact with much smaller pores and increased hardness,hole diameter reduced from 80～90 nm to 40 nm.The film thickness analysis result showed that average growth rate of modified anodic films raised up to 110%.XPS analysis showed that Ce is present in the film as CeO₂ and Ce₂O₃,and Nd is present as Nd₂O₃. Modified oxide films were still typically amorphous the same as that of usual anodic aluminum.In neutral,acidic and basic NaCl solutions,the rare earth modified films showed obviously improved corrosion resistance.The effect of element Ce on increasing corrosion resistance of the film is better than that of Nd.The rare earth salt modified anodic films showed higher R_p value and lower C_p than those of the anodic film on pure aluminum in neutral NaCl solution.The semiconductor function of rare earth modified anodic films is changed from n-type to p-type.The properties of anodic films on purity aluminum formed in sulfuric acid electrolyte containing rare earth salt were studied.The role of rare earth element in the process of anodizing was analyzed by component test、microstructure observation and electrochemical test.The results showed that rare earth elements can accelerate the growth rate of aluminum oxide film about 5%,and also decreased porosity and increased hardness.Compared with anodic films modified by single rare earth salt,electrochemical test showed that the anodic film modified by compound rare earth salts has better corrosion resistance.The element Ce showed better effect on increasing corrosion resistance of the film than Nd.This research studied the no-toxic materials in sealing methods for anodic films on ZL201 aluminum alloy,and Ce and Nd were introduced in aluminum anodic film.Using compound sealing with Ce salt and Nd salt,the corrosion resistance of the anodic film was great improved.The sealed anodic film has been developed to improve the corrosion resistance of anodic films without the use of chromates and nickelates.更多还原