摘要
钽是一种难熔金属，具有优异的物理化学性能，广泛应用于工业中。由于金属晶粒取向的不同，表现出不同的物理化学性能。在化学或电化学腐蚀的过程中，不同取向的晶粒具有不同的腐蚀敏感性，即腐蚀取向相关性。本文利用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和表面轮廓仪等实验手段，对再结晶和轧制态的高纯多晶钽腐蚀取向相关性进行了系统研究。钽金属经阳极氧化后会生成多孔结构的Ta2O5氧化膜和Ta2O5纳米管，但此研究并不广泛，本文首先通过优化阳极氧化制备Ta2O5纳米管的制备工艺，并制备出形貌质量优良的Ta2O5纳米管。随后利用SEM、XRD、纳米压痕仪和光催化仪器，对钽金属阳极氧化生成的Ta2O5纳米管薄膜的取向相关性进行了系统的研究。获得以下主要结论：
①两种不同状态的高纯多晶钽（再结晶态和轧制态）在H2SO4 / HNO3/ HF 溶液中腐蚀后，不同取向晶粒的腐蚀速率和腐蚀形貌不同。再结晶态样品中不同取向晶粒的腐蚀速率表现为(111)>（110）>（100）。此外，不同取向晶粒的腐蚀形貌表现为不同特征，（111）晶粒表面由许多“包”状物构成；（110）晶粒表面呈“沟壑”状；（100）晶粒表面布满了“浅坑”。通过对不同取向的晶粒表面原子层信息的分析，表面原子层排列的紧密程度和晶粒表面自由能的大小影响了钽金属的腐蚀行为。轧制态钽金属在变形的过程中，（111）晶粒出现大量的小角度晶界，这些小角度晶界是位错聚集处，相对于（100）晶粒具有较高的储存能。因此，在腐蚀的过程中会首先被腐蚀，且腐蚀后的表面由很多不均匀的“包”状物构成，相比于再结晶态样品，晶粒表面更为粗糙。本文通过对钽金属腐蚀取向相关性的研究，有望通过
改善样品的内部显微组织结构改善金属的抗腐蚀性能。
爱之链②在特定的电解液、电压和时间下对钽金属进行阳极氧化可制备出Ta2O5纳米管。通过优化前期处理工艺，可制备出形貌质量优良的Ta2O5纳米管。钽样品首先在体积比为9:1的H2SO4/ HF电解液中电解抛光，Ta2O5纳米管被抛除后，样品表面仅保留一层多孔结构的Ta2O5薄膜，并以此多孔结构薄膜的样品为基础再进行阳极氧化，可获得开口率高、管壁光滑、表面没有氧化物残留的Ta2O5纳米管。通过控制变量法改变电压和氧化时间，可以制备出管长管径可控的Ta2O5纳米管。试验结果表明电压是影响Ta2O5纳米管生成的主要因素，在低电压5 V以下，样品表面将不会生成纳米管薄膜。
③对阳极氧化生成的Ta2O5纳米管进行物相分析，试验结果表明此结构为无定形态，在充满氩气的管式炉中900 o C退火30 min，Ta2O5纳米管由无定形态转变为结晶态并失去管状结构。对阳极氧化直接生成的Ta2O5纳米管、纳米管退火后的
粉末和商业用200 nm Ta2O5颗粒粉末分别进行光催化性能测试，测试结果表明阳极氧化直接生成的Ta2O5纳米管具有较高的光催化性能，光催化率达到93%；Ta2O5纳米管退火后的粉末和商业用的200 nm Ta2O5颗粒粉末没有光催化性能。
④对（111）、（110）和（100）取向单晶在同等条件下进行阳极氧化，研究了纳米管生成的取向相关性。（111）取向单晶首先生成Ta2O5纳米管，在相同的氧化时间下纳米管长度最长；（110）和（
100）单晶生成的纳米管薄膜具有类似的表面形貌，但（100）取向单晶生成的纳米管管长略长。（111）取向的单晶具有较高的表面自由能，由阳极氧化动力学曲线分析可知，在阳极氧化的第一阶段（111）单晶的电流密度首先下降，并生成致密氧化膜；在阳极氧化的第二阶段电流密度首先回升，生成纳米孔结构。因此（111）晶体在同等条件下阳极氧化生成的纳米管最长。利用纳米压痕仪对三种单晶生成的Ta2O5纳米管薄膜做力学性能测试，（111）单晶的硬度和弹性模量最大。因此，也可以通过改善晶体取向来获得形貌及性能可控的Ta2O5纳米管。
关键词：高纯钽，晶体取向，腐蚀，阳极氧化，Ta2O5纳米管
使满意的英文ABSTRACT
布依族Tantalum is a refractory metal with excellent physical and chemical properties. High purity polycrystalline tantalum is widely ud in the industry. The different grain orientations of polycrystalline metals prent different physical and chemical properties. In the process of chemical or electrochemical corrosion, different grain orientations cau different corrosion nsitivity, which is called corrosion orientation correlation. In this thesis, Orientation-dependent corrosion behaviors of high-purity Tantalum under recrystallization and rolled were studied by multiple characterization methods, such as the Scanning Electron Microscope (SEM), Electron Back Scattering diffraction (EB
SD) and surface profile instrument. Ta2O5 oxide film and Ta2O5 nanotube were fabricated using an electrochemical anodic oxidation method, but which isn’t widely rearched. The quality of surface morphology of anodic Ta2O5 nanotube was improved by optimizing the pretreatment of tantalum template, and orientation-dependent anodic of Ta was studied using SEM, XRD, nanoindentation and light catalytic instrument. Main conclusions can be drawn:
①The corrosion rate and morphology were dependent on grain orientations, when high purity polycrystalline Ta (recrystallization and cold rolled) were etched in the acid etching solution of H2SO4 / HF / HNO3. The corrosion rate of the grain orientation of the crystalline sample was (111) > (110) > (100)，and (111) grain orientation was compod of many “bags” appearance on the surface, the surface of (110) grain orientation prented step-shaped appearance, while the surface of the (100) grain was covered with a large numbers of “shallow pit” appearance. The analysis was bad on the information of the atom layer on the grain surface. The corrosion behavior was affected by the arrangement of atom layer and free energy of the grain. The (111) grain of cold rolled Ta showed a lot of small angle grain boundaries and strong dislocation density, which was higher storage energy and more easily corroded than (100) orientation. The surface of (111) grain corroded with many uneven “bags” was rougher than the recrystallization sample. The study of orientation-dependent corrosion behavior is expected to improving the corrosion resistance of tantalum.
② Ta2O5 nanotube was fabricated using anodic oxidation method and the quality surface morphology was improved by optimizing the pretreatment of tantalum. The results show that high aperture ratio and smooth-wall anodic Ta2O5 nanotube without
oxide residue was obtained by introducing an electropolishing procedure before anodic oxidation. The length and diameter of Ta2O5 nanotube were controlled by changing voltage and oxidation time, and the voltage was the main influence factors. The sample was not generated the nanotube film under low voltage of 5 V.
③Analysis results of XRD showed that anodic Ta2O5 nanotube was amorphous and turned into crystalline state and lost the tubular structure after annealing for 30 min at 900 o C in filled with argon gas. The photocatalytic of anodic Ta2O5 nanotube, nanotube annealed and commercial 200 nm Ta2O5 powder were tested. The results show that the anodic Ta2O5 nanotube prented high photocatalytic performance of 93%, while the powder of nanotube annealed and 200 nm Ta2O5 particle didn’t prent photocatalytic performance.
④ In this paper, three kinds of single crystals with (111), (110) and (100) orientation were oxidized under the same condition to study the orientation correlation with nanotube. The crystal plane with (1
11) was first generated the nanotubes, which was the longest. Nanotube films fabricated on single crystals with (110) and (100) were similar morphology, and the length of nanotube on the single crystal with (110) was longer. The single crystal with (111) orientation had higher surface free energy. Been bad on the anodic oxidation kinetics, the den oxide film was first generated on the crystal with (111) orientation with the current density dropping in the first stage. In the cond stage, the nanopore structure was first generated with rising of the current density, so the length of nanotube with (111) single crystal was the longest under the same condition of anodic oxidation. Mechanical properties of nanotube films fabricated on the three kinds of crystals were tested, parately. The hardness and elastic membrane volume of nanotube film with (111) single crystal were the largest, and single crystal with (110) and (100) had similar hardness and elastic membrane. Therefore, it is also possible to obtain controllable Ta2O5 nanotubes by improving the crystal orientation.
Keywords: high-purity Tantalum, crystal orientation, corrosion, anodic oxidation, Ta2O5 nanotube
雷雨在线阅读目录
中文摘要 ........................................................................................................ I 英文摘要 ...................................................................................................... III 1 绪论 .. (1)
1.1 课题背景和意义 (1)
1.2 文献综述 (2)
1.2.1 织构 (2)
1.2.2 腐蚀的取向相关性 (5)
1.2.3 阳极氧化法制备纳米管薄膜 (7)
1.3 研究内容 (13)
2 实验材料及研究方法 (15)
2.1 实验材料、试剂、仪器 (15)双子和水瓶配对
2.1.1 实验材料 (15)
2.1.2 实验试剂 (15)
2.1.3 实验仪器 (16)
自然景物
2.2 技术路线 (16)akg官网
2.2.1 高纯钽多晶腐蚀 (17)
2.2.2 高纯钽阳极氧化 (17)
2.3 实验过程 (18)
2.3.1 多晶高纯钽腐蚀 (18)
2.3.2 Ta2O5纳米管制备 (18)
2.4 材料表征与性能评价 (18)
2.4.1 EBSD (18)
2.4.2 SEM (19)
2.4.3 XRD (19)
焦急的反义词2.4.4 表面轮廓 (20)
2.4.5 光催化性能 (20)
2.4.6 纳米压痕 (21)
2.5 本章小结 (22)
3 钽腐蚀取向相关性的研究 (23)
3.1 再结晶态钽金属腐蚀的取向相关性 (24)
3.2 轧制态钽金属腐蚀的取向相关性 (25)
