【作者】 邢俊恒；

【导师】 钟理； 夏正斌；

【作者基本信息】 华南理工大学 ， 化学工艺， 2014， 博士

【摘要】 电化学阳极氧化法制备的钛表面氧化物薄膜具有优异的耐腐蚀性、极佳的光催化活性、良好的生物相容性等诸多优点，且其制备过程简单、易于控制、成本低、无毒，因此被广泛应用于腐蚀防护、光催化降解有机污染物、光水解制氢、染料敏化太阳能电池、传感器、电池及生物医学等领域。选择合适的阳极氧化条件，可在钛金属表面形成致密型的氧化膜材料或多孔型的纳米管材料。然而，对于致密型的钛氧化膜材料来说，在不同的阳极氧化条件下钛表面阳极氧化膜的生长和结晶形成机理目前仍不是十分明确。此外，对于多孔型的阳极氧化钛纳米管材料来说，由于氟离子对钛氧化物有较强的化学攻击性，所以传统的采用含有氟离子的电解液来制备TiO2纳米管的方法有其天然的局限性。本文首先在硫酸电解液中详细研究了各种阳极氧化参数和条件对钛阳极氧化膜的生长和结晶的影响，并且探索了在不同条件下钛阳极氧化膜的生长过程和结晶机理。此外，本文还引入了一种新的、温和的含有BF4的电解液，进行了TiO2纳米管的制备及性能研究。本文的主要研究内容如下：（1）研究了不同阳极氧化模式对钛表面阳极氧化膜生长与结晶的影响。结果表明，相较于在扫描电位或者两者结合模式下所生长的氧化膜，恒电位模式下所形成的氧化膜更厚、更加粗糙，并且具有较好的结晶性。对于在恒电位模式下所生长的氧化膜，由于在钛基底表面的局部缺陷处具有非常大的电流密度，因此形成了“花瓣状”的结晶大颗粒。而对于在扫描电位或两者结合的氧化模式下所形成的氧化膜，其结晶性较为均匀，主要是由氧化膜在生长过程中的内在压应力引起的。（2）详细比较了机械打磨钛基材和溅射沉积钛基材表面所生长的钛阳极氧化膜的结构和性能。结果发现，钛基底对钛阳极氧化膜的生长和结晶有着重要的影响。在溅射沉积钛基材表面所生长的氧化膜非常光滑和致密，因此不利于电子的传输，从而不利于氧化膜的生长和结晶。（3）分别在高电位和低电位下研究了氧化时间对钛氧化膜形成和结晶的影响。研究发现，延长氧化时间有利于钛氧化膜的生长和结晶。钛的阳极氧化过程分为两个阶段，即氧化膜的生长阶段和氧化膜的老化阶段。在氧化膜的生长阶段，氧化膜的厚度和结晶度以一个较快的速度增长，而在氧化膜的老化阶段，由于氧化膜的溶解速率加快，氧化膜的厚度和结晶度的改变较小。（4）引入了一种新的含有BF4的电解液，进行TiO2纳米管的制备研究。与在常见的含有F的电解液中制备的TiO2纳米管相比，在HBF4电解液中所形成的TiO2纳米管排列规整、管壁光滑，具有特殊的双层结构，且表现出较好的光催化活性。当采用含有BF4的电解液来进行TiO2纳米管阵列的制备时，BF4离子能够在高电场的作用下分解产生F离子，这对TiO2纳米管的形成起着关键性的作用。（5）分别采用机械打磨钛、电化学抛光钛和两步法钛基底进行了TiO2纳米管的制备。结果表明，钛基底的表面形貌对TiO2纳米管的生长和性能有着重要的影响。对于两步法钛基底，通过移除掉在第一步阳极氧化中所形成的纳米管，在其表面留下了许多呈六方型均匀排列的印迹，在随后进行的第二步阳极氧化中，这些印迹扮演着类似模板的作用，可指导下层纳米管的生长。因此，在三个样品中，通过两步阳极氧化法所制备的TiO2纳米管拥有最为有序的结构和光滑的管壁，因此表现出最为优异的光电化学性能。（6）通过在含有BF4的电解液中加入乳酸或葡萄糖酸的办法来优化TiO2纳米管的形貌和性能。研究发现，相比于在普通电解液中生长的TiO2纳米管，通过乳酸或葡萄糖酸优化的TiO2纳米管具有较好的表面形貌和光催化活性。这是由于乳酸或葡萄糖酸这类弱有机酸的螯合作用能够有效地降低TiO2纳米管表面的OH基团含量，从而为TiO2纳米管的生长提供一个更加“温和”的环境，因此有利于有序而稳固的TiO2纳米管的形成。总之，本文首先在0.1mol·L-1的H2SO4电解液中制备出了致密型的钛阳极氧化物薄膜。结果表明，氧化电位、氧化时间、氧化模式、钛基材等阳极氧化条件和参数对钛氧化膜的生长和结晶都有着重要的影响。这些研究结果为钛和其他金属材料表面阳极氧化膜的形成、结晶和可控生长的知识框架提供了重要的实验和理论的依据。此外，本文还采用了一种新型的含有BF4的电解液体系成功地制备出了高度有序的TiO2纳米管阵列，且所制备的TiO2纳米管具有特殊的纳米孔/纳米管状双层结构和优异的光催化性能。通过以上的研究，获得了对TiO2纳米管在BF4溶液中的形成和生长的基本认识，从而为阳极氧化TiO2纳米管阵列的制备提供了一种新型的、不含有F的电解液体系。更多还原

【Abstract】 Titanium oxides prepared by electrochemical anodization methods possess highcorrosion resistance, excellent photocatalytic activities, good biomedical compatibility,low-cost, non-toxicity and easy-controllable, therefore have been widely used in the areas ofcorrosion protection, pollutants decomposition, water splitting, dye-sensitized solar cells,sensors, batteries and biomedicine. The preparaed anodic oxides can be either compact barrierfilms or porous nanotubes depending on the used electrolytes. However, for the growth andcrystalline mechanisms of titanium oxide films in different anodization conditions, it is stillnot very clear. Moreover, the TiO2nanotubes (NTs) formed in F contained electrolyte havetheir limitations due to the highly aggressive of F for the formed titanium oxides. In thisthesis, the effects of various anodization parameters on the growth and crystallization oftitanium oxide films in H2SO4solution are investigated in details, and the growth process andcrystalline mechanisms of titanium oxide films in different anodization conditions are alsodiscussed. In addition, a new gentle HBF4contained electrolyte is employed for thefabrication of anodic TiO2NTs. The details are presented as below:The influences of anodization modes on growth process and crystallizing mechanisms ofanodic oxide films on titanium are first studied. The results show that the potentiostaticallygrown film is thicker, rougher and more crystalline than the film formed at potential-sweepand combined modes. For titanium oxide film formed in the potentiostatic mode,“flower-like”crystalline grains are developed due to very high local current density at the local defect sitesof titanium surface. In the case of potential-sweep and combined anodization modes, thecrystallization of titanium oxide film is homogeneous, which is mainly caused by the internalcompressive stresses formed during the growth of anodic oxides.Comparisons of the structure and properties of the anodic oxides films formed on themechanically abraded bulk titanium and the sputter-deposited titanium substrates are alsopresented. The titanium substrates can largely influence the properties of the formed anodicfilms. A more smooth and compact titanium oxide film could grow on the sputter-depositedtitanium substrate, which is unfavorable to the ionic migration through the film and thendelays the film growth and crystallization. The influence of anodizing time on formation and crystallization of the potentiostaticallyformed titanium oxide films is studied both at low and high applied potentials. It is revealedthat prolonging the anodizing time is beneficial for the growth and crystallization of titaniaanodic films. The titanium anodization process follows two distinct stages. In the filmformation stage, the film thickness and crystallinity increase fast. While in the film agingstage, the thickness and crystallinity of titanium oxide films only slightly change withanodizing time due to the enhancement of film dissolution rate.A new BF4contained electrolyte is introduced for the preparation of anodic TiO2NTs.The obtained TiO2NTs are highly ordered and extremely smooth, have unique hierarchicalupper-nanoporous and lower-nanotubular structure, and show enhanced photocatalyticactivities than the TiO2NTs formed in common used F contained electrolyte. It is consideredthat the decomposition of BF4into F under high electric field is the key for the formation ofanodic TiO2NTs in BF4contained electrolyte.Three different Ti substrates, the rough abraded Ti foil, the smooth electropolished Ti andthe two-step Ti plate, are employed for the preparation of TiO2NTs. It is revealed that the Tisubstrate morphology can largely influence the formation of TiO2NTs. The two-step Tisubstrate has ordered hexagonally distributed dimples which play the role of template for theformation of new TiO2NTs. As a result, the TiO2NTs grown via a two-step anodizationapproach have highly ordered structure and extremely smooth sidewalls, hence possess thebest photoelectrochemical performance among the three kind of substrates.The morphology and properties of anodic TiO2NTs are also improved by adding lacticacid or gluconic acid to the unique BF4contained electrolyte. It is shown that with specificadditives to the solution, the geometrical morphology and application properties of theobtained TiO2NTs can be significantly enhanced. We ascribe this improvement to thedecrease of surface OH groups content on TiO2NTs, which is related to the chelating effect ofthe added weak organic acids.In general, the compact titanium oxides barrier layers are first prepared in0.1mol·L-1H2SO4solution. It is shown that the growth and crystallization of titanium oxide films aredetermined by the anodizing potential, time, anodization mode and titanium substrate. Theabove results are beneficial for the understanding of the formation, growth and crystallization mechanisms of anodic films on titanium or other metals. Moreover, ordered anodic TiO2NTsare successfully prepared in a new BF4contained electrolyte. The obtained TiO2NTs haveunique nanopore/nanotube hierarchical structure and show enhanced photocatalytic properties.The research provides an alternative way for the preparation of TiO2NTs with F freeelectrolyte.更多还原