从壁垒型氧化膜生长过程研究PAA的生长机制

为研究PAA的生长机理,设计了铝在3种电解液中的阳极氧化,通过SEM和阳极氧化曲线详细分析了规则圆柱形孔道和表面不规则孔洞产生的原因.电解液中阴离子使氧化膜变成了壁垒层和污染层两层.雪崩电子电流导致了在壁垒层/污染层界面上O2的析出.PAA中圆柱形孔道的形成是氧气析出的结果,传统的"酸性场致溶解"只在表面形成不规则的孔洞.当电解液中磷酸含量减少后,氧气析出持续的时间降低,O2析出停止后,多孔孔道被新生成的氧化铝封堵,最后PAA膜转变成BAA膜.     

多孔阳极氧化铝模板的影响因素

近年来,随着纳米技术的发展,研究制备具有纳米孔结构的氧化铝多孔膜越来越受到人们的关注.多孔阳极氧化铝(porous anodic alumina,PAA)薄膜具有易于制备,工艺简单,且价格便宜等诸多优点而被广泛地应用于各个领域.为了制备出性能更加优越的PAA模板,各国学者都对其进行了一些研究.但目前的研究大都不系统,针对这一问题,作者进行了大量的实验,通过实验总结出了PAA模板的主要影响因素,并分别讨论了这些影响因素对模板的有序度、孔密度和模板厚度的影响.     

Oxygen evolution and porous anodic alumina formation

A new formation mechanism of porous anodic alumina (PAA) is proposed, which emphasizes the close relationship between pore generation and oxygen evolution during aluminum anodization. Two special experiments were designed to confirm the formation mechanism: (1) to introduce a reducing agent in anodization for oxygen suppression, and (2) to perform anodization under a reduced pressure for easy oxygen release. The results showed that both reducing agent and atmospheric pressure had a great effect on the morphology of the resultant film. This can be expected on the basis of our hypothesis about the formation mechanism of PAA, but cannot be easily explained by the existing theories.     

Mechanical behavior of anodic alumina coatings reinforced with carbon nanofibers

Anodic alumina was reinforced with three types of carbon nanofibers differing in the orientation of their graphene structure—perpendicular to the fiber axis, and parallel to the fiber axis both with dense core and hollow core (i.e., nanotubes). This study was designed to identify potential toughening and damage tolerant mechanisms in these nanoscale fiber-reinforced composite coatings. The dense carbon fibers improved contact damage resistance and reduced frictional resistance in sliding contacts. The hollow core reinforcements were much more promising for improving the fracture toughness of the composite coatings.     

高度有序多孔阳极氧化铝模板的制备

为了得到纳米孔排列高度有序的多孔阳极氧化铝模板,以0.3 mol·L-1的草酸为电解液研究了模板的制备工艺.采用场发射扫描电子显微镜(FE-SEM)对多孔氧化铝模板的表面形貌进行表征,X射线衍射分析高纯铝及氧化膜的结构.实验结果表明,铝基体不经过高温退火处理,同样能够得到高度有序的氧化铝膜,简化了多孔氧化铝膜的制备工艺.分别讨论了阳极氧化电压和电解液温度对多孔阳极氧化铝膜的形貌及孔径的影响,并对一步法和两步法制得的多孔氧化铝膜进行比较,结果表明,两步阳极氧化法制备的多孔氧化铝模板的有序性优于一步氧化法.XRD分析证实,多孔氧化铝膜由非晶态的Al2O3组成.     

两步阳极氧化法制备多孔阳极氧化铝膜

直流恒压下,在酸性溶液中对铝实施两步阳极氧化制备了多孔氧化铝膜。采用扫描电镜(SEM)、原子力显微镜(AFM)对制备的多孔氧化铝膜进行形貌分析,孔径在纳米级且孔分布具有高度均匀性。采用SEM对试样进行观察,分析了工艺对多孔氧化铝膜形貌的影响。利用阳极氧化初期电流密度的变化并结合阳极氧化过程中的试样的SEM照片,分析了多孔氧化铝膜的形成机理。     

无阻挡层多孔阳极氧化铝膜板的制备

提出一种在中性的KCl溶液中用多孔阳极氧化铝作阴极,通过电解在阴极产生OH-腐蚀阻挡层,制备无阻挡层氧化铝模板的新方法.用扫描电镜对模板进行了表征.结果表明,在草酸溶液中,制得的氧化铝模板孔径为70～80nm,孔间距为130nm,孔密度约8×109/cm2,这种方法去阻挡层不扩大模板孔径,不影响纳米孔的纵横比.无阻挡层的氧化铝模板适合于直流电沉积和无电沉积金属纳米材料.     

Formation of complex anodic films on porous alumina matrices

The kinetics of growth of complex anodic alumina films was investigated. These films were formed by filling porous oxide films (matrices) having deep pores. The porous films (matrices) were obtained voltastatically in (COOH)₂ aqueous solution under various voltages. The filling was done by reanodization in an electrolyte solution not dissolving the film. Data about the kinetics of reanodization depending on the porosity of the matrices were obtained. On the other hand, the slopes of the kinetic curves during re-anodization were calculated by two equations expressing the dependence of these slopes on the ionic current density. A discrepancy was ascertained between the values of the calculated slopes and those experimentally found. For this discrepancy a possible explanation is proposed, related to the temperature increase in the film, because of that the real current density significantly increases during re-anodization.     

多孔阳极氧化铝模板的制备及其光学特性研究

采用二次阳极氧化法获得分布均匀、有序的纳米多孔阳极氧化铝模板（PAAT），对其形貌、相结构及光学性能进行了表征和分析。光吸收测试发现多孔阳极氧化铝模板在250nm处有一个吸收峰，可见光区是透明的。光致发光测试表明多孔阳极氧化铝模板在450-550nm之间有一个较宽的蓝色发光带，发光峰在460nm左右。     

Formation of porous anodic alumina in alkaline borate electrolyte

The growth of porous anodic films at 60 V in an alkaline 0.13 M borax electrolyte at 333 K is examined using sputtering-deposited aluminium substrates, with a fine band of incorporated tungsten tracer. The findings reveal amorphous alumina films containing approximately conical major pores incorporating finer secondary pores, with film thicknesses similar to that of the oxidized aluminium. Further, the distribution of the tungsten tracer within the film is mainly consistent with its expected migration behaviour in anodic alumina. The results indicate that pore development under the present growth conditions is dominated by field-assisted dissolution of anodic alumina, with an efficiency of film growth of about 50%. The findings are in contrast with those of porous anodic films formed in phosphoric acid electrolyte, which are significantly thicker than the layer of oxidized metal.     

Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.     

Indium oxide nanorods and nanowires on porous anodic alumina

We report indium oxide nanorods and nanowires with controllable microstructure deposited on porous anodic alumina membranes (PAAs). At the beginning of the deposition, indium oxide tends to nucleate on the top of PAAs, not at the bottom of PAAs' nanopores, and grows into nanorods. It is interesting that the indium oxide nanorods on the top of PAA just copy the topography of PAA, and form a new porous layer with the thickness of 40-50 nm. As the deposition goes on, the nanorods cannot maintain the ordered nanopore structure, and evolve into nanowire net. And the nanowires can stand upwards separately, and then fall down as the length goes up, forming an indium oxide entangled nanowires. The structure evolvement is discussed according to the field emission scanning electric microscope images.     

Reduction of nanoparticle deposition during fabrication of porous anodic alumina

In this paper, we present evidences of nanoparticle deposition on porous anodic alumina (PAA) surface under different anodizing conditions, and discuss the formation mechanism of precipitations. Low-temperature anodization, vigorous stirring and ultrasound-assisted anodization are proposed to reduce the hydrolysis product or hinder its deposition on the surface as well as inside nanopores of PAA. It is discovered that the ultrasound is very efficient to prevent the deposition of Al³⁺ hydrolysis product on PAA. This study is of great value for realizing ordered PAAs with clean surface.     

Ultrafast excited state deactivation of doped porous anodic alumina membranes

Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5-150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the F?rster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor-acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics.     

铜纳米线阵列的模板组装

采用电解法溶解多孔阳极氧化铝(PAA)模板的阻挡层,用直流电沉积的方法在模板中组装了铜纳米线阵列.分别用扫描电镜和X射线衍射表征铜纳米线阵列的形貌和晶体结构,用电化学法表征了铜纳米线阵列的电催化性能.结果表明,PAA去阻挡层后,伏安图上出现一个阳极氧化峰.恒电位沉积的铜纳米线直径为22nm,沿(111)晶面择优取向.铜纳米线阵列电极能催化亚硝酸根的还原,其催化电流比本体铜电极上大2倍,峰电位正移80mV.纳米铜阵列电极可用于亚硝酸盐的电化学检测.     

Synthesis of metallic nanotube arrays in porous anodic aluminum oxide template through electroless deposition

Ordered Co, Ni and Cu nanotubes embedded in a porous anodic aluminum oxide (AAO) membrane were fabricated by electroless deposition. The results show that the length of the nanotubes is determined by the thickness of the AAO template and the outside diameter of the nanotubes is determined by the pore size of the AAO template. The factors that impact on the growth of metallic nanotubes are also discussed.     

Room-temperature photoluminescence from porous anodic alumina films with embedded terbium and europium species

Strong room-temperature terbium and europium photoluminescence, with well-resolved optical bands corresponding to electron transitions ⁵D₄→⁷F_j (j = 3–6) for Tb³⁺, and ⁵D₀→⁷F_j (j = 1–4) for Eu³⁺, was observed from porous anodic alumina films of 5–55 µm thickness after immersion in solutions of terbium or europium nitrates and subsequent heat treatment. GDOES and TEM examinations of the specimens treated with terbium ions revealed a uniform distribution of terbium across the porous anodic film thickness of 55 µm, with an increased terbium concentration toward the pore bases. Europium- and terbium-doped specimens displayed anisotropic indicatrix of luminescence for the emission wavelength of 613 nm for europium and 545 nm for terbium, with a maximum intensity in the direction along the channels of the pores that is typical for porous anodic alumina with lanthanide ions within the pores. The potential applications of porous anodic alumina doped with lanthanides through immersion in the absence of xerogel are discussed.     

Sputter deposition of self-organized nanoclusters through porous anodic alumina templates

Silver nanoparticles were sputter deposited through self organized hexagonally ordered porous anodic alumina templates that were fabricated using a two-step anodization process. The average pore diameter of the template was 90 nm and the interpore spacing was 120 nm. Atomic force microscope studies of the sputter-deposited silver nanoparticle array on a Si substrate indicate an approximate replication of the porous anodic alumina mask. The nature of the deposition depends strongly on the process parameters such as sputtering voltage, ambient pressure and substrate temperature. We report a detailed study of the sputtering conditions that lead to an optimal deposition through the template.     

Conductive super-hydrophobic surfaces of polyaniline modified porous anodic alumina membranes

A conductive polymer polyaniline (PANI) was employed to achieve surfaces of both super-hydrophobic and conductive on NaOH etched porous anodic alumina (PAA) membranes. The surfaces exhibit micro- and nanostructures. In the PANI modified PAA membrane, PANI is mainly emeraldine. After the membrane was immersed in HCl, the content of the protonated nitrogen increased, which increased the conductivity.