阳极氧化法制备大面积双面多孔氧化铝膜及其应用

室温下,以纯铝箔为基材,采用二步阳极氧化法,在0.3 mol/L草酸溶液中制备了大面积的双面氧化铝膜.在氧化过程中,电流呈现降低、升高、平稳、再降低的变化,最后接近于零.X射线衍射结果显示,双面氧化铝膜为无定型结构.扫描电镜结果显示:每面氧化铝膜的总厚度约为50 μm,孔径分布为50～100 nm.利用制得的双面氧化铝...     

高度有序多孔阳极氧化铝制备工艺的研究

影响多孔阳极氧化铝(porous anodica lumina,PAA)形貌及结构等的因素有很多,如抛光铝片的表面粗糙度、电解液温度、氧化电压、氧化时间、搅拌速率等。本文采用二次阳极氧化法,以草酸为电解液,研究了高度有序AAO模板制备过程的主要工艺条件,并采用扫描电子显微镜对模板的形貌进行表征。结果表明,在电解液温度为12℃,氧化电压为40V能够得到高度有序的、孔径为80nm左右的多孔阳极氧化铝膜。     

AAO模板的制备及其应用

以多孔阳极氧化铝膜为模板制备纳米结构材料具有独特的优越性,得到了广泛的关注。本文介绍了在草酸溶液中制备的AAO模板的工艺过程,并用扫描电子显微镜（SEM）对阳极氧化铝膜的形貌和结构进行了表征,最后介绍了AAO组装体系的应用。     

金属在多孔氧化铝膜中直流电沉积的研究

采用二次阳极氧化法,制备得到了高度有序的氧化铝多孔模（AAO）。通过实时监控高纯铝的阳极氧化以及模板的电沉积过程电流-时间关系,研究了AAO。制备的自组装过程和直流电沉积的模板导电性能。文章着重分析了扩孔时间对阻挡层的去除的影响,发现扩孔时间越长,阻挡层溶解率越大。结合扫描电镜（sEM）、X射线能谱（EDs）,对所制备模板和沉积物进行了表征。     

Magnetization reversal of Co/Pd multilayers on nanoporous templates

By making use of an e-beam deposition system, the [Co(2 Å)/Pd(10 Å)]₁₅ multilayers were prepared on a Si(100) substrate and anodized aluminum oxide [AAO] templates with average pore diameters of around 185, 95, and 40 nm. The mechanism of magnetization reversal of the Co/Pd multilayers was investigated. Wall motion was observed on the Co/Pd multilayers grown on the Si substrate. A combination of wall motion and domain rotation was found in the sample grown on the AAO template with a 185-nm pore diameter. For the samples grown on the AAO templates with pore diameters of around 95 and 40 nm, the reversal mechanism was dominated by domain rotation. The rotational reversal was mainly contributed from the underlying nanoporous AAO templates that provided an additional pinning effect.PACS: 75.30.Gw, magnetic anisotropy; 78.67.Rb, nanoporous materials; 75.60.Jk, magnetization reversal mechanisms.     

Morphological and chemical characterization of highly ordered conical-pore anodic alumina prepared by multistep citric acid anodizing and chemical etching process

Highly ordered, conical-pore anodic alumina (AAO) membranes with interpore distance (D _c ) between ca. 530 and 620 nm and thickness ranging between 2.4 and 7.8 μm, were produced. In the fabrication process aluminum surface was first pre-patterned by the anodization in etidronic acid solution. Then, the regular arrays of Al concaves were used as nucleation sites to grow AAO during the second anodization, which was carried out in highly concentrated citric acid solution (20 wt%) and at relatively high temperature (33–35?°C). The conical pore shape was engineered by a multistep process combining anodization in the citric acid electrolyte and the subsequent chemical pore broadening in phosphoric acid solution. The morphological analyses has revealed that the geometrical parameters of the Al concaves were successfully transferred to the AAO membranes. Furthermore, FTIR spectra analysis confirmed that the electrolyte species, such as phosphonate and citric ions, are being embedded into the AAO framework during the anodization. The graded-index structure formed in AAO can be used for a production of antireflective coatings operating in a broad spectral range.     

Effects of anodization and electrodeposition conditions on the growth of copper and cobalt nanostructures in aluminum oxide films

Anodic aluminum oxide (AAO) films were prepared by alternative current (ac) oxidation in sulfuric acid and phosphoric acid solution. The porous structure of the AAO templates was probed by ac electrodeposition of copper. AAO templates grown using an applied square waveform signal in cold sulfuric acid solution exhibit a greater pore density and a more homogeneous barrier layer. UV–vis–NIR reflectance spectra of the Cu/AAO assemblies exhibit a plasmon absorption peak centered at 580 nm, consistent with the formation of Cu nanostructures slightly larger than 10 nm in diameter. Spectroscopic data also indicate that there is little or no oxide layer surrounding the Cu nanostructures grown by ac electrodeposition. The effect of pH of the cobalt plating solution on the magnetic properties of the Co/AAO assemblies was also investigated. Co nanowire arrays electrodeposited at pH 5.5 in H₂SO₄-grown AAO templates exhibit a fair coercivity of 1325 Oe, a magnetization squarness of about 72%, and a significant effective anisotropy. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Tailoring the nanostructure of anodic aluminum oxide cladding on optical fiber

We report a comprehensive investigation of fabricating nanostructured anodic aluminum oxide (AAO) cladding on optical fiber. We show that the pore size and interpore distance in the AAO cladding with pore channels vertically aligned to fiber surface can be readily controlled by applied voltage, the type, and concentration of electrolytic acid during anodization of aluminum‐coated optical fiber. The structural characteristics of the AAO cladding were examined by scanning electron microscopy (SEM) and analyzed using ImageJ software. Processing maps correlating AAO growth and anodization parameters were established. Compared to planar AAO growth on aluminum foil, higher growth rate as well as larger pore diameter and interpore distance were observed for AAO cladding formation on optical fiber under identical anodization conditions due to circumferential tensile stress in the AAO growth front at the convex AAO/aluminum interface. This tensile stress also contributed to radial cracking of the AAO cladding upon exceeding some threshold thickness.     

Preparation of solid acid catalyst packing AAO/SBA-15-SO3H and application for dehydration of xylose to furfural

The solid acid catalyst packing AAO/SBA-15-SO₃H was prepared by the co-condensation and grafting method with porous anodic aluminum oxide (AAO) as support. FT-IR, SEM and TEM were applied to characterize the prepared samples. Results showed that catalysts prepared by two methods both contained active centers, and SBA-15 nanorod arrays grow inside a porous alumina membrane AAO and are perpendicular to the substrate. Their catalytic performances were tested for dehydration of xylose to furfural. The conversion of xylose and selectivity of furfural were 90% and 74% on the AAO/SBA-15-SO₃H(C) catalyst prepared by the co-condensation method, respectively. The deactivation and regeneration of the AAO/SBA-15-SO₃H(C) catalyst for the dehydration of xylose were also investigated, the activity of catalyst treated by 30 wt.% H₂O₂ almost was recovered.     

Through-hole membranes of nanoporous alumina formed by anodizing in oxalic acid and their applications in fabrication of nanowire arrays

The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried out in 0.3 M oxalic acid at the temperature of 20 °C. This relatively high temperature shortens significantly the anodizing time and allows to fabricate quickly thick through-hole membranes without the additional operating cost of a cooling circuit. The structural features of anodic porous alumina such as pore diameter, interpore distance, porosity, pore density and pore circularity were investigated at various durations of pore opening/widening process carried out in 5% H₃PO₄. An excellent agreement of AAO structural features measured in FE-SEM images of the studied samples with results from software calculations was observed. The pore shape can be monitored qualitatively by fast Fourier transforms (FFTs) and quantitatively by calculation the percentage of pore circularity. Additionally, the regularity of the hexagonal arrangement of nanopores in through-hole AAO membranes was compared for various opening/widening time ranging from 40 to 100 min. It was shown that three-dimensional (3D) representations of FE-SEM images and their surface-height distribution diagrams provide interesting information about the surface roughness evolution during the pore opening/widening process. A template-assisted fabrication of Ag and Sn nanowire arrays by electrochemical deposition into the pores of the prepared AAO templates was also successfully demonstrated.     

Mechanistic study of cobalt catalyzed growth of carbon nanofibers in a confined space by plasma-assisted chemical vapor deposition

Carbon nanofibers (CNFs) were grown in the porous anodic aluminum oxide (AAO) thin film grown on the Si wafer by electron cyclotron resonance chemical vapor deposition using cobalt as the catalyst. A larger Co particle electrodeposited in the AAO pore channel produced vertically aligned CNFs with a tube diameter in compliance with the pore size of the AAO template. On the other hand, a smaller Co particle resulted in CNF growth with a nonuniform distribution of the tube diameter and a sparse tube density. Amorphous carbon residue produced under the plasma-assisted CNF growth condition seemed to play an essential role leading to the observation. A growth mechanism is proposed to delineate the volume effect of the electrodeposited Co catalyst on the CNF growth confined in pore channels of the AAO template.     

Assembly of one-dimensional polymer nanostructure arrays by photolithographic approaches

In this work, large area polymer nanostructure arrays with different patterns were successfully obtained by photolithographic approach and wetting anodic aluminum oxide (AAO) templates. First of all, the AAO templates with patterns were produced by photolithographic approach. Then the AAO/pattern membrane was used as a secondary template to fabricate polymer nanostructure arrays by solution-wetting and melt-wetting methods. The morphology of the polymer nanostructures has been characterized using scanning electron microscopy and transmission electron microscopy. The different factors have been discussed in the process of experiments.     

Fabrication of diameter-modulated and ultrathin porous nanowires in anodic aluminum oxide templates

Anodic aluminum oxide (AAO) membranes with modulated pore diameter were synthesized by pulse anodization in 0.3 M sulfuric acid at 1 °C. For AAO growth, a typical combination of alternating mild anodizing (MA) and hard anodizing (HA) pulses with applied potential pulses of 25 V and 35 V was applied. The control of the duration of HA pulses will provide an interesting way to tune the shape of pores and the structure of AAO channels. It was found that a non-uniform length of HA segments in cross section of AAO is usually observed when the HA pulse duration is shorter than 1.2 s. The pulse anodization performed with longer HA pulses leads to the formation of AAO templates with periodically modulated pore diameter and nearly uniform length of segments. Various diameter-modulated metallic nanowires (Au, Ag, Ni and Ag–Au) were fabricated by electrodeposition in the pores of anodic alumina membranes. A typical average nanowire diameter was about 30 nm and 48 nm for MA and HA nanowire segments, respectively. After a successful dealloying silver from Ag–Au nanowires, porous ultrathin Au nanowires were obtained.     

纳米阳极氧化铝模板膜孔可控生长规律

采用新的二次阳极氧化工艺,制备了多孔纳米阳极氧化铝(anodized Al2O3,AAO)膜.对铝在草酸溶液中的二次阳极氧化过程进行了研究.利用扫描电镜、原子力显微镜、透射电镜等对其形貌进行了表征和分析.结果表明:用高纯铝所制备的纳米AAO膜孔大小一致,有序性强;膜的孔径随扩孔时间的增加而增大,随草酸浓度的增加而减少.进一步延长扩孔时间至1.5h,其孔径生长规律仍符合AAO膜孔径可控性动力学模型方程,使原模型的扩孔时间范围由1.0h拓展到1.5h.AAO膜的最佳制备工艺为:采用0.3mol/L草酸溶液,电压为40V,在40℃氧化9h和扩孔1 h.在最佳制备工艺条件下,制备的AAO膜厚为112.7 μm,孔径为70nm左右.     

铝基氧化铝表面化学镀铜工艺研究

在铝基板表面的氧化铝上实施化学镀铜,获得剥离强度良好的化学镀铜层.利用扫描电子显微镜观察了化学镀铜层的剖面形貌;测定了硅烷化前后氧化铝表面的润湿性;分析了硅烷化时间和施镀时间对氧化铝表面铜厚度的影响.结果表明:在铝基板表面氧化铝上所制得的化学镀铜层与基体结合力良好,可以满足印制线路板的要求.     

Novel, uniform nanostructured catalytic membranes

Nanostructured membrane structures have been fabricated by a combination of anodic aluminum oxidation (AAO) and atomic layer deposition (ALD) for use as platforms for the synthesis of highly uniform heterogeneous catalysts. The ALD method makes it possible to control pore diameters on the Angstrom scale even when the overall pore diameter is 10’s to 100’s of nanometers. AAO membranes imbedded in an aluminum sealing ring have been tested for flow properties and found to follow Knudsen diffusion behavior. Vanadia-coated membranes have been tested for the catalytic oxidative dehydrogenation of cyclohexane and show improved selectivity at the same conversion compared to conventional powdered alumina supported vanadia catalysts.     

Growth of Alumina/Metal Composites into Porous Ceramics by the Oxidation of Aluminum

Alumina/metal composites were grown into the pores of porous alumina, porous aluminosilicate, and porous silicon carbide substrates through the oxidation of Al–Si (5 wt%) powder compacts coated with magnesia powder (11 mg/ cm²). The thickness of the resulting composite increased with oxidation time and temperature, and was proportional to (pore size)^0.5 on using porous alumina. The composite thickness was more than 2 times larger in the silicon carbide and about 4 times larger in the aluminosilicate than in the alumina at 1523 K for 1 h. The products using these three types of substrates consisted of alumina, aluminum, and silicon, except that a silicon carbide phase occurred when using the silicon carbide substrate. Silica and mullite in the aluminosilicate substrate changed to silicon and alumina, and silica in the silicon carbide substrate changed to silicon because of the reduction by aluminum.     

Y型孔洞阳极氧化铝模板的制备研究

阳极氧化铝(AAO)模板由于制备简单,成本较低,其孔径大小具有可控性等优点,是制备形状均匀、有序纳米电子材料的理想无机模板。直流恒压下,在0.3 M草酸溶液中对铝实施两步阳极氧化,并在第二次阳极氧化中途降低电压为初始电压的1/2获得Y形孔洞的氧化铝模板。利用扫描电子显微镜(SEM)对模板进行表征,结果表明:氧化铝模板高度有序,主干孔径约90 nm,分支孔径为(42±5)nm。     

Porous anodic alumina formed by anodization of aluminum alloy (AA1050) and high purity aluminum

A two-step anodization process performed at 0 °C was used to prepare highly ordered porous anodic alumina on the AA1050 alloy and high purity aluminum foil. The anodizing of both substrates was carried out in 0.3 M sulfuric acid and 0.3 M oxalic acid baths at 25 V and 40 V, respectively. The effect of the extended duration of the second anodizing step on pore order degree and structural features of AAO membranes was studied. The presence of alloying elements affects not only the rate of oxide growth but also the microstructure of the anodic film. It was found that pore circularity and regularity of pore arrangement in AAO membranes formed on the AA1050 alloy were always worse than those observed on the pure Al substrate. The structural features, such as pore diameter, interpore distance, wall thickness, barrier layer thickness, porosity and pore density of porous anodic alumina formed on AA1050 are a little different from those obtained for high purity Al. The extended time of the second anodizing step, up to 16 h does not affect significantly the regularity of pore order and all structural features of AAO membranes, independently of the anodizing electrolyte.