阳极氧化制备二氧化锡纳米孔

单质锡箔片在草酸溶液中利用电化学阳极氧化合成出前聚体, 并将前聚体通过加热氧化制备出具有纳米级孔道的二氧化锡材料. 电化学氧化制备的氧化亚锡纳米孔径和分布随外加电压、电解质溶液浓度和氧化时间而变化. 经场发射扫描电镜(FE-SEM)、X射线衍射(XRD)和孔径分析仪(Poresizer)分析显示, 阳极氧化的前聚体是氧化亚锡, 通过在空气中加热转化为二氧化锡, 在详细研究制备条件和氧化锡孔道形貌的基础上, 提出了氧化锡纳米孔的生成机理符合氧化溶解理论模型.     

长程有序纳米孔氧化铝模板的制备与研究

以硫酸和草酸溶液为电解液,采用二次阳极氧化法制备出高度长程有序的纳米孔氧化铝(AAO)模板,并结合扫描电子显微镜(SEM)对其微观结构及形貌进行了观察和表征.通过研究不同的氧化电压和电解液浓度对AAO模板纳米孔形貌(孔径、孔间距、面密度和长程有序性)的影响,得到了最佳的氧化电压和电解液浓度.     

超低密度CHO泡沫结构与力学性能研究

基于溶胶-凝胶技术,通过不同的干燥方式,制备了3种10 mg/cm~3的CHO泡沫,并对泡沫的显微形貌、孔结构分布以及力学性能进行了测试分析。结果表明,通过超临界干燥技术制备得到的三乙酸纤维素(TAC)泡沫力学性能最佳,其弹性模量为3.50×10~4 Pa,冷冻干燥制得的TAC泡沫弹性模量为3.38×10~4 Pa,冷冻干燥获得的TMPTA(聚三羟甲基丙烷三丙烯酸酯)泡沫力学性能最差,其弹性模量仅为0.36×10~4 Pa。超临界干燥TAC泡沫中的孔径较小(数纳米至十几纳米量级),孔径分布较为均匀。冷冻干燥的TAC泡沫孔径增大(几十纳米量级),孔径分布较宽。冷冻干燥的TMPTA泡沫孔径最大(百纳米量级孔洞大幅增加),孔径分布最宽。     

有序蘑菇状负载型纳米TiO_2光催化剂制备

为了解决TiO2光催化剂分散性差、难回收、难固定等问题,提出一种利用有序纳米结构作为载体的负载型催化剂制备技术,来制备三维纳米TiO2光催化剂.利用SiO2和SiNx材料具有不同刻蚀选择比的特点,首先将SiO2纳米球(直径60～90 nm)作为掩模刻蚀衬底上的SiNx薄膜.然后将刻蚀形成的结构作为载体,利用磁控溅射技术在其上制备TiO2薄膜.实验结果表明,样品经刻蚀后形成由SiNx纳米柱和SiO2纳米扁球组成的三维纳米载体,所制备的TiO2分散地负载在该纳米载体上,形成一种由TiO2、SiO2和SiNx构成的蘑菇状三维纳米复合体系.这种通过纳米球刻蚀结合镀膜的方法是制备纳米载体及三维纳米负载型催化剂的技术之一,利用该技术制备的负载型催化剂分散性好、易于回收和重复利用.     

纳米阵列阳极氧化铝模板的制备及其形成机理

多孔阵列阳极氧化铝模板为合成大面积的准一维纳米丝和纳米管微阵列提供了一种有效的载体.采用二次氧化法,制备了孔径在30～40 nm之间的纳米阵列氧化铝模板,分析了纳米阵列阳极氧化铝模板形成的热力学原理、动力学原理及孔的形成机理.采用扫描电子显微镜(SEM)对其形貌进行了表征,通过扩孔试验得到了孔径与扩孔时间的关系.用XRD衍射仪对纳米薄膜的成分和形态进行了分析,证明了制备的氧化膜是非晶态的.     

石墨的微加工工艺研究

石墨具有固态超滑和耐酸、耐碱和耐有机溶剂腐蚀等特性,使其有望成为微机电系统(MEMS)基础材料的一种选择。如能通过微纳米加工工艺对石墨进行微加工并在石墨上大批量、稳定、可控地制备各种掩模图案和石墨微结构,一定程度上可以推动石墨成为MEMS基础材料。故本文通过工艺设计和参数摸索,利用薄膜沉积、光刻、刻蚀等常用的微纳米加工工艺对石墨进行微加工研究,并对加工后的石墨进行表征。结果表明,利用薄膜沉积技术在石墨表面沉积的薄膜可以满足后续光刻和刻蚀等工艺的要求。同时,采用光刻技术能在石墨表面大批量、稳定、可控地加工出不同形状,不同尺寸的光刻胶掩模图案。此外,利用刻蚀技术可以在石墨上大批量、稳定、可控地加工出形状较规则,排列整齐且垂直度较高的石墨微结构。     

阳极TiO_2薄膜两步施加电压法制备参数对其形貌的影响

Ti的硫酸阳极氧化中硫酸的腐蚀性不足以溶解TiO2阻挡层,采用高温、高电压又会使膜纳米孔的孔径大于200 nm,使其应用范围受到限制.采用两步施加电压的方法,对钛阳极进行阳极氧化处理,以期在不同的工艺条件下制备具有不同孔径和孔密度的氧化钛薄膜.使用扫描电子显微镜考察了初始电压、终态电压、电解液温度、氧化时间等工艺参数对阳极氧化钛薄膜形貌的影响.结果表明,初始电压对氧化钛薄膜形貌的影响是通过改变电解液/阻挡层之间的界面条件来实现的;随着阳极氧化时间的延长纳米孔的孔径减小,孔密度增大;提高电解液的温度不影响纳米孔的形成过程,但对氧化钛薄膜的生长过程产生了比较大的影响.     

阳极氧化工艺制备氧化铝模板

多孔氧化铝模板是一种用于制作纳米结构材料的模板.为了制作出理想的模板,采用不同的阳极氧化工艺制备多孔氧化铝模板,通过改变工艺参数研究了模板孔径的变化规律,结果表明,在适宜条件下,纳米级氧化铝模板具有六方紧密堆积柱状结构,在每个六棱柱的中心有一个与膜表面垂直的圆柱孔.在一定范围内,随着氧化电压、电流密度、反应温度、铝片纯度的增加氧化铝模板的孔径也随之增加.     

不同基底对退火制备Ni纳米岛掩模形貌的影响

目前,刻蚀自组装在GaN薄膜上Ni纳米岛的掩模的方法是制备GaN纳米柱阵列常用手段。但是,这将对后续制备出的纳米柱产生Ni污染。除此之外,直接将GaN系的材料暴露在高温下进行Ni纳米岛掩模的制备,会对GaN材料表面产生一定的热腐蚀损伤。因此,以GaN、SiO_2、Al_2O_3和SixNy分别为基底,对退火自组装在这4种基底上的Ni纳米岛形貌进行了较为系统的研究。发现850℃的退火温度下,Al_2O_3基底上Ni薄膜形成的纳米岛的形貌最为规整,为最优化衬底。     

用低纯度铝制备AAO模板及其结构研究

在0.3mol/dm3草酸溶液中,通过不同纯度铝的恒电位二次阳极氧化制备了纳米孔氧化铝模板,并用场发射扫描电子显微镜(FE-SEM)和原子力显微镜(AFM)观察模板结构.实验结果表明,一次氧化除膜后低纯度铝基体表面呈现较为规则的六边形结构,这种蜂巢结构有利于二次氧化过程中获得有序度更高的纳米孔模板.低纯度铝制备的模板表面被晶界分隔为微小的区域,只是在较窄区域内才出现六边形规则排列的纳米孔.恒电位40V时所得模板经扩孔处理后,孔径由35nm增大到100nm左右,且孔径大小几乎一致.从纳米孔的有序度来看,由低纯度铝制备模板还需要进一步优化阳极氧化参数.     

Mounted nanoporous anodic alumina thin films as planar optical waveguides

Solid-supported thin films of self-organized nanoporous anodic aluminum oxide (AAO) have been widely employed for the template preparation of nanostructured functional materials. Recently, the use of nanoporous AAO thin films in optical waveguide spectroscopy (OWS) has been explored for high sensitivity, in situ monitoring of processes occurring within these nanoporous templates. In this contribution, we demonstrate a strategy for mounting bulk anodized AAO thin films on heterogeneous solid-supports suitable for waveguide sensing experiments. Unlike conventional preparations of AAO thin films by anodization of vacuum- or electrochemically deposited Al thin films, the full range of techniques available to anodize bulk Al may potentially be applied with the present method. Moreover, we show that AAO thin films mounted on glass substrates can have superior waveguide coupling properties compared to conventionally prepared samples. The nanostructure of the AAO can be well characterized by an EMT-OWS analysis, demonstrated by comparing scanning electron microscopy images of the AAO and the pore dimensions calculated from an effective medium theory (EMT) analysis of the film refractive index measured by OWS. Finally, using a curved metallic substrate as an example, we show that our mounting technique can be used as a general strategy to functionalize objects with nanoporous AAO films.     

Fabrication of highly ordered anodic aluminium oxide templates on silicon substrates

The controlled fabrication of highly ordered anodic aluminium oxide (AAO) templates of unprecedented pore uniformity directly on Si, enabled by new advances on two fronts - direct and timed anodisation of a high-purity Al film of unprecedented thickness (50 mum) on Si, and anodising a thin but pre-textured Al film on Si, has been reported. To deposit high-quality and ultra-thick Al on a non-compliant substrate, a prerequisite for obtaining highly ordered pore arrays on Si by self-organisation while retaining a good adhesion, a specially designed process of e-beam evaporation followed by in situ annealing has been deployed. To obtain an AAO template with the same high degree of ordering and uniformity but from a thin Al film, which is not achievable by the self-organisation alone, pre-patterning of the thin Al surface by reactive ion etching using a freestanding AAO mask that was formed in a separate process was performed. The resultant AAO/Si template provides a good platform for integrated growth of nanotube, nanowire or nanodot arrays on Si. Template-assisted growth of carbon nanotubes (CNTs) directly on Si was demonstrated via a chemical vapour deposition method. By controllably removing the AAO barrier layer at the bottom of the pores and partially etching back the AAO top surface, new CNT/Si structures were obtained with potential applications in field emitters, sensors, oscillators and photodetectors.     

Surface and interface characterization of nanoporous alumina templates produced in oxalic acid and submitted to etching procedures

High purity aluminum (Al) sheets were used to produce ordered nanoporous alumina templates by two step anodization technique using oxalic acid as electrolyte. Electrochemical polishing of Al sheets was performed in order to study the surface roughness influence on the pore roundness of the alumina templates. The templates were submitted to progressive reduction of anodizing voltage (electrochemical etching) to thin the Al₂O₃ barrier layer on the bottom of the pores, and to chemical etching to widen the diameter of the pores. The pore diameter and porosity increase linearly with the chemical etching time, while interpore distance, circularity, pore density and pore distribution do not change. Electropolished Al substrates produce nanoporous Al₂O₃ templates with more circular pores, and the Al₂O₃ barrier layer at the Al₂O₃/Al interfaces is completely removed after the electrochemical and chemical etching processes.     

The fabrication of tunable nanoporous oxide surfaces by block copolymer lithography and atomic layer deposition

Patterned nanoscale materials with controllable characteristic feature sizes and periodicity are of considerable interest in a wide range of fields, with various possible applications ranging from biomedical to nanoelectronic devices. Block-copolymer (BC)-based lithography is a powerful tool for the fabrication of uniform, densely spaced nanometer-scale features over large areas. Following this bottom-up approach, nanoporous polymeric films can be deposited on any type of substrate. The nanoporous periodic template can be transferred to the underlying substrate by dry anisotropic etching. Nevertheless the physical sizes of the polymeric mask represent an important limitation in the implementation of suitable lithographic protocols based on BC technology, since the diameter and the center-to-center distance of the pores cannot be varied independently in this class of materials. This problem could be overcome by combining block copolymer technology with atomic layer deposition (ALD): by means of BC-based lithography a nanoporous SiO2 template, with well-reproducible characteristic dimensions, can be fabricated and subsequently used as a backbone for the growth of perfectly conformal thin oxide films by ALD. In this work polystyrene-b-poly(methylmethacrylate) (PS-b-PMMA) BC and reactive ion etching are used to fabricate hexagonally packed 23 nm wide nanopores in a 50 nm thick SiO2 matrix. By ALD deposition of Al2O3 thin films onto the nanoporous SiO2 templates, nanostructured Al2O3 surfaces are obtained. By properly adjusting the thickness of the Al2O3 film the dimension of the pores in the oxide films is progressively reduced, with nanometer precision, from the original size down to complete filling of the pores, thus providing a simple and fast strategy for the fabrication of nanoporous Al2O3 surfaces with well-controllable feature size.     

Structural and optical properties of ZnO films grown on the AAO templates

Structural and optical properties of ZnO films grown on Al substrate and anodic alumina oxide (AAO) templates by rf magnetron reactive sputtering deposition were investigated using X-ray diffraction (XRD), atomic-force microscope (AFM) and photoluminescence (PL). We found that ZnO thin films on Al substrate show good C-axis orientation, while the orientation of ZnO film on AAO templates is disordered, this due to the fact that the crystalline of ZnO is greatly influenced by surface morphology of substrates. PL measurements show a blue band in the wavelength range of 400–500 nm caused by the interstitial Zn in the ZnO films. The intensity of emission peak of ZnO films deposited on AAO templates increases compared with that on the Al substrate. Combining electrical resistivity and carrier concentration measurements, we found that that the blue emission intensity is consistent with the concentration for the interstitial zinc in the ZnO films.     

Synthesis of dense, single-crystalline CrO2 nanowire arrays using AAO template-assisted chemical vapor deposition

High-density, vertically aligned CrO(2) nanowire arrays were obtained via atmospheric-pressure CVD assisted by AAO templates. The CrO(2) nanowire arrays show remarkably enhanced coercivity compared with CrO(2) films or bulk. It was found that the length of the nanowires is greatly influenced by the pore diameter of the AAO template used. The growth mechanism and the pore size dependence of the CrO(2) nanowire arrays are discussed. The present method provides a useful approach for the synthesis of CrO(2) nanowire arrays. Such highly ordered nanowire arrays within an AAO template may have important applications in ultrahigh-density perpendicular magnetic recording devices and the mass production of spintronic nanodevices.     

Nondestructive replication of self-ordered nanoporous alumina membranes via cross-linked polyacrylate nanofiber arrays

Ordered nanofiber arrays are a promising material platform for artificial adhesive structures, tissue engineering, wound dressing, sensor arrays, and self-cleaning surfaces. Their production via self-ordered porous alumina hard templates serving as shape-defining molds is well-established. However, their release requires the destruction of the hard templates, the fabrication of which is costly and time-consuming, by wet-chemical etching steps with acids or bases. We report the nondestructive mechanical extraction of arrays of cross-linked polyacrylate nanofibers from thus recyclable self-ordered nanoporous alumina hard templates. Silica replicas of the latter were synthesized using the extricated nanofiber arrays as secondary molds that could be mechanically detached from the molded material. The approach reported here, which can be combined with microstructuring, may pave the way for the high-throughput production of both functional nanofiber arrays and ordered nanoporous membranes consisting of a broad range of material systems.     

The nanoporous structure of anodic aluminum oxide fabricated on the Au/Nb/Si substrate

We have studied the anodization behavior of an Al film evaporated on the Au/Nb/Si substrate and demonstrated an effective approach to fabricate the through-hole anodic aluminum oxide (AAO) template on the conducting substrate. The smoothness of the initial metal films and an appropriate wet etching of the oxide film anodized in the first step were found to be critical factors for successfully anodizing the Al film on Au surface. The barrier layer of the obtained AAO structure presented a convex and thinner characteristic, and the underlying Au surface became porous after the anodization. This phenomenon was similar to the case of anodizing the Al film on an ITO glass substrate and could be explained reasonably by the effect of high pressure O₂ gas impelling and H⁺ etching at the interface of the barrier oxide and the Au layer.     

Formation of Pt nanorods on nanoporous anodic aluminum oxides by controlled nucleation sites

Vertical-aligned Pt nanorods are fabricated on the surface of nanoporous anodic aluminum oxide (AAO) templates by magnetron sputtering. The size effect of AAO templates, which is focused on in this study, would influence the morphology of stacked atoms. The rim of the pores, which act as obstacles to the stacked atoms, could prevent them from forming continuous films. The continuous films are commonly formed because of the larger interpore distance which is compared to the grain size of stacked atoms. Between closely-distributed pores, the shorter interpore distance, namely smaller surface area, indicates insufficient surface energy for heterogeneous nucleation, restricts the growth of stacked atoms. Nevertheless, there still remain regions with larger interpore distance. On these constricted regions, instead of continuous films, isolated nanorods are formed. In this study, a nanorod growth diagram is deduced, and understanding of the growth of nanorods on AAO templates is furthered.     

Nanostructuring polymeric materials by templating strategies

This contribution summarizes efforts in designing, assembling/synthesizing, and structurally and functionally characterizing nanostructured materials using anodized aluminum oxide (AAO) as a thin-film template. Optical waveguide spectroscopy, using a nanoporous template as the guiding structure, is a particularly powerful analytical tool. The layer-by-layer approach for the fabrication of multilayer assemblies is shown to allow the fabrication of nanotube arrays. In addition to using dendrimers as building blocks, semiconducting nanomaterial (e.g., quantum dot) hybrid architectures with very interesting photophysical properties can be assembled. These can be employed, for example, in biosensing applications. Other strategies for using the AAO layers as templates include the growth of polymeric nanorod arrays from different functional monomers, which, after the dissolution of the template, are still able to guide light. This opens up novel concepts for integrated optics platforms with nanostructured materials.