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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. 相似文献
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This article reports on the comparative study of the fabrication of porous anodic alumina films by anodisation of the aluminium films on glass substrates which were deposited by direct current sputtering and electron beam evaporation methods. The relationship between surface morphology of the deposited aluminum films and porous anodic alumina films was investigated. A more uniform and ordered porous anodic alumina was obtained by fabricating from electron beam evaporation deposited aluminium film with smaller and compact grains. Two-step anodisation was used to further improve the quality of porous anodic alumina compared to one-step anodisation. The optical transmittance spectra within wavelength of 370–800 nm were obtained and the optical properties were studied. 相似文献
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The pore height and diameter of the nanoscale structure of porous anodic alumina (PAA) film produced by the anodization technique are controllable. The structures can be applied for the fabrication of visible spectral range optical devices. In this study we characterized the luminescence properties of self-ordered PAA films evaporated onto silicon substrates. Anomalous luminescence properties produced by carrier confinement were observed in PAA films fabricated with the introduction of oxalic acid electrolytes during the anodization process. The recombination mechanisms were characterized by measuring the temperature-dependent photoluminescence (PL) spectra. The PL spectra of PAA films show an asymmetrical luminescence profile in the blue emission region. The Gaussian function divides these into two subbands. The subbands originate from two different kinds of oxygen-deficient defect centers, namely, F+ (oxygen vacancy with only one electron) and F (oxygen vacancy with two electrons) centers. The F centers are densest at the surface but show a gradual decrease with an increase in the pore wall depth and electrolyte concentration. However, the reverse trend is observed for the F+ centers. In strong contrast to the commonly expected trend of a uniform reduction in non-radiative recombination with decreasing lattice temperature, we observed an anomalous low-temperature PL growth and decline between the F and F+ centers. Theoretical models corroborate the anomalous temperature behavior. All the calculations are in agreement with the experimental observations. 相似文献
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Dongdong Li Chuanhai Jiang Jianhua Jiang Xin Ren 《Materials Chemistry and Physics》2008,111(1):168-171
A simple and cost effective method for fabricating long-range ordered porous anodic alumina (PAA) membranes is presented, which explores a self-ordering regime with controllable interpore distances over a large scale (300–360 nm). The cohesive force at the hemi-spherical scallop/cell wall (HS/CW) interface is weaker than the other locations. When the PAA membranes were immersed in H3PO4 solution, regular cheese-like hexagonal patterns have been propagated at the cell boundaries. With increased etching time, numerous pores were observed at triple points where three cells met. The distinct fracture and etching behaviors in PAA can be ascribed to the intense ionic transport accompanied by the volume expansion in the barrier region under high electric field. 相似文献
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A simple method to tune the magnetic and optical properties of porous anodic alumina (PAA) films embedded with Co nanowires is reported. The PAA/Co composite films with gradually changing microstructures displayed highly saturated rainbow rings of structural colours and gradual magnetism after being synthesized following a one-step AC electrodeposition method. The magnetization and optical properties of the films can be effectively tuned by varying the deposition voltage, time and controlling the distance between electrodes. A theoretical study on the electrodeposition mechanism that requires gradually changing the length of Co nanowires is consistent with the reported experimental results. 相似文献
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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. 相似文献
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高度有序多孔阳极氧化铝模板的制备 总被引:1,自引:0,他引:1
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. 相似文献
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多孔阳极氧化铝模板的制备及其光学特性研究 总被引:2,自引:0,他引:2
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。 相似文献
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采用球形和非球形Al2 O3粉料 ,探讨挤出成型中粉料颗粒形貌对多孔支撑体的性能的影响 .用压汞仪、扫描电子显微镜 (SEM )等手段分析了 1450和 150 0℃下 4h烧成的试样 .结果表明 ,规则球形Al2 O3粉料可以按球形密堆积的形式形成支撑体 ,使气孔率变小 ,不利于制备高气孔率的支撑体 ,并且球形Al2 O3粉料颗粒自身的多孔性使制得的试样出现孔径的双峰分布 ,要在较高烧成温度下可以消除 ,但该双峰分布结构对透气度没有影响 ;球形颗粒间的接触面积减少 ,不利于烧结和支撑体强度 ,但是 ,球形粉料形成的孔的形状规则 ,易于使支撑体整体均匀化 相似文献
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采用二步阳极氧化法制备了多孔阳极氧化铝(PAA)薄膜,借助于扫描电子显微镜(SEM)分析了多孔阳极氧化铝薄膜的微观形貌,发现在其表面孔径为70~90 nm的六边形孔洞分布均匀,且垂直于表面平行生长.依据PAA反射光谱的实验数据,利用Kramers-Kronig关系计算出PAA薄膜的复折射率、复介电常数以及光学能隙等光学常数.通过分析吸收系数与入射光子能量之间的关系,表明PAA具有直接带隙(能隙约为3.4eV)半导体的光学性质. 相似文献
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C.H. Voon M.N. Derman U. Hashim K.R. Ahmad L.N. Ho 《Journal of Experimental Nanoscience》2014,9(2):106-112
Porous anodic alumina (PAA) has been produced on aluminium substrate by single-step anodising at 50?V in 0.3?M oxalic acid at 15°C for 60?min. The highly ordered pore and cell structure was achieved by subjecting the PAA to oxide dissolution treatment in a mixture of chromic and phosphoric acids. The nanostructure prior and post-oxide dissolution treatment was examined under scanning electron microscope. It was found that the oxide dissolution treatment improves the regularity of the cell and pore structure significantly. Uniform closely packed honeycomb structure of PAA is obtained. The uniformities of pore diameter and interpore distance are also enhanced. Compared to the PAA prior treatment, it was noticed that the pore diameter of the post-treatment PAA increases. 相似文献
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The synthesis of nanoporous membranes based on different concepts and materials is a field of active research. This review focuses on the synthesis strategies, mesophase evolution mechanisms and potential applications of mesoporous materials confined within anodic alumina membranes (AAM). Following a rapid evolution of synthetic techniques, a significant number of different mesoporous materials (e.g., silica, titania, and carbon) with highly regular structures can now be prepared within these membranes. In recent years, efforts have also been made to understand the formation mechanisms of these hierarchical mesophases. The resulting organized nanoporous membranes open up a wide range of potential applications in fields such as templating oriented nanowires and controlled separation and release of molecules. For example, while various synthesis strategies can be used for the preparation of membrane-embedded nanowires, the latter can also be obtained as isolated objects after dissolution of the alumina host matrix. The review also discusses issues such as control of structural defects or integrity of interfaces that should be addressed in future research in order to fully exploit the potential of these hierarchical mesoporous channel structures. 相似文献
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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. 相似文献
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E. LefeuvreK.H. Kim Z.B. HeJ.-L. Maurice M. ChâteletD. Pribat C.S. Cojocaru 《Thin solid films》2011,519(14):4603-4608
A Hot Wire assisted Chemical Vapor Deposition (HWCVD) process has been developed for producing high-density arrays of parallel, straight and organized silicon nanowires (SiNWs) inside vertical Porous Anodic Alumina (PAA) templates, exploring temperatures ranging from 430 °C to 600 °C, and pressures varying between 2.5 and 7.5 mbar. In order to prevent parasitic amorphous silicon (a-Si) deposit and to promote the crystalline SiNWs growth, we used a tungsten hot wire to partially crack H2 into atomic hydrogen, which acts like a selective etchant regarding a-Si. Here we describe the optimization route we followed to limit the deposit of a-Si onto the surface of the porous membrane and on the walls of the pores, which led to the possibility to grow SiNWs inside the PAA membranes. Such an approach has high potentialities for device realization, like PIN junctions, FETs or electrodes for Li-ion batteries. 相似文献
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Porous anodic oxide films on aluminium formed in phosphoric acid (PAA) have been characterized nondestructively by spectroscopic ellipsometry. Compared to previous studies on porous films formed in sulfuric acid, the optical behaviour of PAA films reveals new features which have been attributed to film-substrate interface roughness and optical anisotropy effects. On one hand relatively large interface roughness has been simulated by a graded index model. On the other hand, the implementation of uniaxial anisotropy in the optical model of the PAA film enables to interpret spectroscopic ellipsometry data acquired at multiple angles of incidence in terms of the morphology of the films. More specifically, accurate and physically realistic values are found for the porosity and porous film thickness. Although more difficult to interpret from the optical findings, the thickness of the barrier part of the porous film can also be estimated. The ellipsometry characterizations are confirmed by complementary TEM analysis of various films. Finally, the anisotropy exhibited by the PAA films is in line with recent theoretical predictions of the optical behaviour of arrays of parallel cylindrical capillaries in an isotropic medium proposed by other authors. 相似文献