多孔阳极氧化铝模板的制备

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。介绍了多孔阳极氧化铝膜的形成机理、结构类型和在草酸溶液中制备多孔氧化铝模板的工艺。在本实验中,使用高纯铝片(99.99%)和0.3 mol/L浓度的草酸,利用电化学二次阳极氧化法制备出多孔阳极氧化铝模板,用SEM对其形貌进行了观测,得到的模板孔径在50～70 nm,孔间距约为100 nm。     

基于自适应小波阈值的SAR图像降噪

合成孔径雷达(SAR)图像固有的相干斑噪声严重降低了图像质量,影响了后续的处理.SAR图像降噪的要求,是在滤除噪声的同时, 尽量保持原始图像的边缘和纹理等细节信息.本文将经典的小波域空间自适应软阈值法应用于降低SAR图像斑点噪声.在此基础上,本文提出根据小波系数的局部统计量选取阈值以及估计相关参数的方法.实验结果表明,本文算法在降低噪声和保持边缘纹理细节之间取得了较好的平衡,处理后的SAR图像的视觉效果和质量评估参数都要优于传统的空间域滤波方法的处理结果.     

电化学制备亚微米氧化铝有序多孔膜方法研究

采用电化学阳极氧化法制备亚微米氧化铝有序多孔膜 ,研究了铝电极预处理过程、扩孔时间、阳极氧化时间和阳极氧化电压对亚微米氧化铝有序多孔膜孔径、孔密度以及孔排列有序性的影响规律 ,并且建立了一个理想模型来探讨亚微米氧化铝多孔膜的生长过程     

电化学制备亚微米氧化铝有序多孔膜方法研究

采用电化学阳极氧化法制备亚微米氧化铝有序多孔膜,研究了铝电极预处理过程、扩孔时间、阳极氧化时间和阳极氧化电压对亚微米氧化铝有序多孔膜孔径、孔密度以及孔排列有序性的影响规律,并且建立了一个理想模型来探讨亚微米氧化铝多孔膜的生长过程.     

基于指导滤波的内侧指横纹识别方法

为了使指导滤波可以更有效地去除噪声进而提高匹配效率,提出了一种基于指导滤波的内侧指横纹识别方法。首先,在ROI提取阶段,通过提取ROI模板和利用模板在原始图像上所处位置的先验知识来指导其他原始图像进行准确的ROI提取,并对得到的ROI和模板进行互相指导滤波去除噪声。其次,在线特征提取阶段,利用Gabor滤波与求偏导相结合的方法进行线特征提取。最后,在特征匹配阶段,利用快速傅里叶变换的方法,得到相似度后通过对其选取合适的阈值来得到较好的实验效果。评估系统建立在包含100个人的2 000幅右手手部图像的数据库上,等错误率为2.32%,证明该算法可以进行指横纹特征识别并具有较高的准确率。     

电化学制备亚微米氧化铝有序多孔膜方法研究

采用电化学阳极氧化法制备亚微米氧化铝有序多孔膜，研究了铝电极预处理过程、扩孔时间、阳极氧化时间和阳极氧化电压对亚微米氧化铝有序多孔膜孔径、孔密度以及孔排列有序性的影响规律，并且建立了一个理想模型来探讨亚微米氧化铝多孔膜的生长过程。     

基于CMOS图像传感器混合噪声的自适应滤波算法

针对中值滤波导致部分图像细节损失和均值滤波出现模糊现象,设计了一种适用于椒盐和高斯混合噪声的自适应滤波算法.该算法先用最小邻域的均值和阈值判断噪声类型,然后使用加权中值滤波处理椒盐噪声,再利用拉普拉斯算子和相应阈值判断图像边缘细节,最后对高斯噪声进行加权均值滤波.实验仿真结果表明,从图像视觉效果来看,相比单独使用中值和均值滤波降噪,自适应滤波算法对图像的还原效果更好,图像细节保存较好,模糊程度相对较弱,图像更清晰.通过对比峰值信噪比(PSNR)和均方误差(MSE),对混合噪声进行处理时,滤波算法的PSNR和MSE值优于中值和均值滤波,有效还原了噪声图像.整个算法是在最小邻域空间进行,易于实现,对混合噪声的处理效果较好,为图像处理的系统集成化设计提供了技术支持.     

氧化铝、氧化钛多孔膜的阳极氧化制备与微结构比较

采用阳极氧化法分别获得了纳米结构的氧化铝多孔膜和氧化钛多孔膜。对多孔膜的微结构、形貌、晶相等进行了检测与分析;系统研究了阳极氧化电压对纳米孔孔径的影响,分析了金属箔片退火、两步阳极氧化对纳米孔有序度和孔径均匀性的影响;对阳极氧化过程中出现的新颖的上下双层和内外双层多孔膜形貌进行了分析和讨论。初步获得了纳米多孔膜的形成机理,阳极氧化铝、氧化钛纳米多孔膜在制备、微结构等方面存在许多共同点。     

阳极氧化铝膜的偏振光谱特性研究

为了测试阳极氧化铝膜的偏振光谱特性,在硫酸溶液中,采用二次阳极氧化的方法获得了孔洞分布均匀、有序的纳米多孔阳极氧化铝膜,对其形貌和结构、透射和偏振光谱特性进行了理论分析和实验验证。研究结果表明,在温度较低和阳极氧化电流密度比较大的条件下制备阳极氧化铝,铝未被完全氧化,孔与孔之间含有剩余的铝柱,这些铝柱构成各向异性纳米金属列阵。X射线衍射图谱显示,多孔阳极氧化铝膜具有氧化铝的非晶态结构;透射光谱和偏振光谱显示,在可见光及近红外光区多孔阳极氧化铝具有很好的透射比和一定的偏光特性。研究结果对含金属纳米线的多孔铝复合结构的偏振器件的制作具有参考价值。     

改进小波阈值在红外热波无损检测中的应用

近二十年来红外热波无损检测技术迅速发展,并在较多领域都得到了普遍应用,但碍于其易受环境影响和工作元件不均匀的特殊性,非制冷红外热像仪原始热波图总存在一定程度的噪声污染,因此对原始热波图进行去噪处理是该技术的关键步骤。传统的改进小波阈值去噪方法局限于对阈值进行自适应分解尺度的改造,使阈值函数平滑连续保真。在噪声方差估计方面没有针对性的方法,而噪声的方差估计是阈值的关键变量,这决定了小波阈值去噪的效果。本文将根据红外图像噪声特性建立混合噪声模型,在噪声模型的基础上进行噪声方差估计、改进阈值及阈值函数,通过软件获取最佳函数参数,最后对仿真模拟结果进行分析,对真实图像进行处理评价,结果表明经改进后的小波阈值去噪方法相对于传统阈值去噪方法和部分滤波去噪方法具有更好的去噪效果。     

Sol-Gel法制备ZnO纳米点阵结构

以Al2O3膜为模板,通过溶胶-凝胶浸渍法,经过干燥、高温加热制备了ZnO纳米点阵结构.SEM结果表明,AAO模板孔遭呈六角形排布,孔道垂直无交叉,孔径为50mm左右,在AAO模板内装入的ZnO为纳米颗粒.XRD结果表明,AAO模板为非晶结构,孔内ZnO具有多晶纤锌矿结构.PL谱结果表明,ZnO/AAO组装体系表现出了很强的紫外发射.     

Functionally Modified Macroporous Membrane Prepared by using Pulsed Laser Deposition

Pulsed laser deposition (PLD) is used to deposit pure metals (Pt and Au) and a mixture of metals (Pt–Ru) at the surface of a porous aluminum anodic oxide (AAO) substrate. In the case of Pt, thick films (> 300 nm) with pore diameters larger than 150 nm (macroporous), replicating the pore structure of the underlying AAO substrate, are obtained when PLD is performed at high (> 50 eV at^–1) kinetic energy (E_k) conditions. At lower E_k conditions, the characteristic structure of the AAO membrane is not discernable in the deposited film. In that case, the substrate is entirely covered by a film, the structure of which is not different from that of a Pt film deposited on a flat Si substrate under the same conditions. AAO membranes modified by macroporous Au and Pt–Ru alloy films are also prepared, demonstrating that the concept can be applied to a wide range of materials. The mechanisms responsible for the replication of the substrate pore structure in the metallic layer are discussed. These functionally modified macroporous membranes are electroactive and this aspect has been emphasized by studying the electrocatalytic properties of Pt and Pt–Ru modified macroporous membranes for CO oxidation.     

Aperture-Adjustable and Repairable Metal-Based MOFs Catalysis Membrane for Water Purification

Precise adjustment of the pore size, damage repair, and efficient cleaning is all challenges for the wider application of inorganic membranes. This study reports a simple strategy of combining dry-wet spinning and electrosynthesis to fabricate stainless-steel metal–organic framework composite membranes characterized by customizable pore sizes, targeted reparability, and high catalytic activity for membrane cleaning. The membrane pore size can be precisely customized in the range of 14–212 nm at nanoscale, and damaged membranes can be repaired by targeted treatment in 120 s. In addition, advanced oxidation processes can be used to quickly clean the membrane and achieve 98% flux recovery. The synergistic actions of the membrane matrix and the selective layer increase the adsorption energy of active sites to oxidant, shorten the electron transfer cycle, and enhance the overall catalytic performance. This study can provide a new direction for the development of advanced membranes for water purification and high-efficiency membrane cleaning methods.     

Effect of electric field polarization and temperature on the effective permittivity and conductivity of porous anodic aluminium oxide membranes

Porous insulators offer new opportunities for the controlled guest-host synthesis of nanowires for future integrated circuits characterized by low propagation delay, crosstalk and power consumption. We propose a method to estimate the effect of the electric field polarization and temperature on the electrical properties of different types of synthesized porous anodic aluminium oxide membranes. It results that the effective permittivity along the pore axis is generally 20% higher than the one in the orthogonal direction. The type of solution and the voltage level applied during anodization are the main parameters affecting the AAO templates characteristics, i.e. their porosity and chemical content. The values of permittivity of the final material, are typically in the range 2.6-3.2 for large pore diameter membranes including phosphorus element and having a low water content, and in the range 3.5-4 for the ones with smaller pores, and showing sulphur element incorporation. Moreover, the dc conductivity of the different membranes appears to be correlated to the pore density.     

阳极氧化铝(AAO)模板法制作的直径和长度一致的碳纳米管

我们在铝衬底上制作了不同参数条件下的阳极氧化铝(AAO)模板.通过改变初次阳极化时间来得到不同尺寸的纳米孔.改变初次阳极化时间可容易地调节,而使用刻蚀技术又可以控制氧化铝孔的长度.在该研究中,控制阳极极化和刻蚀参量成功地制备了不同直径和不同长度的AAO纳米孔.在AAO模板的竖直沟道中生长了方向性强的碳纳米管,而AAO纳米孔的直径和长度可以控制这一过程.通过二次阳极极化法制备了有着六边形孔洞排列方式的纳米AAO模板.由于AAO纳米孔的直径和长度依赖于阳极化参量,故通过控制阳极化参量就可控制AAO纳米孔的直径和长度.     

Recent Advances in Stimuli-Responsive Smart Membranes for Nanofiltration

Nanofiltration membrane plays an increasingly important role in many industrial applications, such as water treatment and resource recovery. The performance of the smart nanofiltration membrane is largely controlled by pore size, the Donnan effect, and surface wettability, which are determined by the function of stimuli-responsive components. Smart membranes, which contain stimuli-responsive components, are capable of changing their physical and chemical properties in response to changes in the environment so that the microstructure of the membrane will have more efficient performances and broader application prospects than the current traditional nanofiltration membranes. Herein, the preparation methods of stimuli-responsive membranes are described and they are systematically classified accordingly to their mechanisms. Moreover, the latest progress of stimuli-responsive membranes in nanofiltration and the main mechanism of each stimuli-response type through relevant examples are discussed and summarized. Finally, this review provides new insights into the remaining challenges and future directions of stimuli-responsive membranes. Fueled by advances in chemistry and materials science, it is expected to build a smart and efficient nanofiltration membrane platform for the benefit of mankind.     

Ordered InAs nanodots formed on the patterned GaAs substrate by molecular beam epitaxy

Ordered indium arsenide (InAs) nanodots are formed by molecular beam epitaxy (MBE) on patterned gallium arsenide (GaAs) substrates, which are prepared by implanting manganese (Mn) ions through anodic aluminum oxide (AAO) membranes into the GaAs wafers. Morphology and structure of the patterned GaAs substrate is determined both by the oxygen desorption and the Mn ion diffusion. Suitable patterned GaAs substrates with the same dosage of Mn ions for the following epitaxy can be obtained by controlling the deoxidization As₄ pressures during the oxygen desorption. Images of samples with different Mn ion implantation dosages and different molecular beam epitaxial conditions for the following deposition of InAs nanodots on the patterned GaAs substrates are characterized by atomic force microscopy (AFM). The order of the InAs nanodots is determined both by the AAO membrane and dosage of Mn ions. The density of InAs nanodots has great relation to the pore density of the AAO.     

直流电沉积法制备铁纳米线阵列及表征

为了制备结构规整的Fe纳米线阵列,以多孔阳极氧化铝(AAO)为模板,采用直流电沉积法制备了Fe纳米线阵列,并利用SEM、TEM、XRD等测试手段对其微观形貌和结构进行了表征。结果表明:所得的Fe纳米线阵列结构规整、直径与模板孔径基本一致,约为250nm,是结构紧密的多晶体。     

煅烧温度和恒温时间对ZnO/AAO/Si组装体系的影响

以AAO/Si为模板,采用化学气相沉积(CVD)的方法在不同温度下,通过煅烧Zn粉和C粉的混合物制备ZnO/AAO/Si组装体系,并对其结构和性质进行了研究。扫描电镜(SEM)结果表明:随着煅烧温度的升高,AAO表面的孔洞逐渐被封堵,当温度达到900℃时,在AAO的表面出现了一层ZnO薄膜。X射线衍射(XRD)结果显示,700℃时在XRD图谱上观看到六角纤锌矿的ZnO的衍射峰,并且随着温度的升高,ZnO的衍射峰逐渐增强,当温度升至800和900℃时出现了ZnAl2O4的衍射峰。因此,化学气相沉积制备组装体系时的最适温为700℃。在700℃时煅烧不同恒温时间制备的ZnO/AAO/Si组装体系SEM图显示,随着恒温时间的延长,孔的封闭效应逐渐明显。     

基于阳极氧化铝模板的金属纳米孔阵列膜制备

以0.3 mol/L草酸为电解液,在40 V直流电压、0～5℃下采用二步阳极氧化法制备了纳米多孔阳极氧化铝模板。用射频磁控溅射法在阳极氧化铝模板表面制备了金属铝膜。SEM分析结果表明:金属膜复制了阳极氧化铝模板形貌,具有纳米孔有序阵列结构;金属膜的孔径受控于溅射功率和时间,功率30 W下沉积10 min约为68 nm,32 W下10 min约为58 nm,32 W下15 min约为25 nm。