用AFM研究阳极氧化铝的不稳定生长

用原子力显微镜(AFM)研究了多孔阳极氧化铝(AAO)模板的不稳定生长. 结果表明:AAO模板的不稳定生长导致了纳米孔道结构有序度的降低.在H₃PO₄溶液中生长的AAO模板孔道结构稳定性较差;而在H₂C₂O₄溶液中生长的AAO模板稳定性依赖于氧化电压和电流密度,在低电压和电流密度下稳定性较好,高电压和电流密度下稳定性较差. 充分利用这种不稳定生长特性,通过控制AAO模板的阳极氧化条件,可得到具有分枝孔道结构的特殊模板,这为利用模板法制备各种Y形或T形纳米线、管提供了新的发展空间.     

大长径比有序多孔阳极氧化铝模板的制备及用于镍纳米线阵列

报道一种恒电流二次氧化制备大长径比(>1000)阳极氧化铝(AAO)模板的方法,研究氧化时间和氧化电流密度分别对制备的AAO模板的表面形貌、孔径大小、厚度等的影响.结果表明,AAO模板的表面形貌及厚度n受m氧、厚化度电约流为密2度00及μ氧m、化长时径间比的为影10响0;-当13氧00化的电高流质密量度A为AO8模m板A·.c采m用-2电时化,氧学化沉1积8方h能法在制制备备出的孔A径A为O模15板0-的20孔0中成功制备了Ni纳米线阵列,分别用扫描电镜(SEM)、高分辨透射电镜(HRTEM)、X射线衍射(XRD)和X射线能量散射光谱(EDS)对其进行了表征;结果显示,制备的Ni纳米线排列整齐有序,每根Ni纳米线直径几乎相同,约150nm,长度约为180-200μm,长径比为1200-1300,与AAO模板的参数一致.研究了Ni纳米线阵列的长径比对其磁性能的影响,发现大长径比的Ni纳米线阵列具有明显的磁各向异性,而长径比约为200的Ni纳米线阵列未表现出明显的磁各向异性.本文结果表明,恒电流二次氧化方法能制备大长径比的AAO模板,并能用于制备大长径比的一维纳米材料阵列,可望在制备具有特殊光学、磁学等性能材料方面得到应用.     

基于层层自组装的CuTsPc/DPDCH纳米管的制备

在阳极多孔氧化铝模板中利用层层自组装技术制备出了高度有序的聚电解质磺化酞菁铜(CuTsPc)/4,4′-联吡啶盐酸盐(DPDCH)纳米管, 并对其组装过程用UV-Vis, XRD和FT-IR进行了分析, 纳米管的微观形貌通过SEM和TEM进行表征. 结果表明, 第一层 CuTsPc和第二层DPDCH在AAO模板上的沉积平衡时间均约为60 min, 沉积过程主要有三个阶段: 模板孔外的吸附过程、孔内扩散控制的沉积过程和孔内表面沉积控制过程. CuTsPc主要以磺酸根吸附于AAO模板上. CuTsPc/DPDCH纳米管为非晶态体系. CuTsPc/DPDCH纳米管的外径和壁厚分别为200和20 nm, 外径受控于AAO模板的孔径, 壁厚与组装的层数有关, 利用此方法还可以制备其他带有相反电荷的有机小分子对纳米管或纳米线.     

溶胶-凝胶模板法合成SmFeO3纳米线

通过阳极氧化在质量分数为0.3 mol·L^-1草酸溶液中制得多孔氧化铝膜。经5%（质量分数）的磷酸扩孔处理得到具有孔径大小均一,排列有序,并具有一定厚度的阳极氧化铝模板（AAO）。用溶胶-凝胶法在氧化铝模板中制备了直径约为50 nm的有序SmFeO3纳米线阵列。用扫描电镜（SEM）、透射电镜（TEM）和X射线衍射仪（XRD）对SmFeO3纳米线的形貌、结构以及相组成进行了分析。结果发现：纳米线的长度受控于氧化铝模板的厚度,直径与氧化铝模板的孔径相等。同时分析了纳米线的形成机制。     

制备不同孔径的氧化铝模板

将适量的有机溶剂加入电解液中，在15 ℃左右制备得到孔径大于200 nm的氧化铝模板.该法使电解时间缩短，加快了制备模板的过程， 是氧化铝模板的有效制备方法.将该方法与传统方法相结合，可以制备孔径在20～250 nm间的氧化铝模板. 实验表明：有机溶剂的加入可有效避免电解时热量的迅速产生, 通过改变实验条件可调控氧化铝模板的孔径.     

溶胶-凝胶模板法制备BaTiO3纳米线及其光催化性能

纳米线为准一维纳米材料[1],因其具有优异的光学、电学及力学性能而引起人们的极大关注.它的制备方法有许多种,如分子束外延法、光刻法、CVD法、模板法[2]等.其中模板法由于具有实验装置简单,操作容易,形态可控,适用面广等特点而成为纳米材料合成领域的一大焦点.常用的模板有:有序空洞阵列氧化铝模板、含有孔洞无序分布的高分子模板、纳米洞孔玻璃模板.其中阳极氧化铝(AAO)模板具有孔径均一、排列有序、孔密度高、热稳定性好且孔径大小可控等优点,成为模板合成法中最常用模板之一[3].     

电化学法制备Ni-W-P纳米线阵列电极及其催化析氢性能

采用二次氧化法制备了多孔阳极氧化铝(AAO)模板, 通过控制电位沉积技术在AAO模板内组装了Ni-W-P合金纳米线阵列. 在扫描电子显微镜(SEM)下观察到Ni-W-P纳米线表面光滑, 长约20 μm, 直径均匀(约为100 nm), 与AAO模板孔径基本一致. 阴极极化曲线和交流阻抗图谱(EIS)的测试结果表明, Ni-W-P合金纳米线阵列电极析氢反应(HER)电阻减小, 具有更高的催化析氢活性, 电流密度为10 mA·cm^-2时, 析氢极化电位较Ni-W-P合金电极正移约250 mV.     

双槽法电沉积Cu/Ni多层纳米线有序阵列

以多孔阳极氧化铝（AAO）为模板，采用双槽法电沉积工艺制得高度有序的Cu/Ni多层纳米线阵列。利用扫描电镜（SEM）和透射电镜（TEM）对Cu/Ni多层纳米线进行了表征，观察到纳米线表面平滑，多层结构清晰，各子层厚度均匀，直径约为 100 nm，与AAO模板孔径基本一致。由选区电子衍射（SAED）照片可知，多层纳米线中Cu层和Ni层均为单晶结构。振动样品磁强计（VSM）测试结果表明，Cu/Ni多层纳米线阵列具有明显的垂直磁各向异性，外加磁场垂直和平行于AAO模板表面时，磁滞回线的矩形比分别为 0.701 和 0.101 ，矫顽力分别为 589 Oe和 202 Oe。通过控制铝阳极氧化工艺及电沉积时间，可获得不同直径、不同子层厚度的Cu/Ni多层纳米线阵列。     

镍有序纳米孔洞阵列厚膜的制备和表征

以阳极氧化铝为模板,通过两步复型的方法,制备了金属镍的有序纳米孔洞阵列厚膜.镍膜的孔道彼此平行,呈六角排列,孔径约40 nm,孔洞间距80 nm,孔密度约1011个/cm2 .     

钯负载介孔氧化锆基复合催化材料的合成与表征

利用表面活性剂辅助模板及适当后处理工艺实现了少量贵金属氧化钯及稀土氧化铈在有序介孔氧化锆孔道中或孔道表面的均匀分散/负载. 借助XRD, TEM, EDS等分析手段进行样品结构表征; 同时针对不同催化体系探讨了丙烯催化氧化以及Heck反应的催化性能. 研究结果表明, 贵金属钯/稀土氧化铈负载的有序介孔氧化锆体系对丙烯氧化具有良好催化活性, 钯直接负载介孔氧化锆的体系具有优异的Heck反应催化选择性及较少的催化剂使用量.     

MCM-41介孔分子筛掺杂的微孔型聚合物电解质的制备与表征

以介孔分子筛MCM-41作填料,丙酮与二甲基甲酰胺混合液为溶剂,用直接造孔成膜的方法制备了微孔型聚合物电解质膜.该法避免使用造孔增塑剂,既简化了制膜工序,又减少电池中副反应的发生,使电池性能得以提高.MCM-41分子筛具有六方有序排列的单一柱状孔道结构和纳米级的粒子尺度,其骨架结构单元与一般聚合物电解质常用的纳米SiO2填料具有相同的化学成分,该分子筛堆积时形成的表面空隙及其独有的一维介孔孔道对聚合物电解质微孔的形成与连通、电导率的提高都具有重要作用,是一种极具实用价值的新型无机填料.     

MICROPOROUS PVDF-HFP-BASED POLYMER MEMBRANES FORMED FROM SUPERCRITICAL CO2 INDUCED PHASE SEPARATION

Microporous poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)membranes following supercritical CO_2 induced phase separation process were prepared using four solvents.The solid electrolytes of PVDF-HFP were formed by microporous PVDF-HFP membranes filled and swollen by a liquid electrolyte.The effect of the solvents on the morphology and structure,electrolyte absorptions and lithium ionic conductivity of the activated membranes were investigated.It was approved that all the membrane had the simi...     

Pushing the size limits in the replication of nanopores in anodized aluminum oxide via the layer-by-layer deposition of polyelectrolytes

We report on the successful replication of the smallest pores in anodized aluminum oxide (AAO) via the layer-by-layer (LBL) deposition of polyelectrolytes to date to yield free-standing, open nanotubes with inner and outer diameters (±2σ) down to 37 ± 4 and 52 ± 19 nm, respectively. This work is based on the fabrication of defined arrays of highly regular nanopores by anodic oxidation of aluminum. Pores with pore diameters between 53 ± 9 and 356 ± 14 nm and interpore distances between 110 ± 3 and 500 ± 17 nm were obtained using an optimized two-step anodization procedure. 3-(Ethoxydimethylsilyl)propylamine-coated pores were replicated by alternating LBL deposition of poly(styrenesulfonate) and poly(allylamine). The detrimental adsorption of polyelectrolyte on the top surface of the template that typically results in partial pore blocking was eliminated by controlling the surface energy of the top surface via deposition of an ultrathin gold layer. The thickness of the deposited LBL multilayer assembly at the pore orifice agreed to within the experimental error with the thicknesses measured by variable angle spectroscopic ellipsometry and atomic force microscopy (AFM) for layers assembled on flat substrates. The selective dissolution of the alumina template afforded free-standing, open polymer nanotubes that were stable without any cross-linking procedure. The nanotubes thus obtained possessed mean outer diameters as small as 52 nm, limited by the size of the AAO template.     

Preparation of Zeolite X Membranes on Porous Ceramic Substrates with Zeolite Seeds

Zeolite X membranes were investigated by in-situ hydrothermal synthesis on porous ceramic tubes precoated with zeolite X seeds or precursor amorphous aluminosilicate, and porous α-Al2O3 ceramic tubes with a pore size of 50 200 nm were employed as supports. Zeolite X crystals were synthesized by the classic method and mixed into deionized water as a slurry with a concentration of 0.2 0.5wt%, having a range of crystal sizes from 0.2 to 2μm. Crystal seeds were pressed into the pores near the inner surface of the ceramic tubes, and crystallization took place at 95℃ for 24-96 h. It was also investigated that Boehmite sol added with zeolite X seeds was precoated on ceramic supports to form a layer of γ-Al2O3 by heating, and hydrothermal crystallization could then take place to prepare the zeolite membranes on the composite ceramic tubes. The crystal species were characterized by XRD, and the morphology of the supports subjected to crystallization was characterized by SEM. The composite zeolite membranes have zeolitic top-layers with a thickness of 10-25 μm, and zeolite crystals can be intruded into pores of the supports as deeply as 100μm. The experimental results indicate that the precoating of zeolitic seeds on supports is beneficial to crystallization by shortening the synthesis time and improving the membrane strength. The resulting zeolite X membrane shows permselectivity to tri-n-butylamine((C4H9)3N) over perfluro-tributyl-amine ((C4Fg)3N), and a permeance ratio of 57 for ((C4Hg)3N to (C4F9)3N could be reached at 350℃. Permeances of BZ, EB and TIPB through the zeolite membrane were also measured and were found to slightly increase with temperature.     

Solvent-dependent permeability in asymmetric ceramic membranes with tortuous or non-tortuous mesopores

Solvent-dependent transport and the role of surface interactions were examined in commercial mesoporous ceramic membranes using permeability and thermoporometry measurements. The membranes chosen were titania (TiO₂) with tortuous interconnected pores (1, 5, and 50 kDa, corresponding to pore diameters of ca. 8.2, 18.3, and 33.2 nm, respectively) and alumina (Al₂O₃) with non-tortuous 20 nm cylindrical pores. A pre-water/solvent/post-water permeability cycle was employed to account for structural differences between membranes and to gauge the effect of residual solvent on water permeability at different temperatures. Our results suggest that in both types of membranes, restricted permeability of 1-butanol and cyclohexane was due to a combination of surface sorption and an increase in disjoining pressure due to solvation forces. Sorption and solvation forces were prevalent as their length scales were on the same order of magnitude as the pore radii. For 1-butanol, chemisorption changed the surfaces from hydrophilic to hydrophobic, and led to a significant decrease in post-water permeability. While Darcy's law could not describe 1-butanol and cyclohexane permeability, it did apply to water and 1,4-dioxane in the 20 nm alumina membranes. Thermoporometry, coupled with permeability, was further used to evaluate surface wetting within the mesopores.     

静电纺制备纳米孔结构聚乳酸(PLLA)超细纤维

采用静电纺丝法制备了孔径为40～150 nm的PLLA纳米孔结构超细纤维,纳米孔不仅分布在纤维表面,而且存在于纤维内部.通过扫面电镜观察了纤维表面形貌.探讨了混合溶剂二氯甲烷/N,N-二甲基甲酰胺的比例、PLLA浓度、电场强度对PLLA纤维纳米孔大小、分布密度、深度的影响.结果表明通过调节PLLA溶液性质和纺丝参数,PLLA纤维的表面形貌可以在3种状态即光滑无孔、疏浅凹坑、密集深孔之间可控.二氯甲烷/N,N-二甲基甲酰胺比例为1∶4,PLLA浓度9%,电场强度1 kV/cm,环境温湿度分别为30℃和52%,静电纺丝所得PLLA超细纤维表面孔洞直径为150 nm,孔洞分布密集.纳米孔PLLA纤维形成的主要机理是由于静电纺丝过程中溶剂的快速挥发引起纤维表面温度急剧降低导致热致相分离而产生多孔结构.PLLA纤维膜的疏水性与纤维表面孔洞结构密切相关,纤维膜接触角最高可达146.6°.由于PLLA纤维的多孔结构,这种高疏水性的PLLA纤维膜能够快速、大量地吸油,90 s内吸收柴油达到90 g/g,25 min内可以达到145 g/g.     

Anodic alumina membranes with defined pore diameters and thicknesses obtained by adjusting the anodizing duration and pore opening/widening time

The through-hole porous anodic aluminum oxide (AAO) membranes were fabricated by a simple two-step anodization of aluminum in 0.3 M oxalic acid, 0.3 M sulfuric acid, and 2 wt.% phosphoric acid solutions under different operating conditions followed by the removal of the remaining Al substrate and the pore opening/widening process. The effect of duration of the second anodizing step on the thickness of the porous oxide layer and the influence of other anodizing conditions such as applied voltage, type of electrolyte, and purity of the substrate on the rate of porous oxide growth were discussed in detail. The pore opening procedure for all synthesized membranes was optimized, and the influence of the duration of chemical etching on structural features of AAO membranes, especially pore diameter, was studied. The rate of pore widening was established for AAO membranes formed in various anodizing electrolytes and for different temperatures of 5 wt.% H₃PO₄ used for alumina dissolution.

     

Cu/AAO纳米有序阵列复合结构的光吸收特性

采用电化学沉积工艺, 成功制备了铜/氧化铝(Cu/AAO)纳米有序阵列复合结构. 研究结果发现, 在λ为570 nm附近出现了明显的Cu表面等离子共振吸收峰, 且随Cu沉积量的增加, 吸收峰位稍有蓝移, 其强度逐渐增强, 峰形由宽变锐; 另外还发现, 该结构的吸收边随着Cu沉积量(或长径比)的增加大幅度红移, 可以实现在近紫外至近红外的大范围内移动, 最大频移量超过500 nm, 且Cu表面等离子振荡吸收峰会随着吸收边的大幅度红移被掩盖而逐渐消失. 对该结构光吸收边的调制机理进行了理论分析, 阐释了吸收峰逐渐消失的原因, 并从理论上定性地解释了导致吸收峰位蓝移及宽化的主要原因.     

Electrostatic exclusion on anionic membranes for ultrafiltration

This work concerns electrostatic processes on ionic membranes for ultrafiltration. The salt retention and the flow-rate of electrolytes are determined. The degree of swelling τ is controlled to deduce the volume fraction of pores. The salt retention varies with the ionic concentration of the solution and nature of the counter-ion; it is correlated with the net charge of the membrane. The influence of the ionic concentration of the electrolyte on the flow-rate is interpreted by introduction of a streaming potential.