交流电在Al2O3模板中沉积金属机理探讨

以铝阳极氧化形成有序的多孔氧化铝为模板,利用交流电在模板孔洞中沉积金属Ag得到纳米Ag粒子/Al2O3组装体系,透射电镜观察证实在氧化铝模板中有金属纳米Ag粒子存在.分析了交流电能在孔洞中沉积金属的原因是由于Al/Al2O3界面的整流特性,测量了Al/Al2O3界面的I－U关系曲线.     

交流电在Al_2O_3模板中沉积金属机理探讨

以铝阳极氧化形成有序的多孔氧化铝为模板,利用交流电在模板孔洞中沉积金属Ag得到纳米Ag粒子/Al2O3组装体系,透射电镜观察证实在氧化铝模板中有金属纳米Ag粒子存在.分析了交流电能在孔洞中沉积金属的原因是由于Al/Al2O3界面的整流特性,测量了Al/Al2O3界面的I－U关系曲线.     

硅基超薄多孔氧化铝膜的制备

将二次阳极氧化法应用于硅基铝膜的制备, 在草酸溶液中得到了厚度可控的硅基超薄多孔氧化铝膜(PAM), 厚度小于100 nm. 实验中记录了氧化电流随时间的实时变化曲线, 发现硅衬底的氧化电流在大幅下降前有一小幅波动. 对应于Al/Si界面的氧化过程中, 孔洞底部之间的残留铝岛被优先氧化, 可将此作为终止铝氧化的标志. 扫描电镜(SEM)观察表明, 二次氧化提高了孔洞分布的均匀性, 使得孔在一定的区域内呈现有序六角分布.这种模板可进一步用于硅基纳米器件和纳米结构的制备.     

镁合金阳极氧化膜的结构、成分及其耐蚀性

采用电压-时间曲线、膜厚-时间曲线、X射线衍射法、扫描电镜、能量色散谱仪、X射线光电子能谱法、全浸腐蚀实验和极化曲线等方法分别研究了AZ91D铸镁合金阳极氧化成膜动力学过程、阳极氧化膜的表面形貌、结构、元素组成、元素价态以及相成分和膜层的耐蚀性.结果表明,在阳极氧化的4个阶段中,由于各个阶段所生成膜的厚度、结构和成分等均不同,因此膜的耐蚀性相差很大;镁合金阳极氧化时耐蚀性最好的膜层是在阳极氧化过程中的第阶段和第阶段的交界处所生成的膜层;镁合金阳极氧化膜中含有Mg,O,Si,B和少量的Al,Na元素,膜层主要由MgO,MgSiO₃和Mg3B2O6组成.     

脉冲阳极氧化条件对多孔硅法布里-珀罗干涉特性影响

采用电化学脉冲阳极氧化法制备具有干涉效应的多孔硅. 研究电流密度、有效阳极氧化时间、电解液组成对多孔硅法布里-珀罗(F-P)干涉特性的影响, 利用光纤光谱仪测量多孔硅反射光谱并计算其光学厚度. 结果表明, 当阳极氧化电流密度78 mA•cm－2、有效阳极氧化时间5 min、氢氟酸与乙醇体积比VHF∶VEtOH＝2∶1时, 制备的多孔硅法布里-珀罗干涉条纹均匀, 膜层性质稳定; 当与饱和乙醇气体接触时, 多孔硅反射光谱吸收峰位由612红移到637 nm, 光学厚度由5864增加到6296 nm, 表明利用多孔硅法布里-珀罗干涉效应检测乙醇气体思路是可行的.     

复合稀土铝阳极氧化膜的耐蚀性研究

用金属氧化物前驱体法,在前处理阶段添加稀土再进行阳极氧化,获得了Nd和Ce改性的铝阳极氧化膜.稀土含量在靠近氧化膜/基体界面处达到0.9%左右,由内向外逐渐降低,氧化膜外表面处的含量约为0.5%.稀土前处理后制备得到的阳极氧化膜耐蚀性能比普通硫酸阳极氧化膜有明显提高,其中Ce改性的氧化膜作用尤为明显;经过NaCl溶液浸泡15 d以后,经稀土改性的阳极氧化膜仍然保持良好的耐腐蚀性.稀土引入后,阳极氧化膜的孔径变小,膜更加致密,显微硬度提高.XPS测试表明氧化膜中的稀土Ce以CeO2和Ce2O3形式存在,而Nd以Nd2O3形式存在.阻抗测试表明氧化膜阻挡层的阻抗值增大,说明稀土除了改变氧化膜生长机制外,也可能通过掺杂作用改变氧化膜结构.     

纳米ZnO颗粒在阳极Al2 O3模板中的强光致发光研究

用金属醇盐水解法在阳极Al2O3模板的有序孔洞中生长了纳米量级的ZnO颗粒,并用扫描电子显微镜(SEM)和高分辨电子显微镜(HRTEM)对其形貌进行观察.对纳米ZnO/多孔阳极Al2O3模板组装体的光致发光谱进行测量,将组装体中纳米ZnO颗粒的发光强度与常规方法制备的纳米ZnO颗粒发光强度做了比较,就发光强度提高的原因进行了讨论.     

利用多孔阳极氧化铝研究载体孔洞尺寸对负载银粒子团聚的影响

 利用阳极氧化方法制备了具有规整的可控孔洞尺寸的多孔Al2O3 膜,并以此模拟实际的催化剂载体制备了负载银催化剂. 采用扫描电镜、能量分散谱、透射电镜、X射线衍射和X射线光电子能谱等手段,研究了多孔阳极氧化铝的孔洞大小对负载的银粒子团聚的影响. 结果表明,载体孔洞尺寸对银粒子团聚可能起到限制作用,而且这种限制作用随载体孔洞尺寸增大而减小. 当载体的孔洞尺寸约为50 nm时,随温度升高银粒子的团聚和生长都不明显; 当载体的孔洞尺寸约为200 nm时,随温度升高银粒子发生一定程度的团聚和生长,但孔洞尺寸的限制作用仍存在. 这种载体尺寸的限制作用可以有效地阻止催化剂活性组分的团聚.     

铝阳极氧化膜阻挡层的去除方法

多孔型铝阳极氧化膜常被用作制备纳米阵列材料的模板,然而阻挡层的存在却在很多方面制约了其应用.为此,已经提出了各种不同的方法来去除阻挡层.本文将这些方法分为2类,即剥离氧化膜去阻挡层和不剥离氧化膜去阻挡层.前者包括化学腐蚀法、干蚀法、电解剥离法;后者包括阶梯降压法、高电流击穿法、电化学法和有多孔铝支撑的化学溶解法.其中,化学腐蚀法和干蚀法的工艺条件已相当成熟,得到了广泛应用,而其它几种方法还多处于实验室研究阶段.由于氧化膜脆性很大,因此,不剥离氧化膜原位去除阻挡层的方法具有更大的实用价值.     

阳极氧化物纳米孔道和TiO2纳米管形成机理的研究进展

自组织有序的TiO2纳米管和多孔型阳极氧化膜(PAO)因其潜在的应用价值而倍受关注.阀金属的阳极氧化研究了80多年,但是六棱柱元胞结构和多孔纳米管的形成机理至今尚不清楚.本文不是简单地综述PAO的形成机理,而是从更宽的视角综述了致密型阳极氧化膜与PAO的本质联系和形貌差异.对比两种膜的形貌差异和生长过程有助于孔洞形成本质的认识.简要综述了PAO的传统"场致助溶(FAD)"理论和局限性,重点综述了PAO形成机理的最新研究进展,包括粘性流动模型、阻挡层击穿模型、氧气气泡成孔模型、等电场强度模型等.在充分对比分析最新成果的基础上,对PAO机理研究的发展趋势进行了展望:采用超声氧化、真空或高压条件下氧化以及对电解液中添加碳酸钠或还原剂等方法,对揭示孔洞形成和自组织的本质将会有很大帮助;从电流和阳极氧化效率角度入手,是探究传统FAD理论的物理本质的有效途径.     

Regularities of photostimulated conversions in nanometer aluminum layers

The gravimetric and optical spectroscopic methods reveals that light irradiation with λ = 300–750 nm and intensity I = 6.9 × 10¹⁴–1.1 × 10¹⁶ quanta cm⁻² s⁻¹ for τ = 1–160 min in atmospheric conditions significantly changes the absorption and reflection spectra and mass of aluminum films (d = 2–200 nm). The kinetic curves of the degree of conversion versus aluminum film thickness are satisfactorily described in the inverse logarithmic and parabolic terms. The contact potential difference is measured for Al and Al₂O₃ films along with the photo-EMF of Al-Al₂O₃ systems. The suggested model includes the stages of generation and redistribution of nonequilibrium charge carriers in the contact field of Al-Al₂O₃ systems, oxygen adsorption, Al³⁺ diffusion, and Al₂O₃ formation.     

纳米晶状磷酸钙盐/Al2O3-Ti生物复合材料的制备与结构表征

0引言众所周知,钛及其合金具有优良的机械力学性能,但其生物活性不足。因此,在金属基体上涂敷一层生物活性涂层,结合金属与生物活性材料的各自优势,已成为世界各国学者研究最为活跃的生物复合材料体系之一。该体系可用于临床医学,作为人体硬组织等的修复替换材料。目前,已开发出多种在金属基体上制备生物活性涂层的工艺和方法。如:等离子沉积法[1]、离子束溅射法[2]、激光熔覆法[3]、溶胶鄄凝胶法[4]、电化学沉积与水热处理合成法[5]、电泳沉积[6]、电结晶[7]等多种方法。但现有涂层材料尚存在一些问题:(1)由于替换材料的高硬度而导致其周围硬组织坏死[8];(2)由于疲劳磨损或热膨胀不匹配引起涂层脱落[9];(3)由于异质相导致生物活性降解[10]。因此,研究新的制备工艺,开发新的生物复合材料体系就显得十分重要。考虑到Al2O3具有优异的抗磨损、耐腐蚀等性能,以及较好的生物相容性,常作为临床选用的人造硬组织承载材料[11],故在本研究工作中,我们首次采用阳极氧化与水热处理复合工艺研制酸式磷酸钙/Al2O3鄄Ti生物复合材料体系。该体系不同于由日本Ishizawa等研制的HAp/TiO2鄄Ti复合体系[12]。主要体现在两...     

Investigation of the incorporation of electrolyte anions in porous anodic Al2O3 films by employing a suitable probe catalytic reaction

A new method has been developed capable of describing the incorporation of electrolyte anions along the pore wall surface and across both the barrier layer and the pore wall oxide after the establishment of the steady state of growth of porous anodic Al₂O₃ where other methods cannot be applied to obtain reliable results. The knowledge of the nature/composition of anodic oxides as regards the incorporation of species like electrolyte anions is of specific importance for both the understanding of the electrochemical mechanism of oxide production and growth and the scientific and technological applications of porous anodic Al₂O₃ films. The method consists of the selection and use of a suitable catalytic probe reaction on porous anodic oxides at thicknesses varying from a value near zero up to the maximum limiting thickness and the treatment of the experimental reaction rate results by a properly developed mathematical formalism. This method was employed in anodic Al₂O₃ films prepared in H₂SO₄ anodizing electrolyte at a constant bath temperature and different current densities using as a probe reaction the decomposition of HCOOH on these oxides, which is almost exclusively a dehydration reaction, at relatively high reaction temperatures, 350 °C and 390 °C, where the effect of other species except SO₄ ²⁻ incorporated in the oxide on the reaction rate is eliminated. It has been shown that the fraction of the intercrystallite surfaces occupied by SO₄ ²⁻ follows a parabola-like distribution. It has a significant value at the pore base surface, depending on the current density, then it passes through a maximum along the pore wall surface and across both the barrier layer and the pore walls near the pore bases at positions depending on the current density and then becomes almost zero at the mouths of the pores of the oxide with the maximum limiting thickness and at both the Al₂O₃/Al interface and cell boundaries. The maximum value of the surface coverage is almost independent of the current density and is always near 1, showing an almost complete saturation of intercrystalline surfaces at these positions. The above distribution of surface coverage predicts a qualitatively similar distribution of the SO₄ ²⁻ bulk concentration across both the barrier layer and pore wall oxide around the pore bases. The method may be improved and developed further either for a more detailed investigation of the above films or to investigate films prepared in other pore-forming electrolytes. Received: 30 July 1998 / Accepted: 30 September 1998     

Formation of endogenous MgO and MgAl2O4 particles and their possibility of acting as substrate for heterogeneous nucleation of aluminum grains

Aluminum containing 4 wt.% magnesium was oxidized at a temperature for different oxidation times and analyzed by high‐resolution electron microscopy. A thin oxidized layer of about 5 µm, which is composed of MgO, forms at short oxidation time and gradually increases. High‐resolution microstructures reveal that the oxidized layers are porous regardless of oxidation time. After extended oxidation time, discrete MgAl₂O₄ particles formed as a result of the reaction of initially formed MgO, liquid aluminum, and oxygen introduced from air through the porous MgO. Furthermore, it is clear by high‐resolution lattice images that MgAl₂O₄ particles are covered with thin Al₂O₃, whereas MgO is bonded intimately to aluminum. Therefore, MgAl₂O₄ particles that form naturally during oxidation are difficult to act as a direct substrate for nucleation of aluminum grains because of the coverage of Al₂O₃. In contrast, MgO shows the possibility of acting as a substrate for the aluminum nucleation. The formation mechanism of MgO and MgAl₂O₄ and their possibility of acting as substrates for nucleation of aluminum grains suggest that atomic level bonding and mismatches of nucleant/nucleus metal should be considered for correct evaluation of the possibility of heterogeneous nucleation of metallic matrix on a potent nucleant. © 2015 The Authors. Surface and Interface Analysis Published by John Wiley & Sons, Ltd.     

Interface physicochemical processes controlling sulphate anion incorporation in porous anodic alumina and their dependence on the thermodynamic and transport properties of cations

Aluminium was anodised in H₂SO₄, LiHSO₄, NaHSO₄, KHSO₄, Mg(HSO₄)₂ and Al(HSO₄)₃ electrolytes. The kinetics of growth of porous anodic alumina films and of the pore wall oxide dissolution during anodisation was studied. Based on the derived kinetic parameters, suitable physicochemical processes in the barrier layer electrolyte interface controlling the anion incorporation in the barrier layer were suggested and relevant models were formulated. According to these processes Al³⁺ and H⁺ ions are rejected from the pore base surface in the attached double layer, where Al³⁺ ions are solvated, and are transferred to the pore filling solution. The strongly different mobilities of Al³⁺ and H⁺ and the necessary space negative charge density distribution in the double layer result in similar concentration distributions of Al³⁺ and anions inside it, which differ strongly from that of H⁺. These Al³⁺ and anion concentrations increase with decreasing mobility of the main cations in the solution which depends on their hydration enthalpy and transport mechanism. The concentration of incorporated anions inside both a thin surface layer of the barrier layer and the double layer vary similarly. For identical surface density and base diameter of pores the decrease of the above mobility reinforces anion incorporation.     

Controlled self-assembly of nanoporous alumina for the self-templating synthesis of polyaniline nanowires

In this report, the self-templating synthesis of polyaniline nanowires on prestructured aluminum is described, emphasizing that anodization and electropolymerization can occur at the same time by a single electrochemical process. The method is based on the principle that the anodization of predefined aluminum in H₂SO₄ leads to the formation of highly ordered porous alumina and aniline monomer can be electrochemically polymerized in the formed porous alumina by the anodic reaction. XPS analysis reveals that polyaniline nanowires prepared in this work is protonated emeraldine.     

Large-scale preparation of aluminum borate-coated aluminum oxide nanowires

Single-crystal and uniform aluminum borate (Al₄B₂O₉)-coated aluminum oxide nanowires have been synthesized in high purity and in large yield via a reaction of metal aluminum with boron oxide in the presence of carbon nanotubes (CNTs). The aluminum oxide nanowires exhibit a well-crystallized one-dimensional structure with diameters ranging from 50 to 70 nm, and the Al₄B₂O₉ have a coating thickness of about 1-5 nm. CNTs play a crucial role in the formation of the important ceramic nanowires, by providing a platform to grow the composite structure. The growth mechanism was proposed by the detailed microscopy observations.     

Multilayered separator based on porous polyethylene layer,Al2O3 layer,and electro-spun PVdF nanofiber layer for lithium batteries

With an aim to enhance the thermal stability and electrolyte wetting of a polyethylene porous separator, an Al₂O₃ nano-powder layer and an electro-spun PVdF nanofiber layer were successively formed on both sides of the polyethylene separator. The Al₂O₃ layer provides excellent thermal stability as indicated by thermal shrinkage of only 7.8 % in area at 180 °C and absence of a meltdown up to 200 °C. The electrolyte uptake of the multilayer separator was increased with the thickness of the nanofiber layer. As a result, discharge capacity, rate capability, and cycle life of the lithium ion batteries employing the PVdF nanofiber layers were improved, overcompensating for a loss of performance caused by the Al₂O₃ layer. Therefore, the multilayer approach is highly effective in improving both the performance and safety of lithium ion batteries.     

Influence of oxides of the rare earth elements (La2O3, CeO2) on the thermal stability of highly dispersed aluminum oxide

It has been established that addition of oxides of the rare earth elements (La₂O₃, CeO₂, and their mixtures) increases the thermal stability of the porous structure of highly dispersed aluminum oxide-a secondary carrier of structured catalysts. The greatest stabilizing effect was noted with La₂O₃. The reason for this effect is the formation of a solid solution of La₂O₃ in Al₂O₃ which prevents the diffusion of aluminum ions and slows the transition of low temperature modifications of Al₂O₃ into high temperature α-Al₂O₃. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 318–323, September–October, 2006.     

用于苯选择加氢的Ru/Al2O3-ZrO2-NiO/堇青石蜂窝整体催化剂

使用浸涂法和氨气吸收沉积法制备了新型用于苯选择加氢的具有蛋壳型分布的Ru/Al₂O₃-ZrO₂-NiO/堇青石蜂窝整体催化剂,且在固定床整体反应器中对其性能进行了测试.该催化剂显示了较优的选择性和稳定性,并且在低的ZnSO₄浓度(0.5%问题)下环己烯产物收率可达24.7%.采用N₂吸附-脱附法,电感耦合等离子体发射光谱,光学显微镜,扫描电子显微镜及能量色散X射线光谱仪等技术研究了影响催化剂性能的因素.结果表明,NiO的引入减少了涂层中的微孔含量,有利于在低的添加剂浓度下提高环己烯选择性.ZrO₂的存在抑制了涂层的烧结,保证涂层在1373K高温焙烧后仍有较大的比表面积.Ru的蛋壳分布、薄的涂层厚度、较少的微孔含量、较大的比表面积和狭窄的孔分布可能是影响整体蜂窝催化剂中该特殊催化行为的重要因素.