Anodic oxidation behaviour of aluminium in propylene carbonate

The anodic oxidation behaviour of pure aluminium (Al) in propylene carbonate was investigated using electrochemical measurements, microscopic observations, elemental and gravimetric analyses. The formation and growth of the oxide were observed on the surface of Al in the early stage of anodizing. Further anodic oxidation led to the breakdown of a part of the oxide film, resulting in simultaneous pitting corrosion because of the limitation of mass transfer in the oxide layer.     

Anodic oxidation of InAlAs

The anodic oxidation of InAlAs is investigated by transmission electron microscopy, Rutherford backscattering spectroscopy and medium energy ion scattering in order to elucidate the mechanism of oxide growth. For this purpose, anodizing was carried out at 5 mA cm⁻² in 0.1 M sodium tungstate and 0.1 M ammonium pentaborate electrolytes at 293 K, which results in relatively efficient film growth over an initial voltage increment of about 70 V. In this period, an amorphous oxide develops with a formation ratio of 2.0 ± 0.2 nm V⁻¹. The film consists mainly of an outer layer of In₂O₃ and an inner layer of units of In₂O₃, Al₂O₃ and As₂O₃, the former representing about 14% of the film. There is suggestion of a fine, intermediate layer containing units of In₂O₃ and Al₂O₃ only. The layering correlates with the bond energies of the cation and oxygen species in the oxide and hence their relative migration rates. Further, for films formed in tungstate electrolyte, tungsten species are incorporated into the outer 40% of the film. Bubbles of oxygen gas are present in the film, probably developed within the In₂O₃ layer. At higher voltages, the film undergoes breakdown, with resulting major changes in the film morphology.     

采用微机分布式控制的阳极化电源系统的研究

阳极化电源是军工产品在进行硬质极化时频繁使用的关键设备之一，过去硬质阳极化过程中使用单机电源，工作人员需要经常进入非常恶劣的工作环境之中长时间工作，这对他们的身体健康是不小的威胁，而且效率十分低下。本文提出了一种采用微机分布式控制的阳极化电源系统解决了上述问题，详细介绍了该系统的三个主要组成部分的功能及其特点，分别论述了三者的设计方案。实际应用表明，该系统对提高工作效率、降低工作人员的劳动强度和增加系统可靠性具有重要作用。     

Tribological Behavior of Ceramic Surface Layers of Ring and Box Spinning Machines Aluminum Elements Rubbing against Yarn

The paper deals with the influence of hard anodizing coatings on ring and box spinning machines aluminum elements rubbing against the yarn upon the wear of these parts and the quality of the yarn. The process of hard anodic oxidation substantially increases the durability of the chosen parts of spinning frames; i.e, the spindles and rotors. For example, the wear intensity of collecting groove of the rotor without the oxides coating was found to be of 0.42 μm/h, after about 6000 h of work, while after the process of anodic oxidation it decreased to 0.0022 μm/h. On the other hand, in case of a ring spinning frame the wear intensity of the surface of the spindle coat neck without the oxides coating amounted to 0.068 μm/h, while after anodic oxidation it decreased to 0.00048 μm/h.     

Chemical and mechanical properties of anodized cp-titanium in NH4 H2PO4/NH4F media for biomedical applications

Potentiostatic anodizing of commercially pure titanium, using ammonium phosphate and ammonium fluoride solution as electrolyte is studied. The objective is to generate titanium oxides on the surface and phosphor compounds presenting good protective and mechanical properties, and proper adhesion to the metal substrate to remain during surgical orthopedic procedures (implants). Two different applied potentials were used to obtain different surface oxides morphologies (20 and 30 V). The characterization and quantification of the generated deposits is presented as a starting point for the future application of these composite types of materials. X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy techniques showed the presence of phosphor compounds and anatase (TiO₂) as the main constitutive phases.     

Growth of porous anodic films on sputtering-deposited aluminium incorporating Al-Hf alloy nanolayers

Formation of porous anodic films on sputtering-deposited aluminium incorporating Al-Hf tracer layers has been examined at constant current in sulphuric and phosphoric acids. Hafnium was selected as the tracer species since the migration rates of Hf⁴⁺ and Al³⁺ ions are similar in barrier-type anodic alumina. The distribution of hafnium in the films was determined using ion beam analysis, scanning electron microscopy and transmission electron microscopy. Increases in the anodizing voltage and barrier layer thickness accompany the oxidation of hafnium and the migration of Hf⁴⁺ ions through the barrier layer region of the porous film. Hf⁴⁺ and Al³⁺ ions that migrate to the pore bases are lost to the electrolyte. Other Hf⁴⁺ ions are incorporated into the cell walls. For films formed in phosphoric acid, with relatively thick barrier layers, channelling of the ion current leads to accelerated outward transport of Hf⁴⁺ ions toward the pore base, while a U-shaped inner edge of the hafnium distribution beneath the pores is associated with more slowly transported hafnium species. The tracer behaviours for films formed in both acids are consistent with the transport of Hf⁴⁺ ions in the barrier layer regions by a combination of flow of film material and ion migration, the flow being a key factor in the development of the pores. The percentage losses of Hf⁴⁺ and Al³⁺ ions from the films to the electrolyte are relatively similar, correlating with their similar migration rates, and contrast with the retention in the film of slow migrating W⁶⁺ ions, found previously, due to a more dominant role of flow.     

同一工艺在钢铝等不同金属表面镀制黑色氮钛膜研究

介绍了真空镀黑色氮钛膜工艺化发黑工艺的缺点所存在的问题,用真空镀黑色氮钛膜工艺代替钢磷化或 铝阳极氧化等表面发黑工艺可以克服磷化或铝极氧化工艺的缺点,可使其耐磨性 及耐蚀性得到提高     

Local deposition of polypyrrole on aluminum by anodizing, laser irradiation, and electrolytic polymerization and its application to the fabrication of micro-actuators

Polypyrrole was deposited at selected areas on aluminum by anodizing, laser irradiation, and electrolytic polymerization, and the application of the technique for fabricating micro-actuators was attempted. Aluminum specimens covered with porous type anodic oxide films were irradiated with a pulsed Nd-YAG laser to remove the oxide films locally, and then thin Ni layers were deposited at areas where film had been removed. Polypyrrole could be successfully deposited only on the Ni layer by anodic polarization of the specimens in pyrrole monomer solution, and a polypyrrole/Ni bilayer structure could be obtained by dissolution of the aluminum substrate and anodic oxide film in NaOH solutions. The bilayer structure was found to be inactive to doping and dedoping of ions during anodic and cathodic polarization. A three-layer structure, nitrocellulose/Ni/polypyrrole, fabricated by electrolytic polymerization after nitrocellulose coating on a Ni layer detached from the aluminum substrate, showed ion-doping and -dedoping activity, suggesting the possibility of fabricating micro-actuators in this manner.     

Anodic film growth in the Al-Ta alloy system

The ionic transport numbers, relative migration rates of cation species and formation ratios are reported for barrier anodic films formed on metastable, solid solution Al-Ta alloys, with compositions extending from the aluminium-rich to the tantalum-rich ends of the system. The data were obtained by marker experiments, using ion implanted xenon, transmission electron microscopy, Rutherford backscattering spectroscopy and medium energy ion scattering. The films are amorphous and form by migration of metal and oxygen species. The ionic transport numbers and the formation ratios depend approximately linearly upon the composition of the alloy, between the values for anodic alumina and anodic tantala. The migration rate of Al³⁺ ions exceeds that of Ta⁵⁺ ions, but reduces in relative magnitude as the tantalum content of film increases. The faster migration of Al³⁺ ions is consistent with the higher energy of the Ta⁵⁺-O bond compared with that of the Al³⁺-O bond. Due to the difference in mobilities of the cation species, the films comprise an outer layer of alumina and an inner layer containing units of both alumina and tantala. The two-layered films can develop fingers of inner layer oxide that penetrate the outer alumina layer due to the higher ionic resistivity of the alumina. Such channelling of current can lead to mixing of inner layer oxide and alumina and thereby hinder formation of an alumina layer, particularly in films on the more tantalum-rich alloys.     

Growth of porous type anodic oxide films at micro-areas on aluminum exposed by laser irradiation

Aluminum covered with pore-sealed anodic oxide films was irradiated with a pulsed Nd-YAG laser to remove the oxide film at micro-areas. The specimen was re-anodized for long periods to examine the growth of porous anodic oxide films at the area where substrate had been exposed by measuring current variations and morphological changes in the oxide during the re-anodizing. The chemical dissolution resistance of the pore-sealed anodic oxide films in an oxalic acid solution was also examined by measuring time-variations in rest potentials during immersion.The resistance to chemical dissolution of the oxide film became higher with increasing pore-sealing time and showed higher values at lower solution temperatures. During potentiostatic re-anodizing at five 35-μm wide and 4-mm long lines for 72 h after the film was removed the measured current was found to increase linearly with time. Semicircular columnar-shaped porous type anodic oxide was found to form during the re-anodizing at the laser-irradiated area, and was found to grow radially, thus resulting in an increase in the diameter. After long re-anodizing, the central and top parts of the oxide protruded along the longitudinal direction of the laser-irradiated area. The volume expansion during re-anodizing resulted in the formation of cracks, parallel to the lines, in the oxide film formed during the first anodizing.