Search results

The novel structures and properties of nanostructure and nanomaterials give people perfect artistic expression of feeling and sense, then the nanoart discipline is developed and is closely related on the nanotechniques. The many achieved novel nanostructures with strong anti-corrosion prepared by the anodization have been reviewed. The paper would raise public awareness of nanotechnology, nanomaterial and their impact on our lives.

Anodization is a very effective and simple technique to form various nanostructures of metal oxide. It includes hard anodization, mild anodization and pulse anodization. Many measures have been introduced anodization process to improve the quality of formed nanostructure and enhance its properties, such as anti-corrosion.

The formation mechanism of anodic aluminum oxide (AAO) by using the mild, hard and pulse anodization has been discussed. The pretexture process and many other measures have been taken in mild and hard anodization to improve the regularity of pore array and greatly accelerate the formation rate of AAO. The pulse anodization has been used to prepare the multilayer Y-branched AAO film, which exhibits steady rich and vivid structure colors and gives a very good artistic expression. Furthermore, many other metal oxide nanostructures such as TiO₂ and CuO have also been fabricated using the anodization techniques.

Various nanostructures of metal oxide prepared by anodization have been reviewed and are itself a perfect artwork in mesoscale. Also, many nanostructures have exhibited steady, rich and vivid structure colors and give people a very good artistic expression.

This study aims to investigate the effect of different pore diameter and pore length on corrosion properties of anodic aluminum oxide (AAO) film.

AAO layer was produced by two-step anodization aluminum in oxalic acid. The surface morphology was investigated using field emission scanning electron microscopy. The pore diameters were ranging from 25 ± 5 to 65 ± 5 nm and the pore length ranging from 5 to 17 µm. The corrosion properties of the AAO films was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy tests. Corrosion properties and morphology of the anodic films depending on anodization times and pore expansion times were evaluated.

All highlights of this work can be summarized with the following specified below: more treatment with the protective barrier layer of the solution as the pore diameter increases depends on the morphology of the nanotube structured AAO layer. The excellent corrosion resistance renders AAO films without pore expansion very promising. The oxide layer thickness does not affect the corrosion resistance. The better corrosion resistance of AAO films at low pore length can be ascribed to the barrier layer thickness and the more homogeneous structure. The presence of defects for the higher pore length decreases its corrosion resistance.

The AAO films were fabricated by a two-step anodization method in oxalic acid. The anodization times and pore expansion times affect the corrosion performance. The AAO film without pore expansion has good corrosion resistance. The corrosion resistance decreases as the pore length increases.

Investigations of material parameters within the system Al, Al₂O₃, Ta, Ta₂O₅ and TaO_xN_1‐x are presented. This combination is characteristic when using Al sheet for production of substrates including electronic interconnections, vias and resistive groups. They can serve for MCMs due to the specific features of Al. The technological process includes first electrochemical oxidation of Al‐sheet as base isolation layer Al₂O₃ (50‐70μm). This process is followed by vacuum deposition of relatively thick layers of Al (2‐5μm). Each layer is then processed by lithographic methods followed by selective electro‐chemical oxidation as a help process for structuring. The development of this combined structuring method allows the simultaneous achievement of interconnections (Al) and isolation (Al₂O₃) levels with least size up to 50μm. The importance of the method consists of a vertical combination of several conductive layers of Al structured as described above, “burying” the interconnections in the insulating Al₂O₃ films. All necessary combinations and configurations of different kinds of microstrip lines are possible. The dielectric characteristics of Al₂O₃, achieved through the above mentioned method, can be changed in accordance with the parameters of the technological steps and filling of the porous structure. Thus some interesting high frequency features of microstrips are obtained. Extra advantage is the ability of combination of conductive Al layers with other types of such layers as tantalum (Ta). With Ta can be achieved other permittivity constants of the insulation layers and in combination with TaO_xN_1‐x intermediate planes of resistive groups are developed. The measurement of the stripline parameters is done by microwave technics, because the desired application of the substrates is for high‐speed digital signals in the GHz range.

This paper aims to study the anodization of aluminum in a mixture solution of 1,3-propanediol solutions and 0.4 mol l⁻¹ H₃PO₄ at a low temperature.

The morphology and composition of the resulting anodic aluminum oxide (AAO) template was characterized by means of a scanning electron microscope in combination with an energy dispersive spectrometer.

Pore density and pore diameter both were found to be dependent on the temperature of anodization.

The resulting AAO templates exhibited uniform and regular pores with diameters that were significantly smaller than those found in AAO templates anodized at room temperature.

The purpose of this paper is to use a wear test to determine the effect of sand on the wear rates of materials typically used in aerospace applications. Once a repeatable wear test has been established, it can be used to test any combination of materials or coatings. The effectiveness of several different test methods will also be evaluated, including the sample height, surface roughness and mass difference. In addition, the current work will observe the differences between applying sand before the samples are brought into contact or after. The wear rates obtained from these tests could also be used to predict the wear of other components in similar abrasive particulate environments.

A modified block-on-flat wear test of anodized aluminum on hard coat anodized aluminum was used to study this. The experiments were performed with and without sand to study the effects of the sand. Two methods of adding sand were also evaluated. Weighing and profilometry were used to study the differences between the tests.

Wear rates have been calculated based on both the change in the masses of the samples and the change in the height between the upper and lower samples over the course of each test. The wear rates from the change in the masses are repeatable with and without sand, but the results for the change in height show no repeatability without sand. In addition, only in the presence of sand do the trends for the two methods agree. The wear rate was found to be non-linear as a function of load and therefore not in agreement with Archard’s Wear Law. The wear rate also increased significantly when sand was present in the contact for the duration of the test. The sand appears to change the wear mechanism from an adhesive to an abrasive mechanism. Black wear particles formed both when there was sand and when there was not sand. The source of these particles has been investigated but not determined.

This work has not been previously published and is the original work of the authors.

The electrodeposition of any metal over titanium substrates meets with many problems due to the formation of a non‐conductive layer of titanium oxide on the surface of substrates during the electroplating process. Trials were made to overcome these problems by the pre‐anodisation of titanium substrates in oxalic acid solution of concentration 100g/l, at high current density of 60‐95mA/cm^–2, and at ambient temperature. In these conditions, a thin, porous and conductive titanium oxide film can be obtained, which will then support electroplating processes. Rhodium metal was electrodeposited over the anodised titanium substrates from a bath consisting of Rh₂(SO₄)₃, 5.2g/l and H₂SO₄, 100g/l. At optimum conditions of electroplating, the rhodium electrodeposits were formed over the anodised titanium substrate with high adhesion, brightness and high current efficiency (92.05 per cent).

The purpose of this paper is to investigate and explain thermal oxide effect on electrochemical corrosion resistance anodized stainless steel (SS).

Electrochemical corrosion resistance of thermal oxides produced on anodized 304 SS in air at 350°C, 550°C, 750°C and 950°C in 3.5 wt.% NaCl solution have been investigated by dynamic potential polarization, EIS and double-loop dynamic polarization. Anodized 304 SS were obtained by anodization at the constant density of 1.4 mA.cm^-2 in the solution containing 28.0 g.L^-1H₃PO₄, 20.0 g.L-1C₆H₈O₇, 200.0 g.L^-1H₂O₂ at 70°C for 50 min. SEM and EDS had been also used to characterize the thermal oxides and passive oxide.

Interestingly, anodized 304SS with thermal oxide produced at 350°C displayed more electrochemical corrosion and pitting resistance than anodized 304 SS only with passive oxide, as related to the formation of oxide film with higher chromium to iron ratio. Whereas, anodized 304SS with thermal oxide formed at 950°C shows the worse electrochemical corrosion and pitting resistance among those formed at the high temperatures due to thermal oxide with least compact.

When thermally oxidized in the range of 350°C–950°C, electrochemical corrosion and pitting corrosion resistance of anodized 304 SS decrease with the increase of temperature due to less compactness, more defects of thermal oxide.

Recent progress in the investigation of the material parameters of Al/Al₂O₃systems leads to an increase in the possibilities for using embedded TaO_XN_1‐X layers. The use of Al‐sheets as mechanical strength carriers in combination with vacuum‐deposited Al‐layers and electrochemically anodized Al₂O₃ structure requires study. This was found to create a periodic multilayer Al/Al₂O₃ structure. The material qualities of this system allow optimization in order to achieve high speed data processing and signal propagation. The existing studies using Al and Ta combination as well as the high resistance qualities of the modified TaO_XN_1‐X layers have shown satisfactory results. It can be concluded that the development of this new layer combination is possible in the multilayer carrier structures. Some preliminary research studies show a proper adhesion and satisfactory characteristics of the two integrated resistive planes in the multilayer combination Al/Al₂O₃//TaO_XN_1‐X/Ta₂O₅/Al.

In this paper we present recent studies on the electrochemical migration processes in Ag thin film parallel microstrip lines in MCM(D) structures. The basic concept is applying accelerated local drop‐test of water solutions onto the surface of two adjacent lines, under a given voltage potential. These operational conditions are often met in the interconnection line buses, placed in the top assembly level of multilayered hybrid structures. The subject of investigations are MCM(D) developed on Al‐sheet carrier with internal conducting and isolating layers, produced through unique selective electrochemical anodization of Al and Ta. This technology process also enables the creation of embedded R and C passive components on the base of TaO_xN_1‐x and Ta₂O₅ (or Al₂O₃) respectively. We propose an electrochemical deposition of Ag/Sb alloys on the surface of Al interconnection lines and contact pads to ease the bondability and solderability in chip mounting procedures. The artificially created silver migrated defects and partial shorts are investigated through the high frequency method of coupled transmission lines in order to eliminate the errors and insufficient validity of DC direct measurements.

In this article a resume is given of the principal obsevations made during the course of exposure in a natural atmosphere during some twenty years, while choosing the most characteristic examples. The following points will be examined: Resistance to spray and mist of aluminium‐magnesium, aluminium‐magnesium‐silicon, aluminium‐ zinc‐magnesium, and aluminium‐copper magnesium rolled alloys, and of cast alloys; Behaviour of welds, and of contacts with steel and cement; Behaviour during immersion in the sea, and corrosion by differential aeration; Protection by anodisation. These observations have been made during exposure at the experimental stations of the Pechiney Group, in marine atmospheres at Salin‐de‐Giraud (Mediterranean), Saint‐Jean‐de‐Luz, Biarritz and Ostend, and in an industrial atmosphere at Aubervilliers.