To prevent the corrosion of palladium-plated ferro-alloy bases for lead frams, the effect of pulse plating on nickel deposits used as the underlayer for palladium-plated layers was investigated. The following results were obtained. (1) For nickel deposition at a current density of 4A/dm2 and a pulse cycle time of 10ms, fine crystal grains and a smooth surface were obtained at a duty cycle of 9%. (2) The nickel underlayers deposited using pulse current at a duty cycle of 9% improved the corrosion resistance of the palladium-plated ferro-alloy bases more than those deposited using smooth DC. These results suggest the feasibility of applying palladium plating to ferro-alloy lead frames.
The structure of the interface between Ti thin films and Si (100) substrates was investigated to discuss film-to-substrate adhesion after two different surface pretreatments. Prior to film deposition, the substrates were pretreated either by conventional Ar ion bombardment or by chemical etching. It was found that chemical pretreatment resulted in greater adhesion than Ar ion bombardment. The results of observation by TEM, EDS, XPS, SIMS, RBS, and AES suggest that differences in the interface structure and adhesion are caused by the Ar atoms incorporated during Ar ion bombardment. When the Ti thin film is deposited onto the Si substrate, these Ar atoms are concentrated around the interface, lowering the adhesion.
It is well known that TiN and TiC films have been used practically as coatings for improving the properties of materials. In this study, a reactive ion plating technique was used to develope new films that combine the advantages of both films. Single-layer films of TiN or TiC, double-layer films of TiN/TiC and triple-layer films of TiN/Ti (C, N)/TiC were deposited, and their wear resistance and adhesion to substrates were evaluated by wear tests and scratch test. The wear test showed that wear resistance was influenced by the top layer in the case of the double-layer films, but by the intermediate layer in the case of the triple-layer films. The results of scratch tests indicated that the adhesion of TiC films to the substrate was strengthened by depositing a Ti (C, N) film as an intermediate layer.
A study of bond strength, reaction layers and the distribution of the elements in the bonding of zirconia and metal by active metal brazing was conduced by means of tensile tests, XRD, EPMA, and SEM. The results showed that there is a maximum value in the relationship between bond strength and titanium foil thickness. The titanium reacted with the oxygen in the zirconia to produce a TiO layer. The thickness of which depended on the thickness of the titanium foil thickness. Thicker foils produces thicker TiO layers containing cracks that resulted in weaker bond strength.
The area of Diamond-like carbon film defects was determined by cathodic polarization. When films cathodically polarized at a potential of -0.8V vs. Ag/AgCl in aerated aqueous Na2SO4 solution, the reduction of oxygen dissolved in the solution took place on the substrate of film defects. The limiting diffusion current of oxygen reduction was proportional to electrode area, so that the area of the film defects could be determined from cathodic current. Although this method is applicable only to insulating films, it has the advantage that it does not damage the substrate. The number, size and distribution of film defects were obtained by Cu electroplating.
Previous studies showed that the electrodeposition from baths consisting of trimethylamineborane and cobalt sulfate using a rotary electrode could yield Ni-Co-B ternary alloy films, and their alloying ratios and crystallographical structures could be controlled by changing the current density. In this study, the authors prepared multilayer films by periodically changing the current density, and investigated their structures and magnetic properties. The results were as follows: 1. In electrodeposition using a rotary electrode, periodic changes in current density and plating time were effective in controlling crystal size and film thickness to the levels required. 2. The films had soft magnetic properties. Controlling the crystallographical structure and thickness of the layers resulted in films with various soft magnetic properties.
Studies were conducted using the double zincate method on the surface morphologies of aluminum substrates at each stage from pretreatment to electroless nickel plating, on the structure of immersion zinc-iron deposits and on the initial deposition process of electroless nickel plating on aluminum. A large number of zinc crystals about 1μm in diameter were deposited by displacement plating after the first zincate stage, and island-like protuberances were observed on the aluminum surface after stripping of the zinc crystals. It was confirmed that zinc crystals were formed on the tops of the protuberances prior to the flat aluminum surface during the second zincate displacement reaction. The zinc crystal formed in both the first and second zincate processes contained about 1wt% of iron. The structure of the initial electroless nickel deposition layer was studied by TEM of cross sections prepared by ultramicrotomy. The presence on the zinc crystal surface of a layer that appeared to be pure nickel, acting as a center of autocatalytic reaction was confirmed.
A high density of etch pits on high purity aluminum foil for electrolytic capacitors is produced by anodic dissolution in hot hydrochloric acid solution. Pit morphology and AC impedance characteristics were investigated under potentiostatic conditions for aluminum foil with (100) crystal orientation in 1mol/dm-3 hydrochloric acid solution at 363K, and the charge transfer resistance Rct, time constant τ0 and reaction uniformity parameter θ were estimated. Increase of anodic potential led to an increase in pit density and tunnel length, and to a decrease in pit size. The value of τ0 has a tendency to increase with time until becoming constant value at 0.4ms, and is independent of etching potential. In the steady state, when regular pits with small size and long tunnel length are made and large surface area are got, the value of τ0 is less than 0.4ms. When τ0 has a large constant value, pits proceed circumferentially around the walls of the pits without any preferred direction. This means that the change in τ0 value corresponds to the change in the morphology of pits formed at various potentials.
The effect of ultrasonic waves on the anodizing of aluminum was studied in terms of synergism in the presence of glass beads. The baths used were sulfuric acid (1∼15w/v%) at 20∼40°C, frequencies of 28∼1000kHz, power outputs of 100∼60W and current densities of 1∼2A/dm2. It was found that the coatings formed under ultrasonic waves were thicker and much harder than those formed without ultrasonic waves. The best results were obtained with a 15w/v% bath at 400kHz and a 1w/v% bath at 28kHz. Dissolution of the coatings in 5∼15w/v% baths by 28∼100kHz ultrasonic waves was also investigated. It is suggested that effects of ultrasonic waves during anodizing were to increasing the dissosiation of aluminum ions and to promote the decomposition of oxygen supplyers (OH-).
Ultrasound power was supplied with hone type at 20kHz, 400W. Process parameters studied were closed steady-state temperature, concentration, pH, sonication time and flow rate. The decomposition of dichloromethane (methylene chloride) was not affected between 300∼340K and pH 3∼9. Dilute methylene chloride in water was rapidly decomposed by ultrasonic irradiation into carbon monoxide and/or carbon dioxide, hydrochloric acid, free chlorine and water at ambient pressure. Decomposition efficiency was about 30% after 2min of sonication and about 50% after 10min of sonication at 25∼100ppm.