In order to establish a fundamental interpretation of the etching mechanism, the polarization behavior of several metals in ferric chloride etchant has been investigated using DC polarization. Linear potential sweeps were applied to working electrodes of several metals, having an area of 1cm2, in ferric chloride etchants under static condition. Cyclic voltammograms at different scan rates indicated that the mass transfer processes control the reduction kinetics of ferric ions in the etchant. The steady state polarization curves indicated that the etching reaction was cathodic diffusion controlled. Kinetic parameters-diffusion coefficent, diffusion layer thickness and limiting cathodic currentwere determined by these electrochemical techniques. Since the corrosion current for metal dissolution must be balanced with the limiting cathodic current of ferric ions, the metals were shown to be dissolved at the same corrosion current in the same etchant as long as the above dissolution mechanism was occurred. The fundamental behavior of metal etching was successfully explained in terms of electrochemical reaction processes.
Cyclic oxidation tests of Ni-TiC composite and TiC films formed by reactive ion plating were carried out for ten -5h cycles at 300, 400, 500 and 600°C. The composite films exhibited good oxidation resistance relative to the TiC films. After oxidation the films were examined by X-ray diffraction, electron microprobe and Auger analyses. The results indicated that the good oxidation resistance of the Ni-TiC composite film at 300 and 400°C is attributable to a continuous, protective NiO layer formed on the surface of the film. As a result of this good oxidation resistance, the Ni-TiC films exhibited high hardness (Hv 1500) even after the oxidation tests, while the TiC films changed into titanium oxide with low hardness during the tests.
The surface composition depth profiles, chemical bonding and structure of a nitride layer in vanadium implanted with high doses of nitrogen ions were investigated. Nitrogen ions (N2++N+) were implanted into polycrystalline vanadium sheets in the dosage range of 3×1017∼1×1018 ions cm-2 at an accelerating voltage of 90kV. The implanted layers were characterized by means of Auger electron spectroscopy (AES), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Futhermore, the effect of the implantation on the embrittlement of cathodically hydrogen-charged vanadium was evaluated by measuring the formation of hydride. The formation of VN0.35 (bct) and VN (fcc) was found. The nitride composition changed continuously depending on the fluence level of the nitrogen ions and the depth from the surface. Composition changes were evaluated not only by the binding energy shift, but also by the full width of the half maximum (FWHM) of the XPS. The hydrogen absorption inhibiting effect of the nitride thin film was considered to be great. A dose of 5×1017 ions cm-2 was required to obtain the maximum hardness. When the fluence level exceeded its critical value, blisters appeared on the surface layer. High dose nitrogen ion implantation not only modifies nitride layer composition and the surface hardness, but also somewhat affects the surface topography.
Many studies have recently been made on alloy systems for the preparation of amorphous alloy films by plating method and on their applications, but few have been conducted to prepare electroplated amorphous alloy films in which boron is codeposited. The authors have previously studied and reported on the plating conditions of electroplated amorphous Ni-B alloy films from an electrolytic bath that includes trimethylamineborane (CH3)3NBH3. This study is intended to consider the effect of heat treatment on the crystal structure and hardness of electroplated amorphous Ni-B alloy films and to compare their crystal structure and hardness with those of electroplated Ni-P alloy films. Electroplated Ni-B alloy films are amorphous at boron contents of approximately 5wt.% or more. Analysis of the amorphous Ni-B alloy film by X-ray diffraction pattern analysis and differential scanning calorimetry (DSC) indicated that Ni-B alloy films with boron contents of 4.22wt.% or less had a different phase transition process from those with a boron content of 5.38wt.%. The effect of heat treatment on hardness was such that the hardness of the Ni-B alloy film was maximum at approximately 300°C, while that of the electroplated Ni-P alloy film was maximized at approximately 380°C; the former was higher than the latter.
Generally, a barrier-type film of anodized aluminum is formed in baths of neutral salts (ammonium carbonate or ammonium borate), but a porous-type anodized film was formed in ammonium carbonate or ammonium borate baths through the addition of ammonium fluoride. In this paper the effect of carbonic acid derivatives and acid amides on aluminum anodizing were investigated in ammonium carbonate (carbonate-fluoride) baths and ammonium borate (borate-fluoride) baths containing ammonium fluoride. During the anodizing of aluminum in baths containing carbonic acid derivatives or acid amides, bath voltage decreased and uniform films were formed but nonuniform films were obtained in the baths without these additives. Anodizing in a borate-fluoride bath containing ammonium carbamate ((NH4)2O·5B2O3 0.1mol/L, NH4F 0.2mol/L, NH2COONH4 0.1mol/L) for 30min at 20°C with a current density of 2A/dm2 yielded the thickest (about 16μm) and most uniform films. These films also had high grade hardness and corrosion resistance. SEM observation of the film surface and cross-sections proved that the film formed in carbonate-fluoride baths and borate-fluoride baths containing carbonic acid derivatives and acid amides had larger pores (500∼700Å) and cells than films formed in sulfuric acid baths. Cracks formed by partial dissolution of cells were observed on the upper parts of the films formed in carbonatefluoride baths containing formamide, acetamide, or urea.
Chemical vapor deposition of Al2O3 thin films on the microporous structure of anodic aluminum oxide films formed in oxalic acid solutions was examined for the purpose of surface treatment and control of the pore size of the films. Thermal decomposition of aluminum triisopropoxide (ATI) in a infrared irradiation chamber resulted in a homogeneous thin film of Al2O3. The CVD Al2O3 was deposited preferentially at the edge of the porous structure of the aluminum anodic films at an early stage of the CVD treatment. Al2O3 growth proceeded uniformly, and pore sealing was completed. CVD treatment of the anodic aluminum oxide did not cause cracks below 300°C and resulted in a uniform sealing layer at the surface. Changes in the surface morphology of the anodic alumina in the course of the CVD treatment were examined with a scanning electron microscope and the manner of the deposition of the Al2O3 film on the porous structure was discussed.