This paper, which clarifies effects of Cu ion beam irradiation with a tandem accelerator and an ion implanter on the morphologies of initial pits and on pit growth in high-purity aluminum, describes investigations of direct current (DC) etching and rectangular alternating current (AC) etching in hydrochloric acid solutions. Results of SIMS analysis confirmed that the Cu ion depths in specimens irradiated with the tandem accelerator and the ion implanter were approximately 1 μm at 1.5 MeV, 3 μm at 6 MeV (tandem accelerator), and 0.2 μm at 300 keV (ion implanter), respectively. These depths almost agreed with theoretical values. During DC etching, many facets were produced on the tips of tunnel pits through the zone of Cu ion concentration. The Cu ions in aluminum foils irradiated with the tandem accelerator cause excessive facet dissolution during tunnel pit growth. Plural facets on the cubic pits' side walls were observed in Cu ion irradiated specimens after AC etching. Results suggest that Cu ion irradiation of high-purity aluminum accelerated facet dissolution during the anodic half cycle of AC etching. Consequently, the excessive facet dissolution caused by Cu ions irradiated in aluminum is inferred to prevent pit propagation and extension of horizontal pit growth.
The adhesive ability of diamond film deposited on nitric-acid treated Co-cemented tungsten carbide was evaluated using ultrasonic cavitation tests. Without nitric acid treatment, the diamond film surface roughness is high, but its adhesive ability is quite low. During nitric acid treatment lasting longer than five minutes, Co is eluted from the Co-cemented carbide and fine pores are formed on the surface. The adhesion strength depends on the nitric acid treatment time: strength after treatment for five minutes and over ten minutes is significantly different. Neither the surface morphology nor its chemical composition changed, but ultrasonic microscopy revealed a lowered ultrasonic surface-wave velocity after nitric acid treatment. A deformation layer of 5 μm or less was formed when the substrate was polished. Furthermore, acid-affected layers of 5-18 μm were formed during nitric acid treatment. Longer nitric acid treatment duration yields a thicker acid-affected layer. The low ultrasonic surface-wave velocity indicates that the Co is eluted and that the conjugation between WC particles weakened and that the apparent Young's modulus of the acid affected layer decreased. The layer with the low apparent Young's modulus is thought to absorb the thermal residual stress of CVD diamond deposition. Presumably, the difference in results obtained at five minutes and at more than ten minutes is attributable to their different acid-affected layer thickness.
Adsorption and desorption behaviors of human serum albumin (HSA) on titanium particles were examined as a function of pH. The HSA showed a high affinity-type isotherm with well-defined saturation values, even when HSA had a net charge that was the same type as that of titanium. The saturated amount of HSA adsorbed (Γsat) depended on pH. The maximum value of Γsat was obtained at pH around the apparent point of zero charge of HSA, where the net charge (ZH+app) of HSA was zero and where HSA has the minimum intrinsic viscosity ([η]), reflecting the molecular volume. Results showed that the ZH+app and [η] of HSA are the most important factors determining the Γsat value. Curves for the surface charge density (σapp) of HSA-adsorbed titanium prepared at initial pH 7.4 showed that carboxyl groups on HSA contributed to interactions even with the negatively charged titanium surfaces. The possible interactions between ionic functional groups on HSA and titanium were discussed based on measurements of variation in pH of solutions, i.e., uptake or release of proton (ΔpH) as a result of adsorption. The removal of HSA from titanium surfaces was more rapid when using alkaline solutions, particularly at pH greater than 11. Results showed that HSA was adsorbed onto titanium surfaces, even under unfavorable electrostatic conditions, through various interactions between ionic groups on HSA and surface OH groups on titanium, the magnitude of those interactions was diminished by the OH−cleaning action.
Carbon nitride has fascinating properties such as high hardness, high current density of field emission and so on. To obtain this material, generally CH4 is used as a carbon source. Therefore, to make clear the effects of the reaction gas on the preparation of carbon nitride, we tried to use C2H4 as a carbon source instead of CH4. However, crystalline carbon nitride has not been synthesized from the C2H4-N2 reaction gas system. On the other hand, quality of CVD diamond is improved by O2 addition for diamond growth. So, for the preparation of carbon nitride, H2 addition is expected to be efficient as well as O2 addition for the preparation of CVD diamond. Investigation was carried out on the preparation from the C2H4-N2-H2 reaction gas system using microwave plasma CVD. As a result of SEM observation, crystalline deposits were observed in the condition for H2 flow rate;3∼15 SCCM, C2H4 flow rate;1 SCCM and for H2 flow rate;9∼21 SCCM, C2H4 flow rate;2 SCCM. Morphologies were changed from amorphous to crystalline with increasing H2 flow rate. From AES estimation, peaks of C and N were observed in AES spectra of each sample. From XPS measurement, C-N bond and C=N bond were obtained in XPS spectra of each sample. The chemical bonding state were changed from C-N bonding to C=N bonding with increasing H2 flow rate. In conclusion, morphologies are changed from amorphous to crystalline, and chemical bonding state are changed from C-N bonding to C=N bonding with increasing H2 flow rate.
As described in this paper, using first principles calculation, we calculated the surface energy, which is important information to understand the high-release property. To confirm the accuracy of our calculations, we first calculated the lattice parameters of metal nitride crystals with NaCl structure. The calculated lattice parameters agreed with the experimental values with, at most, 2.7% differences. Next, we calculated the surface energies of TiN, VN, CrN, ZrN, TaN, and NbN crystals. Results showed that the surface energy of CrN(100) was the lowest among (100), (110), and (111) surfaces. Calculation also showed that the surface energy of (100) was lower than that of (110) surface in the other metal nitride crystals. The (100) surface energy of CrN was the lowest among the calculated metal nitride crystals. Furthermore, results showed that the adsorption energy of an O atom on CrN(100) was the lowest among the metal nitride crystals. The results described herein indicate that first principles calculation, which deals with the ideal surface at the atomic scale, can be used to evaluate the surface energy of metal nitride.
Corrosion behaviors of intermetallic compounds FeAl and FeAl(Cr) were investigated. Steady-state polarization curves of FeAl and FeAl(Cr) were measured in solutions of various pH (pH 0-3) containing chloride ions. Protective regions were observed for FeAl(Cr), even in the HCl solutions of pH 0 and 1. Furthermore, FeAl(Cr) showed a self-passive state in solutions of pH 2-7. In contrast, FeAl showed no protective behavior in a pH 0 solution. Its self-passive regions were smaller than those of FeAl(Cr). The passive film formed on FeAl(Cr) immersed in 1 M HCl solution for 432 ks caused a shift in the corrosion potential by about 130 mV to the noble direction. The potential width of the protective region increased from 160 mV to 300 mV. Moreover, a considerable decrease was observed in passive current density: more than one order. The passive current density of FeAl(Cr) after long-term immersion in HCl solution was less than that of SUS316 steel. Results suggest that aluminized steel with a coating layer of FeAl(Cr) and appropriate immersion treatment in HCl solution can show high corrosion resistance comparable to that of conventional stainless steels.