Diamond deposition by a microwave plasma CVD process was observed using substrates of different chemical natures. The reaction gas consisted of CH4 and H2, with the latter supplied at a rate of 100cm3/min, while a pressure of 2.3kPa was maintained in the chamber. The CH4 concentration was set generally at 0.6vol%; the microwave output was at 120W. Diamond formed at high densities on substrates of W, Mo, Ta or Zr, so these materials, pre-scratched, are suitable for a diamond film deposition. In contrast, the deposition occurred at much lower densities on Au, Pt, Cu or Pd, which thus seemed more suitable for a growth of particles. No diamond formed on any of the ferrous metals studied, but the materials, when coated with ceramics, served as good substrates. Cobalt had to be removed from the surface of the cemented carbide or sintered diamond before they could serve well as substrates. By depositing diamond on the mixture particle of amorphous carbon and diamond, it was possible to produce particles which had numerous small edges on the surface and which may find applications as an abrasive material.
Using the vapor of alkylbenzenes such as toluene, ethylbenzene, and n-butylbenzene, having comparatively low saturation pressures, small surface areas could be estimated from the gradient of the linear portion of the Type II adsorption isotherms which were found in many of the solid adsorbents. In this “gradient method”, surface area was obtained from the monolayer volume, which is equated to the gradient values of dv/d(P/Ps), where v is the amount adsorbed and P/Ps is the relative pressure, and from the adsorbate molecular cross-sections calculated from the liquid densities. The surface areas thus obtained agreed, with a precision of ±20%, with the standard N2-BET surface areas for more than 20 solid powder samples. The surface areas for plate-like samples examined, however, were estimated a little larger than the geometrical values, probably because the surface pores of the samples could not completely be removed by surface pretreatment. It was ascertained that this method is useful for the estimation of surface areas, and especially the small areas, not only because the vapor pressures of the alkylbenzenes were low but not too low (e.g., the saturation pressure of n-butylbenzene was 21.3Pa at 0°C), but also because adsorption measurements can easily be carried out at room temperature.
Electrochromic iridium oxide films have been investigated by a periodic reverse current method of electrodeposition using a simple apparatus. The electrochromic iridium oxide films formed by periodic reverse current electrodeposition (PRIROF) were dependent on the chemical structure of the sulfatoiridate complex used as the electrolyte. The most desirable aspect of the chemical structure of the complex is that the sulfate ions are chelatingly coordinated to iridium atoms, and the best results were attained by heating a commercial sulfatoiridate reagent. In electrolysis, the applied potential was reversed from +1350mV to -200mV with a period of 6 sec. Periodic reverse electrolysis contributed to improve the uniformity and promoted the increase of the growth of iridium oxide films. XPS analysis suggests that PRIROFs are more hydrated than anodic iridium oxide films (AIROFs). The films showed blue-black in anodic polarization and transparent in cathodic polarization. They were chemically stable and showed good reversibility. PRIROFs are better than sputtered iridium oxide films (SIROFs) in terms of coloring efficiency in 0.5M H2SO4 solution.
Nickel boride has relatively high hardness, low electrical resistance and high melting point which are properties required of materials for electrical contacts and welding electrodes. It is well known that composite materials composed of metals and borides can be produced by sintering or melting. While sintering involves high cost and difficulty in achieving uniform distribution of the boride, melting has the disadvantage of crystallizing the boride at the solidification of the molten alloy, causing the formation of borides with particles that are too coarse. On immersion of Cu-Ni (5-95wt%) and Cu-Ni (5-50wt%)-M(0.2-10wt%, M: Ti, Si, Cr and Co) alloys in molten borax containing 30wt% B4C at 800-1000°C for 1-16hrs, boron diffused into the copper alloys to form a nickel boride dispersed layer only in the surface portion of copper alloys. Additions of Ti and Si to the copper alloys were effective to form finer boride particles uniformly.
Anodic oxide films formed on aluminum in electrolyte solutions of sulfuric, oxalic, chromic and phosphoric acid were then electrolytically colored in nickel sulfate solution and the coloring behavior was investigated. For films formed at identical voltages in different electrolytes, minimum AC coloring voltage increased with the electrolyte of formation in the order of chromic, phosphoric, sulfuric and oxalic acid solution. For films formed in the same electrolyte, the minimum coloring voltage (Vp) did not increase proportionally to increasing film formation voltage (Vf); rather, the Vp:Vf ratio decreased as Vf increased, except for films formed in oxalic acid. These electrolyte and voltage dependent behaviors on coloring are caused by differences in the nature of barrier layers and are explicable by the flaw density in the barrier layer. The coloring behavior of sulfuric acid films was also studied in electrolyte solutions of copper, cobalt, nickel, ferrous and tin sulfate, and the minimum coloring voltage decreased in that order. The spread of AC coloring voltage broadened in the order of cobalt, tin, ferrous, nickel and copper sulfate solutions.
Boride films were formed on chromium-plated low carbon steel specimens by immersing them into molten KCl-BaCl2-NaF-B2O3-ferroboron salts at 973-1273K for 3.6-10.8ks. X-ray analysis showed that CrB2 was formed in the case, and the formation of the film was confirmed by microscopic observation and EPMA analysis. The CrB2 layer had high hardness (about 2500 Vickers) and high wear resistance. The amount of CrB2 produced depended on immersion time and temperature, as well as on the amount of NaF, B2O3 and ferroboron added to the melt. This suggests that CrB2 was formed through the following disproportionation reaction: 2B3++B(in ferroboron)→3B2+……(1) 6B2++Cr(on specimen)→CrB2+4B3+……(2)