A determination was made of the conditions favorable to the deposition and diffusion of Si3N4 on SKD11 steel substrates by means of an inductively coupled, externally heated plasma discharge and a push-pull Hartley RF (13.56-MHz) oscillator using a triode and having a maximum output of 70W was disigned. The reactive gases NH3 and SiN4 were diluted with Ar to a prescribed concentration. Test pieces of SKD11 measuring 5×5×0.5mm were prepared, thier surfaced were polished using diamond paste, and the Si3N4 was deposited onto the surface. By means of experiments based on a method using orthogonal table L27, it was found that the optimum distance between the test pieces and the oscillator electrode was 25cm, and the optimum ratio between NH3 and SiH4 was 1:2.5 at 1073K. The relationship between the distance between the test pieces and the oscillator electrode and the reaction temperature was 5% significant for the thickness of the diffusion layer. Investigation of the apparent activation enerty of the growth of the diffusion layer of Si3N4 yielded a value of 78.7kJ/mol at 1023K-1073K.
Magnesium naphthalocyanine (MgNc) was prepared through two different routes, i.e., from 2, 3-dicyanonaphthalene and Mg in alpha-chloronaphthalene (MgNc-a) and from diiminobenzo-isoindoline and magnesium acetate in tetralin (MgNc-b) and vacuum evaporated onto glass plates. The evaporated films were then examined spectroscopically. The results were: (1) Q band spectra differed with the source of MgNc; specifically the spectra of MgNc-a varied slightly for each deposited film. (2) Absorption maxima of MgNc-a films were at 780nm and 720nm, the former for amorphous MgNc and the latter for crystalline. (3) MgNc-a tends to be amorphous because of the axial ligation of alpha-chloronaphthalene. (4) Alpha-chloronaphthalene splits off MgNc when the film is heated to the transition point and helps promote the rearrangement of MgNc molecules. MgNc-b does not make thermal transition because there are no solvent molecules effective for the relaxation. (5) For effective thermal transition, the vapor deposition of axially ligated Nc is recommended.
Electrodeposition of arsenic has been studied in acidic and alkaline solutions containing As2O3. The current efficiency from the electrodeposition of arsenic was approximately 90% in initial 3 hours but it gradually falled down below 50% after 20 hours. The cathode deposits were metallic grey arsenic at low current densities but was less-conductive powdery arsenic at high current densities. An X-ray analysis indicated that the deposits were non-crystalline. Cathodic hydrogen evolution on the electrodeposited arsenic in an acidic solution obeyed the Tafel relation with a slope of 0.12V/decade in a limited range of current densities and the exchange current density for hydrogen was in the order of 10-3 A m-2. It was also found that the arsenic electrode was slowly reduced to arsine (AsH3) during the cathodic polarization experiment. The anodic polarization curves for the arsenic exhibited a Tafel line with a slope of 0.06V/decade.
The oxygen content of the baths and the magnetic field during electrolysis had an effect on electrodeposition and anodic dissolution by the cathodic and anodic polarization curves and current efficiencies measurement. The oxygen content of the bath was small relative to the cathodic reaction. The magnetic field had no effect on the rate-determining step, but increased the charge transfer current in both cathodic and anodic reactions. The effect on the crystal orientation of the electrodeposits and surface after anodic dissolution in pulse electrolysis were small. Cathodic efficiency increased, and anodic efficiency decreased over 0.5mol·dm-3 CuSO4 solution by magnetic field effects. The magnetic field effects could not explained by Lorentz force, and it is concluded that it was effected by natural convection currents occuring due to concentration gradient. When using the effects of magnetic fields in pulse electrolysis, it is necessary to determine in more detail the concentration of the species in the bath, and the magnetic flux density, as well as on-time, off-time, pulse cycle.
The deposition of copper-zinc alloy (brass) on platinum substrates from pyrophosphate electroplating baths was investigated by potentiostatic electrolysis with respect to the effect of electrode potential on the properties of the alloy deposit. The electrodeposits were analyzed by atomic absorption spectrophotometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis and for their metal element contents by anodic chronoamperometry. It was found that the quantity of electricity obtained by means of anodic chronoamperometry permitted evaluation of the content of metallic copper and zinc in the alloy deposit, since both dissolved as divalent ions in ammonium nitrate solution. In sodium cyanide solution, however, copper and zinc behaved as monovalent and divalent ions, respectively. Both zinc oxide and zinc hydroxide were always included in alloy deposit obtained at potentials more noble than -1.25V (Ag/AgCl sat. KCl) and were never found at a potential of -1.25V, but at potentials less noble than -1.25V they were included in the alloy deposits again when the deposition current and hydrogen evolution current increased.
IMS-H grit of 35/40 mesh made by Tohmei Diamond Co. was prepared by electrodeposition on the truncated cone face on the top of a pencil-like holder at current densities of 3, 5 and 7A/dm2. Disk specimens made of hard metal were revolved, the grit was fed to the specimen surface, and the surface was ground in a spiral configuration to avoid repeated grinding of the same place. It was found that: 1) The grinding depth is changed both by the small smash of the grit edge and by the elastic deformation of the electrodeposited layer. 2) The current density had a great influence on the total amount of grinding and the grinding velocity, but did not affect the experimental results. 3) Grit retention was influenced by the grinding depth and the current density of electrodeposition.