Crystal growth in a microwave plasma CVD was studied using as seeds crystalline diamond particles produced by an HP-HT technique. Reaction pressure and hydrogen gas flow rate were fixed at 3.3kPa and 2.8cm3/s, respectively, while the methane concentration and reaction duration were variable. A microwave power of 220W was used for most of the runs. Results were evaluated in terms of increase in linear grain dimension. The growth rate reached a maximum at a microwave power of around 220W (1170K estimated) and a methane concentration of about 5.4%. There was a tendency for growth rate to be high in the early stage and to decrease as the process went on, with larger seeds growing more slowly. It was also observed that the growth rate was significantly affected by the surface condition in the early stage. Based on observation of deposited particles and analysis by X-ray diffraction and Raman spectroscopy, methane concentrations not exceeding 1.0% are necessary for producing idiomorphic diamond crystals. Specifically, at concentrations higher than 1.8%, the product was round, with amorphous carbon co-deposited.
Diamond was synthesized by microwave plasma CVD from CH4-H2 based mixed gases containing varying proportions of either O2, CO2 or CO as an additive. H2 flow rate and CH4 concentration were fixed at 1.67cm3/s and 3.0% respectively and microwave power was 220W. Addition of minute amounts of all of the additives resulted in increasing deposition rate. O2 and CO2 were effective in improving the morphology, while CO had no appreciable effect. CO2 was found most effective in both increasing the deposition rate and improving the morphology. An increased concentration of O2 or CO2 resulted in more idiomorphic diamond crystals with less secondary growth on the surface. The effectiveness of CO2 addition in improving both deposition rate and morphology of diamond is thought to be due to the increase in both carbon and oxygen concentration in the reaction gas system. Amorphous carbon would be eliminated by active oxygen in the plasma, and methyl radical, an intermediate product on the way to diamond, would be formed. Raman spectroscopy is especially effective in evaluating amorphous carbon.
It was found that bright tin deposits were obtained by addition of polyoxyethyleneglycol (PEG) and formaldehyde to pyrophosphate baths containing SnSO4 and K4P2O7. The optimum bath composition and operating condition for bright tin plating were SnSO4 0.2M, K4P2O70.5M, PEG (average molecular weight 3000) 1.0g/L, formaldehyde 0.6mL/L, pH7-9, bath temperature 50°C, and current density 10-20mA/cm2. Cathode current efficiency was over 80% at current densities between 5 and 20mA/cm2, and decreased with increasing concentrations of formaldehyde and K4P2O7. The addition of PEG to an additive-free bath shifted the cathodic polarization curve to a less-noble potential and yielded fine-grained deposits. The addition of formaldehyde to baths containing PEG shifted the polarization curve to a more-noble potential and yielded bright tin deposits. It was concluded that in the electrodeposition of tin from pyrophosphate baths, formaldehyde results in the suppression of the adsorption of PEG on the tin surface and contributes to the brighting of tin deposits only in the presence of PEG.
Hot hardness and dilation curves were measured and the associated X-ray studies were conducted on electroplated Ni-W alloys of 40, 44 and 51wt%W during heating at a rate of 1°C/min. The increase in hot hardness started at around 200°C, and softening began at about 600°C. The 44wt%W alloy showed the highest hot hardness-Hv900-between 450°C and 550°C. Along with such well known Ni-W crystals as face centered cubic solid solution, Ni4W and nearly pure tungsten, a new phase was found to be precipitated. For example in 40wt%W alloy, the new phase had a body centered tetragonal structure with a=9.136Å and c=10.268Å±0.038Å, having 74 or more atoms of anomalously small atomic volume in a giant unit cell. Although the new phase appeared first on heating, it was fairly thermally stable and was the predominant precipitate at the peak hardness of the alloys. The origin of the formation of the new phase is discussed, and the precipitation of pure tungsten which was found on heating the 40 and 44wt%W alloys, was experimentally analyzed.
A method of assaying gelatin in acidic copper plating baths was investigated, and gelatin content was determined indirectly in the following way. Only the gelatin in the electrolyte was bounded with a nitrocellulose (NC) filter, and the gelatin on the NC filter was allowed to react with Amido Black 10B (AB10). The AB10 was then eluted with a NaOH solution, and the absorbancy of the AB10 solution was measured. Gelatin in concentration up to 16ppm were determined without the influence of coexistent ions. The decomposition behavior of gelatin in the electrolyte was investigated. The molecular weight of the decomposed gelatin was determined by the gel permeation chromatography, after the gelatin combined with the NC filter was eluted with a surfactant. It appeared that the gelatin decomposes with time, and that the decomposition rate is faster at higher temperatures. After standing for 240min, gelatin with a molecular weight of 70, 000 broke down to molecular weight of 25, 000, 15, 000, and 5, 000 at 32°C, 45°C, and 60°C, respectively.
The extraneous deposition of electroless Ni-W-P alloy films on the transparent electrode was investigated. A degreasing process suppressed thick extraneous deposition, while low concentrations of dissolved oxygen resulted in granular extraneous deposition which was affected by the size of the substrate and the orientation of the pattern. The composition of the granular extraneous deposits was almost the same as that of normal deposition, except it was slightly richer in phosphorus and poorer in nickel. The occurrence of granular extraneous deposition was closely related with the amount of adsorption hydrogen, which was reduced by the higher concentration of dissolved oxygen and by stirring.
The GA process for descaling hot rolled stainless steel is proposed, in which ammonium chloride vapor is introduced soon after annealing, reacting at high temperature with only the surface of the steel though use of the heat held in the steel, without damage to equipment composing materials. Fundamental studies of the GA process were conducted to comfirm of its descaling effect, with the following results: 1. By comfirmig GA treatment with bending and brushing, it was possible to reduce descaling times for SUS 430 steel by acid cleaning using the ordinary HNO3-HF mixture to 10 seconds. In comparison with descaling times by bending only of 30∼50 seconds, this represented a time saving of 1/5∼1/3. 2. It was comfirmed that the hydrogen chloride and chlorine generated in GA treatment produced by the thermal decomposition of ammonium chloride and ferric chloride affected the scale, and changed the properties of the scale to acid soluble and mechanically frangible. 3. Problems still remain in terms of optimum GA process conditions for Austenite stainless steels snd systems for by-product recovery, but the process are judged to be practicable in principle.
TiNx films (N/Tiratio=1.09∼0.8) were ion-plated onto silicon wafers, and comparisons were made between their residual stresses as determined by substrate deflection and X-ray stress measurment. Maximum compressive-stress was obtained at an N/Ti ratio of 1 by the former method, and at ratios lower than 1 for the latter.