Heating causes the hardness of Ni-P plated films to increase, reach a maximum, and then decrease. This phenomenon is also observed in nickel films of low phosphorus content deposited from nickel sulfamate-hypophos-phorous acid solutions. To explain the hardness with heating, the peak profiles of X-ray diffraction patterns were analyzed, and the crystal grain size and residual internal strain were calculated. The relationships between these and hardness change were discussed. Films deposited from baths containing nickel sulfamate and 0 to 2.5g/L hypophosphorus acid were heat treated up to 450°C. Nickel crystal grain size in the (100) direction and residual internal strain were calculated from the Ni(111) and Ni(200) peak profiles obtained by X-ray diffraction. TEM observation was also conducted. It was found that 1) The hardness of nickel films containing phosphorus is based on the solid solution effect of phosphorus, and it increases with phosphorus content; 2) The change in hardness with heating is caused by segregation of phosphorus as the pre-stage of Ni3P precipitation; 3) The decrease in hardness at higher temperatures is caused by recrystallization and by stress release with Ni3P precipitation.
Ni-P electroplating is widly used as a corrosion prevention technique, but the fact that the high corrosion resistance of Ni-P film is due to its amorphous structure is not well known. A detailed investingation was therefore conducted on the process by which the film become amorphous as more and more P is added. Electroplated Ni film is crystalline, with a prefered orientation of 220. When 5 at % P is mixed into this Ni film, the orientation is changed to 111 and the crystals in the film assume an elliptical or columnular shape about 50Å in diameter and 100Å or less in length, perpendicular to the surface of the film. When the concentration of P reaches about 10 at%, the crystals assume a needle shape, and at higher P concentrations, the needle length decreases and the film becomes amorphous. It is concluded that the direct cause of the amorphous structure of the film is P concentration, not multiple nucleation. It further seems that the amorphous formation is related to the adsoption of P atoms to Ni atom and to the obstruction of nucleation and grain growth-What we term the theory of obstruction of nucleation or obstruction of grain growth.
Ni-Fe-P alloys were electrodeposited in Watts' type nickel baths containing ferrous chloride and phosphonic acids. The Ni and P content of the alloys increased with increasing current density or increasing phosphonic acid concentration, whereas the Fe content decreased with increasing P content. The X-ray diffraction intensity of the alloys was progressively lowered by increasing the P content. Alloys containing more than 8.0% P were substantially amorphous. It seems that plating baths of low Ni2+ concentration are preferable for obtaining amorphous Ni-Fe-P alloys. The anodic polarization curves for electrodeposited amorphous Ni-Fe-P alloys in 0.1N sulfuric acid did not exhibit passivity, but the alloys were much more highly corrosion resistant than crystalline Ni-Fe alloys.
Comparative tests of the Vickers hardness and Knoop hardness of amorphous plating films were made using standard hardness blocks and a microhardness tester. It was found that there were differences in the interrelationship between the HV and HK values, depending on the standard blocks used and the films tested. Accordingly the configurations of cross sections were compared to elucidate differences in load dependence and the interrelationship between HV and HK values related to whether the strucutre was crystalline or amorphous. An investigation was also made of the changes in the hardness of amorphous Ni-P films with heat treatment.
SiC composite Ni-P alloys were electrodeposited from normal Watt's type baths in which 20-160g/L SiC powder was suspended. The SiC particles were easily codeposited using baths containing H3PO3. Uniformity of the particle dispersion in the deposit, and the soundness of the interface between SiC and the amorphous Ni-P matrix were examined by scanning and transmission electron microscopes. The thermal stability of the amorphous Ni-P matrix in the composite alloys was studied by differential scanning calorimetry. Vickers hardness tests were also done to study the effects of SiC content and heat treatment. It was found that 1) Composite Ni-P-SiC alloys containing 3.5-7.2wt%SiC were obtained by suspending 20-160g/L SiC in the electrolytic bath; 2) The crystallization temperature of the amorphous matrix decreased with an increase in SiC content; 3) The hardness of the amorphous Ni-P deposites tended to increase slightly with an increase in SiC content. These deposits hardened greatly after being heat treated up to 450°C.
Because of the importance, from the engineering point of view of evaluating brittleness, a study was undertaken on critical stress (Pf) and critical strain (df) in the relation between load (stress) and the size of the pyramidal hole (strain) under microplastic deformation of brittle Ni-S alloys. Deformation energy (Ef) on fracture was also evaluated. Brittle Ni-S alloys were prepared by electroplating on Cu sheet (current density=60A/m2, distance between electrodes=40mm, pH=6.0, bath temperature=303K). The concentration of the water solutions were 100g/L for NiSO4(NH4)2SO4·6H2O, 15g/L for Na3C6H5O7·2H2O, and 1∼30g/L for Na2S2O3·5H2O. Ni-S alloy composition was varied by controlling the concentration of Na2S2O3. Precise evaluations of fractures were preformed with a Vickers microhardness tester. The addition of sulfur was found to decrease resistance to microplastic deformation (Po), however the higher the sulfer concentration, the lower were the values of Ef, df, and Pf become. Comparing values of Ef, the brittleness of Ni-S alloys was found to approximate the values obtained for Al2O3 and slide glasses.
Computer simulation of Co82 Gd18 film deposition on a planer substrate has been conducted to elucidate the process of film formation by sputtering. In the simulation, Co and Gd atoms were taken to be Lennard-Jones particles having atomic diameters of 2.50Å and 3.40Å, respectively. Five film formation processes were simulated, and the resultant strucure factors of the 305-atom deposits were compared with an experimental reduced interference function F(k) and a reduced radial distribution function G(r). Among the five structures obtained, only one reproduced the experimental F(k) and G(r) with fair accuracy. In the simulated deposition of this model, Co-Co as well as Co-Gd atom pairs has been formed and deposited on the surface.
Electrodeposited Fe-Cr alloys show amorphous structure and better corrosion resistance when the Cr content of the films is more than 30wt%. Research with controlled plating conditions-e.g. bath pH, current density and bath composition-have been performed and the alloys are definitely introdeced to show how these factors affect the amorphous sturcture of the deposited films. In addition, by taking the results of electrochemical measurement into account, some difference in corrosion between amorphous and crystalline Fe-Cr alloys have been recognized. The amorphous structure was observed to be passivated in 0.1N H2SO4 solution.
The conditions for the preparation of Fe-Mo, Co-Mo, and Ni-Mo amorphous alloys by an electroplating technique were investigated. Mo is deposited as alloys when the iron family transition metal is in the plating solution, and when the concentration of Mo in the deposited film exceeds a certain limit the deposited alloy film becomes amorphous. The range of Mo concentrations required to produce an amorphous structure is 10∼55 at% Mo for Fe, 15∼55 at% Mo for Co, and 30∼75 at% Mo for Ni, but these ranges may be wider under certain circumstances. The most important condition for preparing amorphous alloys by electroplating is apart from plating temperature, not in the plating conditions, but in the composition of the deposited alloy, which is approximately the range in which intermetallic compounds are formed.
The retarding effect (RE) of various organic reagents on the reaction beween 1, 1, 1-trichloroethane (CCl3·CH3) and aluminum was investigated by measuring the induction period of the reaction. In the previous paper, it was confirmed that the RE of compounds having two functional groups increased 5-100 times over that of compounds having one functional group. However, contrary to expectation, some dihydric and trihydric phenols, diamides and imides, which do not dissolve in CCl3CH3, had no effect of RE. In this paper, we tried to dissolve these insoluble organic reagents in CCl3CH3 by adding a solvent, and then examined whether these organic reagents had a large RE or not. The results are summarized as follows: 1) polyphenols (1, 3-dihydroxybenzene and 1, 3, 5-trihydroxybenzene and 1, 2, 3-trihydroxybenzene), diamides (succinic acid diamide and phthalic acid diamide) and imides (succinimide and phthalimide) could be dissolved in CCl3CH3 by using ethyl alcohol or acetone as a solvent. The RE of these organic reagents was found to be extremely large. 2) when two species of soluble organic reagents having different functional group were added in CCl3CH3, the RE was larger than that of one species, but smaller than that of other species. The synergistic action, that is, the phenomenon that the RE when two species of organic reagents were used simultaneously becomes larger than those of respective reagents, was not observed. Accordingly, when an insoluble organic reagent and a solvent were also added simultaneously, it is concluded that there was no synergistic action.
Isotachophoresis was applied to the quantitative analysis of phosphorus in Ni-P and Co-P alloy deposits, thereby increasing the speeding of analysis. Sample fimls were dissolved in a solution of 40%HNO3 and the solution was demineralized by electrodialysis using an ion-exchange membranes. This pretreatment redurced the timer equired for analysis to less than 1 hour. Isotachophoresis resulted in higher accuracy and reproducibility than could be obtained with other analytical methods, and it is also applicable to the analysis of boron in such alloy deposit films.
Anodic oxidation of electrodeposited Co in alkaline solutions was investigated to improve the coercivity of thin films in the potential range where Co(OH)2 might form. The coercivity of the Co film was increased extensively by anodic oxidation. This is attributed to the isolation of individual Co particle caused by the formation of hydroxide at the grain boundaries.
Electroless plating of Pd-P alloys from palladium-ethylenediamine complex solutions containing sodium hypophosphite as a reducing agent, was investigated. The deposition rate of Pd-P alloys was markedly influenced by the concentration of palladium chloride and bath temperature. The phosphorus content of deposits was proportional to the 0.2 power of sodium hypophosphite concentration. In Pd-P alloys, the amorphous solid was converted with heat treatment at 250-300°C into either stable crystal phase Pd plus Pd8P or Pd plus Pd6P, according to phosphorus content. It was found that hardness increased when heat treatment of the alloy resulted in the formation of PdxP crystals.
Ni-P eutectic alloy film as an insert metal is successfully applied in joining clad pipes, and continuous electroplating technology was examined to plate Ni-P alloy on long metal foil for this application. Watts baths to which phosphorus acid had been added were found to be stable for continuous plating. Film composition can be easily maintained by using a soluble Ni anode and adding phosphorous acid.