Electrodeposition of Ni-Fe-Mo-W Alloys - Part 2
2nd Quarterly Report - AESF Research Project #R-117
by E.J. Podlaha-Murphy, Professor of Chemical Engineering, Northeastern University
Editor's Note: This paper was submitted to NASF and the AESF Foundation Research Board in July 2013 as a 2nd-quarter report of AESF Research Project #R-117. A printable PDF version is available by clicking HERE.
This NASF-AESF Foundation research project addresses the induced codeposition of molybdenum and tungsten alloys with nickel and iron with a focus on developing a toolbox of plating conditions to deposit different combinations of Ni, Fe, Mo and W. The experimental approach utilizes electrodes with a controlled hydrodynamic environment, since it has been noted by the project director that the reduction mechanism can involve a coupled kinetic-mass transport behavior. The project was initiated in January 2013.
This second report follows the work of three students in the lab: undergraduate senior Matthew Silva, graduate student Shaopeng Sun and graduate student Avinash Kola. During the second quarter of the project, we have continued work focused on the effect of electrolyte temperature of NiMoW alloys, the influence of adding Fe(II) to the system, pulse plating of the NiMoW alloys and developing correlations to compare the conventional Hull cell with a rotating Hull cell.
Matthew E. Silva, undergraduate senior in chemical engineering
Mathew Silva started working in our lab in spring 2013 for course credit and has continued for the summer as a temporary employee. He has surveyed conditions of NiMoW at different electrolyte temperatures over a wide range of current densities employing a rotating Hull cell. From the 1st quarter report, rotating Hull cell (RCH) experiments at 500 rpm were conducted for three average applied current densities (1.0, 2.0 and 3.0 A) and three temperatures (room temperature, 40°C and 60°C). The electrolyte contained 0.15M nickel sulfate, 0.1M sodium tungstate, 0.1M sodium molybdate, 0.375M sodium citrate, and 1.0M boric acid. The pH was adjusted with dilute sulfuric acid or potassium hydroxide to maintain a value of 7.0 ± 0.3. At an applied average current density of 66.3 mA/cm2, there was an effect of temperature on where the deposit formed along the electrode and on the deposit appearance. At lower temperatures, the deposit occurred over a broader distribution, while at higher temperatures, there was an apparent shift in the deposit to the higher current density regions. Figure 1 shows the deposit surface by SEM of two regions on the rotating Hull cell at three temperatures near a high current density region, ~ 120 mA/cm2 and a low current density region, ~ 60 mA/cm2, where a metallic deposit occurs. At high current densities, nodules are observed which are reduced in size with increasing temperature. At low current densities there is an increase in microcracking with increasing temperature.