Electrodeposition of Ni-Fe-Mo-W Alloys - Part 3
3rd Quarterly Report - AESF Research Project #R-117
This paper was submitted to NASF and the AESF Foundation Research Board in October 2013 as a 3rd-quarter report of 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 October 2013 as a 3rd-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. A part of this work was also supported by the National Science Foundation, CHE-#0957448.
This third quarterly report follows the work of two of the three students in the lab that have participated in this project: undergraduate senior Matthew Silva, and graduate student Avinash Kola. They have been working on different aspects of the project to address 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. During the third quarter of the project, we have continued work focused on the effect of electrolyte temperature of NiFeMoW alloys, and the influence of adding thiourea to NiW alloys.
NiFeMoW and NiMoW deposition, Matthew Silva, undergraduate student
In the previous quarter, the addition of iron to the Mo, W and Ni electrolyte resulted in a decrease of nickel and molybdate content, but more significantly it induced the codeposition of tungsten in a region where it was not codeposited when the iron ions were not present in the electrolyte. In an electrolyte containing 0.15M nickel sulfate, 0.1M sodium molybdate, 0.1M sodium tungstate, 0.375M sodium citrate, 1.0M boric acid and a pH of 7, and variable amounts of Fe ions, the surface structure changed considerably as depicted in Fig. 1 for deposits at 49.5 mA/cm2. The electrode was a rotating cylinder electrode having a diameter of 0.6 cm and a rotation rate of 500 rpm. At iron sulfate concentrations greater than 0.1M, nodules formed on the deposits. Some of these nodules even had holes within them, indicating regions where gas bubbles adhered.
The current efficiency of this electrolyte has been found to be very low, on the order of 10%. The low current efficiency is attributed, in part to of the lack of ammonium species, such as ammonium hydroxide, that was not added in order to develop a more environmentally-friendly electrolyte.