Mesoscale structure in electrodeposited nanocrystalline Ni–Fe alloys

A previously unreported mesoscale structure in nanocrystalline Ni–Fe electrodeposits, existing at a length scale between the nanometer-scale grains and the macro-scale dimensions of the electrodeposit, is presented. This structure can be seen in etched cross-sections as a series of bands that are oriented perpendicular to the growth direction and was extensively characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). TEM with energy dispersive X-ray spectroscopy (EDS) suggests that there are periodic variations in the alloying components. In addition, variations in the secondary ion signal obtained from TOF-SIMS analysis indicate that there are likely fluctuations in the concentration of light impurities, such as oxygen and hydrogen. These compositional modulations may have an important effect on the mechanical behaviour of the material.