On the electrodeposition and characterization of niobium from fused fluoride electrolytes
The electrodeposition of niobium from a binary electrolyte consisting of KF and NaF was characterized and compared with that from the ternary electrolyte of LiF, NaF and KF. The deposition experiments were conducted at current densities between 5 and 35 mA cm−2 and electrolyte temperatures between 725 and 800°C. DTA measurements indicated the melting points to be 450 and 710°C for the ternary and binary electrolytes with added K2NbF7; however, it was necessary to operate both electrolytes above 725°C to obtain dense coherent deposits. Coating morphology was described by optical and scanning electron microscopy studies, while coating structure and properties were characterized by X-ray diffraction analysis. In particular, a series of diffraction measurements were reported to describe the changes in the microstructure of the deposited material as a function of the preparation conditions.
High Rate Electrodeposition of Niobium from Molten Fluorides Using Periodic Reversal Steps and the Effects on Grain Size
Application of periodic reversal (PR) technique, in which a cathodic (depositing) step is followed by an anodic (polishing) step, was found very beneficial to the increase of electroplating rate of coherent niobium. With no mechanical agitation, the application of the PR technique facilitated an electroplating rate increase by a factor of about 10 over the direct current method. The morphology of the deposits was found to be of the columnar structure. The columns became more oriented along the [100] direction, and of smaller diameters as the rate of electrodeposition increased. Unexpectedly, beyond a certain rate and under certain conditions, the columnar grains became large once again. Under such conditions a pronounced heteroepitaxial effect of the substrate (Cu) grains on the deposit grain size and orientation was observed.
Using Infrared Thermography to Detect Moisture in Historic Masonry: A Case Study in Indiana
Nondestructive testing mapped water infiltration in the decoratively painted interior of a Masonic Temple in Muncie, Indiana.