Derek Graham

Conductive copper and nickel lines via reactive inkjet printing

Conductive copper lines were directly written on paper through inkjet printing of a copper salt and a reducing agent sequentially from a multi-color printhead. The copper ink was an aqueous copper citrate solution and the reducing agent was a solution of sodium borohydride (NaBH4). The two inks were loaded in two separate compartments of a traditional HP color cartridge, which enabled the generation of two droplet streams from the two separate compartments. The cartridge was fixed above an X–Y positioning table and conductive copper lines were prepared using multiple printing passes. The estimated conductivity obtained on paper (1.8 × 106 S m−1) is about 1/30 that of bulk metal copper (59.6 × 106 S m−1 at room temperature). Oxidation of the printed copper lines was studied using EDS elemental analysis of lines printed onto poly(vinylidenefluoride), PVDF, membranes. The Cu–O ratio of copper lines decreased over 400 hours in air, due to oxidation, but leveled off afterwards. The same approach has also been applied to the printing of nickel where oxidation is less marked.

Time-lapse lab-based x-ray nano-CT study of corrosion damage

An experimental protocol (workflow) has been developed for time‐lapse x‐ray nanotomography (nano‐CT) imaging of environmentally driven morphological changes to materials. Two case studies are presented. First, the leaching of nanoparticle corrosion inhibitor pigment from a polymer coating was followed over 14 days, while in the second case the corrosion damage to an AA2099 aluminium alloy was imaged over 12 hours. The protocol includes several novel aspects relevant to nano‐CT with the use of a combination of x‐ray absorption and phase contrast data to provide enhanced morphological and composition information, and hence reveal the best information to provide new insights into the changes of different phases over time. For the pigmented polymer coating containing nominally strontium aluminium polyphosphate, the strontium‐rich components within the materials are observed to leach extensively whereas the aluminium‐rich components are more resistant to dissolution. In the case of AA2099 it is found that the initial grain boundary corrosion is driven by the presence of copper‐rich phases and is then followed by the corrosion of grains of specific orientation.