Linsey Lapeire

Structural dependence of gold deposition by nanoplating in polycrystalline copper

In the present work, the gold-nanoplating technique is used to monitor differences in the electrochemical activity of different types of grain boundaries in high-purity copper. Gold-nanoplating is based on the electrochemical displacement of gold, which is deposited as particles from an aqueous solution on the polycrystalline copper surface. The complementary use of electron backscatter diffraction for revealing microstructural features, field emission scanning electron microscopy for imaging, and energy-dispersive X-ray analysis for quantification of the deposited gold makes it possible to detect differences in the grain boundary activity for different types of grain boundaries. In this way, it becomes possible to distinguish special from random boundaries in an efficient way. Also quantitative experimental results on grain boundary activity are produced, which correlate strongly with literature predictions on grain boundary energy.

Combined EBSD and AFM Study of the Corrosion Behaviour of ETP-Cu

In order to increase the sustainability of metals, a more detailed understanding of the corrosion process is of crucial importance. Current literature often considers corrosion as a purely chemical interaction with a nearly exclusive dependence on compositional effects, while ignoring microstructural and crystallographic properties of the metal surface. Some recent literature data, however, suggest an important effect of microstructural elements such as grain size, crystallographic orientation and grain boundary characteristics. The aim of this work is to obtain a better understanding of the relation between the corrosion behaviour of a metal and its microstructural and crystallographic features. Therefore, warm rolled Electrolytic Tough Pitch (ETP-) Cu was immersed in a 0.1 M NaCl and 0.5M Na2SO4 solution and the combination of Atomic Force Microscope (AFM) and Electron Backscatter Diffraction (EBSD) allowed to identify differences in attack for different crystallographic orientations.

Nanoscale Intergranular Corrosion and Relation with Grain Boundary Character as Studied In Situ on Copper

The initiation of intergranular corrosion at various types of grain boundaries (GBs) was studied at the nanometer scale on microcrystalline copper in 1 mM HCl aqueous solution. In situ Electrochemical Scanning Tunneling Microscopy (ECSTM) and Electron Back-Scatter Diffraction analysis of the same local microstructural region were combined using an innovative methodology including micro marking performed with the STM tip. The results demonstrate that electrochemically-induced intergranular dissolution, at the surface termination of GBs, is dependent on the grain boundary character. It is found that random high angle boundaries as well as sigma9 coincidence site lattice (CSL) boundaries are susceptible to nanoscale initiation of intergranular corrosion while for sigma3 CSL boundaries the behavior is dependent on the deviation angle of the GB plane from the exact orientation. For the sigma3 twins, a transition from resistance to susceptibility occurs between 1{\deg} and 1.7{\deg} of deviation as a result of the increase of the density of steps (i.e. misorientation dislocations) in the coincidence boundary plane. The work emphasizes the precision needed in the design of the grain boundary network in applications where intergranular corrosion or its initiation must be controlled at the nanoscale.

Texture comparison between cold rolled and cryogenically rolled pure copper

Nowadays, there is a considerable scientific interest in bulk ultrafine grained materials, due to their potential for superior mechanical properties. One of the possible formation methods of nano-grained materials is cryogenic rolling. The influence of rolling at cryogenic temperatures has been investigated. Significant differences in the textures and the microstructures can be observed between the cryogenically rolled copper and conventionally cold rolled copper, reduced to the same thickness.

On the Role of the Crystallographic Grain Characteristics in the Corrosion Behavior of Polycrystalline Copper

In order to increase the sustainability of metals, a more detailed understanding of the corrosion phenomenon is of crucial importance. In current literature, corrosion is often considered as a purely chemical interaction with nearly exclusive dependence on compositional effects, whilst ignoring the microstructural features of the metal surface. In the present work, results are presented which illustrate both the role of grain orientation and grain boundaries in the corrosion process. To evaluate the grain orientation dependent electrochemical behavior, polycrystalline Cu, was brought into contact with a corrosive electrolyte. Subsequently, the attack was evaluated by measuring the surface with both Atomic Force Microscopy (AFM) and Electron Backscatter Diffraction (EBSD). It was demonstrated that the grain orientation itself did not significantly influence the corrosion kinetics, but, alternatively, that the orientation of the neighboring grains seemed to play a decisive role in the grain dissolution rate. To increase understanding on the role of grain boundaries, a method was developed based on the electrochemical (galvanic) displacement of gold, which is deposited from an aqueous solution on a pure copper substrate. This technique demonstrated its sensitivity to the grain boundary characteristics as far less gold was deposited on special boundaries, such as coincidence site lattice boundaries, as compared to the random high angle grain boundaries.