The use of synchrotron x-rays to observe copper corrosion in real time. Department of Physics, University of Warwick, Coventry CV4 7AL, UK

Transcription

1 The use of synchrotron x-rays to observe copper corrosion in real time. Mark Dowsett 1, Annemie Adriaens 2,* Chris Martin 3 and L. Bouchenoire 4,5 1 Department of Physics, University of Warwick, Coventry CV4 7AL, UK 2 Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, Ghent, Belgium 3 School of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, UK 4 uropean Synchrotron Radiation Facility, XMaS Beam Line, 6 Rue Jules Horowitz, BP220, Grenoble, Cedex, France 5 Department of Physics, University of Liverpool, Liverpool L69 7Z, UK * Corresponding author: annemie.adriaens@ugent.be, Fax Contents S-1 The geometry of the experiment and the reprojection algorithms for extracting the spectra. S-2 Raw image from the Mar CCD camera and its reprojection. S-3 Nantokite growth data from the droplet experiment to compare with that from espin in Figure 3 of the paper. S-4 XRD images from key stages in the experiment. S-5 The data from Figure 4(a) of the paper presented as a waterfall plot. S-6 Reference patterns for Figure 4. S-7 Pure CuCl exposed to tap water turns to cuprite. S-1

2 Figure S-1 Using the equations to the right, esaproject transforms or reprojects diffraction images into a space where the rings are straight lines (a map of 2Θ vs. out of plane scattering angle Φ). The transformation conserves intensity whilst incorporating an anti-aliasing strategy to reduce pixel sampling oscillations in the final pattern. It employs an algorithm with a saturating series for the inverse cosine function so that it is immune to rounding errors which result in the invalid expression arcos(1+ ) where 0< <<1 in some regions of the map. h cosβ 2Θ= arcos d+ y tanβ d + ρ d Φ= arcos sinα sinβ d 2 w whereρ = x 2 andα 2Θ ρ 2 h + y 2 1 tanα tanβ 2 S-2

3 (a) (b) Figure S-2 (a) Raw X-ray diffraction data from the Mar CCD camera on the XMaS beam line at the uropean Synchrotron Radiation Facility (Ironbow scale) showing the effect of reprojection. The sample is the nantokite surface from the droplet experiment after rinsing with deionised water. Referring to Figure S-1, the normal to the camera plane is at β=45 to the incoming beam so the intersections of the Scherrer cones with the detector are elliptical. (b) The reprojected image: xtraction of a 1D pattern is now a straightforward matter of summing the rows. S-3

4 Counts/10 3 Figure S-3 Waterfall plot of XRD patterns extracted from a sequence of 50 XRD images taken over 580 seconds when a copper coupon was brought into contact with a droplet of saturated copper (II) chloride solution in the ecell on the XMaS beam line. The result is similar to that seen with the Rapid II detector at SRS in Figure 3 of the paper, with the exception of the behavior of the copper reflections which first rise rapidly and then flatten off. The aquisition time per image was 5 s, and the X-ray energy was 8 kev. S-4

5 (a) (b) 2Θ Figure S-4 (c) Reprojected images from (a) the last point in the droplet experiment, (b) the surface allowed to dry and (c) after the rinsing. In all three cases the copper reflections are distinct from the others in that they are streaky, whereas the surface deposits produce a more spotty texture due to the presence of rather large but randomly oriented grains. Although image (c) is superficially identical to (a), patterns integrated out of this image show the presence of cuprite and paratacamite (Figure 4(c) in the paper.) 2Θ S-5

6 30 25 riochalcite N Nantokite Cu Copper N () N Cu N Cu () N () N Cu Wavenumber(=2 /d)/å -1 Figure S-5 Waterfall plot of the patterns shown in the time lapse image of figure 4 (a). The bifurcation of the copper and nantokite reflections is clearly seen. Some of the smaller peaks observable in Figure 4(b) are not seen here because of the linear intensity scale. S-6

7 riochalcite Paratacamite Nantokite Cuprite Copper o Wave number (= 2 / d) / A -1 Figure S-6: Reference patterns for Figure 4 of the paper. Data replotted from S-7

8 Intensity/10 3 Figure S-7 48 mg of copper (I) chloride (Alfa Aesar, %) was added to 100 ml of tap water at room temperature with a starting ph 7.8. The mixture was stirred continuously. An hour after adding the CuCl, the ph has fallen to 6.6. The greyish green CuCl turns cuprite colored on contact with the water, and as powder XRD of the reaction products confirms, has indeed largely been converted to cuprite. The reaction probably stops when each powder particle is coated with cuprite, protecting the remaining CuCl. A small amount of copper is also seen. S-8