2D (3D) Profiling

Analysis of galvanic layers

Cooper + Tin bronze:

  • exhibits an extraordinary range of alloys with widely differing properties
  • well known for production of electromechanical devices (proper proportions)
  • surface should enable welding, sustain temperatures of 300°C, wear and corrosion

Thermal annealing is used to provide proper mixing and increase temperature stability of layers. Galvanization is the cheapest and the most frequently used industrial coating technique. The diagnostics of usually thick deposited layers is rather time consuming and expensive (surface layers have to be removed). Proton-impact RBS exhibits both large range and sufficient depth resolution for efficient and cost-effective depth profiling. Several galvanic coatings composed of Sn/Cu/Ni/Graphite layers were analyzed at Ljubljana tandetron. Macro and microbeam analysis were performed with RBS, PIXE and SE spectroscopy.

Various samples with unknown layer and elemental structure were obtained from the manufacturer. They were first examined by the broad proton beam and then with microbeam. We used PIXE and SE spectra to determine the elemental composition on the surface. Line scans across the edges revealed the elements in the lower layers. Point analysis were performed on places where upper layer was thinner or removed. RBS spectra were collected.
The energy scale was calibrated using the RBS signals from SiO2 and Ta(sample holder).

Detectors:

  • PIXE, Si(Li),vacuum, 8 micron Be window, no absorbers
  • RBS, Annular PIPS, 170o, 0.78 strd
  • RBS, Surface Barrier, d = 5 mm, 135°, dist. = 70 mm
  • SE, Channeltron, Umax = 2 kV, Uel = - 50 ... +50

Positioning of the sample: Optical lens with high magnification. Optimization of the beam: 125, 25, 12.5 microns copper mesh.

Conventional analysis of unannealed sample with interface layer thickness equal to 2.3 microns:

  • RBS spectra (top left)
  • concentration profile (top right)

Conventional analysis of annealed sample with interface layer thickness equal to 11.0 microns:

  • RBS spectra (top left)
  • concentration profile (top right)

Microbeam analysis of Sn/Cu coatings:

Two types of analyses were performed; scans 2x2 mm and point analysis (A and B). Figure below: Secondary electrons map and elemental maps of Sn, Cu and Ni. Scan size: 2x2 mm.

Results of point analysis:

  • Point A: the thickness of the Sn layer is 8 microns, the thickness of the intermediate layer with mixture of Sn, Cu and Ni is 3 microns. After 11 microns, only Cu and Ni can be detected.
  • Point B: the thickness of the Sn layer is 1 micron, the thickness of the intermediate layer with mixture of Sn, Cu and Ni is 3 microns.

Analysis of metallic paints in car colours

Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element polymer matrix. Spatial distribution and orientation of metallic flakes inside the matrix determines the covering efficiency of the paint, glossiness, and its angular-dependent properties such as lightness flop and color flop.

Pigment volume concentration

Different pigment volume concentration (PVC) of Al flakes in dry paint layer PIXE Al Ka map, proton dose 0.03 microC/map.

Flake size: 34<d<75 microns, < d > = 49 microns, :silver dollar: type -soft surface, soft edges. Scan size: 500 x 500 microns.


Grouping of Al flakes

PIXE map on the left showing the regions with flakes.

RBS point spectra revealed number of overlapping flakes in vertical direction. The spectrum on the right was taken in point 1 (see below).

Flake size: 10<d<37 microns, < d > = 23 microns. Scan size: 300 x 300 microns.

Line scan:

10 points line scan across the flake showed the peak shift - 1019 (1 ±0.2) at/cm2 which corresponded to 0.8 micrometers of dry polimer. Upper flake was tilted 0.7 (1 ±0.2) degree ! (in respect to the paint layer surface). The distance from point 4 to point 10 was 70.8 microns.

Contact person:

Dr. Primož Pelicon



Last updated: 01/22/2014