XRF is the first analytical technique used on the collection. A Bruker Tracer III-V+ X-ray fluorescence (XRF) spectrometer with a K 4084 Rhodium tube, channel 2048, and 40 kV connected to Bruker S1PXRF software to analyze these samples. XRF spectroscopy determines the elemental composition of whatever material you are analyzing.

Each run was collected in a 30-second scanning period, and this data was then exported to the Artax software for analysis. For each object, the handheld machine was manually directed and placed on different areas of the object. Data was collected from various locations on the object to try to generate a full image of the surface composition.

XRF works using three things: 1) X-rays, 2) electrons, and 3) energy! When using an XRF, you point the X-ray source at the material, which comes from the rhodium tube, and shoot a high-energy ‘incident’ X-ray. This X-ray causes the electrons in the material to fluoresce. This doesn’t mean that the material starts to glow, but instead goes through the process of absorption, relaxation, and emission. In this process, electrons, after being exposed to the X-rays, absorb the high energy and are emitted from their orbital. This leaves a gap that needs to be filled. An electron that is situated on a higher energy orbital level falls down to fill the gap, lowering the energy, which is favorable. Energy is released in this process in the form of a photon, which releases a secondary x-ray, which is characteristic of the element present.

Scanning electron microscopy (SEM) provides high-resolution images and detailed surface information of samples. The resolution of SEM instruments works within micrometers! This means that objects that are just a tiny crumb look like mountains, and the surface can be clearly visualized. To prepare our samples, corrosion product was taken from the surface of four objects using a scalpel. This was placed on metal stubs with carbon tape between the stub and the sample.

An electron beam comes from the electron gun at the instrument’s top. This beam is accelerated and focused by a series of lenses, creating a high-energy beam that is directed onto the sample. Two types of emissions are detected, secondary electrons and backscattered electrons.

 Secondary electrons (SE) are low-energy electrons resulting from the inelastic scattering of the incident electron beam with the sample. By detecting these electrons, we can create high-resolution topographic images, which provide information about the surface of the object! 

Backscattered electrons are high-energy electrons that are elastically scattered from the sample. By detecting these electrons, images correlated to compositional information are created.