XRF is an analytical technique used to determine the chemistry of a material – In simple terms it tells us which elements are present and the quantities of each element. There are two methods for this test namely pressed pallet and fused bead method. We will look at the fused bead method.
It works by emitting X rays onto a material glass bead sample whereupon the atoms in the material absorb this X-Ray energy. The atoms then emit their own characteristic X-Rays (Fluorescence) back to the instrument for reading. Think of this characteristic X-Rays as a fingerprint for each element. The results from the XRF gives us elemental oxides such as Calcium (CaO), Silicon (SiO2) etc.
In order for the spectrometer (XRF machine) to read the chemistry, a glass bead containing the sample material first has to be created (Sample Image X). The formation of the glass bead starts by crushing and milling the sample material to a fine powder after which it is combined with a powder fluxing agent (typically lithium based).
After a thorough mixing the sample is placed in a furnace at 950 ℃ for 1 hour to burn off all combined water and carbon dioxide before placing the sample in a fusion machine. The fusion machine gradually heats the sample to a melt after which it automatically casts the molten sample into a reservoir that forms a homogeneous glass bead after cooling (Picture X). It is this glass bead that is placed into the spectrometer for chemical analysis.
In the next part we will look at how the cement business unit uses XRF for auto-control testing, composition confirmation and problem solving.
Figure 1: Glass Beads
Figure 2: Fusion machine casting molten samples into reservoirs
