Sample preparation for XRF analysis – cement and building materials
For many years the cement industry has been relying on X-ray fluorescence (XRF) for the elemental analysis of cement and related raw materials. Sample preparation by pressing powders into pellets was commonly and widely used for decades, but for the last decades, borate fusion has become more important and increased in popularity. Both methods are equally important. One should base the decision on whether to use one or the other on various factors.
Crushing
Crushing of the material is required to reduce its size allowing further processing, such as representative sub-sampling, homogenization, and grinding.
Grinding
Grinding of the material to a fine powder is required to minimize undesired particle size effects and to allow further processing like pressing or fusion.
Pressing
Pressed pellets are often very successfully used in production control, especially if the calibration ranges are narrow.
You can press pellets into Al cups or steel rings. The use of binders is usually required to achieve the necessary mechanical stability and robustness. Malvern Panalytical also offers the ultra-wax binder, for the preparation of high-quality pellets for the most demanding applications. For a limited number of countries, the binder (and other consumable products) is available from the E-store.
Fusion
For applications where accuracy and reproducibility play a significant role, you can dissolve the sample into a molten glass-forming flux at high temperatures. This ultimately results in a completely homogeneous bead. In this way, you can eliminate particle size and matrix effects (almost) completely.
It is not always easy to obtain suitable standards that have the same particle size, mineralogy, surface roughness and segregation characteristics as the production samples. Therefore, the role of fused beads is extremely important in setting up reference calibrations for determining in-house standards for use in production control calibrations. A possible solution for fusion is to make use of one of the Claisse® fusion instruments.
Also in the seven-part series on ‘Sample preparation for XRF analysis’:
Watch out for other upcoming blogs in the seven-part series on ‘Sample preparation for XRF analysis in the course of this year.