During the past 10 years XRD (X-ray diffraction) gained greater acceptance for industrial applications, particularly for the cement industry. One of the major drivers is the need for more and better phase information at the different steps during the production.
This inludes the control of incoming goods, the cross check of semi-finalized materials during production and the final quality control. Quantitative phase analysis provides very valuable information to the process and quality control. For example is the knowledge about the abundance of different clinker minerals in the cement manufacturing process is crucial to improving the process and to predict the final product performance.
In the past, the simplified Bogue approach was sufficient. In the early days this normative indirect description successfully indicated the sintering conditions in the kiln and the characteristics of the clinker for the production of cement. In the past few decades, more and more alternative raw materials and alternative fuels are used, requiring the need for a direct determination of the clinker minerals. For example, elements like Mg stabilize the alite phase that lead to an improved hardening behavior of the cement, while elements like phosphorous effect the formation of alite in a negative way. Unfortunately, the effects of certain elements not straightforward, because there are usually interconnected changes in the stability of various phases with regards to coupled substitution of elements in the relevant crystal structures.
Therefore, the only opportunity to solve these issues is through the direct measurement of the clinker minerals. The introduction of fast detection systems together with the use of the Rietveld-method contributes substantially to the ability to extract the needed information from the clinker. This methodology, however, requires near perfect sample preparation, fast representative sampling, and optimized milling and pressing of the powder to obtain useful results in a production environment.
Automated sample preparation using equipment such as the Centaurus combined mill and press are required to ensure reproducible and accurate results in production settings.
The demands of research and development applications, however, require a higher quality of sample preparation and flexibility than production environments. This is because of the wider range of materials that have more complicated sample preparation issues, such as preferred orientation effects. Preferred orientation effects can be corrected in the subsequent data analysis during the Rietveld refinements, but this approach can also introduce larger errors. For example these errors can increase by a factor of 8 in cases where a very strong preferred orientation correction is applied using the March-Dollase algorithm. For that reason a reduction of the preferred orientation of the powder is essential for a proper analysis, especially during R&D, where the quantitative models were developed.
Today the best methodology to press powder samples is the use of a front loading, including randomization and back pressing of the materials which can be accomplished using the unique ASP 100 automated soft press which was specifically developed to address these issues.