High-precision quality management system
based on XRD/Rietveld analysis
| ＞Introduction | ＞Quality Management Video | ＞Overview and Features | ＞Measurement and Analysis | ＞Future Outlook |
High Precision, Fast Quality Management System with High Utility Value
Cement is a mix of inorganic, powdered compounds which harden as a result of chemical reactions with water. As Table 1 shows, cement quality refers to properties such as fluidity, setting time, heat generation and strength. The quality of cement is strongly affected by the ratio of its constituent compounds (mineral composition). That's why the appropriate mineral composition varies by cement type. These differences make it essential to have a system for managing the mineral composition of products.
In the past, cement mineral composition has been theoretically calculated based on chemical composition, but the increase in trace elements resulting from greater use of recycled fuel and raw materials has resulted in deviations from actual mineral compositions. Conventional methods of measuring mineral composition have also taken too much time.
These have resulted in the need for a management system which can more accurately monitor mineral composition. In response, Taiheiyo Cement has deployed a high-precision quality management system based on XRD/Rietveld analysis, using X-ray diffractometers. This system has made it possible to perform high precision, completely automated quality management, measuring the mineral composition of cement products. It has also greatly reduced analysis times from the several hours required to measure a sample using the past approach to roughly 10 minutes.
These have resulted in the need for a management system which can more accurately monitor mineral composition. In response, Taiheiyo Cement has deployed a high-precision quality management system based on XRD/Rietveld analysis, using X-ray diffractometers. This system has made it possible to perform high precision, completely automated quality management, measuring the mineral composition of cement products. It has also greatly reduced analysis times from the several hours required to measure a sample using the past approach to roughly 10 minutes.
Conventional management method
（１）Microscope-based point counting method
Samples are observed under a microscope, and their mineral composition is directly measured by measurement personnel.
Problems
- Large degree of result disparity between measurement personnel
- Crushed samples and porous samples are not well suited to observation
- Sample preparation and measurement takes 5 to 6 hours or longer
（２）Calculation by applying Bogue's formula (theoretical formula) to X-ray fluorescence results
In this method, the chemical composition is measured by performing X-ray fluorescence on the sample, and then Bogue's formula is applied to the results to derive the mineral composition.
Problems
- Only main chemical composition is taken into consideration in calculations, so when there are a large amount of trace elements, the derived mineral composition may vary significantly from the actual mineral composition.
- Factors which affect actual mineral compositions, such as sintering temperature and cooling speed, are not reflected.
XRD/Rietveld analysis
An X-ray diffractometer (XRD) is used to measure the X-ray pattern of a sample. A calculation method called Rietveld analysis is then used to analyze the results, directly calculating the mineral composition.
Advantages
- Measurement requires little time
(Takes several hours when using the point counting method) - Can directly determine mineral composition
(The Bogue's formula approach consists of theoretical calculations based on chemical analysis, and may differ from actual composition)
What is Rietveld analysis?
Rietveld analysis is a method created by Dutch crystallographer Hugo Rietveld in 1969 for use with neutron diffraction. The XRD/Rietveld method uses X-ray diffraction.
In XRD/Rietveld analysis, theoretical diffraction profiles for X-ray diffraction patterns are refined using the least square method to determine the crystalline structure parameters of individual minerals. This makes it possible to refine their crystalline structure.
In recent years, this method has come to be applied to samples containing multiple types of minerals, such as cement samples. When this method is used, not only the sample's crystalline structure but also the parameters indicating the ratio of various elements, referred to as the scale factor, are refined. This is making it possible to determine how much of which minerals are present in the sample. We used our own accumulated expertise to make it possible to perform quantitative analyses of cement with the optimal degree of precision.
In XRD/Rietveld analysis, theoretical diffraction profiles for X-ray diffraction patterns are refined using the least square method to determine the crystalline structure parameters of individual minerals. This makes it possible to refine their crystalline structure.
In recent years, this method has come to be applied to samples containing multiple types of minerals, such as cement samples. When this method is used, not only the sample's crystalline structure but also the parameters indicating the ratio of various elements, referred to as the scale factor, are refined. This is making it possible to determine how much of which minerals are present in the sample. We used our own accumulated expertise to make it possible to perform quantitative analyses of cement with the optimal degree of precision.
