This application note shows that the Epsilon 4 - a high-performance energy dispersive X-ray fluorescence spectrometer - is capable of analyzing major and minor elements in cement samples.
X-ray fluorescence spectrometry is used extensively for the analysis of cements and associated raw materials. Simple sample preparation, high accuracy and precision are the main reasons for this choice. Accurate cement analysis is important for many reasons, for example, superior process control with associated cost savings; minimizing and controlling contamination and environmental pollution during cement manufacture; quality control of products; and pure research. To show the capabilities of the Epsilon 4, major and minor elements in cement pressed powders were measured and the results are shown in this application note.
Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a 10W, 50 kV silver anode X-ray tube, 6 filters, a helium purge facility, a high-resolution silicon drift detector, a spinner and a 10-position removable sample changer.
The samples were prepared by grinding 5 g cement material with 0.5 g of binder (wax). After grinding, the mixture was pressed into a pellet of 32 mm diameter (20 tons, 30 s dwelling time).
Eleven cement standards from China were used to set up a calibration for nine major oxides (Ca, Si, Al, Fe, S, Mg, K, Ti, and Na). Two different measurement conditions were used, each one optimizing the excitation of a group of elements (Table 1).
Table 1. Measurement conditions
Figure 1. XRF spectrum of a NIST cement pressed powder showing the excellent sensitivity and resolution of the detector, resulting in fully separated Na, Mg, Al and Si peaks.
Figure 2. Calibration plot of MgO in cement pressed powder
Accurate calibration results
Figure 2 shows a calibration plots for MgO in cement pressed pellets. This plot shows a good correlation between the certified concentrations and the calculated concentrations. Detailed results for MgO and the other compounds are listed in Table 2.
Table 2. Calibration results
To test the analytical precision of the instrument, one cement sample was measured 10 times consecutively, using the conditions given in Table 1. The certified concentration, average concentration, and the RMS (1 sigma standard deviation) are expressed in Table 3.
Table 3. Results of the repeatability test
The results clearly demonstrate that the Epsilon 4 EDXRF spectrometer is suitable for the analysis of major and minor compounds in cement. Accurate, reliable and repeatable results are obtained in 3 minutes measuring time per sample.