With a view to improving the rapidity and precision of X-ray fluorescence analysis of briquetted iron ores, a comparison was made of the natures of surfaces of briquetted samples prepared by a newly proposed dry grinding method using graphite powder as a binder and by three conventional methods, viz. a dry grinding method using no binder, a wet grinding method using stearic acid powder and a wet grinding method using polystyrene-maleic acid powder as a binder. An electron probe microanalyzer and a scanning electron microscope were used in this investigation. The results obtained are as follows:
(1) The new graphite grinding method is more suitable for the minute grinding of iron ores than other grinding methods and can produce iron ores with a uniform particle size of 1 μm under.
(2) By grinding through the graphite grinding method, iron ore powders are readily prepared into briquet after grinding, thus shortening the time necessary for briquetting.
(3) The internal standard (Co
2O
3) is uniformly and homogeneously dispersed in the briquet prepared by the graphite grinding method, compared with other grinding ones.
(4) Calibration curves exactly became simple for the important components in iron ores, that is, total Fe, CaO, SiO
2, Al
2O
3 and MgO by adopting the graphite grinding method.
(5) Repeatability and precision (σ
d) were improved by the graphite grinding method. For example, σ
d was 0.43 for total Fe and 0.05 for CaO.
As mentioned above, the graphite powder has the grinding effect as a solid lubricant by the use of the graphite grinding method, so that the briquet obtained becomes uniform with improvements in repeatability and precision. The graphite grinding method is also suitable for the analysis for process control.
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