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Phase composition study of natural minerals used as a source of white pigment production

Marcin T. Klepka 1Roman Minikayev 1Maciej Jablonski 2Aleksander Przepiera 2Velichka Kontozova 3Krystyna Lawniczak-Jablonska 1

1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
2. Technical University, Institute of Chemistry and Environmental Protection, Al. Piastów 42, Szczecin 71 065, Poland
3. University of Antwerp, Department of Chemistry, Groenenborgerlaan 171, Antwerp 2020, Belgium


The phase composition of mineral ilmenites originated from the several places in the world (Norway, China, India, Australia) was investigated using complementary non-destructive and destructive methods. These minerals are commonly used in the white pigment production. Composition of the phases has large influence on efficiency and the quality of the final product. The non-destructive X–Ray Powder Diffraction (XRD), Single Particle Electron Probe Micro Analysis (Single Particle EPMA) and conventional X-Ray Fluorescence analysis (XRF) as well as destructive classical chemical analysis were applied for full characterisation of the mineral ilmenites. The materials have very complicated morphology, therefore conventional XRD and XRF provides confusing results which in many cases do not match. In a standard procedure composition of phases is given as a content of the most popular oxides. It does not fit to the real amount of oxygen in the material and quantity of particular chemical compounds. The diffraction pattern is complicate and several peaks overlap what make the analysis complicate and not unambiguous.
To solve this problem we applied different techniques. The XRF was used to get the knowledge about average elements content and from the balance of elements the possible phases which were assumed. To characterize the homogeneity and local composition of investigated minerals, EPMA with single particle approach and conventional φρz correction procedure were used.
The Single Particle EPMA method and integrated software have been developed at Department of Chemistry, University of Antwerp for quantification of individual aerosol particles based on an iterative reverse Monte Carlo simulations combined with successive approximation for the elemental composition. This technique allows determining the concentration of low Z elements such as carbon, nitrogen and oxygen. The analyzed particles were divided into different groups (clusters), applying Hierarchical Clustering Analysis (HCA) based on their compositional similarity and their relative abundances in the sample Next, the set of phases existing in the given cluster were proposed to keep the overall content of elements in clusters in agreement with the measurements.
These results were used as a starting point in the XRD refinement and compared with the results of chemical analysis. The chemical analysis allowed estimating the amount of majority elements (Ti, Fe) at the particular ionic state. This ionic state superimpose occurrence of the particular phase. However this analysis is laborious, very time-consuming and destructive.
Three main phases were identified in the studied minerals unambiguously by all applied methods: ilmenite (FeTiO3), pseudorutile (Fe2Ti3O9), hematite (Fe2O3) and several minority phases like: MnTiO3, MgSiO3, MgTiO3, Cr2O3.


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Presentation: Poster at 11th European Powder Diffraction Conference, Poster session, by Marcin T. Klepka
See On-line Journal of 11th European Powder Diffraction Conference

Submitted: 2008-05-07 16:46
Revised:   2009-06-07 00:48