High-energy milling induced calcite to aragonite transformation in eggshell

A. Zorkovská and P. Baláž

Institute of Geotechnics, SAS, Watsonova 45, 043 53 Košice, Slovak Republic

Eggshell biomaterial has been mechanically activated in a planetary mill Pulverisette 6 (Fritsch, Germany) in air for increasing time (15 – 960 min.). X-ray diffraction study of the milling products has been carried out using a D8 Advance diffractometer (Bruker, Germany), the diffraction patterns were treated with the MAUD and Diffrac^plus Topas software.

The analysis has revealed an extensive and fast calcite-to-aragonite transformation, what is a polymorphous transformation of CaCO₃ from trigonal to orthorhombic crystal system. The process started after 15 min. of milling. The volume fraction of the aragonite phase reached maximum (~65%) after 240 min. of milling, the mechanochemical equilibrium between phases was established after 960 min.

Figure 1. XRD spectra of high-energy milled eggshell. Duration of milling indicated in the graph

The Slovak Grant Agency VEGA (project 2/0009/11), the Agency for Science and Development (project APVV-0189-10) and the project “Centre of Excellence of Advanced materials with Nano- and Submicron–Structure” (“nanoCEXmat”) financed by the European Regional Development Fund are gratefully acknowledged. The SEM microphotographs have been kindly provided by the International Laser Center in Bratislava (J. Kováč, A. Šatka)

Extended contribution submitted