Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles
2013 (English)In: CrysteEngComm, ISSN 1466-8033, Vol. 15, no 6, 1257-1263 p.Article in journal (Refereed) Published
Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120-400 degrees C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120-350 degrees C and rates of temperature increase of 20-100 degrees C min(-1), the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is generally difficult to achieve using wet-chemicals under kinetic control. The amorphous precursor particles (similar to 10 nm) transformed into crystallites (similar to 30-50 nm) during sintering. Consistently, the specific surface areas of 140-160 m(2) g(-1) for the precursor particles were reduced to 10-20 m(2) g(-1) for the porous tablets. The porous network within the tablets consisted of fused aragonite and vaterite particles in a ratio of similar to 80 : 20. The fraction of aragonite to vaterite was invariant to the temperature and rate of temperature change used. The particle size increased only to a small amount on an increased rate of temperature change. At temperatures above 400 degrees C, porous tablets of calcite formed. The later transformation was under thermodynamic control, and led to a minor reduction of the specific surface area. The size of the crystallites remained small and the transformation to calcite appeared to be a solid-state transformation. Porous, template-and binder-free tablets of calcium carbonate could find applications in for example, biology or water treatment.
Place, publisher, year, edition, pages
2013. Vol. 15, no 6, 1257-1263 p.
IdentifiersURN: urn:nbn:se:su:diva-88304DOI: 10.1039/c2ce26604kISI: 000313532100028OAI: oai:DiVA.org:su-88304DiVA: diva2:611905