Influence of initial CaCl 2 concentration on the phase and morphology of CaCO 3 prepared by carbonation Yong Sheng Han Æ Gunawan Hadiko Æ Masayoshi Fuji Æ Minoru Takahashi Received: 17 May 2005 / Accepted: 20 September 2005 / Published online: 2 May 2006 Ó Springer Science+Business Media, LLC 2006 Abstract Calcium carbonate particles were prepared by bubbling the mixed gas CO 2 /N 2 into CaCl 2 solution. The effect of initial CaCl 2 concentration on the morphology and phase of CaCO 3 was discussed with the help of XRD and SEM measurements. The samples prepared at low CaCl 2 concentration composed mainly of spherical vaterite. With the increase of CaCl 2 concentration, more and more rhombic particles were formed and mixed with spherical particles. When the initial CaCl 2 concentration increased to 0.3 mol/L, only rhombic calcite was formed in the final product. The change of CaCO 3 morphology with the in- crease of CaCl 2 concentration was attributed to the excess of Ca 2+ , which speeded the transformation of vaterite to calcite, thus more rhombic calcite was formed at higher CaCl 2 concentration. Introduction Calcium carbonate is a widely used chemical in various industries, such as plastics, textiles, rubbers, adhesives, paints and so on. Advanced applications of CaCO 3 are used as fillers in polyester films for the manufacture of magnetic tapes, coating of pigments used in the cosmetic industry or in the paper manufacturing [1]. The application of CaCO 3 particles is determined by a great number of strictly defined parameters, such as particles morphology, structure, size, specific surface area, brightness, oil adsorption, chemical impurity and so on [2]. One of the most important factors is particles morphology. The morphologies of crystal calcium carbonate particle are generally classified as rhombic cal- cite, needle-like aragonite and spherical vaterite. Calcite is the most stable phase at room temperature under normal atmospheric conditions, while aragonite and vaterite are metastable polymorphs which readily transform into the stable phase—calcite. The morphology of calcium carbonate particles was mainly determined by the preparation conditions, such as reactants concentration, flowing rate, pH, temperature, and additives. Reactants concentration ([Ca 2+ ] and [CO 3 2) ]) is usually considered to be the basically impor- tant factor in controlling the morphology of calcium carbonate. There are many literatures reporting the influ- ence of reactants concentration on the formation of cal- cium carbonate [3–5]. Their main concerns focused on the influence of the [Ca 2+ ][CO 3 2) ] ion product on the forma- tion of calcium carbonate. There are a few literatures investigating the [Ca 2+ ] and [CO 3 2) ] separately. Even through a few literatures were reported, some of the reporting results are contradictory or arguable. For example, Chen et al. [6] found that the concentration of calcium ion seems to be a minor factor in the determi- nation of vaterite. While Yagi et al. [7] reported that the vaterite were preferably formed at low Ca 2+ concentra- tion. For complete and clear understanding the influence of each reactants concentration, it is necessary to inves- tigate each of the species separately and systematically. The influence of [CO 3 2) ] on the formation of calcium carbonate has been discussed in another paper [8]. This paper will mainly focus on the effect of [Ca 2+ ] on the formation of calcium carbonate. The main purpose of this paper is to investigate the influence of [Ca 2+ ] on the morphology and phase of Y. S. Han (&) Æ G. Hadiko Æ M. Fuji Æ M. Takahashi Ceramics Research Laboratory, Nagoya Institute of Technology, 10-6-29, Asahigaoka, Tajimi 507-0071, Japan e-mail: hysh00@mails.tsinghua.edu.cn J Mater Sci (2006) 41:4663–4667 DOI 10.1007/s10853-006-0037-4 123