Tanaka, I; Nakahara, F; Kageyama, H; Nakahara, Y
The spherical particles of manganese(II) carbonate were prepared by "Interfacial Reaction Method", in which the manganese(II) carbonate was formed by the reaction of manganese (II) salts aqueous solution emulsified in benzene with carbonate salts solution. Some manganese(II) salts (MnCl2, MnSO4, Mn(NO3)2) and some carbonate salts (NaHCO3, Na2CO3, K2CO3) were used in order to make clear the difference of formation of spherical particles by the kinds of salts. The particle size distributions, DTA-TG curves, X-ray diffraction patterns, specific surface areas and pore volume distributions were measured to clarify the properties of the spherical particles.
The spherical particles were formed by reacting MnCl2, MnSO4 and Mn(NO3)2 with NaHCO3 but were not formed with Na2CO3, K2CO3 (Table. 1). The conditions for the preparation of the spherical particles can be summarized: a) the mole ratio of the manganese(II) salt (2 mol/dm3 solution) and carbonate salt was over 2/15; b) the volume ratio of the manganese (II) salt solution and emulsifier solution (1.5 wt%) was 1/2-1/5 (Table. 1). That is to say, it is necessary to select good combinations of the kinds, volume and concentration of manganese (II) salts, carbonate salts and emulsifiers in order to allow the reaction of the manganese (II) salt and the carbonate salt to proceed rapidly on the surface of emulsion without burst of the emulsion. The particle mean diameter was about 1.00 approximately 1.50-mu-m, the specific surface area was 7 approximately 32 m2/g, and the particle had many pores of 20 approximately 300 angstrom in diameter on the surface (Fig. 4, Table. 2, Fig. 7). The manganese(II) carbonate spherical particles were transformed to crystalline Mn2O3 particles by heating at 700 approximately 800-degrees-C, 10 h, of which shapes were also spherical (Fig. 6). The particle diameter was not changed, but pore volume and specific surface area decreased by heating at high temperature (Table. 2, Fig. 7).