Synthesis of γ‐Type CMD from Dense MnCO3

Abstract

Current CMD (chemical manganese dioxide) has the crystal structure indicating broad patterns (not sharp and undefined peak) between (2θ, Fe‐Kα), as exemplified by International Common Samples IC‐5, 8, 12, and 22. However, a definite γ‐type CMD has not yet been developed. The authors succeeded in the synthesis of a 92% grade γ‐type CMD by treating dense with an aqueous solution of caustic soda to convert it into a dense , followed by oxidation in air and with a gas mixture to give 85% grade . It has then reacted with . The γ‐type CMD obtained has a tap density of about 1.47 g/cm−3, which is rather low for dry battery use. An attempt was made to obtain a denser product by subjecting it to the chlorate reaction under acidic conditions. It was demonstrated that a CMD having a tap density of 2.3 g/cm−3 (nearly the same as that of EMD) and with an x‐ray diffraction pattern of a more developed crystal structure than that of IC‐17 (EMD) can be obtained if the proportion of formed by the chlorate reaction is only about 25% of the total .