Formation mechanism of fibrous cobalt oxalate precipitated from alkaline Co2+–NH3–C2O42−–H2O system

The cobalt oxalate particles with fibrous morphology were obtained by precipitating CoCl2 and mixed (NH4)2C2O4, NH3·H2O solutions in a double jets process. The samples were characterized by SEM, XRD, FTIR, TG/DTA and GCMS. Thermodynamic calculations and experiments revealed that the formation of Co(NH3)n2+ (n = 1,2,…,6) results in species variation of cobalt oxalate precipitated in alkaline Co2+–NH3–C2O42−–H2O system. It was found that there are two kinds of cobalt oxalates precipitated in Co2+–NH3–C2O42−–H2O system with the change of synthetic conditions. One is β-CoC2O4·2H2O with a square columnar morphology. The other is Co(NH3)1.5C2O4·2H2O with a fibrous morphology, a species of cobalt oxalate without being recorded in newest JCPDS files. The formation mechanism of fibrous cobalt oxalate powders is that Co(NH3)1.5C2O4·2H2O precipitates in alkaline Co2+–NH3–C2O42−–H2O system.