ConclusionsIn summary, cobalt oxalate samples were successfully preparedusing the microwave-assisted method, employing MWPs of 280and 700 W, in the presence of CTAB. The pure Co3O4NPs wereobtained by the calcination in air at 500◦C, for 1 h, of its oxalateprecursor. The results showed that the MWP played an impor-tant role in morphology and size control of both CoC2O4·2H2O andCo3O4NPs. Needle-like and rod-like CoC2O4·2H2O and Co3O4mate-rials were obtained utilizing MWPs of 280 and 700 W, respectively.High-magnification TEM images demonstrated that the obtainedCo3O4structures consist of numerous nanocapsules having diame-ters of 47–65 and 75–125 nm and lengths of 62–79 and 100–180 nmfor the samples prepared using MWP of 280 and 700 W, respec-tively. The obtained results put forward a new research strategyfor controlling the size of Co3O4, which is an important factor thatinfluences its catalytic activity in reactions like N2O decomposition