Synthesis of manganese ferrite from manganese ore prepared by mechanical milling and its application as an inorganic heat-resistant pigment

Abstract Manganese ferrite (MnFe2O4), as a high-resistance pigment, is successfully synthesized using calcined manganese ore and Fe2O3 prepared by mechanical milling and calcination. The powders obtained were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), thermal analysis and colour measurement. The effect of the milling, the composition ratio Mn: Fe, and the calcination temperatures on the synthesis are examined thoroughly. The stability of MnFe2O4 is evaluated by observation its decomposition and discolouration at various temperatures. MnFe2O4 phase with the milling process start to form at 800 °C, while without milling process the spinel phase can be obtained at 1000 °C. This finding highlight that the existence of the milling process can reduce the formation temperature of MnFe2O4. In addition, the full MnFe2O4 phase is achieved Mn: Fe = 1 at 1000 °C, while the others composition resulting in unreacted Mn2O3 and Fe2O3. Colour measurement shows that sample with full MnFe2O4 phase produces the darkest colour, while the presence of Fe2O3 and Mn2O3 on the synthesized MnFe2O4 leads to an increase in the brightness of colour. A thermal treatment shows that samples with full MnFe2O4 begin to decompose at 600 °C. It was suggested that MnFe2O4 phase play a crucial role as thermal resistance black pigment.