Infrared radiation properties of La3Ni2O7 and performance of the La3Ni2O7-based coating considering the effect of thermal reactivity

Materials with excellent infrared radiation properties are important for preparing infrared radiation coatings that are applied in industrial furnaces, to improve the efficiency of heating equipment. To find a new material with better infrared radiation performance, La3Ni2O7, a layered perovskite structural material, was prepared by the sintering method, and its infrared radiation performance was studied in detail. It was found that La3Ni2O7 has excellent infrared radiation properties, and the measured emissivity values at the 3–5 μm waveband were above 0.970, which was determined by its narrower forbidden bandwidth. Furthermore, La3Ni2O7-based coatings on clay brick substrates were prepared. The thermal behavior of the coatings, from room temperature to 1400 °C, was studied using thermogravimetry and differential scanning calorimetry (TG-DSC). The results indicated that a series of reactions occurred for the coatings at temperatures higher than 1000 °C. Furthermore, the coatings were heated in a muffle furnace at 1000 °C, 1100 °C, and 1200 °C, for 60 min to study the effect of thermal reactivity on the infrared radiation performance of the coatings. The results showed that at high temperatures, although the thermal reactivity led to a phase change for the coatings, the change had little effect on the emissivity. Above 1100 °C, La3Ni2O7 starts to decompose into La2NiO4 and NiO, and above 1200 °C, the La2NiO4 content is above 50%, implying that the decomposition product La2NiO4 plays a key role in maintaining the high emissivity of the coatings. The emissivity of La2NiO4 specifically fabricated was tested and it was found that its emissivity was above 0.970. Furthermore, thermal shock resistance tests of the coatings were conducted. The results showed that the transition layer was formed by the chemical reactions between La3Ni2O7 and the oxides in the substrate, which plays a positive role in prolonging the service life of the coating.