Regulating pH value synthesis of NiCo₂O₄ with excellent electromagnetic wave absorbing performance

In last several decades, electromagnetic wave (EMW) absorbing materials have attracted much attention because of their ability to attenuate EMW and reduce the electromagnetic pollution caused by the rapid development of information technology. Among many electromagnetic wave absorbers, nickel cobaltite (NiCo₂O₄) stands out for its excellent electromagnetic wave absorbing performance. However, as the most commonly used synthesis method of NiCo₂O₄-based materials, hydrothermal method is time-consuming and complicated, which hinders the actual production and application of nickel cobaltite. In this work, agglomerate NiCo₂O₄ of lamellar accumulation was prepared by chemical coprecipitation and calcination with oxalic acid as precipitant. The effect of pH control on the properties of product was studied by adding ammonia to change the microenvironment of coprecipitation system. When the pH value of the coprecipitation system is 7, the absorbent has been prepared successfully which has broad absorption bandwidth of 6.26 GHz (11.74–18 GHz) and ultrathin matching thickness of 1.58 mm. The synthesis method is simple, convenient, time-saving and energy-saving, and the product has excellent electromagnetic wave absorption capacity, which has a good industrial application prospect.