Electromagnetic Wave-Absorbing Property and Mechanism of Cementitious Composites with Different Types of Nano Titanium Dioxide

Ten types of nano TiO2 (NT) were used to endow cementitious composites with the electromagnetic absorbing property. The influences caused by sample thickness, the size, and surface treatment of NT on the electromagnetic absorbing performance of cementitious composites in the frequency of 2–18 GHz were compared. Results showed that the electromagnetic wave-absorbing property of NT-modified cementitious composites increases with the increasing thickness of the sample. When the sample thickness is 20 mm, the cementitious composite incorporated with 1,500- nm rutile NT exhibits the best absorbing performance with a reflectivity of −29.29 dB in Ku (12.5–18 GHz) band, which is 242.97% higher than that of control cementitious composites. Compared with untreated NT, mixed crystal NT, TiO2@SiO2, and TiO2@Al2O3@SiO2 have a better enhancement effect on the electromagnetic wave-absorbing properties of cementitious composites. Through analyzing the dielectric constant and magnetic permeability of cementitious composites, it can be proved that the electromagnetic-absorbing properties of cementitious composites with NT are governed by dielectric loss rather than magnetic loss.