Sureface Magnetic Modification And Microwave Absorbing Properties Of Micro/Nano-mineral Powder

In this work, micro/nano-mineral powder-attapulgites and cenospheres were magnetized through co-precipitation treatment after purification and surface treatment. The phase composition, element status, microstructure and microwave absorption capacity of the samples were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vector network analyzer (VNA), respectively. The results indicated that the modified samples exhibited excellent microwave absorption capacityThe process is simple, low-cost and suitable for large-scale industrial production. This study provides a new way for the selection and design of microwave-absorbing materials and explores a new route to the application of micro-nano mineral powders in high-tech fields.The purification and dispersion of attapulgite are shown as following:Sodium pyrophosphate was used as the dispersant to add into attapulgite clay, after wet mechanical milling and post-centrifugal separation, most of the impurities were removed and single-crystal nanorods attapulgitewere obtained, which measure about 10～50nm in diameter and 0.2～0.8μm in length.Fe3O4-attapulgite (Fe3O4-ATP) magnetic nanoparticles were fabricated by the co-precipitation method in an aqueous suspension of attapulgite pre-modified with FeCl2. The FeCl2 solution was added to the purified attapulgite (6g/L) when a proper PH, temperature and time of the reaction were adjusted. The TEM observations revealed that the Fe3O4 magnetic particles had grown on the surface of the ATP needles with a diameter distribution ranging from 10-80 run.The microwave absorption capacity of Fe3O4-ATP was measured by a vector network analyzer. It was found that when the thickness of all samples reached a critical value, their optimal reflection loss (RL) was more than -15dB, the optimal absorption frequency band can be designed by adjusting the thickness of the absorber, in order to satisfying the practical requirements.NaOH and NH4F solution were used successively to activate and coarsen the surface of cenospheres. Fe3O4-FAC was also fabricated by the similar co-precipitation method mentioned above. The VNA results indicated that the samples with different thickness had excellent microwave absorbing properties. The biggest reflection loss (RL) could be about-21 dB at 12.1GHz with a layer thickness of 3.5 mm and the reflection loss (RL) of this samples were more than-10dB in the frequency range of 10.8-15.1 GHz.