Preparation Of Ni-N, Fe-Ni-N Compounds And Evaluation Of Their Magnetic And Microwave Absorbing Properties

Magnetic metal nitrides have good corrosion resistance as well as high thermostability and saturationmagnetization, showing promising potential as a kind of new electromagnetic wave absorbing materials inhigh frequency region. However, little is currently available about magnetic metal nitrides. Thus in thepresent research we pay attention to commonly used magnetic metals Ni and Fe and adopt simlehigh-temperature nitridation method to prepare Ni-N and Fe-Ni-N compounds. The magnetic andelectromagnetic properties of as-fabricated Ni-N and Fe-Ni-N compounds were investigated. The maincontents and results are as follows:1. Fine Ni power was prepared by a liquid-phase reduction process with NiCl2, NaOH and hydrazinehydrate as the starting materials. As-obtained Ni powder was then used as a precursor to prepare a series ofNi-N compounds by high-temperature calcination under a flow of NH3. The crystal structure ofas-prepared Ni-N compounds was analyzed by means of X-ray diffraction, and their magnetic hysteresisloops, saturated magnetization as well as electromagnetic parameters were measured. It was found that Nipowder precursor is sequentially transformed into Ni/Ni₃N, Ni₃N, and Ni as the nitridation temperaturerises, while their saturated magnetization gradually declines therewith. Particularly, product Ni₃N exhibitsparamagnetism. In the meantime, the dielectric constant of the products obtained after nitridation remainsalmost unchanged as compared with that before intridation, but the nitrided products have greatly reducedmagnetic permeability. This indicates that pure phase Ni₃N is not a promising electromagnetic waveabsorption material.2. A precursor containing FeNi oxides as the major component was prepared via a hydrothermalreaction at high temperature with NiCl2, FeCl3, NaOH and hydrazine hydrate as the starting materials.As-obtained precursor was then calcinated at high temperature under a flow of NH3to prepare FeNiNcompounds with different Fe/Ni atomic ratio. The magnetic hysteresis loops, saturated magnetization aswell as electromagnetic parameters of as-fabricated FeNiN compounds were measured; and then theirreflection loss was calculated while the measured electromagnetic parameters were taken into account. Itwas found that as-fabricated FeNiN compounds with different Fe/Ni atomic ratio all possess highsaturation magnetization and low coercivity, which implies that they exhibit soft magnetism. In the meantime, all as-fabricated FeNiN compounds exhibit good electromagnetic wave absorbing performance,and in particular, Fe-Ni-N with a Fe/Ni atomic ratio2:1shows a reflection loss of as much as-17.5dB.3. A precursor was prepared via a high-temperature hydrothermal reaction with NiCl2, FeCl3, NaOH,hydrazine hydrate, and tetraethyl orthosilicate as the starting materials. As-obtained precursor was thennitrided at elevated temperature under a flow of NH3to afford Fe₂Ni₂N/SiO₂nanocomposite. The effect ofSiO₂on the magnetic and electromagnetic properties of Fe₂Ni₂N/SiO₂nanocomposite was investigated. Itwas found that as-fabricated Fe₂Ni₂N/SiO₂nanocomposite has zero coercivity and remanent magnetism,showing superparamagnetism. In the meantime, as-fabricated Fe₂Ni₂N/SiO₂nanocomposite possesses highmagnetic loss owing to high frequency nature resonance, showing promising potential as a microwaveabsorbing material in high frequency region.