Preparation Of Light Ferrite And Its Application In Wave Absorbing Gypsum Board

Building is the main place to human production and life. Electromagnetic protection technology can be used on building in order to reduce the electromagnetic pollution. Cementing materials is the most widely used construction materials. The simple and feasible method to meet the requirements of absorption of electromagnetic waves is adding absorbing agent into the cementing material. The addition of ferrite in cementing materials was beneficial to the improvement of absorbing properties. Because of the high density of ferrite, there are problems that the quality of ferrite was big and and the mechanics performance of cementing materials decreased to achieve certain absorbing performance. Light ferrite absorbing agent has good compatibility with gypsum was prepared and its effect on the gypsum board performance was studied in this paper.The nickel zinc ferrite precursor was loaded on diatomite, cenosphere and wood powder respectively by sol-gel method. The composite precursor powders were heat treated under different calcination system and the lightweight ferrite was prepared. The XRD, SEM, DSC-TG, IR, density and electromagnetic parameter test were employed to analyse the ferrite. The chemical properties and electromagnetic effects of lightweight ferrite were studied in different precursor solution p H, nickel/ zinc ratio and calcination system.Results show that the diatomite/nickel zinc ferrite and cenosphere/nickel zinc ferrite has core-shell structure, the coating layer which has spinel structure combined with the matrix solidly. The wood powder/nickel zinc ferrite shows porous structure. The density of diatomite/nickel zinc ferrite is 3.2³.8 g/cm³, the cenosphere/nickel zinc ferrite is 2.8³.3 g/cm³, and density of wood powder/nickel zinc ferrite is about 1 g/cm³. In the frequency range of 0-1000 MHz, the electromagnetic loss tangent values?tan?? of diatomite/Ni_0.5Zn_0.5Fe₂O₄ is 0.05 to 0.3 and the tan? of cenosphere/Ni_0.5Zn_0.5Fe₂O₄ is about 0.05 to 0.05. Within the frequency of the 2¹8 GHz, the tan? value of the diatomite/Ni_0.5Zn_0.5Fe₂O₄ is between 0.02 to 0.15, and the cenosphere/Ni_0.5Zn_0.5Fe₂O₄ is 0.01 to 0.1, and wood powder/nickel zinc ferrite is between 0.1 to 0.35.Diatomite/Ni_0.5Zn_0.5Fe₂O₄ and cenosphere/Ni_0.5Zn_0.5Fe₂O₄ which has excellent performance and proper density was added into the gypsum respectively. The influence of ferrite content on absorbing and mechanical properties of the gypsum based composite absorbing material was studied. Results show that when the content of diatomite/Ni_0.5Zn_0.5Fe₂O₄ is 15%, bending strength decreased by 18%, and compressive strength increased by 13%, and the reflectivity can reach to-6 d B in 12 GHz. When the content of cenosphere/Ni_0.5Zn_0.5Fe₂O₄ is 15%, the flexural strength of gypsum decreased by 25%, and the compressive strength increased by 15.4%, and the reflectivity can reach to-6.2 d B in 11.7 GHz.