Synthesis Of Iron Fibers And Its Alloy Fibers Prepared By Thermal Decomposition-Oxidation-Deoxidization Of Gel Precursor

In this article, Fe, Fe-Co and Fe-Ni magnetic fibers are prepared by thermal decomposition-oxidation-deoxidization method of gel precursor fibers. When ferric citrate, metal salt and ammonia are used as raw materials, the sol which has good spinnability can be synthesized by complex reaction. After dry spinning, the sol is turned into precursor fibers. Then after gelation and thermal decomposition, Fe,Fe-Co and Ni-Fe fibers can be got. Using FT-IR,the analysis of elemental content,SEM,XRD,TG-DTA, The factors influencing the spinnability of the sol are studied,the molecular structures of the precursor is deduced, the crystal structure,the elemental composition,the morphology of fibers which are prepared in different condition are studied in the phase of thermal decomposition; The electromagnetic parameters of metal and alloy fibers are tested with the Vector Network Analyzers.The research shows that the sol has good spinnability when the PH of the reaction is 7.0, the reaction temperature is 50℃and the concentration of ferric citrate is 0.5~1.0mol/L. After dry spinning and gelation, the gel fibers containing ferric element can be got, and they are turned into Fe2O3 fibers when they are calcined for five hours in tubular furnace (440℃). Then they are turned intoα-Fe fibers when they are deoxidized for 2.5h in hydrogen atmosphere (650℃), and the content of Fe element is 90.65%. But in both oxide fibers and Fe fibers, there are a lot of cracks and holes. First, the pyrogenation of gel fibers in N2 atmosphere; Then after the oxidation-deoxidization process, the purity of Fe fibers is improved to 93.27%, the content of carbon decreases to 0.41% and the content of nitrogen decreases to 0.62%. At this time, there are no obvious cracks and holes, and the compactness of the fibers is better.Using nickel carbonate basic, cobaltous carbonate basic and ferric citrate as raw materials, the sol with different ratios of Fe and Co or Fe and Ni element is prepared. After thermal decomposition in nitrogen atmosphere and the oxidation-deoxidization process, the precursor fibers are turned into Fe-Co and Fe-Ni fibers. The research implies that Fe-Co gel fibers with different Co content are all turned into substituting solid solution. Fe-Ni gel fibers with different Ni content are all turned into the mixture ofα-Fe and Fe0.64Ni0.36 when Ni/Fe is less than 1/2. When Ni/Fe is 1/2, the deoxidization outcome is Fe0.64Ni0.36 which has the single structure.The research on microwave capability of fibers prepared in different conditions implies that when the experimental frequency is 2~18GHz,ε″and the complex permeabilityμincrease obviously as the purity of Fe fibers is higher. The maximum ofμ′is 2.22 when the frequency is 2GHz, and the maximum ofμ″is 0.61 when the frequency is 11.6GHz. The complex permeabilityμand the complex permittivityεof Fe-Co and Fe-Ni fibers decrease as the tested frequency increases, and they manifest much better dispersive character of wave. The absorption peak value ofμ″moves to high frequency as the content of Co or Ni decreases. After simulation, the absorption band of Fe-Co and Fe-Ni fibers has the wider trend than Fe fibers.