We report a simple, consistent, and economical wet-chemical method for synthesizing a series of Fe-Ni nanocomposites by varying Fe and Ni fractions. Further, graphite wrapped Fe-Ni alloy nanoparticles in core-shell geometries are prepared by calcination of nanocomposites at 900°C under N₂ gas. XRD studies reveal body-centered and face-centered (bcc/fcc) cubic Fe-Ni alloy core particles and hexagonal graphitic shell formation. More interestingly, a structural transition from bcc to fcc phase is also investigated with varying Ni concentration. The microstructural studies demonstrate ~10 nm graphitic shells together with a nearly spherical ~40 nm diameter Fe-Ni metallic core. These magnetic alloys showed the variation in magnetization and coercive fields with alloy compositions. The Fe-Ni core-shell material with the maximum magnetization is used for fabricating rubber-based composites by varying filler loading in the range 60–80 wt%. The utility of Fe-Ni/C alloy and rubber composite is categorized in terms of electromagnetic impedance matching for the entire X-band (8.2–12.4 GHz) frequency range based on the filler concentration and absorber thickness for microwave absorption applications. These core-shell alloy systems may show potential for stealth of strategic targets because of their very low density (~1.1 g/cc) and lesser thickness than conventional absorbers.

我们报告了一种简单，一致且经济的湿化学方法，可通过改变Fe和Ni含量来合成一系列Fe-Ni纳米复合材料。此外，通过在900°C下在N ₂下煅烧纳米复合材料，制备了核-壳几何形状的石墨包裹的Fe-Ni合金纳米颗粒气体。XRD研究表明，体心和面心（bcc / fcc）立方铁镍合金芯颗粒和六角形石墨壳形成。更有趣的是，还研究了Ni浓度变化时从bcc相到fcc相的结构转变。微观结构研究表明，约10 nm的石墨壳以及直径约40 nm的近似球形的Fe-Ni金属核。这些磁性合金显示出合金成分的磁化和矫顽场的变化。具有最大磁化强度的Fe-Ni核-壳材料可通过在60-80 wt％的范围内改变填料含量来制造橡胶基复合材料。Fe-Ni / C合金和橡胶复合材料的用途按整个X波段的电磁阻抗匹配进行分类（8.2–12。4 GHz）频率范围基于填充剂浓度和微波吸收应用中的吸收体厚度。这些核-壳合金系统由于其非常低的密度（〜1.1 g / cc）和比常规吸收器更薄的厚度，因此可能显示出潜在的战略目标。