(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B:A novel high-entropy monoboride with good electromagnetic interference shielding performance in K-band

摘要

A novel equimolar high-entropy(HE)transition metal monoboride,(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B,was designed and prepared in powder and bulk form by high temperature elemental reaction method and spark plasma sintering(SPS)method,respectively.XRD analysis shows that HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B possesses orthorhombic structure with Pnma space group.Through Rietveld refinement,the lattice parameters of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B are a=5.6675,b=2.9714,c=4.2209 and the theoretical density is 6.95 g/cm~3.The Vickers hardness and electrical conductivity of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with relative density of 90%is 12.3±0.5 GPa and 0.49±0.04×10~6 S/m,respectively.Due to high electrical conductivity,HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B bulk with 3.0 mm thickness displays superior EMI shielding performance in 18.0–26.5 GHz(K-band),and the average values of SET,SER,and SEAare 23.3 dB,13.9 dB,and 9.4 dB,respectively.The EMI shielding mechanism of HE(Cr_(0.2)Mn_(0.2)Fe_(0.2)Co_(0.2)Mo_(0.2))B mainly results from reflection.