Mixed-dimensional hierarchical configuration of 2D Ni_(2)P nanosheets anchored on 1D silk-derived carbon fiber for extraordinary electromagnetic wave absorption

Considering a series of electromagnetic pollution problems brought by the development of electronic communication technology,more attention has been paid to the research of electromagnetic wave(EMW)absorbing materials with unique composition and structure.Herein,under the inspiration of mixeddimensional hierarchical structure,2D Ni_(2)P nanosheets anchored on 1D silk-derived carbon fiber is successfully fabricated as a gratifying resistor-dielectric type absorber.By a controllable pyrolyzation strategy and disproportionated reaction,high-density 2D Ni_(2)P nanosheets were grown vertically and cross-linked on the surface of 1D silk-derived carbon fiber.The sample exhibited superior EMW absorption performance with maximum reflection loss value of–56.9 d B at the thickness of 2.32 mm and the effective absorption bandwidth can reach to 7.2 GHz at the thickness of 1.93 mm.In addition,the pure Ni_(2)P shows remarkable dielectric characteristic and EMW absorption ability as well.The integration of dualconductive loss,enhanced polarization relaxation loss and the multiple scattering in the composites was proved to contribute to the good EMW absorption performance.Therefore,this work confirms the great potentials of Ni_(2)P as a high-efficient EMW absorbing materials and light a new way in construction of multidimensional absorber.

Multiple α sub-variants and anisotropic mechanical properties of an additively-manufactured Ti-6Al-4V alloy

Additive manu facturing(AM)is a promising material processing method which gains significant momentum in the aerospace and biomedical industries.However,the anisotropy in the mechanical properties of additively-manufactured materials is still poorly understood.This study was aimed at elucidating crystallographic feature-anisotropy-mechanical property relationship for a Ti-6Al-4V alloy manufactured via selective electron beam melting(SEBM).Abundantαlamellae with six variants were present inside the columnar prior-βgrains with a<100>fiber texture duringβ→αphase transformation.The sixαvariants followed the Burgers orientation relationship of{110}_(β)//{0001}_(α)and<1-11>_(β)//<11-20>_(α).Multiple sub-variants in eachαvariant were observed for the first time.The anisotropy in the mechanical properties was mainly related to the relative amount of sixαvariants.While the horizontally-oriented samples had a lower yield strength,they exhibited a higher ductility and longer fatigue life than the vertically-oriented samples.Cyclic softening occurred at higher strain amplitudes,and cyclic stabilization sustained at lower strain amplitudes.Fatigue crack mainly initiated from the specimen surface at lower strain amplitudes,while multiple crack initiation tended to occur at higher strain amplitudes.Crack propagation was characterized by fatigue striations along with some secondary cracks.

Study of local environment of Cu atoms in Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy with different annealing temperature

The local environment of Cu atoms in Fe73.5Cu1Nb3Si13.5B9 alloy was investigated by extended X-ray absorption fine structure(EXAFS).Cu clusters began to order when the annealing temperature was around 733 K from the results of the Fourier transform curves.The fitting results showed that the first shell of the near fcc(face-centered cubic)Cu clusters only contained Cu atoms.The coordination number increased with the annealing temperature.Subsequently,the occupancy rate increased from 33.3%(annealed at 733 K)to 100% (annealed at 853 K).This local structural change of Cu atoms could probably affect the distribution of the bcc(body-centered cubic)α-Fe in Fe73.5Cu1Nb3Si13.5B9 alloy.