In this study, novel quaternary MWCNT/CuO/Fe3O4/PANI nanocomposites were synthesized with three different weight ratios of CuO/Fe3O4/PANI to MWCNT (1:3), (1:4), and (1:5), where all of its components were synthesized separately and then combined in specific weight ratios. CuO/Fe3O4/PANI transmission electron microscopy (TEM) images revealed that most nanoparticles were in a CuO/Fe3O4 hybrid form, with a narrow size distribution uniformly dispersed in a polymer background. The TEM and scanning electron microscopy (SEM) images of the MWCNT/CuO/Fe3O4/PANI nanocomposite revealed that the MWCNT was uniformly coated with CuO/Fe3O4/PANI. All three nanocomposites samples demonstrated superior microwave attenuation performance in terms of reflection loss and absorption bandwidth. The minimum reflection losses for MWCNT/CuO/Fe3O4/PANI nanocomposites (1:3), (1:4), and (1:5) were 45.7, 58.7, and 85.4, 87.4 dB, respectively. The absorption bandwidths (RL ≤ −10 dB) of MWCNT/CuO/Fe3O4/PANI nanocomposites (1:3), (1:4), and (1:5) were 6, 7.6, and 6 GHz, respectively.

The bi-alkali pnictogens have attracted significant attention for optoelectronic and photocathodic device applications. However, in most of the compounds belonging to this family, there has been less effort put into investigating the mechanical properties and topological phase transitions (TPT) of the compounds. Here, in the framework of density functional theory, the mechanical properties and topological phase transition of NaLi2Bi under hydrostatic pressures are investigated. Elastic constants and phonon calculations have shown the mechanical and dynamical stability of this compound under hydrostatic tension and compression. The analysis of the elastic constants show that the NaLi2Bi in the equilibrium state is an auxetic material with a negative Poisson’s ratio of -0.285, which changes to a material with a positive Poisson’s ratio under hydrostatic tension. Meanwhile, Poisson’s ratio and Pugh ratio indicate that this compound has brittle behavior and maintains it under hydrostatic pressures. The calculated results of the band structure within the generalized gradient approximation (GGA) (Tran-Blaha modified Becke-Johnson exchange potential approximation (TB-mBJ)) show that NaLi2Bi is a nontrivial topological material (trivial topological material). It was found that hydrostatic compression (tension) in the GGA (TB-mBJ) approach leads to a transition from a nontrivial (trivial) to a trivial (nontrivial) topological phase for this compound. Moreover, the calculated Wannier charge centers confirm the TPT. Identifying the mechanisms controlling the auxetic behavior and TPT of this compound offers a valuable feature for designing and developing high-performance nanoscale electromechanical and spintronic devices.