Enhanced Microwave Absorption Properties by Tuning Cation Deficiency of Perovskite Oxides of Two-Dimensional LaFeO₃/C Composite in X-Band

Abstract

Development of microwave absorption materials with tunable thickness and bandwidth is particularly urgent for practical applications but remains a great challenge. Here, two-dimensional nanocomposites consisting of perovskite oxides (LaFeO) and amorphous carbon were successfully obtained through a one pot with heating treatment using sodium chloride as a hard template. The tunable absorption properties were realized by introducing A-site cation deficiency in LaFeO perovskite. Among the A-site cation-deficient perovskites, LaFeO/C (LFOC) has the best microwave absorption properties in which the maximum absorption is -26.6 dB at 9.8 GHz with a thickness of 2.94 mm and the bandwidth range almost covers all X-band. The main reason affecting the microwave absorption performance was derived from the A-site cation deficiency which induced more dipoles polarization loss. This work proposes a promising method to tune the microwave absorption performance via introducing deficiency in a crystal lattice.

Facile Preparation of Snowflake‐Like MnO2@NiCo2O4 Composites for Highly Efficient Electromagnetic Wave Absorption

“…Figures 1c and ds how the morphologies of NiCo 2 O 4 without MnO 2 as template under different magnification, and the self-assembled spiny balls couldb eo bserved.A ss hown in Figure 1e,t he NiCo 2 (OH) 6 nanoneedlesw ere uniformly distributed around the MnO 2 nanorods to form the MnO 2 @NiCo 2 O 4 precursor,a nd the lengths of the NiCo 2 (OH) 6 nanoneedlesw ere about 750 nm. Figures 1a and bs how the snowflake structure of the 1D MnO 2 nanorods crossing each other and the lengths of the nanorods were more than 30 mm.…”

“…Then NiCo precursor (NiCo 2 (OH) 6 )n anoneedles wered epositedu niformly on the surface of MnO 2 with the help of urea in ah ydrothermalp rocess. Firstly, snowflake-like MnO 2 (3 MnSO 4 ·H 2 O+ +2MnO 4 À !3SO 4 2À + +5MnO 2 (s)+ +H 2 O+ +4H + )i nteracted with Ni 2 + and Co 2 + through an electrostatic adsorption effect.…”

“…[4] Till now,v arious EMW absorption materials with different compositions and structures have been designed and prepared, such as one-dimensional (1D) mesoporous MoO 2 /C heteronanowires, [5] two-dimensional (2D) LaFeO 3 / C [6] and 2D Fe 3 C@NG/NC composites, [7] three-dimensional (3D) hierarchicalM oS 2 nanosheets/ultralongN -doped carbon nano-tubes [8] 3D SiO 2 @Fe 3 O 4 core-shell nanorod array/graphene architectures, [9] core-shell Fe 3 O 4 @MnO 2 composite microspheres, [10] hollow NiFe 2 O 4 particle/graphene hybrids, [11] etc. [4] Till now,v arious EMW absorption materials with different compositions and structures have been designed and prepared, such as one-dimensional (1D) mesoporous MoO 2 /C heteronanowires, [5] two-dimensional (2D) LaFeO 3 / C [6] and 2D Fe 3 C@NG/NC composites, [7] three-dimensional (3D) hierarchicalM oS 2 nanosheets/ultralongN -doped carbon nano-tubes [8] 3D SiO 2 @Fe 3 O 4 core-shell nanorod array/graphene architectures, [9] core-shell Fe 3 O 4 @MnO 2 composite microspheres, [10] hollow NiFe 2 O 4 particle/graphene hybrids, [11] etc.…”

“…The snowflake-like MnO 2 was synthesized by a hydrothermalm ethod, then 1D NiCo 2 (OH) 6 nanoneedles were obtainedo nt he surfaceo fM nO 2 throughahydrothermal methodb yu sing MnO 2 as template, followed by as imple thermal annealing process to afford MnO 2 @NiCo 2 O 4 composites, which displayed an enhanced EMW absorption performance comparedw ith pure MnO 2 and NiCo 2 O 4 due to au nique coreshell structure, good impedance matching,a nd high dielectric loss. The snowflake-like MnO 2 was synthesized by a hydrothermalm ethod, then 1D NiCo 2 (OH) 6 nanoneedles were obtainedo nt he surfaceo fM nO 2 throughahydrothermal methodb yu sing MnO 2 as template, followed by as imple thermal annealing process to afford MnO 2 @NiCo 2 O 4 composites, which displayed an enhanced EMW absorption performance comparedw ith pure MnO 2 and NiCo 2 O 4 due to au nique coreshell structure, good impedance matching,a nd high dielectric loss.…”

“…The phenomenons hould be attributedt ot he transformation of NiCo 2 (OH)6 to NiCo 2 O 4 andthe evaporation of produced water from the reaction [Eq. 20-0781).…”