Metal Oxide/Nitrogen-Doped Carbon Nanosheet Heteronanostructures as Highly Efficient Electromagnetic Wave Absorbing Materials

In this paper, we will discuss the excellent broadband microwave absorption behaviors of Cu/CuO/carbon nanosheet composites: traces of copper and oxide embedded in a carbon nano-sheet not only cut down the high permittivity of adsorbs but also induce more interfacial polarization centers. The results showed that at a cracking temperature of 900 °C, the fabricated material has a unique ripple-like structure, which promotes the hierarchical interfacial polarization. The prepared material has a maximum absorption bandwidth of 4.48 GHz at an exceedingly thin thickness of 1.7 mm and a maximum reflection loss of −25.3 dB at a thickness of 2 mm. It is a relatively ideal material for electromagnetic wave absorption.

A high-performance eletromagnetic wave absorption material based on biochar derived from pomelo peel

As a kind of renewable resources with abundant reserves, research on the utilization of biochar has been paid more and more attention. However, the use of pomelo peel biomass carbon in the field of eletromagnetic wave absorption (EWA) has never been reported. In this study, the pomelo peel of natural recovery were carbonized at temperature of 700°C for 1 h in a high vacuum of 300 pa. The as-prepared biomass carbon were uniformly mixed with the paraffin by heat-assisted impregnation to prepare small ring-shaped devices, and the EWA characteristics of the small devices were investigated. The absorbing measurements were performed with the filling mass fraction of 30% and 50% of the biochar, respectively. The biochar with a mass fraction of 50% showed the excellent absorbing properties with the maximum reflection loss up to –44.3 dB at 9.84 GHz in the thickness of 2.0 mm, which is expected to be used as light, broadband and efficient EWA material.

Preparation and Microwave Absorbing Properties of Natural Ferrites from Corrosion Product as Radar Absorber Materials in X-Band

Rust is the by product of oxidation on ferrous metal. Rust is extremely harmful and can’t be avoided. Due to that reason for added values on rust a research titled utilizing corrosion product as absorber for microwave on X-band frequency is done. This research goals are to determine the ability of rust to absorb radar waves by maximum reflection loss values. The study was conducted by taking a powder natural ferrites of rust from corroded ferrous metal in Surabaya, Malang, Bangkalan and then later separated by using a 0.1 T hard magnet. The XRF, XRD and VSM characterization showed that rust powder sample has chemical compound of ferrites (Fe3O4) with magnetite phase and a soft magnetic with Ms = 8 emu/g. Based on the measurement microwave absorbing by VNA showed that maximum reflection loss of natural ferrites Surabaya, Malang, Bangkalan respectively-20.15 dB, -12.64 dB and-6.75 dB, at matching frequency 11 GHz and width frequency 3 GHz.

Microstructure and Microwave Absorption Characteristics of BaTiO3-CoFe2O4 Composites

Magnetic and dielectric phases like CoFe2O4 and BaTiO3 are both intrinsically capable of absorbing electromagnetic waves. The characteristics of the two phases in a composite structure to obtain the combined effect of the existence of phases as composite components have been investigated. Observation of the microstructure of composites with the composition (1-x)BaTiO3-(x)CoFe2O4 has shown the compact structure of composite sample with an increased the mass density with increasing value of x. No changes in lattice constant of each phase in the composite structure. This ensures that no complete or partial substitution between the ions of each phase has occurred. However, the presence of a material phase in the composite structure influenced the crystallite growth behavior of each phase. The mean crystallite size of the two phases tends to increase, but grew with a different rate. The saturation magnetization value of the composite samples is composition dependent. The value of remanent magnetization and coercivity increases with increasing values of x. All composite samples based on the results of data evaluation data taken by a vector network analyzer (VNA) in X-band frequency, shows the ability to absorb electromagnetic waves in all X-band frequencies. Composite composition determined the peak frequency that gives the maximum reflection loss value. The largest maximum reflection loss value is-40 dB occurring at a frequency of 10.98 GHz from samples with a composition x = 0.5. In conclusion, the composite of CoFe2O4/BaTiO3 system composite can be a promising candidate for electromagnetic wave dampers when the composite is properly designed.

Mechanical Exfoliation of Reduced Graphene Oxide From Old Coconut Shell as Radar Absorber in X-Band

The purpose of this study is to determine the effect of heating temperature and the chemical exfoliation process on the reflection loss of r-GO synthesized from coconut shell. The heating process is carried out at temperature of 400°C and 700°C. The chemical exfoliation process is carried out by adding 1M H2SO4 solution in a ratio of 1: 1, 1: 5, and 1:10. Then, the process of washing is done using an ultrasonic cleaner. The XRD pattern indicates that coconut shell charcoal has formed the r-GO phase. In the chemical exfoliation process with the addition of 1M H2SO4 solution in a ratio of 1: 10 at a temperature of 400°C, it shows that the maximum reflection loss is -7.186 dB at 10.48 GHz with an electrical conductivity of 1.075 x 10-3 S/cm.

Excellent microwave absorption properties based on a composite of one dimensional Mo2C@C nanorods and a PVDF matrix

A Mo2C@C/PVDF composite with excellent absorption performance has been synthesized. The results indicate that the maximum reflection loss can reach −39.0 dB, and the absorbing bandwidth is up to 3.1 GHz at a thickness of 2.0 mm.

Nanocomposites Fe/Activated Carbon/PVA for Microwave Absorber: Synthesis and Characterization

Nanocomposites, activated carbon/polyvinyl alcohol (AC/PVA) filled with Fe to form Fe/AC/PVA, were characterized by using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and vector network analyzer (VNA). The crystal orientations from Fe are (104), (110), and (200) and the bonding formations of AC are O-H, C-H, and C=C show existence in nanocomposites, which may be due to the Fe that has been filled the pore of AC via a chemical bond. 20% AC (3 mm in thickness) in nanocomposites shows higher performance absorption for C-band (4.65 GHz) with maximum reflection loss of −32.5 dB.

Fabrication and electromagnetic performance of talc/NiTiO 3 composite

In this study, the electromagnetic (EM) performance of talc/NiTiO 3 composite was evaluated. The morphology of talc displayed a lamella structure; there were many nanoparticles of NiTiO 3 coated on the talc lamella . Thermal destruction occurred, which increased the surface area from 2.51 m 2 g −1 to 79.09 m 2 g −1 at the calcined stage at 650°C. The presence of NiTiO 3 increased dielectric loss and magnetic loss of talc. The calculation of EM wave absorption of talc/NiTiO 3 obtained a maximum reflection loss of −11.94 dB at the thickness of 6.85 mm; the optimum thickness for microwave absorption is 6.3–7.3 mm. This study revealed a new approach for fabricating an EM absorber and broadening applications of both talc and NiTiO 3 in EM absorption.

Facile synthesis of porous Fe3O4@C core/shell nanorod/graphene for improving microwave absorption properties

Porous Fe3O4@C core/shell nanorods decorated with reduced graphene oxide were synthesized by a facile one-pot method, and exhibit high microwave absorption performance: maximum reflection loss reaches −48.6 dB.

Synthesis, Magnetic and Electromagnetic Absorption Properties of Amorphous Core-Shell Fe-B@SiO2 Submicrospheres

Amorphous core-shell Fe-B@SiO2 submicrospheres with the SiO2 shell layer of about 18 nm were fabricated via a two-step process. Fe-B submicrospheres were first obtained, and core-shell Fe-B@SiO2 submicrospheres were subsequently fabricated using TEOs as a Si source through a modified Stöber method. The measurements of the magnetic properties demonstrated that the amorphous core-shell Fe-B@SiO2 submicrospheres exhibit ferromagnetic behavior at room temperature. The maximum reflection loss reaches −24.8 dB at 11.76 GHz for the absorber with thickness of 2.2 mm. The absorption bandwidth with the reflection loss below −10 dB is up to 14.76 GHz for the absorber with a thickness of 1.5-6 mm and the absorption bandwidth with the reflection loss below −20 dB is up to 6.6 GHz for the absorber with a thickness of 1.8-3.1 mm. Our results demonstrates that the amorphous core-shell Fe-B@SiO2 submicrospheres obtained in this work are attractive candidate materials for the magnetic and EM wave absorption applications.