Characterization of a polyaniline/pre-oxidized fiber felt electromagnetic wave absorbing composite

Firstly, a polyaniline/pre-oxidized fiber felt composite was prepared by in situ polymerization using pre-oxidized fiber felt as the substrate, aniline as the monomer, ammonium persulfate as the oxidant, and p-toluenesulfonic acid as the dopant. Secondly, the electromagnetic wave absorbing property and tensile property of the polyaniline/pre-oxidized fiber felt composite were investigated. Finally, the structure and composition were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and differential scanning calorimetry. The results show that the reflection loss of the polyaniline/pre-oxidized fiber felt composite is the smallest at the 3000 MHz frequency, reaching –8.23 dB, and the average surface resistance is 2059.84 Ω, with good conductivity. The characterization analysis shows that polyaniline has been successfully loaded on the pre-oxidized fiber felt, and the protonation reaction occurs at the nitrogen atom on the imine -N-. The polyaniline structure is doped by p-toluenesulfonic acid with a certain degree of order and crystallinity, and the composite has good thermal stability.

Preparation and Characterization of PU/PET Matrix Gradient Composites with Microwave-Absorbing Function

In the field of microwave-absorbing materials, functional powder has always been the focus of research. In order to fabricate lightweight and flexible garment materials with microwave-absorbing function, the current work was carried out. Firstly, the general properties of polyurethane (PU) matrix composites reinforced with various microwave-absorbing powders were studied, and the carbon nanotubes (CNTs)/Fe3O4/PU film was proven to have the best general properties. Secondly, the needle-punched polyester (PET) nonwoven fabrics in 1 mm-thickness were impregnated into PU resin with the same composition of raw material as Fe3O4/CNTs/PU film, thereby the microwave-absorbing nonwovens with gradient structure were prepared. Moreover, the absorbing properties of the CNTs/Fe3O4/PU/PET gradient composites were tested and analyzed. Finally, the relationship between the mass ratio of CNTs and Fe3O4, and the microwave-absorbing properties was studied. The results show that the mass ratio of CNTs/Fe3O4 has a significant effect on the microwave-absorbing property of CNTs/Fe3O4/PU/PET. When the mass ratio of CNTs/Fe3O4 is 1:1, the prepared CNTs/Fe3O4/PU/PET gradient composite can achieve effective reflection loss in the range of more than 2 GHz in Ku-band (12–18 GHz), and the minimum reflection loss reaches −17.19 dB.

Advancements in Geo-Inclusions for Ballasted Track: Constitutive Modelling and Numerical Analysis

This paper reviewed some salient features evolving through mathematical and numerical modelling of ballasted track components incorporating recycled rubber products. Firstly, a constitutive model based on the bounding surface concept was introduced to simulate the shear stress-strain response of waste mixtures (i.e., recycled rubber crumbs, coal wash, and steel furnace slag) used for the capping layer placed below the ballast medium, whereby the energy absorbing property resulting from the inclusion of different amounts of rubber has been captured. Subsequently, key research findings concerning the inclusion of recycled rubber mats on ballasted tracks for reduced particle degradation under cyclic loading were examined and discussed. Discrete element modelling (DEM) coupled with Finite element modelling (FEM) to micro-mechanically characterise ballast behaviour with and without rubber mats offers invaluable insight into real-life track operations. In particular, this coupled DEM-FEM model facilitates the exploration of micromechanical aspects of particle breakage, contact force distributions within the granular assembly, and the orientation of contacts during cyclic loading.

Effect of Temperature on the Microwave-Absorbing Properties of an Al2O3–MoSi2 Coating Mixed with Copper

To obtain a high temperature-resistant microwave absorbing coating, an Al2O3–MoSi2/Cu composite coating was prepared by atmospheric plasma spraying. Compared with a normal temperature environment, there are a few reports on Cu as an absorbent for high temperature microwave absorbing coatings. Therefore, in this regard, wave absorbing property can be improved by using a Cu absorbent. The microstructure of a Al2O3–MoSi2/Cu coating was observed, and the dielectric properties of the composite coating in the high-temperature environment of the X-band were tested. The experimental results show that with the increase in temperature, Cu transforms Cu2O in the high-temperature environment and improves the coating’s wave absorption performance with MoSi2. In addition, a 1.4 mm-thick coating showed best microwave absorbing performance at 700 °C. The reflection loss was −19.09 dB, and the effective microwave absorbing bandwidth was 2.83 GHz (Reflection Loss < −10 dB). It was found that the Al2O3–MoSi2/Cu composite coating has good wave-absorbing performance in a 700 °C high-temperature environment.

In vitro biocompatibility study of microwave absorbing conducting polymer blend films for biomedical applications

In the present communication, microwave absorbing property in the frequency range of 12.4–18 GHz and in vitro biocompatibility studies of light weight, flexible, biocompatible, and environment friendly polymer blend films of polyvinylchloride (PVC)-polyvinylpyrrolidone (PVP) (taken in ratio 1:1) and doped with various percentage weight concentration of polypyrrole (PPy) are reported. Addition of PPy in the PVC-PVP matrix exhibited a synergetic effect in improving microwave absorbing property. PVC-PVP blend film with 40 and 50% concentrations of PPy were seen to absorb microwaves of the order of 28–50 dB in ku band of microwave region indicating that this composition can suitably find application as microwave absorbing material. In vitro biocompatibility skin irritation study of PVC-PVP (taken in ratio 1:1) with 50% weight concentration of PPy indicated that the prepared film did not have any irritation upon administration and hence is safe for topical application. Moreover, the blood compatibility study of this film exhibited compatibility with blood and can safely be used in any blood contacting mask/device. Hence, this biocompatible film can potentially be used as microwave absorbing material for masking some parts of human body or can be interfaced to biological systems or devices.