Analysis and Design of Absorbers for Electromagnetic Compatibility Applications

Absorbers are one of the key components in the realm of electromagnetic compatibility. Depending on the frequency range of interest, different types of absorbers can be utilized for this purpose. This chapter introduces the analysis and modeling of ferrite-based absorbers for low-frequency applications (below 1 GHz) and discusses the issues encountered in their installation, resulting in air gaps. Later, different kinds of pyramidal absorbers, commonly used in the broadband microwave frequency range (above 1 GHz), are presented, and analytical and numerical approaches for predicting their performance are reviewed. The combination of the ferrite tile and pyramidal dielectric absorbers is also provided. Then, some practical aspects of designing hybrid absorbers, including the influence of carbon loading and matching layer on their performance, are mentioned. Finally, the absorber operating frequency extension to the millimeter-wave spectrum using metamaterial structures or graphene material is presented.

Risk analysis and solution of using graphene: Material, synthesis, and application (Mini review)

Graphene is a nanomaterial with unique physical and chemical properties. The two-dimensional hexagonal sp2 structure in the honeycomb lattice has high thermal conductivity, high electricity, mechanical strength, and large surface area. The nano properties are significantly different from the bulk material. The review of the material, synthesis and application aspects of graphene gave rise to risk analysis in each field of study. Graphene material does not yet have adequate information regarding the risk of danger. Because graphene is nano-sized, this material can enter the human body through inhalation, ocular, cutaneous and oral. Graphene synthesis involves using chemicals that will produce hazardous products and reduce agents with high toxicity. The risk becomes more and more when the challenges of mass production of graphene are faced. Graphene can be applied as sensors, nanoelectronics, and biomedical applications. In this biomedical application, graphene has direct contact with humans and can increase reactive oxygen species in the body. The recommendation to overcome the risk is to use personal protective equipment and handle graphene material properly. The toxic materials involve in the synthesis step can be replaced with other environmentally friendly materials. Antidotes substances can reduce the toxicity of graphene materials so that the risks graphene in its application can be overcome.

Implementation of 20 nm Graphene Channel Field Effect Transistors Using Silvaco TCAD Tool to Improve Short Channel Effects over Conventional MOSFETs

In recent years, demands for high speed and low power circuits have been raised. As conventional metal oxide semiconductor field effect transistors (MOSFETs) are unable to satisfy the demands due to short channel effects, the purpose of the study is to design an alternative of MOSFETs. Graphene FETs are one of the alternatives of MOSFETs due to the excellent properties of graphene material. In this work, a user-defined graphene material is defined, and a graphene channel FET is implemented using the Silvaco technology computer-aided design (TCAD) tool at 100 nm and scaled to 20 nm channel length. A silicon channel MOSFET is also implemented to compare the performance. The results show the improvement in subthreshold slope (SS) = 114 mV/dec, ION/IOFF ratio = 14379, and drain induced barrier lowering (DIBL) = 123 mV/V. It is concluded that graphene FETs are suitable candidates for low power applications.

Studies on Carbon Materials Produced from Salts with Anions Containing Carbon Atoms for Carbon Paste Electrode

In the presented work, the properties of carbon materials obtained in the reaction of sodium bicarbonate (C–SB) and ammonium oxalate (C–AO) with magnesium by combustion synthesis were investigated. For the materials obtained in this way, the influence of the type of precursor on their properties was analyzed, including: Degree of crystallinity, porous structure, surface topography, and electrochemical properties. It has been shown that the products obtained in magnesiothermic process were found to contain largely the turbostratic carbon forming a petal-like graphene material. Both materials were used as modifiers of carbon paste electrodes, which were then used to determine the concentration of chlorophenol solutions by voltammetric method. It was shown that the peak current determined from the registered differential pulse voltammograms was mainly influenced by the volume of mesopores and the adsorption capacity of 4-chlorophenol for both obtained carbons.