# The Comparison of Microwave Reflectance of Graphite and Reduced Graphene Oxide Used for Electronic Devices Protection

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Graphite

_{2}SO

_{4}. A major limitation in the practical applications of graphite is its poor magnetic properties. This problem can be solved by mechanically combining graphite with iron compounds, which results in a synergistic effect and gives graphite magnetic properties, increasing its electromagnetic efficiency in the microwave area.

## 3. Reduced Graphene Oxide (RGO)

_{2}H

_{4}xH

_{2}O (hydrazine hydrate), NaBH

_{4}, NaOH, NaH

_{2}PO

_{2}H

_{2}O etc. In RGO (the final product), the oxygen functional groups are partially removed but some of them always remain. RGO is a promising material with a variety of potential applications in many technical areas and is a relatively well-studied carbon/graphene derivative. Its production is cost-effective. The material itself has many valuable properties; it is flexible, achieves excellent electrical/thermal conductivity and has outstanding barrier properties. In addition, the remaining functional groups and defects in the RGO structure improve impedance mismatch, electron dipole relaxation and defect polarization relaxation. All types of defects presumably increase absorption, not reflection, as was observed with carbon nanotubes and graphite.

## 4. Method Section

^{3}, while RGO was 1.55 g/cm

^{3}.

#### 4.1. Measurement of Material Properties

_{11}and S

_{21}are sufficient to characterize the material.

- γ—propagation constant,
- ρ—reflection coefficient at front surface of the material.$$\rho =\frac{\sqrt{\mu}-\sqrt{\epsilon}}{\sqrt{\mu}+\sqrt{\epsilon}}$$
- d1—thickness of the sample being measured.

_{11}and S

_{21}according to Nicolson, Ross and Weir (NRW) formulas [10,11,12].

^{3}at 200 MHz but decreases to 100 at 10 GHz. Such a high value of ε″ of graphite makes it possible to obtain a good absorbing property of the absorber. On the other hand, the real part of permittivity of RGO is much higher compared to graphite with a value of 180 at 200 MHz and 100 at 10 GHz. The electric loss factor is stable from 155 to 100 in the measured frequency range.

#### 4.2. Reflection Properties of the Absorber Lying on Conductive Sheet

_{11}and S

_{21}are scattering coefficients for the slab of materials in free space, calculated using Equations (3)–(6).

^{2}(%)) in reference to the incident power density.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Schematic presentation of incident (E), transmitted (E

_{T}) and reflected field (E

_{R}): (

**a**) electronic circuit inside metallic or metallic-like enclosure, (

**b**) enclosure equipped with an absorber.

**Figure 3.**(

**a**,

**b**) permittivity of graphite (blue, dashed lines) and reduced graphene oxide (red, solid lines); (

**c**,

**d**) permeability of graphite (blue, dashed lines) and reduced graphene oxide (red, solid lines).

**Figure 5.**Reflection coefficients of power density of the absorber backed with the metal layer with thickness: (

**a**) 2 mm, (

**b**) 5 mm; graphite—blue, dotted line; RGO—red, solid.

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**MDPI and ACS Style**

Kubacki, R.; Lipińska, L.; Przesmycki, R.; Laskowski, D.
The Comparison of Microwave Reflectance of Graphite and Reduced Graphene Oxide Used for Electronic Devices Protection. *Energies* **2022**, *15*, 651.
https://doi.org/10.3390/en15020651

**AMA Style**

Kubacki R, Lipińska L, Przesmycki R, Laskowski D.
The Comparison of Microwave Reflectance of Graphite and Reduced Graphene Oxide Used for Electronic Devices Protection. *Energies*. 2022; 15(2):651.
https://doi.org/10.3390/en15020651

**Chicago/Turabian Style**

Kubacki, Roman, Ludwika Lipińska, Rafał Przesmycki, and Dariusz Laskowski.
2022. "The Comparison of Microwave Reflectance of Graphite and Reduced Graphene Oxide Used for Electronic Devices Protection" *Energies* 15, no. 2: 651.
https://doi.org/10.3390/en15020651