Morphological Characterization and Lumped Element Model of Graphene and Biochar Thick Films

Abstract

Carbon based materials exhibit interesting mechanical, thermal and electrical properties which make them excellent contenders for use as fillers in composites as film. Graphene has been vastly used among the carbon-based materials. More recently eco-friendly carbon-based materials like biochar have emerged. The deployment of carbon-based materials in films needs to be studied since films are more versatile and permit the exploitation of electrical properties of such materials over circuits and systems. Typical circuits and systems exploiting electrical properties of novel materials perform a number of applications including sensing, detection, tunable devices and energy harvesting. In this paper, films composed of 9:1 graphene or biochar are deployed on a microstrip line. The morphological properties of graphene and biochar and their respective films are studied with Raman spectra and Field Emission Scanning Electron Microscope (FESEM). The electrical properties (four-point probe measurements and scattering parameter measurements) of the films. Low frequency measurements are used as starting point for circuit models estimating the lumped impedance of the films. From the morphological characterization it is shown that biochar films appear as granulates carbonaceous materials whereas graphene films contains several flakes forming a network. From the low frequency measurements and microwave characterization it is seen that graphene films are more conductive as compared to biochar films. In many applications, it is useful to know the surface impedance of the film since it varies on interaction with any external stimulus (variation of pressure, humidity, gas, etc.)

Correlation of Transmission Properties with Glucose Concentration in a Graphene-Based Microwave Resonator

“…R s accounts for the sheet resistance, but is also the DC resistance (the only remaining element at zero frequency) between nodes A and B, and is linked to the percolative path in the deposition. As discussed in [37,38], an increase in graphene weight fraction makes R s lower as the percolative threshold falls. The described model takes into account both the graphene and the binder due to the impossibility of removing it.…”

“…As shown in [39], capacitances toward GND are mainly due to the binder. In the case of a line with a gap where the film is deposited, generally, a resistance variation of the film will result in an amplitude variation of the S 21 , whereas a reactance variation will result in the phase variation of the S 21 [37].…”

Analysis of Transmission Properties of Sludge Biochar Composites in the C-Band

“…The probe works in the frequency band of 200 MHz to 20 GHz. Details of the measurements performed with this setup can be found in [14]. To measure the complex permittivity of the composites, the probe was calibrated using the required calibration procedure with air, short, and water.…”

“…This will result in value being added to the product and also help recycle unwanted and environmentally damaging material. The use of carbon-negative materials in innovative applications can be effective in reducing the carbon footprint [14]. A number of studies have been performed on the use of carbon-based materials (see, e.g., [15] and [16]), specifically biochar, in applications on the effectiveness of electromagnetic interference/shielding [16].…”

Lumped-Element Circuit Modeling for Composite Scaffold with Nano-Hydroxyapatite and Wangi Rice Starch

“…Lumped-element modeling can be realized at microwave frequencies [ 7 , 8 , 9 , 10 ]. Many past studies have used this model for various applications [ 11 , 12 , 13 , 14 , 15 , 16 ]. At higher frequencies, the inductive and capacitive reactance of the passive elements are significant.…”