PSI - Issue 28

Angeliki-Eirini Dimou et al. / Procedia Structural Integrity 28 (2020) 1679–1685 Author name / Structural Integrity Procedia 00 (2019) 000–000

1682

4

Table 3. Mix proportions of rGO dispersions Dispersion

rGO (g)

Water (mL)

wt % of binder

rGO_0.05 rGO_0.075 rGO_0.10 rGO_0.15 rGO_0.20 rGO_0.25

0.070 0.105 0.140 0.210 0.280 0.315

100 100 100 100 100 100

0.05

0.075

0.10 0.15 0.20 0.25

Dispersion was accomplished by subjecting the mixtures to ultrasonication energy with a probe type sonicator. The ultrasound generator used was the VCX-500 model and the nozzle model was CV-334 model by the company Sonics &Materials (Fig. 1). The total duration of the sonication process was approximately 4.5 h (~ 100 kJ sonication energy), consisting of 360 sonication cycles with each cycle containing 15 s “pulse mode” and 30 s “idle mode” to avoid temperature rise.

(a) (b) Fig. 1. (a) rGO dispersion with the embedded probe sonicator and electrical impedance sensor just before testing and (b) ultrasound energy generator 2.2.2. Electrical Impedance Spectroscopy EIS measurements were conducted during the sonication process using a Dielectric Thermal Analysis System (DETA-SCOPE ® ) supplied by ADVISE, Greece (Fig. 2). The setup was connected to an interdigital dielectric sensor IDEX ® , film-shaped, produced by Netzsch, Germany. The DETA-SCOPE ® applies sinusoidal excitation voltage having amplitude of 10 V and frequency that ranged from 0.1 Hz to 100 kHz. The measurements are recorded by the corresponding software of the company. The first experiments to be conducted were on the solvent itself, while the tests on the six dispersions followed. For each dispersion 20 impedance measurements were taken during the ultrasonication. The total process was repeated twice for each dispersion.

Fig. 2. Electrical Impedance Spectroscopy setup