**3. Experimental section**

The experimental studies consist of two different methods; microwave (MW) energy-assisted method and ultrasound (US) energy-assisted method.

#### **3.1 Materials used**

In microwave energy method; graphite (natural flake graphite, grade 3061; purchased from Asbury Graphite Mills, Inc., New Jersey) was used as starting carbon source. Different solvents were used such as 25% ammonia solution (Merck KGaA), N,N-Dimethyl formamide (Merck KGaA), ethylene glycol (ZAG Chemicals) and ethylene diamine (Merck KGaA). Chemicals used in the second cycle of experiments were of analytical grade; n-Hexadecane (Merck, 99.5%), dimethyl sulfoxide (Merck, 99.9%), sodium hydroxide (J.T. Baker, 99%), 1-octanol (Merck, 99%), perchloric acid (Merck, 70–72%), N,N-Dimethyl formamide (Merck, 99.8%), ethylene glycol (ZAG Chemicals, 99.3%), and ethylene diamine (Merck, 99%).

Chemicals used in the ultrasound method are as follows: Graphite fine powder (Extra pure, Asbury Inc., New Jersey), graphene nanoplatelets (XG Sciences, Michigan, US) Dimethyl sulfoxide - DMSO (Merck), N,N-Dimethylformamide - DMF (Merck), Perchloric acid 70–72% - PA (Merck).

#### **3.2 Preparation of graphene sheets via microwave method**

The procedure of MW treatment was summarized as following: First, natural graphite is added to ammonia, then obtained suspension was sonicated by ultrasound energy device (BANDELIN ® HD 2200 SONOPULS), under conditions 200 W,

**31**

**Figure 5.** *Ultrasound device.*

*Investigation of Alternative Techniques for Graphene Synthesis*

and thermocouple was adjusted carefully as shown in **Figure 4**.

**3.3 Preparation of graphene sheets via ultrasound method**

35 kHz, mode 5 and 50% power for 10 min. Secondly, reaction was performed in Milestone Start-S model microwave oven for half an hour at 120°C temperature and 1 bar pressure by applying 50, 100 or 200 Watt energy. Pressure controller was active,

0.3 g graphite was dispersed in 50 ml solvent such as DMSO, DMF and PA. Obtained dispersions were sonicated by the means of BANDELIN ® HD 2200 SONOPULS (which is given in **Figure 5**) equipped with a VS 190 T sonotrode,

Then, these dispersions were subjected to 60 minutes centrifugation (Elektromag, M 4812 P) at 3000 rpm to remove the unexfoliated part of graphite; after the heavier particles were settled down, supernatant parts were decanted and

*The experimental system with a multimode microwave furnace: Reaction was performed inside a Teflon* 

*DOI: http://dx.doi.org/10.5772/intechopen.94153*

200 W, 50% amplitude for 3 hours.

collected in separate vials.

**Figure 4.**

*vent-and-reseal vessel.*

*Investigation of Alternative Techniques for Graphene Synthesis DOI: http://dx.doi.org/10.5772/intechopen.94153*

35 kHz, mode 5 and 50% power for 10 min. Secondly, reaction was performed in Milestone Start-S model microwave oven for half an hour at 120°C temperature and 1 bar pressure by applying 50, 100 or 200 Watt energy. Pressure controller was active, and thermocouple was adjusted carefully as shown in **Figure 4**.
