Using a microwave to expand graphite produces partially-exfoliated graphene "worms" that are useful in the production of graphene and for making supercapacitor batteries. This method involves microwaving acid-treated graphite to produce expanded graphite. Acid-treated graphite can be made by soaking approximately 10 grams of ~35 mesh flake graphite in 150 mL concentrated sulfuric acid (H2SO4, 98%) together with 50 mL 70% Phosphoric acid (70%) overnight. The acid molecules are small enough to squeeze in between and intercalate the layers of graphene that make up the graphite flakes. The graphite is then placed in a acid-resistant filter paper (PE/PTFE) and washed with copious amounts of deionized (DI) or distilled water several times to remove any excess acid until the pH reaches 7 and is dried overnight or for several hours in a vacuum drier at 60-80 degrees C. The dried acid-treated graphite is then placed in a modified domestic 1000-Watt microwave oven for 1-2 minutes at a time with frequent intermissions in order to remove the expanded graphite and to rearrange the remaining unexpanded graphite. The process is repeated until all the acid-treated graphite is expanded.
NOTE: This procedure involves dangerous, corrosive strong acids, dangerous or fatal acid fumes and vapors, and high heat produced by the microwave-assisted expansion. This procedure can cause skin burns, acid/chemical burns, respiratory injury or failure, and potential death. DO NOT ATTEMPT TO PERFORM THIS PROCEDURE INDOORS WITH A KITCHEN MICROWAVE, OR WITHOUT THE NECESSARY PERSONAL PROTECTION EQUIPMENT (GOOGLES, GLOVES) AND PROPER CHEMICAL AND SAFETY TRAINING. The acid vapors will destroy the microwave oven if the oven is not properly vented and shielded with acid-resistant materials to keep the acid vapors from condensing inside the oven and destroying the electrical components. Do not attempt to open any microwave oven if you are either an amateur person who has never serviced electrical appliances, or someone who is unsure or unskilled in electronics and electrical safety, as microwave ovens contain a high-voltage capacitor which hold several thousand volts (even when the oven is not in operation or is unplugged) and can kill a person on direct contact if touched. The use of high-voltage transformers and microwave ovens for this procedure as demonstrated in this video should never be performed by children or any person who is unfamiliar with chemical and electrical safety and must follow all safety precautions and assume any and all risks, including damage of equipment, personal injury or death, that are likely to occur from performing this procedure.