What materials have the higest carbon?

Question

This is for the purpose of repelling harmful energy in the microwave frequencies. Diamond? Graphite?

Answer 1

Carbon in all allotropic forms is 100% C.
Carbon does not 'repel' microwave. There is nothing inherently harmful in microwave energy. Those frequencies used in cooking can cause deep burns if one is exposed.
It can be hazardous, if the oven leaks.
Virtually any metal, aluminum for example will reflect it. After all the resonant cavity of the common MW oven reflects all energy internally. Many recipes suggest shielding some meat portions from the micro wave using the common kitchen foil.

Answer 2

The synthesis of composites based on polymers containing carbon as additives is rather relevant because it has been found that applications in several industries are increasing, particularly due to their unusual mechanical and electrical properties. By choosing the adequate doping concentrations, we can precisely control the electrical properties in the microwave frequencies.

I think the materials are styrene polymers. :))

Answer 3

Nothing repels microwaves. Any conductor absorbs microwaves. I do not know of any good evidence of people being harmed by microwaves, except for people with pacemakers.