What material will absorb 900MHz, 2.4G, 5.8G RF frequencies?

Anyone knows about the ISM band ?

900MHz, 2.4G, 5.8G

Any materials will absorb those frequency ?

Ferrite Tile is a good RF absorber for freq below 1GHz. It is a 10mm thick, heavy and easy-to-break material.

For higher freq, it should be pyramidal absorber. It size is depend on the freq (size reduce for higher freq).

An easy way to know the absortion of the materials at 2.4 is introduced them into a microwave oven.
If they take heat is that absorv else don′t use it in any project unless you need a loss in the signal.

All RF frequencies are absorbed in water. So everything is containing water (as human body for example ) will absorb those more or less. What really count is the dielectrical permitivity of the material which is radiated with this frequency, the power level, the modulation scheme and the exposion time.
So, the +18dbm emitted continously by an indoor WIFI router it has the same danger for a long time exposion on the human body as the 900MHz 2W GSM phone used one or twice per week.

greetings,