| Abstract
| - Amorphous materials are typically characterized using nitrogen adsorption isotherms at 77 K to obtain poresize distributions. However, higher temperatures and different adsorbates could also be used. We have measuredthe adsorption isotherms of carbon dixoide, methane, nitrogen, and argon at room temperature and 77 K onthe typical high surface area amorphous activated carbon AX21. We analyze these isotherms using densityfunctional theory to obtain pore size distributions and explore whether they vary with the adsorbate used orwith temperature. We find, for example, that the pore structures predicted for AX21 using nitrogen at 77 Kand carbon dioxide at 293 K are quite different, with carbon dioxide showing a unimodal micropore peak at10.3 Å not seen at 77 K by nitrogen or argon.
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