Low-Temperature Ashing in Plasma Chambers Equipped with Electrostatic Shielding

Low-temperature ashing of cellulose powder impregnated with inorganic salts was carried out in plasma chambers where sample boats were isolated from the discharge region by a stainless steel mesh. Two types of the plasma chambers installed with external and internal electrode systems were tested using alkali halides as model mineral components. The electrostatic shielding by the metal mesh raised the recovery of halides and supressed the production of oxyhalides, thus suggesting that milder oxidation took place. It has been found that the plasma chamber incorporated both with external electrode system and with electrostatic shielding will be best advisable to obtain high recovery of initial mineral components and to minimize the production of higher oxides by the oxygen plasma.