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The behavior of ZSM5 zeolites in the acid, sodium form or ion-exchanged with various metal ions (Cs, Sr, Ba, Mg, Fe, Co, Cu, Ag, Rh, Ga, In, La, and Ce) and that of Y and X zeolites ionexchanged with Ba ions are discussed with reference to their behavior in the adsorption of N 2 O from gaseous industrial streams containing low (<0.1-0.2%) concentrations of N 2 O, to produce a concentrated (>5%) stream of N 2 O for either autothermic operation of the decomposition of N 2 O or use of N 2 O as a selective oxidant. Ba-ZSM5 show significantly better performances than other metal-exchanged zeolites in the adsorption of N 2 O, although water competes with N 2 O for adsorption. However, the adsorption of N 2 O is faster than that of water, and thus it is possible to adsorb N 2 O even in the presence of larger (40 times higher) amounts of water in the feed. It is also shown that it is possible to have a dual-bed selective adsorption, where first water adsorbs selectively on an alumina bed and then N 2 O is adsorbed on a Ba-ZSM5 bed. It is suggested that the enhanced adsorption properties of Ba-ZSM5 are related to the presence of naked Ba 2+ ions that creates a strong electrostatic field within the zeolite cavities which allows the orienting of the N 2 O molecule and its trapping inside the zeolite.

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A continuous carbon fiber/silicon carbide matrix composite material has been produced by a low-cost process. In this process the space in a two-dimensional carbon fiber preform is filled with a SiC powder by a pressure infiltration method. High particle packing densities are achieved within the fiber preform in this way. The compact body is heat-treated at 400°C to form a porous framework, which is then infiltrated with a liquid preceramic polymer, Ceraset TM SN. Subsequently the infiltrated polymer is pyrolyzed in argon at 1300°C. The microstructure of the final composite is characterized, and mechanical properties of these composites are discussed.

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