TPD Study of Mordenite-Type Zeolites for Selective Catalytic Reduction of NO by NH 3
ABSTRACT The effect of the adsorption of NO and NH3on catalytic activity has been examined by temperature-programmed desorption over a series of cation-exchanged mordenite catalysts for selective catalytic reduction (SCR) of NO by NH3. The catalytic activity observed in a packed-bed flow reactor was well correlated with the cation content of the catalyst and its adsorption properties, making it possible to elucidate the role of metals and acidity in this reaction system. The amount of NH3and NO adsorbed on the catalyst surface proportionally increased with the degree of cation exchange of the catalyst, especially at the Brønsted acid site (H+) and the metal site (Cu2+). SCR activity also gradually increased with the acidity of the catalyst and/or its degree of catalyst cation exchange. Surface acidity of the mordenite catalysts appears to be a dominant factor in the high performance of the SCR reaction system. The common activation energy is observed to be about 12 kcal/mole for NaHM and CuHM catalysts, independent of their cation content on the catalyst surface. The active sties of this catalytic system are both the Brønsted acid site and the metal site. Furthermore, the reaction occurred in a Langmuir–Hinshewood manner with a dual-site catalysis mechanism.
Conference Paper: Resistless patterning of aluminum[Show abstract] [Hide abstract]
ABSTRACT: A technique for patterning and depositing aluminum using laser-assisted selective chemical vapor deposition (CVD) is presented. This is accomplished using a light-assisted process that activates an adsorbed metallorganic precursor for aluminum, dimethyl-aluminum hydride (DMAlH), onto the substrate surface, thus forming a seed layer for subsequent selective CVD. In the same processing chamber, once the patterning is delineated via this seed layer, the substrate temperature is raised to 110-180°C, and selective CVD of aluminum takes place. A report is presented on the issues of selectivity, growth rates, morphology, electrical properties, and elemental composition of aluminum grown in this manner. Electrical resistivity, for example, can be as low as twice that of bulk aluminum. Furthermore, in order to make such a process compatible with multilevel metallization schemes, contact resistivity of such a film to preexisting aluminum metallization (with a native aluminum oxide) was measured and found to be ~0.2 μΩ-cm <sup>2</sup> without any special pre- or post-treatment. Previous attempts at such a deposition and patterning scheme were less than successful at obtaining reliably low contact resistivitiesVLSI Multilevel Interconnection Conference, 1990. Proceedings., Seventh International IEEE; 07/1990
Conference Paper: A 2.5 gb/s GaAs ATM Mux Demux ASIC[Show abstract] [Hide abstract]
ABSTRACT: This paper describes the design and implementation of a high speed GaAs ATM Mux Demur ASIC (AMDA) which is the key element in a high speed ATM Add-Drop unit. This unit is used in a new distributed ATM multiplexing-demultiplexing architecture for broadband switching systems. The Add-Drop unit provides a cell based interface between networks/systems operating at different data rates, the high speed interface being 2.5 Gb/s and the low speed interface being 155/622 Mb/s. Self-timed FIFOs are used for handling the speed gaps between domains operating at different clock rates, and a Self-Timed At Receiver's Input (STARI) interface is used at all high speed chip-to-chip links to eliminate timing skews The AMDA demonstrated operation above 4 Gb/s (500 MHz clock frequency) with an associated power dissipation of 5 WGallium Arsenide Integrated Circuit (GaAs IC) Symposium, 1995. Technical Digest 1995., 17th Annual IEEE; 01/1995