ABSTRACT
In this study we report on the adsorbate structures on an Ir(1 1 1) surface during the phase transition from the inactive to the active state during CO oxidation. The CO oxidation over Pt(1 1 1) is used as a reference case. Where Pt(1 1 1) either is inactive and CO covered or active and O covered, Ir(1 1 1) exhibits a transition state with co-existing chemisorbed O and CO. The observed structural differences are explained in terms of DFT-calculated adsorption energies. For Pt(1 1 1) the repulsive CO-O interaction makes co-existing chemisorbed CO and O unfavourable, while for Ir(1 1 1) the stronger O and CO adsorption allows for overcoming the repulsive interaction. At the onset of CO oxidation over Ir(1 1 1), a CO structure containing defects forms, which enables O2 to dissociatively adsorb on the Ir(1 1 1) surface, thus enabling the CO oxidation reaction. At the mass transfer limit, the Ir(1 1 1) surface is covered by a chemisorbed O structure with defects; hence, the active surface is predominately chemisorbed O covered at a total pressure of 0.5 mbar and no oxide formation is observed.
ABSTRACT
A patient treatment modality that involved a two-stage resin-bonded FPD was presented in this clinical report. During recovery of the alveolar socket, a direct bonded acrylic pontic was seated with an adhesive resin (Super-Bond C&B Clear). This primary prosthesis provided service for 6 months without trouble and was effective for maintaining the open space and recovery of oral functions. The secondarily seated resin-bonded FPD, which was made of silver-palladium-copper-gold alloy and bonded with a primer for noble alloys (V-Primer) and an adhesive resin (Super-Bond Opaque), has been functioning satisfactorily for more than 5 years. This two-stage procedure is useful in situations that require conservative or periodontal treatment before seating final prostheses.
