Platinum aspect ratio

Figure 1.2 Modulus of the field enhancement factor versus the aspect ratio a = b and wavelengths X for SPM tips of different materials (a) gold, (b) platinum, (c) silver, (d) p-doped silicon, (e) tungsten. Reprinted with permission from J. Jersch, Applied Physics A, 66, 29 (1998). Copyright 1998, Springer-Verlag.

Profiles of mean and root-mean-squared (rms) temperatures were measured at 1-millimeter intervals along the stagnation plane. The latter was identified by the zero mean axial velocity as described below, of the opposed flames with thermocouple junctions comprising butt-welded bare platinum with platinum-rhodium (13%) wires of 50-micrometer diameter, with an aspect ratio of approx-... 

To increase the response rates of diffusion limited actuators, the aspect ratio can be increased to allow more surface area to be accessed. A common approach to achieve this is to produce responsive fibers of the polymer, often exploited for polyacrylonitrile (PAN)-based devices. To further improve their actuator behavior, the conductivity of the fibers can be increased by seeding with metallic particles, such as platinum, or by combination with other conductive fibers, such as graphite. ... 

A second method was based on the direct assembly of platinum building blocks, where hyperbranched multipods with high aspect ratios could serve as the nanostructured precursors. A network of platinum nanowires directly assembled from a solution phase is shown in Figure 10.15. Unlike the networks made from templates, these assembled networks could either be disassembled into individual multipods in dispersion form, or sintered into connected networks. 

Tables 13 and 14) [31]. These countries report huge reserves, but with different mine ratios of Pt to Pd to Rh (Table 15). The concentration of Pt, Pd and Rh in the raw ore is reported to be in the order of magnitude of a few parts per million, whereas their concentration in automotive catalysts is in the order of magnitude of about 3 000 ppm for Pt and about 600 ppm for Rh. These aspects contribute to the increasing interest in the recycling of the precious metals out of used automotive emission control catalysts. By 1996 about 16% of the platinum demand for automotive catalysts, about 5% of the palladium demand and about 10% of the rhodium demand for automotive catalysts was supplied from the recycling of these catalysts [32, 33],... 

This paper reports first results of research and development work to achieve nitrogen oxide reduction under lean diesel exhaust gas conditions. Much attention is paid to the influence of operation conditions on catalyst performance. A major part of the paper deals with the influence of the hydrocarbon component, the hydrocarbon concentration and the HC/NO ratio on the activity of a special developed platinum based catalyst. Other aspects discussed are a spectroscopic characterization and a selectivity study. A hypothesis of a "dual-site" reaction mechanism for NOx-reduction in lean diesel exhaust gas precious metal based catalyst is established. Finally, first promising results on the performance of the catalyst system in a vehicle dynamometer test are given. 

---