Oxidation of iridium

Complex Transport Reactions in a Temperature Gradient Tube: Radiochemical Study of Volatilization and Deposition of Iridium Oxides and Hydroxides

“…The solid line is calculated with Equations (9, 13) using ¿l//?ds.d¡ss = -102 kJ mol -1 , dashed lines give the uncertainty of +4.4 kJ molIf the low-temperature zone originates from a simple adsorption of a water-containing compound, the entropy change can be calculated with Equation (15), see Table 2. This allows then an estimate of the adsorption enthalpy by means of Equation (9). Figure 4b and Table 4 show such an evaluation.…”

“…These studies were carried out at various oxygen partial pressures by the carrier gas method [3,4,7,9,10,12], with a thermobalance [1], by weight-loss measurements [4], by mass spectrometry [8], and by the heating-wire technique [6,11], The results led to the conclusion that Ir0 3 (g) is the dominant species in the transport reaction, whereas the formation of lr 2 0 3 , discussed earlier [4,10,12], was considered to be unlikely [13]. Transport reactions of macroamounts in presence of water at defined partial pressures have not yet been reported.…”

Oxidation Damage of Spark Plug Electrodes

“…[23±32] Generally low weight losses were measured using furnaces, where both the gas atmosphere and the walls are at the reaction temperature. [23,24,26,31,32] If however, only the sample is heated, [25,28±30] like in the present experiment, the volatile oxide molecules can condense at the cold walls of the chamber. This does not give rise to equilibrium conditions, thus leading to higher oxidation rates.…”

Phase equilibria and oxidation behavior of Ir-rich Ir–Y binary alloys

“…Among them, IrO 2 (g) and IrO 3 (g) are often observed [14][15][16][17][18][19][20][21][22][23], while the existence of IrO(g) [19] and Ir 2 O 3 (g) [16,17,25,26] has also been suggested. Below 1775 K, IrO 3 (g) predominantly forms over IrO 2 (g) under 1.0 atm of oxygen [18], and the partial pressure of IrO(g) and Ir 2 O 3 (g) is negligibly small [18,20,32]. Hence, it is speculated that IrO 3 (g) is the major gaseous Ir oxide formed during the oxidation of the pure-Ir and Ir-Y alloys at 1373 K.…”

“…All the alloys exhibit small weight gain at the initial stage of oxidation, followed by apparent weight loss with elapsed time. The weight loss is believed to be attributed to the volatilization of Ir oxides, since Ir is known to form several kinds of volatile oxides [14][15][16][17][18][19][20][21][22][23][24][25][26]. The absolute values of the weight loss are re-plotted in a double-logarithmic diagram as shown in Fig.…”