Oxygen niobium oxide

Niobium Oxides. The solubihty of oxygen in niobium obeys Henry s law to the solubiHty limit of the first oxide phase of 850—1300°C (123). The amount of oxygen in solution in niobium is 1.3 at. % at 850°C and nearly 2 at. % at 1000°C (124). Only three clearly defined anhydrous oxides of niobium have been obtained in bulk, ie, NbO, Nb02, and Nb20. Niobium monoxide, NbO, is obtained by hydrogen reduction of the pentoxide at... 

The fluorination process aims to decompose the material and convert tantalum and niobium oxides into complex fluoride compounds to be dissolved in aqueous solutions. The correct and successful performance of the decomposition process requires a clear understanding of the oxygen-fluorine substitution mechanism of the interaction itself. 

Thermal treatment of the compounds obtained from the hydrolysis leads to their decomposition, yielding tantalum or niobium oxides and gaseous oxygen. The processes of thermal decomposition are given as follows [512] ... 

At temperatures above 45°C, however, (NRj MOs compounds decompose yielding gaseous ammonia, NH3, and oxygen as well as tantalum or niobium oxides ... 

Oxygen sensors for air/fuel control in combustion engines (niobium oxide, Nb205, is also used for this application). 

Sasaki K, Zhang L, Adzic RR. 2008. Niobium oxide-supported platinum ultra-low amount electrocatalysts for oxygen reduction. Phys Chem Chem Phys 10 159-167. 

Oxygen and carbon have substantial solid solubilities in niobium at the temperatures normally required for reduction. As the activity coefficients of both carbon and oxygen in niobium are low, their retention in the niobium metal produced by the carbothermic reduction of niobium oxide is expected. It is, however, possible (as explained later) to remove these residual impurities by extending the pyrovacuum treatment to still higher temperatures and lower pressures. 

Niobium is a soft grayish-silvery metal that resembles fresh-cut steel. It is usually found in minerals with other related metals. It neither tarnishes nor oxidizes in air at room temperature because of a thin coating of niobium oxide. It does readily oxidize at high temperatures (above 200°C), particularly with oxygen and halogens (group 17). When alloyed with tin and aluminum, niobium has the property of superconductivity at 9.25 Kelvin degrees. 

The difference in the distribution of acidic sites in the samples calcined in air and in vacuum can be due to the reduction of niobium oxide which most probably occurs during heating under vacuum. The samples evacuated at higher temperatures became blue. The blue colour disappeared after heating in the presence of oxygen. The reduced form of niobium oxide can be located in positions different from those occupied by Nb205 and may cause the strong Lewis acidity of samples. 

NbC and the various oxides that were formed. The results confirm the fact that both NisNb and NbC react with oxygen at these temperatures to form niobium oxides of ranging stoichiometry, with a greater propensity for NisNb to oxidize to Nb205. 

Platinum supported on niobium oxide phases also exhibits high activity for oxygen reduction, despite a 50 to 150 fold decrease in platinum compared to the standard 10 weight % platinum on Vulcan carbon. 

The structural chemistry described in Section 5.3 is concerned with reduced niobium oxides in which various NbeOu clusters are discernible. - Phases with ordered structures have been prepared by careful choice of preparative conditions. Reduced niobium oxides have NbeOn cluster cores which are discrete (OD) or linked together through apical oxygen atoms to form ID (chain), 2D (layer), or 3D... 

There are some limitations to NblZr based alloys. At high temperatures Niobium oxidizes rapidly in atmospheres containing oxygen, resulting in significant embrittlement [DiStefano, 1990]. This restricts the use of NblZr when in contact with most atmospheres. These limitations preclude the use of NblZr on the outside surfaces of the... 

---