Transition manganese oxide phases

Positive proof is given that thermal ions or chemi-ions accelerate the nucleation process of carbon formation. On the other hand, metals which easily produce hydroxides can inhibit carbon formation, and of these, barium is the most eflBcient. Transition metals such as manganese do not seem to play a role either in the formation phase of small soot particles or in their oxidation phase. We suggest that in industrial combustion devices, their intervention occurs in the agglomeration phase from involatile oxides formed in poor combustible zones. These oxides produce positively charged solid particles which can transfer their charges to the small soot particles, and consequently they prevent the agglomeration process. [Pg.189]

All decomposition reactions are endothermal except that of FeU04, presumably because this is the only reaction which involves oxidation of the double oxide. No significant diflFerence was noted in the DTA or TGA curves of the two NiU04 phases. It is interesting to note the alternating pattern in the decomposition reactions of the uranates. The iron, nickel, and zinc double oxides tend to decompose directly into their constituent oxides, while the manganese, cobalt, and copper compounds decompose to other double oxides. The pattern is not carried over into the decomposition temperatures. In this instance, the thermal stability of the double oxides appears to vary directly with the characteristic transition element oxidation states Gr(III) > Mn, Go (III, II) > Ni, Zn(II) > Gu(II, I). The iron compounds constitute a definite exception to this pattern. [Pg.221]

Another example of the hollandite-type manganese oxides is Ki.5(H30)x MngOi6 [131, 132], where the HsO groups occupy part of the 1/4 vacant sites in the tunnels, not occupied by potassium ions. These groups intercalate into the structure during a hydrothermal synthesis. From susceptibility measurements, three phase transitions were observed [131, 132] at Ti = 180-250 K, Tj = 52 K, and T3 =... [Pg.811]

Several metal oxides with varying phase structures and nanostructures have been developed, including manganese oxide, iron oxide, molybdenum oxide, tin oxide, and titanium oxide. The most prominent issues surrounding transition metal oxide development efforts are (1) limited electronic conductivity and low theoretical capacitance in comparison to ruthenium oxide and (2) poor cyclability due to their redox nature and electrochemical instabilities. The varying electrochemically stable potential windows for some species of metal oxides completely eliminate their potential applications in ES devices. [Pg.339]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...