Magnesium oxide, isotopic oxygen

Magnesium oxide may be expected to function as an active catalyst for CO2 utilization since CO2 is easily chemisorbed on MgO [1-3]. Most works so far reported on this adsorption system were carried out above the room temperature, and recent works have demonstrated the occurrence of oxygen isotope exchanges between adsorbed species and surface 0 [4-6]. However, dynamic behaviors of adsorbed species, especially below the room temperature, are still open to question. 

Winter 10) relates isotopic exchange of molecular oxygen with magnesium oxide, zinc oxide, chromium oxide, nickel oxide, and iron oxide. He also compares the rates of isotopic exchange of these oxides with oxygen and the rates of adsorption and catalytic activity relating to the oxidation of CO and the decomposition of NgO. 

SIMS is also the only technique covered in this book that can detect isotopes. In Fig. 4.26, oxygen diffusion in magnesium oxide is smdied using [56]. A layer of Mg 0 mixed with Mg 0 is grown on a Mg O substrate followed with a Mg 0 layer to sandwich the Mg 0 layer. An as-grown sample and samples annealed at 1,950 °C for 5 m and at 1,360 °C for 72 h are profiled for to show the diffusion of The sample was profiled with 14.5 keV Cs" in a Cameca IMS 5f. The sample is an insulator so sample charging was controlled with an electron gun. 

As can be seen in Fig. 2-1 (abundance of elements), hydrogen and oxygen (along with carbon, magnesium, silicon, sulfur, and iron) are particularly abundant in the solar system, probably because the common isotopic forms of the latter six elements have nuclear masses that are multiples of the helium (He) nucleus. Oxygen is present in the Earth s crust in an abundance that exceeds the amount required to form oxides of silicon, sulfur, and iron in the crust the excess oxygen occurs mostly as the volatiles CO2 and H2O. The CO2 now resides primarily in carbonate rocks whereas the H2O is almost all in the oceans. 

Yapp CJ (1990) Oxygen Isotopes in iron (III) oxides 1. Mineral-water factors. Chem Geol 85 329-335 Young ED, Galy A (2004) The isotope geochemistry and cosmochemistry of magnesium. Rev Mineral Geochem 55 197-230... 

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