| Autor: |
H. Kathrein, H.J. Heinen, H. Wengeler, R. Knobel, F. Freund, G. Demortier, G. Oberheuser |
| Rok vydání: |
1982 |
| Předmět: |
|
| Zdroj: |
Nuclear Instruments and Methods in Physics Research. 197:27-36 |
| ISSN: |
0167-5087 |
| DOI: |
10.1016/0167-5087(82)90113-2 |
| Popis: |
Using the 12 C(d, p) 13 C method and an ultrahigh vacuum chamber for in situ heat treatments up to 1170 K and down to liquid nitrogen temperature, carbon was analyzed in a variety of synthetic MgO single crystals and of natural olivine single crystals (Mg, Fe) 2 SiO 4 . Characterisation by IR-spectroscopy and laser flash induced mass spectroscopy had shown that the crystals were free of occluded CO 2 , CO 3 , carbide and graphite, but carbon was found to be present in the bulk in the order of 300 to 800 wt. ppm in MgO crystals and of 200 wt. ppm in olivine crystals. The 12 C(d, p) 13 C analysis showed that the carbon was strongly enriched in a 0.5 μm thich subsurface zone and highly mobile. Heat treatment in vacuum up to 1170 K (MgO) respectively and 930 K (olivine) causes characteristic variations of the subsurface from within the bulk. The results indicate that the mobile carbon is interstitially dissolved, but more carbon is trapped in extrinsic vacancy sites from where it can be thermally activated to enter the interstitial sites. Upon heating the carbon reacts with lattice oxygen to give CO 2 and CO. With co-dissolved hydrogen it reacts to give a wide variety of hydrocarbons. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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