Formation and characterization of catalytic carbons obtained from co disproportionation over an iron nickel catalyst—II: Characterization

✍ Scribed by M. Audier; J. Guinot; M. Coulon; L. Bonnetain

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 612 KB
• Volume: 19
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(81)90114-7

✦ Synopsis

The metal-carbon composites obtained by CO disproportionation (2CO *CO2 + C) over an iron-nickel (containing 75 Wt%Ni) are characterized by T.E.M., X-ray diffraction and krypton adsorption at 77 K. Besides the now well known carbon filaments, two other types of morphology are described and the experimental conditions of their formation determined: the bit&es and bifilaments as low temperature products and carbon shells as high temperature products. X-Ray diffraction studies show that the structure of the alloy is not modified by fragmen_tation and deposition and that the d 00.2 spacing is about 3.42 A when formed below 500°C and about 3.38 A when formed above 500°C. Krypton isotherms confirm that the mean size of the carbon particles increases with temperature of their formation. The filamentous-shell morphology transition suggests that a change in the mechanism of metal fragmentation occurs around 500°C which is also observed in the deposition kinetics. Finally we propose two semi quantitative index numbers for characterization of the crystallographic orientation of surfaces, the two numbers being derived from the shape of krypton adsorption isotherms.