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The present text describes an investigation of XPS study of multiwall carbon nanotube (MWNT) synthesis. The aim of the investigation was not only to improve the reaction activity by mixing nickel with vanadium, but also to understand the formation mechanism of the nanotubes. Carbon nanotubes were produced by catalytic chemical vapor deposition (CCVD) of acetylene on transition metal containing catalysts supported on zeolite ZSM-5. The samples were characterized at two different levels. At the nanoscale, they were studied by transmission electron microscopy (TEM), while at macroscopic scale mainly XPS was used to investigate the changes during the reaction.

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C h aracterization o f iro n con ta in in g alum ina sup p orted ca ta ly sts w as perform ed b y tra n sm issio n electron m icrocopy (T E M), M ossbauer, and X PS sp ectroscop y d u rin g form ation o f m u ltiw all carb on n an otu b es from a cety len e a t 1000 K. TEM im ages show ed th a t carb on fib ers (o u ter diam eter is around 2 0-4 0 nm) w ere gen erated on F e/A l2 0 3 sam p les w h ile on th e b im eta llic F e,C o/A l2 0 3 carb on n an otu b es w ith an average d iam eter o f 8-1 2 nm w ere form ed. X PS sp ectra revealed th a t F e-C o a llo y form ed durin g th e in tera ctio n o f F e,C o/A l2 0 3 and acetylen e a t 1000 K. T he fo rm ation o f th e b im eta llic a llo y w as proven by M ossbauer sp ectroscop y a s w ell. Index Terms-Iron con ta in in g alu m in a su p p orted ca ta ly st, n an otu b es, M ossbauer sp ectroscop y, X PS sp ectro sco p y. I. In t r o d u c t i o n S INCE their discovery in 1991 [1], carbon nanotubes have been generating a continuously growing interest since these hollow nanostructures have exceptional electrical [2] and mechanical [3] properties, making them usable in many fields. Various production methods have been developed aiming at the production of carbon nanotubes in large scale. Of the main synthetic processes, laser vaporization [4], electric arc dis charge [5], and catalytic chemical deposition of hydrocarbons over metal catalysts (CCVD technique) [6], only the latter method supplies carbon nanotubes in high yield at a low cost of production. Being a catalytic process, the combinations of transition metals and supports can be changed depending on the characteristics required, for example, the alignment [7] or the size of the tubes [8], [9]. On the other hand, it has been demonstrated that supported transition metals (in particular iron, cobalt, and nickel) on silica [10], alumina [11], zeoliteand clay-derived [%BIBREFGoumis:2002%] supports are used frequently in this process [12]. For characterizing and comparing the productivity of the catalysts the amount of

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