A study on the solubility and distribution of carbon in oxides

Wolf, Irene; Grabke, H. J.

doi:10.1016/0038-1098(85)91021-x

Cited by 166 publications

(57 citation statements)

References 13 publications

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“…In the present study, Ar/H 2 plasma pretreatment of the iron oxide film resulted into high density of nanoparticles (not shown here) which catalyzed the nucleation and growth of CNTs on the introduction of C 2 H 2 in the plasma [17]. The observation of a-C in samples A, and B and relative increase in the percentage of a-C with decreasing H 2 plasma pretreatment time of oxide films suggest the poor catalytic activity of oxide for CNTs growth as also reported by other methods [20,21]. In case of sample C, most of the iron oxide clusters are supposed to be reduced to Fe after 15 minutes of H 2 plasma treatment since plasma contains a lot of active H-species as observed by in-situ OES of the H 2 and H 2 +C 2 H 2 plasma in 200a900 nm wavelength range as shown in Fig.…”

Section: Resultssupporting

confidence: 70%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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The effect of hydrogen plasma treatment of iron oxide films on the growth and microstructure of carbon nanotubes (CNTs) by microwave plasma enhanced chemical vapor deposition process has been investigated. Microwave plasma was characterized in-situ using optical emission spectrometer. Morphology of the films was examined by scanning electron microscopy. Structural analysis was carried out by high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDS) and micro-diffraction attachments. It is found that oxide films without H 2 plasma pretreatment or treated for lesser time resulted in CNT films with high percentage of carbonaceous particles and with embedded particles/nanorods distributed discontinuously in the cavity of the nanotubes. The embedded particles were found to be of iron carbide (Fe-C) as confirmed by HRTEM, EDS and micro-diffraction analysis. Experimental observations suggested that the iron oxide particles had poor catalytic action for CNT growth and in-situ reduction of oxide clusters to Fe by hydrogen plasma plays a key role in discontinuous filling of the nanotubes by the catalytic particles. [12][13][14] have been used to synthesize CNTs. CVD methods (both thermal and plasma enhanced) are reliable in producing multiwalled CNTs (MWNTs) with proper control over the process parameters. Plasma enhanced CVD, however, can produce CNTs with a higher growth rate, at low temperature, and with better reproducibility. The plasma not only ionizes the gas but also causes a local surface heating [15]. Consequently, growth temperature could be significantly decreased compared to non-plasma CVD processes. In addition, the plasma atmosphere may also influence the detailed catalyst surface kinetics in many ways [16] and hence the growth of carbon nanostructures.Growth of CNTs and their microstructures depend on several parameters such as growth technique, feed gases, growth temperature, catalyst, and catalyst preparation method as well as their state (solid, liquid or vapor). In plasma assisted CVD processes, dilution gases play a critical role in the growth of CNTs and the structure of CNTs can be tailored by judicious control over gas composition [17]. In our earlier report, we investigated the effect of different dilution gases such as H 2 , NH 3 and N 2 and their different composition on the growth and microstructure of CNTs by microwave plasma enhanced CVD (MPECVD) process on Fe coated Si substrates using C 2 H 2 as feed gas [17]. Plasma pretreatment of catalyst film can also affect the growth and structure of CNTs significantly especially in a high frequency plasma process such as MPECVD. To the best of our knowledge, effect of H 2 plasma pretreatment of iron oxide films on the growth and structure of CNTs by MPECVD process have not been reported. Therefore, the motivation for the present

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Section: Resultssupporting

confidence: 70%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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“…Fujii and Meussner [5] proposed that carbon was generated on the oxide surface, transported through a dense outer oxide layer and produced a CO-CO 2 atmosphere within voids in a porous inner oxide layer. However, subsequent experiments [6] showed that the solubility of carbon in iron oxides is extremely small, and its solid-state diffusion through iron oxide scales is not feasible. Transport could occur instead by means of molecular CO 2 , but the scale microstructures are reported [5] to appear impermeable to gas.…”

Section: Introductionmentioning

confidence: 99%

“…Etching with a solution of 1% picric acid and 5% hydrochloric acid in ethanol was used to reveal alloy grain boundaries and internal carbides, and to distinguish wustite from the spinel phase in oxide scales. Murakami's reagent (1 g K 3 Fe(CN) 6 and 1 g KOH for 10 mL H 2 O) was also employed for revealing carbides.…”

Section: Materials and Experimentsmentioning

confidence: 99%

Carburisation of ferritic Fe–Cr alloys by low carbon activity gases

Gheno¹,

Monceau²,

Zhang³

et al. 2011

Corrosion Science

154

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“…Considering that in the metal dusting mechanisms reported, the ingress of carbon into the alloy seems to be a critical step to initiate the corrosion of the materials affected, we have proposed a novel approach to protect materials exposed to this type of corrosion consisting of applying surface thin films of (Cr, Al, or Si) oxides, which are impermeable to the diffusion of carbon [3]. Initially our efforts were focused on producing adherent and dense thin films [4,5], however soon after it was evident that fracturing of the films associated to the evolution of residual stresses during deposition was also a central issue in the development of effectively protective films.…”

Section: Introductionmentioning

confidence: 99%