Temperature-dependent chemical state of the nickel catalyst for the growth of carbon nanofibers

Yu, Bowen; Zhang, Qiankun; Hou, Lei; Wang, Shiliang; Song, Min; He, Yuehui; Huang, Han; Zou, Jin

doi:10.1016/j.carbon.2015.10.048

Cited by 36 publications

(35 citation statements)

References 52 publications

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“…61 Group (b) spacings could be assigned either to rh-Ni 3 C or to fcc-Ni. According to these findings, previous own work, and the literature on this material system, the initial Ni-rich phase of NCT type I is assigned to rh-Ni 3 C. 57,[62][63][64] The cross-sectional TEM image of NCT type II (Fig. 1d) shows the formation of a Ni-enriched layer appearing darker than the SiO 2 substrate and the resin glue on top of the film, which is used for TEM specimen preparation.…”

Section: Resultssupporting

confidence: 61%

Carbon : nickel nanocomposite templates – predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

et al. 2016

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Carbon : nickel (C : Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD). Two NCT types of 2 nm thickness were prepared by ion beam co-sputtering without (type I) or with assisting Ar(+) ion irradiation (type II). NCT type I comprised Ni-rich nanoparticles (NPs) with defined diameter in an amorphous carbon matrix, while NCT type II was a homogenous C : Ni film. Based on the Raman spectra of more than 600 individual SWCNTs, the diameter distribution obtained from both types of NCT was determined. SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I. About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm. In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution from 0.80 to 1.40 nm covering 88% of all SWCNTs are obtained from NCT type II. From both catalyst templates predominantly separated as-grown SWCNTs are obtained. They are free of solvents or surfactants, exhibit a low degree of bundling and contain negligible amounts of MWCNTs. The study demonstrates the advantage of predefined catalysts for diameter-controlled SWCNT synthesis in comparison to in situ formed catalysts.

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Section: Resultssupporting

confidence: 61%

Carbon : nickel nanocomposite templates – predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

et al. 2016

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“…This situation is analogous to catalyst poisoning or coking mechanisms in classical heterogeneous catalysis. 112 We emphasize that this highly bulk supersaturated nature at all processing stages and the intrinsically high carbon arrival rates from the surroundings are hallmark features of the thermal evolution mechanism in such metal/carbon nanocomposites, which clearly separates this class of materials from other metal–carbon systems where carbon influx to the interface can be controlled at lower rates, such as in balanced heterogeneous catalysis reactions 112 , 113 or graphene 35 − 42 and CNT 45 − 59 growth from Ni catalysts.…”

Section: Discussionmentioning

confidence: 97%

In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

Bayer¹,

Bosworth²,

Michaelis³

et al. 2016

J. Phys. Chem. C

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Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for higher temperatures (400–800 °C) Ni-catalyzed isothermal graphitization of the amorphous carbon matrix sets in, which we link to bulk-diffusion-mediated phase separation of the nanocomposite into coarser Ni and graphite grains. Upon natural cooling, only minimal precipitation of additional carbon from the Ni is observed, showing that even for highly carbon saturated systems precipitation upon cooling can be kinetically quenched. Our findings demonstrate that phase transformations of the filler and morphology modifications of the nanocomposite can be decoupled, which is advantageous from a manufacturing perspective. Our in situ study also identifies the high carbon content of the Ni filler crystallites at all stages of processing as the key hallmark feature of such metal–carbon nanocomposites that governs their entire thermal evolution. In a wider context, we also discuss our findings with regard to the much debated potential role of metastable Ni3C as a catalyst phase in graphene and carbon nanotube growth.

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“…[82] In another carbon nanofiber growth study with nickel as the growth substrate, it was found that nickel can be present in three stages during the growth process:N i 3 Ca t5 73 K, composite formation of Ni-Ni 3 C 1Àx at 673-773 Ka nd Ni metal at 873 K. They also note that no stable nickel carbides can be formed, but that metastable species are often presenta tl ower temperatures( below 1373K). [83] Ni-W 2 Cs upported on activated carbon has been shown to be comparablya ctive to noble metal catalysts in hydrocracking of woody biomass to form ethylene glycol. [84] Nickelm etal can be carburized to form Ni 3 C, which occurs in small amounts duringm ethanation with CO gas as the reactant at 538 K. [85]…”

Section: Biomass Conversion and Catalysts For Related Processesmentioning

confidence: 99%

“…The formation of carbon nanofibers and incorporated nickel carbide could only occur after the initial reduction of Ni 2+ to Ni 0 by carbon containing precursors . In another carbon nanofiber growth study with nickel as the growth substrate, it was found that nickel can be present in three stages during the growth process: Ni 3 C at 573 K, composite formation of Ni‐Ni 3 C 1− x at 673–773 K and Ni metal at 873 K. They also note that no stable nickel carbides can be formed, but that metastable species are often present at lower temperatures (below 1373 K) . Ni‐W 2 C supported on activated carbon has been shown to be comparably active to noble metal catalysts in hydrocracking of woody biomass to form ethylene glycol .…”

Section: Mechanisms Of In Situ Carburizationmentioning

confidence: 99%

In Situ Formation of Metal Carbide Catalysts

et al. 2017

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Metal carbide catalysts are essential to many widely used chemical processes. Fischer‐Tropsch synthesis, methane dehydroaromatization and biomass conversion catalysts are typically prepared in situ from a metal oxide precursor with a carbon‐containing gas. The reduction process of the metal oxide affects the final catalyst, as does the carburization gas mixture and metal promoters. By looking at materials that are carburized in situ, new insights can be gained about catalyst activation, fuel processing, and deactivation stages. The main focuses of this Review are iron carbide, molybdenum carbide and nickel carbide; analyzing catalyst synthesis methods, reduction steps, in situ carburization and improvements to the native processes. By combining years of research on these catalysts, trends and similarities are observed that can be used to improve current catalytic studies.

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Temperature-dependent chemical state of the nickel catalyst for the growth of carbon nanofibers

Cited by 36 publications

References 52 publications

Carbon : nickel nanocomposite templates – predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

Carbon : nickel nanocomposite templates – predefined stable catalysts for diameter-controlled growth of single-walled carbon nanotubes

In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

In Situ Formation of Metal Carbide Catalysts

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