We present a parametric study on the growth of carbon nanotubes (CNTs) by spray pyrolysis of a biorenewable feedstock obtained from living pine trees, namely α-pinene. The analyzed variables were the type of catalyst, catalyst concentration, flow of reactants, and reaction time; all at a fixed temperature of 800 °C. The evaluation and optimization of these parameters was performed based on the yield and crystallinity of produced CNTs which were monitored by Raman spectroscopy, thermogravimetric analysis, X-ray diffraction, and high resolution transmission electron microcopy. Ferrocene as catalyst produced highly crystalline multiwalled CNTs while Co-and Fe-phtalocyanine produced nitrogendoped CNTs. A ferrocene concentration of 37 mg/mL and 5000 sccm flow were the optimal conditions to obtain the highest yield of crystalline CNTs. The variation of time produced crystalline CNTs with different lengths without modifying their crystallinity. The growth kinetics of MWCNTs follows a Deal− Grove model which indicates that the growth is diffusion-limited and suggests that the root growth mechanism controls the growth process.

2015): Synthesis of iron sulfide films through solid-gas reaction of iron with diethyl disulfide, Journal of Sulfur Chemistry, Iron sulfide films were synthesized by the solid-gas reaction of diethyl disulfide on iron foils in the temperature range of 658-768 K using a microbalance, where the film growth kinetics followed Deal-Grove behavior. Analysis of the films by X-ray photoelectron and Raman spectroscopies as well as X-ray diffraction and scanning electron microscopy analysis revealed the formation of combined FeS/FeS 2 (troilite/pyrite) films with a sheet-like morphology at low temperatures and only FeS (troilite) films with granular morphology at higher temperatures.

Samples of well-controlled nanoparticles consisting of alloys of cobalt and nickel of different atomic ratios were synthesized using wet chemical methods with oleylamine as the solvent and the reducing agent. These materials were characterized by a variety of techniques, including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Small amounts of heterogenized catalysts were prepared using alumina as the support. However, the potential for use of Co–Ni catalysts in CO hydrogenation was explored using a larger amount of Co–Ni/alumina catalyst prepared from standard aqueous impregnation methods and tested in a continuously stirred tank reactor (CSTR) for Fischer–Tropsch synthesis (FTS). Results are compared to a reference catalyst containing only cobalt. The heterogenized catalysts were characterized using synchrotron methods, including temperature programmed reduction with extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge spectroscopy (TPR-EXAFS/XANES). The characterization results support intimate contact between Co and Ni, strongly suggesting alloy formation. In FTS testing, drawbacks of Ni addition included decreased CO conversion on a per gram catalyst basis, although Ni did not significantly impact the turnover number of cobalt, and produced slightly higher light gas selectivity. Benefits of Ni addition included an inverted induction period relative to undoped Co/Al2O3, where CO conversion increased with time on-stream in the initial period, and the stabilization of cobalt nanoparticles at a lower weight % of Co.

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