Firuze Okyay

Production of Carbon Nanotubes over Fe-FSM-16 Catalytic Material: Effect of Acetylene Flow Rate and CVD Temperature

In this article, a high-yield synthesis of high-quality carbon nanotubes (CNTs) using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16, by chemical vapor deposition (CVD), using acetylene as a hydrocarbon source, is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy, Raman spectroscopy and thermogravimetric analysis. Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However, the acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were multi-walled carbon nanotubes (MWCNTs). High-resolution transmission electron micrographs of samples reveal the multi-layer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed.

An Improved Technique for the Exfoliation of Graphene Nanosheets and Utilization of their Nanocomposites as Fuel Cell Electrodes

Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional 2D honeycomb lattice. The graphene sheets in graphite interact with each other through van der Waals forces to form layered structure. The first graphene sheets were obtained by extracting monolayer sheets from the three-dimensional graphite using a technique called micromechanical cleavage in 2004 [. There are numerous attempts in the literature to produce monolayer graphene sheets by the treatment of graphite. The first work was conducted by Brodie in 1859 and GO was prepared by repeated treatment of Ceylon graphite with an oxidation mixture consisting of potassium chlorate and fuming nitric acid [. Then, in 1898, Staudenmaier produced graphite oxide (GO) by the oxidation of graphite in concentrated sulfuric acid and nitric acid with potassium chlorate [. However, this method was time consuming and hazardous. Hummers and Offeman found a rapid and safer method for the preparation of GO and in this method graphite was oxidized in water free mixture of sulfuric acid, sodium nitrate and potassium permanganate [.

The Conversion of Low-rank Kilyos Coal to Nitrogeneous Fertilizers

Abstract The aim of this work is to convert the low-rank Kilyos coal to a material that could be used as a nitrogenous fertilizer. Incorporation of nitrogen into this Kilyos coal was accomplished by oxidative ammoniation, which was a two-step process involving oxidation with nitric acid followed by a treatment by ammonia. The nitrogen content of the raw coal increased from 0.8% to 8.3–9.3% after ammoniation process. Trace element concentrations in the nitro-coal, humic acid, and oxy-ammoniated coal samples were within the acceptable ranges to be used as nitrogenous fertilizer. Therefore the oxy-ammoniated products could be considered as high-value fertilizers.

Thermal Decarboxylation of Demineralized Turkish Beypazari Lignite by the Catalytic Effect of Cr2+, Fe2+, and Co2+

Abstract Demineralized Beypazari lignite were thermally decarboxylated using Cr2+, Fe2+, and Co2+ as decarboxylation catalysts. Effective loadings of Cr2+, Fe2+, and Co2+ were 2, 5, and 3%, respectively. The calorific values of the demineralized lignite samples increased after the thermal decarboxylation experiments to values about 6, 12, and 15% higher than that of the untreated demineralized sample, when Cr2+, Fe2+, and Co2+, respectively, were used as catalysts. The most effective catalyst, with respect to the lowest activation energy attained, was Cr2+. Decarboxylation temperatures using Cr2+, Fe2+, and Co2+ as catalysts were 150, 100, and 200°C, respectively.