Marina Aghayan

Template-Assisted Wet-Combustion Synthesis of Fibrous Nickel-Based Catalyst for Carbon Dioxide Methanation and Methane Steam Reforming

Efficient capture and recycling of CO2 enable not only prevention of global warming but also the supply of useful low-carbon fuels. The catalytic conversion of CO2 into an organic compound is a promising recycling approach which opens new concepts and opportunities for catalytic and industrial development. Here we report about template-assisted wet-combustion synthesis of a one-dimensional nickel-based catalyst for carbon dioxide methanation and methane steam reforming. Because of a high temperature achieved in a short time during reaction and a large amount of evolved gases, the wet-combustion synthesis yields homogeneously precipitated nanoparticles of NiO with average particle size of 4 nm on alumina nanofibers covered with a NiAl2O4 nanolayer. The as-synthesized core-shell structured fibers exhibit outstanding activity in steam reforming of methane and sufficient activity in carbon dioxide methanation with 100% selectivity toward methane formation. The as-synthesized catalyst shows stable operation under the reaction conditions for at least 50 h.

Graphene Covered Alumina Nanofibers as Toughening Agent in Alumina Ceramics

Graphene is a promising component for next-generation high-performance structural and multifunctional composite materials. Graphene deposited onto nanofibers of high aspect ratio can serve as reinforcement agent for improving ceramic fracture toughness and electroconductivity. It was found that quality and quantity of graphene sheets on the fiber surface essentially depends on the pyrolysis of carbon source conditions such as gas flow, duration, temperature and the composition of the gas mixture. The alumina/graphene composites of 10 and 15 wt% of nanofibers covered by graphene were produced by spark plasma sintering (SPS) at 1380 °C. Both composites show improvement in mechanical and electrical properties as compared to the monolithic alumina. The main advantage of the graphene growth on the fibers surface is a lack of complicated step of constituents mixing. Graphene platelets are believed to act as toughening agents prevailing crack propagation under loading.

Hybrid Graphene/Alumina Nanofibers for Electrodonductive Zirconia

Ceramic materials have become of high industrial importance in some applications as their properties outperform ones of metallic components. However, use of ceramics is limited due to the difficulties in shaping. Electrically conductive ceramics can be machined by Electro-Discharge Machining (EDM) irrespective of its hardness or strength. In this study, yttria stabilized zirconia (YTZP) conductive composite was produced by incorporation of the cost-effective graphene coated alumina nanofibers (ANFC) into the matrix. Almost fully dense YTZP/5 vol.% ANFC nanocomposite was obtained by spark plasma sintering (SPS) at 1250 °C with uniaxial pressure of 40 MPa. Scanning electron microscopy observation of the microstructures showed that ANFCs were homogeneously dispersed in the matrix. Addition of ANFC resulted in slightly decreased mechanical properties, but the electrical resistivity of the composite dropped 9 orders of magnitude compared to monolithic zirconia, exhibiting 1.4 Ω∙m, satisfying the required condition for the EDM.

Fabrication of NiO/NiAl2O4 Nanofibers by Combustion Method

Nickel aluminate spinel (NiAl2O4) has received attention as a catalyst solid support due to its stability, strong resistance to acids and alkalis and high melting point. The properties and quality of the catalysts are heavily affected by crystal size, morphology, phase homogeneity and surface characteristics of the materials, which themselves are dependent on method and parameters of processing rout. In this work, we report on the fabrication of novel NiAl2O4 nanofibers covered by NiO nanolayer by combustion method.The XRD patterns show that the combustion technique was excellent to prepare NiO/NiAl2O4 nanofibers. The crystallite sizes of NiAl2O4 and NiO were found to be around 27 and 19 nm correspondingly. Scanning electron micrographs (SEM) and Energy dispersive X-ray (EDX) analysis showed that the NiO/NiAl2O4 nanofibers with more than 20 nm in diameter were consist of NiAl2O4 core and NiO outer layer.