Synthesis and characterization of non-transformable tetragonal YSZ nanopowder by means of Pechini method for thermal barrier coatings (TBCs) applications

A simple soft chemical method of synthesizing tetragonal yttria stabilized zirconia nanopowders is described here. Zirconium oxy-chloride octahydrate and yttrium nitrate hexahydrate were taken as a source of zirconium, citric acid was taken as a chelating agent, and ethylene glycol was used as a polysterification agent. The synthesized powders were characterized by X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, transmission electron microscopy, field emission scanning electron microscope, Fourier transform infrared spectroscopy and Raman spectroscopy. Furthermore, precise cell parameters were calculated in order to exactly determine non-transformable tetragonal crystal structure, which was the best zirconia phase for thermal barrier coatings applications. In this process, tetragonal yttria stabilized zirconia nanopowders could be prepared at a temperature of 1,000 °C and the process was simple and cost-effective.     

Plasma Catalytic Synthesis of Ammonia Using Functionalized-Carbon Coatings in an Atmospheric-Pressure Non-equilibrium Discharge

We investigate the synthesis of ammonia in a non-equilibrium atmospheric-pressure plasma using functionalized-nanodiamond and diamond-like-carbon coatings on α-Al₂O₃ spheres as catalysts. Oxygenated nanodiamonds were found to increase the production yield of ammonia, while hydrogenated nanodiamonds decreased the yield. Neither type of nanodiamond affected the plasma properties significantly. Using diffuse-reflectance FT-IR and XPS, the role of different functional groups on the catalyst surface was investigated. Evidence is presented that the carbonyl group is associated with an efficient surface adsorption and desorption of hydrogen in ammonia synthesis on the surface of the nanodiamonds, and an increased production of ammonia. Conformal diamond-like-carbon coatings, deposited by plasma-enhanced chemical vapour deposition, led to a plasma with a higher electron density, and increased the production of ammonia.     

A comparison between Suzuki cross-coupling reaction and direct arylation in the synthesis of new antibacterial imidazo-pyrazines/pyridazines

Two efficient synthetic routes to preparation of 2,3-diarylimidazo[1,2-a]pyrazines and 2,3-diarylimidazo[1,2-b]pyridazines are described. The procedures involve a Suzuki cross-coupling reaction and a palladium-catalyzed direct arylation at position 3 and finally a comparative study is achieved. The antibacterial activities of the synthesized compounds in vitro were measured and the results showed that most products presented moderate to good antibacterial activities. Compounds 3a , 3c , 3j , 3k , 3l , and 3n revealed obvious potency against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli with minimum inhibitory concentration values of 32 μg/mL, which were better compared with the others.