Selective hydrogen gas sensor using CuFe 2 O 4 nanoparticle based thin film

Hydrogen gas sensors based on CuFe2O4 nanoparticle thin films are presented in this work. Each gas sensor was prepared by depositing CuFe2O4 thin film on a glass substrate by dc sputtering inside a high vacuum chamber. Argon inert gas was used to sputter the material from a composite sputtering target. Interdigitated metal electrodes were deposited on top of the thin films by thermal evaporation and shadow masking. The produced sensors were tested against hydrogen, hydrogen sulfide, and ethylene gases where they were found to be selective for hydrogen. The sensitivity of the produced sensors was maximum for hydrogen gas at 50 °C. In addition, the produced sensors exhibit linear response signal for hydrogen gas with concentrations up to 5%. Those sensors have potential to be used for industrial applications because of their low power requirement, functionality at low temperatures, and low production cost.Scopu

Influence of the Type of Cement on the Durability of Concrete Structures Exposed to Various Carbonation Environments in Greece: A Contribution to the Sustainability of Structures

The research objective of this paper is to investigate the effect of different types of cement and different climatic conditions on the durability of reinforced concrete structures to understand and address issues of durability and erosion. The types of cement used were CEM I 42.5N, CEM II/A-M (P-LL) 42.5N and CEM II/B-M (W-P-LL) 32.5N. Mixtures of three different cement mortars and six different concretes were prepared with these three types of cement. Cement mortars were produced according to the European standard EN 196-1. Concrete mixtures were of the strength classes C25/30 and C30/37. Concrete mixtures produced according to the specifications of the European standard EN 206 may have a shorter service life due to carbonation-induced corrosion if the choice of the cement type is not made carefully. The results indicate that the carbonation rate of concrete mixtures is significantly influenced by the type and strength class of the cement used. Using meteorological data from six regions of Greece, an empirical carbonation prediction model for these regions was obtained

Hybrid Porous Molybdenum Disulfide Monolith for Liquid Removal of Dibenzothiophene

Molybdenum disulfide (MoS₂) has been historically used as a hydrodesulfurization (HDS) catalyst and industrial lubricant. Because of its 2D nature and unique properties, MoS₂ is being considered for new applications in catalysis and electronics. In addition, there is great interest in designing new physical forms of MoS₂ that will allow for improved implementation of its properties, such as a continuous porous monolithic form. In this work, we report a new synthesis method to fabricate continuous, centimeter-sized, open cell hybrid foam (monolith) that consists of molybdenum sulfide and carbon as its main constituents. The hybrid foam was characterized using XRD, electron microscopy (SEM and TEM), Raman, FTIR, and EELS spectroscopy. Furthermore, liquid adsorption of dibenzothiophene (DBT) in toluene solvent was used to test the foam affinity to adsorb organosulfur compounds. The monolith is of low density and exhibits high specific adsorption capacity compared to existing materials reported in the literature

Iron-substituted cubic silsesquioxane pillared clays:Synthesis, characterization and acid catalytic activity

Novel pillared structures were developed from the intercalation of iron-substituted cubic silsesquioxanes in a sodium and an acid-activated montmorillonite nanoclay and evaluated as acid catalysts. Octameric cubic oligosiloxanes were formed upon controlled hydrolytic polycondensation of the corresponding monomer (a diamino-alkoxysilane) and reacted with iron cations to form complexes that were intercalated within the layered nanoclay matrices. Upon calcination iron oxide nanoparticles are formed which are located on the silica cubes (pillars) and on the surfaces of the clay platelets. Acid activation of the nanoclay was performed in order to increase the number of acid active sites in the pristine clay and thus increase its catalytic activity. A plethora of analytical techniques including X-ray diffraction, thermal analyses, Fourier transform infrared, electron paramagnetic resonance, Raman, Mossbauer and X-ray photoelectron spectroscopies and porosimetry measurements were used in order to follow the synthesis steps and to fully characterize the final catalysts. The resulting pillared clays exhibit a high specific area and show significant acid catalytic activity that was verified using the catalytic dehydration of isopropanol as a probe reaction. (C) 2017 Elsevier Inc. All rights reserved

Facile MoS2 Growth on Reduced Graphene-Oxide via Liquid Phase Method

Single and few-layers MoS2 were uniformly grown on the surface of chemically reduced graphene oxide (r-GO), via a facile liquid phase approach. The method is based on a simple functionalization of r-GO with oleyl amine which seems to affect significantly the MoS2 way of growth. Scanning-transmission-electron microscopy (STEM) analysis revealed the presence of single-layer MoS2 on the surface of a few-layers r-GO. This result was also confirmed by atomic-force microscopy (AFM) images. X-ray photoemission spectroscopy (XPS) and Raman spectroscopy were used for in-depth structural characterization. Furthermore, we have successfully applied the method to synthesize MoS2 nanocomposites with multi wall carbon nanotubes (CN) and carbon nanofibers (CNF). The results demonstrate clearly the selective MoS2 growth on both carbon-based supports

Facile MoS2 Growth on Reduced Graphene-Oxide via Liquid Phase Method

10.3389/fmats.2018.00029Frontiers in Materials52

Presentation_1_Facile MoS2 Growth on Reduced Graphene-Oxide via Liquid Phase Method.pdf

<p>Single and few-layers MoS₂ were uniformly grown on the surface of chemically reduced graphene oxide (r-GO), via a facile liquid phase approach. The method is based on a simple functionalization of r-GO with oleyl amine which seems to affect significantly the MoS₂ way of growth. Scanning-transmission-electron microscopy (STEM) analysis revealed the presence of single-layer MoS₂ on the surface of a few-layers r-GO. This result was also confirmed by atomic-force microscopy (AFM) images. X-ray photoemission spectroscopy (XPS) and Raman spectroscopy were used for in-depth structural characterization. Furthermore, we have successfully applied the method to synthesize MoS₂ nanocomposites with multi wall carbon nanotubes (CN) and carbon nanofibers (CNF). The results demonstrate clearly the selective MoS₂ growth on both carbon-based supports.</p