Amine impregnated porous silica gel sorbents synthesized from water-glass precursors for CO2 capturing

In this work, porous silica gel-solid beads have been made from economically affordable water-glass precursors via sol-gel nano casting technique. A stable nanometric silica sol was prepared first from water glass and studied for surface potential and sol to gel transition. A free-flow, injectable gel was obtained upon aging the sol which was then assembled into spherical silica beads in a chemical bath. A surface area of 304.7m2g-1 was obtained for water glass derived silica gel beads. These gel beads were impregnated with 3-aminopropyltrimethoxysilane (APTMS) and polyethylenimine (PEI) active functional groups at different percentages for turning the gel beads as sorbents for CO2 gas adsorption. The effect of amine loading on the thermal stability, morphology as well as porosity was studied and was correlated with CO2 adsorption values. Depending upon the amount of amine loaded in the gel support CO2 uptake was found varied. These amine modified silica gel porous adsorbents showed CO2 adsorption capacity at temperatures as low as 100°C; samples modified with 15wt% PEI had CO2 adsorption capacity of 1.16mmolg-1 at 50°C. © 2015 Elsevier B.V

Enhanced catalytic and supercapacitor activities of DNA encapsulated b-MnO2 nanomaterials

A new approach is developed for the aqueous phase formation of flake-like and wire-like b-MnO2 nanomaterials on a DNA scaffold at room temperature (RT) within a shorter time scale. The b-MnO2 nanomaterials having a band gap energy B3.54 eV are synthesized by the reaction of Mn(II) salt with NaOH in the presence of DNA under continuous stirring. The eventual diameter of the MnO2 particles in the wire-like and flake-like morphology and their nominal length can be tuned by changing the DNA to Mn(II) salt molar ratio and by controlling other reaction parameters. The synthesized b-MnO2 nanomaterials exhibit pronounced catalytic activity in organic catalysis reaction for the spontaneous polymerization of aniline hydrochloride to emeraldine salt (polyaniline) at RT and act as a suitable electrode material in electrochemical supercapacitor applications. From the electrochemical experiment, it was observed that the b-MnO2 nanomaterials showed different specific capacitance (Cs) values for the flake-like and wire-like structures. The Cs value of 112 F g�1 at 5 mV s�1 was observed for the flake-like structure, which is higher compared to that of the wire-like structure. The flake-like MnO2 nanostructure exhibited an excellent long-term stability, retaining 81% of initial capacitance even after 4000 cycles, whereas for the wire-like MnO2 nanostructure, capacitance decreased and the retention value was only 70% over 4000 cycles. In the future, the present approach can be extended for the formation of other oxide-based materials using DNA as a promising scaffold for different applications such as homogeneous and heterogeneous organic catalysis reactions, Li-ion battery materials or for the fabrication of other high performance energy storage device

Effect of Nano-engineered SiO2/Al2O3 Mixed Matrix Microcomposite Fillers on Thermal, Mechanical and Tribological Properties of Epoxy Polymers

International audienceEffect of Nano-engineered SiO2/Al2O3 Mixed Matrix Microcomposite Fillers on Thermal, Mechanical and Tribological Properties of Epoxy Polymer

Synthesis of yttrium doped nanocrystalline ZnO and its photocatalytic activity in methylene blue degradation

Yttrium doped zinc oxide was prepared by microwave irradiation of Y (NO3)3·6H2O and Zn(NO3)2·4H2O as precursors, in ethanol–water medium. Highly polar ethanol–water medium (30/70, v/v) with hexamine and urea assist the formation of ZnO nuclei very rapidly in a specific fashion. Furthermore, Y3+ ions infiltration into Zn(OH)2 precipitate was facilitated by microwaves (2.45 GHz, 950 W). Yttrium doped nanocrystalline ZnO (ZnO-99 and ZnO-95) was formed with 1 and 5 mol% yttrium precursor. The powder was morphologically characterized with XRD, DLS, SEM and TEM. Photocatalytic activity of microwave treated Y3+ doped ZnO was tested by studying the oxidation of methylene blue solution in a batch reactor. The studies showed that the catalytic reaction followed second order kinetics. Based on the results obtained from photocatalytic studies, efficiencies of various ZnO samples were found to be in this order: ZnO-A > ZnO-99 > ZnO-95 > ZnO-R that is, Y3+ doped ZnO was not as effective as commercial undoped ZnO. However, ZnO-95 had shown better stability, antiphotocorrosive nature and reusability among the samples tested in this study

Surface engineered silica mesospheres – A promising adsorbent for CO2 capture

Carbon dioxide adsorption capacities of amine modified sol-gel SiO2 mesospheres were evaluated. The sorbents were prepared from readily available sodium metasilicate via sol-gel process. Three amines were used for surface modification purpose, namely Tetraethylenepentamine (TEPA), Tetraethylenepentamine acrylonitrile (TEPAN) and a mixture of Aminopropyltrimethoxysilane (APTMS) coupled with the two amines individually. The sorbents were characterized and carbon dioxide adsorption studies at 50 and 75 °C were conducted. CO2 adsorption isotherms of the functionalized samples at both the temperatures showed that the sorbents coupled with APTMS gave better adsorption performance than with individual amines. The sample with mixture of APTMS and TEPA showed the best performance among the samples studied with a CO2 adsorption capacity of 3.26 mmol g-1 at 75 °C. The TEPAN immobilized sorbents exhibited faster kinetics at both the temperatures of 50 and 75 °C; henceforth it appears that in addition to the amine content present in the sample, effective distribution of the amines on the surface and inside the pores that are accessible to CO2 determine the actual working capacity of the adsorbent

Full transition from metal to ceramic by direct oxidation of metallic cobalt powder

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