The structure and properties of V doped TiO2 nanometric powders, synthesized using sol-gel method... more The structure and properties of V doped TiO2 nanometric powders, synthesized using sol-gel method were studied. The precursors employed were Ti(OC2H5)4 as TiO2 source and VO(Acac)2 as V2O5 source. The molar ratios of TiO2:V2O5 were 98:2 and 99.95:0.05, respectively. The obtained gels were thermally treated for 1 h at 300°C with a heating rate of 1°C/min in order to eliminate the water and organic residues and to obtain crystallized nanometric powders. The characterization of the powders was realized by thermogravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), specific surface area and porosity measurements. The obtained powders were also tested as catalyst for water splitting and oxidation of methanol. The correlation between composition, structure and catalytic properties of the samples was established.
Mesoporous CoFe2O4 nanoparticles were synthesized through a simple precipitation method using cet... more Mesoporous CoFe2O4 nanoparticles were synthesized through a simple precipitation method using cetyltrimethylammoniumbromide (CTAB) as surfactant. Variation of surfactant concentration has been investigated to synthesize CoFe2O4 nanoparticles with superior textural properties.The samples were characterized by FTIR,TG/DSC, XRD, SEM, N2 adsorption–desorption technique, and vibrating sample magnetometer (VSM). The obtained results revealed that the surface area and magnetic properties of CoFe2O4 are significantly influenced by the initial concentration of CTAB. The capacity of the synthesized samples to adsorb lead ions from aqueous solution and the factors affecting the adsorption process, like contact time and pH of the media, were evaluated. The Pb2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb2+ adsorption capacity was 32.11 mgg1 according to the Langmuir isotherm.
ABSTRACT The nanostructured multilayer silica-titania or silica-titania-alumina films doped with ... more ABSTRACT The nanostructured multilayer silica-titania or silica-titania-alumina films doped with Er3+ were prepared by sol-gel method. The sol-gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2-10%TiO2 or 85%SiO2-10%TiO2-5% Al2O3 and 0.5% Er2O3.
Salted environments are the natural habitat of certain halophilic microorganisms, both bacteria a... more Salted environments are the natural habitat of certain halophilic microorganisms, both bacteria and archaea extremophiles which are a source of enzymes (extremozymes) with extreme stability. Taking into account that extremozymes are stable and active under hard conditions of pH and ionic strength, their study as biocatalysts is attractive. Many halophiles secrete proteolytic enzymes which enable the degradation of proteins and peptides in the natural hypersaline environments. The interactions of various nanostructures with biological molecules attracted a serious interest in the last years in order to understand their use for human life purposes and benefits. This paper deals with approaching the functionalization of silica and titanate nanostructures with halotolerant proteases. Since salted environments are widely used in Roumania for recreational activity, it is of high interest to investigate the impact of new materials like silica and titanate nanotubes on metabolites of haloph...
Sol-gel process allows the synthesis of powders with a more elaborate structure and morphology, i... more Sol-gel process allows the synthesis of powders with a more elaborate structure and morphology, improving thus the reactivity of the synthesized material. Binary Oxide nanoparticles can have properties superior to those of the pure components. Oxides nanopowders in the Al2O3-TiO2 system have been mainly used as raw materials for advanced polycrystalline Al2TiO5 ceramics synthesis. However, Al2TiO5 based powders have also other applications as for example in petroleum hydro-treatments or as potential adsorbents in the decontamination of chemical warfare agents. In the present work Al2O3-TiO2 oxides were obtained by a sol-gel process and were characterized by thermogravimetric/differential thermal analysis, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, BET specific surface area and porosity analysis. The obtained results were discussed comparatively with those obtained for the monocomponent oxides in order to establish new and better potential for their appli...
ABSTRACT In this research, both commercially available (Cloisite 93A) and advanced functionalized... more ABSTRACT In this research, both commercially available (Cloisite 93A) and advanced functionalized clay mineral were used to obtain clay–epoxy nanocomposites. Cloisite 93A was modified with three different alkoxysilanes and was incorporated in Epon 862 epoxy resin which was crosslinked using tetraethylenepentamine as a curing agent. The determination of color grades of the composite samples was followed. The morphology of the composites was analyzed using X-ray diffraction and ESEM micrographs which provided insight into the fracture mechanism. Thermal behavior was evaluated by TGA and DSC and thermo-mechanical properties of the cured samples have been evaluated by DMA technique. The data indicated that intercalated or agglomerated silylated Cloisite–epoxy nanocomposites were obtained. The silylated Cloisite samples are more compatible with the polymer matrix due to their enhanced hydrophobic behavior leading to an improvement in storage modulus and stiffness but also to the increase of glass transition temperature up to 30 °C.
ABSTRACT A novel ternary Ti-15Zr-10Nb alloy with innovative microstructural and mechanical proper... more ABSTRACT A novel ternary Ti-15Zr-10Nb alloy with innovative microstructural and mechanical properties and very good long-term corrosion resistance in simulated physiological solutions was studied in this paper. Optical and scanning electron microscopy (SEM) observations revealed alpha + beta biphasic Widmanstatten microstructure with characteristic interleaving lamella of alpha and beta phases. Energy dispersive spectroscopy (EDS) measurements gave good compositional homogeneity with wt.% contents of 75 +/- 5% for Ti, 15 +/- 2% for Nb, and 10 +/- 2% for Zr. The XRD pattern was indexed to a biphasic crystalline structure containing the hexagonal a phase with calculated lattice parameters of a = 2.92 angstrom, c = 4.63 angstrom and the cubic beta phase with calculated lattice parameter of a = 3.19 A. The alloy has very good mechanical properties: Young's modulus of 64 GPa, very close to that of the human bone; superior ultimate tensile strength, appropriate 0.2% yield strength and strain to fracture to those of Ti. The alloy native passive film has a thickness of 5.5 +/- 0.5 nm and contains protective TiO2, ZrO2 and Nb2O5 oxides (X-ray photoelectron spectroscopy - XPS analysis). The cyclic voltammetry in Ringer's solutions indicated a nobler electrochemical behaviour of the alloy in comparison with Ti due to the beneficial influence of the alloying elements, which participate with their oxides to the compactness, thickening, reinforcement of the native passive film. The electrochemical impedance spectra were modelled with an electric equivalent circuit comprising two time constants: for inner, compact layer and outer, porous slightly inferior protective layer.
ABSTRACT Mesoporous powders were obtained by sol-gel process in the MgO-TiO2 system. The scanning... more ABSTRACT Mesoporous powders were obtained by sol-gel process in the MgO-TiO2 system. The scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermogravimetric/differential thermal analysis (TG/DTA), powder X-ray diffraction (XRD) and nitrogen adsorption/desorption measurements have been used to characterize the morphology, phase evolution, crystallinity and pore structure of the obtained materials. The adsorption capacity of the synthesized powders for CO2 and CO was also investigated. The results were discussed comparatively with those obtained for the monocomponent oxides in order to establish new and better potential for their applications.
ABSTRACT CuFe2−xCrxO4 spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluc... more ABSTRACT CuFe2−xCrxO4 spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mössbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mössbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained spinel powders depend on the concentration of Cr3+ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic spinel type structure for x=0.5, 1.0 and a tetragonal structure for x=0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mössbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe2−xCrxO4 spinels.
ABSTRACT Polymer-clay nanocomposites were synthesized by solution polymerization method using adv... more ABSTRACT Polymer-clay nanocomposites were synthesized by solution polymerization method using advanced functionalized clay and vinyl benzyl trimethyl ammonium chloride as monomer. First stage consisted in the silylation of a commercial organo-modified clay-Cl 20A using alkoxysilanes with different chain lengths. In the second step, the synthesis and characterization of polymer-nanocomposites were followed. To evaluate the clay functionalization process as well as the final polymer-clay products, thermogravimetric, X-ray diffraction, dynamic light scattering, Fourier transform infrared spectroscopy and three test liquid contact angles analyses were used. The loss of ammonium ions from commercial clay, the grafting degree, the lengths and the nature of alkyl chain influence the dispersion of the advanced modified clay into the polymer solution and, furthermore, the properties of the final polymer-clay nanocomposite film. Graphical Abstract Polymer-clay nanocomposites were obtained by solution polymerization using advanced functionalized clay and a water soluble monomer. The loss of ammonium ions, the grafting degree, the lengths and the nature of alkyl chain influenced the dispersion of the modified clay into the polymer solution and the properties of the final hybrid film.
The structure and properties of V doped TiO2 nanometric powders, synthesized using sol-gel method... more The structure and properties of V doped TiO2 nanometric powders, synthesized using sol-gel method were studied. The precursors employed were Ti(OC2H5)4 as TiO2 source and VO(Acac)2 as V2O5 source. The molar ratios of TiO2:V2O5 were 98:2 and 99.95:0.05, respectively. The obtained gels were thermally treated for 1 h at 300°C with a heating rate of 1°C/min in order to eliminate the water and organic residues and to obtain crystallized nanometric powders. The characterization of the powders was realized by thermogravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), specific surface area and porosity measurements. The obtained powders were also tested as catalyst for water splitting and oxidation of methanol. The correlation between composition, structure and catalytic properties of the samples was established.
Mesoporous CoFe2O4 nanoparticles were synthesized through a simple precipitation method using cet... more Mesoporous CoFe2O4 nanoparticles were synthesized through a simple precipitation method using cetyltrimethylammoniumbromide (CTAB) as surfactant. Variation of surfactant concentration has been investigated to synthesize CoFe2O4 nanoparticles with superior textural properties.The samples were characterized by FTIR,TG/DSC, XRD, SEM, N2 adsorption–desorption technique, and vibrating sample magnetometer (VSM). The obtained results revealed that the surface area and magnetic properties of CoFe2O4 are significantly influenced by the initial concentration of CTAB. The capacity of the synthesized samples to adsorb lead ions from aqueous solution and the factors affecting the adsorption process, like contact time and pH of the media, were evaluated. The Pb2+ adsorption followed pseudo-second-order kinetics, and the maximum Pb2+ adsorption capacity was 32.11 mgg1 according to the Langmuir isotherm.
ABSTRACT The nanostructured multilayer silica-titania or silica-titania-alumina films doped with ... more ABSTRACT The nanostructured multilayer silica-titania or silica-titania-alumina films doped with Er3+ were prepared by sol-gel method. The sol-gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2-10%TiO2 or 85%SiO2-10%TiO2-5% Al2O3 and 0.5% Er2O3.
Salted environments are the natural habitat of certain halophilic microorganisms, both bacteria a... more Salted environments are the natural habitat of certain halophilic microorganisms, both bacteria and archaea extremophiles which are a source of enzymes (extremozymes) with extreme stability. Taking into account that extremozymes are stable and active under hard conditions of pH and ionic strength, their study as biocatalysts is attractive. Many halophiles secrete proteolytic enzymes which enable the degradation of proteins and peptides in the natural hypersaline environments. The interactions of various nanostructures with biological molecules attracted a serious interest in the last years in order to understand their use for human life purposes and benefits. This paper deals with approaching the functionalization of silica and titanate nanostructures with halotolerant proteases. Since salted environments are widely used in Roumania for recreational activity, it is of high interest to investigate the impact of new materials like silica and titanate nanotubes on metabolites of haloph...
Sol-gel process allows the synthesis of powders with a more elaborate structure and morphology, i... more Sol-gel process allows the synthesis of powders with a more elaborate structure and morphology, improving thus the reactivity of the synthesized material. Binary Oxide nanoparticles can have properties superior to those of the pure components. Oxides nanopowders in the Al2O3-TiO2 system have been mainly used as raw materials for advanced polycrystalline Al2TiO5 ceramics synthesis. However, Al2TiO5 based powders have also other applications as for example in petroleum hydro-treatments or as potential adsorbents in the decontamination of chemical warfare agents. In the present work Al2O3-TiO2 oxides were obtained by a sol-gel process and were characterized by thermogravimetric/differential thermal analysis, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, BET specific surface area and porosity analysis. The obtained results were discussed comparatively with those obtained for the monocomponent oxides in order to establish new and better potential for their appli...
ABSTRACT In this research, both commercially available (Cloisite 93A) and advanced functionalized... more ABSTRACT In this research, both commercially available (Cloisite 93A) and advanced functionalized clay mineral were used to obtain clay–epoxy nanocomposites. Cloisite 93A was modified with three different alkoxysilanes and was incorporated in Epon 862 epoxy resin which was crosslinked using tetraethylenepentamine as a curing agent. The determination of color grades of the composite samples was followed. The morphology of the composites was analyzed using X-ray diffraction and ESEM micrographs which provided insight into the fracture mechanism. Thermal behavior was evaluated by TGA and DSC and thermo-mechanical properties of the cured samples have been evaluated by DMA technique. The data indicated that intercalated or agglomerated silylated Cloisite–epoxy nanocomposites were obtained. The silylated Cloisite samples are more compatible with the polymer matrix due to their enhanced hydrophobic behavior leading to an improvement in storage modulus and stiffness but also to the increase of glass transition temperature up to 30 °C.
ABSTRACT A novel ternary Ti-15Zr-10Nb alloy with innovative microstructural and mechanical proper... more ABSTRACT A novel ternary Ti-15Zr-10Nb alloy with innovative microstructural and mechanical properties and very good long-term corrosion resistance in simulated physiological solutions was studied in this paper. Optical and scanning electron microscopy (SEM) observations revealed alpha + beta biphasic Widmanstatten microstructure with characteristic interleaving lamella of alpha and beta phases. Energy dispersive spectroscopy (EDS) measurements gave good compositional homogeneity with wt.% contents of 75 +/- 5% for Ti, 15 +/- 2% for Nb, and 10 +/- 2% for Zr. The XRD pattern was indexed to a biphasic crystalline structure containing the hexagonal a phase with calculated lattice parameters of a = 2.92 angstrom, c = 4.63 angstrom and the cubic beta phase with calculated lattice parameter of a = 3.19 A. The alloy has very good mechanical properties: Young's modulus of 64 GPa, very close to that of the human bone; superior ultimate tensile strength, appropriate 0.2% yield strength and strain to fracture to those of Ti. The alloy native passive film has a thickness of 5.5 +/- 0.5 nm and contains protective TiO2, ZrO2 and Nb2O5 oxides (X-ray photoelectron spectroscopy - XPS analysis). The cyclic voltammetry in Ringer's solutions indicated a nobler electrochemical behaviour of the alloy in comparison with Ti due to the beneficial influence of the alloying elements, which participate with their oxides to the compactness, thickening, reinforcement of the native passive film. The electrochemical impedance spectra were modelled with an electric equivalent circuit comprising two time constants: for inner, compact layer and outer, porous slightly inferior protective layer.
ABSTRACT Mesoporous powders were obtained by sol-gel process in the MgO-TiO2 system. The scanning... more ABSTRACT Mesoporous powders were obtained by sol-gel process in the MgO-TiO2 system. The scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermogravimetric/differential thermal analysis (TG/DTA), powder X-ray diffraction (XRD) and nitrogen adsorption/desorption measurements have been used to characterize the morphology, phase evolution, crystallinity and pore structure of the obtained materials. The adsorption capacity of the synthesized powders for CO2 and CO was also investigated. The results were discussed comparatively with those obtained for the monocomponent oxides in order to establish new and better potential for their applications.
ABSTRACT CuFe2−xCrxO4 spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluc... more ABSTRACT CuFe2−xCrxO4 spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mössbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mössbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained spinel powders depend on the concentration of Cr3+ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic spinel type structure for x=0.5, 1.0 and a tetragonal structure for x=0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mössbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe2−xCrxO4 spinels.
ABSTRACT Polymer-clay nanocomposites were synthesized by solution polymerization method using adv... more ABSTRACT Polymer-clay nanocomposites were synthesized by solution polymerization method using advanced functionalized clay and vinyl benzyl trimethyl ammonium chloride as monomer. First stage consisted in the silylation of a commercial organo-modified clay-Cl 20A using alkoxysilanes with different chain lengths. In the second step, the synthesis and characterization of polymer-nanocomposites were followed. To evaluate the clay functionalization process as well as the final polymer-clay products, thermogravimetric, X-ray diffraction, dynamic light scattering, Fourier transform infrared spectroscopy and three test liquid contact angles analyses were used. The loss of ammonium ions from commercial clay, the grafting degree, the lengths and the nature of alkyl chain influence the dispersion of the advanced modified clay into the polymer solution and, furthermore, the properties of the final polymer-clay nanocomposite film. Graphical Abstract Polymer-clay nanocomposites were obtained by solution polymerization using advanced functionalized clay and a water soluble monomer. The loss of ammonium ions, the grafting degree, the lengths and the nature of alkyl chain influenced the dispersion of the modified clay into the polymer solution and the properties of the final hybrid film.
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