română L. PALL, J – L. BOBET, E. ANDRONESCU
Abstract
We have studied the influence of the substitution of Al for Ni in the ternary systems RENi5-xBx (RE=Gd, Y). The compounds synthesized in the pseudo-ternary systems RENi4-xAlBx (RE=Gd, Y) were studied in terms of their crystal structure, chemical composition and hydrogen sorption properties. Most of the compounds obtained in these systems crystallize with the CeCo4B-type structure RENi3AlB, with Al atoms replacing Ni. The partial replacement of Ni by Al observed leads to a decrease of lattice parameters compared to ternary RENi4B compounds. The new pseudo-binary phase GdB3 was also observed in this study for the first time. Finally, it is reported that the compounds do not show any affinity towards hydrogen, with no absorption observed.
Keywords
intermetallics, borides, ternary compounds
GEORGETA VELCIU, CRISTIAN ŞEITAN, ALINA DUMITRU, VIRGIL MARINESCU, MARIA PREDA, ALINA MELINESCU
Abstract
Solid electrolyte fuel cells (SOFC), the cleanest sources of electricity generation, are formed of three main components: solid electrolyte, cathode and anode. The cathode and anode (electrodes) are activation support of electrochemical reactions and transporting charge carriers, electrons and partly or totally ions. With electrolyte forms a triple interface "gas - electronic solid - solid ionic" that changes abruptly the conduction mechanism from electronic (TPB - Triple Phase Boundary) to ionic. The study of processes taking place in the TPB in a solid electrolyte fuel cell is important for optimization of electrochemical reactions. This paper presents the structural and microstructural characteristics of interfaces cathode / electrolyte / anode in a fuel cell with solid electrolyte with following ceramic components: solid electrolyte on CeO2 based with addition of calcium oxide and yttrium oxide, cathode of perovskite type based on lanthanum manganite doped (LSM) with strontium and anode a cermet from cerium oxide doped with gadolinium (Ni-CeGd). Mineralogical composition of components used for the fuel cell was performed by X-ray diffraction. Its microstructure was determined by electron microscopy, and the distribution of chemical elements at interfaces cathode / electrolyte and anode / electrolyte was examined by EDX. Cathode and anode surface condition was examined by AFM. The results show a good adhesion of the layers used as electrodes on solid electrolyte support.
Keywords
SOFC, cathode, electrolyte, anode, microstructure
ALINA MELINESCU, CHRISTU ŢÂRDEI, CLAUDIA MARIA SIMIONESCU, VIRGIL MARINESCU, ANGELICA MICLEA
Abstract
Natural or synthetic hydroxyapatite [Ca10(PO4)6(OH)2] has a high exchange capacity for divalent heavy metal ions and is used to treat wastewater containing such ions. The reaction mechanism of hydroxyapatite with lead salts is carried out by dissolution followed by precipitation pyromorphite. As-synthesized HAp granules were analyzed by X-ray diffraction and FTIR spectroscopy. For the study of retention of lead ions were added Ca-hydroxyapatite granules in a solution of lead nitrate. By treatment with a solution of lead nitrate in all cases the chemical reaction leading to the formation pyromorphite, which is a positive result, as it is a compound of the less soluble lead.
Keywords
hydroxyapatite, XRD, FTIR, pyromorphite
AURELIA CRISTINA NECHIFOR, LUCIAN DĂNUŢ GHINDEANU, CRISTINA ORBECI, OCTAVIAN DORCA, EUGENIA EFTIMIE TOTU
Abstract
In this paper it is presented the synthesis and characterization of magnetite nanoparticles coated with polyethylene glycol (PEG) and functionalized with cyanuryl chloride. The synthesis of magnetic core through modified Massart method, starts from high stability materials and it uses polyethylenglycols with variable molecular weight (300, 600, 1000, 2000, 4000 and 10,000 D). The obtained nanoparticles were structurally and morphologically analyzed by help of SEM, TEM, FT-IR spectroscopy and EDAX. The chemical responsiveness of the obtained nanoparticles was evaluated by help of FTIR spectrometry, titration and electrochemical evaluation.
Keywords
magnetic nanoparticles, PEG, cyanuril chloride
ALINA MARIA HOLBAN, ALEXANDRU MIHAI GRUMEZESCU, ANTON FICAI, CARMEN MARIANA CHIFIRIUC, VERONICA LAZĂR, RADU RĂDULESCU
Abstract
During recent years there is an increased interest in magnetite nanoparticles for their wide use in biomedical applications, as prevention of microbial colonization and targeted drug delivery systems. They could stabilize the volatile active components of the essential oils improving their antimicrobial activity. Here we report a newly prepared nano-bio-active coated surface for improved antimicrobial activity of classical wound dressings. Our results demonstrate that the reported nano-modified wound care textiles exhibit a great anti-fungal biofilm activity. These properties recommend the recently fabricated nano-bio-active coatings for the design of new antimicrobial medical surfaces.
Keywords
hydroxyapatite, XRD, FTIR, pyromorphite
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Year
2013
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Issue
43 (3)
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Pages
300-305
OVIDIU OPREA, CRISTINA DANIELA GHIŢULICĂ, GEORGETA VOICU, BOGDAN ŞTEFAN VASILE, ANGELICA OPREA
Abstract
Nanocatalysts of TiO2 doped with 0.5% Fe (III) were prepared by the sol-gel method at 75°C. Titanium (IV) tetrabutoxide (Ti(OC4H9)4), anhydrous iron (III) chloride (FeCl3), acetic acid and acetyl acetone were used as starting materials. The synthesized materials were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM, HRTEM, SAED) and specific surface area by Brunauer, Emmett and Teller method (BET). The photocatalytic activity, measured by UV-Vis adsorption spectroscopy, was evaluated by the photocatalytic degradation of methylene blue (MB) in water under UV irradiation. From XRD and SAED analyses, the results indicate that anatase was obtained at temperature up to 800°C; above this temperature the rutile was obtained, with low photocatalytic properties. The TEM, HRTM and BET analyses showed the presence of nano size and mesoporous particles with high surface area.
Keywords
sol-gel method, anatase, rutile, Fe-doping, photocatalytic properties
IOAN LAZĂU, CRISTIAN CORCOVEANU, CORNELIA PĂCURARIU, RADU IOAN LAZĂU
Abstract
NiAl2O4 spinel was obtained by combustion synthesis method, using nickel and aluminum nitrate and a fuel mixture consisting of urea-dosed in relation to aluminum nitrate and maleic anhydride-dosed in relation to nickel nitrate. The compatibility of each metal nitrate and the respective fuel was established based on the thermal analyses, considering the decomposition temperature range of each reagent. Following the combustion reaction initiated at 500°C results the designed phase NiAl2O4 . By further annealing at 900°C there is only a slight increase of the crystallite size, from 15.8 nm to 16.7 nm. Using the fuels in 10% excess of the stoichiometric amount required, after the combustion results a mixture of NiAl2O4, NiO and metallic Ni; after further annealling of this mixture at 1000°C, NiAl2O4 is formed as single phase. NiAl2O4 specific blue color development, in which the chromophore cations Ni2+ are present tetrahedralyl and octahedrally coordinated, requires the annealing at 900°C of the resulted powders after combustion.
Keywords
combustion synthesis, X-ray diffraction, thermal analysis, nickel spinel.
ŞTEFANIA STOLERIU, ANAMARIA PUIA, SORIN ION JINGA, ECATERINA ANDRONESCU
Abstract
The paper’s aim is to present the preparation and characterization of ceramic sensors in SnO2 – ZrO2 binary system, using nanopowders obtained through co-precipitation from the corresponding chlorides.
All nanopowders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD results show specific diffraction lines of tin oxide solid solutions and tetragonal zirconia solid solutions. The TEM examination shows particle size being below 10 nm with tendency of agglomeration in large agglomerates.
For ceramic sensors obtaining, the nanopowders were shaped and thermally treated in air for sintering, at temperatures between 900° and 1300°C, for 2 hours.
In order to determine the sensitivity of ceramic sensors, the electrical resistanced was measured in air, in methane saturated atmosphere and in methanol vapor saturated atmosphere, as well. The obtained sensors are more sensitive to methanol than to methane, the compositions with a higher amount of tin oxide showing higher sensitivity values to both methanol and methane.
Keywords
ceramic sensors, tin oxide, sensitivity, nanopowders