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Le riviste italiane del Novecento. Atti del convegno, a cura di Vito Moretti e Umberto Russo.
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Synthesis and structural characterization of Fe3+-doped calcium hydroxyapatites: role of precursors and synthesis method
No full textThis work evaluates the role of Ca and P precursors and of two different preparation methods, ceramic and hydrothermal, in the synthesis of undoped- and Fe3+-doped hydroxyapatite (HA), and tests the Fe3+solubility limits in HA. Previous studies have noted that different synthesis conditions lead to different products in variable amounts and recent literature quotes the highest amount of Fe3+ substituting for Ca in the HA structure in the range 0.2-0.5 as a function of temperature. Samples were characterized by X-ray powder diffraction, Mössbauer and Infrared spectroscopies. The samples obtained by the ceramic method at 800° contain mixtures of B-type carbonate-apatite and other phosphates whose type and number depend on Ca and P precursors. Samples synthesized at higher temperatures contain mixtures of hydroxyapatite, tricalcium phosphate and of magnetic phases, as hematite and ferrite, whose relative amounts depend on nominal composition and thermal treatment. Samples obtained by a hydrothermal route are richer in HA phase with respect to the solid state one, even if the obtained HA percentage depends on the pH. Mössbauer results suggest that Fe3+ is randomly distributed between Ca1 and Ca2 sites. At the highest doping levels a reduction takes place with the formation of iron(II) and magnetite
Determinazione della temperatura massima di cottura di manufatti ceramici: verifica dellâ€TMaffidabilità del metodo della ricottura
No full textCoordination polymers formed by diorganotin dichlorides with 2,5-bis(4-pyridyl)-1,3,4-thiadiazole
No full textDichlorodimethyltin and dichlorodiphenyltin form 1:1 adducts with 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (L1). MOssbauer spectra of the compounds SnCl2(CH3)(2) . L1 (1) and SnCl2(C6H5)(2) . L1 . 0.3CH(2)Cl(2) (2) are consistent with a monodimensional polymeric structure containing L1 as a bifunctional bridging ligand. The octahedral coordination geometry at the tin atom is very distorted, with a C-Sn-C bond angle of about 150' for both 1 and 2. (c
Intracrystalline disorder in spinels: sensitivity of cell parameter a and Mossbauer data.
No full textIn spinels accurate determination of cell edge a is crucial , if X-ray powder diffraction methods are used to derive the variations in cation distributions due to thermal treatment. The reproducibility of this parameter was tested by carrying out several a measurements on two spinel samples (VASA and CR5A) the first a near spinel end member and the second a chromium-rich sample, both untreated and quenched from high temperatures. Further Mossbauer spectra were performed on the same powders with the aim of understanding the intracrystalline distributions responsible for the detected variations in a
Inorganic-organic interpenetrating frameworks: oxi-hydroxide iron(III) inside poly-4-vinylpyridine-methacrylic acid-N,N '- methylenebisacrylamide. Part I: Synthesis and macrostructure
No full textA carboxylic gel-type resin, poly-4-vinylpyridine-methacrylic acid-N,N'-methylenebisacrylamide is designed and synthesized in order to be able to incorporate both Fe-III and, potentially, also Au-III in its polymer framework. Along with the gradual substitution of H+ with Na+, of Na+ with Fe3+/3 and after a very controlled and gradual precipitation of Fe-III as oxihydroxides induced by the hydrolysis of urea directly inside the nanoporous domains of the metalated resin particles, an organic-inorganic composite is obtained. The material is characterized with TGA, ESEM, XRMA and Mossbauer spectroscopy
Complex of phthalocyaninatoiron(II) with diazoles
No full textThe complexes of formula [Fe(Pc)(diazole)(2)]. nH(2)O (Pc = phthalocyaninato dianion; diazole = pyrazole, 3(5)-methylpyrazole, indazole and 1-phenylimidazole) have been prepared and characterized. The Mossbauer spectra of the bisadducts of [Fe(Pc)] with diazoles show values of isomer shift close to those of the corresponding complexes with pyridines, but somewhat smaller values of quadrupole splittin
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