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Titolo:
Investigation of the mechanism of sol-gel formation in the Sr(NO3)(2)/citric acid/ethylene glycol system by solution state Sr-87 nuclear magnetic resonance spectroscopy
Autore:
Li, XH; Agarwal, V; Liu, ML; Rees, WS;
Indirizzi:
Georgia Inst Technol, Sch Chem & Biochem, Atlanta, GA 30332 USA Georgia Inst Technol Atlanta GA USA 30332 Biochem, Atlanta, GA 30332 USA Georgia Inst Technol, Inst Mol Design, Atlanta, GA 30332 USA Georgia Inst Technol Atlanta GA USA 30332 l Design, Atlanta, GA 30332 USA Georgia Inst Technol, Sch Mat Sci & Engn, Atlanta, GA 30332 USA Georgia Inst Technol Atlanta GA USA 30332 i & Engn, Atlanta, GA 30332 USA
Titolo Testata:
JOURNAL OF MATERIALS RESEARCH
fascicolo: 11, volume: 15, anno: 2000,
pagine: 2393 - 2399
SICI:
0884-2914(200011)15:11<2393:IOTMOS>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
EXCHANGE KINETICS; OXYGEN PERMEATION; SODIUM-CATION; OXIDES; COMPLEXATION; ION; DIBENZO-24-CROWN-8; DIBENZO-18-CROWN-6; DECOMPLEXATION; NITROMETHANE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
--discip_EC--
Citazioni:
30
Recensione:
Indirizzi per estratti:
Indirizzo: Liu, ML Georgia Inst Technol, Sch Chem & Biochem, Atlanta, GA 30332 USA Georgia Inst Technol Atlanta GA USA 30332 , Atlanta, GA 30332 USA
Citazione:
X.H. Li et al., "Investigation of the mechanism of sol-gel formation in the Sr(NO3)(2)/citric acid/ethylene glycol system by solution state Sr-87 nuclear magnetic resonance spectroscopy", J MATER RES, 15(11), 2000, pp. 2393-2399

Abstract

The polymerization mechanism of a modified Pechini process was investigated by Sr-87 nuclear magnetic resonance spectroscopy for the mixed solution of strontium nitrate, citric acid, and ethylene glycol. The C-ratio (the ratio of citric acid to metal ions in the polymer complex) is suggested to have a strong influence on the quality of the derived film. An analysis of thechemical shift variation, as a function of C-ratio, indicates the presencein the solution of two species: solvated strontium ions and strontium ionsbound to the polymer complex, with a stoichiometry of 1:7. A polymeric precursor model based on this stoichiometry is proposed. Through a relaxation rate study of the strontium sites, it was found that the polymerization mechanism is predominantly bimolecular within the concentration region bring studied. The equilibrium rate constant for the polymerization was calculatedto be 10(4) s(-1). A kinetic study of the fast cation exchange between thetwo identified strontium sites indicates that the inhomogeneity of the polymeric network leads to film cracking during pyrolysis.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/12/20 alle ore 13:23:53