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Binary kinetics in the Y‐Ba‐Cu system: 2. Nanosized particles
Author(s) -
Wang Hong,
Thomson William J.
Publication year - 1995
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690410714
Subject(s) - kinetics , nucleation , particle (ecology) , diffusion , thermodynamics , particle size , chemistry , materials science , chemical engineering , mineralogy , physics , geology , oceanography , quantum mechanics , engineering
The kinetics of binaty mixtures of Y 2 O 3 – BaCO 3 –CuO (Ba–Cu) and Y 2 O 3 –CuO(Y–Cu) prepared by citrate sot‐gel techniques were studied in both air and helium. Particle sizes resulting from the sol – gel preparation were between 5 and 100 nm, and the prevailing kinetics differed significantly from those observed in the companion study of micron‐sized particles. That is, nucleation‐growth kinetics of the Avrami‐Erofe'eu type adequately model the kinetics over the entire conversion range as opposed to the diffusion mechanisms that describe the kinetics in larger sized particles. An alternate nucleation‐growth model, which neglects overlapping volumes during reaction (Austin – Rickett model), was also adequate in the Ba–Cu system where particle size/spacing was larger, but was only applicable in other reaction systems at lower conversions. Activation energies obtained from the Avrami‐ Erofe'ev were consistently lower than those from the Austin ‐ Rickett model, because the former model contains two parameters that are temperature‐sensitive.