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Effect of the Growth Treatment on Two‐Stage Nucleation Experiments
Author(s) -
Davis Mark J.
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00688.x
Subject(s) - nucleation , cluster size , cluster (spacecraft) , limiting , relaxation (psychology) , materials science , thermodynamics , chemical physics , chemistry , molecular dynamics , physics , computational chemistry , psychology , social psychology , mechanical engineering , computer science , engineering , programming language
Numerical simulations are presented that document the strong effect of a previously underappreciated portion of two‐stage thermal treatments used in the study of nucleation processes: the “heat‐up” process whereby samples are heated from “nucleation” conditions to “growth” conditions. The simulations indicate that two limiting regimes exist, dependent on (a) the cluster size distribution of as‐quenched glasses, (b) the temperatures used for nucleation and growth, and (c) the rates of heating and cooling: (1) all clusters larger than the critical size at growth conditions ( n * gr ) will grow to macroscopic size (the “standard” case); and (2) all clusters larger than the critical size at nucleation conditions ( n * nuc ) will grow to macroscopic size. In addition, cases in which the “effective critical size” ( n * eff ) is intermediate between n * gr and n * nuc can also occur. Cases in which n * eff < n * gr is manifested during nucleation experiments as an abrupt boost in crystal number density during the heat‐up from nucleation to growth conditions, as all clusters larger than n * eff are rapidly “flushed” past n * gr . For the system studied herein, this can lead to a 10 6 ‐fold increase in final number density within seconds to a few minutes. Finally, the importance of structural relaxation for this process is demonstrated by examining a case in which the nucleation temperature is below the nominal glass transition temperature.