A new methodology and model for characterization of nucleation and growth kinetics in solids

Abstract

A new kinetic model for three-dimensional heterogeneous nucleationHerein we describe a new experimental protocol and develop a corresponding kinetic model of phase change that together enable the decoupling of simultaneous nucleation and growth processes and quantification of their kinetics. Growth is effectively isolated from nucleation by dividing a phase transition into two isothermal stages: prenucleation, where product crystallites nucleate and grow concurrently, and growth, in which transformation is completed essentially entirely by the expansion of these ''seed'' grains. Using the model, the temperature dependence of growth may be extracted from converted fraction versus time data for specimens that are appreciably larger than the mean crystal grain size. Similarly, the growth velocity can be ascertained from thin films that exhibit thickness-dependent transition kinetics owing to geometric constraints imposed by the specimen size. The combination of grain growth kinetics and information derived from the transformation of unseeded materials then allows the subsequent calculation of the temperature dependence and absolute rates of nucleation. A preliminary assessment of this method ͑for the crystallization of amorphous solid water͒ indicates that the model captures the basic physics of ''seeded'' transformations and that the technique appears to be a viable method of quantifying simultaneous nucleation and growth in some solids.

Surface and bulk crystallization of amorphous solid water films: Confirmation of “top-down” crystallization

“…Note that the effects of enhanced surface mobility may extend several layers into the film. Our results mean that prior work using only surface sensitive techniques, such as desorption [9][10][11][12][13][14][15] and adsorbate physisorption [16][17][18][19][20], likely do not provide information relevant to bulk nucleation. Surface sensitive experiments may provide information relevant to processes in the environment or in astrophysical ices but it is the bulk nucleation rate that is relevant to processes in supercooled liquid water.…”

“…The crystallization of ASW films has been studied using a variety of methods including temperature programmed desorption (TPD) [9][10][11][12][13][14][15], adsorbate physisorption [16][17][18][19][20], electron diffraction [21,22], and infrared techniques [14,15,20,[23][24][25]. Most of these studies either report or assume that ASW crystallization proceeds via a random bulk nucleation and growth mechanism.…”

Crystallization Kinetics and Excess Free Energy of H2O and D2O Nanoscale Films of Amorphous Solid Water

“…The crystallization of ASW has been studied using a variety of techniques, including temperature programmed and isothermal desorption, − ,,,,− mass balance, infrared spectroscopy, ,,,,,− electron spectroscopy, − and inert gas physisorption. ,,,− In most of these studies, the crystallization kinetics were studied either isothermally or using only one heating rate. In this section, we study the effect of varying the heating rate on the crystallization kinetics and discuss the experimental advantages and physical insight afforded by such an approach.…”

Influencing FTO thin film growth with thin seeding layers: a route to microstructural modification

“…Thus, the growth step merges seeded islands into the final patterned thin film, with the kinetics of crystallite growth related to the velocity of crystallite expansion from the seed crystal. 61 The seed layer acts as the initial template for the first crystalline nucleation stage, promoting adhesion and increasing the growth rate at energetically more favourable sites, which results in dramatically increased growth and uniformity versus conventional, non-seeded CVD methods. An insufficient number of nucleation sites and/or an insufficient overlay time to promote growth in the regions between the seed sites means holey films are obtained (see Fig.…”