Didactic experiment of a one-dimensional process of solidification from nuclei at random to a linear polycrystal. Part I: Nuclei, nuclei distances, and grain lengths

Abstract

We show theexperimental verification of a didactic model which is named “one-dimensional (1D) process of solidification (crystallization) from nuclei at random to linear polycrystal”.

This one-dimensional model assumes: 1) Nuclei are distributed “at random”. 2) From these the grains start to grow instantaneously, circularly, and with the same and constant growth rate. 3) Growth stops where two grains touch. This model was theoretically treated by Schulze [1,2] and about 20 statements were derived; here, these statements were experimentally verified. To that end, the 1D model is experimentally approximated by a spun filament of 15-μm diameter. The filament consists of polypropylene and, therefore, the grains are spherulites; it is embedded in a glue, which acts as a capillary tube. A later heat-treatment of the embedded filament (including melting, nucleation, grain (spherulite) growth) finally shows the nuclei, the nuclei distances, and the grain (spherulite) lengths. These values are measured: there are 1601 nuclei and the mean nuclei distance (and the mean grain length) is 361 μm. The growth rate of the grain (spherulite) is 4.15 μm/min. A comparison between theory and experiment shows agreement.