HEYNS, AM and RANGE, KJ (1991) THE POLYMORPHISM OF ALKALI-METAL FORMATES .2. A RAMAN-SPECTROSCOPIC STUDY OF THE KINETICS OF THE 1'-II PHASE-TRANSITION IN NAHCOO. MATERIALS RESEARCH BULLETIN, 26 (7). pp. 589-595. ISSN 0025-5408,
Full text not available from this repository.Abstract
When the room temperature phase of NaHCOO (NaHCOO-II) is heated, it undergoes a first-order transition to a high temperature phase (NaHCOO-I) at 500 K. Upon cooling this phase, an intermediate phase (NaHCOO-I') is formed and after an induction period of approximately 10 hours it slowly retransforms into the original phase NaHCOO-II at room temperature. The kinetics of this I'-II phase transition has been studied using Raman spectroscopy at various temperatures. Applying the log-log method, derived from the Avrami-Erofeev equation, to the experimental data, an average value of n = 1.70 has been obtained at 298 K. This indicates a diffusion-controlled process with initial growth of particles nucleated largely at the start of the transformation, but also including some nucleation throughout the growth process. At higher temperatures n decreases, possibly because the particles become more cylindrical in shape. An activation energy of E(A) = 45 +/- 1 kJ.mole-1 has been obtained for the phase transformation.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | POTASSIUM FORMATE; SODIUM; FORMATES |
| Depositing User: | Dr. Gernot Deinzer |
| Last Modified: | 19 Oct 2022 08:46 |
| URI: | https://pred.uni-regensburg.de/id/eprint/54968 |
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