Experimental verification of the formal nucleation and growth rate equations - Initial UH3 development on uranium surface

M. Brill, J. Bloch, M. H. Mintz

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


A Hot Stage Microscopy (HSM) technique was utilized for continuous observations of UH3 nucleation and growth on hydrogen exposed uranium (U-0.1 wt% Cr) surface. Such observations enabled the quantitative evaluation of both, nucleation rate function, N(t), and the average lateral growth velocity, u, of the individually growing nuclei. Knowing these kinetic parameters, the validity of the different assumptions made in the derivation of the formal nucleation and growth rate equations (i.e. the Avrami-Erofeev or Johnson-Mehl equations) can be checked. It was found that the basic assumption underlying the Avrami's approach, namely, the relation between the extended and the experimental reacted fractions, is very accurate over a wide range of surface coverages. However, the time dependence of the nucleation rate function was not monotonous, as commonly applied in the conventional treatments. Instead, the nucleation rate first accelerated, passed through a maximum and finally decayed again. At about 7-10% of the reaction, the nucleation rate decayed to zero, and saturation in the number of growing nuclei was attained. This nucleation behavior leads to overall kinetics which do not fit the simplified power law time dependence that is usually applied in the kinetic analysis of nucleation and growth processes.

Original languageEnglish
Pages (from-to)180-185
Number of pages6
JournalJournal of Alloys and Compounds
Issue number1-2
StatePublished - 20 Feb 1998


  • Growth
  • Hydrogen absorption
  • Nucleation
  • Rate equations
  • Uranium

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry


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