Autodiffusion le long des sous-joints dans la phase ‘plastique’ de l'acide pivalique (2,2-dimethyl propanoique acide)

Publisher Website
Google Scholar
Abstract
SUB-GRAIN-BOUNDARY SELF-DIFFUSION IN ‘PLASTIC’ PIVALIC ACID (2,2-DIMETHYL PROPANOIC ACID) The sub-grain-boundary self-diffusion coefficient has been measured in the orientationally disordered (plastic) phase of pivalic acid. High purity (99·9999%) polycrystals were used. A sub-structure was introduced by compression creep of single crystals at room temperature. The average grain size was about 200 μm and the misorientation about 3°. A thin layer of tracer (molecules of pivalic acid labelled with 14C) was deposited on each sample. Concentration-penetration curves were established by the serial-sectioning technique. To calculate D′δ, where δ is the sub-grain-boundary width and D′ the sub-grain-boundary self-diffusion coefficient, Le Claire's solution was used; it describes Suzuoka's and Whipple's analysis in the case of the sectioning technique. The slope variation of concentration-penetration curves versus time of diffusion anneal shows that D′δ is characteristic of the sub-grain-boundary self-diffusion. From 281 to 297 K, D′δ is given by D′δ (m3 s−1) = (3 ± 0·7)10−9 exp[-(47 ± 3) kJ mol−1]/RT, the value 47 kJ mol−1 being the activation energy of the process which is significantly lower than the value of lattice self-diffusion activation energy, 59 ± 1 kJ mol−1. Results using the crude Fisher solution agree with this analysis of the experiments.

This publication has 9 references indexed in Scilit: