Reaction Kinetics in Fractals

EZEQUIEL V ALBANO

Enciclopedia of Complexity and System Science.

Springer Verlag

Lugar: Heildelberg; Año: 2008; p. 1 - 18

Processes involving reaction among atoms, molecules and particles in general, are ubiquitous both, in Nature as well as in laboratories. After the introduction of the concept of fractals by B. Mandelbrot in the 1980s, it has been realized that a wide variety of reactions takes place in fractal media, leading to the observation of anomalous behaviour, i. e. the so called ``fractal reaction kinetics''. The study of this subject has received considerable theoretical attention and a huge numerical effort has also been devoted to achieve an improved understanding. Furthermore, among the practical examples of fractal reaction kinetics one can quote exciton annihilation in composite materials, chemical reactions in the pores of membranes, charge recombination in colloids and clouds, coagulation, polymerisation and growth of dendrites, etc.Another scenery for the study of reaction kinetics in fractals is in the field of heterogeneous catalysis. In fact, it is well known that most catalysts are constituted by small, catalytically active particles, supported by highly porous (fractal) substrata. So, it is not surprising that this field of research has become particularly active due to, on the one hand, the practical and technological relevance, but also due to the occurrence of quite interesting and challenging phenomena such as irreversible phase transitions, oscillatory behaviour, chaos and stochastic resonance, propagation and interference of chemical waves, interface coarsening, metastability and hysteretic effects, etc.