Spatiotemporal Self-organization In The Bray-Liebhafsky Reaction System

In nature,the fluid transport process can not be ignored,which has potential applications in carbon dioxide storage,crystal growth technology,oil exploitation and environmental remediation.The chemical reaction process involves changes in physical and chemical properties resulting in physical gradients and fluid transport,which in turn interacts with the chemical reactions to generate rich spatiotemporal self-organization behavior.The positive interaction between chemical reactions and fluid dynamics is known as chemohydrodynamics,whose research hotspot is the formation mechanism of spatiotemporal self-organization structures in reaction-diffusion-convection systems.At present,the chemohydrodynamics behavior in simple chemical reactions and autocatalysis reaction systems has been widely studied,such as the fingerprint pattern of acid-base neutralization reaction,the frontal instability（oscillation and acceleration）driven by buoyancy convection and surface tensions in IO₃^--As O₃^2-and Cl O₂^--S₃O₆^2-systems,etc.In the reaction-diffusion-convection medium,the laws of spatiotemporal self-organization driven by convections in the chemical oscillating reaction systems are one of the hot issues in the field of chemohydrodynamics.The coupling of multiple feedback loops in chemical oscillators can lead to more complex spatiotemporal self-organization behavior.The Bray Liebhafsky（B-L）reaction is one of the typical chemical oscillation reactions,which can exhibit sustained oscillation behavior in closed reaction systems.This thesis takes the B-L oscillating reaction system as the research object and systematically studies its spatiotemporal dynamic behavior in the homogeneous and reaction-diffusion-convection medium for further revealing the formation mechanism of reaction-diffusion-convection spatiotemporal self-organization in complex oscillating reaction systems.In the homogeneous reaction system,the oscillatory dynamics of the B-L reaction system was systematically studied through a combination of experimental and theoretical methods,which provided a foundation for the study of reaction-diffusion-convection spatiotemporal self-organization dynamics.During the experiment,the initial concentration of reactants,reaction temperature and light intensities were selected as control parameters to study their effects on the induction period,oscillatory duration,oscillatory period and amplitude of B-L homogeneous oscillations.The oscillatory parameter regions of B-L reaction were also obtained.Furthermore,I^-autocatalysis reaction was the key step to the generation of oscillation reaction.In terms of theoretical research,a 9-step reaction mechanism model was constructed for further explaining the homogenous dynamic behavior through numerical simulations and theoretical analysis.In a reaction-diffusion-convection medium,the spatiotemporal dynamic behavior of the B-L reaction system was systematically studied,and the formation mechanism of the three-stage pattern of the B-R reaction was further explained by adding Mn²⁺and CH₂（COOH）₂.Firstly,illumination was the key to the formation of convective spatiotemporal self-organization structures in the B-L reaction system.Under dark conditions,the B-L reaction system was in a low I₂ state with no convective structure generated.When the light intensity increased to 0.178 m W·cm^-2,the system generated a dendritic network structure.As the light intensity increased,the B-L reaction system exhibited a two-stage pattern structure from transient labyrinth structure to dendritic network structure,due to the fact of that light induces the generation of I?to promote the generation of I^-,which strengthened the autocatalysis reaction,and induced the generation of labyrinth structure.Reducing KIO₃ and increasing the concentration of H₂O₂ are beneficial for the generation of the first stage labyrinth structure,but have no significant impact on the second stage dendritic network structure.Secondly,the effects of Mn²⁺and CH₂（COOH）₂ on the reaction-diffusion-convection pattern in the B-L reaction system were investigated,and the influence of light intensity on the formation of the derived system pattern was systematically studied.In the Mn²⁺-B-L system,the system promotes the formation of HOO?through the Mn²⁺autocatalysis path,which can effectively shorten the induction period of the reaction,promote the formation labyrinth structure in the first stage,and do not affect patterns in the second stage.In the MA-B-L system,the organic autocatalysis path induced by MA has promoted autocatalysis reaction,which made a three-stage convection structure occur（front wave→high I₂stage→dendritic network structure）.The increase of light intensity was conducive to the emergence of labyrinth structures in the first stage and help to shorten the induction periods.Finally,in the Mn²⁺-MA-B-L system,namely Briggs Rauscher（B-R）reaction system,the influence of light intensity on the formation of three-stage pattern was further studied.It was proposed that the coupling effect of photocatalysis path,Mn²⁺autocatalysis path and organic autocatalysis path in the B-R system was the fundamental reason for the formation of three-stage convection structure in the B-R reaction system.Finally,in the B-L reaction system,the addition of trace I^-further verified that the labyrinth structure in the first stage was caused by the autocatalysis reaction of I^-.Through the study of sub reactions H₂O₂-I^-and I₂-H₂SO₄,it was found that the dendritic structure of the B-L reaction system mainly comes from the reaction between H₂O₂ and iodine-containing species.At the same time,the cover experiment and double cell experiment have demonstrated that the Marangoni effect caused by I₂ evaporation plays an important role in the pattern formation.The thesis has 61 pictures,3 tables,and 114 references.