�LLAND� ELEKTROMOS ER�T�R �LTAL INDUK�LT
MINT�ZATK�PZ�D�SSzerz�: VIR�NYI Zsanett V. �vfolyamT�mavezet�k: Dr. T�TH �gota egyetemi adjunktus,
Dr. HORV�TH Dezs� egyetemi adjunktusInt�zm�ny: Szegedi Tudom�nyegyetem, Term�szettudom�nyi Kar, Fizikai K�miai Tansz�k
A s�k k�miai front, mely egy autokatalitikus reakci� t�r-�s id�beli lej�tsz�d�sa, konvekci�mentes k�zegben elvesz�theti plan�ris jelleg�t �s t�rben v�ltoz�, cell�s szerkezet j�het l�tre, ha a reakt�ns fluxusa jelent�sebb a term�k�hez k�pest. Az autokataliz�tor r�szleges, immobilis, reverzibilis megk�t�s�vel vagy ionok k�zti reakci�ban a v�ndorl�si sebess�gek n�vel�s�vel a k�v�nt fluxusk�l�nbs�g el�rhet�.A klorition �s a tetration�tion k�zti reakci� savkataliz�lt, ahol a hidrog�nionok karboxil�tionokkal val� r�szleges megk�t�sevel a s�kfront destabiliz�lhat�. Mivel a reakci�ban ionok vesznek r�szt, a front sebess�ge �s szerkezete befoly�solhat� elektromos er�t�r alkalmaz�s�val. A dolgozat t�m�ja annak numerikus �s k�s�rleti vizsg�lata, hogy az �lland� elektromos er�t�r milyen hat�ssal van a mint�zatk�pz�d�sre savkataliz�lt reakci�ban.A rendszert le�r� differenci�legyenleteket fel�rva �s numerikusan megoldva megmutattuk, hogy megfelel� ir�ny� elektromos er�t�r alkalmaz�s�val k�v�nt mint�zat(s�kfront vagy cell�s szerkezet) stabiliz�lhat�.K�s�rleteinket n�trium-metakril�t tartalm� poliakrilamid g�lben hajtottuk v�gre, amellyel biztos�tottuk a konvekci�mentes k�zeget, �s a g�l n�trium-metakril�t tartalm�nak v�ltoztat�s�val kialak�tottuk a k�v�nt mint�zatot. Az �lland� elektromos er�teret nagy ioner�ss�g alkalmaz�s�val �rt�k el. A g�lt plexib�l k�sz�lt cell�ba helyezt�k, �s platinadr�tok ment�n elektrol�zissel s�kfrontot ind�tottunk, majd a megfelel� t�rer� alkalmaz�sa mellett a front v�ltoz�s�t sz�m�t�g�p �ltal vez�relt k�pfeldolgoz� rendszerrel r�gz�tett�k. A k�s�rletekben a modellsz�m�t�sokkal j� �sszhangban a k�v�nt mint�zatok alakultak ki.Kulcsszavak: mint�zatk�pz�d�s, k�miai front, savkataliz�lt reakci�, elektromos er�t�r
PATTERN FORMATION INDUCED BY A CONSTANT ELECTRIC FIELDAuthor: Zsanett VIR�NYI 5th year undergraduate studentSupervisors: Dr �gota T�TH assistant professor,
Dr Dezs� HORV�TH assistant professor
Institution: Department of Physical Chemistry, University of Szeged, Szeged
Planar chemical fronts arise from the spatiotemporal coupling of an autocatalyzed reaction. If the flux of the reactant is greater than that of the product, planar fronts may lose stability leading to cellular structures. The required difference between the flux of the reactant and the autocatalyst may be achieved by partial reversible immobilization of the autocatalyst or by separating the ionic species involved.The chlorite oxidation of tetrathionate ions is an acid-catalyzed reaction where planar fronts can be destabilized with partial binding of hydrogen ions to immobile carboxylate ions. Since the reaction involves ionic species, the pattern formation is strongly influenced by an externally applied electric field. This project is a numerical and experimental investigation of the effect of a constant electric field on planar fronts in an acid-catalyzed reaction.Partial differential equations of the system were solved numerically and it was shown that any pattern (planar front or cellular structure) can be stabilized with an appropriate electric field.The experiments were carried out in polyacrilamide hydrogel with varying sodium methacrylate content, to ensure the convection-free environment and to set the appropriate immobilization of hydrogen ions. High ionic strength was used to establish the costant electric field. The gel was placed between two plexi plates and the planar front was initiated electrochemically then the required electric field was applied. The propagation of fronts were monitored with a computer-controlled camera and processed using standard imaging techniques.The results of the experiments are in good agreement with that of the numerical modeling study.Keywords: pattern formation, chemical front, acid-catalyzed reaction, electric field