Formação em Cristais de ZnO em Matriz Porosa de Amido Degradado

Abstract

Due to numerous applications of porous matrices and zinc oxide, the main objective of the study is to investigate the formation of zinc oxide crystals in a porous matrix of cassava starch. The different stages of structural starch transformation (gelatinization and retrogradation) were investigated to find the best processing parameters (time, temperature and starch/water volumetric ratio). After optimization of the parameters, the porous matrix was obtained by the degradation process. The water evaporation curves in the zinc precursor salt solutions (Zn(NO3)2.6H2O) were raised to identify the times of supersaturation and crystal formation, as well as the treatment temperatures for transformation of the crystals in the oxide phase. zinc. Two impregnation times were chosen, one below supersaturation and another in the supersaturation region, of the porous matrix in the precursor salt solutions. The impregnated matrices were subjected to the same treatment temperatures to transform the crystals into the zinc oxide phase. The structural transformations undergone by starch during the different stages were characterized by X-ray diffraction, calculating the degree of crystallinity. The crystallization of the solutions and formation of zinc oxide, in the different stages, was also characterized by X-ray diffraction. The results were analyzed by the Line Profile Analysis (LPA) methods (Sherrer, Scherrer-Modified and Williamson-Hall) , obtaining the sizes of the crystalline domains and the microdeformations of the zinc oxide crystals. For morphological characterization optical and atomic force microscopy were used. In general, the research can conclude that the thermal degradation process of starch after retrogradation is effective in obtaining a porous material, which can be used as a support for the formation of oxide crystals that form at lower temperatures. In addition, the material preparation route is low-cost and environmentally friendly.