Geração e otimização de microesferas vítreas produzidas a partir da cinza da casca do arroz

Abstract

Recently, research for sustainable materials applied to different types of products has generated a lot of interest both in the scientific community and in the industrial environment. Among the various sustainable materials, rice husk ash has been used as an alternative material to replace materials that include silica in its composition as construction materials. This is because the rice husk ash is very rich in silica, being, therefore, a natural substitute in any products that need this material in its composition. Therefore, the rice husk ash is also used in the production of silicate glass. Silicate glasses are used in several types of applications, fromthe production of bottle glass to windows, etc. Silicate glasses are also used in the production of microspheres that can be used from medical applications to construction materials, such as thermal and acoustic insulation as well as paints for road demarcation. Thus, this work focuses on making transparent glass using rice husk ash as a source of silica and mainly making an apparatus that allows the generation of solid microspheres from these glasses with potential application in road demarcation paints. Microspheres play an important role in the demarcation once they exhibit the phenomenon of retroreflection of incident light, causing a considerable increase in the intensity of the light reflected by the surface to occur with these microspheres embedded in the ink. The glasses produced, here called boron-sodium-calcium glasses, are constituted, in percentage of moles, by: 53.5 SiO2: 27 Na2O: 5 CaO: 14 B2O3: 0.5 Sb2O3, where ash was considered to have 91 % silica, based on X-ray fluorescence results. This composition was chosen since the results of Uv-Vis spectrophotometry showed a high optical transparency in the visible range of the electromagnetic spectrum, when compared with other compositions with changes in the percentage of silica and antimony oxide. In parallel, an experimental apparatus was developed for the generation and optimization of solid microspheres by horizontal flame. With this apparatus it was possible to generate microspheres with diameters less than 400 μm. The optimization of the microspheres was evaluated in terms of the number of passages of the glass particles through the flame. The morphology of the microspheres was evaluated through optical microscopy images. The results show that it is possible to generate retroreflective microspheres with good optical quality (transparent in the visible region of the electromagnetic spectrum) and morphological (spherical shape) with potential application in road signaling. More specifically, according to the NBR 16184 standard (horizontal road signage - glass spheres and microspheres - requirements and test methods), the microspheres produced with higher quality fit the type IB microspheres, which, in their highest percentage, must have diameters less than 212 μm.