Identificação, evolução e transformação de compostos de silício em uma biomassa tratada termicamente até altas temperaturas

• Autor(a) principal: Yapuchura Ocaris, Enrique Ronald.
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/11094
• topic: Biomass; Phytoliths; Silicon carbide; Carbonaceous materials; SEM-EDS; Raman spectroscopy; XRD; Biomassa; Fitólitos; Sílica; Espectroscopia Raman; Materiais carbonosos; MEV-EDS; DRX; Física; 53

Scanning electron microscopy (SEM) coupled with X-ray dispersive energy (EDS) spectroscopy, Raman spectroscopy and X-ray diffraction (XRD) were successfully used to observe the location and morphology of silica (SiO2) phytoliths in carbonaceous materials derived from biomass and its transformation into silicon carbide (SiC) and SiO2 particles at high heat treatment temperatures (HTT). The analyzes were conducted on carbonaceous materials (chars) derived from the endocarp of babassu coconut (ECB), which naturally contains 1.6 wt.% of silica in its mineral matter. It was observed that ECB chars with HTT between 500 and 1200 °C have globular echinate morphotype SiO2 phytoliths with sizes between 12 and 16 µm; these phytoliths are mainly concentrated around the surface of the char submillimetric fibers present in the endocarp of babassu coconut and also in the general carbonaceous matrix of the material. Phytoliths are not found within the submillimetric char fibers. At the HTT of 1200 °C the phytoliths begin to rounded, and above 1300 °C HTT, most of the phytoliths decompose, part of the silicon reacts with carbon forming nanocrystalline ß-SiC (crystallite size ~ 35 nm). Another part generates numerous (tens to hundreds) amorphous or nanostructured SiO2 microand sub-microparticles (with sizes predominantly below 2 µm) are observed at sites previously occupied by phytoliths. Few rounded phytoliths survive at 1400 °C HTT, but disappear in higher HTTs (1600-2000 °C). It is likely that the ensembles of SiO2 micro- and submicroparticles observed at many sites correspond to the remaining inner remaining part of the original phytoliths whose most external SiO2 structures (at and near the surface) decompose and participate in the carbothermic reaction for the formation of SiC. In addition, this study is complemented with the Raman spectroscopy characterization of the carbonaceous structure of the ECB heat treated samples, reporting characteristic parameters of the Raman D and G bands of carbonaceous materials.