Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies. Abstract-Rice husk (RH) is a rich silica by-product of rice production with great potential for industrial applications. After combustion, a rice husk ash rich in silica is obtained, with some amount of other inorganic components constituted mainly of alkaline elements. The study was conducted to characterize both the rice husk and rice husk ash (RHA) in order to evaluate their constitution and the form in which mentioned impurities are present. The amorphous silica crystallized when heated under certain conditions. In this way, the examination of the crystallization process of rice husk ash with different impurity levels was also carried out by varying the temperature, time and heating conditions. The study reveals a preferential distribution of silica at the cell tip of the outer RH surface cells. The impurities form compounds with combinations of different elements such as Ca and Mg, P and K, and are mainly localized below the inner surface in the form of spherical and cuboidal shapes, as well as irregular morphologies..
E El le ec ct tr ro oc ch he em mi ic ca al l e ex xt tr ra ac ct ti io on n o of f m mi ic cr ro oa al ll lo oy y c ca ar rb bi id de es s i in n N Nb b--s st te ee el l ( (• •) )A.L. Rivas * , E. Vidal ** , D.K. Matlock *** and J.G. Speer *** A Ab bs st tr ra ac ct t An electrochemical extraction technique was evaluated as a characterization method of precipitates in microalloyed steels. To carry out this study, a fully precipitated Nb-modified SAE 8620, was used. The investigation was accomplished by varying the electrolyte composition and the filter pore sizes used to collect the particles. The quantification of Nb was performed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Microscopy examination was also performed on extraction replicas and on residues collected in the acetate filters. Additionally, X-ray diffraction analysis (XRD) on the collected residues containing the precipitates was accomplished. The results showed that the dissolution rate is faster in the electrolyte consisting of 10 vol% HCl in water. Additionally, transmission electron microscopy (TEM) analysis along with chemical analysis by ICP-AES, showed that (Nb,Ti)C particles were collected in acetate filters with a pore size much larger than the precipitate size.K Ke ey yw wo or rd ds s (Nb,Ti)C precipitates; Electrochemical extraction; Steel matrix dissolution; Microalloyed steel; Anodic dissolution; Filtration.E Ex xt tr ra ac cc ci ió ón n e el le ec ct tr ro oq qu uí ím mi ic ca a d de e c ca ar rb bu ur ro os s d de e m mi ic cr ro oa al le ea ac ci ió ón n e en n N Nb b--a ac ce er ro o R Re es su um me en n La técnica de extracción electroquímica fue empleada para evaluar su efectividad en la caracterización de precipitados en aceros microaleados. Para realizar el estudio, se utilizó un acero SAE 8620 modificado con niobio. La investigación se llevó a cabo variando la composición del electrolito utilizado en la disolución electroquímica de la matriz y el tamaño de poro de los filtros usados para recolectar las partículas precipitadas. La cuantificación del contenido de Nb se hizo por espectroscopia de emisión atómica de plasma (ICP-AES). Además, las muestras obtenidas por réplicas de extracción y las provenientes de los residuos recolectados en los filtros fueron analizadas mediante microscopía electrónica de transmisión. Estas últimas muestras, también fueron caracterizadas por difracción de rayos X. Los resultados mostraron que la velocidad de disolución electroquímica de las muestras es mayor en el electrolito acuoso con 10 vol. % HCl. Adicionalmente, el análisis mediante microscopía electrónica de transmisión, en combinación con los análisis químicos mediante ICP-AES, mostró que las partículas de (Nb,Ti)C son recolectadas en filtros de acetato con tamaños de poro mucho mayor que el tamaño de las partículas precipitadas. P Pa al la ab br ra as s c cl la av ve e (Nb,Ti)C precipitados; Extracción electroquímica; Disolución electroquímica de la matriz de acero; Aceros microaleados; Disolución anódica de matriz...
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