Browsing by Author "Gacitua, William"

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    Maximizing bolaina wood utilization: extraction of cellulose nanofibers from sawdust waste
    (2024) Diaz, Shirley; Mora, Hector Gonzales; Gacitua, William; Bustos, Cecilia; Reyes-Contreras, Pablo; Aguayo, Maria Graciela
    This study focuses on the utilization of bolaina sawdust waste from the Peruvian Amazon for the production of cellulose nanofibers (CNFs). Bolaina is known for its rapid growth and extensive wood usage, which generate significant amounts of sawdust waste. The objective of this research was to physicochemically study this biomass source and the conversion of this waste into valuable nanocellulosic materials. The results showed that CNF yields from holocellulose (CNF-BH) and alpha-cellulose (CNF-B alpha) gave high nanofibrillation yields of 80.6% and 74.7%, respectively. The CNFs were disintegrated into nanoscale fibers using microfluidizer treatment, resulting in CNF-BH displaying a thicker, gel-like aspect, while CNF-B alpha showed a more liquid aspect. The FTIR spectra showed peaks associated with -CH2 groups, C = O stretching vibrations of carboxyl and acetyl groups in hemicelluloses, and cellulose I and II vibrations. TGA analysis demonstrated that both CNFs had two stages of degradation, with a maximum peak degradation temperature of 240 degrees C in the first stage and 310 to 350 degrees C in the second stage. The XRD patterns of CNF-BH and CNF-B alpha showed differences in the crystallinity index, with values of 68.1% and 75.4%, respectively. The differences in crystallinity between the two CNFs can be explained by the alkaline purification method to which the alpha-cellulose sample was subjected. Overall, the CNFs exhibited a high crystallinity index and thermal stability, making them promising candidates for various applications in materials science and aiding in the development of sustainable materials.
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    Optical and mechanical properties of Zr-oxide doped TiO2/SiO2 anti-reflective coatings for PV glass covers
    (2022) Zambrano-Mera, Dario F.; Espinoza-Gonzalez, Rodrigo; Villarroel, Roberto; Rosenkranz, Andreas; Carvajal, Nicolas; Pintor-Monroy, Maria I.; Montano-Figueroa, A. Gabriela; Arellano-Jimenez, Maria J.; Quevedo-Lopez, Manuel; Valenzuela, Paulina; Gacitua, William
    Multi-layer systems are frequently used as anti-reflective coatings (ARCs) due to their excellent optical properties. However, these systems suffer from erosive degradation (wear), thus urgently seeking alternative ways to improve their mechanical properties while maintaining their optical response. To tackle this problem, we propose to dope multi-layer TiO2/SiO2 coatings with Zr-oxides to enhance their crystalline structure and density/ compactness, as well as to form Si-Zr-O bonds. We explore the effect of Zr-oxide doping on the microstructure as well as the optical and mechanical properties of multi-layer TiO2/SiO2 coatings with the overall aim to synergistically induce enhanced optical and mechanical properties. Therefore, homogeneous 250 nm thick multi-layer TiO2/SiO2 coatings doped with Zr-oxides (different atomic concentrations) were deposited on glass substrates by magnetron sputtering. Based on our analysis, Zr-doping improves the optical and mechanical properties simultaneously. Among all ARCs, the sample annealed at 400 C and doped with 1 at.-% Zr presented an excellent anti reflective behavior and the best mechanical performance. These characteristics point towards an improved mechanical resistance (outstanding durability) and optical efficiency thus rendering them excellent candidates for the protection of glass covers on solar panels.