Células fotoeletroquímicas com estrutura híbrida: síntese e caracterização estrutural e eletroquímica

Anais do VI Encontro de Iniciação Científica e II Encontro Anual de Iniciação ao Desenvolvimento Tecnológico e Inovação – EICTI 2017 - 04 a 06 de outubro de 2017 - temática Ciências Exatas e da TerraAs células solares de Perovskita (CSPs) demonstra um grande potencial para aplicação em dispositivos fotovoltaicos, sendo que a eficiência de conversão de ener- gia desses dispositivos supera, em apenas 5 anos, os 22 % (NREL, 2017). A principal inovação nessa tecnologia, está em um dos componentes de sua estrutura, a camada absorvedora de Perovskita, (p.e., o CH 3 NH 3 PbI 3 ). Há diversas rotas de síntese deste material descritas na literatura, sendo a mais usual é da reação entre o iodeto de metilamônio (CH 3 NH 3 I) e o iodeto de chumbo (PbI 2 ) que, por sua vez, a reação entre ambos para obtenção da fase perovskita não é trivial, em função principalmente de sua instabilidade. No presente trabalho, diferentes rotas de sínteses foram realizadas objetivando chegar em um material com estrutura adequada para aplicação como fo- toânodo nas células solaresUniversidade Federal da Integração Latino-Americana (Unila); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação Araucária; Parque Tecnológico Itaipu (PTI) e Companhia de Saneamento do Paraná (SANEPAR

Síntese de la Perovsquita CH3 NH3 PbI3 pro medio de ruta alternativa para aplicaciones en células solares

Este número da Revista Brasileira de Iniciação Científica publica os artigos com os resultados das pesquisas de Iniciação Científica 2016/17 da Universidade Federal da Integração Latino-Americana (UNILA). A UNILA é uma das novas universidades federais brasileiras, iniciando suas atividades em 2010. Já em 2011, começa a funcionar seu Programa de Iniciação Científica (IC). A IC é uma das prioridades da política de pesquisa da UNILA. Seu aporte em bolsas de IC é superior ao de fontes externas como CNPq e Fundação Araucária. Em seus seis anos de existência, o Programa de IC tem promovido a difusão da cultura científica entre os estudantes, contribuído com sua formação e os estimulado ao ingresso na pós-graduação.No presente trabalho apresentamos uma rota de síntese alternativa, de baixo custo, para produção de pós da perovsquita CH 3 NH 3 PbI 3 e um de seus precursores, o Iodeto de metilamônio (CH 3 NH 3 I). A técnica de Difração de Raios X foi utilizada para caracterização dos materiais sintetizados. Após 34 horas de maceração, foi obtida a fase CH 3 NH 3 PbI 3 , tendo boa estabilidade, por não se degradar durante o armazenamento, sugerindo sua potencial aplicação em células solares.This work reports one alternative route for the production of perovskite powders CH 3 NH 3 PbI 3 and one of its precursors reagents, methylammonium iodide (CH 3 NH 3 I). The X-ray diffraction technique was used to characterize the synthesized materials. After 34 hours of the maceration process, the CH 3 NH 3 PbI 3 phase was obtained, having good stability, as it did not degrade during storage, suggesting its potential application in solar cells.En el presente trabajo presentamos una ruta de síntesis alternativa, de bajo costo, para producción de polvo de la perovsquita CH 3 NH 3 PbI 3 y uno de sus precursores, el Yoduro de metilamonio (CH 3 NH 3 I). La técnica de Difracción de Rayos X fue utilizada para la caracterización de los materiales. Después de 34 horas de maceración, se obtuvo la fase CH 3 NH 3 PbI 3 , con buena estabilidad, sin degradacción durante el almacenamiento, sugiriendo su potencial aplicación en células solares

Air abrasion before and/or after zirconia sintering: surface characterization, flexural strength, and resin cement bond strength

The purpose of this in vitro study was to evaluate the effect of air-abrasion/zirconia sintering order on the yttria partially stabilized tetragonal zirconia polycrystal (Y-TZP) surface characterization (roughness, morphology, and phase transformation), flexural strength (FS), and shear bond strength (SBS) to a resin cement. Y-TZP specimens were air abraded with 50-μm Al2O3 particles after (AS), before (BS), or before and after zirconia sintering (BAS). For roughness (Ra), 30 block specimens (12×12×3.0 mm; n=10) had their surfaces analyzed by a profilometer. Next, on the air-abraded surfaces of these specimens, composite resin discs (n=30) were bonded with RelyX ARC. The bonded specimens were stored for 24 hours in distilled water at 37°C before shear testing. Failure mode was determined with a stereomicroscope (20×). The surface morphology (n=2) was evaluated by SEM (500×). For the four-point flexural strength test (EMIC DL2000), 39 bar-shaped specimens (20×4.0×1.2 mm; n=13) were air abraded according to the three conditions proposed, and an additional group (nonabraded) was evaluated (n=13). The quantitative analysis of phase transformation (n=1) was completed with Rietveld refinement with X-ray diffraction data. Ra (μm) and SBS (MPa) data were analyzed by one-way analysis of variance (ANOVA) and the Tukey test (α=0.05). Pearson correlation analysis was used to determine if there was a correlation between roughness and SBS. For FS (MPa) data, one-way ANOVA and the Dunnett C-test (α=0.05) were used. The air-abrasion/zirconia sintering order influenced significantly (p<0.001) Ra, SBS, and FS. The BS and AS groups presented the highest (1.3 μm) and the lowest (0.7 μm) Ra. The highest SBS (7.0 MPa) was exhibited by the BAS group, followed by the AS group (5.4 MPa) and finally by the BS group (2.6 MPa). All groups presented 100% adhesive failure. A weak correlation (r=−0.45, p<0.05) was found between roughness and SBS. The air-abrasion/zirconia sintering order provided differences in the surface morphology. The nonabraded (926.8 MPa) and BS (816.3 MPa) groups exhibited statistically similar FS values but lower values than the AS (1249.1 MPa) and BAS (1181.4 MPa) groups, with no significant difference between them. The nonabraded, AS, BS, and BAS groups exhibited, respectively, percentages of monoclinic phase of 0.0 wt%, 12.2 wt%, 0.0 wt%, and 8.6 wt%. The rougher surface provided by the air-abrasion before zirconia sintering may have impaired the bonding with the resin cement. The morphological patterns were consistent with the surface roughness. Considering the short-term SBS and FS, the BAS group exhibited the best performance. Air abrasion, regardless of its performance order, provides tetragonal to monoclinic transformation, while sintering tends to zero the monoclinic phase content

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora