Tin dioxide (SnO2) is a promising material with great potential for applications such as gas sensors and catalysts. Nanostructures of this oxide exhibit greater activation efficiency given their larger effective surface. The present study presents results of the synthesis and characterization of tin dioxide under different conditions via oxidation of solid tin with nitric oxide. SnO2powder was characterized primarily by X-ray diffraction and scanning electron microscopy, as well as complementary techniques such as energy-dispersive X-ray spectroscopy, dynamic light scattering and Fourier transform infrared spectroscopy. The results indicated that the established synthesis conditions were suitable for obtaining rutile tin dioxide nanoparticles with a tetragonal crystal structure.
This study aims to assess methane (CH 4) and carbon dioxide (CO 2) concentrations in the ventilation systems of two coal mines (A and B) in the Santa Catarina coal deposit in southern Brazil (Paraná Basin, Bonito Formation), and estimate their greenhouse gas (GHG) emissions. The highest CH 4 levels (1.8%) were recorded in strong methane emanation areas in mine A, below the lower explosive limit (5%). The IPCCrecommended methods significantly overestimated the methane emission (up to 80%) when compared to the experimental data measured for each mine. Application of an alternative method made it possible to estimate direct CO 2 emissions, indicating that CO 2 accounted for 22 to 77% of total GHG emissions. Carbon dioxide emissions are generally not included in GHG emission inventories, indicating that the coal industry underestimates the contribution of this gas. As such, it is recommended that the methodology used for these calculations be revised and that specific emission factors be applied for each mine. In order to improve the accuracy of inventories, more sampling needs to be carried out in all operational and abandoned mines.
The objectives of this study were twofold: to assess two chromatographic methods for the analysis of greenhouse gases (GHG) and carbon monoxide, and to propose and evaluate a low-cost and reusable alternative system for their sampling and storage, using 10 different container configurations (flasks and bags). To that end, standard samples containing the gases of interest (CO 2 , CH 4 and CO) and different types of real samples were tested. Finally, procedures for the sampling, storage and analysis of CO 2 and CH 4 were evaluated and optimized. Two chromatographic methods were applied, using different analysis conditions and columns. Gas chromatography analysis of sample stability and container reusability demonstrated that borosilicate flasks with butyl rubber and PTFE/silicone septa are ideal for storing samples, allowing up to 5 successive sampling cycles with no significant loss of recovery. For larger volume samples, multilayer foil bags are the most stable for the compounds analyzed. The tests conducted with real and synthetic gas samples under optimized chromatography conditions using both methods indicated satisfactory performance for CO 2 and CH 4 quantification. However, CO analysis in the column with a polystyrene-divinylbenzene stationary phase (Method 1) produced an artifact due to the presence of oxygen in the samples, restricting its quantification.
RESUMO -Este trabalho apresenta correlações obtidas entre propriedades mecânicas, densidade e o estado de deterioração de postes de eucalipto novos e retirados de serviço. O estado de deterioração foi determinado por inspeções em campo de postes da rede de distribuição de energia elétrica no sul do Brasil. Postes em diferentes estados de deterioração foram retirados da rede para os ensaios de flexão estática e medidas de densidade. Os testes mecânicos indicaram que os valores médios da resistência a flexão e da rigidez decrescem com o estado de deterioração do eucalipto. Entretanto, verificou-se uma grande variação nessas medidas com diferentes classes de deterioração apresentando resistência mecânica residual similar. Esse comportamento pode ser explicado pela influência da densidade da madeira nas correlações entre propriedades mecânicas e o estado de deterioração dos postes. Madeiras menos densas podem apresentar baixa resistência mecânica residual mesmo sem apresentar sinais de deterioração. O estudo da caracterização da madeira de eucalipto indicou que o estado de deterioração avaliado pela inspeção em campo, por si só não é um bom indicativo para prever a durabilidade das estruturas de madeiras, fazendo-se necessária uma análise preliminar da densidade da mesma.Palavras-chave: Eucalipto, Deterioração e Densidade. RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND DENSITY OF THE EUCALYPTUS WOOD POLES WITH THEIR DETERIORATION STATURS
The species and density of Eucalyptus wood poles installed in the electrical network are useful parameters which must be considered when it is necessary to establish the service life of these structures. In this work, eucalyptus poles samples were collected and analyzed by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS). SEM image analysis showed that the lumen diameter average of fiber substantially is variable between the three species studied, in line with the wood density obtained in laboratory, for poles with several years in service in the electricity network, as well as for not used poles. In addition, EDS microanalysis was utilized for identify the presence of chemical preservatives employed in the conservation these poles. The analysis method proposed proved effective for characterization for this timber.
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