Neste trabalho foram desenvolvidas amostras de materiais padrão de referência para difratometria de policristais. Materiais de alta pureza foram tratados mecânica e termicamente até atingirem as características necessárias para serem usados como materiais padrão de referência de alta qualidade, comparáveis àqueles produzidos pelo NIST. As medidas foram feitas inicialmente em vários difratômetros convencionais de laboratório de difração de raios X, com geometria de Bragg -Brentano, difratômetros de nêutrons e, posteriormente, em equipamento de alta resolução com fonte síncrotron. Os parâmetros de rede obtidos foram calculados pelo programa Origin e ajustados pelo Método dos Mínimos Quadrados. Esses ajustes foram comparados com os obtidos pelo Método de Rietveld, usando o programa GSAS através da interface gráfica EXPGUI, mostrando-se bastante satisfatórios. Os materiais obtidos foram alumina-α, ítria, silício, céria, hexaboreto de lantânio e fluoreto de lítio, que apresentaram qualidade semelhante e, em alguns casos, superiores aos padrões desenvolvidos e comercializados pelo NIST, a custos bem menores. / In this work, samples of standard reference materials for diffractometry of polycrystals were developed. High-purity materials were submitted to mechanical and thermal treatments in order to present the adequate properties to be used as high-quality standard reference materials for powder diffraction, comparable to the internationally recognized produced by the USA National Institute of Standards and Technology NIST, but at lower costs. The characterization of the standard materials was performed by measurements in conventional X-ray diffraction diffractometers, high resolution neutron diffraction and high-resolution synchrotron diffraction. The lattice parameters were calculated by extrapolation of the values obtained from each X-ray reflection against cos2θ by the Least-Squares Method. The adjustments were compared to the values obtained by the Rietveld Method, using the program GSAS. The materials thus obtained were the α-alumina, yttrium oxide, silicon, cerium oxide, lanthanum hexaboride and lithium fluoride. The standard reference materials produced present quality similar or, in some cases, superior to the standard reference materials produced and commercialized by the NIST.

Neste trabalho foram desenvolvidas amostras de materiais padrão de referência para difratometria de policristais. Materiais de alta pureza foram tratados mecânica e termicamente até atingirem as características necessárias para serem usados como materiais padrão de referência de alta qualidade, comparáveis àqueles produzidos pelo NIST. As medidas foram feitas inicialmente em vários difratômetros convencionais de laboratório de difração de raios X, com geometria de Bragg -Brentano, difratômetros de nêutrons e, posteriormente, em equipamento de alta resolução com fonte síncrotron. Os parâmetros de rede obtidos foram calculados pelo programa Origin e ajustados pelo Método dos Mínimos Quadrados. Esses ajustes foram comparados com os obtidos pelo Método de Rietveld, usando o programa GSAS através da interface gráfica EXPGUI, mostrando-se bastante satisfatórios. Os materiais obtidos foram alumina-α, ítria, silício, céria, hexaboreto de lantânio e fluoreto de lítio, que apresentaram qualidade semelhante e, em alguns casos, superiores aos padrões desenvolvidos e comercializados pelo NIST, a custos bem menores. / In this work, samples of standard reference materials for diffractometry of polycrystals were developed. High-purity materials were submitted to mechanical and thermal treatments in order to present the adequate properties to be used as high-quality standard reference materials for powder diffraction, comparable to the internationally recognized produced by the USA National Institute of Standards and Technology NIST, but at lower costs. The characterization of the standard materials was performed by measurements in conventional X-ray diffraction diffractometers, high resolution neutron diffraction and high-resolution synchrotron diffraction. The lattice parameters were calculated by extrapolation of the values obtained from each X-ray reflection against cos2θ by the Least-Squares Method. The adjustments were compared to the values obtained by the Rietveld Method, using the program GSAS. The materials thus obtained were the α-alumina, yttrium oxide, silicon, cerium oxide, lanthanum hexaboride and lithium fluoride. The standard reference materials produced present quality similar or, in some cases, superior to the standard reference materials produced and commercialized by the NIST.

Firefighters and asphalt pavers are exposed to polycyclic aromatic hydrocarbons (PAHs) during various work activities. The purpose of this study was to evaluate urinary PAH levels and compare these bio-monitoring levels among firefighters, asphalt pavers, and non-occupationally exposed individuals. The National Institute of Standards and Technology (NIST) urinary PAH levels were used for non-occupationally exposed controls. When compared to the NIST standard for smokers and non-smokers, firefighters demonstrated statistically significant differences in urinary concentration differences for the following metabolites: 2-OH-fluorene, 3-OH-fluorene and 1-OH-pyrene, which were lower in firefighters than the NIST mean for smokers. 1-OH-phenanthrene, 2-OH-phenanthrene and 3-OH-phenanthrene were higher among world trade center exposed firefighters than the NIST mean for smokers. When firefighters were compared to the NIST non-smoker standard, firefighters demonstrated elevated levels in all tested PAH biomarkers due to a mixture of smokers and non-smokers in the firefighter cohort. Asphalt workers had statistically significant higher urinary concentration elevations in 2-OH-fluorene, 1-OH-phenanthrene and 3-OH-phenanthrene as compared to the NIST smoker mean. When asphalt pavers were compared to the NIST non-smoker mean, asphalt pavers had statistically significant increases in all tested PAH biomarkers, with the exception of 2-OH-phenanthrene. While firefighters did not demonstrate a substantial change in urinary PAH metabolite levels compared to control populations of smokers and non-smokers, asphalt pavers experienced concentrations that were in some cases increased by orders of magnitude compared to NIST controls. Future research may be needed to evaluate any potential health risk posted to occupational exposed asphalt pavers.