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Sari Lehto Lauri Niinistö Inkeri Yliruokanen 《Fresenius' Journal of Analytical Chemistry》1993,346(6-9):608-611
Summary For the analysis of electroluminescent thin films, X-ray fluorescence (XRF) provides a convenient method as both the concentration of the dopant and the film thickness can be determined rapidly and non-destructively. An XRF method for the determination of thickness and lead concentration in lead doped calcium sulfide thin films was developed. Calibration standards made of polyvinyl alcohol and gelatin as well as filter paper standards were used. In addition, the applicability of a fundamental parameter program UniQuant was investigated. For comparison, the concentrations of lead and calcium were determined after dissolution by atomic absorption spectrometry. Generally, the correlation between the different methods excluding the use of filter paper standards was satisfactory. When the dopant concentration was very low or very high, however, the fundamental parameter program yielded best results. Determination of thicknesses by XRF was made by comparing the sulfur K
intensities of the sample and those of a zinc sulfide standard. A correction factor for molar masses and densities was applied. The thicknesses obtained were compared to those measured with a profilometer after etching and the deviations were found to be less than 10%.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday 相似文献
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Paavo A. Penttilä Anikó Várnai Manuel Fernández Inkeri Kontro Ville Liljeström Peter Lindner Matti Siika-aho Liisa Viikari Ritva Serimaa 《Cellulose (London, England)》2013,20(3):1031-1040
The hydrolysis of nanofibrillated cellulose (NFC), consisting of individual cellulose fibrils, was followed using small-angle scattering techniques in order to reveal changes in the substrate structure caused by cellulose degrading enzymes. In particular, the nanoscale structure of the network of cellulose fibrils was characterized with the combination of small-angle neutron scattering and small-angle x-ray scattering. In the nanocellulose with higher xylan content, the interfibrillar distance was shown to remain unchanged during enzymatic degradation, whereas the distance increased in the nanocellulose with lower xylan content. The limiting effect of xylan on the hydrolysis and a faster hydrolysis of the more thoroughly fibrillated segments of the NFC network could be observed. Despite the extensive fibrillation of the raw material, however, the hydrolysis was eventually limited by the aggregated and heterogeneous structure of the substrate. 相似文献
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The cerium content and the film thickness of cerium-activated alkaline earth metal sulfide films were determined simultaneously. The cerium determination was calibrated by using standard solutions on filter paper. Film thickness was determined by comparing the S Kα intensities with those in zinc sulfide standards. The detection limit for cerium was estimated to be 0.1 μg cm?2. 相似文献
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Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger (\(n=16\)) and more varied collection of samples than previous studies have presented is used. In particular, samples (\(n=6\)) with low crystallinity and small crystallite sizes are included. A good linear correlation (\(r^{2} \ge 0.90\)) between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity. 相似文献
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Tiina Harju Timo Laitinen M. Pärkkä Hannu Revitzer Inkeri Yliruokanen 《Analytical and bioanalytical chemistry》1997,357(7):801-805
Diffusion-controlled sampling techniques, i.e. diffusion screens and diffusion tubes (= denuders), can be used in the collection
of several vaporized heavy metal species in clean gases (pure N2 atmosphere) at elevated temperatures. Collection efficiencies obtained for Hg, HgCl2, Cd, CdCl2 and ZnCl2 were over 90% using adsorption on Au-coated diffusion screens and Ag-coated denuders. However, the collection efficiencies
for Zn and PbCl2 were significantly lower. In field measurements performed at a hazardous waste incineration plant and in a power plant equipped
with a circulating fluidized-bed boiler, collection efficiencies seemed to vary noticeably depending on the sampling conditions
and metal species to be sampled. Best collection efficiencies were obtained for mercury with both Ag coated denuders and Au
coated screens whereas cadmium showed significantly poorer results in field measurements than in the laboratory. Sampling
of zinc and lead species seemed to be problematic in all cases. Of the two sampling techniques, the denuder technique is more
recommendable than the screen technique for sampling in relatively clean gases. However, neither of these techniques should
be used in flue gases without further understanding of the collection mechanisms.
Received: 6 November 1996 / Revised: 3 July 1996 / Accepted: 14 July 1996 相似文献
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