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Nano structure of low crystallinity carbon materials analyzed by using high energy X-ray diffraction

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Oshida K., Nakazawa T., Osawa K., Endo M.
Open Physics
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2009
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vol. 7
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issue 2
232-236
EN
In this study, we tried to characterize a kind of low crystallinity carbon materials. The structure of polyparaphenylene(PPP)-based carbon was analyzed by means of high energy X-ray diffraction using the apparatus of SPring-8. The experimental results revealed the existence of basic structural units (BSU) in the highly disordered materials like PPP-based carbon. It is thought that the PPP-based carbons consist of small turbostratic particles, which have a few piled up poly-aromatic layers. The structure of the PPP-based carbon which seemed to be amorphous was estimated to have hexagonal carbon layers with the size of up to 1 nm. The pores in the PPP-based carbon seem to be clearances formed among the BSUs and amorphous carbon. The pore size of PPP-based carbon was estimated from the result of N2 absorption measurement. The experimental results suggested that the lithium ion charge mechanism in the PPP-based carbon differs from that in graphite.
2
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EPR Study of Dealuminated HY Zeolite and Silica Containing Cu-Mn-Zn Spinels: The Effect of Support

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Decyk P., Więckowski A., Najder-Kozdrowska L., Bilkova I., Ziółek M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
38-44
EN
A mixture of antiferromagnetic Cu_{1.4}Mn_{1.6}O₄ and Cu_{0.5}Zn_{0.5}Mn₂O₄ or/and ZnMn₂O₄ spinels was prepared. Dealuminated HY zeolite and silica were doped by these Cu-Mn-Zn spinels. The materials were investigated by X-ray diffraction, the Fourier transform infrared spectroscopy and EPR spectroscopy. Additionally, all the samples were tested for their activity for isopropyl alcohol dehydration/dehydrogenation. Three EPR signals were observed for Cu-Mn-Zn/dealuminated HY and Cu-Mn-Zn/SiO₂ samples at 293 K. In contrast to the spectra recorded at 293 K, only one broad line attributed to Cu-Mn-Zn spinels was visible at 77 K. The EPR signal from pure Cu-Mn-Zn spinels consists only of a single broad line when recorded at 293 K, whereas at 77 K the line is narrower. For all samples subjected to evacuation at high vacuum up to 573 K, the Cu-Mn-Zn spinels were stable. The evacuation at 673 K resulted in a rapid lowering of the intensity of EPR spectrum.
3
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Controlled Porosity of MCM-41 Obtained by Partial Blocking of Pores by Silicon Oil

100%
Gorgol M., Krasucka P., Goworek J., Zaleski R.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1559-1563
EN
Partial blocking of mesopores in the ordered MCM-41 silica by DC550 silicon oil was proposed as a preparation method of the material with controlled porosity and fixed pore size. The porosity of the samples with various content of DC550 was examined with the use of low temperature nitrogen sorption and positron annihilation lifetime spectroscopy. It was shown that the oil blocks the primary pores by forming the plugs near its entrances, but also partially locates in the interparticle spaces. The comparison of the results obtained from both investigation techniques was used to make the first attempt to obtain the calibration of ortho-positronium intensity, depending on pore volume. This is necessary to improve the utility of positron annihilation lifetime spectroscopy as a porosimetric technique. The need to take the migration of positronium to larger free volume into account is discussed.
4
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Porosity of Silica Monoliths with Tailored Mesopores of Ink-Bottle Shape Determined by Nitrogen Adsorption and Positron Annihilation Lifetime Spectroscopy

100%
Sienkiewicz A., Kierys A., Gorgol M., Zaleski R.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1568-1571
EN
The comparison of pore size distributions obtained with the use of two porosimetric methods: low temperature nitrogen sorption (LN2) and positron annihilation lifetime spectroscopy (PALS), was performed for porous silica monoliths. Four investigated samples were prepared under various synthesis conditions. Nitrogen sorption showed the presence of bottle-shaped pores in all investigated samples. In addition, it seems that the presence of methanol during synthesis influences porosity to a greater extent than organic additives. Quite good agreement between the LN2 and PALS results was observed only for the silica monolith synthesized with β-cyclodextrins as pore directing agent. The biggest discrepancy in the results obtained from these two techniques was observed for the silica gel synthesized with no additives. The origin of such discrepancies, taking into account the shape of pore size distribution and deficiencies of data analysis techniques, is discussed.
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