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Determination of Radiation Shielding of Concrete Produced from Portland Cement with Boron Additives

100%
Davraz M., Pehlıvanoğlu H., Kilinçarslan Ş., Akkurt İ.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 3
702-704
EN
Concrete is a material which is widely used for neutron shielding in such building constructions as nuclear power stations, particle accelerators and medical hospitals. Concrete is very significant for neutron shielding, because is contains some elements which help to moderate very penetrative fast neutrons. Boron increases the neutron shielding effectiveness of concretes. Boron can be added to concrete in different ways, by addition of boron to the water, used in concrete, or by addition of boron containing natural minerals. In this study, three samples of concrete were produced using B₂O₃ additives material, boron-modified active belite and Portland cement. Neutron absorption coefficients of the produced three different types of concrete samples were obtained through experiments. It is concluded that the addition of boron to concrete is an alternative option to be used for the purposes of neutron shielding.
2
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Influence of High Temperature on Concrete Produced from Portland Cement with Boron Additives

100%
Davraz M., Pehlıvanoğlu H., Kilinçarslan Ş.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 3
872-874
EN
The boron compounds have been widely used as additives in the production of cement and concrete to enhance their engineering properties. In this study, three series of concrete specimens were produced using B₂O₃ additive materials, boron modified active belite cement and Portland cement. After 28 days of curing period the specimens were exposed to temperatures of 250, 500 and 750°C. Mass loss and compressive strength were determined and recorded after the specimens were cooled to room temperature. It was concluded that the effect of the boron becomes more apparent at high temperatures.
3
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Preparation, Characterization and Catalytic Properties of SBA-15-SO₃H Supported Tungstophosphoric Acid for Esterification Reaction

81%
Erdem B., Erdem S., Çıtak A., Yavru C., Öksüzoğlu R.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 3
1041-1044
EN
SBA-15-SO₃H supported tungstophosphoric acid (TPA, H₃PW₁₂O₄₀) mesoporous materials were synthesized by impregnation of TPA into the hydrothermally synthesized SBA-15-SO₃H and the catalytic performances were compared for the esterification reaction. The physical and chemical properties of the catalysts were characterized by XRD, SEM/EDX, FT-IR and N₂ adsorption/desorption techniques. The characterization results show that TPA/SBA-15-SO₃H retained the typical mesoporous structure of SBA-15-SO₃H. The experimental results indicated that TPA/SBA-15-SO₃H is a more efficient catalyst than SBA-15-SO₃H for the esterification reaction. The higher activity of TPA/SBA-15-SO₃H compared with that of SBA-15-SO₃H was consistent with the material having the low pKa value, confirming that the esterification rate was mostly dependent on the acid strength of the additional functional groups of solid acid catalyst. Accordingly, the reason for the catalytic activity difference was simply explicated by the effect of TPA, having low pKa value, affecting the pore structure and the total acidity.
4
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Nanoporosity of Polymer Sorbents and Membrane Materials as Seen by PALS and Low Temperature Gas Sorption

81%
Shantarovich V., Bekeshev V., Kevdina I., Yampolskii Y., Bermeshev M., Belov N.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1548-1551
EN
The limits of application of positron annihilation lifetime spectroscopy and low temperature gas sorption for studying nanoporosity of polymer sorbents and membrane materials are discussed relying on the results previously obtained by the authors. For the two methods, limitations are determined by different factors: the dispersion of the material is essential for low temperature gas sorption, while concentration of nanopores of given size is important for positron annihilation lifetime spectroscopy. The both methods came out to be a useful addition to each other in the studies of micropores and mesopores.
5
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Structural Alterations in Smithsonite during High-Energy Ball Milling

61%
Tunç Parlak T., Yilmaz V., Yildiz K.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 3
723-724
EN
Smithsonite, ZnCO₃, from Zamantı-Kayseri, Turkey, was subjected to high-energy milling. X-ray diffraction analysis was performed to study amorphisation in the structure and the alterations of bands in the structure were investigated by Fourier transform infrared spectroscopy. Characterization of milled smithsonite by X-ray diffraction analysis has shown that disappearance, decrease and/or shifting of the patterns occurred with mechanical activation, which means that amorphisation was taking place. Amorphisation was also demonstrated by Fourier transform infrared spectroscopy analysis, where shifting of band centers was observed.
6
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Aerogel IC3120 Under High Pressure Exerted Mechanically and by Nitrogen

52%
Gorgol M., Zgardzińska B.
Acta Physica Polonica A
|
2017
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vol. 132
|
issue 5
1531-1534
EN
Highly porous IC3120 silica aerogel was subjected to the high pressure up to 450 MPa while the positron annihilation lifetime spectra were collected. The pressure was delivered to the investigated samples in two ways: by pistons and by gas (nitrogen) penetrating the aerogel. The evolution of all PALS parameters was discussed. With the increase of the pressure, shortening of ortho-positronium lifetimes (different, depending on the pressure method introduced) was observed. Similarity between the dependence of the longest-lived o-Ps component lifetime on the pressure, for the sample affected with nitrogen molecules and pure nitrogen was observed. It suggests, that the nitrogen fills the largest free volumes of the aerogel. The pressure exerted mechanically causes much smaller decrease of free volume available for positronium. The comparison of PALS results with the electron microscopy images, obtained after removing the pressure, confirmed that more intense and lasting changes were caused by affecting the aerogel with the pistons.
7
Content available remote

Controlled Porosity of MCM-41 Obtained by Partial Blocking of Pores by Silicon Oil

52%
Gorgol M., Krasucka P., Goworek J., Zaleski R.
Acta Physica Polonica A
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2017
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vol. 132
|
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.
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