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1
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On Electrostatic Aharonov-Bohm Effect in Solids

100%
Figielski T., Wosiński T., Morawski A., Mąkosa A.
Acta Physica Polonica A
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1998
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vol. 94
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issue 2
305-308
EN
We analyse conditions for an appearance of the electrostatic Aharonov- Bohm interference in two systems: a single-channel quantum-wire loop and an open ballistic quantum dot. We show that in the first system the effect will be destroyed by charge fluctuations, which probably is the reason why it has not been clearly observed, while in the second system the effect is still open for exploration.
2
Content available remote

The Influence of Ex Situ MgB_2 Barrier and HIP on the I_c Anisotropy in Double Core MgB_2/Cu Wires

100%
Gajda D., Morawski A., Zaleski A., Cetner T.
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issue 5
1059-1061
EN
The effect of large I_{c} anisotropy reductions in MgB_2/Cu sheathed wire is presented. The measurements of the critical current in rising magnetic field up to 14 T at 4.2 K were performed. Due to the application of the high isostatic pressure process to the copper sheathed MgB_2 wires with the ex situ MgB_2 homo barrier around the in situ core the anisotropy for such wires was very small and approached to less than 2% at magnetic field over 4 T. The presented geometry and technology show several advantages in their practical applications.
3
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New photocatalyst for decomposition of humic acids in photocatalysis and photo-Fenton processes

100%
Tryba B., Brożek P., Piszcz M., Morawski A.
Polish Journal of Chemical Technology
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2011
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vol. 13
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issue 4
8-14
EN
Humic acid Leonardite IHSS standard was decomposed on TiO2 and TiO2 modified by FeC2O4 via the photocatalysis and photo-Fenton processes under UV irradiation. Humic acid (HA) were favorable adsorbed on TiO2 surface and followed decomposition during UV irradiation faster on TiO2 than on the modified samples. However, when H2O2 was added to the solution, the photo-Fenton process occurred on the prepared TiO2 samples, contained iron together with photocatalysis and high acceleration of HA decomposition was observed. In this case the mineralization degree was much higher than in the applied photocatalysis only, around 75% HA (with concentration of 18 mg/L) was mineralized after 3 h of adsorption and 5 h of UV irradiation in the presence of H2O2 and modified TiO2 whereas on TiO2 mineralisation of HA occurred in around 45% only. The measured fluorescence spectra of HA solutions showed that in the presence of H2O2 polycyclic aromatics were rapidly oxidized to the lower size products such as alcohols, aldehydes, ketones and carboxylic acids, what accelerated the process of HA decomposition.
4
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Effect of Nano-SiC Doping on the Superconducting Critical Parameters in MgB_2/Fe Wires and Tapes

100%
Gajda D., Zaleski A., Morawski A., Kario A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
371-374
EN
In this paper the results of critical current measurements for MgB_2 wires and tapes in iron sheath with and without nano-SiC doping are presented. We focus on power-in-tube processing technique, using both in situ and ex situ methods. In situ MgB_2 wires and tapes were fabricated from MgH_2 and B or Mg and B powders. The methods such as hydrostatic extrusion and rolling were used. The samples were annealed under high Ar gas pressure (hot isostatic pressing) at 750°C and 1.0 GPa for 40 min. It was found that critical current of MgB_2/Fe superconducting wire or tape with nano-SiC dopant increased in higher magnetic field values in comparison to pure MgB_2. A significant difference of J_c in tapes made by in situ way from MgH_2 and Mg were found.
5
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Thermally Stimulated Electron Emission from K-Bi-GICs

100%
Chrzanowski J., Klimkiewicz R., Morawski A.
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EN
The results of the investigations of thermally stimulated electron emission from graphite submitted to intercalation of K-Bi alloy, in the temperature range of 100-400 K, are presented. Total and partial pressure in the measuring chamber in relation to the temperature of the sample are also reported. The insertion of a K-Bi alloy into the interlayers of graphite considerably changes thermally stimulated electron emission properties. The emission images I(T) depend on the content of intercalate and the emission maxima obtained at temperatures of about 170 and 210 K are conditioned by the desorption of a gas while the total pressure above the different samples is of the same order. The desorption of gases at a temperature over 250 K does not cause any increase in the electron emission.
6
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Modification of Commercial Activated Carbons for CO₂ Adsorption

88%
Sreńscek-Nazzal J., Narkiewicz U., Morawski A., Wróbel,A. Gęsikiewicz-Puchalska R., Michalkiewicz B.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
394-401
EN
The aim of the investigations was a modification of DTO, a commercial activated carbon (AC), to improve CO₂ adsorption capacity. The adsorption of CO₂ up to 40 bar at 40°C temperature was investigated. The volumetric method was applied for CO₂ adsorption isotherm measurements. The starting material - DTO - was modified using chemical activation (KOH, ZnCl₂, K₂CO₃). The textural parameters of all the ACs were determined by nitrogen adsorption at the liquid nitrogen temperature of -196°C on Quadrasorb SI. Results showed that the AC modified with KOH had the highest S_{BET}, V_{tot}, V_{mic} values of 2063 m²/g, 1.13 cm³/g, and 0.67 cm³/g, respectively. ACs with a wider pore size distribution (from micropores to mesopores) were obtained. The maximum CO₂ adsorption was equal to 14.44 mmol/g for DTO/KOH - modified carbon whereas 8.07 mmol/g of CO₂ was adsorbed at DTO. The CO₂ adsorption capacities of the ACs were found to be closely correlated with the BET surface areas of the materials tested. The experimental data was fitted to the Freundlich, Langmuir, Sips and Toth equations to determine the model isotherm. The Sips model was found to be the best for fitting the adsorption of CO₂.
7
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Preparation of Activated Carbon from Beet Molasses and TiO₂ as the Adsorption of CO₂

76%
Glonek K., Sreńscek-Nazzal J., Narkiewicz U., Morawski A., Wróbel R., Michalkiewicz B.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1
158-161
EN
The objective of this work is to produce activated carbon from sugar beet molasses containing TiO₂ for CO₂ adsorption and reduction. Textural properties of activated carbons were obtained based on the adsorption-desorption isotherms of nitrogen at 77 K. The specific surface areas of activated carbons were calculated by the Brunauer-Emmett-Teller method. The volumes of micropores were obtained by density functional theory method. The adsorption isotherms of CO₂ were measured up to the pressure of 1 atm at a temperature of 40°C. The best activated carbon adsorbed 1.9 mmol/g of CO₂.
8
Content available remote

Hydrostatic Pressure Effect on Oxygen Precipitates in Silicon Single Crystal

76%
Misiuk A., Adamczewska J., Bąk-Misiuk J., Härtwig J., Morawski A., Witczak Z.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
317-320
EN
The effect of hydrostatic pressure on some properties of Cz-Si with oxygen precipitates is investigated. The observed phenomena are discussed in terms of misfit between the precipitates and Si matrix.
9
Content available remote

Activated Carbons from Molasses as CO₂ Sorbents

76%
Młodzik J., Sreńscek-Nazzal J., Narkiewicz U., Morawski A., Wróbel R., Michalkiewicz B.
Acta Physica Polonica A
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2016
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vol. 129
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issue 3
402-404
EN
Aim of this research is to obtain effective, molasses based activated carbon, which would adsorb big amounts of CO₂. Molasses was mixed with KOH. Weight ratio of dry materials was 1:1 (AC1, AC3) and 1:2 (only AC2). Homogeneous mixture was obtained. Material was left for 3 h at 25°C. Drying lasted for 12 h at 200°C, and the material was grounded. The mixture was pyrolysed at 750°C, under constant flow (18 dm³/min) of nitrogen. The material was grounded again. Then, powder was washed with water, until filtrate was neutral, which took about 5 dm³ of water. AC3 was washed with 1 dm³ of water. After drying, materials were soaked in HCl (0.1 mol/dm³) for 19 h, and washed with water, until filtrate was neutral. CO₂ adsorption was performed under high pressure up to 40 atm, at 40°C. Specific surface area (according to the Brunauer-Emmett-Teller equation) was calculated for AC1, AC2 and AC3 and it is respectively 1985, 1967, and 2026 m²/g, micropore volume - 0.714, 0.707, and 0.728 cm³/g and it was between 75% and 89% of total pore volume. The excess uptake at 40 atm pressure was as follows: AC1 - 14.02 mmol/g, AC2 - 12.75 mmol/g, and AC3 - 15.79 mmol/g.
10
Content available remote

Removal of hazardous pharmaceutical from water by photocatalytic treatment

76%
Choina J., Duwensee H., Flechsig G., Kosslick H., Morawski A., Tuan V., Schulz A.
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EN
The photocatalytic abatement of hazardous pharmaceuticals has been investigated at very low concentration in the ppb range as found in wastewater and in environmental pollutants. Photocatalytic degradation of tetracycline as a model compound with titania catalysts has been studied using solarium UV-A and black light with differentially applied electric power, tetracycline and catalyst concentration. Abatement of up to 90% has been achieved after 1 hour. Adsorption of tetracycline and photochemical degradation contribute significantly to the abatement of tetracycline resulting in an immediate reduction during the initial period of treatment. Contribution of adsorption is high at very low concentration (500 ppb). Photocatalytic treatment with titania is even highly efficient in the abatement of very small concentrations of tetracycline in drinking water.
11
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Content available

Magnetotransport through Nanoconstriction in Ferromagnetic Semiconductor (Ga,Mn)As

64%
Figielski T., Wosiński T., Pelya O., Sadowski J., Morawski A., Mąkosa A., Dobrowolski W., Jagielski J., Wróbel J.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
525-531
EN
We studied narrow (submicron) constrictions in the layers of ferromagnetic semiconductor (Ga,Mn)As. We have demonstrated a contribution of the quantum localization effects to the magnetoresistance of the constricted samples. We have also found a negative contribution of a domain wall trapped in the constriction to the resistance, due presumably to the erasing of the localization effects by the domain wall.
12
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Content available

Superconducting and Microstructural Properties of (Mg+2B)+MgB_2/Cu Wires Obtained by High Gas Pressure Technology

64%
Kario A., Morawski A., Głowacki B., Łada T., Smaga M., Diduszko R., Kolesnikov D., Zaleski A., Kondrat A., Gajda D.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
693-703
EN
In order to improve the overall critical current characteristics of Cu sheathed in situ MgB_2 wires a special architecture of the wire, and processing parameters were used. The study presents the influence of the ex situ MgB_2 chemical barrier between ex situ core and Cu, suppressing the reaction of Cu with Mg. Wires, doped with 10 at.% SiC of 18 nm average grain size, were fabricated from MgH_2 and B or from Mg and B powders, using the powder-in-tube method. The methods of rotary swaging or drawing were used as the alternating wire-forming processes. The samples were annealed under high Ar gas pressure (hot isostatic pressing) at 750ºC and 1.0 GPa for 15 and 30 min. A significant difference in Cu distribution across the wires for a long and short time of sintering was observed. The formation of microstructure in the powder-in-tube process and the relationship between the microstructure and critical current density J_c values, are discussed in this paper.
13
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Content available

Vertical Electron Transport through PbS-EuS Structures

52%
Wrotek S., Dybko K., Morawski A., Mąkosa A., Wosiński T., Figielski T., Tkaczyk Z., Łusakowska E., Story T., Sipatov A., Szczerbakow A., Grasza K., Wróbel J., Palosz W.
Acta Physica Polonica A
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2003
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vol. 103
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issue 6
629-635
EN
Temperature dependence of current-voltage I-V characteristics and resistivity is studied in ferromagnetic PbS-EuS semiconductor tunnel structures grown on n-PbS (100) substrates. For the structures with a single (2-4 nm thick) ferromagnetic EuS electron barrier we observe strongly non-linear I-V characteristics with an effective tunneling barrier height of 0.3-0.7 eV. The experimentally observed non-monotonic temperature dependence of the (normal to the plane of the structure) electrical resistance of these structures is discussed in terms of the electron tunneling mechanism taking into account the temperature dependent shift of the band offsets at the EuS-PbS heterointerface as well as the exchange splitting of the electronic states at the bottom of the conduction band of EuS.
14
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Fabrication and Electrical Characterization of PbS-EuS Ferromagnetic Semiconductor Microstructures

52%
Wrotek S., Morawski A., Tkaczyk Z., Mąkosa A., Wosiński T., Dybko K., Łusakowska E., Story T., Sipatov A., Péecz B., Grasza K., Szczerbakow A., Wróbel J.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
615-620
EN
Current-voltage characteristics and temperature dependence of differential conductance were studied in lithographically patterned (lateral dimensions from 10 x 10 μm^2 to 100 x 100 μm^2) ferromagnetic EuS-PbS-EuS microstructures. Below the ferromagnetic transition temperature a 4% decrease in the structure conductance was observed for mutual antiferromagnetic orientation of magnetization vectors of ferromagnetic EuS layers.
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