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1
Content available remote

Effect of Heat Treatment on the Phase Transformation and Magnetic Properties of the Rapidly Solidified Pr₉Fe₅₈Co₁₃Zr₁Nb₄B₁₅ Alloy Ribbons

100%
Pawlik K.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 5
1264-1269
EN
The rapidly solidified ribbon samples of the Pr₉Fe₅₈Co₁₃Zr₁Nb₄B₁₅ alloy subjected to short time annealing at temperatures ranging from 923 K to 1033 K were investigated. The phase analysis supported by the Rietveld refinement was used to identify the phase constitution. The results of Rietveld calculations were confirmed by transimission electron microscopy and M(T) studies. Measurement of recoil curves allowed the determination of switching field distributions and δ M plots for samples annealed at various temperatures.
2
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Effect of Annealing Temperature on the Magnetic Properties of Pr-Fe-Co-Zr-Nb-B Alloys Ribbons

100%
Pawlik K.
Acta Physica Polonica A
|
2018
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vol. 133
|
issue 3
657-659
EN
The properties of rapidly solidified ribbons of Pr₉Fe_{50+x}Co₁₃Zr₁Nb₄B_{23-x} (where x=2, 5, 8) alloys annealed at temperatures ranging from 923 K to 1033 K were investigated. The heat treatment of the fully amorphous as-cast ribbons led to the simultaneous crystallization of the hard magnetic Pr₂(Fe,Co)₁₄B, the soft magnetic α-Fe and the paramagnetic Pr_{1+x}Fe₄B₄ phases. However, the crystallization of the α-Fe phase took place as the second crystallization event at higher temperatures for the x=8 alloy. The Rietveld analysis of the X-ray diffraction patterns was used to calculate the crystallite sizes of constituent phases. Additionally, using PONKCS method the weight fractions of crystalline and amorphous components were quantified. For all alloy compositions the temperature dependencies of magnetic parameters were determined from the hysteresis loops.
3

From DNA sequence to antibiotic

64%
Pawlik K., Kotowska M.
Biotechnologia
|
2005
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issue 3
57-74
EN
Progress in molecular biology, large number of known bacterial sequences and a number of microbiological genome sequencing projects finished or running allow to think about creating in vitro the DNA code in order to obtain new metabolites. Here, we describe the attempts of biosynthesis of new polyketides by designing new genes coding polyketide synthases. In assembling new polyketide synthases, the fragments of known genes are widely used. High homology of the polyketide synthase genes and a number of known produced polyketides give a possibility to describe a polyketide synthase on a DNA sequence level. Basing on known amino acid motifs, it is possible to determine enzymatic activities acting in the process of polyketide synthesis, and so to predict putative structure of the final metabolite. Successful artificial synthesis of 6-deoxyerythronolide B synthase genes show how near is the realization of the idea of producing new chemical compounds by creating DNA information.
4

Bacterial small signaling molecules

64%
Pawlik K., Kuczek K.
Biotechnologia
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2002
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issue 4
115-120
EN
Many bacterial species use small chemical molecules as signaling factors. Signal molecules are released into the environment and once a threshold concentration level has been achieved, they trigger a response in the target cells. This system of cell-cell signaling, termed as ?quorum sensing?, plays an important role in the coordination of the growth and other processes in bacterial populations. Two types of signaling molecules have been identified: (1) short peptides, common to Gram-positive bacteria and (2) carboxy-acid derivatives commonly utilised by Gram-negative bacteria. Bacteria of the genus Streptomyces utilize butyrolactones as signaling molecules and thus form a distinct group among Gram-positives. This review focuses on two model regulatory systems based on carboxy-acid derivatives: the regulation of bioluminescence in Vibrio fisheri and the regulation of streptomycin biosynthesis in Streptomyces griseus.
5
Content available remote

Magnetization Reversal Processes in Pr-Fe-B-type Nanocrystalline Magnets

51%
Pawlik K., Pawlik P., Kaszuwara W., Wysłocki J.
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vol. 126
|
issue 1
186-187
EN
The magnetization reversal processes in magnets derived from rapidly solidified Pr_{9}Fe_{52}Co_{13}Zr_{1}Nb_{4}B_{21} alloy samples were studied by analysis of minor hysteresis loops and recoil curves. The studies were carried out on suction-cast 1 mm diameter rod, 1 mm thick plate, 3 mm outer diameter (o.d.) tube and melt-spun ribbon samples subjected to annealing at 983 K for 5 min. The X-ray diffraction analysis has shown multiphase constitution of the samples. Structural and magnetic studies indicated that the initial state of microstructure and phase composition affects the magnetization reversal processes in annealed samples due to a variation of microstructure in samples of various shapes. Magnetic studies allowed estimation of the mean values of nucleation and pinning fields that control the magnetization reversal processes.
6
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Glass Forming Abilities and Crystallization Process in Amorphous Pr-Fe-Co-Zr-Nb-B Alloys of Various B Content

51%
Pawlik K., Pawlik P., Kaszuwara W., Wysłocki J.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 4
979-981
EN
The influence of boron contents on the glass forming abilities and magnetic properties of melt-spun ribbon samples produced from Pr₉Fe_{50+x}Co₁₃Zr₁Nb₄B_{23-x} (x=0, 2, 5, 8) alloys, were investigated. For all compositions, the rapidly solidified samples were fully amorphous, which was confirmed by X-ray diffractometry and the Mössbauer spectroscopy. Differential scanning calorimetry and differential thermal analysis studies revealed good glass forming abilities for all investigated specimens and allowed to determine thermal stability parameters of the amorphous phase. For all alloy ribbons, very large supercooled liquid region before crystallization ΔT_x reaching 100 K was measured. The Kissinger plots were constructed to determine the activation energies for crystallization. Annealing of specimens at temperatures ranging from 923 K to 1033 K for 5 min resulted in significant change of the phase constitution. The X-ray diffractometry studies have shown presence of hard magnetic Pr₂(Fe,Co)₁₄B and paramagnetic Pr_{1+x}Fe₄B₄ phases. Furthermore, with the increase of B contents in the alloy composition crystallization of α-Fe phase occurs at wider range of the annealing temperature. Anomaly of both thermal and magnetic properties was observed for the Pr₉Fe₅₂Co₁₃Zr₁Nb₄B₂₁ alloy ribbons.
7
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The Bulk Glass Forming Ability and Magnetic Properties of Pr_9Fe_{50 + x}Co_{13}Zr_1Nb_4B_{23 - x} (x = 0, 2, 5, 8) Alloys

51%
Pawlik K., Pawlik P., Wysłocki J.
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|
issue 5
900-902
EN
In the present study the rapidly quenched Pr_9Fe_{50 + x}Co_{13}Zr_1Nb_4B_{23 - x} (x = 0, 2, 5, 8) alloy samples produced in a form of 100 mm^2 plate of various thicknesses were investigated. The X-ray diffraction revealed changes in the phase constitution of as-cast samples depending on the alloy composition and plate thickness. The presence of hard magnetic Pr_2(Fe,Co)_{14}B phase was observed in 0.5 mm thick plates of the x = 8 alloy, while fully glassy structure was shown in 0.5 mm thick plates of the x = 0 alloy. It was shown in the present paper that magnetic properties of annealed samples originated from different microstructure of as-cast samples.
8
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Magnetization Reversal Processes in the Nanocrystalline Fe-Co-Zr-Ti-Pr-B Magnets

51%
Pawlik K., Pawlik P., Wysłocki J., Kaszuwara W.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
39-42
EN
Magnetization reversal processes in the magnets derived from the Fe_{60}Co_{13}Zr_1Ti_3Pr_9B_{14} alloy were investigated. It was shown that the processing technique affects the magnetization reversal processes. For the nanocrystalline ribbon samples pinning of the domain walls arises at low external magnetic fields while nucleation of reversed domains occurs at higher fields. However, the nucleation fields are lower than the pinning fields for the nanocrystalline rod and tube samples produced by suction-casting technique.
9
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Phase Structure and Heat Generation in the Co-Precipitated Magnetite Nanoparticles

51%
Pawlik P., Pruba M., Pawlik K., Kotynia K.
Acta Physica Polonica A
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2017
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vol. 131
|
issue 5
1217-1221
EN
In the present studies the phase structure and magnetic ordering of magnetite nanoparticles were investigated. The powder samples were obtained by co-precipitation from Fe(III) and Fe(II) salts. SiO₂ coating was performed using the modified Stöber process. X-ray diffraction studies revealed presence of the only one Fe₃O₄ crystalline phase both for the non-coated and SiO₂-coated samples. The Mössbauer studies have shown differences in shapes of measured spectral lines for Fe₃O₄ particles subjected to the Stöber process and non-coated particles. The heating efficiency was measured for glycerol dispersed nanoparticles. The analysis have shown changes in specific loss power depending on the concentration of the nanoparticles and amplitude of alternating magnetic field.
10
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Influence of Nb Addition on Magnetic Properties of the Nanocrystalline (Nd₁₀Fe₆₇B₂₃)_{100-x}Nbₓ (where x = 1, 2, 4) Alloy Ribbons

45%
Szwaja M., Pawlik K., Pawlik P., Gębara P., Michalski B.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 2
623-625
EN
In the present work the magnetic properties and phase constitution of (Nd₁₀Fe₆₇B₂₃)_{100-x}Nbₓ (where x = 1, 2, 4) alloys in the form of ribbons were investigated. The base alloys were prepared by arc-melting the high purity elements with pre-alloyed Fe-B under an Ar atmosphere. The ribbon samples were obtained by controlled atmosphere melt-spinning technique. In order to generate the nanocrystalline microstructure and hard magnetic properties, samples were annealed at various temperatures (from 923 K to 1023 K) for 5 min. The aim of the present work was to determine the influence of Nb admixture and annealing conditions on the phase constitution and magnetic properties.
11
Content available remote

Magnetization Reversal Processes in Nanocrystalline (Pr, Dy)-(Fe, Co)-B Bulk Alloys

45%
Przybył A., Pawlik K., Pawlik P., Gębara P., Wysłocki J.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 2
579-581
EN
The aim of this paper was to study the phase constitution, magnetic properties and magnetization reversal processes in the rapidly solidified bulk (Pr,Dy)-(Fe,Co)-B alloys doped with Zr, Ti, Mn and Ni. The 3 mm outer diameter tubes samples of the Pr₈Dy₁Fe₆₀Co₇Ni_{(6x)}MnₓB₁₄Zr₁Ti₃ (where x = 0, 3, 6) alloys were produced by suction-casting technique. The admixture of Zr was introduced in order to improve their glass forming abilities while Dy was substituted to enhance the magnetocrystalline anisotropy of hard magnetic phase. The effect of Ni and Mn addition on the phase constitution and magnetic properties was studied in the presented work.
12
Content available remote

Structural and Magnetic Studies of the Fe-Co-Zr-Mo-W-B Amorphous Alloy

45%
Kotynia K., Pawlik P., Hasiak M., Pruba M., Pawlik K.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 5
1204-1206
EN
The paper presents a characterization of the phase structure by X-ray diffraction and isothermal magnetic entropy changes for the amorphous Fe₅₈Co₁₀Zr₁₀Mo₅W₂B₁₅ alloy sample in the as-quenched state. An ingot sample was obtained by arc-melting. The ribbon sample was obtained by the melt-spinning technique. The magnetic measurements at various temperatures allowed for the study of the Curie temperature T_{C} and magnetic entropy changes |ΔS_{M}|. In order to determine the Curie temperature T_{C} of amorphous phase, three independent methods were used. Determination of the Curie temperature T_{C} for the amorphous alloys is not a trivial problem, as magnetization does not decreases rapidly around T_{C}. Therefore it is essential issue to establish T_{C} using few complementary methods. X-ray diffraction analysis revealed a fully amorphous structure of the ribbon samples.
13
Content available remote

Investigations of the Magnetization Reversal Processes in Nanocrystalline Nd-Fe-B Alloys Doped by Nb

39%
Kaźmierczak M., Pawlik P., Wysłocki J., Wnuk I., Gębara P., Pawlik K., Przybył A.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
789-791
EN
In the following article the magnetic properties and phase composition of (Nd₁₀Fe₆₇B₂₃)_{100-x}Nb_{x} (where x=5, 6, 7, 8, 9) alloys in the form of ribbons are discussed. The X-ray diffraction studies revealed the coexistence of amorphous and nanocrystalline structures consisting of Nd₂Fe₁₄B, Nd_{1+ε}Fe₄B₄ and metastable Nd₂Fe₂₃B₃ phases. The shape of M_{rev} (M_{irr}) suggests that the magnetization reversal proceeds through the nucleation of the reversal domain for the ribbon doped with 5-7 at.% of Nb and the subsequent pinning of the domain walls for ribbons doped with 8 and 9 at.% of Nb.
14
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Phase Composition and Magnetic Properties of the Nanocrystalline Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} Alloy

39%
Filipecka K., Pawlik K., Pawlik P., Wysłocki J., Gębara P., Przybył A.
|
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vol. 126
|
issue 1
164-165
EN
The aim of the present work was to study the influence of annealing conditions on magnetic properties and the phase constitution of rapidly solidified Fe_{64.32}Pr_{9.6}B_{22.08}W_{4} alloy ribbons. The base alloy was prepared by arc-melting of the high purity elements under an Ar atmosphere. Subsequently the ribbon samples were obtained by melt-spinning technique under low pressure of Ar. In order to develop nanocrystalline structure, the samples were annealed at 1003 K for 5, 10, 20 and 30 min. The room temperature magnetic properties were determined from hysteresis loops measured by VSM magnetometry in the external magnetic field up to 2 T. For comparison the influence of annealing temperature on magnetic properties was studied for the same alloy composition. The ribbons were annealed at temperatures from 929 K to 1023 K for 5 min. X-ray diffractometry was used to determine the phase composition of annealed ribbons. Heat treatment resulted in an evolution of the phase constitution, that caused changes in magnetic properties of the alloy.
15
Content available remote

Magnetic Properties and Phase Constitution of the Nanocrystalline (Nd_{10}Fe_{67}B_{23})_{100-x}Nb_{x} (where x=1, 2, 3, 4) Alloy Ribbons

39%
Kaźmierczak M., Pawlik K., Pawlik P., Gębara P., Przybył A., Wysłocki J.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 1
91-93
EN
In the present work the magnetic properties and phase constitution of (Nd_{10}Fe_{67}B_{23})_{100-x}Nb_{x} (where x=1, 2, 3, 4) alloys in a form of ribbons were investigated. The ribbon samples were obtained by controlled atmosphere melt-spinning technique. In order to generate the nanocrystalline microstructure, ribbons were annealed at various temperatures (from 923 K to 1023 K) for 5 min. Subsequent annealing resulted in an evolution of the phase constitution accompanied by a change of their magnetic properties. The X-ray diffraction studies show presence of hard magnetic Nd_{2}Fe_{14}B, paramagnetic Nd_{1+ε }Fe_{4}B_{4} and ferromagnetic metastable Nd_{2}Fe_{23}B_{3} phases. The best hard magnetic parameters were measure for annealed ribbons of the (Nd_{10}Fe_{67}B_{23})_{96}Nb_{4} alloy.
16
Content available remote

Effect of Tungsten Addition on Phase Constitution and Magnetic Properties of the Bulk Fe_{65}Pr_{9}B_{26-x}W_x Alloys

39%
Filipecka K., Pawlik P., Pawlik K., Gębara P., Przybył A., Pruba M.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 1
104-106
EN
The effect of tungsten addition on phase constitution and magnetic properties of the bulk Fe_{65}Pr_9B_{26-x}W_{x} (where x=2, 4, 6, 8) alloys was studied. The base alloys were prepared by arc-melting of the high purity elements under Ar atmosphere. Samples were produced by suction of an arc-molten alloy to a water-cooled copper mould (the suction-casting method). In order to develop nanocrystalline structure, the samples were subjected to annealing. Heat treatment resulted in an evolution of the phase constitution that caused changes in magnetic properties of the alloys. X-ray diffractometry was used to determine the phase composition of annealed samples. The analysis showed presence of hard magnetic Pr_2Fe_{14}B, paramagnetic Pr_{1+x}Fe_4B_4 and soft ferromagnetic α-Fe phases of annealed samples. The room temperature magnetic properties were determined from hysteresis loops measured by VSM magnetometer in the external magnetic field up to 2 T. The highest hard magnetic parameters were measured for the rod sample of Fe_{65}Pr_9B_{20}W_6 annealed at 1003 K for 5 min.
17
Content available remote

The Effect of Annealing Temperature on the Phase Constitution and Magnetic Properties of the Pr₈Dy₁Fe₆₀Co₇Mn₆B₁₄Zr₁Ti₃ Alloy Ribbons

39%
Przybył A., Pawlik K., Pawlik P., Gębara P., Kaszuwara W., Wysłocki J., Filipecka K.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 1
94-97
EN
Melt-spun ribbons were produced from the Pr₈Dy₁Fe₆₀Co₇Mn₆B₁₄Zr₁Ti₃ base alloy at the surface velocity of the cooper wheel of 30 m/s. The studies showed amorphous structure of ribbons and their soft magnetic properties. X-ray diffraction was used to determine phase constitution of all obtained samples. Annealing of ribbons caused formation of nanocomposite structure, which was a result of coexistence of hard magnetic RE₂(Fe,Co)₁₄B and soft magnetic α-Fe phases. Basic magnetic properties such as: coercivity _{J}H_{c}, remanence J_{r} and maximum energy product (BH)_{max} were determined from the measured hysteresis loops. The microstructure of selected specimens was observed by transmission electron microscopy technique.
18
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The Influence of Alloy Admixture on Structure and Properties of rm La(Fe, Co, Si)_{13}-Type Phase

39%
Gębara P., Pawlik P., Škorvánek I., Marcin J., Wysłocki J., Szwaja M., Pawlik K.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 5-6
1285-1287
EN
In the present study, the influence of Al and Ga admixture on the lattice parameters and the Curie point T_{C} of the La(Fe, Co, Si)_{13} compound was discussed. The measurements were carried out on ribbon samples of LaFe_{11.0}Co_{0.8}Si_{1.2}, LaFe_{11.0}Co_{0.8}(Si_{0.4}Al_{0.6})_{1.2} and LaFe_{11.0}Co_{0.8}Si_{1.1}Ga_{0.1} alloys. The samples were subjected to annealing in the inert gas atmosphere at 1323 K for 24 h. The change of lattice parameters a with admixture of Al and Ga was determined from the X-ray diffraction analysis. Furthermore, changes of the Curie point with the alloy composition were observed.
19
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Magnetic Properties and Phase Constitution of the Nanocrystalline Fe₆₅Pr₉B₁₈W₈ Alloy Ribbons

39%
Filipecka K., Pawlik P., Kozdraś A., Filipecki J., Pawlik K., Wysłocki J.
Acta Physica Polonica A
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2017
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vol. 131
|
issue 5
1207-1211
EN
The aim of the present work was to investigate the phase constitution and magnetic properties of the rapidly solidified Fe₆₅Pr₉B₁₈W₈ alloy ribbons in the as-cast state and subjected to annealing. The base alloy was prepared by arc-melting of the high purity elements under the Ar atmosphere. The ribbon samples were obtained by the melt-spinning technique under a low pressure of Ar. The studies have shown an amorphous structure of the ribbon in the as-cast state and its soft magnetic properties. Annealing at various temperatures for 5 min resulted in an evolution of the phase constitution that caused changes in magnetic properties of the alloy. The crystallization behavior was studied using differential scanning calorimetry. In order to determine the phase composition of annealed ribbons, X-ray diffractometry was used. The evolution of microstructure and phase constitution was verified by the Mössbauer spectroscopy. The magnetic properties were determined from hysteresis loops measured by a vibrating sample magnetometer in the external magnetic field up to 2 T at room temperature.
20
Content available remote

Thermomagnetic Properties of LaFe_{11.0}Co_{0.8}(Si_{1-x}Al_{x})_{1.2} (x=0, 0.6) Alloys

33%
Gębara P., Pawlik P., Skorvanek I., Marcin J., Pawlik K., Przybył A., Wysłocki J., Szwaja M., Filipecka K.
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|
vol. 126
|
issue 1
166-167
EN
In the present work, Curie temperature, refrigeration capacity and cooling power of the LaFe_{11.0}Co_{0.8}(Si_{1-x}Al_{x})_{1.2} (where x=0, 0.6) alloys, are investigated. The value of Curie temperature was found to be 280 and 290 K for x=0 and 0.6, respectively. The determined values of cooling power (RCP) and refrigeration capacity (RC) differ only slightly for both investigated alloys. The maximum values of RCP and RC obtained under the change of external magnetic field from 0 to 5 T are 433 J/kg (for x=0) and 290 J/kg (for x=0.6), respectively.
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