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1
Content available remote Mechanical Alloying - a Novel Method for Synthesis and Processing of Materials
100%
Oleszak D.
Acta Physica Polonica A
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1999
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tom 96
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nr 1
101-112
EN
High energy ball milling (mechanical alloying) has recently become a popular research topic. As the non-equilibrium processing method, this technique may be used for the synthesis of many materials, including metastable ones. In many cases these materials exhibit the structure and properties quite different from materials prepared by conventional methods. In this paper some examples of metastable structures synthesized by mechanical alloying are described. The results of mechanical alloying in the Fe-Al system are presented as well.
2
Content available remote High Pressure High Temperature Compaction of AA6061-AlNb Composite Powders
63%
Dąbrowska S. , Oleszak D.
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tom 126
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nr 4
928-930
EN
X-ray diffraction, scanning electron microscopy and hardness measurements were applied as experimental methods to investigate the structure and properties of the crystalline-amorphous Al-based composites prepared by mechanical alloying and subsequent high pressure high temperature compaction of the powders. It was possible to obtain bulk, fully dense crystalline-amorphous composites and the applied compaction technique allowed preservation of amorphous structure in the composite. Addition of amorphous Al_{60}Nb_{40} phase to AA6061 alloy resulted in significant increase of hardness of the composite (120 HV), comparing to pure Al alloy compacted at the same conditions (75 HV).
3
Content available remote Mössbauer Spectroscopy Studies of Multiferroic (BiFeO_3)_{1 - x}-(BaTiO_3)_{x} Solid Solutions Prepared by Mechanical Activation
51%
Jartych E. , Malesa B. , Antolak-Dudka A. , Oleszak D.
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tom 125
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nr 3
837-839
EN
X-ray diffraction and ^{57}Fe Mössbauer spectroscopy were applied as complementary methods in order to investigate the structure and hyperfine interactions of (BiFeO_3)_{1-x}-(BaTiO_3)_{x} solid solutions prepared by mechanical activation and subsequent heat treatment.
4
Content available remote Structure and Hyperfine Interactions of Mechanically Activated Delafossite CuFeO₂
51%
Siedliska K. , Pikula T. , Oleszak D. , Jartych E.
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tom 133
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nr 3
372-375
EN
Delafossite CuFeO₂ belongs to multiferroic class of materials. In this work, copper ferrite was prepared by mechanical activation with subsequent thermal treatment. X-ray diffraction and Mössbauer spectroscopy were used as complementary methods to study the structure and hyperfine interactions of the material. As proved by X-ray diffraction, CuFeO₂ compound was obtained with relatively low amount of secondary phases like CuO and CuFe₂O₄. The Mössbauer spectroscopy revealed paramagnetic character of the compound at room temperature. The purest delafossite CuFeO₂ was obtained by mechanical activation of pre-milled precursors and sintering at 1173 K. The temperature of thermal treatment is lower by 100 K as compared to the traditional solid-state synthesis.
5
Content available Fabrication, Structure and Consolidation of NiAl-Al_2O_3 Mechanically Alloyed Nanocomposite Powders
51%
Oleszak D. , Michalski A. , Majewski T.
Acta Physica Polonica A
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2002
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tom 102
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nr 2
187-192
EN
Reactive milling of NiO + Al powder mixture resulted in the formation of NiAl-Al_2O_3 nanocomposite powders, with a crystallite size of about 20 nm. The Hall-Williamson analysis revealed that NiAl showed an orientation dependent crystallite size after short processing time and orientation dependent internal strain after long milling time. Both anisotropies were removed by heating the powders in the differential scanning calorimetry. Calorimetric studies showed one exothermic effect attributed to the reduction reaction of NiO and endothermic one associated with melting of Al. Two methods were applied for powders compaction: resistance sintering and pulse electric discharge. In both cases the densities of about 90% of the theoretical value were achieved. A significant increase in average NiAl crystallites size in compacted samples was observed, up to several hundreds of nanometers.
6
Content available remote Structural Investigation of Rapidly Quenched FeCoPtB Alloys
51%
Grabias A. , Latuch J. , Oleszak D. , Kopcewicz M.
Acta Physica Polonica A
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2011
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tom 119
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nr 1
68-71
EN
Two sets of Fe_{52-x}Co_{x}Pt_{28}B_{20} (x=0-26 at.%) and Fe_{60-x}Co_{x}Pt_{25}B_{15} (x=0-40 at.%) alloys were prepared in the form of ribbons by the rapid quenching technique. Structure of the samples was characterized by Mössbauer spectroscopy and X-ray diffraction. In the as-quenched alloys the amorphous phase coexisted with the fcc-(Fe,Co)Pt disordered solid solution. Differential scanning calorimetry measurements performed in the range 50-720 °C revealed one or two exothermal peaks. The magnetically hard ordered L1_{0} (Fe,Co)Pt and magnetically soft (Fe,Co)_{2}B nanocrystalline phases were formed due to thermal treatment of the alloys. The influence of Co content on the structure of the as-quenched and heated alloys was studied.
7
Content available remote Hyperfine Interactions and Some Magnetic Properties of Nanocrystalline Co_{40}Fe_{50}Ni_{10} and Co_{50}Fe_{45}Ni_{5} Alloys Prepared by Mechanical Synthesis and Subsequently Heat Treated
51%
Pikula T. , Oleszak D. , Pękała M.
Acta Physica Polonica A
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2011
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tom 119
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nr 1
52-55
EN
Co_{40}Fe_{50}Ni_{10} and Co_{50}Fe_{45}Ni_{5} ternary alloys were prepared by mechanical alloying method. To check the stability of their structure thermal treatment was applied subsequently. As X-ray diffraction studies proved the final products of milling were the solid solutions with bcc lattice and the average grain sizes ranged of tens of nanometers. After heating of the Co_{50}Fe_{45}Ni_{5} alloy up to 993 K the mixture of two solid solutions with bcc and fcc lattices was formed. In other cases thermal treatment did not change the type of the crystalline lattice. Mössbauer spectroscopy revealed hyperfine magnetic field distributions which reflected the different possible atomic surroundings of ^{57}Fe isotopes. Results of the macroscopic magnetic measurements proved that both investigated alloys had relatively good soft magnetic properties.
8
Content available Structure and Magnetic Properties of Nanocrystalline Fe-Mo Alloys Prepared by Mechanosynthesis
51%
Karolus M. , Jartych E. , Oleszak D.
Acta Physica Polonica A
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2002
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tom 102
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nr 2
253-258
EN
Nanocrystalline samples of Fe_{80}Mo_{20} and Fe_{50}Mo_{50} alloys were prepared by the mechanical milling method. The structure, lattice parameters, and crystallite size were determined by the X-ray diffraction. The magnetic properties of the milled products were determined by the M"ossbauer spectroscopy. It was observed that in the case of the Fe_{80}Mo_{20} alloy a solid solution of Mo in Fe was formed with the lattice parameters of Fe increasing from 0.28659 nm to 0.29240 nm and the crystallite size decreasing from 250 nm to 20 nm. In the case of the Fe_{50}Mo_{50} alloy there were no clear changes in values of the lattice parameters of Fe and Mo during the milling process, but the crystallite size decreased from 200 nm to 15 nm. Mössbauer spectra revealed different magnetic phases in the mechanosynthesized Fe-Mo samples. In the case of the Fe_{80}Mo_{20} alloy, the spectrum for the milled mixture indicated the formation of a solid solution. In contrast, for the Fe_{50}Mo_{50} the spectrum indicated the disappearance of the ferromagnetic phase.
9
Content available remote Structure and Mössbauer Spectroscopy Studies of Multiferroic Mechanically Activated Aurivillius Compounds
45%
Mazurek M. , Oleszak D. , Pikula T. , Karolus M. , Jartych E.
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tom 126
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nr 4
975-978
EN
X-ray diffraction and ^{57}Fe Mössbauer spectroscopy were applied as complementary methods to investigate the structure and hyperfine interactions of the Aurivillius compounds prepared by mechanical activation and subsequent heat treatment. Preliminary milling of precursors enhanced the diffusion process and pure Aurivillius compounds were obtained at lower temperature as compared with conventional solid-state sintering technology (lower at least by 50 K). All the investigated Aurivillius compounds are paramagnetic materials at room temperature.
10
Content available remote A Study of Point Defects in the B2-Phase Region of the Fe-Al System by Mössbauer Spectroscopy
38%
Hanc A. , Kansy J. , Dercz G. , Pająk L. , Oleszak D. , Mrzigod J.
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nr 6
1555-1562
EN
In this work, we employed the Mössbauer spectroscopy and X-ray powder diffraction in a study of point defect formation in intermetallic phases of the B2 structure of the Fe-Al system as a function of Al concentration. The results are compared with the concentrations of point defect determined from positron annihilation data. In the Mössbauer effect, two types of samples are investigated: Fe-Al alloys with few additives obtained by induction melting and Al-rich metallic powders produced by the self-decomposition method and intensive grinding of high energy in the electro-magneto-mechanical mill. We present the values of the ^{57}Fe isomer shift and quadrupole splitting for the components describing the point defect in the local environment of a Mössbauer nuclide. The concentration of the Fe vacancies and Fe atoms substituting Al (Fe-AS) are determined. The results showed that an increase in Al content causes an increase in vacancy and Fe-AS concentration.
11
Content available remote Mössbauer Study of Mechanosynthesized and Thermally Treated Co-Fe-Ni Alloys
38%
Pikula T. , Oleszak D. , Pękała M. , Mazurek M. , Żurawicz J. , Jartych E.
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nr 6
1545-1553
EN
Mechanical alloying was used to prepare Co_{40}Fe_{60}, Co_{60}Fe_{35}Ni_{5}, Co_{40}Fe_{45}Ni_{15}, and Co_{40}Fe_{35}Ni_{25} alloys from the elemental powders. As X-ray diffraction studies proved the final products of milling were the solid solutions with bcc or fcc lattice and the average grain size between 20 and 50 nm. After heating of the alloys up to 993 K, the mixtures of two solid solutions with bcc and fcc lattices were formed in the case of Co-Fe-Ni alloys. Thermal treatment did not influence the type of the lattice of Co_{40}Fe_{60} alloy. The Mössbauer spectroscopy revealed hyperfine magnetic field distribution ranged from 33 to 38 T for Co_{40}Fe_{60} alloy and from 30 to 37 T for Co-Fe-Ni alloys. In the case of two-phase alloys, distributions were decomposed into two simple Gaussian functions using the numerical fitting. Magnetic measurements allowed to determine the effective magnetic moments and the Curie temperatures of the obtained alloys.
12
Content available remote Electrical and Magnetic Properties of Selected Fe-Based High Entropy Alloys
32%
Perzyńska K. , Go A. , Szymański K. , Biernacka M. , Hawełek Ł. , Kalska-Szostko B. , Oleszak D. , Rećko K. , Waliszewski J. , Zaleski P.
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tom 126
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nr 4
999-1004
EN
The electrical and magnetic properties of Fe_{0.5}A_{0.5} alloys are presented, where the A corresponds to various compositions of the elements: A = (Al, Si, V, Cr, Co, Ga, Ni, Ge). The system is closely related to the known family of high entropy alloys. The samples were synthesized by arc melting and/or melt spinning technique and exhibit a regular type of crystal structure. Lattice parameters are systematically smaller than the estimates based on metallic radiuses of the elements. Temperature dependences of resistivities show maxima for some compositions. This behavior is consistent with results of electronic structure calculations, where a low density of states at the Fermi level were predicted. Also the measured magnetic moments are in good agreement with results of calculations. It is thus presented that some physical properties can be designed by appropriate choice of the chemical composition within the same simple structure.
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