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Bismuth ferrite (BiFeO 3) particles are prepared by a combined mechanochemical−thermal processing of a Bi 2 O 3 + α-Fe 2 O 3 mixture. Structural, magnetic, hyperfine, morphological and chemical properties of the as-prepared BiFeO 3 are studied using X-ray diffraction (Rietveld refinement), 57 Fe Mössbauer spectroscopy, SQUID magnetometry, electron...
For the first time, a spinel-type high entropy oxide (Zn 0.25 Cu 0.25 Mg 0.25 Co 0.25 )Al 2 O 4 as well as its derivative lithiated high entropy oxyfluoride Li 0.5 (Zn 0.25 Cu 0.25 Mg 0.25 Co 0.25 ) 0.5 Al 2 O 3.5 F 0.5 and oxychloride Li 0.5 (Zn 0.25 Cu 0.25 Mg 0.25 Co 0.25 ) 0.5 Al 2 O 3.5 Cl 0.5 are prepared in the nanostructured state via high-...
Magnetic abrasive machining is one of the advanced finishing processes that produce a high level of surface quality of any type. The productivity of the finishing process and the quality of the treated surfaces are determined by magnetic and abrasive properties of the working media. To synthesize effective magneto abrasive composites with the size...
Mullite-type Bi2(Ga1-xFex)4O9 solid solutions, with 0.1 ≤ x ≤ 0.9, have been synthesized by a combination of mechanical and thermal treatments of a Bi2O3/Ga2O3/α-Fe2O3 stoichiometric mixture. The microstructure of the as-prepared materials on the long-range and local atomic scales was investigated by X-ray diffraction and ⁵⁷Fe Mössbauer spectroscop...
The response of the structure of the M-type barium hexaferrite (BaFe12O19) to mechanical action through high-energy milling and its impact on the magnetic behaviour of the ferrite are investigated. Due to the ability of the 57Fe Mössbauer spectroscopic technique to probe the environment of the Fe nuclei, a valuable insight on a local atomic scale i...
Chemical reduction-oxidation (redox) processes induced by mechanical treatment represent an important class of solid-state reactions. In the present work, selected examples are presented of the preparation of nanocomposites by mechanochemical redox reactions, starting from simple binary or complex ternary oxides. The important impact of the work, f...
In this work, the ZnO spherical nanoparticles with a diameter in the range of 10–30 nm have been prepared via mechanochemical oxidation of metallic Zn powders treated in a vibratory ball mill in the presence of air and liquid nitrogen. The as-prepared nanocrystals were characterized by XRD, HR-TEM, FTIR, XPS, and UV–vis spectroscopy. The results sh...
A non-thermal route to oxide nanocomposites by mechanochemical redox reactions in the alpha-Fe2O3 + SnO system is presented. The important impact of the work, from the methodology point of view, is the combined application of Fe-57 and Sn-119 Mossbauer spectroscopies to the study of the mechanically induced redox processes, resulting in the reducti...
Nanocrystalline ZnSe was prepared by mechanochemical synthesis in a laboratory mill and an industrial mill from the mixture of Zn and Se powdered precursors. XRD measurements indicate the formation of the cubic and hexagonal modifications of ZnSe during mechanochemical synthesis in the laboratory mill. Hexagonal modification disappears with increas...
Mechanochemical synthesis of tin diselenide, SnSe2, was performed by high-energy milling of tin and selenium powder in a planetary ball mill. The mechanosynthesized product was characterized by X-ray diffraction, 119SnMAS NMR and 119Sn Mössbauer spectroscopy, which confirmed the presence of the hexagonal SnSe2 phase after 100 min of milling. The si...
A series of Bi2(GaxAl1−x)4O9 solid solutions (0≤x≤1), prepared by mechanochemical processing of Bi2O3/Ga2O3/Al2O3 mixtures and subsequent annealing, was investigated by XRD, EDX, and 27Al MAS NMR. The structure of the Bi2(GaxAl1−x)4O9 solid solutions is found to be orthorhombic, space group Pbam (No. 55). The lattice parameters of the Bi2(GaxAl1−x)...
Interactions in the copper-gallium-tin ternary system are studied. New phase formation involves the step of dissolution of
solid copper alloys in a liquid phase. The induction period of tin segregation in an autonomous phase depends on tin concentration
in the feed. The formation of solid solution of gallium in tin is suggested.
The bulk and surface properties of magnetically diluted Cd0.6Mn0.4S nanocrystals synthesized by solid state route in a planetary mill were studied. XRD, SEM, TEM (HRTEM), low-temperature N2 sorption, nanoparticle size distribution as well as SQUID magnetometry methods have been applied. The measurements identified the aggregates of small nanocrysta...
The evolution of nanocrystalline n-MgFe2O4 by high-energy milling a mixture of MgO and alpha-Fe2O3 for periods of between 0 h and 12 h has been investigated by neutron diffraction in addition to previous Mossbauer, XRD and HRTEM measurements. Complete transformation of the milled products to n-MgFe2O4 only occurs on milling to similar to 8 h even t...
The phase composition and morphology of the diffusion-hardened compound containing Cu/Bi mechanocomposite with nanoscale metals
and liquid gallium were examined by synchrotron radiation X-ray diffraction, as well as by atomic force and electron microscopic
techniques.
The goal of the work was to prepare magnetic elastomers based on a highly elastic polymer matrix (1,4-cis butadiene rubber) filled with magnetic particles. Barium ferrite (BaFe 12O 19) powder with a relatively high saturation magnetization and coercivity was synthesized by co-precipitation method and subsequently used as a magnetic filler. The crys...
Among the many types of preparation and processing techniques, the nonconventional mechanochemical route has been recognized
as a powerful method for the production of novel, high-performance, and low-cost nanomaterials. Because of their small constituent
sizes and disordered structural state, nanoscale materials prepared by mechanochemical route a...
The magnetization enhancement in nanoscale mechanosynthesized MgFe2O4 is reported and is discussed in terms of a modified core–shell model, in which a competition between the effects of spin canting and site exchange of cations plays a decisive role. Because of the nearly random distribution of cations, the surface shell of nanoparticles exhibits a...
Quantitative microstructural information is obtained on the nonequilibrium cation arrangement in high-energy milled MgAl2O4, ZnFe2O4, and NiFe2O4 by means of 27Al MAS-NMR, XPS, and 57Fe Mössbauer spectroscopy, respectively. Independently of the ionic configuration in the nonactivated materials, the mechanically induced redistribution of cations was...
The single-step synthesis of nanosized MgFe2O4 and NiFe2O4 via mechanochemical processing of binary oxide precursors is followed by 57Fe Mössbauer spectroscopy. Quantitative information is provided on both ionic and spin configurations in mechanosynthesized
spinels. The response of the mechanosynthesized ferrite nanoparticles to changes in temperat...
The mechanochemical reduction of antimony sulphide with elemental iron was studied using a laboratory planetary mill and an industrial eccentric vibratory mill. The composition and properties of the obtained Sb/FeS nanocomposites were analysed by XRD, VSM, 57Fe-Mössbauer spectroscopy, and SEM methods. The process kinetics shows that most of the red...
Nanocrystalline magnesium aluminate (MgAl2O4) powders were prepared by high-energy milling of the bulk material. Due to the ability of nuclear magnetic resonance (NMR) spectroscopy to discriminate between probe nuclei on inequivalent crystallographic sites, valuable insight into the mechanically induced evolution of a local cation disorder in MgAl2...
The single-step synthesis of nanosized MgFe2O4 via mechanochemical processing of binary oxide precursors is reported. The mechanochemical route is followed by X-ray diffraction and 57Fe Mössbauer spectroscopy. The nanoscale nature of the mechanosynthesized material is evidenced by transmission electron microscopy. Quantitative information is provid...
The most remarkable effect in spinel ferrites is the strong dependence of properties on the state of structural disorder and, in particular, on the cation distribution. The thermal stability of the non-equilibrium cation distribution in nanoscale milled spinel ferrites is of considerable relevance to nanoscience and nanotechnology of these compound...
The high-energy milling process is known to induce numerous changes in materials. In this contribution, it is pointed out that the milling of ferrimagnetic oxides leads to an extensive structural disordering such as non-equilibrium distribution of cations over the two non-equivalent cation sublattices provided by the spinel structure. The cation in...
Nanocrystalline nickel ferrite (NiFe2O4) with crystallite size ∼9 nm has been synthesized by high-energy milling method from a mixture of α-Fe2O3 and NiO. Mössbauer spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic states of mechanosynthesized...
The changes in magnesium ferrite (MgFe2O4) caused by high-energy milling are investigated by means of Mössbauer spectroscopy, magnetisation measurements, and electron microscopy. The observed enhancement of the magnetisation in nanoscale milled MgFe2O4 is discussed with respect to the mechanically induced cation redistribution and spin canting.
Metastable nanocrystalline nickel ferrite (NiFe2O4) with crystallite size ∼9 nm produced by high-energy milling the bulk material has been annealed at elevated temperatures to investigate the changes induced in the microstructure and the magnetic properties. High-temperature X-ray diffraction, thermogravimetric measurements, Mössbauer spectroscopy,...
The changes in magnesium ferrite (MgFe2O4) caused by high-energy milling are investigated by means of Mössbauer spectroscopy. A collapse of the magnetic hyperfine
fields far below the Néel temperature of the bulk ferrite is observed in nanoscale milled MgFe2O4. The influence of superparamagnetism and collective magnetic excitations on Mössbauer spe...
The changes in nickel ferrite (NiFe2O4) due to high-energy milling in a stainless steel vial have been investigated by Mössbauer spectroscopy, X-ray diffraction (XRD), and thermal analysis. The milling process reduces the average crystallite size of NiFe2O4 to the nanometer range. The Mössbauer spectra show the formation of metallic iron and of a p...
The changes in magnesium ferrite (MgFe2O4) caused by high-energy milling are investigated. Mechanical treatment reduces the average crystallite size of MgFe2O4 to the nanometer range and induces cation redistribution between tetrahedral and octahedral sites. The degree of inversion of the mechanically treated ferrite is compared with that of MgFe2O...
The structural and magnetic evolution in nickel ferrite (NiFe2O4) caused by high-energy milling are investigated by Mssbauer spectroscopy. It is found that the nanostructural state of the milled NiFe2O4 is characterized by a reduced concentration of iron ions on tetrahedral sites. The degree of inversion in NiFe2O4 is calculated from the subspectra...
Mssbauer spectroscopy can provide information on a large variety of mechanochemical processes in solids. In this overview, selected examples are presented of Mssbauer studies of homogeneous and heterogeneous mechanochemical reactions in spinel ferrites. Several interesting features are involved in the work, e.g., mechanically induced cation redistr...
The structural and magnetic evolution in magnesium ferrite (MgFe2O4) caused by high-energy milling is investigated by Mssbauer spectroscopy.
Zinc ferrite forms the structure of a normal spinel. A mechanical activation and a mechanosynthesis of zinc ferrite at room temperature lead to the formation of the metastable inverse spinel structure. The changes in the surface structure of mechanically activated and of mechanosynthesized zinc ferrite as a function of the mechanical treatment time...
New mechanochemical methods of material synthesis have received increased attention in recent years. The changes in the structure of the mechanosynthesized zinc ferrite (synthesized by the high-energy milling of the ZnO/Fe2O3 mixture) and of mechanically activated spinel ferrite (synthesized by the conventional thermal method, followed by mechanica...
The character of the mechanically induced structural disorder and nature of the metastability of mechanosynthesized zinc ferrite are elucidated by investigation of its structure. Attention is concentrated on the explanation of an origin of mechanically induced changes in magnetic properties of the nanoscale mechanosynthesized ferrite. The range of...
In powder mixtures of ZnO and TiO2 the compounds Zn2TiO4, ZnTiO3, and Zn2Ti3O8 can be formed as a result of solid state reactions. The formation of the double oxides is essentially determined by the microstructure of the powder mixture. Furthermore, the type of the double oxide depends on the TiO2 modification. There exist structural similarities b...
In recent years, zinc ferrite has been used as an absorbent material for hot-gas desulphurization. This experimental work focuses on both the novel synthesis pathway (mechanosynthesis) to zinc ferrite and the study of the high-temperature reactivity of nanoscale mechanosynthesized zinc ferrite in coal gas desulphurization and in the subsequent rege...
This paper describes the mechano-synthesis of ZnS by high intensive milling of elementary sulphur and zinc in a planetary mill. Using complex physical and chemical methods (XRD, surface area measurement, IR and XPS) the probable occurrence of sphalerite was proved. The sphalerite was contaminated by iron (up to 0.14% of Fe) and the product of surfa...
The aim of this study was the preparation of the natural zeolitic material of the clinoptilolite type doped with silver iodide. Natural zeolite from the East Slovakian deposit was used. This natural zeolitic material doped with AgI (content of AgI: 28.5%) has been investigated by X-ray powder diffractometry, EDS analysis, scanning electron microsco...
The properties of doped BaTiO3 ceramics prepared from mechanically activated precursors (BaCO3, TiO2, PbO), dopant (Sb) and admixtures (SiO2, Al2O3) were investigated. Mechanical activation of the mixture 1.00 BaCO3 + 1.15 TiO2 + 0.10 PbO brings about an increase in its specific surface and partial amorphization of BaCO3; Ba, O and C occur in the s...
The properties of doped BaTiO3 ceramics prepared from mechanically activated precursors (BaCO3, TiO2, PbO), dopant (Sb) and admixtures (SiO2, Al2O3) were investigated. Mechanical activation of the mixture 1.00 BaCO3 + 1.15 TiO2 + 0.10 PbO brings about an increase in its specific surface and partial amorphization of BaCO3; Ba, O and C occur in the s...
The results obtained by leaching stibnite with a basic solution of sodium hydrogen sulphide are presented in this paper. The intensification of leaching by the mechanical activation produced by grinding the mineral in a planetary mill for 20 min brings about acceleration of the process by tenfold. The non-oxidative leaching of stibnite is a structu...
The dissociative sublimation of mechanically activated cinnabar has been studied in the range 589–658 K. The mechanical activation weakens the Hg-S bonds between chains owing to which the apparent activation energy decreases from 54 to 34 kJ mol−1 and the rate of decomposition of the mineral increases. The morphology of the particles subjected to m...
Nanocomposites in the interacting metal systems Cu-Zr and Cu-Ti were synthesized mechanochemically. The composition and morphology of the composites were studied using X-ray diffraction, electron and atomic force microscopy. INTRODUCTION Recent work [1-3] demonstrated that mechanocomposites can be in wide demand for industry as precursors for conve...