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Mechanical alloying of the elemental powder mixture of iron and multiwalled carbon nanotubes (10, 20 and 30 vol.%) was performed in a high energy planetary ball mill. Nanocomposite materials obtained were examined by X-ray diffraction method as well as by transmission and scanning electron microscopy. It is shown that several phases were forming at the different stages of the milling process, namely, α-(Fe,C) and γ-(Fe,C) supersaturated solid solutions along with the Fe 3- x C and the Fe 7 C 3 carbide phases. The hardness and magnetic properties (Curie temperature and coercive force) of the nanocomposite materials obtained were studied. The process of the mechanical alloying of materials studied has been analyzed. [ABSTRACT FROM AUTHOR]

The DyCu x Ga 4− x −δ alloys ( x = 1.2–0.05) have been studied by the X-ray single-crystal and powder diffraction methods as well as by the magnetometric and XPS techniques. Four individual closely related compounds identified here were shown to be the derivatives of BaAl 4 -type structure (tetragonal or orthorhombically distorted) with the increased multiplicity of their a and b sublattice constants, namely, I-DyCu 1.25−1.12 Ga 2.67−2.80 (1 × 1), II-DyCu 1.07 Ga 2.74 (3 × 3), III-DyCu 0.92−0.76 Ga 2.84−3.00 (3 × 3) and IV-DyCu 0.63−0.06 Ga 3.00−3.57 (9 × 9). All alloys studied are paramagnets at (300–650) K temperature range. The effective paramagnetic moment per Dy atom was found to exceed the value for the Dy 3+ ion (10.65 μ B ). Besides, it increases up to 11.2 μ B with Ga content increasing. Magnetic properties of these alloys are discussed based upon crystal and electronic structure changes. [ABSTRACT FROM AUTHOR]

Nanocomposite materials (NCMs) of the Fe–Cu (4:1) system with/without small addition of carbon nanotubes (CNTs) have been synthesized by mechano-chemical activation of elemental Fe and Cu powders in a high energy planetary ball mill and have been examined by the X-ray diffraction method, SEM and magnetometric studies. The metastable α-(Fe, Cu) supersaturated solid solution is formed in the Fe–Cu nanocomposites during milling process, while a small addition (up to 2 vol.%) of the carbon nanotubes into the Fe–Cu charge results in formation of the martensite-type α-(Fe, Cu, C) phase. The coherent scattering block size of the materials obtained is decreased with milling time increasing. The duration of mechano-chemical activation affects the magnetic properties of nanocomposites studied. Formation of the α-(Fe, Cu, C) phase causes a significant increase of both coercive force and tensile strength of the Fe–Cu (4:1) + CNTs NCMs. [ABSTRACT FROM AUTHOR]

Crystal structures of the ternary DyMn x Ga 3 alloys ( x < 0.45) annealed stepwise at 873 and then at 773 K have been studied by the X-ray powder diffraction method. It was shown that four individual phases are formed in the vicinity of the specific stoichiometric compositions as a result of embedding of the manganese atoms into the octahedral holes of the high temperature DyGa 3 compound. These phases are I-Dy 5 Mn 1− y Ga 15 , II-Dy 4 Mn 1− y Ga 12 , III-Dy 3 Mn 1− y Ga 9 and IV-Dy 2 Mn 1− y Ga 6 . The crystal structures of these phases have been determined and considered as externally or/and internally distorted variants of the AuCu 3 -type structure. The temperature dependencies of magnetic susceptibility were determined by using the Faraday technique. All compounds studied are paramagnets in the temperature range of 300–650 K. The XPS analysis has confirmed that the crystal structure features of the DyMn x Ga 3 alloys and their magnetic properties are caused by the changing of an oxidation degree of the manganese atoms. [ABSTRACT FROM AUTHOR]

Abstract: The structure, magnetic and resistivity characteristics of Co–Si–B metallic glasses containing complex dopants have been investigated. The intervals of thermal stability of the phases existing in the alloys studied have been determined. The temperature dependences of the resistivity were shown to be essentially nonlinear up to a certain temperature, evidencing for the contribution of several scattering mechanisms. Magnetic and resistivity behavior of these alloys are substantially governed by the phase separation within the region of the amorphous state stability and magnetic clusters formation. In the as-cast alloys these clusters are estimated to contain 2–4 Co atoms. Heat treatment significantly affects the structure and magnetic properties. It leads to increase of the Curie temperature and localized magnetic moment, whereas the crystallization temperature remains almost invariable. [Copyright &y& Elsevier]

• Biocompatible superparamagnetic NaFeO 2 nanoparticles synthesized by sol–gel method. • Impact of aging on crystal structure of nanoparticles has studied. • Structural changes affect magnetic parameters of the aged sample. NaFeO 2 magnetic nanoparticles which are biocompatible and have a relatively high saturation magnetization are considered as promising heat mediators for magnetic hyperthermia applications. In this work, we study aging effects in NaFeO 2 nanoparticles and show that they change their structural and magnetic characteristics over time. As-produced NaFeO 2 nanoparticles synthesized by sol–gel technique have been aged in the ambient atmosphere for 10,000 h. Magnetic properties and aging effect were studied by X-ray diffraction and vibrating sample magnetometry at a temperature ranging from 300 to 500 K. Crystal structure of nanoparticles undergoes essential changes, including an increase of lattice parameter and average coherent block size, and decrease of the microdeformation of crystal lattice. These structural changes affect magnetic parameters of the aged sample. It is shown that saturation magnetization becomes higher and Curie temperature tends to increase as the samples undergo the aging processes. [ABSTRACT FROM AUTHOR]

Structural properties of nanocomposite TiAlSiN thin films prepared as monolithic single layer, multilayers and gradient films have been characterized by X-ray diffraction, nano-indentation and atomic force microscopy. The films were deposited onto WC–Co substrates using cathodic arc-plasma. The Al content was varied within the range of Al/Ti=0.5–1.5 and the Si content did not exceed 3.5 at.%. The highest hardness (38–39 GPa) was obtained for samples with Al/Ti=1.0, associated with more effective combination of solid solution hardening and Hall–Petch effect arising from structure refinement by Al and Si addition. In contrast, the films with Al/Ti=1.5 showed the lowest hardness values (30–33 GPa) due to the formation of softer wurtzite-like hcp-AlN phase. Formation of layered films slightly improved hardness with respect to monolithic single layer films of comparable chemical composition. Meanwhile, gradient films (Al/Ti=1.0) showed hardness and modulus values very similar to those obtained for single layer films. Unlike mechanical properties, the formation and propagation of indentation induced cracks appeared more sensitive to film structures (columnar, equiaxed nanograins, …) as well as to growth morphology (monolithic, layered, gradient). The primary cracks appear for all films beneath the indenter at the contact site. The morphology of these cracks consists of a network of short, discontinuous, irregular cracks in columnar films, which gives rise to straight, well-organized repeated crack in fine grain structures. Such modification of crack patterns is attributed to the role of grain boundary sliding which is more pronounced in coarse columnar films than in nanograined materials. [Copyright &y& Elsevier]

Highlights: [•] We study phase equilibria in ternary Ni–Al–Ga in the whole concentration range. [•] Ni(Al,Ga), Ni2(Al,Ga)3, Ni5(Al,Ga)3 extended solid solutions exist in this system. [•] Isothermal section (700°C) of the Ni–Al–Ga system has been constructed. [•] Small additions of Ga increase compressive strength of Ni3(Al,Ga) solid solution. [ABSTRACT FROM AUTHOR]

Abstract: The ternary alloys of the Y–Cu–Ga system have been reinvestigated and the refined data on the compositions and crystal structures of the ternary compounds were received. It was shown that each extended solid solution (ThMn12-, PrFe7-, CaCu5-, BaAl4-, La3Al11-, KHg2-, CaIn2- and CsCl-type structures) consists of several individual isostructural phases, each of them reveals a partial fillings of the certain positions by yttrium or/and copper/gallium atoms. The composition of these phases gradually shifts to the higher yttrium content with increase in Ga-content. Taking into account the structural peculiarities of the extended solid solutions, 23 phases in total were found to exist in the Y–Cu–Ga system at 700°C. [Copyright &y& Elsevier]

Structural features of nanocomposite YCu powder material obtained by mechanical alloying of the equiatomic Y-Cu elemental powder mixture in a high-energy ball mill have been characterized by X-ray diffraction, and scanning electron microscopy. It has been shown that YCu compound with a full ordered CsCl-type structure along with YCu 2 intermetallic have formed at early stage of the milling process (10 min) while a long-time processing product contains these phases as well as Y 2 O 3 oxide. The nanoindentation measurements of the bulk samples compacted after 60 and 120 min of milling have revealed that the mean hardness values H for these samples are higher than those for conventional bulk YCu intermetallic obtained by arc melting. The main reasons for hardness increase are fine-grained microstructure and reinforcement of material by Y 2 O 3 particles uniformly distributed throughout the volume. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fcc NiC monocarbide was synthesized by milling of nickel and CNT/graphite charge. • A two-step carbide formation mechanism has been proposed. • Associated changes in the nickel lattice were evaluated and discussed. • Allotropic form of carbon used makes an impact on NiC crystal structure. • Magnetic moment per nickel atom (2.83μ B) is higher than that of a bulk Ni (1.3μ B). In the present work, a comprehensive study of mechanical alloying of Ni-carbon nanotubes (CNT) and Ni-Graphite equiatomic powder mixtures under the same technological modes has provided to reveal the features of using different types of carbon (CNT or graphite) as a charge component. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and magnetometric study. A novel nanoscale fcc NiC monocarbide was synthesized regardless the type of the charge used. According to the XRD study the formation of this phase takes place in two stages. A two-step carbide formation mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the lattice parameter, lattice strain and residual stresses, which led to the formation of NiC monocarbide were also evaluated and discussed. Parameters of the electronic structure of NiC were calculated using the MStudio MindLab 7.0 software package with the experimental data on the crystal structure of the NiC phase obtained as input. Temperature dependencies of magnetic susceptibility of NiC synthesized have been studied up to 950 K. Carbides synthesized were found to be weak ferromagnets at the room temperature and their Curie temperature T C ranges within 670 – 725 K. The calculated value of the magnetic moment per nickel atom (2.83μ B) is higher than that of a bulk Ni (1.3μ B). Likely, the observed increase of μ is caused by the presence of a certain amount of residual single-domain ferromagnetic Ni nanoparticles in the samples synthesized. [ABSTRACT FROM AUTHOR]

Abstract: New members of the A n B n−1O3n perovskite-like family (Ba5KNb5O18 and Sr6Nb4SnO18 compounds) with n = 6 have been synthesized and studied by the X-ray powder diffraction. Their crystal structures were found to belong to the Ba6Nb4TiO18-type with a = 0.57840(7) nm, c = 4.2532(5) nm and a = 0.5661(1) nm, c = 4.186(1) nm for Ba5KNb5O18 and Sr6Nb4SnO18, respectively. It was shown that Ba and K (A-atoms) are completely disordered in the crystal structure of Ba5KNb5O18 compound. But Nb and Sn atoms (B-atoms) in the crystal structure of the Sr6Nb4SnO18 compound are quite ordered with the preferred Sn+4 and Nb5+ cations localization in the center of perovskite-like block and on the boundaries of these blocks, respectively. Temperature and frequency dependencies of the real components of electric conductivity σ I and dielectric permeability ɛ I; specific electric conductivity at the direct current σ dc have been obtained by the impedance spectroscopy method for Sr6Nb4SnO18. [Copyright &y& Elsevier]

Highlights: [•] We study the crystal structure of GdAl x Ga4−x compounds with 8–66at.% Ga. [•] Existing range of these compounds is fragmented into seven individual regions. [•] The effective magnetic moments have been calculated. [•] The excess magnetic moments are caused by the contribution of the non-4f electrons. [Copyright &y& Elsevier]

Abstract: The crystal structures of seven Ga-rich compounds that exist in the Y–Cu–Ga system were studied by the X-ray single-crystal and powder diffraction methods. The crystal structures of six phases were shown to be constructed from the orthorhombic distorted BaAl4-like fragments by multiplication of its a and b lattice constants. These compounds are: 1-Y1.02Cu1.35Ga2.63 (modified BaAl4-type structure, 1×1 multiplication), 2-Y1.04Cu1.12Ga2.84 and 3-Y1.05Cu1.00Ga2.95 (own type structure, 3×3), 4-Y1.08Cu0.72Ga3.20 (own, 9×9), 5-Y3Cu4Ga7 and 6-Y3.21Cu3.09Ga7.70 (La3Al11, 3×1), 7-YCuGa2 (own, 3×3). [Copyright &y& Elsevier]

The frequency dependence of permeability and power loss are investigated in FINEMET samples after isothermal heat treatments, leading to structural relaxation and/or nanocrystallization. The rapid decrease in power loss and increase in permeability at low frequencies are connected mainly with the structural relaxation and the first period of nanocrystallization. The time scale for the evolution of soft magnetic properties at high frequencies is similar to that for the density change. [Copyright &y& Elsevier]

Abstract: The crystallization kinetics of the amorphous alloys based on was studied under isothermal annealing using magnetometric method. Apparent activation energy of crystallization and Avrami exponent n have been determined. The additions of Ni and Mo were shown to influence weakly on the values of and n. Apparent activation energy of crystallization for the ribbons produced using industrial raw materials agrees within the accuracy of experiment with that for the alloys of identical composition produced from chemically pure components. It was also ascertained that the value of n is mainly determined by the chemical composition of alloy. [Copyright &y& Elsevier]