Hard/soft nanocomposites (NCs) of SrNi0.02Zr0.02Fe11.96O19 (SrNiZr)/MFe2O4 (M = Mn, Co, Cu, and Zn) were prepared using a one-pot sol-gel auto-combustion technique. All produced samples showed smooth ...M − H curves and single peaks on the dM/dH against H curves. This indicates that complete exchange-coupled effects between phases were achieved. Furthermore, the squareness ratio SQR=(Mr/Ms) was obtained and found to be higher than 0.5 at 300 K. This refers to the occurrence of excellent exchange coupling behavior among the soft and hard ferrites, and their structures consist of a single magnetic domain. The electrodynamic parameters were investigated in the 2–18 GHz frequency band using a coaxial line. The dependences of the real and imaginary parts of μ and ε as a function of frequency were determined from the measured S-parameters. A strong correlation between the chemical composition of the soft magnetic phase and the electrodynamic parameters of the composite was observed. This was analyzed in terms of the atomic weight and configuration of the electronic shells of the A-cation in the soft phase. The electromagnetic absorption (EMA) of the investigated composites was estimated from the reflection losses calculated from μ and ε. The maximal EMA value was observed.
Herein, we investigated the correlation between the chemical composition, microstructure, and microwave properties of composites based on lightly Tb/Tm-doped Sr-hexaferrites ...(SrTb0.01Tm0.01Fe11.98O19) and spinel ferrites (AFe2O4, A = Co, Ni, Zn, Cu, or Mn), which were fabricated by a one-pot citrate sol–gel method. Powder XRD patterns of products confirmed the presence of pure hexaferrite and spinel phases. Microstructural analysis was performed based on SEM images. The average grain size for each phase in the prepared composites was calculated. Comprehensive investigations of dielectric properties (real (ϵ′) and imaginary parts (ϵ′′) of permittivity, dielectric loss tangent (tan(δ)), and AC conductivity) were performed in the 1–3 × 106 Hz frequency range at 20–120 °C. Frequency dependency of microwave properties were investigated using the coaxial method in frequency range of 2–18 GHz. The non-linear behavior of the main microwave properties with a change in composition may be due to the influence of the soft magnetic phase. It was found that Mn- and Ni-spinel ferrites achieved the strongest electromagnetic absorption. This may be due to differences in the structures of the electron shell and the radii of the A-site ions in the spinel phase. It was discovered that the ionic polarization transformed into the dipole polarization.
M-type hexaferrite BaFe12−xInxO19 (x = 0.1, 1.2) samples were investigated by high resolution neutron powder diffraction and vibration sample magnetometry in a wide temperature range of 4–730K. ...Structural and magnetic parameters were determined including the unit cell parameters, ionic coordinates, thermal isotropic factors, occupation positions, bond lengths and bond angles, microstrain values and magnetic moments. In3+ cations may be located only in the Fe1 - 2a and Fe2 - 2b crystallographic positions with equal probability for the x = 0.1 sample. At x = 1.2 about half of In3+ cations occupy the Fe5 - 12k positions whilst the other half are equiprobably located in the Fe1 – 2a and Fe2 – 2b positions. The spontaneous polarization was observed for these compositions at 300K. The influence of structural parameters on the temperature behavior of Fe3+(i) - O2- - Fe3+(j) (i, j = 1, 2, 3, 4, 5) indirect superexchange interactions was established. With the substitution level increase the superexchange interactions between the magnetic positions inside and outside the sublattices are broken which leads to a decrease in the value of the corresponding magnetic moments.
The mechanical and tribological properties of Mo(C)N coatings with different carbon concentration have been investigated. The set of coatings with different chemical composition were grown using ...cathodic arc evaporation in various atmosphere composition (nitrogen and acetylene mixture) in the vacuum chamber. The coatings have been tested in macro- and micro-scale. The tests in macro-scale have included: surface morphology (SEM, contact profilometry), hardness (nanoindentation), adhesion (scratch test), friction and wear (pin-on-disc). AFM method has been applied to measure tribological properties: friction coefficient and friction force, and wear in micro-scale.
The highest carbon concentration in the coatings has been about 19at.%. The coatings have shown very good adhesion to steel substrates, to 60N. The hardness of the coatings has reached about 44GPa for carbon free MoN with evident minimum, about 34GPa for coating with about 14at.% of carbon. The wear rate of coatings tested in ball-on-disc system (macro-scale) has been very low, even to (4.7±1.6)×10−17m3/Nm for Mo0.64C0.07N0.29 coating and about two orders of magnitude lower than in AFM test (micro-scale) - 9.6×10−14m3/Nm. Coefficient of friction in macro-scale has been about one level higher than in micro-scale, for Mo0.64C0.07N0.29 coating it has been 0.42 and 0.041 respectively.
•MoN and MoCN coatings deposited by cathodic arc evaporation in nitrogen atmosphere•MoCN coatings were formed using different acetylene flow rates.•Tribological properties were tested in macro- (pin-on-disc) and micro-scale (AFM).•Coefficient of friction in macro-scale is one order of magnitude higher than in micro-scale.•Wear rate in macro-scale is two levels lower than in micro-scale.
Cr–O–N coatings were formed by cathodic arc evaporation at different O2/(N2+O2) relative oxygen concentrations onto HS6-5-2 (DIN standard) steel substrates. The chemical and phase composition, ...surface morphology on the as-deposited coatings were investigated by Wavelength Dispersive Spectrometry, X-ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy and Raman Spectroscopy. The coatings deposited in pure nitrogen atmosphere had a cubic CrN structure. Structural properties of the coatings synthesized in mixed oxygen and nitrogen atmosphere depended strongly on the relative oxygen concentration. High relative oxygen concentration caused amorphization of the coating. XRD diffraction lines were shifted and broadened, indicating increasing stress and decreasing mean crystallite size, from 109nm for coatings deposited at relative oxygen concentration equal 0% to 23nm at 20%. The coatings formed at 50% relative oxygen concentration had a rhombohedral Cr2O3 structure with a grain size of about 11nm and lattice distortion of about 2%. Increasing the relative oxygen concentration also increased the surface roughness and the fraction of the surface rate covered by macroparticles.
•Cr-O-N coatings were deposited using cathodic arc evaporation•The increase in the relative oxygen concentration causes macropoarticle number increase•The coatings with oxygen concentrations to 23 at.% have cubic CrN structure and coating with 56 at.% - rhombohedral Cr2O3 structure•The coatings with oxygen concentrations to 23 at.% have lower roughness than coating with 56 at.%•The increase in the relative oxygen concentration causes grain size decrease
•Ni-Fe coatings with various structure were obtained via controlled electrodeposition.•A nonlinear change in hardness was found during the study by nanoindentation.•The explanation was found in the ...nature of elastoplastic energy relaxation.•Strong correlation between microstructure and deformation mechanisms was found.•The possibilities of the surface and volume hardening of material was shown.
This article contains the study of correlation between the microstructure, mechanical properties and mechanisms of elastoplastic deformation of Ni-Fe coatings that were grown in five electrodeposition modes and had fundamentally different microstructures. A nonlinear change in hardness was detected using nanoindentation. Explanation of the abnormal change in hardness was found in the nature of the relaxation method of elastoplastic energy under load. It is shown that the deformation of coatings with a grain size of 100 nm or more occurs due to dislocation slip. A decrease in grain size leads to the predominance of deformation due to rotations and sliding of grains, as well as surface and grain boundary diffusion. The effect of deformation mechanisms on the nanoscale hardness of Ni-Fe coatings was established. Full hardening of the coatings (both in the bulk and on the surface) was achieved while maintaining the balance of three mechanisms of elastoplastic deformation in the sample. Unique coatings consisting of two fractions of grains (70% of nano-grains and 30% of their agglomerates) demonstrate high crack resistance and full-depth hardening up to H = 7.4 GPa due to the release of deformation energy for amorphization and agglomeration of nanograins.
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Consideration has been given to the possibility of ensuring a high level of broadband signal power in the tracts of a wireless device between the sending–receiving module and the antenna fabricated ...using various materials up to sounding in the most frequently used ranges, viz., 3G, 4G, and 5G. It is suggested that the required level of power transfer be achieved using composite materials with controlled microwave properties (dielectric and magnetic permeabilities) whose variations change the wave resistance and geometric dimensions of the microstrip line, which expands the opportunities for ensuring the required electromagnetic characteristics of a mobile device. In the course of investigation, an estimate was made of the possibility of using a mobile antenna fabricated using a composite material on the basis of fluorinated ethylene–propylene in combination with strontium hexaferrite SrFe
12
O
19
for advanced fifth-generation systems without excluding the possibility of the antenna′s operation in systems of the second, third, and fourth generations. Advantages of using composite materials in implementing antenna devices in 5G technologies are shown.
Ternary chromium based coatings (Cr-O-N) were formed on HS6-5-2 steel substrates using a vacuum arc plasma flux coating system at different relative oxygen concentrations, O2(x) = O2/(N2 + O2). The ...mechanical and tribological properties of the coatings were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), hardness measurements, wear test and adhesion tests (scratch test and Daimler-Benz test). Special attention was paid to coating adhesion and failure modes in the adhesion tests. The coefficient of friction, wear rate and adhesion decreased as the relative oxygen concentration increased. Hardness of the coatings showed the opposite effect, increasing from approximately 19 GPa–30 GPa. The dominant failure mode of Cr-O-N coatings was abrasion. Individual micro fragmentation was also observed for Cr-O-N coating with O2(x) = 20%.
•Cr-O-N coatings were deposited using cathodic arc evaporation at various relative oxygen concentration.•Adhesion is strongly dependent on oxygen concentration in the coating.•An increase in the relative oxygen concentration results in hardness increase and adhesion decrease.•Coefficient of friction and wear rate decrease with an increase in the relative oxygen concentration.
The Ni-Fe thin films were produced via electrodeposition in four different modes - direct current, and three types of pulse-modes with different pulse duration onto Au sublayer. The correlation ...between technological parameters of the electrodeposition and microstructure was demonstrated. Analysis of microstructure evolution revealed an un-expected changing of the film growth mechanism from “island” to “layer-by-layer” with the decreasing of the grain size less than 10 nm. Explanation was found in binding energies competition, that has been defined using the unique AFM method, based on recording the angle of the cantilever twist, when scanning in contact with the surface.
The aim of these work was to investigate low temperature fast synthesis of cobalt spinel ferrite polycrystalline ceramics. The idea of combining high temperature and high pressures was in the ...possibility of a sharp decrease in the synthesis time by the lowering the threshold for activation of chemical interaction due to increasing the rate of diffusion kinetics. Test samples with 2–3 orders of magnitude less duration and reduced sintering temperature by 400º C comparing to conventional sintering were synthesized from initial oxides using solid state reactions method under high-pressure. The thermobaric conditions (combination of high temperatures and high pressures during synthesis) on phase content, structural properties, magnetic and electrical properties of the CoFe2O4 spinels were also investigated. The synthesis was performed at T = 800 °С under high pressures (P = 1–5 GPa) and duration of 1 min. Evolution of the phase composition, microstructure, magnetic and electrical properties of CoFe2O4 ceramics as function of the synthesis pressure was investigated using XRD, SEM, VSM and impedance spectroscopy respectively. Results of XRD demonstrate the formation spinel-like main phase (SG: Fd-3 m) with impurities. It was observed that average grain size decreased from 661 to 355 nm with P increasing from 1 till 5 GPa respectively. It was observed that the P increase induce the non-linear changes in magnetic properties. Thus, Ms decreased from 70,8–60 emu/g while Hc and Mr had a slight increasing trend with increase P from 1 till 5 GPa. CoFe2O4 samples that were produced under higher pressures demonstrated dramatically higher values of permittivity. The proposed method is perspective way for production of the high-density magnetic ceramics with significantly reduced sintering time in comparison with the traditional solid state reactions method. The modification of the proposed method for control phase composition and physical properties is the goal for further investigations.
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•Impact of thermobaric conditions on electrical, magnetic properties of Co-ferrite is studied.•Average grain size decreases from 661 nm to 355 nm with increasing pressure from 1 GPa to 5 GPa.•High permittivity value of 5045 at 120 Hz is obtained at sintering pressure P = 5 GPa.•Saturation magnetization vary from 70,8 to 59,2 emu/g with decreasing pressure.
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