—Nanotribological tests via atomic force microscopy were optimized by recording the lateral interaction forces between the probe tip and the sample surface in the contact mode. In the case of thin ...film metal materials, the technique enabled us to determine independently the sliding force and the static friction force, which reduced the measurement error of tribological characteristics at the nanoscale by 3—5 times.
Nanosized spinel ferrites Co1−xNixFe2O4 (where x = 0.0–1.0) or CNFO have been produced using a chemical method. The crystal structure's characteristics have been determined through the utilization of ...X-ray diffraction (XRD). It has been demonstrated that all samples have a single phase with cubic syngony (space group Fd3m). The lattice parameter and unit cell volume behavior correlate well with the average ionic radii of Co2+ and Ni2+ ions and their coordination numbers. Thus, an increase in the Ni2+ content from x = 0.0 to x = 1.0 leads to a decrease in the lattice parameter (from 8.3805 to 8.3316 Å) and unit cell volume (from 58.86 to 57.83 Å3). Elastic properties have been investigated using Fourier transform infrared (FTIR) analysis. The peculiarities of the microwave properties have been analyzed by the measured S-parameters in the range of 8–18 GHz. It was assumed that the energy losses due to reflection are a combination of electrical and magnetic losses due to polarization processes (dipole polarization) and magnetization reversal processes in the region of inter-resonant processes. A significant attenuation of the reflected wave energy (−10 … −21.8 dB) opens broad prospects for practical applications.
The correlation between the electromagnetic properties of BaFe12-xDxO19 (0.1⩽x⩽1.2) solid solutions (D = Al3+, In3+ and Ga3+) and the concentration of diamagnetic ions was investigated. The changes ...of electromagnetic properties of the investigated samples were explained using neutron powder diffraction and Mossbauer spectroscopy data. The diamagnetic ions with different ionic radii and electronic configurations were chosen. The transmission spectra of all the samples demonstrated a deep minimum in the frequency range 20–65 GHz which was associated with the natural ferromagnetic resonance. The resonance frequency fres and amplitude were changed by the substitution type and level. With increasing the substitution concentration, the resonance frequency increases from 51 GHz to 61 GHz and decreases from 50.5 GHz to 27 GHz for Al- and In-substituted samples, respectively. More complicated concentration dependences of resonance characteristics were obtained for Ga-substituted samples in a narrow range of 49–50.5 GHz. The value of fres had a minimum around x = 0.6 and further increased to 50.5 GHz for x = 1.2. It was concluded that the intrasublattice interactions were responsible for tailoring the magneto crystalline anisotropy and resonance parameters. More detailed investigations would require the development of phenomenological model on the basis of the electronic structure using Goodenough-Kanamori approaches.
ScIn→Sr NHFs have been synthesized via the sol-gel combustion method. The phase and morphonology were analyzed via XRD, SEM, TEM, and HR-TEM. XRD measurements confirmed the purity of all products ...having the crystallite size (DXRD) of 31–77 nm obtained via Rietveld refinement. The agglomeration of products was observed in SEM and HR-TEM images due to their magnetic character. SEM images revealed the hexagonal-shaped nanoparticles. Mössbauer spectra showed that In3+ and Sc3+ ions are located at generally octahedral (Oh) 4 f2 site. The electron density s of iron ions of 4 f2 and 2a sublattices is affected by doping content. The obtained M-H curves (field-dependence of magnetization) demonstrated ferrimagnetic hysteresis loops at both 300 and 10 K. The analysis of M-H curves also showed that the saturation magnetization (Ms) first declined until x = 0.03, then grew up to x = 0.05, and returned to decrease thereafter. The coercivity (Hc) decreased sharply with Sc-In substitution, transforming the magnetic character of samples from hard to soft. Microwave (MW) properties were measured and analyzed between 33 and 50 GHz. It was demonstrated that the increase of the Sc3+/In3+ concentration led to modifications in amplitude-frequency characteristics of the electromagnetic absorption process. It was shown that Sc3+/In3+ substituted Sr NHFs can be used for developing radioelectronic coatings and providing electromagnetic compatibility.
•Sc3+/In3+ substituted Sr hexaferrites for electromagnetic compatibility.•In3+ and Sc3+ ions are located at generally octahedral (Oh) 4 f2 site.•Ferrimagnetic hysteresis loops at 300 and 10 K.•Modifications in amplitude-frequency properties of the electromagnetic absorption.
(BaFe11.9Al0.1O19)1-x - (BaTiO3)x with x = 0, 0.25, 0.5, 0.75 and 1 bicomponent ceramics has been prepared from single-phase compounds of BaFe11.9Al0.1O19 (x = 0) (BFO) and BaTiO3 (x = 1) (BTO) by a ...standard ceramic technique. The constituent materials have been chosen considering their perspective ferrimagnetic and ferroelectric properties, respectively for BFO and BTO. Moreover, Ba-hexaferrites are reported to exhibit ferroelectricity at room temperature as well, and the combination of two ferroelectric phases is of interest. Systematic investigations of the structural, magnetic and dielectrical properties versus chemical composition (x) have been performed. The ferrimagnetic phase transition temperature is almost independent of the BTO content, which is determined by intensity of the Fe3+-O2--Fe3+ indirect superexchange interactions in the BFO hexaferrite phase. However, the coercivity of composite samples is lower due to the contribution of the microstructure-dependent shape anisotropy to the total magnetic anisotropy energy. The permittivity vs. temperature behavior confirmed the existence of two ferroelectric phase transitions corresponding to structural phase transitions in BTO at ~ 400 K and BFO at ~ 700 K. It has been observed that the dielectrical properties of composite samples, including the temperatures of the phase transitions, critically depended on concentration x which affects the composite microstructure. This behavior has been discussed in terms of microstructure analysis and such parameters as the grain size, porosity and density.
In this study, magnetic, structural, and hyperfine interactions of Sc3+ ion substituted Sr0.5Ba0.5Fe12O19 (Sr0.5Ba0.5ScxFe12−xO19 (x ≤ 0.1)) nanohexaferrites (Sc→SrBa NHFs) have synthesized through ...the sonochemical approach. The structure and morphology were studied by XRD, SEM, HR-TEM, and TEM along with EDX. XRD analysis confirmed the hexaferrite formation having crystallite within the range of 45 to 79 nm. Both TEM, HR-TEM, and SEM analyses proved the hexagonal morphology of all products. All products show ferrimagnetic hysteresis loops at both Ts. The evaluation of M(H) hysteresis loops indicated that the Ms (saturation magnetization), Mr (remanence), Hc (coercivity), and nB(Bohr magneton number) gradually decline with the incorporation of Sc3+ ion. Higher doping contents (x ≥ 0.08) revealed a considerable decline in Mr and Hc, showing significant changes from hard to soft magnetic behavior at higher contents. Mössbauer spectra show that Sc3+ ions are located at commonly octahedral (Oh) 4 f2 site. It was also determined that a small amount of Sc3+ occupied the 2b site. The microwave features of the products were determined by measuring S-parameters within the 2–10 GHz range. It was presumed that the energy losses resulting from reflection encompass both electrical and magnetic loss components. The average value of the reflection coefficient is − 14.48–14.24 dB. A noteworthy attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.
•Sr0.5Ba0.5ScxFe12−xO19 (x ≤ 0.1)) nanohexaferrites were synthesized via sonochemical approach.•XRD powder patterns confirmed the formation M-type hexaferrites.•All products show ferrimagnetic hysteresis loops at room and 10 K.•The average value of the reflection coefficient is − 14.48-14.24 dB.•A noteworthy attenuation of the reflected wave energy opens up broad prospects for practical applications as coatings for providing electromagnetic compatibility.
Developing heterostructure electrocatalysts is a possible route to discovering cost-effective and effectual catalysts for the oxygen evolution reaction. Er2O3–NiO nanoparticles have been created by ...successive drop cost method on nickel form. The produced Er2O3, NiO, and Er2O3–NiO electrocatalytic performances have been assessed, showing increased OER (185 mV@10 mA/cm2) activities compared to the single component. Furthermore, the three-electrode system (Er2O3–NiO) has remarkable OER properties, requiring only 1.37 V to reach 10 mA/cm2. Er2O3–NiO ‘s synergistic effect, which helps to cause lattice change into the fine structure of the crystal, activates the evolution of surface partial oxygen atoms and enables the lattice oxygen process, is principally responsible for its excellent catalytic performance and stability. This research contributes to a more profound knowledge of the synergistic interaction between various material oxides in heterostructure catalysts. It offers recommendations for future research and development of nanomaterials in sustainable energy conversion technologies.
Structural, electronic, optical, thermoelectric and magnetic properties of A3In2As4 and A5In2As6 (A = Eu and Sr) Zintl phase compounds in orthorhombic (Pnma and Pbam) phases are examined using ...density functional theory. Structure properties are an agreement with the experiment. Magnetic properties disclose the Non-magnetic nature of Sr3In2As4 and Sr5In2As6 and anti-ferromagnetic nature of Eu3In2As4 and Eu5In2As6 compounds.Electronic properties of Sr3In2As4, Sr5In2As6 and Eu3In2As4, Eu5In2As6 shows that all these compounds have narrow direct bandgap semiconductors at ᴦ and M symmetry. Electrical conductivity also gives the information about the semiconducting characteristic of these compounds. These compounds show that reduction in bandgap occurs through the substitution of Sr by Eu while increasing by going from local density approximation to modified Becke-Johnson potential and further reduce by spin orbit coupling effect. The outcome demonstrates that all compounds are optically dynamic in the infrared region, anisotropic and obstruct ultraviolet waves so these compounds are capable to use as shield for ultraviolet radiation and can be used as paramount applicant for optoelectronic devices. Owing to low thermal conductivity, high Seebeck coefficient, power factor and Figure of merit ranges from 0.39 to 1.2 at 800 K indicating that all compounds are active aspirants for thermoelectric applications.
•Structural, electronic, optical, thermoelectric and magnetic properties of the Zintl phase compounds are examined using DFT.•Good agreement DFT results and experiment was obtained.•Nonmagnetic nature of Sr3In2As4, Sr5In2As6 and antiferromagnetic nature of Eu3In2As4, Eu5In2As6 compounds was revealed.•It is shown that all substances are optically anisotropic, active in the IR-region and block UV-waves.•Such materials can be applied as shields for UV-radiation and paramount applicant for optoelectronic devices.
Tb-substituted Ni0.4Cu0.2Zn0.4TbxFe2−xO4 (0.0≤x≤0.10) nanospinel ferrites were formed by sonochemical technique. It was first time established correlation between chemical composition of the ...nanosized NiCuZn spinels and their structural, electrical and microwave properties. The structure of nanospinel ferrites (NSFs) was proved through XRD. Microstructural were analyzed from SEM. It was observed a non-linear dependence of the average grain size with Tb concentration. The conduction mechanism and dielectric function has been extensively studied as functions of frequency, temperature, and Tb ions substitution ratio using complex impedance spectroscopy. It is obvious to see that the substitutions ratio showed a substantial influence on dielectric features, while Tb ion substitution has little but notable effect on AC/DC conductivity change. From the Arrhenius plots, the activation energies for all substitution ratios were calculated. The reflection losses as a function frequency dependences of the were calculated from S-parameters data within 1–4.5GHz. The occurrences of the electromagnetic absorption in the frequency interval of 1.85–3.79GHz were observed. Non-linear behaviour of the amplitude–frequency features were verified as a function of the level of chemical substitution (x) with Tb ions concentration. It was found microstructural parameters correlates well with the main absorption characteristics. It was discussed the nature of the electromagnetic absorption for partially substituted nanospinels. The decline of the reflected electromagnetic radiations was explicated along with domain-boundary resonance, which well correlates with the microstructure data. The low dimensional magnetic oxides having the domain-boundary resonance have a role in nature of absorption.
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