Synthesis and characterization of nanoscale composite particles formed by 2D layers of Cu-Fe sulfide and Mg-based hydroxide

We introduce here a multifunctional material composed of alternating atomic sulfide sheets close to CuFeS2 and Mg-based hydroxide ones (valleriite), which are assembled due to their electric charges of opposite sign. Valleriite particles of 50-200 nm in the lateral size and 10-20 nm thick were synthesized via a simple hydrothermal pathway using various concentrations of precursors and dopants, and examined with XRD, TEM, EDS, X-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy (REELS), Mössbauer, Raman and UV-vis-NIR spectroscopies, magnetic, dynamic light scattering, zeta potential measurements. The electronic, magnetic and optical characteristics are found to be critically dependent of the charge (electron density) at the narrow-gap sulfide layers containing Cu+ and Fe3+ cations, and can be tuned via the composition of hydroxide part. Particularly, substitution of Mg2+ with Al3+ increases the negative charge of the hydroxide layers and reduces the content of Fe3+-OH centers (10-45% of total iron); the effects of Cr and Co dopants entering both layers are more complicated. Mössbauer doublets of paramagnetic Fe3+ detected at room temperature transform to several Zeeman sextets at 4.2 K; the hyperfine fields up to 500 kOe and complex magnetic behavior, but not pure paramagnetism or antiferromagnetism, were observed for valleriites with the higher positive charge of the sulfide sheets, probably due to the depopulation of the minority-spin 3d states of S-bonded Fe3+ ions. Aqueous colloids of valleriite show optical absorption at 500 - 750 nm, which, along with the peaks at the same energies in REELS, may arise due to quasi-static dielectric resonance involving the vacant Fe 3d band and being dependent on the composition of both layers too. These and other findings call attention to the of valleriites as a new rich family of 2D materials for a variety of potential applications.

Effects of interfacial Dzyaloshinskii–Moriya interaction on magnetic dynamics

In the “Beyond Moore” era, the information device is expected to exhibit advantages including small sizes, high processing speed, and low power and dissipation. The novel magnetic information device with these advantages is made of heavy metal(HM)/ferromagnet (FM) composite. Owing to the asymmetric structure, the anisotropic exchange coupling named the interfacial Dzyaloshinskii–Moriya interaction (iDMI) is generated at the HM/FM interface. This iDMI influences the magnetic dynamics including ferromagnetic resonance (FMR), spin wave, and the motion of chiral DWs. These magnetic dynamic behaviors are the bases of the functions of novel magnetic information devices. Therefore, the influence of iDMI on the magnetic dynamics has attracted wide attention in recent years. In this topical review, we give a detailed introduction and discussion about recent investigation on the iDMI-relevant magnetic dynamics of the HM/FM bilayer system. This review consists of five sections: (1). the introduction about the background, the basic theory of magnetic dynamics and DMI; (2). the review about the effect of iDMI on the propagation of spin wave. Owing to the iDMI, the dispersion relationship of spin wave is asymmetric. This not only offers a precise method for measuring the iDMI constant, but also gives rise to potential application for novel magnonic devices. (3). the review about the effect of iDMI on the FMR. Unique iDMI-relevant mode was observed in the FMR spectra owing to the nonparallel alignment of magnetic moments. (4). the review about the motion of DWs with chiral structure due to iDMI. The iDMI plays a fundamental role in the high velocity of the chiral DWs. Meanwhile, the iDMI results in the tilting of DW plane, and the mechanism has been widely investigated. The tilting of the DW plane may be depressed by the interlayer exchange coupling. (5). finally, we summarize the review and give an outlook.

Mechanisms of structural-phase transformations during crystallization of solder melt under conditions of magnetic-dynamic influences for carbide tools

The processes of melt formation were studied by methods of optical and electron scanning microscopy. These processes occur during induction brazing of a hard alloy to a steel holder and contact interaction of low-melting (copper-zinc system alloy) and refractory (iron-nickel) components of the solders. It is shown that the effect of a thermal and magnetic-dynamic high-frequency electromagnetic field on the components of the composite solder is how a high-strength solder joint is formed. The structure is forming by disperse hardening mechanism. The research of the contact interaction process for low-melting and high-melting components of solders during the soldering process of the tool showed that the formation of solder in brazed seams occurs through a number of stages and this does not lead to the formation of microstructures that are characteristic of alloys based on copper-iron-phosphorus, copper-zinc-nickel and copper-zinc-iron. Thus, the use of composite solders can reduce the soldering temperature by 40-50 K and increase the concentration of alloying species in the solder and change its structure. These advantages of composite solders reduce the thermal impact on contact materials, increase the strength of the weld and allow you to control the thickness of the brazed weld, and this is important when soldering hard alloys of WC-TiC (TaC) systems. High initial dissolution rates of nickel particles in the copper-zinc melt and the solubility of copper, zinc in nickel lead to the formation in the melt of quasi-liquid particles of the nickel alloy. When the melt is cooled, particles other than the surrounding alloy composition are formed. They are morphologically related to the grain structure of the solder. The formed alloy (solder) has the structure of a composite material in which the metal particles are enriched in nickel, and have the role of a reinforcing element.

Synthesis and characterization of nanoscale composite particles formed by 2D layers of Cu-Fe sulfide and Mg-based hydroxide

Two-dimensional phenomena are attracting enormous interest at present and the search for novel 2D materials is very challenging. We propose here the layered material valleriite composed of altering atomic sheets of Cu-Fe sulfide and Mg-based hydroxide synthesized via a simple hydrothermal pathway as particles of 50-200 nm in the lateral size and 10-20 nm thick. The solid products and aqueous colloids prepared with various precursor ratios were examined using XRD, TEM, EDS, X-ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), Raman, Mössbauer, UV-vis-NIR spectroscopies, magnetic, dynamic light scattering, zeta potential measurements. The material properties are largely determined by the narrow-gap (less than 0.5 eV) sulfide layers containing Cu+ and Fe3+ cations, monosulfide and minor polysulfide anions but are strongly affected by the hydroxide counterparts. Particularly, Fe distribution between sulfide (55-90%) and magnesium hydroxide layers is controlled through insertion of Al into the hydroxide part and by Cr and Co dopants entering both layers. Room-temperature Mössbauer signals of paramagnetic Fe3+ transformed to several Zeeman sextets with hyperfine magnetic fields up to 500 kOe in the sulfide layers at 4 K. Paramagnetic or more complicated characters were observed for valleriites with higher and lower Fe concentrations in hydroxide sheets, respectively. Valleriite colloids showed negative zeta potentials, suggesting negative electric charging of the hydroxide sheets, and optical absorption maxima between 500 nm and 700 nm, also depended on the Fe distribution. The last features observed also in the REELS spectra may be due to localized surface plasmon or, more likely, quasi-static dielectric resonance. The tunable composition, electronic, magnetic, optic and surface properties highlight valleriites as a rich platform for novel 2D composites promising for numerous applications.

Technological potentialities of parts machining in devices with rotating electromagnetic field and outlooks in their use

There are presented application fields of devices with the rotating electromagnetic field. The essence and physical effects stipulating for their use in the technology of manufacturing machinery, coating application, and also metal production waste processing during the processing with ferromagnetic indenters are shown. There are shown the results of experimental investigations depicting technological potentialities of magnetic-dynamic processing in finish-strengthening.

Utilizing Iron for Targeted Lipid Peroxidation as Anticancer Option of Integrative Biomedicine: A Short Review of Nanosystems Containing Iron

Traditional concepts of life sciences consider oxidative stress as a fundamental process of aging and various diseases including cancer, whereas traditional medicine recommends dietary intake of iron to support physiological functions of the organism. However, due to its strong pro-oxidative capacity, if not controlled well, iron can trigger harmful oxidative stress manifested eventually by toxic chain reactions of lipid peroxidation. Such effects of iron are considered to be major disadvantages of uncontrolled iron usage, although ferroptosis seems to be an important defense mechanism attenuating cancer development. Therefore, a variety of iron-containing nanoparticles were developed for experimental radio-, chemo-, and photodynamic as well as magnetic dynamic nanosystems that alter redox homeostasis in cancer cells. Moreover, studies carried over recent decades have revealed that even the end products of lipid peroxidation, represented by 4-hydroxynonenal (4-HNE), could have desirable effects even acting as kinds of selective anticancer substances produced by non-malignant cells for defense again invading cancer. Therefore, advanced nanotechnologies should be developed for using iron to trigger targeted lipid peroxidation as an anticancer option of integrative biomedicine.