High Magnetic Characteristics Research Articles

Unsteady slip flow of special second-grade fluid induced by Fe3O4 particles past a movable sheet with magnetic and nonlinear heat source/sink

Purpose Ferrofluids are aqueous or non-aqueous solutions with colloidal particles of iron oxide nanoparticles with high magnetic characteristics. Their magnetic characteristics enable them to be controlled and manipulated when ferrofluids are exposed to magnetic fields. This study aims to inspect the features of unsteady stagnation point flow (SPF) and heat flux from the surface by incorporating ferromagnetic particles through a special kind of second-grade fluid (SGF) across a movable sheet with a nonlinear heat source/sink and magnetic field effect. The mass suction/injection and stretching/shrinking boundary conditions are also inspected to calculate the fine points of the features of multiple solutions. Design/methodology/approach The leading equations that govern the ferrofluid flow are reduced to a group of ordinary differential equations by applying similarity variables. The converted equations are numerically solved through the bvp4c solver. Afterward, study and discussion are carried out to examine the different physical parameters of the characteristics of nanofluid flow and thermal properties. Findings Multiple solutions are revealed to happen for situations of unsteadiness, shrinking as well as stretching sheets. Greater suction slows the separation of the boundary layers and causes the critical values to expand. The region where the multiple solutions appear is observed to expand with increasing values of the magnetic, non-Newtonian and suction parameters. Moreover, the fluid velocity significantly uplifts while the temperature declines due to the suction parameter. Originality/value The novelty of the work is to deliberate the impact of mass suction/injection on the unsteady SPF through the special second-grade ferrofluids across a movable sheet with an erratic heat source/sink. The confirmed results provide a very good consistency with the accepted papers. Previous studies have not yet fully explored the entire analysis of the proposed model.

Enhancing trimethoprim pollutant removal from wastewater using magnetic metal-organic framework encapsulated with poly (itaconic acid)-grafted crosslinked chitosan composite sponge: Optimization through Box-Behnken design and thermodynamics of adsorption parameters

Trimethoprim (TMP), an antibiotic contaminant, can be effectively removed from water by using the innovative magnetic metal-organic framework (MOF) composite sponge Fe3O4@Rh-MOF@PIC, which is shown in this study. The composite is made up of magnetite (Fe3O4) nanoparticles and a rhodium MOF embedded in a poly(itaconic acid) grafted chitosan matrix. The structure and characteristics of the synthesized material were confirmed by thorough characterization employing SEM, FTIR, XPS, XRD, and BET techniques. Notably, the composite shows a high magnetic saturation of 64emug-1, which makes magnetic separation easier, according to vibrating sample magnetometry. Moreover, BET analysis revealed that the Fe3O4@Rh-MOF@PIC sponge had an incredibly high surface area of 1236.48m2/g. Its outstanding efficacy was confirmed by batch adsorption tests, which produced a maximum adsorption capacity of 391.9mg/g for the elimination of TMP. Due to its high porosity, magnetic characteristics, and superior trimethoprim uptake, this magnetic MOF composite sponge is a promising adsorbent for effective removal of antibiotics from contaminated water sources. An adsorption energy of 24.5kJ/mol was found by batch investigations on the Fe3O4@Rh-MOF@PIC composite sponge for trimethoprim (TMP) adsorption. The fact that this value was up 8kJ/mol suggests that the main mechanism controlling TMP absorption onto the sponge adsorbent is chemisorption. Chemisorption requires creating strong chemical interactions between adsorbate and adsorbent surface groups, unlike weaker physisorption. The magnetic composite sponge exhibited strong removal capabilities and high adsorption capacities for the antibiotic pollutant. The Fe3O4@Rh-MOF@PIC composite sponge also showed magnetism, which allowed for easy magnetic separation after adsorption. Over the course of 6cycles, it showed outstanding reusability, and XRD confirmed that its composition was stable. The high surface area MOF's pore filling, hydrogen bonding, π-π stacking, and electrostatic interactions were the main trimethoprim adsorption mechanisms. This magnetic composite is feasible and effective for removing antibiotics from water because of its separability, reusability, and synergistic adsorption mechanisms via electrostatics, H-bonding, and π-interactions. The adsorption results were optimized using Box Behnken-design (BBD).

Magnetized cubic zinc MOFs for efficient removal of hazardous cationic and anionic dyes in aqueous solutions.

A significant amount of dye runoff and aqueous waste are released from the manufacturing process of dyes with intense and permanent colors, which are undesirable from a cultural and ecological aspect. In this paper, we present a green, simple, low-effort, and energy-efficient method of creating magnetized cubic Zn-MOFs for the adsorption and elimination of various organic dyes. Magnetic iron oxide materials with a hierarchical structure were loaded and doped into cubic zinc metal-organic frameworks (MDLZ). High magnetic characteristics, chemical stability, minimal toxicity, and ease of removing various dyes from aqueous effluents are all exhibited by the developed MDLZ adsorbent. To assess MDLZ's capacity to adsorb organic dyes from an aqueous solution, organic dyes such as Crystal Violet (CV), Neutral Red (NR), and Congo Red (CR) were used as model materials. Many adsorption factors were examined, including temperature, pH, contact time, initial concentration, and adsorbent dosage. Under optimal elimination circumstances, MDLZ was utilized to evaluate the kinetic, thermodynamic, and isotherm models for the adsorption of CR, NR, and CV dyes. The adsorption capacity (q m) of the MDLZ adsorbent at 25 °C was 39.37 mg g-1 for CV, 239.81 mg g-1 for CR, and 321.54 mg g-1 for NR, which is significantly higher than those of other adsorbents reported. The magnetized nanocubes' large surface area and uniform micropores enabled them to eliminate a large number of organic dyes from wastewater effectively, and their strong adsorption capability persisted even after four reuse cycles. The microporous MLDZ adsorbent offers a simple and effective method for handling industrial effluents and filtration of water.

Three-dimensional network FeNi/C composites with excellent microwave-absorbing properties

In this paper, the carbon coated iron nickel nanoparticles were obtained by calcining PVP crosslinked iron nickel oxalate. The morphology, structural composition and microwave-absorbing (MA) properties of the composites were analyzed by various characterization methods. The results show that FeNi/C composites have excellent impedance matching characteristics and MA performance in multiple frequency by virtue of their microscopic network structure. At the same time, through the analysis of loss mechanism, we found that the material has high dielectric loss and magnetic loss characteristics. Under the joint action of various loss mechanisms such as interface polarization and eddy current loss, the material has a high reflection loss (RL) value at different frequency. At a thickness of 3 mm, the sample FNC12 has a minimum RL of − 52.99 dB at 3.6 GHz. The effective absorption bandwidth (EAB) (RL ≤ −10 dB) is 1.81 GHz.

Significant Improvement in Magnetic and Magnetoelectric Characteristics of (0.95 − x)Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3-xCoFe2O4 Ceramics

Multi-functional materials with high magnetic, electrical, and magnetoelectric characteristics play an important role in development of data storage devices. Herein, a multi-phase (0.95-x)Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3-xCoFe2O4 ceramics were prepared by two-stage mechanochemical activation technique. The objective of this study is to develop a multifunctional material with improved multiferroic characteristics. The structural analysis by Rietveld method shows the presence of heterogeneous structure without any impurity phase. The incorporation of CoFe2O4 (CFO) in 0.95Ba0.9Ca0.1TiO3-0.05Na0.5Bi0.5TiO3 (BCT-NBT) has resulted in significant improvement in magnetic and magnetoelectric characteristics without significantly hampering the electrical properties. The sample with x = 0.11 has shown high saturation magnetization of 8.26 emu/g along with moderately high magnetoelectric coefficient of 5.411 mV/cm.Oe. In addition to this, the energy storage performance of all the studied samples have also been investigated and the optimized sample x = 0.11 presents a large discharge energy density of 2.249 J/cm3 and moderately high energy efficiency of 63.8% at 388 kV/cm. The results obtained in the present work suggest a significant influence of CFO substitution on the magnetic characteristics of BCT-NBT ceramics, which subsequently indicate their potential applications in spintronics, magnetic memory storage, and electrical energy storage devices.

Synthesis and characterization of nearly monodisperse superparamagnetic (Fe3O4/Poly(methyl methacrylate))-SiO2 nanoparticles with raspberry-like morphology

Uniform and nearly monodisperse superparamagnetic Fe3O4/Poly(methyl methacrylate) (core)/SiO2 (shell) nanoparticles with raspberry-like morphology and high saturation magnetization were prepared in three different steps. At first, a facile, one-shot procedure to synthesize hydrophobic Fe3O4 nanoparticles through a modified co-precipitation method was implemented. Based on the hydrophobic interactions, these nanoparticles were used directly in a mini-emulsion polymerization resulting in encapsulation with PMMA. Then, for the covering with a silica shell, the surfaces of the Fe3O4/PMMA nanospheres were hydrolyzed in alkaline media and became hydrophilic through hydrolyzation. In the last step shell deposition of the Fe3O4/PMMA nanospheres through a modified Stober method was implemented. The surface morphology was investigated by scanning electron microscopy (SEM) and the core-shell structure and the prepared products’ diameters were measured by transmission electron microscopy (TEM); the size of the magnetic nanospheres was approximately 83 nm. Vibrating sample magnetometry (VSM) showed high magnetic saturation and superparamagnetic characteristics of the particles. Thermogravimetric analysis (TGA) was used as a supplementary test and, based on the mass loss at high temperature (600°C), the magnetic (Fe3O4) and non-magnetic content (PMMA) of the Fe3O4/PMMA nanospheres was measured as 81 and 19%, respectively. The narrow polydispersity of the nanospheres, measured by dynamic light scattering (DLS), was approximately 0.101. In every preparation step, the synthesized products were characterized by Fourier transform infrared (FTIR) spectroscopy. Our study focused on designing two-layered magnetic nanoparticles with drug delivery potential using two-layer encapsulation based on the hydrophobic and hydrophilic surface characteristics of the PMMA core and silica shells, respectively.

DC bias characteristic enhancement of the powder core by using densified submicron sized FeNi particles through spray pyrolysis

High-density submicron-sized FeNi particles prepared by a spray pyrolysis route exhibit high magnetic characteristics and enhance the powder core performance indicated by the improvement of the DC bias characteristic value.

Влияние атомов замещения и внедрения на магнитные свойства соединения Sm-=SUB=-2-=/SUB=-Fe-=SUB=-17-=/SUB=-

(Sm1-xRx)2Fe17 (R = Ho, Er) alloys with х = 0.1, 0.2 and 0.4 were prepared by induction melting under inert gas atmosphere. The structure and magnetic hysteresis properties of both the initial compositions and hydrides based on them are investigated. It was found that (Sm1-xRx)2Fe17Нy hydrides like the parent compounds have a rhombohedral Th2Zn17-type of crystal structure (sp.gr. R m). Hydrogenation results in a significant increase in the Curie temperature and saturation magnetization at room temperature. Compositions with potentially high magnetic characteristics have been determined.

Investigating the Possibility of Fabricating Pr2Fe14B/α-Fe Composite Materials by Oxidation of the Pr–Fe–B Alloy in a Fluidized-Bed Jet Mill

The results of studying the possibility of fabricating the Pr2Fe14B/α-Fe composite materials by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill are presented. It is shown that the use of the standard powder metallurgy technology supplemented by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill for rare-earth magnetically hard materials (MHMs) makes it possible to fabricate Pr2Fe14B/α-Fe composites with high magnetic characteristics. It is established that, when fabricating finely dispersed powders according to the proposed technology in the argon medium containing 0.2 vol % oxygen, residual magnetic induction (Br) occurs with an insignificant drop in the coercive force (jHc). This effect causes a 5% increase in the maximal energy product (BH)max. The almost complete oxidation of the highly praseodymium phase PrxFe occurs with a further increase in the oxygen concentration, which leads to an abrupt drop in the coercive force and, consequently, a decrease in (BH)max. The particles of the α-Fe phase formed due to the oxidation of the magnetic material are formed at the boundaries between the grains of the Pr2Fe14B phase. Herewith, the highest magnetic characteristics are implemented if the α-Fe particles are separated from the grains of the main magnetic phase by thin interlayers of nonmagnetic phases, which makes it possible to hold a high level of jHc for sintered MHM samples. Herewith, the optimal thickness of the α-Fe layers is 0.2–0.3 μm. The α-Fe layers formed with an oxygen content of 0.3 vol % turned out considerably thicker (from 0.8 to 1.1 μm), which leads to an almost 10% decrease in the coercive force of the samples and 3–7% decrease in other magnetic parameters (Br, (BH)max). Thus, when controlling the oxygen content in the working medium of the jet mill, we can vary the thickness of the interlayer of the forming α-Fe phase in the Pr2Fe14B/α-Fe composite material and control its magnetic parameters.

Effect of sintering temperature on magnetic hysteresis characteristics of powder alloy Fe-30Cr-8Co (wt.%)

In this work, we studied the effect of sintering temperature (1100 - 1400 °C) and thermomagnetic treatment (TMT) on the magnetic hysteresis characteristics of the Fe-30Cr-8 Co alloy, obtained by powder technology. It has been shown that at sintering temperatures of 1200 °C and below, it is possible to obtain materials with high magnetic characteristics that ensure their technical application. Properties exceed the characteristics of analogues obtained by casting technology. In the range 1200 - 1250 °C, the largest increase in the density of samples is observed with an increase in sintering temperature with a simultaneous increase in the values of magnetic characteristics. It was revealed that the total duration of heat treatment for 40-80 hours is sufficient for the formation of the necessary structure that determines the magnetic properties of the material. Long-term heat treatment (up to 160 hours) contributes to a higher level of magnetic properties.

RESEARCH OF MAGNETIC FIELD DISTRIBUTION IN THE WORKING AREA OF DISK SEPARATOR, TAKING INTO ACCOUNT AN INFLUENCE OF MATERIALS OF PERMANENT MAGNETS

Based on the results of a numerical-field analysis of the distribution of the magnetic force field in the working area of the disk magnetic separator, designed to clean bulk substances from ferromagnetic inclusions, the influence of the magnetic material of the poles of the magnetic system on the field distribution is determined. A consistent study of two magnetic systems assembled on the basis of magnetic materials of different classes is carried out. The finite element method implemented in the COMSOL Multiphysics software environment is used to calculate the distribution of magnetic induction in a disk magnetic separator with rare-earth and ferrite magnets. Due to the complexity of the spatial geometry of the force field in the working area of the disk magnetic separator, a three-dimensional model of the magnetic system is developed. A comparative analysis of the distribution of the magnetic force field in the working area of the disk separator with a highly coercive magnetic system and with a magnetic system based on ferrite blocks is carried out. As a result of the analysis, it is found that the indicators of the intensity and heterogeneity of the magnetic field for a highly coercive magnetic system significantly exceed the corresponding parameters of a ferrite magnetic system. It is proved that when choosing magnets for the magnetic system of a disk separator, preference should be given to highly coercive alloys, the magnetic properties of which significantly exceed the magnetic properties of ferrite magnets. To reduce the cost of the magnetic system of the disk separator, the use of a combined magnetic system assembled from magnetic materials of different classes is proposed. Studies of combined magnetic systems with various mass fractions of magnetic materials are done. The ratio of the mass fractions of magnets of various properties in the poles of the magnetic system is determined, at which sufficiently high magnetic characteristics are provided in the working area. It is shown that the presence of a ferrite fraction in the magnetic poles not only reduces the cost of the magnetic system of the separator, but also reduces the mass of the system. The tasks of further research are justified

Synthesis of Ni nanoparticles anchored on cellulose using different reducing agents and their applications towards reduction of 4-nitrophenol

In this study, the immobilization of Ni nanoparticles on microcrystalline cellulose using hydrazine hydrate and sodium borohydride was investigated. The prepared Ni NPs/MCC1 and Ni NPs/MCC2 nanocomposites were then characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The analyses exhibited that morphology of the Ni-nanocomposites and their magnetic characteristics were prominently depended to the applied reducing agents. This means that when hydrazine hydrate was used as a reducing agent, the formation of Ni NPs/MCC1 system with high crystallinity and magnetic characteristics was taken place. However, using sodium borohydride afforded the amorphous Ni NPs/MCC2 system with lowest magnetic property. At the next, catalytic activity of the prepared two nanostructured Ni-cellulose was investigated towards reduction of 4-nitrophenol to 4-aminophenol with the excess amounts of NaBH4 in water at room temperature. Both of the nanocomposites were easily separated from the reaction mixture using an external magnetic field or centrifugation. Reusability of two Ni-nanocomposites was studied for ten consecutive cycles without the significant loss of catalytic activity.

ВЛИЯНИЕ КОНЦЕНТРАЦИИ ЖЕЛЕЗА НА КРИСТАЛЛИЗАЦИЮ АМОРФНОГО СПЛАВА СИСТЕМЫ Co-Fe-B-Nb

In the modern world, technical devices are being constantly improved, creation of which requires materials with the best functional properties. Amorphous and nanocrystalline iron- and cobalt-based alloys are some of such materials. They have proved to be good in the fields of radio- and microelectronics, due to the fact they have high magnetic characteristics. It is also known that these properties can be improved by the formation of a partially crystalline structure is such alloys. However, such a structure cannot always be formed using a standard method of isothermal annealing; therefore, alloying components are added to the alloy composition to slow down the crystallization process. Different content of added components also affects the sequence of phase transformations during crystallization. As most of the properties are structure-dependent, the formed structure also determines the material characteristics. Therefore, establishment of the dependence of the formed structure in amorphous alloys after heat treatment is an important task of condensed matter physics. The crystallization of the amorphous alloys of Co-Fe-B-Nb system was studied by X-ray diffraction. The samples were crystallized using isothermal annealing of the alloys with different content of components under the same conditions. The dependence of the formed structure on the content of an alloying component is determined. It is shown that the formed structure significantly depends on the concentration of iron. With the iron content of 10 at.% and 16 at.%, the structure consists of cubic cobalt nanocrystals and a solid solution of iron in cobalt. With a decrease in the concentration to 5 at.%, the crystallization mechanism changes: crystallization begins with the precipitation of Co 23 B 6 boride crystals. The reasons for the effect of iron concentration in the alloy composition on crystallization are discussed.

Multifunctional Magnetic Materials of Organic Origin for Biomedical Applications: A Theoretical Study

AbstractSix different diradical systems based on azulene coupler and nitronyl nitroxide radical moieties have been studied theoretically. Among them, three ferromagnetic diradicals are chosen for further calculation to assess their usability in different biological applications such as two‐photon absorption photodynamic therapy (TPA‐PDT) and magnetic reso nance imaging contrast agents (MRICA). The TPA cross‐section values have been calcu lated to judge their efficiency as TPA‐PDT photosensitizing agents. Calculated values of TPA cross‐section lie in the range of commonly used photosensitizers for PDT. It is seen that the ferromagnetic diradicals can act as very good MRI contrast agents due to their high magnetic anisotropy characteristics. In connection to the magnetic anisotropy, the zero‐field splitting (ZFS) parameters are also computed using density functional theory (DFT) based methods. It is found that the proposed diradicals can show good relaxation behaviour and consequently act as efficient MRI contrast agents. Thus, one can anticipate the multifunctional biological activity of these diradicals.

Co/Ti-substituted SrM-based composite sheets: High frequency permeability and electromagnetic noise suppression above 6 GHz

Co/Ti-substituted Sr-based M-type hexagonal ferrite containing composite sheets are used for the demonstration of electromagnetic noise suppression at and above 6 GHz. Three different compositions (SrCoxTixFe12 − 2xO19 with x = 1.0, 1.2, and 1.4) and two different size groups with the average diameter of ∼10 µm and ∼1 µm have been studied to understand the effect of Co-Ti substitution level and size on the high frequency magnetic characteristics of SrM hexaferrites. A drop in coercivity from 285 Oe to 40 Oe and 710 Oe to 90 Oe was observed as the Co/Ti substitution level, x, increases from 1.0 to 1.4 in the case of 10-µm and 1-µm particles respectively. Complex permeability was measured by two methods – by microstrip probe, and by all-shielded and shorted microstrip line. Ferromagnetic resonance frequency drops from ∼20 GHz to ∼3 GHz as x increases from 1.0 to 1.4, while it decreases a little as the particle size decreases. Electromagnetic noise suppression was demonstrated by measuring the ratio of power loss in the magnetic element to the input power by placing it on top of a microstrip line. With a 500-µm thick composite sheet, electromagnetic noise suppression up to 20% was achieved.

Development of hyperbranched polymer encapsulated magnetic adsorbent (Fe3O4@SiO2–NH2-PAA) and its application for decontamination of heavy metal ions

The water dispersible magnetic adsorbent was fabricated by functionalization of magnetic nanoparticles (MNPs) with 3-aminopropyl trimethoxysilane (APTMS) and dendrimer-like polyamidoamine; the sorbent is named as Fe3O4@SiO2–NH2-PAA. The amine rich Fe3O4@SiO2–NH2-PAA adsorbent was further used in retrieval of heavy metal ions such as Cd(II), Co(II), Zn(II), Pb(II) and Cu(II) from the aqueous medium. Fabrication of Fe3O4@SiO2–NH2-PAA involves a two-step process: (i) surface initiation of MNPs by ligand exchange reaction and condensation of APTMS (Fe3O4@SiO2-NH2), (ii) surface functionalization of MNPs by controlled/living polymerization. Surface functional groups, crystallization characteristics, surface morphologies and magnetic properties of the adsorbent were analyzed by FT-IR, XRD, SEM, TEM, and VSM. The characterization outcomes showed that functionalization improved the oxygen and nitrogen atomic percentages of adsorbent resulting enriched adsorption. Sorption isotherm and kinetic models illustrated that sorption data better fitted to Langmuir isotherm model and pseudo-second order kinetic model. These results suggest that sorption process is monolayer and is chemical in nature. The order of sorption capacities (mgg−1) based on Langmuir isotherm model are: Pb(II) (108.82)>Cd(II) (100.81)>Co(II) (95.40)>Zn(II) (89.62)> Cu(II)(87.82). These findings suggest that as developed magnetic sorbent can be replaceable for traditional adsorbents due its high sorption performance, rapid kinetics, and magnetic separation characteristics.

Pyrolytic in situ magnetization of metal-organic framework MIL-100 for magnetic solid-phase extraction

In this study, we report a facile, environmental friendly fabrication of a type of magnetic metal-organic framework (MOF) MIL-100 that can be used for magnetic solid-phase extraction (MSPE). The magnetic MOF composites were fabricated using in situ calcination method. The as-synthesized materials exhibited both high porosity and magnetic characteristics. They used for the MSPE of polycyclic aromatic hydrocarbons (PAHs) from water samples. Such MOF-based magnetic solid-phase extraction in combination with gas chromatography equipped with a flame ionization detector (GC-FID), exhibited wide linearity (0.02–250μgL−1), low detection limits (4.6-8.9ngL−1), and high enrichment factors (452–907) for PAHs. The relative standard deviations (RSDs) for intra- and inter-day extractions of PAHs were ranging from 1.7% to 9.8% and 3.8% to 9.2%, respectively. The recoveries for spiked PAHs (1μgL−1) in water samples were in the range of 88.5% to 106.6%. The results showed that the special anion-π orbital (electron donor-acceptor) interaction and π-π stacking between magnetic MIL-100 and PAHs play an important role in the adsorption of PAHs.

Deep seismic structure of the northeastern South China Sea: Origin of a high‐velocity layer in the lower crust

AbstractWe present a 2‐D seismic tomographic image of the crustal structure along the OBS2012 profile, which delineates the Moho morphology and magmatic features of the northeastern South China Sea margin. The image was created by forward modeling (RayInvr) and traveltime tomographic inversion (Tomo2D). Overall, the continental crust thins seaward from ~27 km to ~21 km within the continental shelf across the Zhu I Depression and Dongsha Rise, with slight local thickening beneath the Dongsha Rise accompanying the increase in the Moho depth. The Dongsha Rise is also characterized by ~4–7 km thick high‐velocity layer (HVL) (~7.0–7.6 km/s) in the lower crust and exhibits a relatively high velocity (~5.5–6.4 km/s) in the upper crust with a velocity gradient lower than those of the Zhu I Depression and Tainan Basin. Across the continental slope and continent‐ocean transition (COT), which contain the Tainan Basin, the crust sharply thins from 20 km to 10 km seaward and a ~2–3 km thick HVL is imaged in the lower crust. We observed that volcanoes are located only within the COT, but none exist in the continental shelf; the Dongsha Rise exhibits a high magnetic anomaly zone and different geochemical characteristics from the COT. Based on those observations, we conclude that the HVL underlying the COT is probably extension related resulting from the decompression melting in the Cenozoic, whereas the HVL beneath the Dongsha Rise is probably arc related and associated with the subduction of the paleo‐Pacific plate. These findings are inconsistent with those of some previous studies.

Behavior of magnetic characteristics in promising nitrogen-containing steels upon elastoplastic deformation

We report on the studied influence of the applied normal and tangential stresses, as well as their combined effect on the structure, phase composition, and magnetic properties of three high-nitrogen steels (HNS). Two of the studied steels in the initial state had an austenitic structure and were diamagnetic. The third steel, according to the data of the X-ray diffraction and metallographic analysis, contained 7% δ-ferrite in its composition, which specifies its ferromagnetic properties. The nitrogen steels studied in this work have demonstrated the stability of the phase composition, as well as of the magnetic properties at various loading conditions, and, thus, can be used in the production of articles and elements of structures that are required to exhibit low magnetization and high stable magnetic characteristics under an applied force. Parameters that can be used as the informative ones when estimating changes that occur upon the production and exploitation of articles and elements made of HNSs with small contents of δ ferrite have been determined.

Synthesis and Study of the New Class of Magnetic Bioceramics for Biomedical Applications: Mossbauer Studies

Magnetic bioceramics based on hydroxyapatite Ca5(PO4)3OH and particles of the M-type hexagonal (barium or calcium) ferrite (taken in proportions 5, 10, 20, 25, 40 and 50 wt % of M-ferrite) with a high bioactivity and magnetic characteristics providing hyperthermal treatment of oncology diseases has been developed and studied. The phase composition, microstructure, and magnetic properties of the synthesized bioceramics have been determined by using electron diffraction patterns, electron microscope micrograms and Mossbauer spectroscopy. It has been shown that the synthesized biomaterial consists of the biocompatible matrix with the apatite structure into which particles of hexagonal ferrite are incorporated. The Mossbauer spectra for all the samples clearly indicates that the particles of hexagonal ferrite are in the ferromagnetic state and small part of particles in paramagnetic state. The magnetic parameters of the synthesized ceramics are substantially higher than those of the bioglass ceramics modified by iron oxides that have been used in medicine, which suggests good potential and effectiveness of application of the created ceramics for medical purposes. Thus, a new class of magnetic bioceramics combining hydroxyapatite Ca5(PO4)3OH, which exhibits good properties in biocompatibility and bioactivity, with particles of the M-type hexagonal ferrite, which possess high magnetic characteristics, has been created.