Spherical Iron Research Articles

Thermal Magnetic Effect of Needle-Shaped Gamma-Iron Oxide Nanoparticles in Low-Frequency Fields

The hyperthermic effect of spherical and needle-shaped iron oxide nanoparticles coated with oleic and citric acids in a low-frequency alternating magnetic field is studied. Measurements of their magnetic properties reveal the superparamagnetic properties of nanomagnetite and the presence of the hysteresis loop in maghemite. The heat release of dispersions is measured in the low-frequency range (1.0–5.2 kHz) and magnetic fields (8–31 mT). The results are used to calculate a quantitative characteristic, the specific absorption coefficient, and its dependence on the frequency and field strength. A substantial heat-release effect in low-frequency fields for needle-shaped magnetic particles is observed. It is shown that heat release in an aqueous medium is stronger than one in propylene glycol. Suspensions of such particles are promising for application in treating oncological diseases by means of magnetic hyperthermia.

Are hypervelocity impacts able to produce chondrule-like ejecta?

Chondrules are one of the major components of primitive meteorites. Their sphericity indicates they formed as molten fragments or droplets but conditions and mechanisms of chondrule formation remain unknown. A possible scenario is their formation during hypervelocity impacts and ejections. To challenge this idea, we prepared an experiment that reproduces analogous of iron metal -rich chondrules by impact between a glassy silicate projectile and a metallic steel target. The hypervelocity experiment setting allowed an impact velocity of 5 km/s, and was also designed to collect the ejecta. A scanning electron microscopy survey shows that silicate ejecta share several similarities with chondrules. They formed from a population of small melt fragments whose size distribution has the same shape as the size distribution of chondrules, with a shift in size: ejecta are about one order of magnitude smaller than typical chondrules (log(dchondrules/dejecta) = 1.3−0.7+0.5). We attribute this difference in size to the large discrepancy in the size of the impactors (only small 3 mm particle in our experiment versus km-scale planetesimal expected in an impact forming scenario for chondrules). The silicate ejecta formed in the ejecta plume contains numerous small size spherical iron metal beads. Such beads are also observed in numerous chondrules of CO chondrites specifically presented here but also documented in L and LL ordinary chondrites. Size distributions of metal beads in ejecta and chondrules of a carbonaceous chondrite used as reference material (Yamato 81020 CO) display a same shape but with a size shift, quite similar to the one observed between the ejecta droplets and the chondrules: the diameter of metal beads in ejecta is about one order of magnitude smaller than the diameter of the ejecta themselves (log(dejecta/dmetal beads in ejecta) = 1.2−0.8+0.9), and the diameter of metal beads in chondrules is about one order of magnitude smaller than the diameter of the chondrules themselves (log(dchondrules/dmetal beads in chondrules) = 1.4−1.0+0.6). We attribute this size differences to the blast dynamics: for a same velocity and surface tension, fragments of silicate liquid will be stable when iron liquid fragments of similar size will be separated into smaller droplets. In our experiment, the biggest iron metal beads (∼7 μm) are within the mean size range of silicate ejecta and can be considered as analogous of the rare large rounded metallic grains (nearly the same size as chondrules) documented in CB chondrites. The textural analogies exposed here provide support for a production of chondrules by impact.

Simulation of deformation and fracture processes in nanocomposites

The paper studies the processes of deformation and fracture in nanocomposites. The study was curry out by the method of mathematical modeling. The behavior of the nanosystem was described by the molecular dynamics apparatus. A modified immersed atom method was used as a potential. Demonstrated theoretical approaches to the study of the mechanical properties of nanocosposites and the processes of their destruction. Formulas for calculating the stress, strain tensors and displacement veare given. To maintain a constant temperature in the nanosystem, a Nose – Hoover thermostat was used. The destruction of nanocomposites was considered in the process of tension and shear deformation. Pure aluminum, a composite with an aluminum matrix and a filler in the form of spherical iron particles, and a composite with an aluminum matrix and a filler in the form of a cylindrical iron fiber were used as samples. After the filler was introduced into the nanocomposite, the sample was relaxed to ensure its more stable state. The simulation allowed us to establish the basic laws of changes in the atomic structure of the matrix and nanocomposite fillers during deformation and fracture. It is shown that the processes of deformation and destruction of nanocomposites substantially depend both on the structure and types of loading of the material. The results of the research can be used to study the processes of deformation of nanocomposite materials with promising functional properties.

Nanoparticle's size, surfactant and concentration effects on stability and isotropic-nematic transition in ferronematic liquid crystal

Isotropic-nematic phase transition in composites based on 4-cyano-4-hexylbiphenyl (6CB) liquid crystal and spherical magnetic iron oxide nanoparticles with various nanoparticle sizes and various concentrations were investigated. The iron oxide nanoparticles were covered by oleic acid surfactant that prevents their aggregation. Dependences of the phase transition temperature shift on the nanoparticle size and the nanoparticle volume fraction were acquired by optical measurements, differential scanning calorimetry measurements and capacitance measurements. TEM and SEM examination showed a nonuniform thickness of oleic acid layers for different nanoparticle sizes. At the same nanoparticle volume fraction, therefore, the volume fraction of oleic acid varies with nanoparticle size. Although oleic acid surfactant prevents the magnetic aggregation, it modifies isotropic-nematic phase transition temperature significantly. The theoretical considerations of oleic acid provided in the present paper give the interpretation of obtained experimental results.

Numerical simulation of welding fume lung dosimetry

Exposures to airborne particles and toxic gases generated by welding fabrication activities will potentially lead to various diseases. Accurate information on the transport and deposition of such aerosols in the respiratory system is critically needed for precise health risk assessments. To address the data demand mentioned above, a multiscale computational fluid-particle dynamics (CFPD) model was developed in this study. Specifically, a virtual fabrication shop was integrated with a virtual human in the numerical model to evaluate the effects of ventilation condition, particle size, and gas species on the lung uptakes of those welding fume particles and gases. Welding fume particle and gases transmission, transport, and deposition have been simulated and analyzed starting from the emission source to the subject-specific human respiratory system via oral inhalation. Spherical iron particles with diameters of 100, 190, and 830 nm were simulated. The transport and absorption of NOx and CO were predicted too. Steady-state inhalation with 11.87 L/min was applied with two different air filter ventilation conditions. The numerical results indicate that the ventilation condition can significantly influence welding gas transport and deposition. The pulmonary gas absorption rate is much higher at poor ventilation conditions. The air-tissue absorption coefficient is another crucial factor that can impact pulmonary gas absorption. The total particle deposition fractions (TDFs) from mouth/nose to generation 6 (G6) are less than 18.0%, and particles mostly deposit in the oral cavity. Regional and local particle deposition data demonstrate that particles tend to enter the two upper lobes more than the other three lobes. In summary, this study paves the way to build a personalized in silico tool based on CFPD models for noninvasive precise health risk assessments associated with different welding activities.

Effect of Spherical Particle Size on the Electrochemical Properties of Lithium Iron Phosphate

The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different particle size distributions controlled with ball time of precursor slurry was prepared by spray drying method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), charge and discharge measurements and EIS. The electrochemical performances of the sample materials were measured by coin cells and 14500 batteries. XRD shows that the spherical lithium iron phosphate with different particle sizes all have good crystal structure due to the perfect mixing of the raw materials and rapid drying. The lithium iron phosphate microsphere with different particle sizes self-assembled with submicron primary particles has a core-shell structure. The longer ball time the precursors are, the smaller the active material particles are prepared. The electrode material with 6 h ball time of precursor slurry has the best physical properties and the processability. The composite has a uniform particle size and higher tap density of 1.46 g/cm3, which delivers a discharge capacity of 167.6 mAh/g at a discharge rate of 0.5 C. The results were confirmed by the 14 500 mA·h cylindrical batteries, which delivers a discharge capacity of 579 mAh at 0.5 C. And low-temperature performance with capacity of 458.5 mA h at −20 °C under a discharge rate of 0.5 C is the 79.2% of the same discharge rate at 25 °C. Otherwise, the 14500 batteries also exhibit excellent cycling performance and the capacity maintains 93% after 2 000 cycles.

Mesoporous electromagnetic composite particles: Electric current responsive release of biologically active molecules and antibacterial properties

Electric current responsive magnetic composite particles are prepared in three steps. In the first step, spherical and mesoporous submicrometer-sized magnetic iron oxide (Fe3O4) core particles are prepared by solvothermal method. Then magnetic Fe3O4 particles are functionalized with amine groups using glycine, where the COO- group of glycine formed a bridging bidentate interaction with the hydroxyl groups on Fe3O4 particle surface. Finally polyaniline (PAni) is grafted onto the functional Fe3O4 surface via in situ seeded chemical oxidative polymerization of aniline. The average size of Fe3O4/PAni composite particles is 418.82 nm with mesoporous surface structure. Electron microscopic images confirmed that PAni pockets are localized on the surface of Fe3O4 core particles. The surface composition is further confirmed by Fourier transform IR (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimety (TG) analyses. Fe3O4/PAni composite particles possessed strong paramagnetic property (47.77 emu g−1). The electrical conductivity of Fe3O4/PAni composite particles (1.46 × 10-4 S cm−1) remained in the same order of magnitude as that of reference PAni particles (3.42 × 10-4 S cm−1). The release behavior of biologically active molecules such as trypsin (TR), albumin (AL) and p-acetamido phenol (pAP) is studied using low intensity electric current as stimuli to prevent degradation. Depending on the nature, up to ˜ 33–88% of adsorbed biomolecules/drug are released from the electromagnetic Fe3O4/PAni composite particles. Compared to Fe3O4 particles, Fe3O4/PAni composite particles exhibited moderate antibacterial property.

Magnetoferritin: Process, Prospects, and Their Biomedical Applications.

Ferritin is a spherical iron storage protein composed of 24 subunits and an iron core. Using biomimetic mineralization, magnetic iron oxide can be synthesized in the cavity of ferritin to form magnetoferritin (MFt). MFt, also known as a superparamagnetic protein, is a novel magnetic nanomaterial with good biocompatibility and flexibility for biomedical applications. Recently, it has been demonstrated that MFt had tumor targetability and a peroxidase-like catalytic activity. Thus, MFt, with its many unique properties, provides a powerful platform for tumor diagnosis and therapy. In this review, we discuss the biomimetic synthesis and biomedical applications of MFt.

In Situ Grafting Hydrophilic Polymeric Layer for Stable Drag Reduction.

Developing drag reduction techniques has attracted great attention because of their need in practical applications. However, many of the proposed strategies exhibit some inevitable limitations, especially for long period of adhibition. In this work, the dynamic but stable drag reduction effect of superhydrophilic hydrogel-coated iron sphere falling freely in a cylindrical water tank was investigated. The absolute instantaneous velocities and displacements of either the hydrogel-encapsulated or unmodified iron sphere falling freely in water were monitored via a high-speed video. It was revealed that, in the range of Reynolds number from 104 to 106, the optimized hydrogel-coated iron sphere with uniform stability could reduce the resistance by up to 40%, which was mainly due to the boundary slip of water and the delayed boundary separation that resulted from the coated hydrogel. Besides, the deliberate experiments and analysis further indicated that the superhydrophilic hydrogel layer accompanied by the emergence of the drag crisis has largely effected the distribution of flow field at the boundary around the sphere. More importantly, the drag reduction behavior based on the proposed method was thermodynamically stable and resistant to external stimulus, including fluidic oscillator and hydrodynamic pressure. The effective long-term drag reduction performance of the hydrophilic substrate can be expected, correspondingly, and also provides a novel preliminary protocol and avenues for the development of durable drag reduction technologies.

Numerical and experimental studies of the effect of iron ore particle shape on repose angle and porosity of a heap

Spherical (pellet), cylindrical and conical iron ore particles were produced to study the effect of particle shape on repose angle and bottom porosity distribution of a heap formed by natural piling. The effects of coefficient of static friction, rolling friction and restitution and particle shape on the repose angle and porosity of the pile for three particle shapes were numerically studied by the discrete element method. The results show that the primary influential factors on repose angle and porosity is the static friction, followed by particle shape. The repose angle of piles of spheres is smaller than that of non-spheres, but there is little difference in repose angle between non-spherical particles. The value of the porosity in the three kinds of piles decreases from spheres to cones to cylinders, but all show a V-shape distribution, with lowest porosity along the axis through the apex. The porosity shows a minimum value when the sphericity is about 0.85. Piles of cylindrical particles show the smallest porosity due to parallel planes of the particle shape.

Magnetodielectric Response of Soft Magnetoactive Elastomers: Effects of Filler Concentration and Measurement Frequency.

The magnetodielectric response of magnetoactive elastomers (MAEs) in its dependence on filler concentration, magnetic field, and test frequency is studied experimentally. MAEs are synthesized on the basis of a silicone matrix filled with spherical carbonyl iron particles characterized by a mean diameter of 4.5 µm. The concentration of the magnetic filler within composite materials is equal to 70, 75, and 80 mass%. The effective lossless permittivity ε′ as well as the dielectric loss tanδ grow significantly when the magnetic field increases. The permittivity increases and the dielectric loss decreases with increasing filler concentration. In the measurement frequency range between 1 kHz and 200 kHz, the frequency hardly affects the values of ε′ and tanδ in the absence of a magnetic field. However, both parameters decrease considerably with the growing frequency in a constant magnetic field. The more strongly the magnetic field is applied, the larger the change in permittivity and loss tangent at the same test frequency is observed. An equivalent circuit formulation qualitatively describes the main tendencies of the magnetodielectric response.

Investigation of Neutron Cross Section for Iron in the ENDF Library with Pulsed Sphere Measurements

This work investigates the quality of the ENDF 56Fe cross-section libraries for describing the transport of fast neutrons in iron. We have used the D(d,n)3He reaction with a pulsed 7-MeV deuteron beam energy as a neutron source and analyzed the neutrons transmitted through two natural iron spheres of thicknesses 3 and 8 cm. The experimental neutron time-of-flight transmitted spectra for various angles are compared with MCNP simulations. Our result indicates the possibility of an underestimation of the nonelastic cross section and an overestimation of the elastic cross section for 56Fe in the ENDF/B-VII.1 library for the neutron energy range of 7.2 to 10.2 MeV. Our result agrees qualitatively with the Ramsauer model and optical model calculations. This discrepancy in the library cross section might lead to an underestimation/overestimation of material damage in nuclear reactor calculations. A newer evaluation, ENDF/B-VIII.0, was released subsequent to the completion of the majority of this project. The new evaluation has a decreased elastic cross section and an increased inelastic cross section for 56Fe in our energy range of interest, which agrees qualitatively with our result.

Modeling of Ferrous Metal Diffusion in Liquid Lead Using Molecular Dynamics Simulation

Modeling of Iron metal diffusion in liquid lead using molecular dynamics simulation has been done. Molecular dynamics simulations are used to predict the value of physical quantities that we want to know based on the designed material model and on the input simulation data. In this research, effect of different geometry of material models was observed to know the diffusion coefficient. The material system was iron (Fe) in liquid lead (Pb). The material models is designed using Packmol software to get the initial configuration of atom's arrangement by inputting the material's characteristics such as mass, density, volume, number of atoms. This work examines the diffusion coefficient of iron in molten lead metal with the geometric shape of the simulation system in the form of iron in molten metal for various simulation models of boxes in a box, balls in a box and balls in balls. To design simulated geometric shapes we use the Packmol program. To calculate the diffusion coefficient we use the molecular dynamics simulation method. To find out which geometry is suitable, we compare the diffusion coefficient of the simulation results with existing references. The diffusion coefficient value of the spherical iron (Fe) system in the spherical liquid lead (Pb) has the best value compared to the other two forms with an accuracy rate of 99.94% because it is influenced by the even distribution of atoms in each part.

Structural characterization of polysaccharide-coated iron oxide nanoparticles produced by Staphylococcus warneri, isolated from a thermal spring.

The biocompatible-coated iron oxide nanoparticles (IONs) have attracted a great interest because of their various applications in biological science and medicine. In most cases, the toxic effect of naked iron oxide nanoparticles is completely cleared by adding a biocompatible coating, such as polysaccharides, polyethylene glycol (PEG), or biosynthesis of biocompatible-coated IONs using microorganisms such as bacteria. In the present study, polysaccharide-coated iron oxide nanoparticles were produced by a strain of Staphylococcus warneri isolated from a thermal spring. For identification of the isolated bacterium, 16S rRNA gene sequencing was done. Characterization of the nanoparticles was performed for the first time, using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), X-ray crystallography (XRD), Fourier-transform infrared (FTIR) spectroscopy, vibrating sample magnetometer (VSM), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results indicated that the spherical iron oxide nanoparticles were coated by a polysaccharide (13.6%), which provided a large negative charge of -91 mV and very low saturation magnetization of around 0.28 emu/g. The result of MTT assay on MOLT-4 cell lines showed that the percentage of viability was between 95.6% and 68.9% in the 10-100 µM of nanoparticle concentrations with a high IC 50 value, which makes it appropriate for biomedical applications such as cancer therapy.

Preparation of Spherical FePO4 by Chemical Co-precipitation Combined with Spray-Drying

Well-shaped spherical agglomerates of FePO4 particles were prepared by a novel method: chemical co-precipitation combined with spray-drying. Tap density analysis, Brunauer–Emmett–Teller analysis, characterizations of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy confirmed that the micron-sized spherical agglomerates with high specific surface area and high tap density were composed of the uniform nano-sized particles. The effects of pH and reaction time on the morphology of the FePO4 particles were investigated by experimental and theoretical analyses. The analyses revealed that amorphous FePO4 was responsible for forming a well-shaped spherical agglomerate, and the ideal spherical particles were obtained at pH 3. The reaction time also played a significant role in controlling the size and surface morphology of the FePO4 particles, and smooth spherical FePO4 particles were obtained at a reaction time of 6 h. By this novel method, poly-porous spherical iron phosphate particles were prepared, which can be used with high efficiency in some special fields, especially as a precursor for synthesizing LiFePO4 and catalysts.

The Effects of Heat Treatment on the Tensile Properties of Camshaft made of GGG70 Series Spherical Graphite Cast Iron

The Effects of Heat Treatment on the Tensile Properties of Camshaft made of GGG70 Series Spherical Graphite Cast Iron

Effects of particle size on electromagnetic properties of spherical carbonyl iron

Classification experiments using the spherical carbonyl iron (SCI) with particle size ranged from 1 to 7 µm were conducted by an air classifier. The electromagnetic properties of the SCI with different particle size were investigated in the frequency range of 2–18 GHz. The effects of particle size on the microwave absorption properties of the SCI were discussed on the results of scanning electronic microscopy, vibrating sample magnetometer, and frequency dependence of complex permittivity and permeability. The results show that the larger particle size leads to higher permittivity and lower permeability. The dielectric loss is attributed to the Debye dipolar polarization, while the magnetic loss arises from natural resonance and blocking resonance between superparamagnetism and ferromagnetism. The SCI with average particle size of 1.49 µm exhibits the optimal microwave absorption performance. A minimum reflection loss (RL) of − 50.8 dB is achieved at 15.6 GHz with a thickness of 1.27 mm, along with the corresponding bandwidth of RL less than − 10 dB (90% absorption) covering 7.04 GHz. Notably, the SCI with smaller particle size (about 1–3 µm) show superior microwave absorption properties at higher frequency range and thinner thickness than the corresponding larger ones (about 5 µm), which is mainly attributed to the improved impedance matching.

Dynamics and stability of an iron drop falling in a magma ocean

The latest stages of planetary accretion involved large impacts between differentiated bodies, hence large scale melting events. Consequently, the iron brought by the impactors sank within a deep magma ocean, before reaching the proto-core. Yet the fluid dynamics of this process remains poorly known. Here, we report numerical simulations of the sinking dynamics of an initially spherical liquid iron drop within a molten silicate phase, up to its possible fragmentation. We consider a 2D cylindrical axisymmetric geometry. We vary the viscosity of the molten silicates in the range of 0.05 Pa.s–100 Pa.s and the initial radius of the iron drop in the range of 1 mm–350 mm. Hence, we investigate Reynolds number in the range of [0.027–85600] and Weber number in the range of [0.073–7480]. Our numerical model constrains the morphology, dynamics and stability of the iron drop as a function of the dimensionless Weber and Reynolds numbers as well as of the viscosity ratio between the molten silicates and the liquid iron drop. In particular, we show that the maximal stable drop radius and the critical Weber number are monotonically increasing functions of the magma ocean viscosity. The momentum boundary layer thickness depends mainly on the drop radius and slightly on the magma ocean viscosity. Increasing the viscosity of the silicate phase prevents oscillations of the iron phase and limits the exchange surface. Oppositely, increasing the initial radius of the iron drop enhances its deformation and increases its relative exchange surface. Above the critical Weber number, we confirm that the fragmentation of the liquid iron occurs within a falling distance equal to 3.5–8 times the drop initial radius in the explored range of moderate Weber number, and we describe a variety of fragmentation regimes. Consequences for Earth’s formation models are briefly assessed.

Meso-Structure Controlled Synthesis of Sodium Iron-Manganese Oxides for Na-Ion Batteries

Increasing deployment of large scale electric storage applications would benefit from the development of inexpensive batteries. Na-ion batteries (NIBs) are of great interest since their cathodes can be made from inexpensive and abundant materials such as sodium, iron, and manganese. However, existing iron and manganese oxide cathodes lack the electrochemical performance, including capacity retention, required for these NIB applications and significant improvement is needed. Prior work on lithium ion battery cathodes demonstrates that meso-structured materials can improve electrochemical performance for batteries. Incorporating spherical meso-structured materials in lithium ion battery cathodes was shown to improve capacity retention. To emulate this approach in NIB cathode materials, a synthesis method for producing pure phase spherical meso-structured sodium iron manganese oxide is first needed. No literature has been found that describes a method for this synthesis. Key synthesis parameters to be controlled include the choice of method, material precursors, pH of reaction, calcination time, and cooling rate. In this work we demonstrate a modified co-precipitation method to synthesize spherical meso-structure pure phase P2-Na0.67Fe1/4Mn3/4O2 (see Figure 1) and we report initial characterization of the electrochemical performance of this material. The key parameter found to control the formation of a spherical meso-structure is the cooling rate applied during synthesis. The slow cooled material forms spherical meso-structures while the quenched material has no ordered meso-structure. Additionally, the spherical meso-structured material shows increased capacity, improved cyclability, and reduced polarization. The electrochemical performance enhancement is attributed to higher surface area, reduced surface concentration of sodium carbonate, and lower internal resistance during cycling. Further exploring the synthesis and mechanisms of meso-structured materials offers a path for improving Na-ion battery cathodes. Figure 1

Effect of Heat Treatmemt in (α+γ) Range on Mechanical Properties of Austempered Spheroidal Graphite Cast Iron

It is well known that austempered spheroidal graphite cast iron shows good tensile and elongation. And, retained austenite include in the austempered spheroidal graphite cast iron structure was known to effect for the mechanical properties when TRIP was occurred. On the other hand, fineness and homogeneity of the structure are considered to influence as a factor to improve mechanical property. In this study, the mechanical properties of spherical graphite cast iron was evaluated that it treatmented fineness prior-structure and austenitized at (α + γ) range followed by isothermal treatment at bainitic transformation temperature range. Compared the heat treatment of this study and typical austempering treatment, the mechanical properties with good balance of strength and ductility were obtained in the heat treatment of this study. But, retained austenite that it determined by x-ray diffraction was slightly changed before and after the tensile test. Therfore, it was considered that not TRIP but complex phase effect on mechanical properties.