Experimental and mechanism research of the effects of alkali on the reduction reaction of hematite during roasting reduction reaction

Red mud as one of the major waste materials, the recycling of it is very important for environmental security and resource recovery. However, the alkali in the red mud strongly affects the concentrating of iron. In order to make the reduction process more controllable and enhance the efficiency, this paper studied the roasting reduction reaction behavior of hematite and artificially mixed red mud in different alkaline environments. X-ray diffraction (XRD), vibrating Sample Magnetometer (VSM) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) were used to reveal the phase transformation, magnetic transformation and microstructure variation of the roasting products. The results revealed that the optimum reduction temperature and time of hematite in alkaline environment were 560 °C and 15 min respectively. With the increase of NaOH and Na₂SiO₃, the phase transformation from Fe₂O₃ to Fe₃O₄ of hematite was hindered. The depression effect of NaOH was stronger than that of Na2SiO3. However, with the increase of CaO, Na₂SiO₃/CaO and NaOH/CaO, the phase transformation from Fe₂O₃ to Fe₃O₄ in hematite was enhanced first, and then depressed. The gangue minerals in artificially mixed red mud involved in the reaction and consumed part of alkali. The morphology evolution of hematite was similar under different condition that reduction reaction in cracked region was more sufficient.     

Cordierite as catalyst support for nanocrystalline CuO/Fe2O3 system

CuO, Fe₂O₃ and CuO–Fe₂O₃ samples supported on cordierite (commercial grade) were prepared by wet impregnation method using finely powdered support material, copper and/or iron nitrates. The extent of loading was varied between 5 and 20 wt.% CuO, Fe₂O₃ or CuO–Fe₂O₃. The physicochemical, surface and catalytic properties of the various solids calcined at 350–700 °C were investigated using XRD, EDX, nitrogen adsorption at 77 K and CO-oxidation by O₂ at 220–280 °C.The results obtained revealed that the employed cordierite preheated at 350–700 °C was well-crystallized magnesium aluminum silicate (Mg₂Al₄Si₅O₁₈). Loading of 20 wt.% CuO or Fe₂O₃ on the cordierite surface calcined at 350 °C led to a partial dissolution of the added oxides in the support lattice forming solid solutions. The other portions remained as separate nanocrystalline CuO or Fe₂O₃ phases. The dissolved portions of the transition metal oxide increased upon increasing the calcination temperature from 350 to 500 °C. Loading of 20 wt.% CuO–Fe₂O₃ on the cordierite surface followed by calcination at 350 °C resulted in a solid–solid interaction between some of CuO and Fe₂O₃ yielding iron cuprate Fe₂CuO₄, which decomposed at ≥500 °C yielding copper and iron oxides. The portion of Fe₂O₃ dissolved in the cordierite lattice at 500 °C is twice that of CuO.The S_BET of cordierite increased several times by treating with small amounts of Fe₂O₃ or CuO. The increase was more pronounced by treating with Fe₂O₃. The catalytic activity of the cordierite increased progressively by increasing the amount of oxide(s) added. The mixed oxides system supported on cordierite and calcined at 350–700 °C showed catalytic activities much bigger than those measured for the individual supported systems. The synergistic effect manifested in case of solids calcined at 350 °C was attributed to the formation of surface iron cuprate. The significant increase in surface concentration of copper species on top surface layers of the solids treated with mixtures of copper and ferric oxides could be responsible for the synergistic effect for the mixed oxide catalysts calcined at 500 or 700 °C.     

Synthesis of Fe–4.6?wt% B alloy via electro-deoxidation of mixed oxides

Fe–4.6 wt% B alloy was synthesized via electro-deoxidation of the mixed oxide precursor. The oxides, Fe₂O₃ and B₂O₃, mixed in suitable proportions were sintered at 900 °C yielding pellets with a two-phase structure; Fe₂O₃ and Fe₃BO₆. The sintered pellets, connected as cathode, were then electro-deoxidized in molten CaCl₂ or in CaCl₂–NaCl eutectic, against a graphite anode at 3.1 V. The electrolysis at 850 °C has successfully yielded a powder mixture of Fe and Fe₂B. Sequence of changes during the electrolysis was followed by interrupted experiments conducted at 850 °C. This has shown that iron is extracted quite early during the electrolysis through the depletion of oxygen from the starting oxide; Fe₂O₃, forming the other iron oxides in the process. Boron follows a more complicated route. Fe₃BO₆, the initial boron-bearing phase, was depleted in the early stages due to its reaction with molten salt. This gave rise to the formation of calcium borate. Boron was extracted from calcium borate in later stages of electrolysis, which appeared to have reacted in situ with the iron forming compound Fe₂B. An erratum to this article can be found at     

Dielectric behaviour of MgFe2O4 prepared from chemically beneficiated iron ore rejects

Chemically beneficiated high silica/alumina iron ore rejects (27–76% Fe₂O₃) were used to synthesize iron oxides of purity 96–98% with SiO₂/Al₂O₃ ratio reduced to 0.03. The major impurities on chemical beneficiations were Al, Si, and Mn in the range 2–3%. A 99.73% purity Fe₂O₃ was also prepared by solvent extraction method using methyl isobutyl ketone (MIBK) from the acid extracts of the ore rejects. The magnesium ferrite, MgFe₂O₄, prepared from these synthetic iron oxides showed high resistivity of ∼ 10⁸ ohm cm. All ferrites showed saturation magnetization, 4πM_s, in the narrow range of 900–1200 Gauss and the Curie temperature,T, _cof all these fell within a small limit of 670 ± 30 K. All ferrites had low dielectric constants (ε′), 12–15, and low dielectric loss, tan δ, which decreased with the increase in frequency indicating a normal dielectric dispersion found in ferrites. The presence of insignificant amount of polarizable Fe²⁺ ions can be attributed to their high resistances and low dielectric constants. Impurities inherent in the samples had no marked influence on the electrical properties of the ferrites prepared from the iron ore rejects, suggesting the possibility of formation of ferrite of constant composition, MgFe₂O₄, of low magnetic and dielectric losses at lower temperatures of 1000°C by ceramic technique.     

A novel approach for synthesis of M-type hexaferrites nanopowders via the co-precipitation method

M-type hexaferrites; barium hexaferrite BaFe₁₂O₁₉ and strontium hexaferrite SrFe₁₂O₁₉ powders have been successfully prepared via the co-precipitation method using 5 M sodium carbonate solution as alkali. Effects of the molar ratio and the annealing temperature on the crystal structure, crystallite size, microstructure and the magnetic properties of the produced powders were systematically studied. The results indicated that a single phase of barium hexaferrite was obtained at Fe³⁺/Ba²⁺ molar ratio 12 annealed at 800–1,200 °C for 2 h whereas the orthorhombic barium iron oxide BaFe₂O₄ phase was formed as a impurity phase with barium M-type ferrite at Fe³⁺/Ba²⁺ molar ratio 8. On the other hand, a single phase of strontium hexaferrite was produced with the Fe³⁺/Sr²⁺ molar ratio to 12 at the different annealing temperatures from 800 to 1,200 °C for 2 h whereas the orthorhombic strontium iron oxide Sr₄Fe₆O₁₃ phase was formed as a secondary phase with SrFe₁₂O₁₉ phase at Fe³⁺/Sr²⁺ molar ratio of 9.23. The crystallite sizes of the produced nanopowders were increased with increasing the annealing temperature and the molar ratios. The microstructure of the produced single phase M-type ferrites powders displayed as a hexagonal-platelet like structure. A saturation magnetization (53.8 emu/g) was achieved for the pure barium hexaferrite phase formed at low temperature 800 °C for 2 h. On the other hand, a higher saturation magnetization value (M _s = 85.4 emu/g) was obtained for the strontium hexaferrite powders from the precipitated precursors synthesized at Fe³⁺/Sr²⁺ molar ratio 12 and thermally treated at 1,000 °C for 2 h.     

Synthesis of manganese–zinc ferrite by powder mixing using ferric oxide from a steel mill acid recovery unit

With the aim of producing fine-grained manganese–zinc (Mn–Zn) ferrite at the end of a calcination process at moderate temperatures, this study consisted, at first, of an “electrochemically designed” powder mixing by wet-ball milling a mixture of manganese (MnO₂), zinc (ZnO), and iron (Fe₂O₃ granules produced by an acid recovery unit of a Brazilian steelmaker, milled to fine sizes using alkaline media) –based raw materials. This mixing/milling resulted in improved size reduction when compared to milling without any alkali addition. Further, noticeable size reduction was achieved when elemental Zn was used in place of ZnO, especially when ammonia was used as the medium. Calcination of the alkaline-milled mixture of MnO₂ + ZnO + Fe₂O₃ at 1200 °C allowed obtaining well-crystallized single-phase Mn–Zn ferrite, whereas calcination of the MnO₂ + ZnO + Fe₂O₃ mill-mixed in 100% NH₄OH at 1200 °C produced the highest saturation magnetization in the as-calcined state.     

Simultaneous carbothermic reduction of iron and titanium oxides to produce an iron-based composite by mechanically activated sintering method

In this research, for the first time, Fe–TiC nano-crystalline composite was produced via simultaneous reduction of iron and titanium oxides by petrocoke. Powder mixture of Fe₂O₃/TiO₂/petrocoke was mechanically activated in a high-energy ball mill at different times. X-ray diffraction method (XRD) and Scanning Electron Microscopy (SEM) were used to characterize the milled powders. The results showed that new phases were not formed during milling, even after 20 h of milling. However, crystallite size and lattice strain of hematite were remarkably decreased and increased, respectively. Thermogravimetry and Differential Thermal Analysis (TG–DTA) were done on 0, 10 and 20 h mechanically activated powders. These experiments showed a substantial decrease in reduction temperature of iron and titanium oxides as a result of mechanical activation. Then, the powders were cold compacted and sintered at 1200 °C in argon atmosphere for 1 h. XRD results of 20 h milled samples demonstrated that, in this condition, iron oxide was completely reduced to nano-crystalline iron and titanium dioxide was reduced to nano-crystalline titanium carbide and Fe–TiC nano-crystalline composite was successfully formed.     

Oxygen release–absorption properties and structural stability of Ce0.8Fe0.2O2−x

Oxygen release–absorption properties and structural stability of Ce–Fe mixed oxides (Ce_0.8Fe_0.2O_2?x) with different calcination temperatures (600–1000 °C) were investigated and correlated to their oxygen storage capacity. Iron ions could be incorporated into the CeO₂ lattice to form a solid solution after calcination at low temperatures, but such solid solution was unstable under high-temperature thermal treatments. High-temperature (≥800 °C) calcination resulted in the appearance of exposed Fe₂O₃ phases on the surface of the solid solution, and this structural evolution finally affected the reduction behavior. The Fe³⁺ reduction from the Ce–Fe oxide solid solution was easier than the bulk Fe₂O₃ particles, while the small Fe₂O₃ particles in close contact with CeO₂ could enhance the reducibility of cerium oxides. The strong interaction between the exposed small Fe₂O₃ particles and the solid solution made the Ce–Fe mixed oxides possess good reduction stability and high oxygen storage capacity (OSC) even after repeated redox treatments. Such interactions were absent toward the physically mixed sample. An unusual enhancement on the reducibility of Ce–Fe mixed oxides was observed after a successive redox treatment. Large oxygen evolution appeared at around 600 °C for the recycled samples, and the OSC rose to 1.31 mmol-O₂/g after six redox cycles. The XRD, Raman, and TEM analyses revealed that the material structure of the mixed oxides was stabilized to have an inter-region between the Fe₂O₃ particles and the solid solution after the redox treatment. It was concluded that such microstructural evolutions of composite particle from solid solution under redox conditions brought beneficial property to the OSC of the Ce–Fe mixed oxides.     

Magnetic PNIPA hydrogels for hyperthermia applications in cancer therapy

Temperature-sensitive Poly (N-isopropylacrylamide), PNIPA gels were synthesized with micron-sized iron and iron oxide (Fe₃O₄) particles to investigate their viability for combined hyperthermia and drug release applications. The ultimate goal is to combine hyperthermia and triggered drug release. Induction heating of the magnetic hydrogels with varying concentration of magnetic powder was conducted at a frequency of 375 kHz for magnetic field strength varying from 1.7 kA/m to 2.5 kA/m. It was observed that the maximum temperature induced in the magnetic hydrogels increased with the concentration of magnetic particles and magnetic field strength. The PNIPA gel underwent a collapse transition at 34 °C. The best combination was found for the PNIPA–Fe₃O₄ system, 2.5 wt.% Fe₃O₄ in PNIPA–Fe₃O₄ system took 260 s to be heated to 45 °C under a magnetic field strength of 1.7 kA/m and the specific absorption rate (SAR) was found to be 1.83. SAR of iron oxide was found to be higher than the SAR of iron.     

Carbothermic reduction roasting for processing of ferruginous chromite ore using conventional and microwave heating

The present study investigates the recovery of chromite from a low-grade ferruginous ore through the carbothermic magnetization route using conventional and microwave heating sources. The carbothermic magnetization of ore is studied in both a horizontal tube furnace and a microwave oven by varying different process variables. The main objective of the study is to enhance the magnetic susceptibility of iron-bearing gangue minerals to enable the separation in a magnetic field. Alteration of crystalline structure and magnetic property of these minerals enables separation of low-grade ore by using magnetic separation. It is found that low-grade ferruginous chromite ore can be upgraded by reduction roasting, and 61.2% Cr₂O₃ was recovered with a chromium-to-iron ratio of 1.93 from a feed chromium-to-iron ratio of 1.01. The optimum result is achieved at a roasting temperature of 800 °C, with a roasting time of 60 min and a reductant dosage of 7.5%. Similarly, under microwave radiation, the chromium-to-iron ratio was upgraded to 1.81 with a recovery of 22%Cr₂O₃. The optimum result achieved under microwave radiation is at a microwave power of 900 W and exposure time of 7.5 min, with a reductant dosage of 10%. The findings of these two processing routes are discussed through characterization tools.     

Synthesis and dielectric properties of BiFeO<Subscript>3</Subscript> derived from molten salt method

BiFeO₃ powder was synthesized in NaCl media at temperature range from 700 to 800 °C, using Bi₂O₃ and Fe₂O₃ as raw materials. Effects of calcining temperature and salt ratios on the synthesis of BiFeO₃ powder had been investigated. It was found that NaCl effectively promoted the formation of BiFeO₃. Almost pure BiFeO₃ phase with a very small amount of Bi₂Fe₄O₉ phase was synthesized at 750 °C with salt weight ratios of 1:1. A large amount of BiFeO₃ phase decomposed to Bi₂Fe₄O₉ and Bi₂₅FeO₃₉ phase when the temperature was up to 800 °C. In the present method, the calcining temperature played an important role in the formation of BiFeO₃ phase. BiFeO₃ ceramics derived from molten salt method were prepared and exhibited the higher dielectric constant.     

A further investigation on the MnO2-Fe2O3 system roasted under CO-CO2 atmosphere

Investigations on the MnO₂-Fe₂O₃ system roasted in air has been reported in our previous work. This study further investigated the MnO₂-Fe₂O₃ system roasted under CO-CO₂ atmosphere. Extensive investigations were concentrated on the reduction of simplex iron oxides or manganese oxides, and little attention were paid on the reduction of MnO₂-Fe₂O₃ system regarding to interactive reactions between them. In this work, it was found that spinel-type Mn_xFe_3?xO₄ with high magnetism formed easily under CO-CO₂ atmosphere. The reduction and thermodynamic analyses of pure MnFe₂O₄ were also researched to better understand the reduction behaviors of MnO₂-Fe₂O₃ system. Phase study showed that a series of Mn-Fe composite oxides, including Mn_xFe_3?xO₄ and (MnO)_y(FeO)_1?y, generated during the reduction of MnO₂-Fe₂O₃ system. Mn_xFe_3?xO₄ was readily generated under CO content of 2.5–25?vol% at 1000?°C. With further increase of CO content, Mn_xFe_3?xO₄ was reduced to (MnO)_y(FeO)_1?y and then to MnO and metallic iron. Reduction of manganese oxides, iron oxides and manganese ferrites happened concurrently during the reduction of MnO₂-Fe₂O₃ system. And the reduction of MnO₂, Fe₂O₃, Fe₃O₄ and MnFe₂O₄ were compared by TG and thermodynamic analyses. In addition, the morphology evolution and magnetism change of the MnO₂-Fe₂O₃ system reduced under different CO contents were also studied.     

Natural and synthetic iron oxides for hydrogen storage and purification

In this paper, the hydrogen storage capacity of some synthetic and natural iron oxides is presented. The results of the activity tests and characterization techniques of natural and synthetic iron oxides (N₂ adsorption–desorption isotherms, temperature-programmed reduction, X-ray diffraction, and plasma atomic emission spectroscopy) suggest that the use of chromium on iron oxide systems improved their hydrogen storage capacity. This is related to the capacity of chromium to modify the iron oxide reduction profile when Cr was incorporated. A direct reduction from Fe₃O₄ to Fe was observed as the mechanism for H₂ storage. In addition, natural oxides as commercial Superfine and Densinox-L oxides are proved to be suitable materials to store and purify H₂ due to their high stability during different cycles of reduction and oxidation. The best results among the natural ones were Densinox-L and among the synthetic ones Fe–10Cr.     

Microwave-induced substitutional-combustion reaction of Fe3O4/Al ceramic matrix porous composite

Microwave processing and substitutional-combustion reaction have been utilized to fabricate ceramic matrix porous composite from the thermite reaction of Fe3O4/Al system. Stoichiometric and mixtures with lower and over aluminum were tested. As this system was highly exothermic, the melting of reaction products and destruction the porous structure may occur. In order to avoid that, reaction coupled with a smaller driving force by controlling the microwave (MW) ignition condition at low temperature exotherm, where substitutional reaction occurs has been investigated. The phase and microstructure evolution during the reaction is analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Thermogram of the DTA analysis, irrespective of their mole ratio, recorded two exothermic peaks, one at ~1310 °C and another one at ~1370 °C. Fe and α-Al₂O₃ were the main products for the combusted mixture. Hercynite appeared as the major phase in the stoichiometric and slightly lower Al content mixtures due to incompleteness of reaction. In contrary, over aluminized mixture revealed the presence of Al_3.2Fe. When heated at 1360 °C, an additional FeO phase was observed. Mixtures with extremely low Al content showed the presence of unreacted Fe₃O₄ and some free Al due to the decrease of combustion velocity associated with a decrease in the sample exothermicities. Sample heated in electric furnace was dense. When heating by microwave, controlling the reaction progress at low temperature exotherm allowed the achievement of porous structure composite consisting of micron size iron particles well distributed and embedded in the hercynite and/or Al₂O₃ matrix.     

Preparation of mullite-based iron magnetic nanocomposite powders by reduction of solid solution

In this article, the preparation of mullite-based iron magnetic nanocomposite powders by hydrogen reduction of Fe-doped mullite solid solution with a nominal composition of Al_5.4Fe_0.6Si₂O₁₃ is reported. The formation process of Al_5.4Fe_0.6Si₂O₁₃ solid solution was analyzed using X-ray diffraction analysis (XRD), Fourier Transform Infrared Spectrum (FT-IR), thermogravimetric, and differential thermal analysis (TG-DTA). It is found that doping with Fe³⁺ cation affects the crystallization temperature of mullite. During the hydrogen reduction process, more than 89% Fe³⁺ cation in solid solution were transformed into α-Fe phase when reduction temperature reached 1200 °C. Microstructure characterization of nanocomposite powders reduced at 1300 °C reveals that there are two types of α-Fe particles in mullite matrix. Fe nanoparticles with a size of approximately 10 nm were precipitated within the mullite grains, while Fe particles larger than hundreds of nanometers were located at the surfaces of the mullite grains. The measurement of the magnetic properties of nanocomposite powders indicates that large particles and nanoparticles of α-iron have the ferromagnetic and superparamagnetic behavior at room temperature, respectively.     

Hydrogen evolution kinetics during transition metal oxide-catalyzed ammonia borane hydrolysis

This paper examines the feasibility of using transition metal oxides (cobalt, iron, copper, molybdenum, and vanadium oxides) as catalysts for ammonia borane (AB) hydrolysis. In our experiments, we used an aqueous solution containing 0.24 wt % AB. The amount of oxide catalysts was 10–40 mg. The hydrolysis process was run in the temperature range from 35 to 80°C. The highest hydrogen evolution rate was observed at a temperature of 80°C in the presence of cobalt and iron oxides (Co₃O₄ and Fe₂O₃ · nH₂O). The data obtained for the cobalt and iron oxides demonstrate that the reaction is first-order in ammonia borane. We determined the rate constants of the process and its apparent activation energy: 47.5 kJ/mol for Co₃O₄ and 60.2 kJ/mol for Fe₂O₃ · nH₂O. The cobalt and iron oxides were shown to be efficient catalysts for hydrogen production from aqueous AB solutions.     

Powder reduction kinetics of dicalcium ferrite,calcium ferrite,and hematite: Measurement and modeling

Shrinking core model is widely applied to describe the reduction of iron ore pellets, but limited to the illustration on powder sample. The reduction of powder materials is commonly observed in blast furnace production but has been rarely investigated. In this study, thermal kinetics analysis was conducted to describe the powder reduction of dicalcium ferrite (2CaO?Fe₂O₃, C₂F), calcium ferrite (CaO?Fe₂O₃, CF), and hematite (Fe₂O₃, H), with particle sizes below 70 µm. Isothermal reduction experiments were performed through thermogravimetry analysis under CO atmosphere. The reduction degrees and reaction rate constants increased in the order of C₂F, CF, and H at 1123, 1173, and 1223 K. The reduction rate analysis illustrated that the reduction of C₂F, CF, and H appeared as one-, two-, and three-stage reactions, respectively. Moreover, the reduction of C₂F and CF proceeded as the 2D reaction mechanism described by Avrami–Erofeev (A-E) equation. The reduction of H was initially controlled by 2D, followed by the 3D A-E kinetics equation. Phase with superior reducibility could be reduced by CO in more dimensions of sample layers. The reduction degrees and rate change expressed by A-E equations were verified to be in accordance with the experimental data. A new kinetics model was proposed to elucidate the reduction of C₂F, CF, and H in ultrafine powder compared with that in pellets. The reduction process in the powdered samples comprised independent reduction stages caused by uniform CO diffusion in powdered particles.     

One-step solution auto-combustion process for the rapid synthesis of crystalline phase iron oxide nanoparticles with improved magnetic and photocatalytic properties

We report the solution auto-combustion (AC) process for the rapid synthesis of Fe₃O₄ nanoparticles derived from the sol–gel (SG) process. The citric acid (CA) and tartaric acid (TA) is used as gelling agents in the SG process, where the citric acid turns into a fuel that combusts the gel and yields a highly magnetic crystalline phase Fe₃O₄ nanoparticles in one step with an average particle size of 50 nm. In contrast, the citric acid at different concentrations and tartaric acid at any concentrations do not lead to any combustion process and yield amorphous iron oxides. Upon annealing, these CA and TA derived iron oxide samples are turned to crystalline phase α-Fe₂O₃ particles. In contrast, the as-synthesized AC sample (i.e. Fe₃O₄) is oxidized to γ-Fe₂O₃ phase, which is confirmed from their respective XRD, Rietveld refinement and XPS studies. All the synthesized iron oxide phases showed broad visible light absorption. The room temperature M?H hysteresis curves obtained from VSM revealed that the Fe₃O₄ and α-Fe₂O₃/γ-Fe₂O₃ phases exhibit super-paramagnetic and ferromagnetic properties, respectively. The photocatalytic efficiencies of the samples are found to be in the order of Fe₃O₄ > γ-Fe₂O₃ > α-Fe₂O₃ with 98, 87, 79/73% degradation of rhodamine B dye at the end of 3 h and H₂ evolution rate over these systems is found to be 2.1, 1.3 and 0.92/0.89 mmol/h/g, respectively under simulated solar light irradiation. The photocatalytic recycle studies demonstrated that all the synthesized photocatalysts possess excellent chemical and photo-stabilities.     

Magnet–PNIPA hydrogels for bioengineering applications

Temperature-sensitive Poly (N-isopropylacrylamide), PNIPA gels were synthesized with micron-sized iron and iron oxide (Fe₃O₄) particles to investigate their viability for hyperthermia applications. Induction heating of the magnetic hydrogels with varying concentration of magnetic powder was conducted at a frequency of 375  kHz for magnetic field strength varying from 1.7 kA/m (21 Oe) to 2.5 kA/m (31.4 Oe). It was observed that the maximum temperature induced in the magnetic hydrogels increased with the concentration of magnetic particles and magnetic field strength. The PNIPA gel underwent a collapse transition at 34 °C. It was found that a 2.5 wt.% Fe₃O₄ in PNIPA composite took 260 s to be heated to 45 °C under a magnetic field strength of 1.7 kA/m, the specific absorption rate (SAR) was found to be 1.83. SAR of iron oxide was found to be higher than the SAR of iron.     

Synthesis of multicomponent nanocomposites containing filamentary carbon nanostructures

Abstract

In this work, the multicomponent nanocomposites containing filamentary carbon nanostructures were synthesized using materials based on iron oxides with a predominant content of the epsilon phase (ε-Fe₂O₃). These iron oxide-based materials were obtained by a direct plasma-dynamic synthesis with supersonic outflow of an iron-containing electric discharge plasma into an oxygen atmosphere. Subsequently, they were used as an initial precursor and placed in the plasma-chemical reactor, where the multicomponent C/Si_xO_y/Fe₂O₃ nanostructures were synthesized under the influence of the pulsed electron beam. This method was based on the volume excitation of the reaction gas by a pulsed electron beam in such a way as to control the uniform process implementation in the entire excitation region. The morphology and phase composition of the synthesized C/Si_xO_y/Fe₂O₃ nanocomposites were studied. A typical morphological feature of the C/Si_xO_y/Fe₂O₃ samples was found to be the formation of filamentary nanostructures. Their diameter does not exceed 10–20?nm, while their length varies up to 1?μm.