Cellulose-precursor synthesis of nanocrystalline Co0.5Cu0.5Fe2O4 spinel ferrites

International Nuclear Information System (INIS)

Ounnunkad, Kontad; Phanichphant, Sukon

2012-01-01

Highlights: ► Synthesis of spinel copper cobalt nanoferrite particles from a cellulose precursor for the first time. Control of nanosize and properties of nanoferrites can take place by varying the calcining temperature. The simple, low cost, easy cellulose process is a choice of nanoparticle processing technology. -- Abstract: Nanocrystalline Cu 0.5 Co 0.5 Fe 2 O 4 powders were prepared via a metal-cellulose precursor synthetic route. Cellulose was used as a fuel and a dispersing agent. The resulting precursors were calcined in the temperature range of 450–600 °C. The phase development of the samples was determined by using Fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (XRD). The field-dependent magnetizations of the nanopowders were measured by vibrating sample magnetometer (VSM). All XRD patterns are of a spinel ferrite with cubic symmetry. Microstructure of the ferrites showed irregular shapes and uniform particles with agglomeration. From XRD data, the crystallite sizes are in range of 16–42 nm. Saturation magnetization and coercivity increased with increasing calcining temperature due to enhancement of crystallinity and reduction of oxygen vacancies.

Low-loss Z-type hexaferrite (Ba3Co2Fe24O41) for GHz antenna applications

Science.gov (United States)

Lee, Woncheol; Hong, Yang-Ki; Park, Jihoon; LaRochelle, Gatlin; Lee, Jaejin

2016-09-01

We report a low magnetic loss Ba3Co2Fe24O41 (Co2Z) hexaferrite for use in gigahertz (GHz) antennas. Acid-etching was very effective in removal of unwanted Y-type hexaferrite (Ba2Co2Fe12O22) from calcined Co2Z powder. It is found that the calcined and acid etched (AE) Co2Z hexaferrite shows a low magnetic loss tangent (tan δμ) of 0.012 and 0.037 at 1 and 2 GHz, respectively. These low tan δμ are attributed to removal of Y-type hexaferrite, which possesses a lower anisotropy field (Hk) than W-type hexaferrite (BaCo2Fe16O27). The figure of merit (FOM) of the AE Co2Z hexaferrite is 141.7 and 48.7 at 1 and 2 GHz, respectively. These FOM are much higher than the FOM of previously reported low-loss magnetic materials. Therefore, the AE Co2Z hexaferrite can be a good candidate for GHz antenna application in the ultra-high frequency (UHF) band.

Characterization of SrCo{sub 1.5}Ti{sub 1.5}Fe{sub 9}O{sub 19} hexagonal ferrite synthesized by sol-gel combustion and solid state route

Energy Technology Data Exchange (ETDEWEB)

Vinaykumar, R., E-mail: vinaykumar.r1984@gmail.com; Mazumder, R., E-mail: ranabrata@nitrkl.ac.in; Bera, J., E-mail: jbera@nitrkl.ac.in

2017-05-01

Co-Ti co-substituted SrM hexagonal ferrite (SrCo{sub 1.5}Ti{sub 1.5}Fe{sub 9}O{sub 19}) was synthesized by sol-gel combustion and solid state route. The effects of sources of TiO{sub 2} raw materials; titanium tetra-isopropoxide (TTIP) and titanyl nitrate (TN) on the phase formation behavior and properties of the ferrite were studied. The thermal decomposition behavior of the gel was studied using TG-DSC. The phase formation behavior of the ferrite was studied by using X-ray powder diffraction and FTIR analysis. Phase formation was comparatively easier in the TN-based sol-gel process. The morphology of powder and sintered ferrite was investigated using scanning electron microscope. Magnetic properties like magnetization, coercivity, permeability, tan δ{sub µ} and dielectric properties were investigated. The ferrite synthesized by sol-gel based chemical route showed higher saturation magnetization, permeability and permittivity compared to the ferrite synthesized by solid state route. - Highlights: • SrCo{sub 1.5}Ti{sub 1.5}Fe{sub 9}O{sub 19} ferrite was successfully prepared by sol–gel combustion process. • Sol-gel synthesis of the ferrite using titanyl nitrate has been reported first time. • Phase formation was easier in the titanyl nitrate based sol-gel process. • Better magneto-dielectric properties were observed in sol-gel processed ferrite.

Microstructural evolution of ferritic steel powder during mechanical alloying with iron oxide

Energy Technology Data Exchange (ETDEWEB)

Wen, Yuren; Liu, Yong; Liu, Donghua; Tang, Bei [Central South Univ., State Key Lab. of Powder Metallurgy, Changsha (China); Liu, C.T. [The Hong Kong Polytechnic Univ., Dept. of Mechanical Engineering, Hong Kong (China)

2011-02-15

Mechanical alloying of mixed powders is of great importance for preparing oxide dispersion strengthened ferritic steels. In this study, the microstructural evolution of ferritic steel powder mixed with TiH{sub x}, YH{sub 2} and Fe{sub 2}O{sub 3} in the process of mechanical alloying is systematically investigated by using X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and microhardness tests. It is found that titanium, yttrium hydrides and iron oxide are completely dissolved during milling, and homogeneous element distribution can be achieved after milling for 12 h. The disintegration of the composite powder particles occurs at 24 h and reaches the balance of welding and fracturing after 36 h. The oxygen content increases sharply with the disintegration of powder particles due to the absorption of oxygen at the solid/gas interface from the milling atmosphere, which is the main source of extra oxygen in the milled powder. Grain refinement down to nanometer level occurs due to the severe plastic deformation of particles; however, the grain size does not change much with further disintegration of particles. The hardness increases with milling time and then becomes stable during further milling. The study indicates that the addition of iron oxide and hydrides may be more beneficial for the dispersion and homogenization of chemical compositions in the powder mixture, thus shortening the mechanical alloying process. (orig.)

The influence of dislocation defects on the sintering kinetics of ferrite powders

International Nuclear Information System (INIS)

Fadeeva, I.V.; Portnoi, K.V.; Oleinikov, N.N.; Tretyakov, D.Yu.

1976-01-01

In the presented paper are given the results of the X-ray investigations of non-equilibrium defects in powders of nickel-zinc ferrites. The block size, the crystal lattice microdistortions and stacking faults of two types were determined by the method of Fourier's analysis of diffraction line profiles. The influence of similar defects on sintering of ferrite powders was shown. The kinetics data on densification processes occurring during sintering of active powders can adequately be described in terms of the equations which describe reactions in the solid phase, where the interaction limit is on the border of the phases with different geomtery of the border. The correlation between the behaviour of compacts and dislocation defects in powders during sintering is established

Structural, Magnetic and Microwave Properties of Nanocrystalline Ni-Co-Gd Ferrites

Science.gov (United States)

Nikzad, Alireza; Parvizi, Roghaieh; Rezaei, Ghasem; Vaseghi, Behrooz; Khordad, Reza

2018-02-01

A series of Co- and Gd-substituted NiFe2O4 ferrite nanoparticles with the formula Ni1- x Co x Fe2- y Gd y O4 (where x = 0.0-1.0 and y = 0.0-0.1) have been successfully synthesized using a hydrothermal method. X-ray diffraction and field emission scanning electron microscopy results indicated that a highly crystallized spherical ferrite nanoparticle structure was obtained along with an increase in the lattice parameters. Compositional analysis of the prepared nanoferrite powders has been carried out using energy-dispersive x-ray (EDX) spectra. The EDX analysis reveals the presence of Ni, Co, Gd and Fe elements in the specimens. Magnetization and the coercive field improved dramatically with an increase in the amount of cobalt and gadolinium added, attributed to the redistribution of cations in the spinel nanoferrite structure. Saturation magnetization and coercivity values up to 99 emu/g and 918 Oe, respectively, were measured using a vibration sample magnetometer at room temperature. Comparative microwave absorption experiments demonstrated that the reflection loss (RL) properties enhanced with increasing substitution of cations in the Ni-ferrite spinel structure for an absorber thickness of 1.8 mm. A maximum RL of - 26.7 dB was obtained for substituted Ni-Co-Gd nanoferrite with x = 1.0 and y = 0.1 at a frequency of 9.4 GHz with a bandwidth of 3.6 GHz (RL ≤ - 10 dB). Experimental results revealed that the synthesized nanoparticles possessed great potential in microwave absorption applications.

Structural, dielectric and gas sensing behavior of Mn substituted spinel MFe{sub 2}O{sub 4} (M=Zn, Cu, Ni, and Co) ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Ranjith Kumar, E., E-mail: ranjueaswar@gmail.com [Department of Physics, Dr. NGP Institute of Technology, Coimbatore 641048, Tamil Nadu (India); Siva Prasada Reddy, P.; Sarala Devi, G. [Inorganic and Physical Chemistry Division, Indian Institute Chemical Technology, Hyderabad 500607 (India); Sathiyaraj, S. [Department of Chemistry, Dr. NGP Institute of Technology, Coimbatore 641048, Tamil Nadu (India)

2016-01-15

Spinel ferrite (MnZnFe{sub 2}O{sub 4}, MnCuFe{sub 2}O{sub 4}, MnNiFe{sub 2}O{sub 4} and MnCoFe{sub 2}O{sub 4}) nanoparticles have been prepared by evaporation method. The annealing temperature plays an important role on changing particle size of the spinel ferrite nanoparticles was found out by X-ray diffraction and transmission electron microscopy. The role of manganese substitution in the spinel ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in dielectric properties have been measured in the frequency range of 100 kHz to 5 MHz. These spinel ferrites are decomposed to α-Fe{sub 2}O{sub 3} after annealing above 550 °C in air. Through the characterization of the prepared powder, the effect of annealing temperature, chemical composition and preparation technique on the microstructure, particle size and dielectric properties of the Mn substituted spinel ferrite nanoparticles are discussed. Furthermore, Conductance response of Mn substituted MFe{sub 2}O{sub 4} ferrite nanoparticles were measured by exposing the materials to reducing gas like liquefied petroleum gas (LPG). - Highlights: • The egg white support to achieve sample with shorter reaction time. • Manganese plays a significant role in sensor response. • Nature of the ferrites was affected with increasing annealing temperature.

Effect of Powder Grain Size on Microstructure and Magnetic Properties of Hexagonal Barium Ferrite Ceramic

Science.gov (United States)

Shao, Li-Huan; Shen, Si-Yun; Zheng, Hui; Zheng, Peng; Wu, Qiong; Zheng, Liang

2018-05-01

Compact hexagonal barium ferrite (BaFe12O19, BaM) ceramics with excellent magnetic properties have been prepared from powder with the optimal grain size. The dependence of the microstructure and magnetic properties of the ceramics on powder grain size was studied in detail. Single-phase hexagonal barium ferrite powder with grain size of 177 nm, 256 nm, 327 nm, and 454 nm was obtained by calcination under different conditions. Scanning electron microscopy revealed that 327-nm powder was beneficial for obtaining homogeneous grain size and compact ceramic. In addition, magnetic hysteresis loops and complex permeability spectra demonstrated that the highest saturation magnetization (67.2 emu/g) and real part of the permeability (1.11) at 1 GHz were also obtained using powder with grain size of 327 nm. This relationship between the powder grain size and the properties of the resulting BaM ceramic could be significant for development of microwave devices.

Green Synthesis Methods of CoFe_2O_4 and Ag-CoFe_2O_4 Nanoparticles Using Hibiscus Extracts and Their Antimicrobial Potential

International Nuclear Information System (INIS)

Gingasu, D.; Mindru, I.; Patron, L.; Caleron-Moreno, J.M.; Mocioiu, O.C.; Preda, S.; Stanica, N.; Nita, S.; Dobre, N.; Popa, M.; Gradisteanu, G.; Chifiriuc, M. C.

2016-01-01

The cobalt ferrite (CoFe_2O_4) and silver-cobalt ferrite (Ag-CoFe_2O_4) nanoparticles were obtained through self-combustion and wet ferritization methods using aqueous extracts of Hibiscus rosa-sinensis flower and leaf. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and magnetic measurements were used for the characterization of the obtained oxide powders. The antimicrobial activity of the cobalt ferrite and silver-cobalt ferrite nanoparticles against Gram-positive and Gram-negative bacteria, as well as fungal strains, was investigated by qualitative and quantitative assays. The most active proved to be the Ag-CoFe_2O_4 nanoparticles, particularly those obtained through self-combustion using hibiscus leaf extract, which exhibited very low minimal inhibitory concentration values (0.031-0.062 mg/ml) against all tested microbial strains, suggesting their potential for the development of novel antimicrobial agents.

Green Synthesis Methods of CoFe2O4 and Ag-CoFe2O4 Nanoparticles Using Hibiscus Extracts and Their Antimicrobial Potential

Directory of Open Access Journals (Sweden)

Dana Gingasu

2016-01-01

Full Text Available The cobalt ferrite (CoFe2O4 and silver-cobalt ferrite (Ag-CoFe2O4 nanoparticles were obtained through self-combustion and wet ferritization methods using aqueous extracts of Hibiscus rosa-sinensis flower and leaf. X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and magnetic measurements were used for the characterization of the obtained oxide powders. The antimicrobial activity of the cobalt ferrite and silver-cobalt ferrite nanoparticles against Gram-positive and Gram-negative bacteria, as well as fungal strains, was investigated by qualitative and quantitative assays. The most active proved to be the Ag-CoFe2O4 nanoparticles, particularly those obtained through self-combustion using hibiscus leaf extract, which exhibited very low minimal inhibitory concentration values (0.031–0.062 mg/mL against all tested microbial strains, suggesting their potential for the development of novel antimicrobial agents.

Structure and magnetic properties of Mg0.35Cu0.2Zn0.45Fe2O4 ferrite synthesized by co-precipitation method

Directory of Open Access Journals (Sweden)

Bo Yang

2017-05-01

Full Text Available Mg0.35Cu0.2Zn0.45Fe2O4 nanosize particles have been synthesized by chemical co-precipitation method and characterized by X-ray diffraction (XRD and vibrating sample magnetometry (VSM. The XRD patterns confirmed the single phase spinel structure of the synthesized powder. The average crystallite size of the powder varied from 14 to 55 nm by changing annealing temperature. The activation energy for crystal growth was estimated as about 18.61KJ/mol. With the annealing temperature increasing, saturation magnetization (MS was successively increased while the coercivity (HC was first increased, passed through a maximum and then declined. The sintering temperature has significant influence on bulk density, initial permeability and Curie temperature of Mg0.35Cu0.2Zn0.45Fe2O4 ferrite.

Characterization of Ni ferrites powders prepared by plasma arc discharge process

Energy Technology Data Exchange (ETDEWEB)

Safari, A. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Gheisari, Kh., E-mail: khgheisari@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Farbod, M. [Physics Department, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)

2017-01-01

The aim of this work was to synthesize a single-phase spinel structure from a mixture of zinc, iron and nickel powders by plasma arc discharge method. A mixture of zinc, iron and nickel powders with the appropriate molar ratio was prepared and formed into a cylindrical shape. The synthesis process was performed in air, oxygen and argon atmospheres with the applied arc current of 400 A and pressure of 1 atm. After establishing an arc between the electrodes, the produced powders were collected and their structure and magnetic properties were examined by XRD and VSM, respectively. ZnO as an impurity was appeared in the as-produced powders owing to the high reactivity of zinc atoms, preventing the formation of Ni–Zn ferrite. A pure spinel structure with the highest saturation magnetization (43.8 emu/g) was observed as zinc powders removed completely from the initial mixture. Morphological evaluations using field emission scanning electron microscopy showed that the mean size of fabricated nanoparticles was in the range 100–200 nm and was dependent on the production conditions. - Highlights: • Nanocrystalline Ni ferrite powders are prepared by plasma arc discharge process. • The mean particle size of the as-synthesized ceramic powders is about 100 nm. • The highest saturation magnetization is observed as zinc powders removed completely from the initial mixture.

Influence of reagents mixture density on the radiation-thermal synthesis of lithium-zinc ferrites

Science.gov (United States)

Surzhikov, A. P.; Lysenko, E. N.; Vlasov, V. A.; Malyshev, A. V.; Korobeynikov, M. V.; Mikhailenko, M. A.

2017-01-01

Influence of Li2CO3-ZnO-Fe2O3 powder reagents mixture density on the synthesis efficiency of lithium-zinc ferrites in the conditions of thermal heating or pulsed electron beam heating was studied by X-Ray diffraction and magnetization analysis. The results showed that the including a compaction of powder reagents mixture in ferrite synthesis leads to an increase in concentration of the spinel phase and decrease in initial components content in lithium-substituted ferrites synthesized by thermal or radiation-thermal heating.

Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

International Nuclear Information System (INIS)

Oliver, S. A.; Harris, V. G.; Hamdeh, H. H.; Ho, J. C.

2000-01-01

The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn 0.55 2+ Fe 0.18 3+ ) tet [Zr 0.45 2+ Fe 1.82 3+ ] oct O 4 through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe 3+ on both sites is consistent with the measured room temperature magnetic properties. (c) 2000 American Institute of Physics

Dopant driven tunability of dielectric relaxation in MxCo(1-x)Fe2O4 (M: Zn2+, Mn2+, Ni2+) nano-ferrites

Science.gov (United States)

Datt, Gopal; Abhyankar, A. C.

2017-07-01

Nano-ferrites with tunable dielectric and magnetic properties are highly desirable in modern electronics industries. This work reports the effect of ferromagnetic (Ni), anti-ferromagnetic (Mn), and non-magnetic (Zn) substitution on cobalt-ferrites' dielectric and magnetic properties. The Rietveld analysis of XRD data and the Raman spectroscopic study reveals that all the samples are crystallized in the Fd-3m space group. The T2g Raman mode was observed to split into branches, which is due to the presence of different cations (with different vibrational frequencies) at crystallographic A and B-sites. The magnetization study shows that the MnCoFe2O4 sample has the highest saturation magnetization of 87 emu/g, which is attributed to the presence of Mn2+ cations at the B-site with a magnetic moment of 5 μB. The dielectric permittivity of these nanoparticles (NPs) obeys the modified Debye model, which is further supported by Cole-Cole plots. The dielectric constant of MnCoFe2O4 ferrite is found to be one order higher than that of the other two ferrites. The increased bond length of the Mn2+-O2- bond along with the enhanced d-d electron transition between Mn 2 +/Co 2 +⇋Fe 3 + cations at the B-site are found to be the main contributing factors for the enhanced dielectric constant of MnCoFe2O4 ferrite. We find evidence of variable-range hopping of localized polarons in these ferrite NPs. The activation energy, hopping range, and density of states N (" separators="|EF ), of these polarons were calculated using Motts' 1/4th law. The estimated activation energies of these polarons at 300 K were found to be 288 meV, 426 meV, and 410 meV, respectively, for the MnCoFe2O4, NiCoFe2O4, and ZnCoFe2O4 ferrite NPs, while the hopping range of these polarons were found to be 27.14 Å, 11.66 Å, and 8.17 Å, respectively. Observation of a low dielectric loss of ˜0.04, in the frequency range of 0.1-1 MHz, in these NPs makes them potential candidates for energy harvesting devices in

Synthesis, characterization and adsorption capability for Congo red of CoFe2O4 ferrite nanoparticles

International Nuclear Information System (INIS)

Ding, Zui; Wang, Wei; Zhang, Yajun; Li, Feng; Liu, J. Ping

2015-01-01

Highlights: • CoFe 2 O 4 ferrite nanoparticles are synthesized by an ethanol-assisted hydrothermal method. • Suitable amount of ethanol can reduce the particle size and increase BET surface area. • The introduction of ethanol leads to the cation redistribution. • Using ethanol/water mixed solution greatly enhances their adsorption capacity for CR dyes. - Abstract: CoFe 2 O 4 ferrite nanoparticles are synthesized by an ethanol-assisted hydrothermal method, where the ethanol is mixed with water as the solution. In this synthesis, a rapid mixing of reducible metal cations with reducing agent and a simultaneous reduction process take place in a colloid mill. Synthesized ferrite samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Raman spectroscopy. XRD patterns reveal the formation of CoFe 2 O 4 ferrites with single spinel phase. SEM and TEM images show that the as-synthesized samples are with narrow size distribution. Raman spectroscopy studies clearly indicate the cation distribution in nanosized particles. Here, it is worthy to note that, with increasing ethanol content in ethanol–water mixed solution, an obvious superparamagnetic behavior of as-synthesized nanoparticles at room temperature is observed. The adsorption capability of the as-synthesized ferrite nanoparticles for Congo Red (CR) is examined. Enhancement of adsorption capability for CR with adding ethanol as the mixing solution is shown. The adsorption mechanism is discussed. This investigation reveals that the composition of ethanol/water mixed solution has great effects on the microstructure and magnetic properties as well as adsorption capacity of Congo Red (CR) dye of the as-synthesized CoFe 2 O 4 ferrite samples

Large zinc cation occupancy of octahedral sites in mechanically activated zinc ferrite powders

Energy Technology Data Exchange (ETDEWEB)

Oliver, S. A. [Center for Electromagnetic Research, Northeastern University, Boston, Massachusetts 02115 (United States); Harris, V. G. [Complex Materials Section, Code 6342, Naval Research Laboratory, Washington, DC 20375 (United States); Hamdeh, H. H. [Department of Physics, Wichita State University, Wichita, Kansas 67260 (United States); Ho, J. C. [Department of Physics, Wichita State University, Wichita, Kansas 67260 (United States)

2000-05-08

The cation site occupancy of a mechanically activated nanocrystalline zinc ferrite powder was determined as (Zn{sub 0.55}{sup 2+}Fe{sub 0.18}{sup 3+}){sub tet}[Zr{sub 0.45}{sup 2+}Fe{sub 1.82}{sup 3+}]{sub oct}O{sub 4} through analysis of extended x-ray absorption fine structure measurements, showing a large redistribution of cations between sites compared to normal zinc ferrite samples. The overpopulation of cations in the octahedral sites was attributed to the ascendance in importance of the ionic radii over the crystal energy and bonding coordination in determining which interstitial sites are occupied in this structurally disordered powder. Slight changes are observed in the local atomic environment about the zinc cations, but not the iron cations, with respect to the spinel structure. The presence of Fe{sup 3+} on both sites is consistent with the measured room temperature magnetic properties. (c) 2000 American Institute of Physics.

Processing line for industrial radiation-thermal synthesis of doped lithium ferrite powders

Science.gov (United States)

Surzhikov, A. P.; Galtseva, O. V.; Vasendina, E. A.; Vlasov, V. A.; Nikolaev, E. V.

2016-02-01

The paper considers the issues of industrial production of doped lithium ferrite powders by radiation-thermal method. A technological scheme of the processing line is suggested. The radiation-thermal technological scheme enables production of powders with technical characteristics close to the required ones under relatively low temperature annealing conditions without intermediate mixing. The optimal conditions of the radiation-thermal synthesis are achieved isothermally under irradiation by the electron beam with energy of 2.5 MeV in the temperature range of 700-750 0C within- 120 min.

Magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared at room temperature: variation with crystallite size

Energy Technology Data Exchange (ETDEWEB)

Rajendran, M.; Pullar, R.C.; Bhattacharya, A.K. E-mail: ashokbhattacharya@warwick.ac.uk; Das, D.; Chintalapudi, S.N.; Majumdar, C.K

2001-06-01

The magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared by a redox process at room temperature have been studied by vibrating sample magnetometer (VSM). The average crystallite size of the powders varied from 6 to 20 nm by changing the synthesis conditions and the corresponding saturation magnetisation (M{sub s}) value ranged from 9 to 38 emu g{sup -1}. On heating, the crystallite size increased with corresponding increase in M{sub s} values. At 1073 K all samples achieved M{sub s} values close to 73 emu g{sup -1}. On increasing the crystallite size, the coercivity (H{sub c}) increased passed through a maximum and dropped. Cobalt ferrite powder with an average crystallite size of 6 nm prepared at room temperature achieved desirable values of M{sub s}=60 emu g{sup -1} and H{sub c}=1.42 kOe after thermal annealing at 973 K. The Moessbauer spectra were recorded for CoFe{sub 2}O{sub 4} having a range of crystallite sizes at room temperature and at low temperatures down to 40 K. The magnetic and Moessbauer results are provided for nanocrystalline CoFe{sub 2}O{sub 4} as a function of crystallite size and measurement temperature.

Effect of Co2+ and Y3+ ions insertion on the microstructure development and magnetic properties of Ni0.5Zn0.5Fe2O4 powders synthesized using Co-precipitation method

Science.gov (United States)

Rashad, M. M.; Rayan, D. A.; Turky, A. O.; Hessien, M. M.

2015-01-01

Nanocrystalline Ni0.5Zn0.5-xCoxFe2-zYzO4 powders (x=0-0.3 and z from 0 to 0.3) have been synthesized via a facile co-precipitation technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) are utilized in order to study the effect of variation of cobalt and yttrium substitutions and its impact on crystalline size, lattice parameter, X-ray density, microstructure and magnetic properties of the formed powders. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase for the formed precursors precipitated at pH 10 annealed at 1000 oC for 2 h. The lattice parameter and the unit cell were decreased linearly with increasing Co content whereas they were increased with increasing the Y incorporation. Additionally, the porosity was increased with increasing Co concentration while it was decreased with increasing the Y insertion. The mean ionic radii and hopping and bond lengths was decreased with the value of Co2+ and they were increased with the value of Y3+ ion as well as both of Y3+ and Co2+ ions. The microstructures of the produced powders were found to be cubic like structure. The addition of Y3+ ion suppressed the grain size whereas addition of Co2+ ion enhanced the grain growth availably. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Co and Y concentrations incorporation up to x=0.3. Meanwhile, the formed powders exhibited superparamagnetic characteristics. A high saturation magnetization (77.0 emu/g) was achieved for Ni0.5Zn0.2Co0.3Fe2O4 sample annealed at 1000 oC for 2 h.

Magnetization reversal processes in bonded magnets made from a mixture of Nd-(Fe,Co)-B and strontium ferrite powders

Science.gov (United States)

Dospial, M.; Plusa, D.

2013-03-01

Isotropic epoxy-resin bonded magnets composed of different amounts of Magnequench MQP-B and strontium ferrite powders have been prepared using a compression molding technique. The magnetic parameters for magnets with different amounts of strontium ferrite and magnetization reversal processes have been studied by the measurement of the initial magnetization curves, the major hysteresis loops measured at a field up to 14 T and sets of recoil loops. The enhancement of μ0MR and μ0HC is observed in comparison with the calculated values. From the recoil loops the field dependences of the reversible, irreversible and total magnetization components and the differential susceptibilities were derived. From the dependence of the irreversible magnetization component versus an applied field it was deduced that the main mechanism of magnetization reversal process is the pinning of domain walls in MQP-B and strontium ferrite grains. The interactions between the magnetic particles and grains have been examined by the analysis of the δM plot. The δM behavior of magnets with ferrite has been interpreted as being composed of magnetizing exchange coupling and demagnetizing dipolar interactions.

Chemical synthesis of spinel cobalt ferrite (CoFe2O4) nano-flakes for supercapacitor application

International Nuclear Information System (INIS)

Kumbhar, V.S.; Jagadale, A.D.; Shinde, N.M.; Lokhande, C.D.

2012-01-01

Highlights: ► The first time preparation of cobalt ferrite material in thin film form, using chemical method at low temperature. ► A nano-flake like morphology of the cobalt ferrite thin film. ► An application of the film as an electrode in supercapacitor cell. - Abstract: The present paper reveals the formation of cobalt ferrite (CoFe 2 O 4 ) thin film on stainless steel substrate by simple chemical route from an alkaline bath containing Co 2+ and Fe 2+ ions. The films are characterised for structural, surface morphological and FT-IR properties. The XRD and FT-IR studies revealed formation of single phase of CoFe 2 O 4 . The formation of nano-flakes-like morphology is observed from scanning electron microscope. The electrochemical behaviour of CoFe 2 O 4 film has been studied using cyclic voltammetry in 1 M NaOH electrolyte. The maximum specific capacitance of 366 F g −1 is obtained at the scan rate of 5 mV s −1 . Using AC impedance technique equivalent series resistance (ESR) value is found to be 1.1 Ω.

Magnetization reversal processes in bonded magnets made from a mixture of Nd–(Fe,Co)–B and strontium ferrite powders

International Nuclear Information System (INIS)

Dospial, M.; Plusa, D.

2013-01-01

Isotropic epoxy-resin bonded magnets composed of different amounts of Magnequench MQP-B and strontium ferrite powders have been prepared using a compression molding technique. The magnetic parameters for magnets with different amounts of strontium ferrite and magnetization reversal processes have been studied by the measurement of the initial magnetization curves, the major hysteresis loops measured at a field up to 14 T and sets of recoil loops. The enhancement of μ 0 M R and μ 0 H C is observed in comparison with the calculated values. From the recoil loops the field dependences of the reversible, irreversible and total magnetization components and the differential susceptibilities were derived. From the dependence of the irreversible magnetization component versus an applied field it was deduced that the main mechanism of magnetization reversal process is the pinning of domain walls in MQP-B and strontium ferrite grains. The interactions between the magnetic particles and grains have been examined by the analysis of the δM plot. The δM behavior of magnets with ferrite has been interpreted as being composed of magnetizing exchange coupling and demagnetizing dipolar interactions. - Highlights: ► SrFe 12 O 19 addition causes a decrease in the H c , J R and (BH) max . ► H c and J R changes are not in agreement with dilution law. ► Main mechanism of the coercivity is the pinning of domain walls. ► In both magnets from pure powders dominant role plays long range dipolar interactions. ► Dipolar and exchange interaction are simultaneously present in hybrids but the dipolar are weaker.

Room-temperature ferromagnetism in pure and Co doped CeO2 powders

International Nuclear Information System (INIS)

Wen Qiye; Zhang Huaiwu; Song Yuanqiang; Yang Qinghui; Zhu Hao; Xiao, John Q

2007-01-01

We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO 2 powder. An insulating nonmagnetic CeO 2 single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g -1 . However, the CeO 2 powder became paramagnetic after oxygen annealing, which strongly suggests an oxygen vacancy meditated FM ordering. Furthermore, by doping Co into CeO 2 powder the FM can significantly enhance through a F-centre exchange (FCE) coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. As the Co content increases, the FM of Co doped CeO 2 initially increases to a maximum 0.47 emu g -1 , and then degrades very quickly. The complex correlation between the Co content and saturation magnetization was well interpreted by supposing the coexistence of three subsets of Co ions in CeO 2 . Our results reveal that the large RT-FM observed in Co doped CeO 2 powder originates from a combination effect of oxygen vacancies and transition metal doping

Structural, morphological and magnetic properties of Eu-doped CoFe2O4 nano-ferrites

Directory of Open Access Journals (Sweden)

Aiman Zubair

Full Text Available Europium (Eu doped spinel cobalt ferrites having composition CoEuxFe2−xO4 where x = 0.00, 0.03, 0.06, 0.09, 0.12 were fabricated by co-precipitation route. In order to observe the phase development of the ferrite samples, thermo-gravimetric analysis was carried out. The synthesized samples were subjected to X-ray diffraction analysis for structural investigation. All the samples were found to constitute face centered cubic (FCC spinel structure belonging to Fd3m space group. Scanning electron microscopy revealed the formation of nanocrystalline grains with spherical shape. Energy dispersive X-ray spectra confirmed the presence of Co, Eu, Fe and O elements with no existence of any impurity. The magnetic hysteresis curves measured at room temperature exhibited ferrimagnetic behavior with maximum saturation magnetization (Ms of 65 emu/g and coercivity (Hc of 966 Oe. The origin of ferrimagnetism in Eu doped cobalt ferrites was discussed in detail with reverence to the allocation of Co2+ and Fe3+ ions within the spinel lattice. The overall coercivity was increased (944–966 Oe and magnetization was decreased (65–46 emu/g with the substitution of Eu3+. The enhancement of former is ascribed to the transition from multi domain to single domain state and reduction in lateral is attributed to the incorporation of nonmagnetic Eu ions for Fe, resulting in weak superexchange interactions. Keywords: Europium doped cobalt ferrites, Co-precipitation, X-ray diffraction, Scanning electron microscopy, Magnetic properties

Synthesis and characterization of nano silver ferrite composite

International Nuclear Information System (INIS)

Murthy, Y.L.N.; Kondala Rao, T.; Kasi viswanath, I.V.; Singh, Rajendra

2010-01-01

We report the synthesis of nano sized silver ferrite composite having the empirical formula AgFeO 2 by a co-precipitation method. The resulting powders are thin platelets, transparent and a rich ruby red in color in transmission. The X-ray diffraction (XRD) powder data consisted of only nine reflections, and the analysis showed the unit cell to be rhombohedral. The powders showed extensive XRD line broadening and the sizes of the crystals are calculated to be in the range 4-36.5 nm. The morphology of the silver ferrite composite studied using scanning electron microscope showed nano sized particles. The particle size is found to increase with increase in annealing temperature. The magnetic behavior, measured using a vibrating sample magnetometer, indicated a change from paramagnetic to ferromagnetic with increase in particle size.

Effects of Mg substitution on the structural and magnetic properties of Co0.5Ni0.5-x Mg x Fe2O4 nanoparticle ferrites

Science.gov (United States)

R, M. Rosnan; Z, Othaman; R, Hussin; Ali, A. Ati; Alireza, Samavati; Shadab, Dabagh; Samad, Zare

2016-04-01

In this study, nanocrystalline Co-Ni-Mg ferrite powders with composition Co0.5Ni0.5-x Mg x Fe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co-Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The XRD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of ˜ 32 nm to ˜ 36 nm. The lattice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of IR spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2+ substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from ˜ 57.35 emu/g to ˜ 61.49 emu/g and ˜ 603.26 Oe to ˜ 684.11 Oe (1 Oe = 79.5775 A·m-1), respectively. The higher values of magnetization M s and M r suggest that the optimum composition is Co0.5Ni0.4Mg0.1Fe2O4 that can be applied to high-density recording media and microwave devices. Project supported by the Ibnu Sina Institute for Scientific and Industrial Research, Physics Department of Universiti Teknologi Malaysia and the Ministry of Education Malaysia (Grant Nos. Q.J130000.2526.04H65).

Sol-Gel Synthesis and Characterization of Selected Transition Metal Nano-Ferrites

Directory of Open Access Journals (Sweden)

Aurelija GATELYTĖ

2011-09-01

Full Text Available In the present work, the sinterability and formation of nanosized yttrium iron garnet (Y3Fe5O12, yttrium perovskite ferrite (YFeO3, cobalt, nickel and zinc iron spinel (CoFe2O4, NiFe2O4 and ZnFe2O4, respectively powders by an aqueous sol-gel processes are investigated. The metal ions, generated by dissolving starting materials of transition metals in the diluted acetic acid were complexed by 1,2-ethanediol to obtain the precursors for the transition metal ferrite ceramics. The phase purity of synthesized nano-compounds was characterized by infrared spectroscopy (IR and powder X-ray diffraction analysis (XRD. The microstructural evolution and morphological features of obtained transition metal ferrites were studied by scanning electron microscopy (SEM.http://dx.doi.org/10.5755/j01.ms.17.3.598

Investigation of structural, magnetic and dielectric properties of Cr3+ substituted Cu0.75Co0.25Fe2-xO4 ferrite nanoparticles

Science.gov (United States)

Reddi, M. Sushma; Ramesh, M.; Sreenivasu, T.; Rao, G. S. N.; Samatha, K.

2018-05-01

Chromium doped Copper-Cobalt ferrite Nanoparticles were obtained by sol-gel auto-combustion method using citric acid as a fuel. The metal nitrates to citric acid ratio was taken as 1:1. The prepared powder of Cr3+ doped copper-cobalt ferrite nanoparticles is annealed at 600°C for 5 hrs and the same powder was used for characterization and investigations of structural properties. The phase composition, micro-structural, micro morphological and elemental analysis studies were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM) technique and energy dispersive spectroscopy (EDS). The FTIR spectra of these samples are recorded to ensure the presence of the metallic compounds. The average crystallite size obtained by Scherrer's formula is of the order of 19.28 nm to 32.92 nm. The dielectric properties are investigated as a function of frequency at room temperature using LCR-Q meter. The saturation magnetization (Ms) of the Cr3+ substituted Cu-Co ferrite sintered at 1100°C lies in the range of 5.4136-28.9943 emu/g, the coercivity (Hc) dropped desperately from about 2091.3-778.53Oe as Cr3+ composition increases from 0.0 to 0.25.

Synthesis, characterization and adsorption capability for Congo red of CoFe{sub 2}O{sub 4} ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Ding, Zui [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing 100029 (China); Wang, Wei, E-mail: wangwei@mail.buct.edu.cn [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing 100029 (China); Zhang, Yajun [Institute of Plastics Machinery and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Li, Feng [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Liu, J. Ping [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

2015-08-15

Highlights: • CoFe{sub 2}O{sub 4} ferrite nanoparticles are synthesized by an ethanol-assisted hydrothermal method. • Suitable amount of ethanol can reduce the particle size and increase BET surface area. • The introduction of ethanol leads to the cation redistribution. • Using ethanol/water mixed solution greatly enhances their adsorption capacity for CR dyes. - Abstract: CoFe{sub 2}O{sub 4} ferrite nanoparticles are synthesized by an ethanol-assisted hydrothermal method, where the ethanol is mixed with water as the solution. In this synthesis, a rapid mixing of reducible metal cations with reducing agent and a simultaneous reduction process take place in a colloid mill. Synthesized ferrite samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Raman spectroscopy. XRD patterns reveal the formation of CoFe{sub 2}O{sub 4} ferrites with single spinel phase. SEM and TEM images show that the as-synthesized samples are with narrow size distribution. Raman spectroscopy studies clearly indicate the cation distribution in nanosized particles. Here, it is worthy to note that, with increasing ethanol content in ethanol–water mixed solution, an obvious superparamagnetic behavior of as-synthesized nanoparticles at room temperature is observed. The adsorption capability of the as-synthesized ferrite nanoparticles for Congo Red (CR) is examined. Enhancement of adsorption capability for CR with adding ethanol as the mixing solution is shown. The adsorption mechanism is discussed. This investigation reveals that the composition of ethanol/water mixed solution has great effects on the microstructure and magnetic properties as well as adsorption capacity of Congo Red (CR) dye of the as-synthesized CoFe{sub 2}O{sub 4} ferrite samples.

Moessbauer characterization of calcium-ferrite oxides prepared by calcining Fe2O3 and CaO

International Nuclear Information System (INIS)

Hirabayashi, Daisuke; Sakai, Yoichi; Yoshikawa, Takeshi; Mochizuki, Kazuhiro; Kojima, Yoshihiro; Suzuki, Kenzi; Ohshita, Kazumasa; Watanabe, Yasuo

2006-01-01

Calcium ferrite oxides were prepared by calcining a mixture powder of iron- and calcium oxide. The 57 Fe-Moessbauer spectra of the calcium ferrites oxides were measured, revealing that the products should be Ca 2 Fe 2 O 5 and CaFe 2 O 4 , the ratio of which was dependent of the Fe/Ca atomic ratio of the mixture powder.

Studies on structural and magnetic properties of ternary cobalt magnesium zinc (CMZ) Co{sub 0.6-x}Mg{sub x}Zn{sub 0.4} Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6) ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kaur, Manpreet, E-mail: manpreetchem@pau.edu; Jain, Palak; Singh, Mandeep

2015-07-15

In this paper we report the variation in structural and magnetic properties of ternary ferrite nanoparticles (NPs) having stoichiometery Co{sub 0.6-x}Mg{sub x}Zn{sub 0.4} Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6) and pure spinel ferrites MFe{sub 2}O{sub 4} (M = Mg, Co). NPs with average particle diameter of 25–45 nm were synthesized employing self-propagating oxalyl dihydrazide - metal nitrate combustion method. The products were characterized using X-ray diffraction (XRD), Vibrating sample magnetometer (VSM), Transmission electron microscopy (TEM) and FT-IR spectroscopy. FT-IR spectral analysis revealed two bands centered at 560 and 440 cm{sup −1} for tetrahedral and octahedral metal–oxygen bond stretching. Zinc doping caused red shift in the frequency band of tetrahedral M−O stretching. XRD powder diffraction patterns confirmed the formation of spinel ferrite nanoparticles, expansion of the lattice on zinc doping and enhancement of spinel phase purity in the doped ferrites. Cobalt ferrite displayed lowering of the magnetic parameters on zinc doping which further decreased in ternary ferrites Co{sub 0.6-x}Mg{sub x}Zn{sub 0.4}Fe{sub 2}O{sub 4} on replacing cobalt ions with non-magnetic magnesium ions up to x = 0.4. At x = 0.6 reverse trend was observed and Ms was enhanced. Magnesium zinc ferrite Mg{sub 0.6}Zn{sub 0.4} Fe{sub 2}O{sub 4} with high value of Ms was obtained. Combustion process employed in the present studies serves as a low temperature facile route for the synthesis and structural analysis of ternary doped ferrite nanoparticles. - Highlights: • Ternary doped cobalt magnesium zinc ferrite nanoparticles are synthesized. • FT-IR displayed red shift in tetrahedral stretching band on Zinc doping. • Expansion of lattice and enhancement of spinel phase purity on zinc doping. • The variation in saturation magnetization (Ms) on doping is explained.

Electrical transport properties of CoMn0.2−xGaxFe1.8O4 ferrites using complex impedance spectroscopy

Directory of Open Access Journals (Sweden)

Chien-Yie Tsay

2016-05-01

Full Text Available In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2−xGaxFe1.8O4 (x=0, 0.1, and 0.2 prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z’ and the imaginary part (Z” of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

Optimization principles for preparation methods and properties of fine ferrite materials

Science.gov (United States)

Borisova, N. M.; Golubenko, Z. V.; Kuz'micheva, T. G.; Ol'khovik, L. P.; Shabatin, V. P.

1992-08-01

The paper is devoted to the problems of development of fine materials based on Ba-ferrite for vertical magnetic recording in particular. Taking an analogue — BaFe 12-2 xCo xTe xO 19 — we have optimized the melt co-precipitation method and shown a new opportunity to provide chemical homogeneity of microcrystallites by means of cryotechnology. Magnetic characteristics of the magnetic tape experimental sample for digital video recording are presented. A series of principles of consistent control of ferrite powder properties are formulated and illustrated with specific developments.

Study and characterization of the hexa ferrite Ba2Co2Fe12O22 (Co2-Y)

International Nuclear Information System (INIS)

Pires Junior, G.F.M.; Rodrigues, H.O.; Sales, J.C; Sancho, E.O.; Sombra, A.S.B.

2009-01-01

The objective of this work is to synthesize and to characterize the Hexaferrita Ba2Co 2 Fe 12 O 22 (Co 2 Y). The Y-type Hexaferrita (Co 2 Y) was prepared by the ceramic conventional method. The mixed powder by 1 h was calcined at 1050 deg C for 3 h. After of the calcination the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) using a diffractometer DMAXB of the Rigaku (Japan), CuK α radiation (λ=1.5405 angstrom) in a tax of 0.5 deg /min and linear band (20 deg at 80 deg) in 2θ. The characterization more detailed by XRD was made using the DBWS9807a program that uses the method of Rietveld for refinement of crystalline structures and confirmed the isolated attainment of the phase (Co 2 Y) with hexagonal crystalline structure (a = b = 5,8560 angstrom and c = 43,4977 angstrom; α = β = 90 deg and γ = 120 deg) with density and volume of the unit cell calculated of 5.45 g/cm 3 and 1292,3 angstrom respectively. (author)

Crystallographic and magnetic properties of the spinel-type ferrites ZnxCo1-xFe2O4 (0.0 ≤ x ≤ 0.75)

Science.gov (United States)

Azad, A. K.; Zakaria, A. K. M.; Jewel, Md. Yusuf; Khan, Abu Saeed; Yunus, S. M.; Kamal, I.; Datta, T. K.; Eriksson, S.-G.

2015-05-01

Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system ZnxCo1-xFe2O4 (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn2+, Co2+ and Fe3+ over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B sub-lattices and their exchange coupling.

Modification of the ASME code z-factor for circumferential surface crack in nuclear ferritic pipings

International Nuclear Information System (INIS)

Choi, Young Hwan; Chung, Yon Ki; Koh, Wan Young; Lee, Joung Bae

1996-01-01

The purpose of this paper is to modify the ASME Code Z-Factor, which is used in the evaluation of circumferential surface crack in nuclear ferritic pipings. The ASME Code Z-Factor is a load multiplier to compensate plastic load with elasto-plastic load. The current ASME Code Z-Factor underestimates pipe maximum load. In this study, the original SC. TNP method is modified first because the original SC. TNP method has a problem that the maximum allowable load predicted from the original SC. TNP method is slightly higher than that measured from the experiment. Then the new Z-Factor is developed using the modified SC. TNP method. The desirability of both the modified SC. TNP method and the new Z-Factor is examined using the experimental results for the circumferential surface crack in pipings. The results show that (1) the modified SC. TNP method is good for predicting the circumferential surface crack behavior in pipings, and (2) the Z-Factor obtained from the modified SC. TNP method well predicts the behavior of circumferential surface crack in ferritic pipings. 30 refs., 13 figs., 4 tabs. (author)

Conversion of MX Nitrides to Modified Z-Phase in 9-12%Cr Ferritic Steels

DEFF Research Database (Denmark)

Cipolla, Leonardo

for Z-phase formation was highlighted during the studies. Several 9-12%Cr commercial steels with prolonged high-temperature exposures have been investigated, too. The same mechanism of Z-phase formation observed in 12%Cr model alloys was identified in industrial 9-12%Cr steels after thousands of hours......The 9-12%Cr ferritic steels are extensively used in modern steam power plants at service temperature up to 620°C. Currently the best perform ing ferritic creep resistance steel is the ASTM Grade 92, whose high temperature strength has recently been assessed by European Creep Collaborative Committee...... in 2005 as 600°C/113MPa/10 5h. All previous attempts made in the last twenty years to develop ferritic steels for 650°C applications have failed due to the incapacity to combine the superior oxidation resistance, given by 12%Cr content, with excellent creep resistance of high-alloyed ferritic steels...

Preparation of cobalt-zinc ferrite (Co0.8Zn0.2Fe2O4) nanopowder via combustion method and investigation of its magnetic properties

International Nuclear Information System (INIS)

Yousefi, M.H.; Manouchehri, S.; Arab, A.; Mozaffari, M.; Amiri, Gh. R.; Amighian, J.

2010-01-01

Research highlights: → Cobalt-zinc ferrite was prepared by combustion method. → Properties of the sample were characterized by several techniques. → Curie temperature was determined to be 350 o C. -- Abstract: Cobalt-zinc ferrite (Co 0.8 Zn 0.2 Fe 2 O 4 ) was prepared by combustion method, using cobalt, zinc and iron nitrates. The crystallinity of the as-burnt powder was developed by annealing at 700 o C. Crystalline phase was investigated by XRD. Using Williamson-Hall method, the average crystallite sizes for nanoparticles were determined to be about 27 nm before and 37 nm after annealing, and residual stresses for annealed particles were omitted. The morphology of the annealed sample was investigated by TEM and the mean particle size was determined to be about 30 nm. The final stoichiometry of the sample after annealing showed good agreement with the initial stoichiometry using atomic absorption spectrometry. Magnetic properties of the annealed sample such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 70 emu/g, 14 emu/g, and 270 Oe, respectively. The Curie temperature of the sample was determined to be 350 o C using AC-susceptibility technique.

Synthesis, electrical and magnetic properties of sodium borosilicate glasses containing Co-ferrites nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Othman, H.A. [Department of Physics, Faculty of Science, Menoufia University, Shibin El-Kom 32511, Menoufia (Egypt); Eltabey, M.M. [Department of Basic Engineering Science, Faculty of Engineering, Menoufia University, Shibin El-Kom, Menoufia (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Ibrahim, Samia E.; El-Deen, L.M. Sharaf; Elkholy, M.M. [Department of Physics, Faculty of Science, Menoufia University, Shibin El-Kom 32511, Menoufia (Egypt)

2017-02-01

Co-ferrites nanoparticles that have been prepared by the co-precipitation method were added to sodium borosilicate (Na{sub 2}O–B{sub 2}O{sub 3}–SiO{sub 2}) glass matrix by the solid solution method and they were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and magnetization measurements. (XRD) revealed the formation of the Co-ferrite magnetic crystalline phase embedded in an amorphous matrix in all the samples. The investigated samples by (TEM) showed the formation of the cobalt ferrite nanoparticles with a spherical shape and highly monodispersed with an average size about 13 nm. IR data revealed that the BO{sub 3} and BO{sub 4} are the main structural units of these samples network. IR spectra of the investigated samples showed the characteristic vibration bands of Co-ferrite. Composition and frequency dependent dielectric properties of the prepared samples were measured at room temperature in the frequency range 100–100 kHz. The conductivity was found to increase with increasing cobalt ferrite content. The variations of conductivity and dielectric properties with frequency and composition were discussed. Magnetic hysteresis loops were traced at room temperature using VSM and values of saturation magnetization M{sub S} and coercive field H{sub C} were determined. The obtained results revealed that a ferrimagnetic behavior were observed and as Co-ferrite concentration increases the values of M{sub S} and H{sub C} increase from 2.84 to 8.79 (emu/g) and from 88.4 to 736.3 Oe, respectively.

Influence of starting powder milling on magnetic properties of Mn-Zn ferrite

Directory of Open Access Journals (Sweden)

Miodrag M. Milutinov

2017-06-01

Full Text Available In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200°C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss density, and hysteresis were measured using the modified watt-meter method. The complex permeability and hysteresis loop were modelled with a new model proposed in the paper. The core loss density was modelled with the Steinmetz empirical equation. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range 0.1-10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder.

Investigation of Structural, Morphological, Magnetic Properties and Biomedical applications of Cu2+ Substituted Uncoated Cobalt Ferrite Nanoparticles

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M. Margabandhu

Full Text Available ABSTRACT In the present work, Cu2+ substituted cobalt ferrite (Co1-xCuxFe2O4, x = 0, 0.3, 0.5, 0.7 and 1 magnetic nanopowders were synthesized via chemical co-precipitation method. The prepared powders were investigated by various characterization methods such as X-ray diffraction analysis (XRD, scanning electron microscope analysis (SEM, vibrating sample magnetometer analysis (VSM and fourier transform infrared spectroscopy analysis (FTIR. The XRD analysis reveals that the synthesized nanopowders possess single phase centred cubic spinel structure. The average crystallite size of the particles ranging from 27-49 nm was calculated by using Debye-scherrer formula. Magnetic properties of the synthesized magnetic nanoparticles are studied by using VSM. The VSM results shows the magnetic properties such as coercivity, magnetic retentivity decreases with increase in copper substitution whereas the saturation magnetization shows increment and decrement in accordance with Cu2+ substitution in cobalt ferrite nanoparticles. SEM analysis reveals the morphology of synthesized magnetic nanoparticles. FTIR spectra of Cu2+ substituted cobalt ferrite magnetic nanoparticles were recorded in the frequency range 4000-400cm-1. The spectrum shows the presence of water adsorption and metal oxygen bonds. The adhesion nature of Cu2+ substituted cobalt ferrite magnetic nanoparticles with bacteria in reviewed results indicates that the synthesized nanoparticles could be used in biotechnology and biomedical applications.

Characterization of M-type barium hexagonal ferrite-based wide band microwave absorber

Science.gov (United States)

Meshram, M. R.; Agrawal, Nawal K.; Sinha, Bharoti; Misra, P. S.

2004-05-01

This paper present the design, development and characterization of the hexagonal ferrite powder [BaCo 0.5δTi 0.5δMn 0.1Fe (11.87-δ)O 19] and [Ba(MnTi) δFe (12-2δ)O 19] at δ=1.6 as a microwave absorber. The hexagonal ferrite powder has been developed by dry attrition and sintering procedure. The developed ferrite powder 60% by weight has been mixed in epoxy resin to form a microwave-absorbing paint. This paint was coated on a conducting aluminum sheet to study the absorption characteristics of a linearly polarized TE wave at X band. The results for single- and two-layer microwave absorbers for different coating thicknesses have been reported. It has been found that it shows the broadband characteristics with minimum absorption of 8 dB from 8 to 12 GHz for a coating thickness of 2 mm.These paints are very useful in military applications such as RCS reduction, camouflaging of the target and prevention of EMI, etc.

Characterization of M-type barium hexagonal ferrite-based wide band microwave absorber

International Nuclear Information System (INIS)

Meshram, M.R.; Agrawal, Nawal K.; Sinha, Bharoti; Misra, P.S.

2004-01-01

This paper present the design, development and characterization of the hexagonal ferrite powder [BaCo 0.5δ Ti 0.5δ Mn 0.1 Fe (11.87-δ) O 19 ] and [Ba(MnTi) δ Fe (12-2δ) O 19 ] at δ=1.6 as a microwave absorber. The hexagonal ferrite powder has been developed by dry attrition and sintering procedure. The developed ferrite powder 60% by weight has been mixed in epoxy resin to form a microwave-absorbing paint. This paint was coated on a conducting aluminum sheet to study the absorption characteristics of a linearly polarized TE wave at X band. The results for single- and two-layer microwave absorbers for different coating thicknesses have been reported. It has been found that it shows the broadband characteristics with minimum absorption of 8 dB from 8 to 12 GHz for a coating thickness of 2 mm.These paints are very useful in military applications such as RCS reduction, camouflaging of the target and prevention of EMI, etc

TiO₂ Surface Coating of Mn-Zn Dopped Ferrites Study

DEFF Research Database (Denmark)

Solný, Tomáš; Ptacek, Petr; Másilko, Jiří

2016-01-01

This study deals with TiO2 coating of powder Mn-Zn ferrite in order to recieve photocatalytic layer on the top of these particles, forming core-shell catalyst. Powder catalysts are of great advance over the world due to the high surface area, considering the kinetics proceeds through heterogenous...... phase boundary catalysis. However their withdrawal from cleaning systems often requires energetically and economically demanding processes such as filtration and ultrafiltration. Since the ferrite is magnetic, the advantage of such formed core-shell photocatalyst is easibility of removing from...... photocatalytic decomposition system using external magnetic field. In this study the surface coating is performed, using Ti alkoxides mixtures with nanosized TiO2 particles and C and Au coating to form film layer of TiO2 on the surface of ferrite. XRD, SEM – EDS analyses are employed to study surface coating....

Microstructure and Mechanical Property of ODS Ferritic Steels Using Commercial Alloy Powders for High Temperature Service Applications

Energy Technology Data Exchange (ETDEWEB)

Noh, Sanghoon; Choi, Byoung-Kwon; Kang, Suk Hoon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Oxide dispersion strengthening (ODS) is one of the promising ways to improve the mechanical property at high temperatures. This is mainly attributed to uniformly distributed nano-oxide particle with a high density, which is extremely stable at the high temperature and acts as effective obstacles when the dislocations are moving. In this study, as a preliminary examination to develop the advanced structural materials for high temperature service applications, ODS ferritic steels were fabricated using commercial alloy powders and their microstructural and mechanical properties were investigated. In this study, ODS ferritic steels were fabricated using commercial stainless steel 430L powder and their microstructures and mechanical properties were investigated. Morphology of micro-grains and oxide particles were significantly changed by the addition of minor alloying elements such as Ti, Zr, and Hf. The ODS ferritic steel with Zr and Hf additions showed ultra-fine grains with fine complex oxide particles. The oxide particles were uniformly located in grains and on the grain boundaries. This led to higher hardness than ODS ferritic steel with Ti addition.

Influence of CaCO3 and SiO2 additives on magnetic properties of M-type Sr ferrites

Science.gov (United States)

Huang, Ching-Chien; Jiang, Ai-Hua; Hung, Yung-Hsiung; Liou, Ching-Hsuan; Wang, Yi-Chen; Lee, Chi-Ping; Hung, Tong-Yin; Shaw, Chun-Chung; Kuo, Ming-Feng; Cheng, Chun-Hu

2018-04-01

An experiment was carried out to investigate the influence of CaCO3 and SiO2 additives on the magnetic and physical properties of M-type Sr ferrites by changing experimental parameters such as the additive composition and Ca/Si ratio. Specimens were prepared by conventional ceramic techniques. It was found that the magnetic properties (Br = 4.42 kG, iHc = 3.32 kOe and (BH)max = 4.863 MGOe) were considerably improved upon adding CaCO3 = 1.1% and SiO2 = 0.4 wt% together with Co3O4, and the mechanical properties thereof were acceptable for motor applications. It was revealed that CaCO3 and SiO2 additives led to an upswing in the magnetic properties via the enhancement of uniform grain growth, particle alignment, and the densification of Sr ferrite.

Development of cobalt ferrite powder preparation employing the sol-gel technique and its structural characterization

International Nuclear Information System (INIS)

Sajjia, M.; Oubaha, M.; Prescott, T.; Olabi, A.G.

2010-01-01

Research highlights: This work focuses on the sol-gel process and the effects that the initial parameters have on the final product, which is the cobalt ferrite powder, in addition to the heat treatment. Particular interest is devoted to understand how the crosslinker and the chelating agent work and affect the final product. - Abstract: This work focuses on the development of a method to make cobalt ferrite powder using the sol-gel process. A particular emphasis is devoted to the understanding of the role of the chemical parameters involved in the sol-gel technique, and of the heat treatment on the structures and morphologies of the materials obtained. Several samples of cobalt ferrite powder were obtained by varying the initial parameters of the process in addition to the heat treatment temperature. X-ray diffraction and scanning electron microscopy were used to identify the structure and morphology of samples demonstrating the influence of the initial parameters. DTA/TGA was carried out on two standard samples to identify important reaction temperatures during the heat treatment. The average size of the nano crystallites was estimated for a sample by the full width at half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak. It has been found that the chelating agent and the crosslinker have a critical influence on the resultant structure, the particle size and the particle size distribution.

Characterization of Ni ferrites powders prepared by plasma arc discharge process

Science.gov (United States)

Safari, A.; Gheisari, Kh.; Farbod, M.

2017-01-01

The aim of this work was to synthesize a single-phase spinel structure from a mixture of zinc, iron and nickel powders by plasma arc discharge method. A mixture of zinc, iron and nickel powders with the appropriate molar ratio was prepared and formed into a cylindrical shape. The synthesis process was performed in air, oxygen and argon atmospheres with the applied arc current of 400 A and pressure of 1 atm. After establishing an arc between the electrodes, the produced powders were collected and their structure and magnetic properties were examined by XRD and VSM, respectively. ZnO as an impurity was appeared in the as-produced powders owing to the high reactivity of zinc atoms, preventing the formation of Ni-Zn ferrite. A pure spinel structure with the highest saturation magnetization (43.8 emu/g) was observed as zinc powders removed completely from the initial mixture. Morphological evaluations using field emission scanning electron microscopy showed that the mean size of fabricated nanoparticles was in the range 100-200 nm and was dependent on the production conditions.

Investigation of structural and magnetic properties of Zr-Co doped nickel ferrite nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Ali, Rajjab [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Manzoor, Alina [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Department of Physics, Government College University, Faisalabad 38000 (Pakistan); Shahid, Muhammad [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Haider, Sajjad [Chemical Engineering Department, College of Engineering, King Saud University, Riyadh 11421 (Saudi Arabia); Malik, Abdul Sattar [Department of Electrical Engineering, University College of Engineering and Technology, Bahauddin Zakariya University, Multan 60800 Pakistan (Pakistan); Sher, Muhammad [Department of Chemistry, University of Sargodha, Sargodha 40100 (Pakistan); Shakir, Imran [Sustainable Energy Technologies (SET) Center, College of Engineering, King Saud University, PO-BOX 800, Riyadh 11421 (Saudi Arabia); FarooqWarsi, Muhammad, E-mail: farooq.warsi@iub.edu.pk [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

2017-05-01

Nano-sized Zr-Co doped nickel ferrites with nominal composition, NiZr{sub x}Co{sub x}Fe{sub 2-2x}O{sub 4} (x=0.0, 0.2, 0.4, 0.6, 0.8) were synthesized using the micro-emulsion route. The structural elucidation of the synthesized materials was carried out by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD analysis confirmed face centered cubic (FCC) structure of all compositions of NiZr{sub x}Co{sub x}Fe{sub 2-2x}O{sub 4} nanocrystallites. Crystallite size was calculated by Scherrer's formula found in the range 10–15 nm. The variation in lattice parameter as determined by XRD data agreed with size variation of host (Fe{sup 3+}) and guest (Zr{sup 4+} and Co{sup 2+}) cations. FTIR spectra of doped NiFe{sub 2}O{sub 4} exhibited the typical octahedral bands at 528.4 cm{sup −1} which is the characteristic feature of spinel structure of spinel ferrites. The characterized spinel NiZr{sub x}Co{sub x}Fe{sub 2-2x}O{sub 4} nano-ferrites were evaluated for their potential applications by magnetic hysteresis loops and dielectric measurements. The value of saturation magnetization (M{sub s}) decreased from 47.9 to 13.09 emu/g up to x=0.8 with ups and downs fluctuations in between x=0.0 to x=0.8. The high values of Ms of some compositions predicted the potential applications in high density perpendicular recording media and microwave devices. The frequency dependent behavior of permittivity (ε') is recorded and discussed with the help of hopping mechanism of both holes and electrons. The dielectric and magnetic data of NiZr{sub x}Co{sub x}Fe{sub 2-2x}O{sub 4} nano-ferrites suggested the potential applications of these ferrite nanoparticles in high frequency and magnetic data storage devices fabrication. - Graphical abstract: Zr-Co doped nickel nano-ferrites were prepared via micro-emulsion method. The crystallite size calculated by scherrer's formula lie in the range 10–15 nm. The saturation magnetization decreases from 47

Processing, structure and magnetic properties correlation in co-precipitated Ca-ferrite

Energy Technology Data Exchange (ETDEWEB)

Abasht, Behzad, E-mail: abasht@gmail.com [Space Thruster Research Institute, Iranian Space Research Center, Tabriz (Iran, Islamic Republic of); Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Beitollahi, Ali; Mirkazemi, Seyyed Mohammad [Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

2016-12-15

La-substituted hexagonal calcium ferrite, Ca{sub 1−X}La{sub X}Fe{sub 12}O{sub 19} (x varies from 0 to 0.6 with the step of 0.2), was synthesized by applying co-precipitation method, in which the molar ratio of Fe{sup 3+}/(Ca{sup 2+}+La{sup 2+}) was 11. The ferrite precursors were prepared from aqueous solution of calcium nitrate, ferric nitrate and lanthanum nitrate by co-precipitation of calcium, iron and lanthanum ions by using an aqueous base of sodium hydroxide (1.5 M) at the pH of 14 and at room temperature. These precursors were calcinated with different amount of La at different temperature of 700, 1100 and 1200 °C for constant calcination time of 1 h in a static air atmosphere. Some tests such as simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were carried out to investigate the thermal behavior, crystallographic properties, morphology and magnetic properties of the precursor powders which were calcinated at different temperatures. The powder XRD patterns of samples which consisted of La as dopant and were calcinated at 1200 °C for 1 h, indicates the formation of calcium hexaferrite and also α-Fe{sub 2}O{sub 3} besides Magnetoplumbite-phase (M-phase). However, the results showed that CaFe{sub 4}O{sub 7} and α-Fe{sub 2}O{sub 3} phases were formed in the sample with the same condition but without using any dopant. The results of SEM showed that the calcium hexaferrite particle were regular hexagonal platelets with the size range of 1–2 µm. The magnetic properties such as maximum magnetization (M{sub Max}), remanent magnetization (M{sub r}) and coercivity (H{sub c}) were measured from the hysteresis loops. Low values of coercive field (16.3 kA m{sup −1}) and maximum magnetization (50.6 A m{sup 2} kg{sup −1}) were obtained from calcium hexaferrite particle in optimum amount of La (X=0.4) which calcinated at the temperature of 1200 °C. - Highlights: • In this

CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

Directory of Open Access Journals (Sweden)

T. Ramesh

2016-01-01

Full Text Available Cobalt ferrite (CoFe2O4 and silica (SiO2 nanopowders have been prepared by the microwave hydrothermal (M-H method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The (100-x (CoFe2O4 + xSiO2 (where x = 0%, 10%, 20%, and 30% composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD, Fourier transformation infrared (FTIR spectra, and scanning electron microscopy (SEM, respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.

Structural and magnetic properties of nano-sized NiCuZn ferrites synthesized by co-precipitation method with ultrasound irradiation

Energy Technology Data Exchange (ETDEWEB)

Harzali, Hassen, E-mail: harzali@mines-albi.fr [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Saida, Fairouz; Marzouki, Arij; Megriche, Adel [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Baillon, Fabien; Espitalier, Fabienne [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi CT cedex 09 (France); Mgaidi, Arbi [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Taibah University, Faculty of Sciences & art, Al Ula (Saudi Arabia)

2016-12-01

Sonochemically assisted co-precipitation has been used to prepare nano-sized Ni–Cu–Zn-ferrite powders. A suspension of constituent hydroxides was ultrasonically irradiated for various times at different temperatures with high intensity ultrasound radiation using a direct immersion titanium horn. Structural and magnetic properties were investigated using X-diffraction (XRD), FT-IR spectroscopy, transmission electron microscopy (TEM), Nitrogen adsorption at 77 K (BET) and Vibrating sample magnetometer (VSM). Preliminary experimental results relative to optimal parameters showed that reaction time t=2 h, temperature θ=90 °C and dissipated Power P{sub diss}=46.27 W. At these conditions, this work shows the formation of nanocrystalline single-phase structure with particle size 10–25 nm. Also, ours magnetic measurements proved that the sonochemistry method has a great influence on enhancing the magnetic properties of the ferrite. - Highlights: • Coprecipitation experiments were carried out with ultrasound. • The spinel ferrite NiCuZn was perfectly synthesized by ultrasound. • The saturation magnetization and crystals size are found to be correlated as the dissipated power was varied.

Structural and magnetic properties of nano-sized NiCuZn ferrites synthesized by co-precipitation method with ultrasound irradiation

International Nuclear Information System (INIS)

Harzali, Hassen; Saida, Fairouz; Marzouki, Arij; Megriche, Adel; Baillon, Fabien; Espitalier, Fabienne; Mgaidi, Arbi

2016-01-01

Sonochemically assisted co-precipitation has been used to prepare nano-sized Ni–Cu–Zn-ferrite powders. A suspension of constituent hydroxides was ultrasonically irradiated for various times at different temperatures with high intensity ultrasound radiation using a direct immersion titanium horn. Structural and magnetic properties were investigated using X-diffraction (XRD), FT-IR spectroscopy, transmission electron microscopy (TEM), Nitrogen adsorption at 77 K (BET) and Vibrating sample magnetometer (VSM). Preliminary experimental results relative to optimal parameters showed that reaction time t=2 h, temperature θ=90 °C and dissipated Power P_d_i_s_s=46.27 W. At these conditions, this work shows the formation of nanocrystalline single-phase structure with particle size 10–25 nm. Also, ours magnetic measurements proved that the sonochemistry method has a great influence on enhancing the magnetic properties of the ferrite. - Highlights: • Coprecipitation experiments were carried out with ultrasound. • The spinel ferrite NiCuZn was perfectly synthesized by ultrasound. • The saturation magnetization and crystals size are found to be correlated as the dissipated power was varied.

and aluminum-substituted cobalt ferrite prepared by co-precipitation ...

Indian Academy of Sciences (India)

Spinal ferrites having the general formula Co1-ZnFe2-AlO4 ( = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were prepared using the wet chemical co-operation technique. The samples were annealed at 800°C for 12 h and were studied by means of X-ray diffraction, magnetization and low field AC susceptibility measurements.

Preparation, characterization and application of nanosized copper ferrite photocatalysts for dye degradation under UV irradiation

Energy Technology Data Exchange (ETDEWEB)

Zaharieva, Katerina, E-mail: zaharieva@ic.bas.bg [Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 11, 1113 Sofia (Bulgaria); Rives, Vicente, E-mail: vrives@usal.es [GIR-QUESCAT, Dpto. Química Inorgánica, Universidad de Salamanca, 37008 Salamanca (Spain); Tsvetkov, Martin, E-mail: mptsvetkov@gmail.com [Faculty of Chemistry and Pharmacy, St. Kliment Ohridski University of Sofia, 1 J. Bourchier Blvd., 1164 Sofia (Bulgaria); Cherkezova-Zheleva, Zara, E-mail: zzhel@ic.bas.bg [Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 11, 1113 Sofia (Bulgaria); Kunev, Boris, E-mail: bkunev@ic.bas.bg [Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 11, 1113 Sofia (Bulgaria); Trujillano, Raquel, E-mail: rakel@usal.es [GIR-QUESCAT, Dpto. Química Inorgánica, Universidad de Salamanca, 37008 Salamanca (Spain); Mitov, Ivan, E-mail: mitov@ic.bas.bg [Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Block 11, 1113 Sofia (Bulgaria); Milanova, Maria, E-mail: nhmm@wmail.chem.uni-sofia.bg [Faculty of Chemistry and Pharmacy, St. Kliment Ohridski University of Sofia, 1 J. Bourchier Blvd., 1164 Sofia (Bulgaria)

2015-06-15

Nanosized copper ferrite-type materials (Cu{sub x}Fe{sub 3–x}O{sub 4}, 0 ≤ x ≤ 1) have been prepared by combination of co-precipitation and mechanochemical activation and/or thermal treatment. The crystalline structure and morphology of the obtained ferrite nanopowders have been characterized by different instrumental methods, such as Powder X-ray diffraction (PXRD), Mössbauer and FT-IR spectroscopies, specific surface area and porosity measurements, thermal analyses (Differential Thermal Analysis and Thermogravimetric Analysis) and Temperature-Programmed Reduction. The average crystallite size of copper ferrites ranged between 7.8 and 14.7 nm and show a superparamagnetic and collective magnetic excitations nature. The photocatalytic decolorization of Malachite green oxalate under different UV illumination intervals was examined using these copper ferrites as photocatalysts. The results indicate that the prepared nanostructured copper ferrites showed enhanced photocatalytic activity and amount adsorbed Malachite Green dye. The co-precipitated nanosized copper ferrite powder with a low content of copper metal ions in a magnetite host structure (Cu{sub 0.25}Fe{sub 2.75}O{sub 4}) showed an apparent pseudo-first-order rate constant 15.4 × 10{sup −3} min{sup −1} and an amount adsorbed Malachite Green as model organic dye pollutant per 1 g catalyst of 33.4 ppm/g after the dark period. The results confirm that the copper ferrites can be suitable for photocatalytic treatment of wastewaters containing organic dyes. The new aspect of presented investigations is to study the influence of different degree of incorporation of copper ions into the magnetite host structure and preparation methods on the photocatalytic properties of nanosized copper ferrite materials and obtaining of potential photocatalyst (Cu{sub 0.25}Fe{sub 2.75}O{sub 4}) with higher photocatalytic activity (15.4 × 10{sup −3} min{sup −1}) than that of the standard referent Degussa P25 (12 × 10

Preparation, characterization and application of nanosized copper ferrite photocatalysts for dye degradation under UV irradiation

International Nuclear Information System (INIS)

Zaharieva, Katerina; Rives, Vicente; Tsvetkov, Martin; Cherkezova-Zheleva, Zara; Kunev, Boris; Trujillano, Raquel; Mitov, Ivan; Milanova, Maria

2015-01-01

Nanosized copper ferrite-type materials (Cu x Fe 3–x O 4 , 0 ≤ x ≤ 1) have been prepared by combination of co-precipitation and mechanochemical activation and/or thermal treatment. The crystalline structure and morphology of the obtained ferrite nanopowders have been characterized by different instrumental methods, such as Powder X-ray diffraction (PXRD), Mössbauer and FT-IR spectroscopies, specific surface area and porosity measurements, thermal analyses (Differential Thermal Analysis and Thermogravimetric Analysis) and Temperature-Programmed Reduction. The average crystallite size of copper ferrites ranged between 7.8 and 14.7 nm and show a superparamagnetic and collective magnetic excitations nature. The photocatalytic decolorization of Malachite green oxalate under different UV illumination intervals was examined using these copper ferrites as photocatalysts. The results indicate that the prepared nanostructured copper ferrites showed enhanced photocatalytic activity and amount adsorbed Malachite Green dye. The co-precipitated nanosized copper ferrite powder with a low content of copper metal ions in a magnetite host structure (Cu 0.25 Fe 2.75 O 4 ) showed an apparent pseudo-first-order rate constant 15.4 × 10 −3 min −1 and an amount adsorbed Malachite Green as model organic dye pollutant per 1 g catalyst of 33.4 ppm/g after the dark period. The results confirm that the copper ferrites can be suitable for photocatalytic treatment of wastewaters containing organic dyes. The new aspect of presented investigations is to study the influence of different degree of incorporation of copper ions into the magnetite host structure and preparation methods on the photocatalytic properties of nanosized copper ferrite materials and obtaining of potential photocatalyst (Cu 0.25 Fe 2.75 O 4 ) with higher photocatalytic activity (15.4 × 10 −3 min −1 ) than that of the standard referent Degussa P25 (12 × 10 −3 min −1 ) for degradation of organic dye

Structural and magnetic properties of Co-substituted NiCu ferrite nanopowders

Energy Technology Data Exchange (ETDEWEB)

Li, Le-Zhong, E-mail: lezhongli@cuit.edu.cn; Zhong, Xiao-Xi; Wang, Rui; Tu, Xiao-Qiang; Peng, Long

2017-07-01

Highlights: • There are Fe{sub 2}O{sub 3} and CuO impurity phases when x ≤ 0.10. • The saturation magnetization and coercivity monotonically increase with the increase of Co substitution. • The anisotropy constant increases with the increase of Co substitution. • The calculated and observed values of magneton number are in close agreement with each other. - Abstract: Co-substituted NiCu ferrite nanopowders with the chemical formula Ni{sub 0.5−x}Cu{sub 0.5−x}Co{sub 2x}Fe{sub 2}O{sub 4} (0 ≤ x ≤ 0.50) were synthesized by sol-gel auto-combustion method. The effects of Co substitution on the cation distribution, structural and magnetic properties of the NiCu ferrite nanopowders have been investigated. Differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) measurements were used to characterize the chemical, structural and magnetic properties of the ferrite nanopowders, respectively. The DTA-TG results indicate that there are three steps of the combustion process. XRD results indicate that there are Fe{sub 2}O{sub 3} and CuO impurity phases when x ≤ 0.10. Furthermore, the lattice parameter increases, and the X-ray density and the average crystallite size decrease with increasing Co substitution. And the obtained particle size from TEM image is in very good agreement with the average crystallite size estimated by XRD measurements. The saturation magnetization and coercivity monotonically increase with the increase of Co substitution. The increase of the saturation magnetization is due to the substitution of Ni{sup 2+} and Cu{sup 2+} ions with lower magnetic moment by Co{sup 2+} ions with higher magnetic moment on the octahedral sites. And the increase of the coercivity is mainly due to the increase of magnetocrystalline anisotropy energy.

Preparation and electromagnetic properties of low-temperature sintered ferroelectric-ferrite composite ceramics

International Nuclear Information System (INIS)

Yue Zhenxing; Chen Shaofeng; Qi Xiwei; Gui Zhilun; Li Longtu

2004-01-01

For the purpose of multilayer chip EMI filters, the new ferroelectric-ferrite composite ceramics were prepared by mixing PMZNT relaxor ferroelectric powder with composition of 0.85Pb(Mg 1/3 Nb 2/3 )O 3 -0.1Pb(Ni 1/3 Nb 2/3 )O 3 -0.05PbTiO 3 and NiCuZn ferrite powder with composition of (Ni 0.20 Cu 0.20 Zn 0.60 )O(Fe 2 O 3 ) 0.97 at low sintering temperatures. A small amount of Bi 2 O 3 was added to low sintering temperature. Consequently, the dense composite ceramics were obtained at relative low sintering temperatures, which were lower than 940 deg. C. The X-ray diffractometer (XRD) identifications showed that the sintered ceramics retained the presence of distinct ferroelectric and ferrite phases. The sintering studies and scanning electron microscope (SEM) observations revealed that the co-existed two phases affect the sintering behavior and grain growth of components. The electromagnetic properties, such as dielectric constant and initial permeability, change continuously between those of two components. Thus, the low-temperature sintered ferroelectric-ferrite composite ceramics with tunable electromagnetic properties were prepared by adjusting the relative content of two components. These materials can be used for multilayer chip EMI filters with various properties

Sol-gel synthesis and structure of La2O3–CoO–SiO2 powders

Directory of Open Access Journals (Sweden)

Lachezar Radev

2008-12-01

Full Text Available LaCoO3 powders are studied because they exhibit interesting electrical, magnetic and catalytic properties. In this paper, new synthesized La2O3-CoO-SiO2 powders with different quantity of silica were prepared via solgel method in aqua media, starting from metal nitrates with different chelating agents. The relation between the reaction in solution, crystallization pathway and morphology were discussed. In LaCoO3-SiO2 powders, depending on the content of SiO2 and the treatment temperature (700–1100°C, different crystalline phases (LaCoO3, Co2SiO4 and La9.31(SiO46O2 were observed with the crystallite sizes ranging from 50 to 100 nm. It was proved that chemical composition and nature of used additives has influence on the phase formation and structure of obtained nanomaterials.

and aluminum-substituted cobalt ferrite prepared by co-precipitation

Indian Academy of Sciences (India)

Structural and magnetic properties of zinc- and aluminum-substituted cobalt ferrite prepared by co-precipitation method. S T ALONE1,∗ and K M JADHAV2. 1Shiv Chhatrapati College, Aurangabad 431 004, India. 2Department of Physics, Dr. B. A. Marathwada University, Aurangabad 431 004, India. ∗Corresponding author.

Preparation of hollow microspheres of Ce{sup 3+} doped NiCo ferrite with high microwave absorbing performance

Energy Technology Data Exchange (ETDEWEB)

Duan, Hong-zhen, E-mail: duanhz2000@163.com; Zhou, Fang-ling; Cheng, Xia; Chen, Guo-hong; Li, Qiao-ling

2017-02-15

Hollow microspheres of Ce{sup 3+} doped NiCo-ferrites were synthesized by template-based-deposition and surface reaction method with carbon sphere as the template. The phase structure, morphology, magnetic properties and wave absorbing properties of the sample were characterized by X-ray powder diffraction(XRD), Scanning electronic microscopy(SEM), Vibration sample magnetometer (VSM) and a network vector analyzer (NVA), respectively. The results indicated that the particle size of the carbon sphere sample prepared by hydrothermal method was about 0.5 µm and the particle size of the Ni{sub 0.5}Co{sub 0.5}Fe{sub 2}O{sub 4} sample prepared by template-based method was about 300 nm. The influence of the amount of rare earth element on the magnetic and absorbing properties of sample was studied. The saturation magnetization and coercivity decreased gradually with the increase of the content of Ce. When the content of Ce was 0.02, the maximal saturation magnetization value and coercivity was 75.72 emu• g{sup −1} and 789.88 Oe, respectively. The associated ferrite hollow spheres have good absorbing performance, and the return loss value was −18.8 dB at 5500 MHz. - Highlights: • Hollow microspheres of Ce{sup 3+} doped NiCo-ferrites were synthesized by template-based-deposition and surface reaction method. • The influence of rare earth Ce{sup 3+} on the magnetic and absorbing properties of sample was studied. • When the content of Ce was 0.02, the maximal saturation magnetization value and coercivity was 75.72 emu• g{sup −1} and 789.88 Oe, respectively.

Synthesis of Nano-Structured La0.6Sr0.4Co0.2Fe0.8O3 Perovskite by Co-Precipitation Method

Directory of Open Access Journals (Sweden)

Ebrahim Mostafavi

2015-06-01

Full Text Available Nano-structured lanthanum strontium cobalt ferrite, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF, was successfully synthesized via co-precipitation method using metal nitrates as starting materials. Effects of precipitating agent and calcination temperature on the phase composition and morphology of synthesized powders were systematically studied using X-ray diffraction (XRD and field emission scanning electron microscopy (FESEM, respectively. XRD analysis revealed that a single phase La0.6Sr0.4Co0.2Fe0.8O3 perovskite was obtained in the processed sample using ammonium carbonate as precipitating agent with a NH4+/NO3-molar ratio of 2 after calcination at 1000C for 1 h. The phase composition of products was also affected by changing pH values. Moreover, using sodium hydroxide as a precipitant resulted in a mixture of La0.6Sr0.4Co0.2Fe0.8O3 and cobalt ferrite (CoFe2O4 phases. Careless washing of the precursors can also led to the formation of mixed phase after calcination of final powders. Mean crystallite size of the obtained powders was not noticeably affected by varying calcination temperature from 900 to 1050C and remained almost the same at 10 nm, however increasing calcination temperature to 1100C resulted in sharp structural coarsening. FESEM studies demonstrate that relatively uniform particles with mean particle size of 90 nm were obtained in the sample processed with a NH4+/NO3- molar ratio of 2 after calcination at 1000C for 1 h.

FTIR and structural properties of co-precipitated cobalt ferrite nano particles

International Nuclear Information System (INIS)

Hutamaningtyas, E.; Utari; Suharyana; Purnama, B.; Wijayanta, A. T.

2016-01-01

The FTIR and structural properties in co-precipitated cobalt ferrite (CoFe 2 O 4 ) nanoparticles are discussed in this paper. The synthesis was conducted at temperatures of 75°C and 95°C following post annealing at 1200°C for 5 hours. Other modification samples were synthesis at temperature of 95°C and then annealing at temperature of 1000°C and 1200°C for 5 hours. For both modification of synthesis and annealing temperature, FTIR result showed a metal oxide at a wave number of 590 cm -1 which indicated cobalt ferrite nanoparticles. The crystalline structure was confirmed using x-ray diffraction that the high purity of cobalt ferrite was realized. Calculation of the cation distribution by using comparison I 220 /I 222 and I 422 /I 222 show that the synthesis and annealing temperature succesfully modify cation occupy the site octahedral and tetrahedral. (paper)

Neutron depolarization in compressed ferrite powders

International Nuclear Information System (INIS)

Rekveldt, M.Th.; Kraan, W.H.

1976-01-01

The polarization change of a polarized neutron beam after transmission through a partly magnetized ferromagnetic material can be described by a (3x3) depolarization matrix. This matrix can be expressed in terms of domain quantities such as the reduced mean magnetization M, the mean domain size delta and the mean square direction cosinus γsub(y) of the inner magnetization within the domain, and can be used for measuring magnetic properties of ferromagnetic materials. In the underlying depolarization theory it is assumed that no correlations exist between the direction of the spontaneous magnetization Bs in neighbouring domains, and between the direction of Bs and the individual domain sizes. In order to extend the measuring method for ferromagnetic materials, measurements have been made with different compressed ferrite powders assuming that the mean domain size is equal to the mean particle size. The neutron depolarization matrix is measured as a function of an alternative external magnetic field and interpreted in terms of m, γsub(y), and delta. The possibilities and limitations of the measuring method are discussed

Synthesis, structural investigation and magnetic properties of Zn2+ substituted cobalt ferrite nanoparticles prepared by the sol–gel auto-combustion technique

International Nuclear Information System (INIS)

Raut, A.V.; Barkule, R.S.; Shengule, D.R.; Jadhav, K.M.

2014-01-01

Structural morphology and magnetic properties of the Co 1−x Zn x Fe 2 O 4 (0.0≤x≥1.0) spinel ferrite system synthesized by the sol–gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co–Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol–gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co–Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn 2+ content in cobalt ferrite nanoparticles is followed by decrease in n B , M s and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature. - Highlights: • Co–Zn nanoparticles are prepared by sol–gel auto-combustion method. • Structural properties were characterized by XRD, SEM, and FTIR. • Compositional stoichiometry was confirmed by EDAX analysis. • Magnetic parameters were measured by the pulse field hysteresis loop technique

Tri-metallic ferrite oxygen carriers for chemical looping combustion

Science.gov (United States)

Siriwardane, Ranjani V.; Fan, Yueying

2017-10-25

The disclosure provides a tri-metallic ferrite oxygen carrier for the chemical looping combustion of carbonaceous fuels. The tri-metallic ferrite oxygen carrier comprises Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta., where Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta. is a chemical composition. Generally, 0.5.ltoreq.x.ltoreq.2.0, 0.2.ltoreq.y.ltoreq.2.5, and 0.2.ltoreq.z.ltoreq.2.5, and in some embodiments, 0.8.ltoreq.x.ltoreq.1.2, y.ltoreq.1.2, and z.gtoreq.0.8. The tri-metallic ferrite oxygen carrier may be used in various applications for the combustion of carbonaceous fuels, including as an oxygen carrier for chemical looping combustion.

Distribution of cations in nanosize and bulk Co-Zn ferrites

Czech Academy of Sciences Publication Activity Database

Veverka, Miroslav; Jirák, Zdeněk; Kaman, Ondřej; Knížek, Karel; Maryško, Miroslav; Pollert, Emil; Závěta, K.; Lančok, Adriana; Dlouhá, M.; Vratislav, S.

2011-01-01

Roč. 22, č. 34 (2011), 345701/1-345701/7 ISSN 0957-4484 R&D Projects: GA ČR GAP204/10/0035; GA ČR(CZ) GAP108/11/0807 Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z40320502 Keywords : cobalt zinc ferrites * nanoparticles distribution of cations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.979, year: 2011

Preparation of zinc ferrite nano powders by high energy wet-milling method and investigation of Crystallites size variation during this process

International Nuclear Information System (INIS)

Masoudi, H.; Aftabi, A.; Mozafari, M.; Amighian, J.

2007-01-01

In this research work ZnFe 2 O 4 nano powders were prepared by high-energy wet-milling process, using metallic Fe and Zn powders. The process was investigated by XRD technique. 10% of the zinc ferrite was formed after 10 h milling. The as-milled sample was annealed at 500, 550 and 600 d egree C . Ultimately a single sample was obtained at 600 d egree C . Using sherrer's formula, the mean crystallite size of the as-milled and annealed powders were calculated. These were in the range of 17.9 to 20.4 nm.

Development of novel exchange spring magnet by employing nanocomposites of CoFe_2O_4 and CoFe_2

International Nuclear Information System (INIS)

Safi, Rohollah; Ghasemi, Ali; Shoja-Razavi, Reza; Tavoosi, Majid

2016-01-01

CoFe_2O_4−CoFe2 hard–soft nanocomposites were prepared via reduction of the cobalt ferrite CoFe_2O_4 in hydrogen atmosphere at different temperature. The structure and the room temperature magnetization of the samples were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization of the nanocomposite powders increases by reduction temperature while their coercivity decreases. The highest M_r/M_s ratio of 0.52 was obtained for sample reduced at 550 °C. Single smooth hysteresis loops of nanocomposites show that these nanocomposites behave as the single-phase materials. This result indicates the presence of exchange coupling between two different hard and soft phases. - Highlights: • CoFe_2O_4–CoFe_2 was successfully synthesized by reduction diffusion process. • Two phases are effectively exchange coupled in nanocomposite. • Single smooth hysteresis loop was developed in nanocomposites.

Effects of TiO{sub 2} and Co{sub 2}O{sub 3} combination additions on the elemental distribution and electromagnetic properties of Mn–Zn power ferrites

Energy Technology Data Exchange (ETDEWEB)

Yang, W.D.; Wang, Y.G., E-mail: yingang.wang@nuaa.edu.cn

2015-06-15

The effects of TiO{sub 2} and Co{sub 2}O{sub 3} combination additions on the elemental distribution and electromagnetic properties of Mn–Zn power ferrites are investigated. TiO{sub 2} addition can promote Co{sub 2}O{sub 3} transfer from grain boundaries to the bulk of the grains. The temperature at which the highest initial permeability μ{sub i} and the lowest power losses P{sub L} appear shifts to low temperature range with the increase of Co{sub 2}O{sub 3} content. Compared with the reference sample without TiO{sub 2} and Co{sub 2}O{sub 3} addition, the microstructure and electromagnetic properties of Mn–Zn power ferrites can be considerably improved with suitable amounts of TiO{sub 2} and Co{sub 2}O{sub 3} combination additions. At the peak temperature, the sample with the 0.1 wt% TiO{sub 2} and 0.08 wt% Co{sub 2}O{sub 3} additions has an increase of 15.8% in μ{sub i} to 3951, and a decrease of 22.9% in P{sub L} to 286 kW/m{sup 3}. The saturation magnetic induction B{sub s} and electrical resistivity ρ at 25 °C reach the highest values of 532 mT and 8.12 Ω m, respectively. - Highlights: • TiO{sub 2} addition can promote Co{sub 2}O{sub 3} transfer from grain boundaries to the bulk of grains. • The Co{sup 2+} ion addition has a compensation for the effect of Ti{sup 4+}on the Mn–Zn ferrites. • The combination of TiO{sub 2} and Co{sub 2}O{sub 3} additions insures stabilization of crystal lattice. • The lowest power loss P{sub L} as 286 kW/m{sup 3} is relatively lower than reported now.

Manufacturing of Mn-Zn ferrite transformer cores

International Nuclear Information System (INIS)

Waqas, H.; Qureshi, A.H.; Hussain, N.; Ahmed, N.

2012-01-01

The present work is related to the development of soft ferrite transformer cores, which are extensively used in electronic devices such as switch mode power supplies, electromagnetic devices, computers, amplifiers etc. Mn-Zn Ferrite (soft ferrite) powders were prepared by conventional mixed oxide and auto combustion routes. These powders were calcined and then pressed in toroid shapes. Sintering was done at different temperatures to develop desired magnetic phase. Impedance resistance of sintered toroid cores was measured at different frequencies. Results revealed that Mn-Zn Ferrite cores synthesized by auto combustion route worked more efficiently in a high frequency range i.e. > 2MHz than the cores developed by conventional mixed oxide method. It was noticed that compact size, light weight and high impedance resistance are the prime advantages of auto combustion process which supported the performance of core in MHz frequency range. Furthermore, these compact size cores were successfully tested in linear pulse amplifier circuit of Pakistan Atomic Research Reactor-I. The fabrication of soft ferrite (Mn-Zn Ferrite) cores by different processing routes is an encouraging step towards indigenization of ferrite technology. (Orig./A.B.)

Enhanced Coal Bed Methane Recovery and CO2 Sequestration in the Powder River Basin

Energy Technology Data Exchange (ETDEWEB)

Eric P. Robertson

2010-06-01

Unminable coal beds are potentially large storage reservoirs for the sequestration of anthropogenic CO2 and offer the benefit of enhanced methane production, which can offset some of the costs associated with CO2 sequestration. The objective of this report is to provide a final topical report on enhanced coal bed methane recovery and CO2 sequestration to the U.S. Department of Energy in fulfillment of a Big Sky Carbon Sequestration Partnership milestone. This report summarizes work done at Idaho National Laboratory in support of Phase II of the Big Sky Carbon Sequestration Partnership. Research that elucidates the interaction of CO2 and coal is discussed with work centering on the Powder River Basin of Wyoming and Montana. Sorption-induced strain, also referred to as coal swelling/shrinkage, was investigated. A new method of obtaining sorption-induced strain was developed that greatly decreases the time necessary for data collection and increases the reliability of the strain data. As coal permeability is a strong function of sorption-induced strain, common permeability models were used to fit measured permeability data, but were found inadequate. A new permeability model was developed that can be directly applied to coal permeability data obtained under laboratory stress conditions, which are different than field stress conditions. The coal permeability model can be used to obtain critical coal parameters that can be applied in field models. An economic feasibility study of CO2 sequestration in unminable coal seams in the Powder River Basin of Wyoming was done. Economic analyses of CO2 injection options are compared. Results show that injecting flue gas to recover methane from CBM fields is marginally economical; however, this method will not significantly contribute to the need to sequester large quantities of CO2. Separating CO2 from flue gas and injecting it into the unminable coal zones of the Powder River Basin seam is currently uneconomical, but can

Structure and magnetic properties of Co and Ni nano-ferrites prepared by a two step direct microemulsions synthesis

Czech Academy of Sciences Publication Activity Database

Pulišová, Petra; Kováč, J.; Voigt, A.; Raschman, P.

2013-01-01

Roč. 341, september (2013), s. 93-99 ISSN 0304-8853 Institutional support: RVO:61388980 Keywords : Precipitation in microemulsion s * Ferrite nano-powder * Magnetic properties * ZFC * FC measurements Subject RIV: CA - Inorganic Chemistry Impact factor: 2.002, year: 2013

Characterization of magnetic nano particles of CoFe{sub 2}O{sub 4} and CoZnFe{sub 2}O{sub 4} prepared by the chemical co-precipitation method; Caracterizacion de nanoparticulas magneticas de CoFe{sub 2}O{sub 4} y CoZnFe{sub 2}O{sub 4} preparadas por el metodo de coprecipitacion quimica

Energy Technology Data Exchange (ETDEWEB)

Lopez, J.; Zambrano, G.; Gomez, M. E. [Universidad del Valle, Departamento de Fisica, Laboratorio de Peliculas Delgadas, Ciudad Universitaria Melendez, 25360 Cali (Colombia); Prieto, P. [Universidad del Valle, Centro de Excelencia en Nuevos Materiales, Ciudad Universitaria Melendez, 25360 Cali (Colombia); Espinoza B, F. J., E-mail: javierlo21@gmail.com [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Queretaro, Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla, 76230 Queretaro (Mexico)

2012-07-01

Magnetic cobalt ferrite nanoparticles of CoFe{sub 2}O{sub 4} and CoZnFe{sub 2}O{sub 4} were prepared by co-precipitation technique from aqueous salt solutions of Co (II), ZnSO{sub 4} and Fe (III), in an alkaline medium. CoFe{sub 2}O{sub 4} powder samples were structurally characterized by X-ray diffraction, showing the presence of the most intense peat at 2{theta} = 413928{sup o} (Co K{alpha}1) corresponding to the (311) crystallographic orientation of the CoFe{sub 2}O{sub 4} spinel phase. The mean size of the crystalline of CoFe{sub 2}O{sub 4} and CoZnFe{sub 2}O{sub 4} nanoparticles determined from the full width at half maximum of the strongest reflection of the (311) peak by using the Scherrer approximation was calculated to be 11.4 and 7.0 ({+-} o.2) nm, respectively. Transmission electron microscopy studies permitted determining nanoparticle size of CoZnFe{sub 2}O{sub 4}. Fourier transform infrared spectroscopy was used to confirm the formation of Fe-O bonds, allowing identifying the presence of ferrite spinel structure. Magnetic properties were investigated with the aid of a vibrating sample magnetometer at room temperature Herein, the sample showed superparamagnetic behavior, determined by the hysteresis loop finally, due to the hysteresis loop of the CoZnFe{sub 2}O{sub 4} is very small, our magnetic nanoparticles can be considered as a soft magnetic material. These magnetic nanoparticles have interesting technological applications in biomedicine given their biocompatibility, in nano technology, and in ferro fluid preparation. (Author)

Structural properties of Cd–Co ferrites

Indian Academy of Sciences (India)

36, No. 5, October 2013, pp. 919–922. c Indian Academy of Sciences. Structural properties of Cd–Co ferrites. S P DALAWAIa,∗. , T J SHINDEb, A B GADKARIc and P N VASAMBEKARa. aDepartment of Electronics, Shivaji University, Kolhapur 416 004, India. bDepartment of Physics, KRP Kanya Mahavidyalaya, Islampur ...

Preparation of TiO2 Nanocrystallite Powders Coated with 9 mol% ZnO for Cosmetic Applications in Sunscreens

Directory of Open Access Journals (Sweden)

Moo-Chin Wang

2012-02-01

Full Text Available The preparation of TiO2 nanocrystallite powders coated with and without 9 mol% ZnO has been studied for cosmetic applications in sunscreens by a co-precipitation process using TiCl4 and Zn(NO32·6H2O as starting materials. XRD results show that the phases of anatase TiO2 and rutile TiO2 coexist for precursor powders without added ZnO (T-0Z and calcined at 523 to 973 K for 2 h. When the T-0Z precursor powders are calcined at 1273 K for 2 h, only the rutile TiO2 appears. In addition, when the TiO2 precursor powders contain 9 mol% ZnO (T-9Z are calcined at 873 to 973 K for 2 h, the crystallized samples are composed of the major phase of rutile TiO2 and the minor phases of anatase TiO2 and Zn2Ti3O8. The analyses of UV/VIS/NIR spectra reveal that the absorption of the T-9Z precursor powders after being calcined has a red-shift effect in the UV range with increasing calcination temperature. Therefore, the TiO2 nanocrystallite powders coated with 9 mol% ZnO can be used as the attenuate agent in the UV-A region for cosmetic applications in sunscreens.

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

Science.gov (United States)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

Effects of In{sub 3+} substitution on structural properties, cation distribution and Mössbauer spectra of CoFe{sub 2}O{sub 4} ferrite

Energy Technology Data Exchange (ETDEWEB)

Kumar, Ravi, E-mail: ranade65@gmail.com [Centre for Material Science and Engineering, National Institute of Technology Hamirpur (H.P.)-177005 (India); Pandit, Rabia; Sharma, K. K.; Kaur, Pawanpreet [Department of Physics, National Institute of Technology Hamirpur (H.P.)-177005 (India)

2014-04-24

The use of non-destructive, high resolution technique namely Mössbauer spectroscopy is discussed in detail for the investigation of structural and magnetic properties of Fe based indium substituted cobalt ferrites. The polycrystalline samples of CoFe{sub 2−x}In{sub x}O{sub 4} (x = 0.2, 0.6) were prepared by double sintering solid state reaction method. To ensure a single phase formation of the as prepared samples the X-ray diffraction (XRD) data of the powdered samples was Rietveld refined using Fd3m space group. An excellent agreement is obtained between the integrated intensity ratios of 57 Fe spectra at A- and B-sites and those calculated on the basis of cation distribution the cation distribution obtained data analysis. The results of Mössbauer spectra and cation distribution are also correlated well with magnetization versus applied field (M-H) study.

Crystallographic and magnetic properties of the spinel-type ferrites Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 0.75)

Energy Technology Data Exchange (ETDEWEB)

Azad, A. K. [Faculty of Integrated Technologies, Universiti Brunei Darussalam, Gadong BE 1410 (Brunei Darussalam); Zakaria, A. K. M.; Yunus, S. M.; Kamal, I.; Datta, T. K. [Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, Savar, Dhaka (Bangladesh); Jewel, Md. Yusuf; Khan, Abu Saeed [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Eriksson, S.-G. [Department of Chemical & Biological Engineering, Chalmers University of Technology, Gothenburg (Sweden)

2015-05-15

Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn{sup 2+}, Co{sup 2+} and Fe{sup 3+} over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

Science.gov (United States)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Impact of Nd{sup 3+} in CoFe{sub 2}O{sub 4} spinel ferrite nanoparticles on cation distribution, structural and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Yadav, Raghvendra Singh, E-mail: yadav@fch.vutbr.cz [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Wasserbauer, Jaromir; Hajdúchová, Miroslava; Enev, Vojtěch [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Kuřitka, Ivo; Kožáková, Zuzana [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlín, Nad Ovčírnou 3685, 760 01 Zlín (Czech Republic)

2016-02-01

Nd{sup 3+} doped cobalt ferrite nanoparticles have been synthesized by starch-assisted sol–gel auto-combustion method. The significant role played by Nd{sup 3+} added to cobalt ferrite in changing cation distribution and further in influencing structural and magnetic properties, was explored and reported. The crystal structure formation and crystallite size were studied from X-ray diffraction studies. The microstructural features were investigated by field emission scanning electron microscopy and transmission electron microscopy that demonstrates the nanocrystalline grain formation with spherical morphology. An infrared spectroscopy study shows the presence of two absorption bands related to tetrahedral and octahedral group complexes within the spinel ferrite lattice system. The change in Raman modes in synthesized ferrite system were observed with Nd{sup 3+} substitution, particle size and cation redistribution. The impact of Nd{sup 3+} on cation distribution of Co{sup 2+} and Fe{sup 3+} at octahedral and tetrahedral sites in spinel ferrite cobalt ferrite nanoparticles was investigated by X-ray photoelectron spectroscopy. Room temperature magnetization measurements showed that the saturation magnetization and coercivity increase with addition of Nd{sup 3+} substitution in cobalt ferrite. - Highlights: • Nd{sup 3+} doped CoFe{sub 2}O{sub 4} nanoparticles by starch-assisted sol–gel auto-combustion method. • The change in Raman modes with Nd{sup 3+} substitution. • Presence of absorption infrared bands related to octahedral and tetrahedral site. • The impact of Nd{sup 3+} on cation distribution at octahedral and tetrahedral sites. • Influence of Nd{sup 3+} substitution in cobalt ferrite on magnetic properties.

Structural, magnetic and spectral properties of Gd and Dy co-doped dielectrically modified Co-Ni (Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4}) ferrites

Energy Technology Data Exchange (ETDEWEB)

Ditta, Allah [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Junaid, Muhammad, E-mail: junaid.malik95@yahoo.com [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khalil, R.M. Arif [Department of Physics, Sahiwal Sub-Campus Bahauddin Zakariya University, Sahiwal (Pakistan); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

2017-02-15

Gadolinium (Gd) and Dysprosium (Dy) co-doped Ni-Co (Ni{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4}) ferrites were prepared by micro-emulsion route. X-ray diffraction (XRD) analysis indicated the development of cubic spinel structure. The lattice parameter and X-ray density were found to increase from 8.24 to 8.31 Å and 5.57 to 5.91 (gm/cm{sup 3}) respectively as the Gd-Dy contents increased in nickel-cobalt ferrites. The crystallite size calculated from the Scherrer's formula exhibited the formation of nanocrystalline ferrites (13–26 nm). Two foremost absorption bands observed in FTIR spectra within 400 cm{sup −1} (υ{sub 2}) to 600 cm{sup −1} (υ{sub 1}) which correspond to stretching vibrations of tetrahedral and octahedral complexes respectively. The dielectric constant (ε) and dielectric loss (tanδ) were decreased by the optimization of frequency and abrupt decrease in the low frequency region and higher values in the high frequency region were observed. The dielectric dispersion was due to rapid decrease of dielectric constant in the low frequency region. This variation of dielectric dispersion was explicated in the light of space charge polarization model of Maxwell-Wagner. The dielectric loss occurs in these ferrites due to electron hopping and defects in the dipoles. The electron hopping was possible at low frequency range but at higher frequency the dielectric loss was decreased with the decrease of electron hopping. Magnetic properties were observed by measuring M-H loops. Due to low dielectric loss and dielectric constant these materials were appropriate in the fabrication of switching and memory storage devices.

Synthesis, structural investigation and magnetic properties of Zn{sup 2+} substituted cobalt ferrite nanoparticles prepared by the sol–gel auto-combustion technique

Energy Technology Data Exchange (ETDEWEB)

Raut, A.V., E-mail: nano9993@gmail.com [Vivekanand Arts and Sardar Dalipsingh Commerce and Science College, Aurangabad, 431004 Maharastra (India); Barkule, R.S.; Shengule, D.R. [Vivekanand Arts and Sardar Dalipsingh Commerce and Science College, Aurangabad, 431004 Maharastra (India); Jadhav, K.M., E-mail: drjadhavkm@gmail.com [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431004 Maharastra (India)

2014-05-01

Structural morphology and magnetic properties of the Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (0.0≤x≥1.0) spinel ferrite system synthesized by the sol–gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co–Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol–gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co–Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn{sup 2+} content in cobalt ferrite nanoparticles is followed by decrease in n{sub B}, M{sub s} and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature. - Highlights: • Co–Zn nanoparticles are prepared by sol–gel auto-combustion method. • Structural properties were characterized by XRD, SEM, and FTIR. • Compositional stoichiometry was confirmed by EDAX analysis. • Magnetic parameters were measured by the pulse field hysteresis loop technique.

Preparation and characterization of complex ferrite nanoparticles by a polymer-pyrolysis route

International Nuclear Information System (INIS)

Liu Xianming; Fu Shaoyun; Xiao Hongmei; Zhu Luping

2007-01-01

The polymer-pyrolysis route used in this work was to synthesize the copolymeric precursor of the mixed metallic ions and then to pyrolyze the precursor into complex spinel ferrite nanoparticles. Thermogravimetric analysis (TGA) showed that the complex ferrite nanoparticles could be obtained by calcination of their precursors at 500 deg. C. The structures, elemental analyses and particle morphology of the as-calcined products were characterized by powder X-ray diffraction (XRD), ICP-AES, transmission electron microscope (TEM) and electron diffraction (ED) pattern. The results revealed that the as-calcined powders were complex spinel ferrites and the size of those nanoparticles ranged from 10 to 20 nm. Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM). The saturation magnetization of the Mn-Zn ferrites was related to the molar ratio of Mn to Zn and increased with the increase of Mn. The complex Co-Mn-Zn ferrite nanoparticles showed a high magnetization of 58 emu/g at the applied field of 10 kOe and a low coercivity of 30 Oe, which indicated that this materials exhibited characteristics of soft ferromagnetism

Preparation and studies of Co(II) and Co(III)-substituted barium ferrite prepared by sol-gel method

Energy Technology Data Exchange (ETDEWEB)

Teh, Geok Bee [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia)]. E-mail: tehgb@mail.utar.edu.my; Nagalingam, Saravanan [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia); Jefferson, David A. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

2007-01-15

The sol-gel preparative method was employed to synthesise Co(II) and Co(III)-substituted barium ferrite. This method was attempted to achieve higher homogeneity of the final product. Samples of substituted ferrites were characterised by various experimental techniques including high resolution transmission electron microscopy, X-ray diffraction analysis, magnetometry and thermal gravimetric analysis. The microstructural changes induced by such substitution are also discussed.

Preparation and studies of Co(II) and Co(III)-substituted barium ferrite prepared by sol-gel method

International Nuclear Information System (INIS)

Teh, Geok Bee; Nagalingam, Saravanan; Jefferson, David A.

2007-01-01

The sol-gel preparative method was employed to synthesise Co(II) and Co(III)-substituted barium ferrite. This method was attempted to achieve higher homogeneity of the final product. Samples of substituted ferrites were characterised by various experimental techniques including high resolution transmission electron microscopy, X-ray diffraction analysis, magnetometry and thermal gravimetric analysis. The microstructural changes induced by such substitution are also discussed

Remanence properties of Co-precipitated cobalt ferrite

International Nuclear Information System (INIS)

Bueno-Baques, D.; Medina-Boudri, Angela; Matutes-Aquino, J.

2001-01-01

Isothermal remanent magnetization (IRM) and DC demagnetization (DCD) curves of a co-precipitated cobalt ferrite sample were obtained. From the IRM and DCD data, the Henkel plot was obtained and analyzed in the Preisach model framework. The Henkel plot data are below the Wohlfarth line that indicates a dominant local disorder (demagnetizing-like effect). Forward and reverse switching field distribution curves were obtained from differentiation of the IRM and DCD curves. The peak values of these switching field distributions differ by a factor of about 2.7

Heat generation ability in AC magnetic field of nano MgFe2O4-based ferrite powder prepared by bead milling

International Nuclear Information System (INIS)

Hirazawa, Hideyuki; Aono, Hiromichi; Naohara, Takashi; Maehara, Tsunehiro; Sato, Mitsunori; Watanabe, Yuji

2011-01-01

Nanosized MgFe 2 O 4 -based ferrite powder having heat generation ability in an AC magnetic field was prepared by bead milling and studied for thermal coagulation therapy applications. The crystal size and the particle size significantly decreased by bead milling. The heat generation ability in an AC magnetic field improved with the milling time, i.e. a decrease in crystal size. However, the heat generation ability decreased for excessively milled samples with crystal sizes of less than 5.5 nm. The highest heat ability (ΔT=34 o C) in the AC magnetic field (370 kHz, 1.77 kA/m) was obtained for fine MgFe 2 O 4 powder having a ca. 6 nm crystal size (the samples were milled for 6-8 h using 0.1 mm φ beads). The heat generation of the samples was closely related to hysteresis loss, a B-H magnetic property. The reason for the high heat generation properties of the samples milled for 6-8 h using 0.1 mm φ beads was ascribed to the increase in hysteresis loss by the formation of a single domain. Moreover, the improvement in heating ability was obtained by calcination of the bead-milled sample at low temperature. In this case, the maximum heat generation (ΔT=41 o C) ability was obtained for a ca. 11 nm crystal size sample was prepared by crystal growth during the sample calcination. On the other hand, the ΔT value for Mg 0.5 Ca 0.5 Fe 2 O 4 was synthesized using a reverse precipitation method decreased by bead milling. - Research Highlights: →The crystal and particle size for MgFe 2 O 4 based ferrite were decreased by bead milling. →The highest heat ability was obtained for MgFe 2 O 4 having a ca. 6 nm crystal size. →This high heat generation ability was ascribed to the increase in hysteresis loss. →Hysteresis loss was increased by the formation of a single domain.

PREPARATION OF WC-Co POWDER BY DIRECT REDUCTION AND CARBONIZATION

Institute of Scientific and Technical Information of China (English)

Zhonglai Yi; Gangqin Shao; Xinglong Duan; Peng Sun; Xiaoliang Shi; Zhen Xiong; Jingkun Guo

2005-01-01

A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed.Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder (CoWO4/WO3)was first formed by a spray-pyrolysis technique, which was then mixed with carbon black and converted to WC-Co composite powder at 950℃ for 4 h in N2 atmosphere. The resulting powder has a particle size of 100-300 nm.

Nanoferrites of nickel doped with cobalt: Influence of Co{sup 2+} on the structural and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, A.P.G. [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Gomes, D.K.S., E-mail: dkarinne@yahoo.com.br [Federal University of Rio Grande do Norte, Graduate Program in Materials Science and Engineering, Laboratory of Catalysis and Materials, Natal-RN 59078-970 (Brazil); Coordination of Improvement of Higher Education Personnel, CAPES/PNPD (Brazil); Araújo, J.H., E-mail: humberto@dfte.ufrn.br [Federal University of Rio Grande do Norte, Department of Theoretical and Experimental Physics, Laboratory of Magnetism and Magnetic Materials, Natal-RN 59078-970 (Brazil); Melo, D.M.A., E-mail: daraujomelo@gmail.com [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Oliveira, N.A.S. [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Braga, R.M., E-mail: renata@cear.ufpb.br [Federal University of Paraíba, DEER-CEAR, João Pessoa–PB 58051-970 (Brazil)

2015-01-15

Nanoferrites of nickel substituted with cobalt of composition Ni{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4} (0≤x≤0.75), were synthesized by combustion reaction assisted in microwaves. The influence of the substitution of Ni{sup 2+} by Co{sup 2+} content and the concentration of Co{sup 2+} in the structural and magnetic properties was investigated. The powders were prepared by combustion according to the concept of chemical propellants and heated in a microwave oven with a power of 7000 kW. The synthesized powders were characterized by absorption spectroscopy in the infrared region (FTIR), X-ray diffraction (XRD) together with Rietveld refinement, surface area (BET) method, scanning electron microscopy (MEV) and magnetic measurements (MAV). The results indicated that it was possible to obtain nickel ferrite doped with cobalt in all compositions and that an increase of cobalt concentration caused an increase in particle size (9.78–21.63 nm), a reduction in surface area, and reduction in magnetic concentrations greater than 50%. - Highlights: • Nanoferrites Ni{sub 1–x}Co{sub x}Fe{sub 2}O{sub 4}(0≤x≤0.75) synthesized by combustion reaction assisted. • The structural and magnetic properties of substitution of Ni{sup 2+} by Co{sup 2+} were investigate. • Combustion reaction takes spinel phase with suitable magnetic properties. • The ferrites presented characteristics of soft and intermediate magnetic materials.

Magnetic and electrical properties of the La doped Mn-Zn ferrite nanoparticles synthesized by the co-precipitation method

International Nuclear Information System (INIS)

Chandel, Vipin; Vijeta; Thakur, Atul; Thakur, Preeti

2013-01-01

In the present study, nano crystalline Mn-Zn-La ferrite with chemical formula Mn 0.4 Zn 0.6 La 0.3 Fe 1.7 O 4 was successfully synthesized by a co-precipitation method. The prepared powders were presintered at 700℃. The pallets formed were finally sintered at 700℃, 800℃ and 900℃ for 3h reach. The structural and morphological behavior was investigated by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD confirms the formation of the expected spinel structure. Scanning Electron Microscopy (SEM) was used to characterize the microstructure of the ferrite samples i.e. grain morphology, grain size, grain size distribution and shape. Fourier transform infrared spectroscopy (FTIR) confirms the peaks of different molecules in the given sample. Electrical and magnetic properties were studied by using dc resistivity set up and vibrating sample magnetometer (VSM). (author)

Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

International Nuclear Information System (INIS)

Majeed, Abdul; Khan, Muhammad Azhar; Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F.; Murtaza, Ghulam; Akhtar, Majid Niaz; Shakir, Imran; Warsi, Muhammad Farooq

2016-01-01

Rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm −1. Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b VI ). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba 2 NiCoRE x Fe 28−x O 46 ferrites. • The crystallite size was found in the range 7–19 nm. • The rare-earth incorporation enhanced the coercivity (664–926 Oe). �

Influence of metallic additives on manganese ferrites sintering

Science.gov (United States)

Shevelev, S. A.; Luchnikov, P. A.; Yarullina, A. R.

2018-01-01

Influence of cuprum nanopowder additive received by electric explosion on the process of manganese ferrites MgFe2O4 consolidating at thermal sintering was researched by dilatometry method. Cuprum nanopowder at a rate of 5 mass % was added into the original commercial-grade powder of manganese ferrite MgFe2O4. Powder mixture was numerously blended with screening for better blending before pressing. Powder compacts were formed by cold one-axle static pressing. It was proved that introduction of cuprum additive caused shrinkage increase at final heating stage. There was abnormal compact enlarging at sintering in the air at isothermal stage; the specified process was not observed in vacuum. This difference can be explained by changes in conditions of gaseous discharge from volume of pores.

Experimental determination of magnetocrystalline anisotropy constants and saturation magnetostriction constants of NiZn and NiZnCo ferrites intended to be used for antennas miniaturization

International Nuclear Information System (INIS)

Mattei, Jean-Luc; Le Guen, Emmanuel; Chevalier, Alexis; Tarot, Anne-Claude

2015-01-01

This study investigates the magnetocrystalline anisotropy constants (K 1 ) and the saturation magnetostriction constants (λ S ) of Ni 1−x Zn x Fe 2 O 4 (NiZn) and Ni 0.8−x Zn x Co 0.2 Fe 1.98 O 4−δ (NiZnCo) ferrites intended to be used for antenna downsizing. Composite materials constituted of soft ferrite nanosized particles (NiZn or NiZnCo ferrites) embedded in an epoxy matrix are realized. Measurements of their magnetic permeability in the frequency range of 200 MHz–6 GHz are performed. The influence of compressive stress (in the range of 32–96 MPa) on their Ferrimagnetic Resonance (FMR) is demonstrated. An analytical modeling of stress-induced FMR changes is proposed that allows simultaneous determinations of the Natural Ferrimagnetic Resonance (NFMR, F 0 ), K 1 and λ S of Ni 1−x Zn x Fe 2 O 4 and Ni 0.8−x Zn x Co 0.2 Fe 1.98 O 4−δ ferrites. The obtained results for NiZn ferrites are in agreement with literature data, validating both the experimental process and the proposed modeling of the stress-induced FMR changes. Regarding NiZnCo ferrites, extended data on K 1 and λ S are presented for the first time. Increasing zinc content (x) induces a spin disorder that reduces in a same time K 1 and the magnetization at saturation M S . The rapid variation of K 1 (x) is related to that of the magnetization M S (x) through a power law. The single-ion anisotropy model allows a satisfactory interpretation of K 1 dependence on zinc content. The unexpected low values of λ S got for NiZnCo ferrites, compared to those got for NiZn ferrites, are also discussed. Application of compressive stress lowers noticeably magnetic losses of Ni 0.6 Zn 0.2 Co 0.2 Fe 1.98 O 4−δ at given frequency, thereby enhancing the ability of this spinel ferrite to be used as a substrate in the aim of antenna miniaturization. - Highlights: • We measure permeability of ferrite-based composites from 0.1 GHz to 6 GHz. • The influence of compressive stress on the FMR of

Enhanced microwave absorption properties in cobalt–zinc ferrite based nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Poorbafrani, A., E-mail: a.poorbafrani@gmail.com; Kiani, E.

2016-10-15

In an attempt to find a solution to the problem of the traditional spinel ferrite used as the microwave absorber, the Co{sub 0.6}Zn{sub 0.4}Fe{sub 2}O{sub 4}–Paraffin nanocomposites were investigated. Cobalt–zinc ferrite powders, synthesized through PVA sol–gel method, were combined with differing concentrations of Paraffin wax. The nanocomposite samples were characterized employing various experimental techniques including X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Alternating Gradient Force Magnetometer (AGFM), and Vector Network Analyzer (VNA). The saturation magnetization and coercivity were enhanced utilizing appropriate stoichiometry, coordinate agent, and sintering temperature required for the preparation of cobalt–zinc ferrite. The complex permittivity and permeability spectra, and Reflection Loss (RL) of Co{sub 0.6}Zn{sub 0.4}Fe{sub 2}O{sub 4}–Paraffin nanocomposites were measured in the frequency range of 1–18 GHz. The microwave absorption properties of nanocomposites indicated that the absorbing composite containing 20 wt% of paraffin manifests the strongest microwave attenuation ability. The composite exhibited the reflection loss less than –10 dB in the whole C-band and 30% of the X-band frequencies. - Highlights: • We enhanced the magnetic properties of cobalt–zinc Ferrite nanocomposites. • The samples showed absorption in the whole C-band and 30% of the X-band frequencies. • We tried to solve the problem of the spinel ferrite utilized as efficient absorber. • We enhanced the microwave reflection loss over extended frequency ranges.

Structural and optical properties of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano ferrites: Effect of sintering temperature

Energy Technology Data Exchange (ETDEWEB)

Thakur, Prashant, E-mail: prashant007thakur@gmail.com; Sharma, Rohit; Sharma, Vineet, E-mail: vineet.sharma@juiit.ac.in; Sharma, Pankaj, E-mail: pankaj.sharma@juit.ac.in

2017-06-01

Mn-Zn ferrites have shown various remarkable applications e.g. in magnetic amplifiers, power transformers and electromagnetic interference etc. due to their high initial permeability. Mn–Zn ferrite powder (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) has been prepared by the co-precipitation method and subsequently sintered at three different temperatures i.e. 973 K, 1173 K, 1373 K. Optical properties have been correlated with the structural properties. For structural properties X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) have been employed. It has been observed that there is an increase in crystallite size with sintering from 973 K to 1373 K and FTIR confirms the formation of bond between metal ion and oxygen ion at the octahedral site and tetrahedral site. A red shift has been confirmed from UV–visible absorption spectra and photoluminescence spectra have been reported with an increase in sintering temperature. - Graphical abstract: Mn–Zn ferrite powder (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) has been prepared by the co-precipitation method and subsequently sintered at three different temperatures i.e. 973 K, 1173 K, 1373 K. A red shift has been confirmed from UV–visible absorption spectra and photoluminescence spectra have been reported with an increase in sintering temperature. - Highlights: • Nanoparticles of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} have been prepared by the co-precipitation method. • There is an increase in crystallite size with sintering from 973 K to 1373 K. • A red shift is found in UV–visible and PL spectra with an increase in sintering temperature.

Synthesis of zinc substituted cobalt ferrites via reverse micelle technique involving in situ template formation: A study on their structural, magnetic, optical and catalytic properties

Energy Technology Data Exchange (ETDEWEB)

Singh, Charanjit; Jauhar, Sheenu [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Kumar, Vinod [ICON Analytical Equipment (P) Ltd., Mumbai 400018 (India); Singh, Jagdish [Institute Instrumentation Centre, Indian Institute of Technology–Roorkee (India); Singhal, Sonal, E-mail: sonal1174@gmail.com [Department of Chemistry, Panjab University, Chandigarh 160014 (India)

2015-04-15

Nano-crystalline particles of visible light responsive Zn–Co ferrites having formula Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were successfully synthesized via reverse micelle technique. Sodium dodecyl sulfate was used as a surfactant/templating agent. The ferrite formation was confirmed using powder X-Ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. The spherical shape of the ferrite particles was established by High Resolution Transmission Electron Microscope (HR-TEM) analysis. From the magnetic studies, the ferromagnetic nature of CoFe{sub 2}O{sub 4} was known. However, the nano-particles exhibited a transition from ferromagnetic to super-paramagnetic upon increasing the zinc concentration. In addition, the photo-Fenton activity of ferrites was also studied by carrying out degradation of Rhodamine B (RhB) dye under visible light irradiation. The catalytic activity increased with increase in zinc ion concentration. - Highlights: • Controlled dimensions of Zn–Co ferrite nanoparticles by microemulsion technique. • Spherical shape with uniform size distribution of ∼5 nm was achieved. • Significant shift from ferromagnetic to superparamagnetic with Zn{sup 2+} ion doping. • Improved photocatalytic activity with Zn{sup 2+} ion doping.

Effect of Zn addition on structural, magnetic properties, antistructural modeling of Co1-xZnxFe2O4 nano ferrite

Science.gov (United States)

Raghuvanshi, S.; Kane, S. N.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

Effect of Zn addition on cationic distribution, structural properties, magnetic properties, antistructural modeling of nanocrystalline Co1-xZnxFe2O4 (0.08 ≤ x ≤ 0.56) ferrite is reported. XRD confirms the formation of single phase cubic spinel nano ferrites with average grain diameter ranging between 41.2 - 54.9 nm. Coercivity (Hc), anisotropy constant (K1) decreases with Zn addition, but experimental, theoretical saturation magnetization (Ms, Ms(t)) increases upto x = 0.32, then decreases, attributed to the breaking of collinear ferrimagnetic phase. Variation of magnetic properties is correlated with cationic distribution. A new antistructural modeling for describing active surface centers is discussed to explain change in concentration of donor's active centers Zn'B, Co'B, acceptor's active centers Fe*A are explained.

Effect of d-block element Co{sup 2+} substitution on structural, Mössbauer and dielectric properties of spinel copper ferrites

Energy Technology Data Exchange (ETDEWEB)

Dar, M.A.; Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com

2017-08-15

Highlights: • Tetragonal (I41/amd) to cubic (Fd3m) phase change is observed in Cu{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4}. • Raman studies reveal 2 (5) optical active modes in CuFe{sub 2}O{sub 4} and 5 (5) at room temperature. • Transmission Mössbauer spectroscopy discerns two sets of six-line hyperfine patterns. • The dielectric constant increases is maximum for Co{sup 2+}x = 0.1 composition. • ac conductivity is constant (low frequency) and increases abruptly (high frequency). - Abstract: The present work focuses on the influence of replacement of d-block element Cu{sup 2+} ion by Co{sup 2+} in Cu-spinel ferrites [Cu{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.1, 0.2, 0.4, 0.6, and 1.0)] on the structural, vibrational and dielectric properties as synthesized by Solid-state reaction route. A structural transition from tetragonal (space group I41/amd)) to cubic (space group Fd3m) phase is observed due to introduction of cobalt. Cubic spinel- type structure at room temperature of Cu{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4} (0.4 ≤ x ≤ 1.0) is confirmed by Rietveld – refined X-ray powder diffraction patterns. Raman spectroscopic studies reveal 2 (5) optical active modes in CuFe{sub 2}O{sub 4} (CoFe{sub 2}O{sub 4}) at room temperature. Transmission Mössbauer spectroscopy of Cu{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.2 and 0.6) shows two sets of six-line hyperfine patterns for all the three samples, indicating the presence of Fe in both A and B sites. Identification of sites is accomplished by evidence from hyperfine distribution and isomer-shift data. Dielectric constant and dielectric loss tangent measured in the frequency range from 1 KHz to 1 MHz at room temperature are found to be decreasing with the increase in frequency.

Synthesis and characterization of nanocrystalline zinc ferrite

DEFF Research Database (Denmark)

Jiang, J.S.; Yang, X.L.; Gao, L.

1999-01-01

Nanocrystalline zinc ferrite powders with a partially inverted spinel structure were synthesized by high-energy ball milling in a closed container at ambient temperature from a mixture of alpha-Fe2O3 and ZnO crystalline powders in equimolar ratio. From low-temperature and in-field Mossbauer...

Application of permanent magnets made from NdFeB powder and from mixtures of powders in DC motors

International Nuclear Information System (INIS)

Slusarek, B.; Dudzikowski, I.

2002-01-01

The paper presents the influence of magnetic properties of applied permanent magnets on the characteristics of DC motors excited with these magnets. In the factory-produced DC motors, excited with sintered ferrite magnets, authors replaced ferrite magnets with the dielectromagnets from NdFeB powder and from different mixtures of NdFeB and ferrite powders. The paper shows the increase of the power of the resultant DC motors according to the powders' content

Experimental determination of magnetocrystalline anisotropy constants and saturation magnetostriction constants of NiZn and NiZnCo ferrites intended to be used for antennas miniaturization

Energy Technology Data Exchange (ETDEWEB)

Mattei, Jean-Luc, E-mail: mattei@univ-brest.fr [Lab-STICC, Université de Bretagne Occidentale, CS 93837, 6 Avenue Le Gorgeu, 29238 Brest Cedex 3 (France); Le Guen, Emmanuel, E-mail: emmanuel.leguen@hotmail.fr [Lab-STICC, Université de Bretagne Occidentale, CS 93837, 6 Avenue Le Gorgeu, 29238 Brest Cedex 3 (France); IETR, Université de Rennes 1, 263 Avenue General Leclerc, 35042 Rennes Cedex (France); Chevalier, Alexis, E-mail: alexis.chevalier@univ-brest.fr [Lab-STICC, Université de Bretagne Occidentale, CS 93837, 6 Avenue Le Gorgeu, 29238 Brest Cedex 3 (France); Tarot, Anne-Claude, E-mail: anne-claude.tarot@univ-rennes1.fr [IETR, Université de Rennes 1, 263 Avenue General Leclerc, 35042 Rennes Cedex (France)

2015-01-15

This study investigates the magnetocrystalline anisotropy constants (K{sub 1}) and the saturation magnetostriction constants (λ{sub S}) of Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (NiZn) and Ni{sub 0.8−x}Zn{sub x}Co{sub 0.2}Fe{sub 1.98}O{sub 4−δ} (NiZnCo) ferrites intended to be used for antenna downsizing. Composite materials constituted of soft ferrite nanosized particles (NiZn or NiZnCo ferrites) embedded in an epoxy matrix are realized. Measurements of their magnetic permeability in the frequency range of 200 MHz–6 GHz are performed. The influence of compressive stress (in the range of 32–96 MPa) on their Ferrimagnetic Resonance (FMR) is demonstrated. An analytical modeling of stress-induced FMR changes is proposed that allows simultaneous determinations of the Natural Ferrimagnetic Resonance (NFMR, F{sub 0}), K{sub 1} and λ{sub S} of Ni{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} and Ni{sub 0.8−x}Zn{sub x}Co{sub 0.2}Fe{sub 1.98}O{sub 4−δ} ferrites. The obtained results for NiZn ferrites are in agreement with literature data, validating both the experimental process and the proposed modeling of the stress-induced FMR changes. Regarding NiZnCo ferrites, extended data on K{sub 1} and λ{sub S} are presented for the first time. Increasing zinc content (x) induces a spin disorder that reduces in a same time K{sub 1} and the magnetization at saturation M{sub S}. The rapid variation of K{sub 1}(x) is related to that of the magnetization M{sub S}(x) through a power law. The single-ion anisotropy model allows a satisfactory interpretation of K{sub 1} dependence on zinc content. The unexpected low values of λ{sub S} got for NiZnCo ferrites, compared to those got for NiZn ferrites, are also discussed. Application of compressive stress lowers noticeably magnetic losses of Ni{sub 0.6}Zn{sub 0.2}Co{sub 0.2}Fe{sub 1.98}O{sub 4−δ} at given frequency, thereby enhancing the ability of this spinel ferrite to be used as a substrate in the aim of antenna

Magnetic behavior of nickel ferrite nanoparticles prepared by co-precipitation route

International Nuclear Information System (INIS)

Maaz, K.; Mashiatullah, A.; Javed, T.; Ali, G.; Karim, S.

2008-01-01

Magnetic nanoparticles of nickel ferrite (NiFe/sub 2/O/sub 4/) have been synthesized by co-precipitation route using stable ferric and nickel salts with sodium hydroxide as the precipitating agent and oleic acid as the surfactant. X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) analyses confirmed the formation of single phase nickel ferrite nanoparticles in the range 8-28 nm. The size of the particles was observed to be increasing linearly with increasing annealing temperature of the sample. Typical blocking effects were observed below -225 K for all the prepared samples. The superparamagnetic blocking temperature was found to be continuously increasing with increasing particle sizes that has been attributed to the increased effective anisotropy of the nanoparticles. The saturation moment of all the samples was found much below the bulk value of nickel ferrite that has been attributed to the disordered surface spins of these nanoparticles. (author)

Magnetic properties of Co-ferrite-doped hydroxyapatite nanoparticles having a core/shell structure

International Nuclear Information System (INIS)

Petchsang, N.; Pon-On, W.; Hodak, J.H.; Tang, I.M.

2009-01-01

The magnetic properties of Co-ferrite-doped hydroxyapatite (HAP) nanoparticles of composition Ca 10-3x Fe 2x Co x (PO 4 ) 6 (OH) 2 (where x=0, 0.1, 0.2, 0.3, 0.4 and 0.5% mole) are studied. Transmission electron microscope micrograms show that the 90 nm size nanoparticles annealed at 1250 o C have a core/shell structure. Their electron diffraction patterns show that the shell is composed of the hydroxyapatite and the core is composed of the Co-ferrite, CoFe 2 O 4 . Electron spin resonance measurements indicate that the Co 2+ ions are being substituted into the Ca(1) sites in HAP lattice. X-ray diffraction studies show the formation of impurity phases as higher amounts of the Fe 3+ /Co 2+ ions which are substituted into the HAP host matrix. The presence of two sextets (one for the A-site Fe 3+ and the other for the B-site Fe 3+ ) in the Moessbauer spectrum for all the doped samples clearly indicates that the CoFe 2 O 4 .cores are in the ferromagnetic state. Evidence of the impurity phases is seen in the appearance of doublet patterns in the Moessbauer spectrums for the heavier-doped (x=0.4 and 0.5) specimens. The decrease in the saturation magnetizations and other magnetic properties of the nanoparticles at the higher doping levels is consistent with some of the Fe 3+ and Co 2+ which being used to form the CoO and Fe 2 O 3 impurity phase seen in the XRD patterns.

Tunable permittivity and permeability of low loss Z + Y-type ferrite composites for ultra-high frequency applications

Energy Technology Data Exchange (ETDEWEB)

Su, Zhijuan; Hu, Bolin; Chen, Yajie, E-mail: y.chen@neu.edu; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); Li, Qifan; Feng, Zekun [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Wang, Xian [Center for Microwave Magnetic Materials and Integrated Circuits, and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States); School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

2015-05-07

A series of Z-type and Y-type ferrite composites with various phase fractions were studied for their RF properties including the measurement of permittivity to permeability spectra over a frequency range of 0.1–10 GHz. Phase identification of the ferrite composites' constituents was determined by X-ray diffraction. An effective medium approximation was used to predict the magnetic and dielectric behavior of the composites. The experiments indicated that the composite having 75 vol. % of Z-type ferrite demonstrated a permeability of ∼12 with a nearly equivalent permittivity, yielding a ratio (μ′/ε′) of 0.91 at a frequency range from 0.55 to 0.75 GHz. The dielectric loss (i.e., tan δ{sub ε}) and magnetic loss (i.e., tan δ{sub μ}) were measured to be lower than 0.08 at f = 0.1–1 GHz and 0.29 at f = 0.1–0.7 GHz, respectively. Furthermore, the loss factors, as tan δ{sub ε}/ε′ and tan δ{sub μ}/μ′, were calculated to be 0.003 and 0.02 at 0.65 GHz, respectively.

Development of novel exchange spring magnet by employing nanocomposites of CoFe{sub 2}O{sub 4} and CoFe{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Safi, Rohollah; Ghasemi, Ali, E-mail: ali13912001@yahoo.com; Shoja-Razavi, Reza; Tavoosi, Majid

2016-12-01

CoFe{sub 2}O{sub 4}−CoFe2 hard–soft nanocomposites were prepared via reduction of the cobalt ferrite CoFe{sub 2}O{sub 4} in hydrogen atmosphere at different temperature. The structure and the room temperature magnetization of the samples were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization of the nanocomposite powders increases by reduction temperature while their coercivity decreases. The highest M{sub r}/M{sub s} ratio of 0.52 was obtained for sample reduced at 550 °C. Single smooth hysteresis loops of nanocomposites show that these nanocomposites behave as the single-phase materials. This result indicates the presence of exchange coupling between two different hard and soft phases. - Highlights: • CoFe{sub 2}O{sub 4}–CoFe{sub 2} was successfully synthesized by reduction diffusion process. • Two phases are effectively exchange coupled in nanocomposite. • Single smooth hysteresis loop was developed in nanocomposites.

An investigation of semiconducting behavior in the minority spin of Co2CrZ (Z = Ga, Ge, As): LSDA and LSDA + U method

International Nuclear Information System (INIS)

Rai, D.P.; Thapa, R.K.

2012-01-01

Highlights: ► Volume optimization was done to find the theoretical lattice parameters. ► LSDA was performed to calculate electronic and magnetic properties of Co 2 CrZ. ► The result shows the half-metal ferromagnetic behavior of Co 2 CrGa and Co 2 CrGe. ► Co 2 CrAs fails to give HMF within LSDA thus treated with LSDA + U, to obtain HMF. - Abstract: We have calculated the electronic and magnetic properties of 3d transition metal based full Heusler compounds Co 2 CrZ (Z = Ga, Ge, As), by using full potential linearized augmented plane wave (FP-LAPW) method. The calculated density of states (DOS) and band structure for Co 2 CrZ shows the existence of band gap in their minority-spin channel. The respective energy gaps of Co 2 CrGe and Co 2 CrGa are 0.24 and 0.38 eV with their Fermi energies (E F s) lie exactly at the gap. The compound Co 2 CrAs when treated with local spin density approximation (LSDA) does not show half metallic ferromagnetism (HMF) even though there exist a gap this is because the E F does not lie at the middle of the gap. We have considered Co 2 CrAs as strongly correlated system as Cr-d states at E F are strongly localized thus the system was treated in terms of the LSDA + U. The total magnetic moment of Co 2 CrAs was found to be an exact integer value 5.00 μ B within LSDA + U. We have also found that the total magnetic moments increase as the Z goes from Ga to As.

Moessbauer and magnetic susceptibility measurements on M-type hexagonal Ba - ferrite

International Nuclear Information System (INIS)

Lipka, J.; Gruskova, A.; Sitek, J.; Miglierini, M.; Groene, R.; Hucl, M.; Toth, I.; Orlicky, O.

1990-01-01

Samples of stoichiometric BaFe 12 O 19 and Co, Ti substituted barium ferrite were prepared by chemical wet method. Moessbauer spectroscopy, magnetic susceptibility measurements, X-ray diffraction, infrared spectroscopy were conducted to examine the mechanism of formation. The observed magnetic characteristics and electron scanning microscopy show that single domain coprecipitated powders were formed. (orig.)

Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

Energy Technology Data Exchange (ETDEWEB)

Majeed, Abdul, E-mail: abdulmajeed2276@gmail.com [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F. [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Murtaza, Ghulam [Centre for Advanced Studies in Physics, Government College University, Lahore 54000 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Shakir, Imran [Deanship of Scientific Research, College of Engineering, King Saud University, PO Box 800, Riyadh 11421 (Saudi Arabia); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

2016-06-15

Rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm{sup −1.} Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b{sub VI}). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} ferrites. • The crystallite size was found

Effects of Gd-Substitutions on the Microstructure, Electrical and Electromagnetic Behavior of M-Type Hexagonal Ferrites

Science.gov (United States)

Ahmad, Ishtiaq; Ahmad, Mahmood; Ali, Ihsan; Kanwal, M.; Awan, M. S.; Mustafa, Ghulam; Ahmad, Mukhtar

2015-07-01

A series of Gd-substituted Ba-Co-based (M-type) hexaferrites having the chemical compositions of Ba0.5Co0.5Gd x Fe12- x O19 ( x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by co-precipitation method. The pellets formed by co-precipitated powder were calcined at a temperature of 1200°C for 20 h. Final sintering was done at 1320°C for 4 h. From the x-ray diffraction analysis, it was revealed that all the samples showed M-type hexagonal structure as a major phase. The scanning electron microscope was used to examine the morphology of the sintered ferrites. The average grain size estimated by the line intercept method was found to be in the range of 2.8-1.0 μm. The room temperature DC resistivity increases with increasing Gd-contents to make these ferrites useful for high frequency applications and microwave devices. Lower values of coercivity ( H c) and higher saturation magnetization ( M s) may be suitable to enhance the permeability of these ferrites, which is favorable for impedance matching in microwave absorption. In addition, reflection coefficients for a sample was also measured from a frequency of 1 MHz to 3 GHz and a reflection peak was observed at about 2.2 GHz.

Magnetic properties of Sn-substituted Ni-Zn ferrites synthesized from nano-sized powders of NiO, ZnO, Fe2O3, and SnO2

Science.gov (United States)

Ali, MA; Uddin, MM; Khan, MNI; Chowdhury, FUZ; Hoque, SM; Liba, SI

2017-06-01

A series of Ni0.6-x/2Zn0.4-x/2Sn x Fe2O4 (x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3) (NZSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction (XRD). The magnetic properties such as saturation magnetization ({M}{{s}}), remanent magnetization ({M}{{r}}), coercive field ({H}{{c}}), and Bohr magneton (μ) are calculated from the hysteresis loops. The value of {M}{{s}} is found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability ({μ }^{\\prime }) over a wide range of frequency. The decreasing trend of {μ }^{\\prime } with increasing Sn content has been observed. Curie temperature {T}{{C}} has been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the NZSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

Room temperature ferromagnetism in nano-crystalline Co:ThO2 powders

International Nuclear Information System (INIS)

Bhide, M.K.; Kadam, R.M.; Godbole, S.V.; Tyagi, A.K.; Salunke, H.G.

2012-01-01

The major interest in dilute magnetic semiconductors (DMS's) had been directed towards the synthesis of room temperature ferromagnetic (RTF) materials for their potential applications in spintronic devices. Room temperature (RT) ferromagnetism was initially reported in Co doped TiO 2 , ZnO 2 and SnO 2 thin films and in the recent past in transition metal doped wide band gap materials. In the present paper we report the synthesis of Co doped ThO 2 nano powders by urea combustion method. The XRD characterization of 300℃ annealed samples confirmed formation of ThO 2 in the cubic phase and the average crystallite size obtained using Scherrer's formula was around 6 nm

Magnetic properties of Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} spinel ferrite nanoparticles synthesized by starch-assisted sol–gel autocombustion method and its ball milling

Energy Technology Data Exchange (ETDEWEB)

Yadav, Raghvendra Singh, E-mail: yadav@fch.vutbr.cz [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Havlica, Jaromir [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Hnatko, Miroslav; Šajgalík, Pavol [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 36 Bratislava (Slovakia); Alexander, Cigáň [Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9, SK-841 04 Bratislava (Slovakia); Palou, Martin; Bartoníčková, Eva; Boháč, Martin; Frajkorová, Františka; Masilko, Jiri; Zmrzlý, Martin; Kalina, Lukas; Hajdúchová, Miroslava; Enev, Vojtěch [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic)

2015-03-15

In this article, Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (x=0.0 and 0.5) spinel ferrite nanoparticles were achieved at 800 °C by starch-assisted sol–gel autocombustion method. To further reduce the particle size, these synthesized ferrite nanoparticles were ball-milled for 2 h. X-ray diffraction patterns demonstrated single phase formation of Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (x=0.0 and 0.5) spinel ferrite nanoparticles. FE-SEM analysis indicated the nanosized spherical particles formation with spherical morphology. The change in Raman modes and relative intensity were observed due to ball milling and consequently decrease of particle size and cationic redistribution. An X-ray Photoelectron Spectroscopy (XPS) result indicated that Co{sup 2+}, Zn{sup 2+} and Fe{sup 3+} exist in octahedral and tetrahedral sites. The cationic redistribution of Zn{sup 2+} and consequently Fe{sup 3+} occurred between octahedral and tetrahedral sites after ball-milling. The change in saturation magnetization (M{sub s}) and coercivity (H{sub c}) with decrease of nanocrystalline size and distribution of cations in spinel ferrite were observed. - Highlights: • Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} spinel ferrite nanoparticles. • Starch-assisted sol–gel auto-combustion method. • Effect of ball-milling on particle size and cation distribution. • Magnetic property dependent on cations and particle size.

Study and characterization of the hexa ferrite Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}-Y); Sintese e caracterizacao da hexaferrita Ba{sub 2}Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}-Y)

Energy Technology Data Exchange (ETDEWEB)

Pires Junior, G.F.M.; Rodrigues, H.O. [Universidade Federal do Ceara (DETI/UFC), Fortaleza, CE (Brazil). Dept. de Teleinformatica; Sales, J.C [Universidade Estadual Vale do Acarau (UVA), Fortaleza, CE (Brazil). Dept. de Engenharia; Sancho, E.O. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Engenharia de Materiais; Sombra, A.S.B. [Universidade Federal do Ceara (LOCEM/UFC), Fortaleza, CE (Brazil). Dept. de Fisica. Lab. de Telecomunicacoes e Ciencias e Engenharia de Materiais

2009-07-01

The objective of this work is to synthesize and to characterize the Hexaferrita Ba2Co{sub 2}Fe{sub 12}O{sub 22} (Co{sub 2}Y). The Y-type Hexaferrita (Co{sub 2}Y) was prepared by the ceramic conventional method. The mixed powder by 1 h was calcined at 1050 deg C for 3 h. After of the calcination the powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) using a diffractometer DMAXB of the Rigaku (Japan), CuK{sub {alpha}} radiation ({lambda}=1.5405 angstrom) in a tax of 0.5 deg /min and linear band (20 deg at 80 deg) in 2{theta}. The characterization more detailed by XRD was made using the DBWS9807a program that uses the method of Rietveld for refinement of crystalline structures and confirmed the isolated attainment of the phase (Co{sub 2}Y) with hexagonal crystalline structure (a = b = 5,8560 angstrom and c = 43,4977 angstrom; {alpha} = {beta} = 90 deg and {gamma} = 120 deg) with density and volume of the unit cell calculated of 5.45 g/cm{sup 3} and 1292,3 angstrom respectively. (author)

Complex impedance techniques and some properties of Mn sub 0.5 Zn sub 0.5 Fe sub 2 O sub 4 ferrite

International Nuclear Information System (INIS)

Ahmad Nazlim Yusoff; Mustaffa Abdullah

1995-01-01

Complex impedances (Z-axes = Z' - jZ ) of a standard parallel R-C circuit and a Mn sub 0.5 Zn sub 0.5 Fe sub 2 O sub 4 ferrite sample at 300 K have been measured in the frequency range 1 Hz to 10 MHz by a technique of phase shift. For comparison, the impedances of both systems were also measured using Schlumberger HF 1255 frequency response analyzer. The complex impedance spectrum (Z' vs Z') from the R-C circuit is a perfect semicircle, whereas the spectrum for the ferrite sample is a semicircular curve with its centre being depressed to below the real impedance axis. The depression of the semicircle for the ferrite is discussed as due to a deviation from the ideal Debye relaxation process. An equivalent circuit model that comprises of a capacitor and a resistor in parallel is suggested for the ferrite, but the result for the impedance is modified by including a factor that accounts for the distribution of the relaxation time. The simulated data from the circuit are in agreement with those from the experiment. The dispersion of the impedance is attributed to the conduction and polarization processes in the material

Optimization of LiCoO2 powder extraction process from cathodes of lithium-ion batteries by chemical dissolution

Directory of Open Access Journals (Sweden)

Lucas Evangelista Sita

2015-05-01

Full Text Available A chemical process has been applied to extract LiCoO2 powder from cathodes of spent lithium-ion batteries by dissolution of the binder that agglutinate the powder particle each other as well to the Al collector surface. As solvents dimethylformamide (DMF and N-methyilpirrolidone (NMP were employed and the variables, cathode area, solution temperature, ultrasound bath power and solution stirring were chosen to optimize the extraction process. NMP solutions presented best results for powder extraction than DMF solutions. At 100 oC and under mechanical stirring or low power ultrasound bath NMP solution optimizes the binder dissolution. Powder extractions under DMF solutions are slow and an increase in the powder extraction efficiency was observed for crushed cathodes on solutions under ultrasound bath, at medium power. Filtration processes can separate the decanted LiCoO2 powder extracted upon DMF dissolution while the powder in suspension in the NMP solutions is separated by centrifugation techniques.

Structural and DC electrical resistivity, magnetic properties of Co0.5M0.5Fe2O4 (M= Ni, Zn, and Mg) ferrite nanoparticles

Science.gov (United States)

Ramakrishna, A.; Murali, N.; Mammo, Tulu Wegayehu; Samatha, K.; Veeraiah, V.

2018-04-01

Inverse spinel structured nanoparticles of cobalt ferrite partially substituted by divalent cations of Ni, Zn, and Mg have been synthesized through sol-gel auto combustion route. Structural parameters are studied by powder X-ray diffraction at the diffraction angle range of 10-80°; and FT-IR spectroscopy in the wavenumber range of 1600-400 cm-1. Lattice parameters were calculated from the (hkl) values of the diffraction planes and interplanar spacing and found to be in the range of 8.3659-8.4197 Å. The surface morphology and crystalline nature are studied using scanning electron microscopy and also using HRTEM. The magnetic properties are analyzed through vibrating sample magnetometer. High saturation magnetization of 90.12 emu/g has been achieved from Co-Zn sample whereas high coercive force of 883.45 Oe is achieved in Co-Ni sample. A two-probe DC resistivity was measured in temperature ranges of 300-450 K.

Structural and physical property study of sol-gel synthesized CoFe2-xHoxO4 nano ferrites

Science.gov (United States)

Patankar, K. K.; Ghone, D. M.; Mathe, V. L.; Kaushik, S. D.

2018-05-01

CoFe2-xHoxO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20) ferrites were prepared by the suitably modified Sol-Gel technique. X-ray diffraction (XRD) analysis revealed that the substituted samples show phase pure formation till 10% substitution, which is far higher phase pure than the earlier reports. Upon further substitution an inevitable secondary phase of HoFeO3 along with the spinel phase despite regulating synthesis parameters in the sol-gel reaction route. These results are further corroborated more convincingly by room temperature neutron diffraction. Morphological features of the ferrites were studied by Scanning Electron Microscopy (SEM). The magnetic parameters viz. the saturation magnetization (Ms), coercivity (Hc) and remanence (Mr) were determined from room temperature isothermal magnetization. These parameters were found to decrease with increase in Ho substitution. The decrease in magnetization is analyzed in the light of exchange interactions between rare earth and transition metal ions. Magnetostriction measurements revealed interesting results and the presence of a secondary phase was found to be responsible for decreased measu-red magnetostriction values. The solubility limit of Ho in CoFe2O4 lattice is also reflected from the X-ray and neutron diffraction analysis and magnetostriction studies.

Magnetic Properties of Copper Doped Nickel Ferrite Nanoparticles Synthesized by Co Precipitation Method

Science.gov (United States)

Anjana, V.; John, Sara; Prakash, Pooja; Nair, Amritha M.; Nair, Aravind R.; Sambhudevan, Sreedha; Shankar, Balakrishnan

2018-02-01

Nickel ferrite nanoparticles with copper atoms as dopant have been prepared using co-precipitation method with general formula Ni1-xCuxFe2O4 (x=0.2, 0.4, 0.6, 0.8 and 1) and are sintered at quite ambient temperature. Structural and magnetic properties were examined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction method (XRD) and Vibrating Sample Magnetometer (VSM) to study the influence of copper doping in nickel ferrite magnetic nanoparticles. X-ray studies proves that the particles are possessing single phase spinel structure with an average particle size calculated using Debye Scherer formula. Magnetic measurements reveal that saturation magnetization value (Ms) decreases while magnetic coercivity (Hc) increases upon doping.

Kinetics of CO Oxidation over Unloaded and Pd-Loaded α-Fe2O3 Spherical Submicron Powder Catalysts: Photoacoustic Investigations at Low Pressure

Directory of Open Access Journals (Sweden)

Joong-Seok Roh

2018-02-01

Full Text Available In this study, α-Fe2O3 spherical particles with an average diameter of approximately 200 nm were synthesized by a solvothermal method for use as both a catalyst and medium for a Pd catalyst. The kinetics of CO oxidation over powders of α-Fe2O3 spherical particles and 14 wt % Pd/α-Fe2O3 spherical particles were measured in a static reactor by using a CO2 laser-based photoacoustic technique. The total pressure was fixed at 40 Torr for the CO/O2/N2 mixture for temperatures in the range of 225–350 °C. The variation in the CO2 photoacoustic signal with the CO2 concentration during CO oxidation was recorded as a function of time, and the CO2 photoacoustic data at the early reaction stage was used to estimate the rates of CO2 formation. Based on plots of ln(rate vs. 1/T, apparent activation energies were calculated as 13.4 kcal/mol for the α-Fe2O3 submicron powder and 13.2 kcal/mol for the 14 wt % Pd/α-Fe2O3 submicron powder. Reaction orders with respect to CO and O2 were determined from the rates measured at various partial pressures of CO and O2 at 350 °C. The zero-order of the reaction with respect to Po2 was observed for CO oxidation over α-Fe2O3 submicron powder, while 0.48 order to Po2 was observed for CO oxidation over Pd/α-Fe2O3 submicron powder. The partial orders with respect to PCO were determined as 0.58 and 0.54 for the α-Fe2O3, and the Pd/α-Fe2O3 submicron powders, respectively. The kinetic results obtained from both catalysts were compared with those for the α-Fe2O3 fine powder catalysts and were used to understand the reaction mechanism.

Microstructure and magnetic properties of MFe2O4 (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method

Science.gov (United States)

Wang, Wei; Ding, Zui; Zhao, Xiruo; Wu, Sizhu; Li, Feng; Yue, Ming; Liu, J. Ping

2015-05-01

Three kinds of spinel ferrite nanocrystals, MFe2O4 (M = Co, Ni, and Mn), are synthesized using colloid mill and hydrothermal method. During the synthesis process, a rapid mixing and reduction of cations with sodium borohydride (NaBH4) take place in a colloid mill then through a hydrothermal reaction, a slow oxidation and structural transformation of the spinel ferrite nanocrystals occur. The phase purity and crystal lattice parameters are estimated by X-ray diffraction studies. Scanning electron microscopy and transmission electron microscopy images show the morphology and particle size of the as-synthesized ferrite nanocrystals. Raman spectrum reveals active phonon modes at room temperature, and a shifting of the modes implies cation redistribution in the tetrahedral and octahedral sites. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (Ms). Meanwhile, experiments demonstrate that the hydrothermal reaction time has significant effects on microstructure, morphologies, and magnetic properties of the as-synthesized ferrite nanocrystals.

Structural and magnetic properties of Ni0.15Mg0.1Cu0.3Zn0.45Fe2O4 ferrite prepared by NaOH-precipitation method

International Nuclear Information System (INIS)

Hou, Wei-xiao; Wang, Zhi

2015-01-01

Highlights: • NiMgCuZn ferrites were successfully prepared by low-temperature sintering. • NiMgCuZn ferrites have the advantages of both NiCuZn and MgCuZn ferrites. • NiMgCuZn ferrites exhibit high Curie temperature & high stability of permeability. - Abstract: The Ni 0.15 Mg 0.1 Cu 0.3 Zn 0.45 Fe 2 O 4 ferrite powders have been prepared by NaOH co-precipitation method and characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The XRD patterns confirm the single phase spinel structure of synthesized nanoparticles. The average crystallite size of the particles increases from 12 to 36 nm with calcining temperature (T a ) from 500 to 800 °C. The saturation magnetization (M s ) of the superparamagnetic particles was deduced by Langevin theory. Subsequently, the densification characteristics and magnetic properties of the low-temperature 950 °C-sintered ferrite bulk samples were also investigated. The magnetic measurement showed that the sintered bulk sample of T a = 600 °C has the highest initial permeability (μ i ), lowest coercivity (H c ), largest saturation magnetization (M s ) and satisfactory thermal stability of μ i . The microstructures of sintered samples were examined using field emission scanning electric microscope (FESEM). The T a has significant influence on the bulk density, initial permeability, saturation magnetization and coercivity of Ni 0.15 Mg 0.1 Cu 0.3 Zn 0.45 Fe 2 O 4 ferrite

Studies on magnetic properties of chemically synthesized crystalline calcium ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Debnath, A., E-mail: debnathanimesh@gmail.com [Department of Civil Engineering, National Institute of Technology Agartala, Jirania, West Tripura, 799046 India (India); Bera, A.; Saha, B. [Department of Physics, National Institute of Technology Agartala, Jirania, West Tripura 799046 (India); Chattopadhyay, K. K. [Department of Physics, Jadavpur University, Kolkata 700 032 (India)

2016-05-23

Spinel-type ferrites have taken a very important role for modern electronic industry. Most of these ferrites exhibit low-loss dielectric properties, high resistivity, low eddy current and also high temperature ferromagnetism. Calcium ferrite is one such important metal oxide which is environmentally safe, chemically stable, low cost and greatly abundant. This outstanding material of calcium ferrite is synthesized by a simple chemical precipitation method using NaOH as the precipitating agent. Ferric chloride anhydrous (FeCl{sub 3}) and Calcium chloride dihydrate (CaCl{sub 2}.2H{sub 2}O) were used as iron and calcium sources respectively. The samples were heated at 200°C for 8h to obtain homogeneous powder of Calcium ferrite. The powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission electrical microscopy (TEM), and Fourier transform infrared spectroscopic (FTIR) measurements. The polycrystalline nature of the sample was confirmed by X-ray diffraction study. The magnetic properties of the sample were investigated by vibrating sample magnetometer (VSM) measurements. Magnetization curve of the prepared sample depicts that as synthesized calcium ferrite nanoparticles have saturation magnetic moment of 1.74 emu/g and the coercivity of 35.08 Oe with superparamagnetic behavior. The synthesized calcium ferrite nanoparticles with such magnetic properties will be a candidate material for different applications in electronics and exploring its functionality in the field of recently developing semiconductor device physics and spintronics.

Studies on magnetic properties of chemically synthesized crystalline calcium ferrite nanoparticles

International Nuclear Information System (INIS)

Debnath, A.; Bera, A.; Saha, B.; Chattopadhyay, K. K.

2016-01-01

Spinel-type ferrites have taken a very important role for modern electronic industry. Most of these ferrites exhibit low-loss dielectric properties, high resistivity, low eddy current and also high temperature ferromagnetism. Calcium ferrite is one such important metal oxide which is environmentally safe, chemically stable, low cost and greatly abundant. This outstanding material of calcium ferrite is synthesized by a simple chemical precipitation method using NaOH as the precipitating agent. Ferric chloride anhydrous (FeCl_3) and Calcium chloride dihydrate (CaCl_2.2H_2O) were used as iron and calcium sources respectively. The samples were heated at 200°C for 8h to obtain homogeneous powder of Calcium ferrite. The powders were characterized by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Transmission electrical microscopy (TEM), and Fourier transform infrared spectroscopic (FTIR) measurements. The polycrystalline nature of the sample was confirmed by X-ray diffraction study. The magnetic properties of the sample were investigated by vibrating sample magnetometer (VSM) measurements. Magnetization curve of the prepared sample depicts that as synthesized calcium ferrite nanoparticles have saturation magnetic moment of 1.74 emu/g and the coercivity of 35.08 Oe with superparamagnetic behavior. The synthesized calcium ferrite nanoparticles with such magnetic properties will be a candidate material for different applications in electronics and exploring its functionality in the field of recently developing semiconductor device physics and spintronics.

Experimental study on the thrust modulation performance of powdered magnesium and CO2 bipropellant engine

Science.gov (United States)

Li, Chao; Hu, Chunbo; Zhu, Xiaofei; Hu, Jiaming; Li, Yue; Hu, Xu

2018-06-01

Powdered Mg and CO2 bipropellant engine providing a practical demonstration of in situ resource utilization (ISRU) for Mars Sample Return (MSR) mission seems to be feasible by current investigations. However, essential functions of the engine to satisfy the complicated ballistics requirements such as thrust modulation and multiple pulse have not been established yet. The aim of this experimental study is to evaluate the engine's thrust modulation feasibility and to investigate its thrust modulation characteristics. A powdered Mg and CO2 bipropellant engine construction aiming to achieve thrust modulation ability was proposed. A mass flow rate calibration experiment to evaluate the gas-solid mass flow rate regulating performance was conducted before fire tests. Fire test result shows that the engine achieved successful ignition as well as self-sustaining combustion; Thrust modulation of the engine is feasible, detail thrust estimating result of the test shows that maximum thrust is 135.91 N and the minimum is 5.65 N with a 22.11 thrust modulation ratio, moreover, the transportation period is quick and the thrust modulation ratio is adjustable. At the same time, the powder feed system reaches a two-step flow rate regulating with a modulation ratio of 4.5-5. What' more, caused by the uneven engine working conditions, there is an obvious difference in combustion efficiency value, maximum combustion efficiency of the powdered Mg and CO2 bipropellant engine is 80.20%.

Electromagnetic properties of photodefinable barium ferrite polymer composites

Science.gov (United States)

Sholiyi, Olusegun; Lee, Jaejin; Williams, John D.

2014-07-01

This article reports the magnetic and microwave properties of a Barium ferrite powder suspended in a polymer matrix. The sizes for Barium hexaferrite powder are 3-6 μm for coarse and 0.8-1.0 μm for the fine powder. Ratios 1:1 and 3:1 (by mass) of ferrite to SU8 samples were characterized and analyzed for predicting the necessary combinations of these powders with SU8 2000 Negative photoresist. The magnetization properties of these materials were equally determined and were analyzed using Vibrating Sample Magnetometer (VSM). The Thru, Reflect, Line (TRL) calibration technique was employed in determining complex relative permittivity and permeability of the powders and composites with SU8 between 26.5 and 40 GHz.

Electromagnetic properties of photodefinable barium ferrite polymer composites

Directory of Open Access Journals (Sweden)

Olusegun Sholiyi

2014-07-01

Full Text Available This article reports the magnetic and microwave properties of a Barium ferrite powder suspended in a polymer matrix. The sizes for Barium hexaferrite powder are 3–6 μm for coarse and 0.8–1.0 μm for the fine powder. Ratios 1:1 and 3:1 (by mass of ferrite to SU8 samples were characterized and analyzed for predicting the necessary combinations of these powders with SU8 2000 Negative photoresist. The magnetization properties of these materials were equally determined and were analyzed using Vibrating Sample Magnetometer (VSM. The Thru, Reflect, Line (TRL calibration technique was employed in determining complex relative permittivity and permeability of the powders and composites with SU8 between 26.5 and 40 GHz.

Evaluation of magnetic properties of NI-ZN ferrites obtained by different synthesis methods

International Nuclear Information System (INIS)

Simoes, A.N.; Neiva, L.S.; Simoes, V.N.; Gama, L.; Gomes Filho, A.C.; Oliveira, J.B.L.

2012-01-01

Ceramic oxides that exhibit ferromagnetic behavior represent important commercial products for the electronics industry and are commonly known as ferrites. The Ni-Zn ferrites are considered to be one of the most versatile and soft due to its high electrical resistivity and low eddy current losses. Thus, this study aims to evaluate the magnetic properties of Ni-Zn ferrite obtained by the Pechini and combustion reaction. After synthesis the powders were characterized by XRD, SEM, BET and magnetic measurements. The results showed that for both methods of synthesis used was the formation of the spinel phase of Ni-Zn ferrite. The micrographs show that the powders obtained by both methods have regular shapes and spherical. Were determined by BET surface area is 26 m 2 /g by the Pechini and 13 m 2 /g by combustion. And the samples synthesized by Pechini method obtained the best magnetic characteristics (author)

Jingle-bell-shaped ferrite hollow sphere with a noble metal core: Simple synthesis and their magnetic and antibacterial properties

International Nuclear Information System (INIS)

Li Siheng; Wang Enbo; Tian Chungui; Mao Baodong; Kang Zhenhui; Li Qiuyu; Sun Guoying

2008-01-01

In this paper, a simple strategy is developed for rational fabrication of a class of jingle-bell-shaped hollow structured nanomaterials marked as Ag(MFe 2 O 4 ) (M=Ni, Co, Mg, Zn), consisting of ferrite hollow shells and metal nanoparticle cores, using highly uniform colloidal Ag(C) microspheres as template. The final composites were obtained by direct adsorption of metal cations Fe 3+ and M 2+ on the surface of the Ag(C) spheres followed by calcination process to remove the middle carbon shell and transform the metal ions into pure phase ferrites. The as-prepared composites were characterized by X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy and SQUID magnetometer. The results showed that the composites possess the magnetic property of the ferrite shell and the optical together with antibacterial property of the Ag core. - Graphical abstract: MFe 2 O 4 (M=Ni, Co, Mg, Zn) hollow spheres with a noble metal nanoparticle core were successfully prepared by using colloidal metal(C) core-shell spheres as templates with no need of surface modification. The shell thickness and magnetic properties of the ferrite hollow spheres could be controlled by varying the synthetic parameters

AC conductivity and dielectric properties of Ti-doped CoCr{sub 1.2}Fe{sub 0.8}O{sub 4} spinel ferrite

Energy Technology Data Exchange (ETDEWEB)

Elkestawy, M.A., E-mail: mkestawy@hotmail.co [Physics Department, Faculty of Science, Suez Canal University, Suez (Egypt); Abdel kader, S.; Amer, M.A. [Physics Department, Faculty of Science, Tanta University, Tanta (Egypt)

2010-01-15

Dielectric properties of spinel ferrite samples Co{sub 1+x}Ti{sub x}Cr{sub 1.2-2x}Fe{sub 0.8}O{sub 4} (0<=x<=0.5) were investigated as a function of frequency at different temperatures using a complex impedance technique. Also Cole-Cole diagrams of both permittivity and electric modulus were investigated at different temperatures to have an insight into the electric nature of the studied solids. It has been found that the electric modulus M* is the dominating property clarifying the intrinsic picture of these polycrystalline ferrites. The low conductivity and loss factor values indicate that the studied compositions may be good candidates for practical applications.

Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Rieken, Joel [Iowa State Univ., Ames, IA (United States)

2011-12-13

Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O₂) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

A Hierarchical Z-Scheme α-Fe2 O3 /g-C3 N4 Hybrid for Enhanced Photocatalytic CO2 Reduction.

Science.gov (United States)

Jiang, Zhifeng; Wan, Weiming; Li, Huaming; Yuan, Shouqi; Zhao, Huijun; Wong, Po Keung

2018-03-01

The challenge in the artificial photosynthesis of fossil resources from CO 2 by utilizing solar energy is to achieve stable photocatalysts with effective CO 2 adsorption capacity and high charge-separation efficiency. A hierarchical direct Z-scheme system consisting of urchin-like hematite and carbon nitride provides an enhanced photocatalytic activity of reduction of CO 2 to CO, yielding a CO evolution rate of 27.2 µmol g -1 h -1 without cocatalyst and sacrifice reagent, which is >2.2 times higher than that produced by g-C 3 N 4 alone (10.3 µmol g -1 h -1 ). The enhanced photocatalytic activity of the Z-scheme hybrid material can be ascribed to its unique characteristics to accelerate the reduction process, including: (i) 3D hierarchical structure of urchin-like hematite and preferable basic sites which promotes the CO 2 adsorption, and (ii) the unique Z-scheme feature efficiently promotes the separation of the electron-hole pairs and enhances the reducibility of electrons in the conduction band of the g-C 3 N 4 . The origin of such an obvious advantage of the hierarchical Z-scheme is not only explained based on the experimental data but also investigated by modeling CO 2 adsorption and CO adsorption on the three different atomic-scale surfaces via density functional theory calculation. The study creates new opportunities for hierarchical hematite and other metal-oxide-based Z-scheme system for solar fuel generation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructural characterization of ODS ferritic steels at different processing stages

Energy Technology Data Exchange (ETDEWEB)

Gil, E., E-mail: egil@ceit.es; Ordás, N.; García-Rosales, C.; Iturriza, I., E-mail: iiturriza@ceit.es

2015-10-15

Highlights: • ODS ferritic stainless steel produced by new route without mechanical alloying. • Fully dense ferritic stainless steels containing Y and Ti were obtained by HIPping. • Y and Ti-rich precipitates prevent grain growth during heat treatment up to 1320 °C. • HIPping at 1220 °C dissolves the metastable oxides on PPBs. - Abstract: Nanostructured Oxide Dispersion Strengthened Reduced Activation Ferritic Stainless Steels (ODS RAF) are promising structural materials for fusion reactors, due to their ultrafine microstructure and the presence of a dispersion of Y–Ti–O nanoclusters that provide excellent creep strength at high temperatures (up to 750 °C). The traditional powder metallurgical route to produce these steels is based on Gas Atomization (GA) + Mechanical Alloying (MA) + HIP + ThermoMechanical Treatments (TMTs). Recently, alternative methods have arisen to avoid the MA step. In line with this new approach, ferritic stainless steel powders were produced by gas atomization and HIPped, after adjusting their oxygen, Y and Ti contents to form Y–Ti–O nanoclusters during subsequent heat treatments. The microstructure of as-HIPped steels mainly consists of ferrite grains, Y–Ti precipitates, carbides and oxides on Prior Particle Boundaries (PPBs). Post-HIP heat treatments performed at high temperatures (1270 and 1300 °C) evaluated the feasibility of achieving a complete dissolution of the oxides on PPBs and a precipitation of ultrafine Ti- and Y-rich oxides in the Fe14Cr2W matrix. FEG-SEM with extensive EDS analysis was used to characterize the microstructure of the atomized powders and the ODS-RAF specimens after HIP consolidation and post-HIP heat treatments. A deeper characterization of atomized powder was carried out by TEM.

Tuning Fermi level of Cr{sub 2}CoZ (Z=Al and Si) inverse Heusler alloys via Fe-doping for maximum spin polarization

Energy Technology Data Exchange (ETDEWEB)

Singh, Mukhtiyar [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India); Saini, Hardev S. [Department of Physics, Panjab University, Chandigarh-160014 (India); Thakur, Jyoti [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India); Reshak, Ali H. [New Technologies—Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Kashyap, Manish K., E-mail: manishdft@gmail.com [Department of Physics, Kurukshetra University, Kurukshetra-136119, Haryana (India)

2014-12-15

We report full potential treatment of electronic and magnetic properties of Cr{sub 2−x}Fe{sub x}CoZ (Z=Al, Si) Heusler alloys where x=0.0, 0.25, 0.5, 0.75 and 1.0, based on density functional theory (DFT). Both parent alloys (Cr{sub 2}CoAl and Cr{sub 2}CoSi) are not half-metallic frromagnets. The gradual replacement of one Cr sublattice with Fe induces the half-metallicity in these systems, resulting maximum spin polarization. The half-metallicity starts to appear in Cr{sub 2−x}Fe{sub x}CoAl and Cr{sub 2−x}Fe{sub x}CoSi with x=0.50 and x=0.25, respectively, and the values of minority-spin gap and half-metallic gap or spin-flip gap increase with further increase of x. These gaps are found to be maximum for x=1.0 for both cases. An excellent agreement between the structural properties of CoFeCrAl with available experimental study is obtained. The Fermi level tuning by Fe-doping makes these alloys highly spin polarized and thus these can be used as promising candidates for spin valves and magnetic tunnelling junction applications. - Highlights: • Tuning of E{sub F} in Cr{sub 2}CoZ (Z=Al, Si) has been demonstrated via Fe doping. • Effect of Fe doping on half-metallicity and magnetism have been discussed. • The new alloys have a potential of being used as spin polarized electrodes.

A study of magnetoplumbite-type (M-type) cobalt-titanium-substituted barium ferrite, BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6)

Energy Technology Data Exchange (ETDEWEB)

Teh, G.B. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia)], E-mail: tehgb@mail.utar.edu.my; Saravanan, N. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia); Jefferson, D.A. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

2007-10-15

Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe{sub 12}O{sub 19} were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo{sub 3}Ti{sub 3}Fe{sub 6}O{sub 19} showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected.

Structural investigation of chemically synthesized ferrite magnetic nanomaterials

Science.gov (United States)

Uyanga, E.; Sangaa, D.; Hirazawa, H.; Tsogbadrakh, N.; Jargalan, N.; Bobrikov, I. A.; Balagurov, A. M.

2018-05-01

In recent times, interest in ferrite magnetic nanomaterials has considerably grown, mainly due to their highly promising medical and biological applications. Spinel ferrite powder samples, with high heat generation abilities in AC magnetic fields, were studied for their application to the hyperthermia treatment of cancer tumors. These properties of ferrites strongly depend on their chemical composition, ion distribution between crystallographic positions, magnetic structure and method of preparation. In this study, crystal and magnetic structures of several magnetic spinels were investigated by neutron diffraction. The explanation of the mechanism triggering the heat generation ability in the magnetic materials, and the electronic and magnetic states of ferrite-spinel type structures, were theoretically defined by a first-principles method. Ferrites with the composition of CuxMg1-xFe2O4 have been investigated as a heat generating magnetic nanomaterial. Atomic fraction of copper in ferrite was varied between 0 and 100% (that is, x between 0 and 1.0 with 0.2 steps), with the copper dope limit corresponding to appear a tetragonal phase.

Structural and magnetic characterization of co-precipitated Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Srinivas, Ch., E-mail: srinivas.chintoju75@gmail.com [Department of Physics, Sasi Institute of Technology and Engineering, Tadepalligudem 534101 (India); Tirupanyam, B.V. [Department of Physics, Government College (Autonomous), Rajamahendravaram 533103 (India); Meena, S.S.; Yusuf, S.M. [Solid State Physics Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Babu, Ch. Seshu [Department of Physics, Sasi Institute of Technology and Engineering, Tadepalligudem 534101 (India); Ramakrishna, K.S. [Department of Physics, Srinivasa Institute of Engineering and Technology, Amalapuram 533222 (India); Potukuchi, D.M. [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University, Kakinada 533003 (India); Sastry, D.L., E-mail: dl_sastry@rediffmail.com [Department of Physics, Andhra University, Visakhapatnam 530003 (India)

2016-06-01

A series of Ni{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} (x=0.5, 0.6 and 0.7) ferrite nanoparticles have been synthesized using a co-precipitation technique, in order to understand the doping effect of nickel on their structural and magnetic properties. XRD and FTIR studies reveal the formation of spinel phase of ferrite samples. Substitution of nickel has promoted the growth of crystallite size (D), resulting the decrease of lattice strain (η). It was also observed that the lattice parameter (a) increases with the increase of Ni{sup 2+} ion concentration. All particles exhibit superparamagnetism at room temperature. The hyperfine interaction increases with the increase of nickel substitution, which can be assumed to the decrease of core–shell interactions present in the nanoparticles. The Mössbauer studies witness the existence of Fe{sup 3+} ions and absence of Fe{sup 2+} ions in the present systems. These superparamagnetic nanoparticles are supposed to be potential candidates for biomedical applications. The results are interpreted in terms of microstructure, cation redistribution and possible core–shell interactions. - Highlights: • Thermodynamic solubility of Ni{sup 2+} in zinc ferrite influences the crystallite sizes. • At room temperature the ferrite systems exhibit superparamagnetism. • Core–shell model was exactly suited to explain magnetic behavior. • Core–shell interactions decrease with increase in Ni{sup 2+} ion concentration.

Development of Ferrite-Coated Soft Magnetic Composites: Correlation of Microstructure to Magnetic Properties

Science.gov (United States)

Sunday, Katie Jo

Soft magnetic composites (SMCs) comprised of ferrite-coated ferrous powder permit isotropic magnetic flux capabilities, lower core losses, and complex designs through the use of traditional powder metallurgy techniques. Current coating materials and methods are vastly limited by the nonmagnetic properties of organic and some inorganic coatings and their inability to withstand high heat treatments for proper stress relief of core powder after compaction. Ferrite-based coatings are ferrimagnetic, highly resistive, and boast high melting temperatures, thus providing adequate electrical barriers between metallic particles. These insulating layers are necessary for reducing eddy current losses by increasing resistivity in order to improve the overall magnetic efficiency and subsequent frequency range. The goals of this work are to correlate ferrite-coated Fe powder composites microstructure for the coating and core powder to magnetic properties such as permeability, coercivity, and core loss. We first explore the relevant concepts of SMC materials from their composition to processing steps to pertinent properties. This thesis employs a suite of characterization techniques for powder and composite properties. We use X-ray diffraction, scanning electron microscopy, and transmission electron microscopy to provide a complete understanding of the effect of processing conditions on ferrite-coated Fe-based SMCs. Magnetic, mechanical, and electrical properties are then analyzed to correlate microstructural features and determine their effect on such properties. In the second part of this thesis, we present a proof of concept study on Al2O3- and Al2O3- Fe3O4-coated Fe powder composites, illustrating magnetization is highly dependent on ferromagnetic volume. We then expand on previous work to compare an ideal, crystalline state using Fe3O 4-Fe thin film heterostructures to a highly strained state using bulk powder studies. Fe3O4-coated Fe composites are produced via mechanical

Surface effects on the magnetic behavior of nanocrystalline nickel ferrites and nickel ferrite-polymer nanocomposites

International Nuclear Information System (INIS)

Nathani, H.; Misra, R.D.K.

2004-01-01

The magnetization studies on nanocrystalline nickel ferrite as powder particles, and as diluted dispersion (10 wt.%) in polymer matrix (polymer nanocomposites) are presented. The two polymer-based nanocomposites were prepared via ball-milling and in situ polymerization, respectively. The magnetization measurements provide strong evidence of surface effects to magnetization, which explains the non-saturation of magnetization at high fields. The differences in the magnetization behavior of nickel ferrite as powder particles and in the ball-milled nanocomposite and the nanocomposite prepared via in situ polymerization are attributed to the different extent of interparticle interactions between the particles and the preparation route. The magnetization versus applied field behavior of the three ferrite systems show a similar jump in the initial part of the magnetization curve in all the cases which implies the existence of a core-shell like morphology of the particles over a large temperature range and its dominance over the interparticle interaction effects between the particles

Study of structural phase transformation and hysteresis behavior of inverse-spinel α-ferrite nanoparticles synthesized by co-precipitation method

Science.gov (United States)

Dabagh, Shadab; Chaudhary, Kashif; Haider, Zuhaib; Ali, Jalil

2018-03-01

Substitution of cobalt (Co2+) ions in cobalt ferrite (CoFe2O4) with copper (Cu2+) and aluminum (Al3+) ions allows variations in their electric and magnetic properties which can be optimized for specific applications. In this article, synthesis of inverse-spinel Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) nanoparticles by substituting Cu2+ and Al3+ ions in CoFe2O4 via co-precipitation method is reported. By controlling copper and aluminum (Cu-Al) substituent ratio, the magnetic moment and coercivity of synthesized cobalt ferrite nanoparticles is optimized. The role of substituents on the structure, particle size, morphology, and magnetic properties of nano-crystalline ferrite is investigated. The Co1-xCuxFe2-xAlxO4 (0.0 ≤ x≤ 0.8) nanoparticles with crystallite size in the range of 23.1-26.5 nm are observed, 26.5 nm for x = 0.0-23.1 nm for x = 0.8. The inverse-spinel structure of synthesized Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) nano-particles is confirmed by characteristic vibrational bands at tetrahedral and octahedral sites using Fourier transform infrared spectroscopy. A decreases in coercive field and magnetic moment is observed as Cu-Al contents are increased (x = 0.0-0.8). The positive anisotropy of synthesized particles Co1-xCuxFe2-xAlxO4 (0.0 ≤ x ≤ 0.8) is obtained in the range 1.96 × 105 J/m3 for x = 0.0 to 0.29 × 105 J/m3 for x = 0.8.

A CO2 laser based system for the production of nanoscaled powders

International Nuclear Information System (INIS)

Kurland, H.-D.; Schindler, K.; Staupendahl, G.; Oestreich, Ch.; Loogk, M.; Mueller, E.

2002-01-01

Nowadays the world-wide industrial competition is increasingly determined by the use of new materials which allow optimised and in part totally new qualities of products or the production of more compact components. Thereby the importance of ultrafine ceramic powders with grain sizes of only a few nanometers rises rapidly. These powders show some interesting physical and chemical features which result from the extremely small dimensions of their particles, for example very high specific surfaces, high surface energy or special behaviour in the phase transformation. Their thermodynamic and kinetic (short diffusion lengths) parameters are mirrored in high sintering activities and hence relatively low sintering temperatures as well as very special properties of the sintered materials, especially the possibility of super plasticity. Nanoscaled powders also have a broad potential for the production of thin layers for example in the electronics industry or as part of composite materials with components of lower thermal stability. At present different technologies for the manufacturing of nanoscaled powders are intensively used and developed. In this paper a technique for the production of ceramic nanopowders by evaporation of solid starting materials with CO 2 laser radiation is presented

Modified solvothermal synthesis of cobalt ferrite (CoFe2O4 magnetic nanoparticles photocatalysts for degradation of methylene blue with H2O2/visible light

Directory of Open Access Journals (Sweden)

Abul Kalam

2018-03-01

Full Text Available Different grads of magnetic nano-scaled cobalt ferrites (CoFe2O4 photocatalysts were synthesized by modified Solvothermal (MST process with and without polysaccharide. The indigenously synthesized photocatalysts were characterized by means of X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM, thermo gravimetric analysis (TGA, Fourier transform infrared (FT-IR, UV–visible (UV–vis spectroscopy and N2 adsorption–desorption isotherm method. The Fourier transform infrared spectroscopy study showed the Fe-O stretching vibration 590–619 cm−1, confirming the formation of metal oxide. The crystallite size of the synthesized photocatalysts was found in the range between 20.0 and 30.0 nm. The surface area of obtained magnetic nanoparticles is found to be reasonably high in the range of 63.0–76.0 m2/g. The results shown that only MST-2 is the most active catalyst for photo-Fenton like scheme for fast photodegradation action of methylene blue dye, this is possible due to optical band gap estimated of 2.65 eV. Captivatingly the percentage of degradation efficiency increases up to 80% after 140 min by using MST-2 photocatalyst. Photocatalytic degradation of methylene blue (MB dye under visible light irradiation with cobalt ferrite magnetic nanoparticles followed first order kinetic constant and rate constant of MST-2 is almost 2.0 times greater than MST-1 photocatalyst. Keywords: Cobalt ferrite, Photocatalysis, Kinetics, Optical properties, Surface area studies

Microstructure and magnetic properties of MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei, E-mail: wangwei@mail.buct.edu.cn; Ding, Zui; Zhao, Xiruo [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing 100029 (China); Wu, Sizhu [State Key Laboratory of Organic–Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Li, Feng [State Key Laboratory of Chemical Resource Engineering and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Yue, Ming [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China); Liu, J. Ping [Department of Physics, University of Texas at Arlington, Arlington, Texas 76019 (United States)

2015-05-07

Three kinds of spinel ferrite nanocrystals, MFe{sub 2}O{sub 4} (M = Co, Ni, and Mn), are synthesized using colloid mill and hydrothermal method. During the synthesis process, a rapid mixing and reduction of cations with sodium borohydride (NaBH{sub 4}) take place in a colloid mill then through a hydrothermal reaction, a slow oxidation and structural transformation of the spinel ferrite nanocrystals occur. The phase purity and crystal lattice parameters are estimated by X-ray diffraction studies. Scanning electron microscopy and transmission electron microscopy images show the morphology and particle size of the as-synthesized ferrite nanocrystals. Raman spectrum reveals active phonon modes at room temperature, and a shifting of the modes implies cation redistribution in the tetrahedral and octahedral sites. Magnetic measurements show that all the obtained samples exhibit higher saturation magnetization (M{sub s}). Meanwhile, experiments demonstrate that the hydrothermal reaction time has significant effects on microstructure, morphologies, and magnetic properties of the as-synthesized ferrite nanocrystals.

Lattice parameter values and phase transitions for the Cu2Cd1-zMn zGeSe4 and Cu2Cd1-zFe zGeSe4 alloys

International Nuclear Information System (INIS)

Quintero, E.; Tovar, R.; Quintero, M.; Delgado, G.E.; Morocoima, M.; Caldera, D.; Ruiz, J.; Mora, A.E.; Briceno, M.; Fernandez, J.L.

2007-01-01

X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu 2 Cd 1-z Mn z GeSe 4 and Cu 2 Cd 1-z Fe z GeSe 4 alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu 2 Cd 1-z Fe z GeSe 4 system, only two single solid phase fields, the tetragonal stannite α and the wurtz-stannite δ structures were found to occur in the diagram. For the Cu 2 Cd 1-z Mn z GeSe 4 system, in addition to the tetragonal stannite α and the wurtz-stannite δ phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling

Magnetic hyperthermia heating of cobalt ferrite nanoparticles prepared by low temperature ferrous sulfate based method

Directory of Open Access Journals (Sweden)

Tejabhiram Yadavalli

2016-05-01

Full Text Available A facile low temperature co-precipitation method for the synthesis of crystalline cobalt ferrite nanostructures using ferrous sulfate salt as the precursor has been discussed. The prepared samples were compared with nanoparticles prepared by conventional co-precipitation and hydrothermal methods using ferric nitrate as the precursor. X-ray diffraction studies confirmed the formation of cubic spinel cobalt ferrites when dried at 110 °C as opposed to conventional methods which required higher temperatures/pressure for the formation of the same. Field emission scanning electron microscope studies of these powders revealed the formation of nearly spherical nanostructures in the size range of 20-30 nm which were comparable to those prepared by conventional methods. Magnetic measurements confirmed the ferromagnetic nature of the cobalt ferrites with low magnetic remanance. Further magnetic hyperthermia studies of nanostructures prepared by low temperature method showed a rise in temperature to 50 °C in 600 s.

Synthesis and Characterization of Oxide Dispersion Strengthened Ferritic Steel via a Sol-Gel Route

International Nuclear Information System (INIS)

Sun Qinxing; Zhang Tao; Wang Xianping; Fang Qianfeng; Hu Jing; Liu Changsong

2012-01-01

Nanocrystalline oxide dispersion strengthened (ODS) ferritic steel powders with nominal composition of Fe-14Cr-3W-0.3Ti-0.4Y 2 O 3 are synthesized using sol-gel method and hydrogen reduction. At low reduction temperature the impurity phase of CrO is detected. At higher reduction temperature the impurity phase is Cr 2 O 3 which eventually disappears with increasing reduction time. A pure ODS ferritic steel phase is obtained after reducing the sol-gel resultant products at 1200°C for 3 h. The HRTEM and EDS mapping indicate that the Y 2 O 3 particles with a size of about 15 nm are homogenously dispersed in the alloy matrix. The bulk ODS ferritic steel samples prepared from such powders exhibit good mechanical performance with an ultimate tensile stress of 960 MPa.

Study of kinetics of reaction of lithium deuteride powder with O2, CO2 and water vapor

International Nuclear Information System (INIS)

Li Gan; Lu Guangda; Jing Wenyong; Qin Cheng

2004-01-01

The kinetics of reaction of lithium deuteride powder with O 2 , CO 2 and water vapor is studied. The experimental results show that lithium deuteride reacts with O 2 and CO 2 at very small reaction rate but with water vapor at comparatively larger rate at room temperature (≅28 degree C). The reaction process with water vapor could be described using the unreacted shrinking core model. The second-order kinetics is appropriate for the chemical reaction on the surface of lithium deuteride and reaction rate constant is 0.281 kPa -1 ·min -1

Phase and morphology evolution of (Na1-xKxNbO3 powders related to calcinations and K2CO3 content

Directory of Open Access Journals (Sweden)

Steven J. Milne

2007-03-01

Full Text Available Sodium-potassium niobate ((Na1-xKxNbO3 powders with x = 0.2, 0.4, 0.6 and 0.8 were prepared following the conventional mixed oxide method and characterized by TG-DTA, XRD and SEM techniques.The effects of calcination temperature, dwell time and K2CO3 content on phase formation behavior and morphology of the powders were investigated. The calcination temperature and dwell time were found tohave a pronounced effect on the phase formation of the calcined sodium-potassium niobate powders. It was found that the crystallized phase depended on calcination conditions. The high calcination temperature andlong dwell time clearly favored particle growth and the formation of large and hard agglomerates. All the (Na1-xKxNbO3 powders showed a similar orthorhombic phase structure. The K2CO3 content significantlyaffected the calcination temperature and particle size and shape. Large particle size, cubic shape and a lower calcined condition were observed in (Na1-xKxNbO3 powder with low K2CO3 content (x = 0.2.

Coprecipitation synthesis of zinc ferrit (FE 2 O 3 /ZNO) nanoparticles ...

African Journals Online (AJOL)

Zinc ferrite (Fe2O3/ZnO) nanocomposites were successfully synthesized by simple co-precipitation method via iron (III) nitrate 9-hydrate (Fe(NO3)3.9H2O) and zinc nitrate hexahydrate (Zn(NO3)2.6H2O) as precursor in the presence of cetyltrimethylammonium bromide (CTAB) surfactant. The samples were characterized by ...

Jingle-bell-shaped ferrite hollow sphere with a noble metal core: Simple synthesis and their magnetic and antibacterial properties

Science.gov (United States)

Li, Siheng; Wang, Enbo; Tian, Chungui; Mao, Baodong; Kang, Zhenhui; Li, Qiuyu; Sun, Guoying

2008-07-01

In this paper, a simple strategy is developed for rational fabrication of a class of jingle-bell-shaped hollow structured nanomaterials marked as Ag@ MFe 2O 4 ( M=Ni, Co, Mg, Zn), consisting of ferrite hollow shells and metal nanoparticle cores, using highly uniform colloidal Ag@C microspheres as template. The final composites were obtained by direct adsorption of metal cations Fe 3+ and M 2+ on the surface of the Ag@C spheres followed by calcination process to remove the middle carbon shell and transform the metal ions into pure phase ferrites. The as-prepared composites were characterized by X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy and SQUID magnetometer. The results showed that the composites possess the magnetic property of the ferrite shell and the optical together with antibacterial property of the Ag core.

Synthesis and magnetic properties of CoFe2O4 spinel ferrite nanoparticles doped with lanthanide ions

International Nuclear Information System (INIS)

Kahn, Myrtil L.; Zhang, Z. John

2001-01-01

Lanthanide ions have been doped into cobalt spinel ferrites using an oil-in-water micellar method to form CoLn 0.12 Fe 1.88 O 4 nanoparticles with Ln=Ce, Sm, Eu, Gd, Dy, or Er. Doping with lanthanide ions (Ln III ) modulates the magnetic properties of cobalt spinel ferrite nanoparticles. In particular cases of Gd 3+ or Dy 3+ ions, a dramatic increase in the blocking temperature and coercivity is observed. Indeed, the introduction of only 4% of Gd 3+ ions increases the blocking temperature ∼100 K and the coercivity 60%. Initial studies on the magnetic properties of these doped nanoparticles clearly demonstrate that the relationship between the modulation of magnetic properties and the nature of doped Ln III ions is interesting but very complex. [copyright] 2001 American Institute of Physics

High yttria ferritic ODS steels through powder forging

Science.gov (United States)

Kumar, Deepak; Prakash, Ujjwal; Dabhade, Vikram V.; Laha, K.; Sakthivel, T.

2017-05-01

Oxide dispersion strengthened (ODS) steels are being developed for future nuclear reactors. ODS Fe-18%Cr-2%W-0.2%Ti steels with 0, 0.35, 0.5, 1 and 1.5% Y2O3 (all compositions in weight%) dispersion were fabricated by mechanical alloying of elemental powders. The powders were placed in a mild steel can and forged in a stream of hydrogen gas at 1473 K. The steels were forged again to final density. The strength of ODS steel increased with yttria content. Though this was accompanied by a decrease in tensile elongation, all the steels showed significant ductility. The ductility in high yttria alloys may be attributed to improved inter-particle bonding between milled powders due to reduction of surface oxides by hydrogen. This may permit development of ODS steels with yttria contents higher than the conventional limit of 0.5%. It is suggested that powder forging is a promising route to fabricate ODS steels with high yttria contents and improved ductility.

Investigation of the oxidative processes in intermetallic Sm Co5 powder during heat treatment

International Nuclear Information System (INIS)

Talijan, Nadezda M.; Milutinovic-Nikolic, Aleksandra; Stajic-Trosic, Jasna T.; Jovanovic, Zarko D.

1996-01-01

Understanding of the thermal stability of intermetallic Sm Co 5 powder is essential for designing the working atmosphere in all phases of the technological procedure in the production of sintered Sm Co 5 magnets to obtain maximal magnetic properties. The thermal stability of the Sm Co 5 powder with defined chemical composition and particle size was investigated in the interval from 20 to 900 deg C. Commercial Sm Co 5 powder was used in this experiment. The powder was milled in anhydrous toluene in an agate mortar to fine powder of quality used in the production of sintered magnets. All the experiments were carried out with powder of an average particle size of 7.23μm, established by SEM. THe thermal stability of the Sm Co 5 powder in static air atmosphere was investigated by thermogravimetric analysis (TGA) using a DuPont Thermal Analyzer. Investigation of the behaviour of Sm Co 5 powder during heating was carried out using new samples of Sm Co 5 powder for each of the investigated temperature cycles. It was found by TGA that up to 200 deg C, the oxidation of Sm Co 5 was negligible. X-ray diffraction of the thermogravimetric experimental residue of the Sm Co 5 powder, heated at 240 deg C, yielded only the presence of the Sm Co 5 phase. By X-ray diffraction different crystal forms were identified depending on the maximal heating temperature. The following phases were identified: Sm 2 O 3 , Co, Co O, Co 3 O 4 and Sm Co O 3 . According to TG and X-ray results, for each of the investigated temperatures, the corresponding chemical reactions were established. The experimental data from both the thermal and X-ray investigations confirm that the phases of pressing and aligning the Sm Co 5 powder, in the process of producing sintered Sm Co 5 magnets, may be performed without a protective atmosphere. (author)

Study of transport properties and conduction mechanism of pure and composite resorcinol formaldehyde aerogel doped with Co-ferrite

International Nuclear Information System (INIS)

Attia, S.M.; Sharshar, T.; Abd-Elwahed, A.R.; Tawfik, A.

2013-01-01

Highlights: • A novel composite RF aerogels with Co-ferrite were prepared by sol–gel process. • RF aerogels exhibit a semiconducting behavior. • The dielectric constant of RF aerogel is very low (4 times as that of air) and can be controlled by adding Co-ferrite. • Large overlapping polaron (OLP) was found to be the preferred conduction mechanism in these materials. -- Abstract: A series of resorcinol formaldehyde aerogels (RF aerogels) composite with nanoparticles of CoFe 2 O 4 have been prepared by sol–gel method. Four samples of pure RF aerogels were prepared at different concentrations of Na 2 CO 3 as catalyst (0.02, 0.025, 0.03, and 0.04 wt.%) and four samples of composite RF aerogels were prepared at different concentration of doped CoFe 2 O 4 (0.075, 0.1, 0.125, and 0.15 wt.%; Na 2 CO 3 concentration = 0.03 wt.%). DC electrical conductivity as a function of temperature was studied in the temperature range 25 °C–200 °C for all samples. AC electrical conductivity and dielectric properties were determined using RLC Bridge in the frequency range 100 Hz–1 MHz at different temperature (25–200 °C). The pore size of the samples was determined using positron annihilation lifetime spectroscopy (PALS). RF aerogels are found to exhibit a semiconducting behavior and characterized by two transition temperatures T 1 and T 2 . Also σ DC increases with increase of Co-ferrite contents. Pure RF aerogels posses a very low dielectric constant, where the lowest value of ε′ is ∼4 times as that of air. ε′ decreases with increase of frequency, and increases with increase of temperature. Large overlapping polaron (OLP) is found to be the preferred conduction mechanism in these materials. The results of PALS show that there are two types of pore size in these samples; the first ranges from 1.9 to 2.5 nm, while the second ranges from 3.2 to 5.3 nm

Synthesis and characterization of hexagonal ferrite Sr{sub 1.8}Sm{sub 0.2}Co{sub 2}Ni{sub 1.50}Fe{sub 10.50}O{sub 22}/PST thin films for high frequency application

Energy Technology Data Exchange (ETDEWEB)

Ali, Irshad, E-mail: irshadalibzu@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan P.O. 60800 (Pakistan); Islam, M.U. [Department of Physics, Bahauddin Zakariya University, Multan P.O. 60800 (Pakistan); Ashiq, Muhammad Naeem, E-mail: naeemashiqqau@yahoo.com [Institute of Chemical Science, Bahauddin Zakariya University, Multan 60800 (Pakistan); Asif Iqbal, M. [Department of Physics, Bahauddin Zakariya University, Multan P.O. 60800 (Pakistan); College of E & ME, National University of Science and Technology, Islamabad (Pakistan); Karamat, Nazia [Institute of Chemical Science, Bahauddin Zakariya University, Multan 60800 (Pakistan); Azhar Khan, M. [Department of Physics, Islamia University, Bahawalpur 63100 (Pakistan); Sadiq, Imran [Centre of Excellence in Solid State Physics, University of The Punjab, Lahore (Pakistan); Ijaz, Sana [Institute of Chemical Science, Bahauddin Zakariya University, Multan 60800 (Pakistan); Shakir, Imran [Sustainable Energy Technologies (SET) Center, College of Engineering, King Saud University (Saudi Arabia)

2015-11-01

Y-type hexagonal ferrite (Sr{sub 1.8}Sm{sub 0.2}Co{sub 2}Ni{sub 1.50} Fe{sub 10.50}O{sub 22}) was prepared by a normal microemulsion route. The ferrite/polymer composites thin films are formed at different ferrite ratios in pure polystyrene matrix. The X-ray diffraction analysis shows broad peak at low angles which is due to the PST and the peaks for Y-type ferrite are also observed in composite samples. The peaks become more intense and show less broadening with increasing concentration of ferrite which suggests that crystallinity is improved with the addition of ferrite. DC resistivity of the composites samples is lower than that of the pure PST and decreases by increasing ferrite filler into the polymer. This decrease of resistivity is mainly due to the addition of comparatively less resistive ferrite into the highly insulating polymer matrix of PST. The observed increase in the dielectric constant (permittivity) with increasing concentration ratio of ferrites is mainly due to the electron exchange between Fe{sup 2+}↔Fe{sup 3+}+e{sup −} which consequently results in enhancement of electric polarization as well as dielectric constant. The existence of resonances peaks in the dielectric loss tangent spectra is due to the fact when the external applied frequency becomes equal to the jumping frequency of electrons between Fe{sup 2+} and Fe{sup 3+}. The increasing behavior of the dielectric constant, dielectric loss and AC conductivity with increasing ferrite ratio in PST matrix proposes their versatile use in different technological applications especially for electromagnetic shielding. - Highlights: • Y-type hexaferrites were synthesized by the microemulsion route. • AC activation is lower than DC activation energy. • Ferrite/polymer composites thin films are formed. • The peaks become more intense with increasing concentration of ferrite. • Values of “n” confirm the hopping mechanism in all thin films.

Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

Energy Technology Data Exchange (ETDEWEB)

Abbas, Y.M., E-mail: ymabbas@live.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Mansour, S.A.; Ibrahim, M.H. [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Ali, Shehab E., E-mail: shehab_physics@yahoo.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt)

2011-11-15

Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: > The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. > The transmission electronic microscope analysis confirmed the X-ray results. > The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

Major and minor magnetostriction hysteresis loops of Co-Cu-Ni ferrite

International Nuclear Information System (INIS)

Bienkowski, Adam; Kaczkowski, Zbigniew

2000-01-01

Initial curve, major and minor magnetostriction hysteresis loops (butterfly loops) as the functions of the static magnetic field of the Co 0.004 Cu 0.12 Ni 0.866 Fe 2.01 O 4.02 ferrite were investigated. The saturation magnetostriction for the field equal to 2500 A/m was negative and equal to -11.1x10 -6 and for the field of 540 A/m (equal to 3H c ) was equal to -8.0x10 -6 . Other minor magnetostriction hysteresis loops are presented

High yttria ferritic ODS steels through powder forging

Energy Technology Data Exchange (ETDEWEB)

Kumar, Deepak [Department of Metallurgical and Materials Engineering, I.I.T-Roorkee, Uttarakhand 247667 (India); Prakash, Ujjwal, E-mail: ujwalfmt@iitr.ac.in [Department of Metallurgical and Materials Engineering, I.I.T-Roorkee, Uttarakhand 247667 (India); Dabhade, Vikram V. [Department of Metallurgical and Materials Engineering, I.I.T-Roorkee, Uttarakhand 247667 (India); Laha, K.; Sakthivel, T. [Mechanical Metallurgy Group, IGCAR, Kalpakkam, Tamilnadu 603102 (India)

2017-05-15

Oxide dispersion strengthened (ODS) steels are being developed for future nuclear reactors. ODS Fe-18%Cr-2%W-0.2%Ti steels with 0, 0.35, 0.5, 1 and 1.5% Y{sub 2}O{sub 3} (all compositions in weight%) dispersion were fabricated by mechanical alloying of elemental powders. The powders were placed in a mild steel can and forged in a stream of hydrogen gas at 1473 K. The steels were forged again to final density. The strength of ODS steel increased with yttria content. Though this was accompanied by a decrease in tensile elongation, all the steels showed significant ductility. The ductility in high yttria alloys may be attributed to improved inter-particle bonding between milled powders due to reduction of surface oxides by hydrogen. This may permit development of ODS steels with yttria contents higher than the conventional limit of 0.5%. It is suggested that powder forging is a promising route to fabricate ODS steels with high yttria contents and improved ductility. - Highlights: •ODS steels with yttria contents beyond the conventional limit of 0.5 wt% were fabricated by powder forging in a hydrogen atmosphere. •All the alloys exhibited significant ductility. •This may be attributed to improved inter-particle bonding due to reduction of surface oxides by hydrogen. •Strength in excess of 300 MPa was obtained at 973 K for 0.5%, 1% and 1.5% yttria ODS alloys. •Powder forging is a promising route to fabricate ODS steels and permits development of compositions with up to 1.5% yttria.

The significant role of the rare earth ions on the elastic and thermodynamic parameters of LiCoDy- and ZnCoCe-ferrites

International Nuclear Information System (INIS)

Bishay, Samiha T.

2006-01-01

Two types of rare earth ferrites [Li 0.6 Co 0.1 Dy x Fe 2.3-x O 4 ; 0.0= 0.5 Co 0.5 Ce y Fe 2-y O 4 ; 0.0= L ) and shear (V S ) velocities, Young's modulus (E), Debye temperature (θ D ) and specific heat capacity (C v ) have been evaluated for all the investigated samples. The rare earth content as well as its ionic radius plays a significant role in the evaluated parameters. According to the experimental results, the two investigated types of rare earth ferrite are considered as insulator magnetic solids. It was found that for each composition there exists a characteristic temperature, down to which the resonance frequency of the investigated samples drops smoothly, but above this temperature the resonance frequency stays constant. Accordingly, these samples seem to be of importance in industrial applications especially in the field of electronics

Larnite powders and larnite/silica aerogel composites as effective agents for CO{sub 2} sequestration by carbonation

Energy Technology Data Exchange (ETDEWEB)

Santos, A., E-mail: alberto.santos@uca.es [Departamento de Ciencias de la Tierra, Universidad de Cadiz, Puerto Real, 11510 Cadiz (Spain); Ajbary, M.; Morales-Florez, V. [Departamento de Fisica de la Materia Condensada, Universidad de Cadiz, Puerto Real, 11510 Cadiz (Spain); Kherbeche, A. [Universite Sidi Mohamed Ben Abdellah, Ecole Superieure de Technologie, Fes (Morocco); Pinero, M. [Departamento de Fisica Aplicada, Universidad de Cadiz, Puerto Real, 11510 Cadiz (Spain); Esquivias, L. [Departamento de Fisica de la Materia Condensada, Facultad de Fisica, Instituto de Ciencias de Materiales de Sevilla (CSIC), Universidad de Sevilla, 41012 Sevilla (Spain)

2009-09-15

This paper presents the results of the carbonation reaction of two sample types: larnite (Ca{sub 2}SiO{sub 4}) powders and larnite/silica aerogel composites, the larnite acting as an active phase in a process of direct mineral carbonation. First, larnite powders were synthesized by the reaction of colloidal silica and calcium nitrate in the presence of ethylene glycol. Then, to synthesize the composites, the surface of the larnite powders was chemically modified with 3-aminopropyltriethoxysilane (APTES), and later this mixture was added to a silica sol previously prepared from tetraethylorthosilicate (TEOS). The resulting humid gel was dried in an autoclave under supercritical conditions for the ethanol. The textures and chemical compositions of the powders and composites were characterized.The carbonation reaction of both types of samples was evaluated by means of X-ray diffraction and thermogravimetric analysis. Both techniques confirm the high efficiency of the reaction at room temperature and atmospheric pressure. A complete transformation of the silicate into carbonate resulted after submitting the samples to a flow of pure CO{sub 2} for 15 min. This indicates that for this reaction time, 1 t of larnite could eliminate about 550 kg of CO{sub 2}. The grain size, porosity, and specific surface area are the factors controlling the reaction.

Evolution of frozen magnetic state in co-precipitated ZnδCo1-δFe2O4 (0 ≤ δ ≤ 1) ferrite nanopowders

Science.gov (United States)

Kubisztal, M.; Kubisztal, J.; Karolus, M.; Prusik, K.; Haneczok, G.

2018-05-01

The evolution of frozen magnetic state of ZnδCo1-δFe2O4 (0 ≤ δ ≤ 1) ferrite nanoparticles was studied by applying vibrating sample magnetometer measurements in temperature range 5-350 K and magnetic fields up to 7 T. It was shown that gradual conversion from the inverse spinel (δ = 0) to the normal one (δ = 1.0) is correlated with a drop of freezing temperature Tf (corresponding to blocking of mean magnetic moment of the system) from 238 K (δ = 0) to 9 K (δ = 1.0) and with a decrease of magnetic anisotropy constant K1 from about 8 · 105 J/m3 to about 3 · 105 J/m3. The percolation threshold predicted for bulk ferrites at 1 - δ ≈ 0.33 was observed as a significant weakness of ferrimagnetic coupling. In this case magnetization curves, determined according to the zero field cooling protocol, reveal two distinct maxima indicating that the system splits into two assemblies with specific ions distribution between A and B sites.

Resistance to pitting corrosion in ferritic and austenitic/ferritic steels

International Nuclear Information System (INIS)

De Bouvier, O.

1995-01-01

Stainless steel tubes carrying raw water are potentially vulnerable to pitting corrosion. With a view to minimizing the corrosion risk in the river-water-cooled condensers at PWR power plant, a study was conducted to determine initiation conditions and incubation durations for pitting corrosion in stagnant water. As a result, condenser tubes in Z2 CI 18 (439) or Z2 CT 18-10 (304L) steels were phased out in favour of Z2 CND 16-32 (316L) stainless steel. The same question can be yield for other applications and especially for all types of exchangers for use in electrical applications. This study sought to assess alternative methods for estimating pitting corrosion, and to check the results of these methods against the actual behaviour of studied steels. The study covered ferritic steels (439, 444, 290Mo), austenitic steel (316L) and austenitic/ferritic steels (Uranus 35N, 45N, 47N, 52N). Two approaches were adopted: laboratory tests to compare pitting corrosion risks on different materials, and tests for characterizing the behaviour of steels exposed to river water. The study begins with a laboratory tests that yield an arbitrary parameter for quantifying pitting corrosion resistance. One method involves measuring the pitting temperature in an aggressive ferric chloride solution. Other methods measure the pitting potential, either statistically (Multipit method) or deterministically (polarization curve). We then go on to discuss tests under simulated life-like conditions, involving repeated immersions in water from the Seine. (author). 9 refs., 13 figs, 9 tabs

Materials Synthesis Of Barium Hexa ferrite Used Local Natural Resources

International Nuclear Information System (INIS)

Ridwan; Sulungbudi, Grace Tj.; Mujamilah

2003-01-01

The magnetic materials of barium hexa ferrites, Ba O.6Fe 2 O 3 successfully synthesized by powder metallurgy method used local natural resources from materials waste of steel fabrication (HSM, CRM), waste of polymer fabrication (LK) as well as iron sands (PBA). These waste as well as iron sands were the main resources of iron oxide, Fe 2 O 3 . The barium oxide used in this experiments are from BaCO 3 product of Merck, and BaCO 4 which is commercially available in the market as barite. Phase identification by x-ray diffraction technique show the synthesized magnetic materials are agreed with the available commercial product, (SUMI). The energy product maximum (BH) max measured by vibrating sample magnetometer (VSM) for the samples used HSM-, CRM- and BaCO 3 as basic materials are 1.141 MGOe and 1.136 MGOe while SUMI is 1.142 MGOe. However for the samples made from LK-, PBA- used of BaCO 3 or CRM- with barite, the energy product maximum (BH) max are relatively lower than commercial product

Optimization of LiCoO2 powder extraction process from cathodes of lithium-ion batteries by chemical dissolution

OpenAIRE

Lucas Evangelista Sita; Stephany Pires da Silva; Paulo Rogério Catarini da Silva; Alexandre Urbano; Jair Scarminio

2015-01-01

A chemical process has been applied to extract LiCoO2 powder from cathodes of spent lithium-ion batteries by dissolution of the binder that agglutinate the powder particle each other as well to the Al collector surface. As solvents dimethylformamide (DMF) and N-methyilpirrolidone (NMP) were employed and the variables, cathode area, solution temperature, ultrasound bath power and solution stirring were chosen to optimize the extraction process. NMP solutions presented best results for powder e...

THE METALLICITY DEPENDENCE OF THE CO {yields} H{sub 2} CONVERSION FACTOR IN z {>=} 1 STAR-FORMING GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Genzel, R.; Tacconi, L. J.; Schreiber, N. M. Foerster; Gracia-Carpio, J.; Lutz, D.; Saintonge, A. [Max-Planck-Institut fuer extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching (Germany); Combes, F. [Observatoire de Paris, LERMA, CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Bolatto, A. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Neri, R.; Cox, P. [IRAM, 300 Rue de la Piscine, 38406 St. Martin d' Heres, Grenoble (France); Sternberg, A. [Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Cooper, M. C. [Department of Physics and Astronomy, Frederick Reines Hall, University of California, Irvine, CA 92697-4575 (United States); Bouche, N. [Department of Physics, University of California, Santa Barbara, Broida Hall, Santa Barbara, CA 93106 (United States); Bournaud, F. [Service d' Astrophysique, DAPNIA, CEA/Saclay, F-91191 Gif-sur-Yvette Cedex (France); Burkert, A. [Universitaetssternwarte der Ludwig-Maximiliansuniversitaet, Scheinerstr. 1, D-81679 Muenchen (Germany); Comerford, J. [Department of Astronomy and McDonald Observatory, 1 University Station, C1402 Austin, TX 78712-0259 (United States); Davis, M.; Newman, S. [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Garcia-Burillo, S. [Observatorio Astronomico Nacional-OAN, Apartado 1143, 28800 Alcala de Henares- Madrid (Spain); Naab, T., E-mail: genzel@mpe.mpg.de, E-mail: linda@mpe.mpg.de [Max-Planck Institut fuer Astrophysik (MPA), Karl Schwarzschildstrasse 1, D-85748 Garching (Germany); and others

2012-02-10

We use the first systematic samples of CO millimeter emission in z {>=} 1 'main-sequence' star-forming galaxies to study the metallicity dependence of the conversion factor {alpha}{sub CO,} from CO line luminosity to molecular gas mass. The molecular gas depletion rate inferred from the ratio of the star formation rate (SFR) to CO luminosity, is {approx}1 Gyr{sup -1} for near-solar metallicity galaxies with stellar masses above M{sub S} {approx} 10{sup 11} M{sub Sun }. In this regime, the depletion rate does not vary more than a factor of two to three as a function of molecular gas surface density or redshift between z {approx} 0 and 2. Below M{sub S} the depletion rate increases rapidly with decreasing metallicity. We argue that this trend is not caused by starburst events, by changes in the physical parameters of the molecular clouds, or by the impact of the fundamental-metallicity-SFR-stellar mass relation. A more probable explanation is that the conversion factor is metallicity dependent and that star formation can occur in 'CO-dark' gas. The trend is also expected theoretically from the effect of enhanced photodissociation of CO by ultraviolet radiation at low metallicity. From the available z {approx} 0 and z {approx} 1-3 samples we constrain the slope of the log({alpha}{sub CO})-log (metallicity) relation to range between -1 and -2, fairly insensitive to the assumed slope of the gas-SFR relation. Because of the lower metallicities near the peak of the galaxy formation activity at z {approx} 1-2 compared to z {approx} 0, we suggest that molecular gas masses estimated from CO luminosities have to be substantially corrected upward for galaxies below M{sub S}.

Synthesis of nano-crystalline NiFe2O4 powders in subcritical and supercritical ethanol

Czech Academy of Sciences Publication Activity Database

Ćosović, A.; Žák, Tomáš; Glisić, S.; Sokić, M.; Lazarević, S.; Ćosović, V.; Orlović, A.

2016-01-01

Roč. 113, JUL (2016), s. 96-105 ISSN 0896-8446 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : supercritical * subcritical * nano-crystalline powders * nickel ferrite * metal oxide * magnetic properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.991, year: 2016

The comparative study of the structural and the electrical properties of the nano spinel ferrites prepared by the soft mehanochemical synthesis

Directory of Open Access Journals (Sweden)

Sekulić D.L.

2014-01-01

Full Text Available Nano spinel ferrites MFe2O4 (M=Ni, Mn, Zn were obtained by soft mechanochemical synthesis in a planetary ball mill. The appropriate mixture of oxide and hydroxide powders was used as initial compounds. All of this mixture of powders was mechanically activated, uniaxial pressed and sintered at 1100°C/2h. The phase composition of the powders and sintered samples were analyzed by XRD and Raman spectroscopy. Morphologies were examined by SEM. In this study, the AC-conductivity and DC-resistivity of sintered samples of MFe2O4 (M= Ni, Mn, Zn ferrites were measured at different frequencies and at room temperature. The values of the electrical conductivities show an increase with increasing temperature, which indicated the semiconducting behavior of the studied ferrites. The conduction phenomenon of the investigated samples could be explained on the basis of hopping model. The complex impedance spectroscopy analysis was used to study the effect of grain and grain boundary on the electrical properties of all three obtained ferrites [Projekat Ministarstva nauke Republike Srbije, br. III 45003

Synthesis and magnetic characterization of nickel ferrite nanoparticles prepared by co-precipitation route

Science.gov (United States)

Maaz, K.; Karim, S.; Mumtaz, A.; Hasanain, S. K.; Liu, J.; Duan, J. L.

2009-06-01

Magnetic nanoparticles of nickel ferrite (NiFe 2O 4) have been synthesized by co-precipitation route using stable ferric and nickel salts with sodium hydroxide as the precipitating agent and oleic acid as the surfactant. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses confirmed the formation of single-phase nickel ferrite nanoparticles in the range 8-28 nm depending upon the annealing temperature of the samples during the synthesis. The size of the particles ( d) was observed to be increasing linearly with annealing temperature of the sample while the coercivity with particle size goes through a maximum, peaking at ˜11 nm and then decreases for larger particles. Typical blocking effects were observed below ˜225 K for all the prepared samples. The superparamagnetic blocking temperature ( T B) was found to be increasing with increasing particle size that has been attributed to the increased effective anisotropy energy of the nanoparticles. The saturation moment of all the samples was found much below the bulk value of nickel ferrite that has been attributed to the disordered surface spins or dead/inert layer in these nanoparticles.

Synthesis and magnetic properties of bacterial cellulose—ferrite (MFe2O4, M  =  Mn, Co, Ni, Cu) nanocomposites prepared by co-precipitation method

Science.gov (United States)

Sriplai, Nipaporn; Mongkolthanaruk, Wiyada; Pinitsoontorn, Supree

2017-09-01

The magnetic nanocomposites based on bacterial cellulose (BC) matrix and ferrite (MFe2O4, M  =  Mn, Co, Ni and Cu) nanoparticles (NPs) were fabricated. The never-dried and freeze-dried BC nanofibrils were used as templates and a co-precipitation method was applied for NPs synthesis. The nanocomposites were either freeze-dried or annealed before subjected to characterization. The x-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy showed that only MnFe2O4 and CoFe2O4 NPs could be successfully incorporated in the BC nanostructures. The results also indicated that the BC template should be freeze-dried prior to the co-precipitation process. The magnetic measurement by a vibrating sample magnetometer (VSM) showed that the strongest ferromagnetic signal was found for BC-CoFe2O4 nanocomposites. The morphological investigation by a scanning electron microscope (SEM) showed the largest volume fraction of NPs in the BC-CoFe2O4 sample which was complimentary to the magnetic property measurement. Annealing resulted in the collapse of the opened nanostructure of the BC composites. Invited talk at 5th Thailand International Nanotechnology Conference (Nano Thailand-2016), 27-29 November 2016, Nakhon Ratchasima, Thailand.

Enhancement of electrical conductivity in gamma irradiated cobalt ferrite nanoparticles

International Nuclear Information System (INIS)

Nawpute, Asha A.; Raut, A.V.; Babrekar, M.K.; Kale, C.M.; Jadhav, K.M.; Shinde, A.B.

2014-01-01

The cobalt ferrite nanoparticles were synthesized by sol-gel auto- combustion method, in which L-ascorbic acid was used as a fuel. The effect of gamma irradiation on the electrical resistivity of cobalt ferrite nanoparticles has been studied. The ferrite powder annealed at 550℃ was irradiated by gamma source 137 Cs. The synthesized nanoparticles were characterized by X-ray diffraction and DC resistivity. (author)

Effect of preparation conditions on Nickel Zinc Ferrite nanoparticles: A comparison between sol–gel auto combustion and co-precipitation methods

Directory of Open Access Journals (Sweden)

Manju Kurian

2016-09-01

Full Text Available The experimental conditions used in the preparation of nano crystalline mixed ferrite materials play an important role in the particle size of the product. In the present work a comparison is made on sol–gel auto combustion methods and co-precipitation methods by preparing Nickel Zinc Ferrite (Ni0.5Zn0.5Fe2O4 nano particles. The prepared ferrite samples were calcined at different temperatures and characterized by using standard methods. X-ray diffraction analysis indicated the formation of single phase ferrite nanoparticles for samples calcined at 500 °C. The lattice parameter range of 8.32–8.49 Å confirmed the cubic spinel structure. Average crystallite size estimated from X-ray diffractogram was found to be between 17 and 40 nm. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm−1 and the low frequency band ν2 around 400 cm−1 arising from tetrahedral (A and octahedral (B interstitial sites in the spinel lattice. TEM pictures showed particles in the nanometric range confirming the XRD data. The studies revealed that the sol–gel auto combustion method was superior to the co-precipitation method for producing single phase nano particles with smaller crystallite size.

Effect of sintering temperature on magnetization and Mössbauer parameters of cobalt ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Chandra, Grish, E-mail: grishphysics@gmail.com [Department of Physics, DSB Campus Kumaun University, Nainital 263002, Uttarakhand (India); Srivastava, R.C. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India); Reddy, V.R. [UGC-DAE CSR, Khandwa Road, DAVV Campus, Indore 452017, Madhya Pradesh (India); Agrawal, H.M. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India)

2017-04-01

Nanoparticles of cobalt ferrite of different particle size were prepared using sol-gel method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy techniques were employed for characterization of nanoparticles for structural and magnetic properties. The particle size and saturation magnetization increase with the increase of sintering temperature. The saturation magnetization increases from 53 to 85 emu/g as the sintering temperature increases from 300 to 900 °C. The remanence increases while the coercivity decreases slightly with the increase of sintering temperature. Mössbauer spectra show the ferrimagnetic nature of all the samples and the cation distribution strictly depends on the sintering temperature. The stoichiometry of the cobalt ferrite formed was estimated to be (Co{sup 2+}{sub x}Fe{sup 3+}{sub 1−x})[Co{sup 2+}{sub 1−x}Fe{sup 3+}{sub 1+x}]O{sub 4}, based on our Mössbauer analysis. The inverse spinel structure gradually transforms towards the normal spinel structure as the sintering temperature increases. - Highlights: • After 500 °C sintering the cobalt ferrite shows complete crystallization. • An inversion sintering temperature between 900 °C and 1200 °C is proposed where the Fe{sup +3} again starts migration from B site to A site. • Sintering temperature is one of the prime factors which effect the magnetization and cation distribution between two sites A and B.

Solubility of nickel ferrite (NiFe2O4) from 100 to 200 deg. C

International Nuclear Information System (INIS)

Bellefleur, Alexandre; Bachet, Martin; Benezeth, Pascale; Schott, Jacques

2012-09-01

The solubility of nickel ferrite was measured in a Hydrogen-Electrode Concentration Cell (HECC) at temperatures of 100 deg. C, 150 deg. C and 200 deg. C and pH between 4 and 5.25. The experimental solution was composed of HCl and NaCl (0.1 mol.L -1 ). Based on other studies ([1,2]), pure nickel ferrite was experimentally synthesized by calcination of a mixture of hematite Fe 2 O 3 and bunsenite NiO in molten salts at 1000 deg. C for 15 hours in air. The so obtained powder was fully characterized. The Hydrogen-Electrode Concentration cell has been described in [3]. It allowed us to run solubility experiments up to 250 deg. C with an in-situ pH measurement. To avoid reduction of the solid phase to metallic nickel, a hydrogen/argon mixture was used instead of pure hydrogen. Consequently, the equilibration time for the electrodes was longer than with pure hydrogen. Eight samples were taken on a 70 days period. After the experiments, the powder showed no significant XRD evidence of Ni (II) reduction. Nickel concentration was measured by atomic absorption spectroscopy and iron concentration was measured by UV spectroscopy. The protocol has been designed to be able to measure both dissolved Fe (II) and total iron. The nickel solubility of nickel ferrite was slightly lower than the solubility of nickel oxide in close experimental conditions [3]. Dissolved iron was mainly ferrous and the solution was under-saturated relative to both hematite and magnetite. The nickel/iron ratio indicated a non-stoichiometric dissolution. The solubility measurements were compared with equilibrium calculations using the MULTEQ database. [1] Hayashi et al (1980) J. Materials Sci. 15, 1491-1497. [2] Ziemniak et al (2007) J. Physics and Chem. of Solids. 68,10-21. [3] EPRI Report 1003155 (2002). (authors)

Characteristics of LiMO2 (M = Co, Ni, Ni0.2Co0.8, Ni0.8Co0.2) powders prepared from solution of their acetates

International Nuclear Information System (INIS)

Arof, A.K.

2008-01-01

Stoichiometric quantities of the acetates of lithium, cobalt and nickel were dissolved in distilled water and stirred with a magnetic stirrer. After complete dissolution was obtained, the solutions were heated at 120 deg. C under continuous stirring until some dark colored powder materials were formed. These precursor materials were divided into three batches and heated at 250 deg. C (for 24 h), 370 deg. C (for 24 h) and 800 deg. C for 10 h. The precursor and calcined samples were X-rayed. The X-ray diffractograms for the prepared samples were compared to that of commercialized samples and those published in the literature. The Bragg peak with Miller indices (0 0 3) in the diffractogram of the LiNi 0.8 Co 0.2 O 2 prepared sample showed a lower intensity compared to the (1 0 4) peak. The ratio of the (0 0 3) to (1 0 4) peaks for the LiNi 0.2 Co 0.8 O 2 sample is 1.56. Lattice parameters showed that the LiCoO 2 and LiNi 0.2 Co 0.8 O 2 samples produced by the method in the present investigation have potential to exhibit good electrochemical performance when used as electrodes in lithium ion batteries

TEM examination of microstructural evolution during processing of 14CrYWTi nanostructured ferritic alloys

International Nuclear Information System (INIS)

Kishimoto, H.; Alinger, M.J.; Odette, G.R.; Yamamoto, T.

2004-01-01

A transmission electron microscopy (TEM) study was carried out on the co-evolution of the coarser-scale microstructural features in mechanically alloyed (MA) powders and hot isostatic press (HIP) consolidated Fe-14Cr-3W-0 and 0.4Ti-0.25Y 2 O 3 nanostructured ferritic alloys (NFAs). The pancake shaped nanoscale grains in the as-MA powders are textured and elongated parallel to the particle surface. Powder annealing results in re-crystallization at 850 deg. C and grain growth at 1150 deg. C. The grains also recrystallize and may grow in the alloys HIPed at 850 deg. C, but appear to retain a polygonized sub-grain structure. The grains are larger and more distinct in the alloys HIPed at 1000 and 1150 deg. C. However, annealing resulted in bi-modal grain size distribution. Finer grains retained a significant dislocation density and populations of small precipitates with crystal structures distinct form the matrix. The grains and precipitates were much larger in alloys without Ti

Magnetic and structural studies of trivalent Co-substituted Cd-Mn ferrites

Science.gov (United States)

Amer, M. A.; Meaz, T. M.; El-Kestawy, M.; Ghoneim, A. I.

2016-05-01

Series of polycrystalline Cd0.4Mn0.6CoxFe2-xO4 ferrites, 0≤x≤1, were prepared by solid state reaction method. The samples were characterized by inductive coupling plasma, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectra and vibrating sample magnetometry. This study proved that all samples have single-phase cubic spinel structure. The true lattice constant, saturation magnetization, magnetic moment and trend of grain size and IR band νA showed decrease against x, whereas the trend of crystallite size, threshold frequency, Debye temperature, IR bands ν1 and ν2 and force constants F1 and F2, coercivity, anisotropy constant and residual magnetization showed increase. The IR analysis proved existence of Fe2+, Co2+, Fe4+, Co4+ and/or Mn4+ ions amongst the crystal sublattices. The characteristic bands ν1 and ν2 and force constants F1 and F2 showed decrease versus the tetrahedral- and octahedral-site bond length, respectively. The strain, specific surface area, refractive index, velocity, jump rate and remnant magnetization proved dependence on Co3+ ion content x.

Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

International Nuclear Information System (INIS)

Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab E.

2011-01-01

Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: → The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. → The transmission electronic microscope analysis confirmed the X-ray results. → The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

Study of the first stages of oxidation of a ferritic-martensitic steel Fe-12Cr in CO2

International Nuclear Information System (INIS)

Bouhieda, S.

2012-01-01

In the framework of the development of Sodium Fast Reactors in France, supercritical carbon dioxide integrated in the Brayton cycle is proposed as new cycle energy conversion system to replace current steam generators. Ferritic-Martensitic steels with 9-12 wt% Cr are good candidates for heat exchanger application because they have good mechanical properties up to a temperature of 600 C, a high thermal conductivity, a low coefficient of thermal expansion and a lower cost than that of austenitic steels. However, it has been found that these steels present a high parabolic oxide growth rate and a strong carburization in the temperature and pressure conditions of the SC-CO 2 cycle (550 C, 250 bar). This study aims to investigate the influence of different parameters (impurities present in CO 2 , thermal ramp rate and surface state) on the oxidation mechanism of a Fe-12 Cr steel in CO 2 at 550 C. It has been shown that depending on these parameters, a thin protective oxide scale without any strong carburization can be obtained. A model is proposed to explain the experimental results. (author) [fr

Exchange coupling behavior in bimagnetic CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Leite, G.C.P. [Instituto de Fisica, Universidade Federal de Mato Grosso, 78060-900 Cuiaba-MT (Brazil); Chagas, E.F., E-mail: efchagas@fisica.ufmt.br [Instituto de Fisica, Universidade Federal de Mato Grosso, 78060-900 Cuiaba-MT (Brazil); Pereira, R.; Prado, R.J. [Instituto de Fisica, Universidade Federal de Mato Grosso, 78060-900 Cuiaba-MT (Brazil); Terezo, A.J. [Departamento de Quimica, Universidade Federal do Mato Grosso, 78060-900 Cuiaba-MT (Brazil); Alzamora, M.; Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Fisicas, Rua Xavier Sigaud 150 Urca, Rio de Janeiro (Brazil)

2012-09-15

In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe{sub 2}O{sub 4} and ferrimagnetic oxide/ferromagnetic metal CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanocomposite. The latter compound is a good system to study hard ferrimagnet/soft ferromagnet exchange coupled. Two steps were followed to synthesize the bimagnetic CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanocomposite: (i) first, preparation of CoFe{sub 2}O{sub 4} nanoparticles using a simple hydrothermal method, and (ii) second, reduction reaction of cobalt ferrite nanoparticles using activated charcoal in inert atmosphere and high temperature. The phase structures, particle sizes, morphology, and magnetic properties of CoFe{sub 2}O{sub 4} nanoparticles were investigated by X-Ray diffraction (XRD), Mossbauer spectroscopy (MS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) with applied field up to 3.0 kOe at room temperature and 50 K. The mean diameter of CoFe{sub 2}O{sub 4} particles is about 16 nm. Mossbauer spectra revealed two sites for Fe{sup 3+}. One site is related to Fe in an octahedral coordination and the other one to the Fe{sup 3+} in a tetrahedral coordination, as expected for a spinel crystal structure of CoFe{sub 2}O{sub 4}. TEM measurements of nanocomposite showed the formation of a thin shell of CoFe{sub 2} on the cobalt ferrite and indicate that the nanoparticles increase to about 100 nm. The magnetization of the nanocomposite showed a hysteresis loop that is characteristic of exchange coupled systems. A maximum energy product (BH){sub max} of 1.22 MGOe was achieved at room temperature for CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanocomposites, which is about 115% higher than the value obtained for CoFe{sub 2}O{sub 4} precursor. The exchange coupling interaction and the enhancement of product (BH){sub max} in nanocomposite CoFe{sub 2}O{sub 4}/CoFe{sub 2} are discussed. - Highlights: Black-Right-Pointing-Pointer CoFe{sub 2}O{sub 4}/CoFe{sub 2} nanocomposite

Nano ZrO{sub 2} particles in nanocrystalline Fe–14Cr–1.5Zr alloy powders

Energy Technology Data Exchange (ETDEWEB)

Xu, W.Z.; Li, L.L.; Saber, M.; Koch, C.C.; Zhu, Y.T., E-mail: ytzhu@ncsu.edu; Scattergood, R.O.

2014-09-15

Here we report on the formation of nano ZrO{sub 2} particles in Fe–14Cr–1.5Zr alloy powders synthesized by mechanical alloying. The nano ZrO{sub 2} particles were found uniformly dispersed in the ferritic matrix powders with an average size of about 3.7 nm, which rendered the alloy powders so stable that it retained nanocrystalline structure after annealing at 900 °C for 1 h. The ZrO{sub 2} nanoparticles have a tetragonal crystal structure and the following orientation relationship with the matrix: (0 0 2){sub ZrO2}//(0 0 2){sub Matrix} and [0 1 0]{sub ZrO2}//[1 2 0]{sub Matrix}. The size and dispersion of the ZrO{sub 2} particles are comparable to those of Y–Ti–O enriched oxides reported in irradiation-resistant ODS alloys. This suggests a potential application of the new alloy powders for nuclear energy applications.

Structural, morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles

Directory of Open Access Journals (Sweden)

S. Anand

2017-12-01

Full Text Available In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural, morphological and dielectric properties are reported. Zirconium substituted cobalt ferrite Co1-xZrxFe2O4 (x = 0.7 nanoparticles were synthesized by sol-gel route. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope (HRSEM analysis are reported. Scherrer plot, Williamson–Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The atoms vibration modes of as synthesized nanoparticles were recorded using Fourier transform infrared (FTIR spectrometer in the range of 4000–400 cm-1. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out. Relative dielectric permittivity, loss tangent and AC conductivity were measured in the frequency range 50 Hz to 5 MHz at temperatures between 323 K and 473 K. The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal.

Improved flux-pinning properties of REBa{sub 2}Cu{sub 3}O{sub 7-z} films by low-level Co doping

Energy Technology Data Exchange (ETDEWEB)

Wang, Wentao; Pu, Minghua; Wang, Weiwei; Lei, Ming [Key Laboratory of Magnetic Levitation and Maglev Trains, Ministry of Education of China, Superconductivity R and D Centre (SRDC), Southwest Jiaotong University, Erhuanlu Beiyiduan 111, 610031 Chengdu (China); Cheng, Cuihua [Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wales, 2052 NSW, Sydney (Australia); Zhao, Yong [Key Laboratory of Magnetic Levitation and Maglev Trains, Ministry of Education of China, Superconductivity R and D Centre (SRDC), Southwest Jiaotong University, Erhuanlu Beiyiduan 111, 610031 Chengdu (China); Superconductivity Research Group, School of Materials Science and Engineering, University of New South Wales, 2052 NSW, Sydney (Australia)

2011-09-15

Biaxially textured REBa{sub 2}Cu{sub 3-x}Co{sub x}O{sub 7-z} (RE = Gd,Y) films were prepared on (00l) LaAlO{sub 3} substrate using self-developed fluorine-free chemical solution deposition (CSD) approach. The in-field J{sub c} values are significantly improved for REBa{sub 2}Cu{sub 3-x}Co{sub x}O{sub 7-z} films through low-level Co doping. Co-doped GdBa{sub 2}Cu{sub 3}O{sub 7-z} film shows the highest J{sub c} values at higher temperatures and fields, whereas the J{sub c} values of Co-doped YBa{sub 2}Cu{sub 3}O{sub 7-z} film surpass that of other films at lower temperatures and fields. In addition, the volume pinning force densities of films with Co doping have been distinctly enhanced in the applied fields, indicating improved flux-pinning properties. The possible reasons are discussed in detail. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation of single-crystal copper ferrite nanorods and nanodisks

International Nuclear Information System (INIS)

Du Jimin; Liu Zhimin; Wu Weize; Li Zhonghao; Han Buxing; Huang Ying

2005-01-01

This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

Iron-based soft magnetic composites with Mn–Zn ferrite nanoparticles coating obtained by sol–gel method

International Nuclear Information System (INIS)

Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zhang, Qian; Zhai, Fuqiang; Logan, Philip; Volinsky, Alex A.

2012-01-01

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn–Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol–gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn–Zn ferrites. Mn–Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn–Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn–Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability. - Highlights: ► Uniformly coated Mn–Zn ferrite powder increased the operating frequency of SMCs. ► Compared with epoxy coated, the permeability of SMCs increased by 33.5% at 10 kHz. ► 400 °C is the optimum annealing temperature to attain the desired permeability.

Modified ferrite core-shell nanoparticles magneto-structural characterization

Science.gov (United States)

Klekotka, Urszula; Piotrowska, Beata; Satuła, Dariusz; Kalska-Szostko, Beata

2018-06-01

In this study, ferrite nanoparticles with core-shell structures and different chemical compositions of both the core and shell were prepared with success. Proposed nanoparticles have in the first and second series magnetite core, and the shell is composed of a mixture of ferrites with Fe3+, Fe2+ and M ions (where M = Co2+, Mn2+ or Ni2+) with a general composition of M0.5Fe2.5O4. In the third series, the composition is inverted, the core is composed of a mixture of ferrites and as a shell magnetite is placed. Morphology and structural characterization of nanoparticles were done using Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), and Infrared spectroscopy (IR). While room temperature magnetic properties were measured using Mössbauer spectroscopy (MS). It is seen from Mössbauer measurements that Co always increases hyperfine magnetic field on Fe atoms at RT, while Ni and Mn have opposite influences in comparison to pure Fe ferrite, regardless of the nanoparticles structure.

Structural, magnetic and electrical properties of Zr-substitued NiZnCo ferrite nanopowders

Energy Technology Data Exchange (ETDEWEB)

Li, Le-Zhong, E-mail: lezhongli@cuit.edu.cn; Zhong, Xiao-Xi; Wang, Rui; Tu, Xiao-Qiang

2017-08-01

Highlights: • The static magnetic properties of NiZnCoZr ferrite nanopowders have been investigated. • The dielectric constant increases with the increase of Zr substitution. • The relaxation peak of tan δ ∼ T curves is observed for x ≥ 0.10. • Electrical transport behavior is found to follow the impurity semiconductor. • The dc resistivity increases at transition temperature with Zr substitution. - Abstract: Zr-substituted NiZnCo ferrite nanopowders, Ni{sub 0.4−x}Zn{sub 0.5}Zr{sub x}Co{sub 0.1}Fe{sub 2.0}O{sub 4} (0 ≤ x ≤ 0.20), were synthesized by the sol-gel auto-combustion method. The effects of Zr substitution on the structural, magnetic and electrical properties have been investigated. The DTA and TG results indicate that there are three steps of combustion process. The X-ray diffraction patterns show that the lattice parameter and the average crystallite size increase with the increase of Zr substitution. The saturation magnetization increases with the increase of Zr substitution when x ≤ 0.05, and then decreases when x > 0.05. Meanwhile, the coercivity initially decreases with the increase of Zr substitution when x ≤ 0.05, and then increases when x > 0.05. The polarization behavior for all the samples in the test frequency range from100 Hz to10 MHz obeys the charge polarization mechanism, which happens since the frequency of the hopping of electron exchange between Fe{sup 2+} and Fe{sup 3+} ions are far from the frequency of alternating-current field. And the dielectric constant increases with the increase of Zr substitution. The relaxation peak of the frequency dependence of dielectric loss is observed for x ≥ 0.10, which is due to the frequency of charge hopping between the Fe{sup 2+} and Fe{sup 3+} exactly matches with the frequency of the external applied field. Electrical transport behavior of the ferrite nanopowders is found to follow the impurity semiconductor, and the effect of Zr substitution on the temperature dependence

Influence of Y{sup 3+} substitution on the structural and magnetic properties of Sr{sub 0.7}La{sub 0.3}Fe{sub 11.75-x}Y{sub x}Co{sub 0.25}O{sub 19} hexagonal ferrites

Energy Technology Data Exchange (ETDEWEB)

Zhang, Cong; Liu, Xiansong; Rehman, Khalid Mehmood Ur; Liu, Chaocheng; Li, Haohao; Meng, Xiangyu [Anhui University, School of Physics and Materials Science, Hefei (China); Anhui University, School of Physics and Materials Science, Engineering Technology Research Center of Magnetic Materials, Hefei (China)

2017-08-15

In this study, the Y{sup 3+} ion-substituted M-type Sr{sub 0.7}La{sub 0.3}Fe{sub 11.75-x}Y{sub x}Co{sub 0.25}O{sub 19} (0 ≤ x ≤ 0.2) hexagonal ferrites were synthesized by the traditional ceramic method. The structural, morphological, and magnetic properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer techniques. The results show that a single M-type strontium ferrite was obtained with the Yttrium content (x) from 0 to 0.08, and the impure phase appeared when x is above 0.08. SEM images indicate the hexagonal platelet-like particles, and the size of the materials is about 3-5 μm. The saturation magnetization (M{sub s}) and coercivity (H{sub c}) of the magnetic powders both increased with the increase of x from 0 to 0.12, then decreased with the increase of x from 0.16 to 0.2. (orig.)

Ceramic grade (U,Pu)O2 powder fabrication

International Nuclear Information System (INIS)

Cristallini, O.A.; Villegas de Maroto, Marina; De Pino, J.I.; Osuna, H.A.

1980-01-01

Ceramic grade UO 2 powder was obtained by the homogeneous precipitation method. This procedure was afterwards applied to the fabrication of ceramic grade (U,Pu)O 2 powders, and mixed oxide powders with Pu content ranging from 0.7 to 16% were obtained. The obtainment of mixed ceramic oxides as well as the recuperation of fabrication scraps were developed in three steps: 1)study of the process of homogeneous precipitation of ammonium diuranate (ADU); 2) co-precipitation of ADU/PuO 2 .H 2 O for Pu concentrations of 0.6 and 6.8; 3) the thermal conditioning to mixed oxide (U,Pu)O 2 powders. The experimental procedure involves the following steps: preparation of the PuO 2 (NO 3 ) 4 solution; co-precipitation of the PuO 2 (NO 3 ) 2 solution with an UO 2 (NO 3 ) 2 solution; filtration and drying of the precipitate, thermal treatment and finally, mixing, pressing and sintering of the (U,Pu)O 2 and Nukem UO 2 powder with a 0. of zinc stearate. Different controls were made by means of physical, chemical and ceramographic tests. This method can be used for the fabrication of fast reactor fuels or, previous mechanical dispersion in UO 2 powder, for the fabrication of thermal reactors fuels. (M.E.L.) [es

Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

Directory of Open Access Journals (Sweden)

Rajendra S. Gaikwad

2011-01-01

Full Text Available Cobalt ferrite, CoFe2O4, nanocrystalline films were deposited using electrostatic spray method and explored in sustainable hydrogen production application. Reflection planes in X-ray diffraction pattern confirm CoFe2O4 phase. The surface scanning microscopy photoimages reveal an agglomeration of closely-packed CoFe2O4 nanoflakes. Concentrated solar-panel, a two-step water splitting process, measurement technique was preferred for measuring the hydrogen generation rate. For about 5 hr sustainable, 440 mL/hr, hydrogen production activity was achieved, confirming the efficient use of cobalt ferrite nanocrystallites film in hydrogen production application.

[Use of powder metallurgy for development of implants of Co-Cr-Mo alloy powder].

Science.gov (United States)

Dabrowski, J R

2001-04-01

This paper discusses the application of powder metallurgy for the development of porous implantation materials. Powders obtained from Co-Cr-Mo alloy with different carbon content by water spraying and grinding, have been investigated. Cold pressing and rotary re-pressing methods were used for compressing the powder. It was found that the sintered materials obtained from water spraying have the most advantageous properties.

One-pot production of copper ferrite nanoparticles using a chemical method

Energy Technology Data Exchange (ETDEWEB)

Nishida, Naoki, E-mail: nnishida@rs.tus.ac.jp; Amagasa, Shota [Tokyo University of Science, Department of Chemistry (Japan); Kobayashi, Yoshio [The University of Electro-Communications, Department of Engineering Science (Japan); Yamada, Yasuhiro [Tokyo University of Science, Department of Chemistry (Japan)

2016-12-15

Copper ferrite nanoparticles were synthesized via the oxidation of precipitates obtained from the reaction of FeCl{sub 2}, CuSO{sub 4} and N{sub 2}H{sub 4} in the presence of gelatin. These copper ferrite particles were subsequently examined using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Mössbauer spectroscopy. The average size of the copper ferrite nanoparticles was less than 5 nm, and they exhibited superparamagnetic behavior as a result of their small size. The low temperature Mössbauer spectrum exhibited three sets of sextets, two corresponding to the tetrahedral and octahedral sites of the copper spinel structure and one with small hyperfine magnetic field corresponding to the surface or defects of the nanoparticles. When the ratio of copper salt was increased, the tetrahedral site became preferable for copper, and metallic copper and copper ferrite were both present in a single nanoparticle.

Source Header List. Volume 2. L through Z

Science.gov (United States)

1998-07-01

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Gas sensing properties of magnesium ferrite prepared by co-precipitation method

International Nuclear Information System (INIS)

Hankare, P.P.; Jadhav, S.D.; Sankpal, U.B.; Patil, R.P.; Sasikala, R.; Mulla, I.S.

2009-01-01

Polycrystalline magnesium ferrite (MgFe 2 O 4 ) was prepared by the co-precipitation method. The synthesized compound was characterized for their phase and morphology by X-ray diffraction and scanning electron microscopy, respectively. Conductance responses of the (MgFe 2 O 4 ) were measured towards gases like hydrogen sulfide (H 2 S), liquefied petroleum gas (LPG), ethanol vapors (C 2 H 5 OH), SO x , H 2 , NO x , NH 3, methanol, acetone and petrol. The gas sensing characterstics were obtained by measuring the sensitivity as a function of various controlling factors like operating temperatures and concentrations of gases. It was found that the sensor exhibited various responses towards these gases at different operating temperatures. Furthermore; the MgFe 2 O 4 based sensor exhibited a fast response and a good recovery towards petrol at temperature 250 deg. C. The results of the response towards petrol reveal that (MgFe 2 O 4 ) synthesized by a simple co-precipitation method, would be a suitable material for the fabrication of the petrol sensor.

Synthesis and hyperthermia property of hydroxyapatite-ferrite hybrid particles by ultrasonic spray pyrolysis

International Nuclear Information System (INIS)

Inukai, Akihiro; Sakamoto, Naonori; Aono, Hiromichi; Sakurai, Osamu; Shinozaki, Kazuo; Suzuki, Hisao; Wakiya, Naoki

2011-01-01

Biocompatible hybrid particles composed of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) and ferrite (γ-Fe 2 O 3 and Fe 3 O 4 ) were synthesized using a two-step procedure. First, the ferrite particles were synthesized by co-precipitation. Second, the suspension, which was composed of ferrite particles by a co-precipitation method, Ca(NO 3 ) 2 , and H 3 PO 4 aqueous solution with surfactant, was nebulized into mist ultrasonically. Then the mist was pyrolyzed at 1000 o C to synthesize HAp-ferrite hybrid particles. The molar ratio of Fe ion and HAp was (Fe 2+ and Fe 3+ )/HAp=6. The synthesized hybrid particle was round and dimpled, and the average diameter of a secondary particle was 740 nm. The cross section of the synthesized hybrid particles revealed two phases: HAp and ferrite. The ferrite was coated with HAp. The synthesized hybrid particles show a saturation magnetization of 11.8 emu/g. The net saturation magnetization of the ferrite component was calculated as 32.5 emu/g. The temperature increase in the AC-magnetic field (370 kHz, 1.77 kA/m) was 9 o C with 3.4 g (the ferrite component was 1.0 g). These results show that synthesized hybrid particles are biocompatible and might be useful for magnetic transport and hyperthermia studies. - Research Highlights: → Biocompatible hybrid particles composed of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) and ferrite (γ-Fe 2 O 3 and Fe 3 O 4 ) were synthesized using a two-step synthesis, which is comprised of co-precipitation and ultrasonic spray pyrolysis. → Cross sectional TEM observation and X-ray diffraction revealed that synthesized hybrid particles showed two phases (HAp and ferrite), and the ferrite was coated with HAp. → The saturation magnetization of ferrite in the HAp-ferrite hybrid was 32.49 emu/g. → The increased temperature in the AC-magnetic field (370 kHz, 1.77 kA/m) was 9 o C with 3.4 g (the ferrite component was 1.0 g).

Iron-based soft magnetic composites with Mn-Zn ferrite nanoparticles coating obtained by sol-gel method

Science.gov (United States)

Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zhang, Qian; Zhai, Fuqiang; Logan, Philip; Volinsky, Alex A.

2012-11-01

This paper focuses on iron-based soft magnetic composites which were synthesized by utilizing Mn-Zn ferrite nanoparticles to coat iron powder. The nanocrystalline iron powders, with an average particle diameter of 20 nm, were obtained via the sol-gel method. Scanning electron microscopy, energy dispersive X-ray spectroscopy and distribution maps show that the iron particle surface is covered with a thin layer of Mn-Zn ferrites. Mn-Zn ferrite uniformly coated the surface of the powder particles, resulting in a reduced imaginary permeability, increased electrical resistivity and a higher operating frequency of the synthesized magnets. Mn-Zn ferrite coated samples have higher permeability and lower magnetic loss when compared with the non-magnetic epoxy resin coated compacts. The real part of permeability increases by 33.5% when compared with the epoxy resin coated samples at 10 kHz. The effects of heat treatment temperature on crystalline phase formation and on the magnetic properties of the Mn-Zn ferrite were investigated via X-ray diffraction and a vibrating sample magnetometer. Ferrites decomposed to FeO and MnO after annealing above 400 °C in nitrogen; thus it is the optimum annealing temperature to attain the desired permeability.

Microemulsion synthesis and magnetic properties of hydroxyapatite-encapsulated nano CoFe{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Foroughi, Firoozeh [Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan (Iran, Islamic Republic of); Hassanzadeh-Tabrizi, S.A., E-mail: tabrizi1980@gmail.com [Young Researchers and Elite Club, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan (Iran, Islamic Republic of); Amighian, Jamshid [Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan (Iran, Islamic Republic of)

2015-05-15

Hydroxyapatite-encapsulated cobalt ferrite (CoFe{sub 2}O{sub 4}) nanopowders were synthesized by one step microemulsion method. The powders were characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. TEM results showed that nanoparticles calcined at 700 °C have core–shell morphology. It was found that the resultant phases, morphology and magnetic properties of the samples depend on calcining temperature. The synthesized nanoparticles showed a maximum saturation magnetization of 7.8 emu/g with a wasp-waisted hysteresis loop. The magnetion was reduced by increasing calcining temperature to 900 °C. This reduction is due to the reaction of cobalt ferrite with hydroxyapatite which leads to CaFe{sub 12}(PO{sub 4}){sub 8}(OH){sub 12} phase. - Highlights: • Hydroxyapatite-encapsulated cobalt ferrite nanopowders were synthesized by a microemulsion method. • The characterization of nanoparticles was performed using various analytical tools, such as TEM, FE-SEM, FTIR, XRD and VSM. • The nanoparticles showed a maximum saturation magnetization of 7.8 emu/g. • The samples indicated a wasp-waisted hysteresis loop.

High frequency permeability and permittivity spectra of BiFeO{sub 3}/(CoTi)-BaM ferrite composites

Energy Technology Data Exchange (ETDEWEB)

Peng, Yun; Wu, Xiaohan; Li, Qifan; Yu, Ting; Feng, Zekun, E-mail: fengzekun@hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Chen, Zhongyan [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Jiangmen Magsource New Material CO., LTD., 529000 Guangdong (China); Su, Zhijuan; Chen, Yajie; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, and Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115 (United States)

2015-05-07

Low magnetic loss ferrite composites consisting of Ba(CoTi){sub 1.2}Fe{sub 9.6}O{sub 19} and BiFeO{sub 3} (BFO) ferrite were investigated for permeability, permittivity, and high frequency losses at 10 MHz–1 GHz. The phase fraction of BiFeO{sub 3} was quantitatively analyzed by X-ray diffraction measurements. An effective medium approach was employed to predict the effective permeability and permittivity for the ferrite composites, which was found to be in good agreement with experimental data. The experiment demonstrated low magnetic losses (<0.128), modified by BFO phase fraction, while retaining high permeability (∼10.86) at 300 MHz. More importantly, the BFO phase resulted in a reduction of magnetic loss by 32%, as BFO phase increased from 2.7 vol. % to 12.6 vol. %. The effect of BFO phase on magnetic and dielectric properties revealed great potential for use in the miniaturization of high efficiency antennas.

The structural changes of Y2O3 in ferritic ODS alloys during milling

International Nuclear Information System (INIS)

Hilger, I.; Tegel, M.; Gorley, M.J.; Grant, P.S.; Weißgärber, T.; Kieback, B.

2014-01-01

Oxide dispersion strengthened (ODS) ferritic steels are usually fabricated via mechanical alloying and subsequent consolidation via hot extrusion or hot isostatic pressing. During the individual process steps, a complex evolution of the nanoparticle structure is taking place. Powders with different Y 2 O 3 contents were milled and examined by means of X-ray diffraction (XRD) and atom probe tomography (APT). It has been observed that the Y 2 O 3 is fragmented and becomes partially amorphous upon milling due to the grain refinement of Y 2 O 3 during the milling process. There was no compelling evidence for Y 2 O 3 dissociation and dissolution into the steel matrix

The effect of Co substitution on the structural and magnetic properties of lithium ferrite synthesized by an autocombustion method

International Nuclear Information System (INIS)

Sawant, V.S.; Rajpure, K.Y.

2015-01-01

Nanoparticles of Li 0.5−0.5x Co x Fe 2.5−0.5x O 4 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) were synthesized by the solution combustion method. The influence of Co substitution on the structural, morphological and magnetic properties of the prepared samples was studied. The XRD studies confirm the formation of single phase cubic spinel structure of the ferrite samples. Their lattice constants vary linearly from 8.31 Å (x=0) to 8.35 Å (x=0.6) with increasing Co 2+ content, due to the ionic volume differences of Co 2+ , Fe 3+ and Li 1+ ions. Also, the bond lengths and site radii of octahedral and tetrahedral sites are found to increase linearly with Co 2+ content. The crystallite sizes of all the prepared samples estimated from the full width half maximum (FWHM) of the strongest reflection of the planes (311) almost remain constant with the increase of Co 2+ content. The surface morphology of the prepared ferrite samples show that some of the particles have a cubic and the others have a spherical shape. The average particle sizes of the samples obtained from SEM micrographs show an initial increase up to the sample of x=0.3 and then it decreases slightly. The magnetic properties of the samples have been studied by measuring M–H plots. Moreover, the saturation magnetization, remnant magnetization, and coercivity of the prepared samples increase up to the sample of x=0.3 (140.1 emu/g, 49.4 emu/g and 714.05 Oe, respectively) and then they decrease again. The variation in the experimental magnetic moment μ B exp with Co 2+ content is explained on the basis of Neel's two sub-lattice model. Furthermore, the initial permeability of the prepared samples increases with increasing Co 2+ content up to the sample of x=0.3 and then a slight decrease is observed again. - Highlights: • Co substituted Li ferrite samples were prepared by the solution combustion method. • Co 2+ content, x was varied as x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6. • Effect of Co 2

Structural and magnetic properties of Ni{sub 0.15}Mg{sub 0.1}Cu{sub 0.3}Zn{sub 0.45}Fe{sub 2}O{sub 4} ferrite prepared by NaOH-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Hou, Wei-xiao; Wang, Zhi, E-mail: zhiwang@tju.edu.cn

2015-09-15

Highlights: • NiMgCuZn ferrites were successfully prepared by low-temperature sintering. • NiMgCuZn ferrites have the advantages of both NiCuZn and MgCuZn ferrites. • NiMgCuZn ferrites exhibit high Curie temperature & high stability of permeability. - Abstract: The Ni{sub 0.15}Mg{sub 0.1}Cu{sub 0.3}Zn{sub 0.45}Fe{sub 2}O{sub 4} ferrite powders have been prepared by NaOH co-precipitation method and characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The XRD patterns confirm the single phase spinel structure of synthesized nanoparticles. The average crystallite size of the particles increases from 12 to 36 nm with calcining temperature (T{sub a}) from 500 to 800 °C. The saturation magnetization (M{sub s}) of the superparamagnetic particles was deduced by Langevin theory. Subsequently, the densification characteristics and magnetic properties of the low-temperature 950 °C-sintered ferrite bulk samples were also investigated. The magnetic measurement showed that the sintered bulk sample of T{sub a} = 600 °C has the highest initial permeability (μ{sub i}), lowest coercivity (H{sub c}), largest saturation magnetization (M{sub s}) and satisfactory thermal stability of μ{sub i}. The microstructures of sintered samples were examined using field emission scanning electric microscope (FESEM). The T{sub a} has significant influence on the bulk density, initial permeability, saturation magnetization and coercivity of Ni{sub 0.15}Mg{sub 0.1}Cu{sub 0.3}Zn{sub 0.45}Fe{sub 2}O{sub 4} ferrite.

Synthesis, structure and electromagnetic properties of Mn-Zn ferrite by sol-gel combustion technique

Science.gov (United States)

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2014-01-01

The electromagnetic absorbing behaviors of a thin coating fabricated by mixing Mn-Zn ferrite with epoxy resin (EP) were studied. The spinel ferrites Mn1-xZnxFe2O4 (x=0.2, 0.5 and 0.8) were synthesized with citrate acid as complex agent by sol-gel combustion method. The microstructure and surface morphology of Mn-Zn ferrite powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permittivity and complex permeability of the fabricated ferrite/EP composites were investigated in terms of their contributions to the absorbing properties in the low frequency (10 MHz to 1 GHz). The microwave absorption of the prepared ferrite/EP composites could be tailored by matching the dielectric loss and magnetic loss and by controlling the doped metal ratio. The composites with the ferrite composition x=0.2 are found to show higher reflection loss compared with the composites with other compositions. It is proposed that the prepared composites can potentially be applied in electromagnetic microwave absorbing field.

Spin canting phenomenon in cadmium doped cobalt ferrites ...

Indian Academy of Sciences (India)

2016-08-26

Aug 26, 2016 ... Abstract. Synthesis of non-collinear (spin canted) ferrites having the formula, CoCdFe2−O4 ( = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), has been carried out using the sol–gel auto combustion method. The ferrite samples show an interesting magnetic transition from Neel to Yafet–Kittel configuration, as the Cd2+ ...

Modified solvothermal synthesis of cobalt ferrite (CoFe2O4) magnetic nanoparticles photocatalysts for degradation of methylene blue with H2O2/visible light

Science.gov (United States)

Kalam, Abul; Al-Sehemi, Abdullah G.; Assiri, Mohammed; Du, Gaohui; Ahmad, Tokeer; Ahmad, Irfan; Pannipara, M.

2018-03-01

Different grads of magnetic nano-scaled cobalt ferrites (CoFe2O4) photocatalysts were synthesized by modified Solvothermal (MST) process with and without polysaccharide. The indigenously synthesized photocatalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermo gravimetric analysis (TGA), Fourier transform infrared (FT-IR), UV-visible (UV-vis) spectroscopy and N2 adsorption-desorption isotherm method. The Fourier transform infrared spectroscopy study showed the Fe-O stretching vibration 590-619 cm-1, confirming the formation of metal oxide. The crystallite size of the synthesized photocatalysts was found in the range between 20.0 and 30.0 nm. The surface area of obtained magnetic nanoparticles is found to be reasonably high in the range of 63.0-76.0 m2/g. The results shown that only MST-2 is the most active catalyst for photo-Fenton like scheme for fast photodegradation action of methylene blue dye, this is possible due to optical band gap estimated of 2.65 eV. Captivatingly the percentage of degradation efficiency increases up to 80% after 140 min by using MST-2 photocatalyst. Photocatalytic degradation of methylene blue (MB) dye under visible light irradiation with cobalt ferrite magnetic nanoparticles followed first order kinetic constant and rate constant of MST-2 is almost 2.0 times greater than MST-1 photocatalyst.

Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

International Nuclear Information System (INIS)

Oksiuta, Z.; Baluc, N.

2009-01-01

Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-14Cr-2W-0.3Ti-0.3Y 2 O 3 (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y 2 O 3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests.

Irregular distribution of metal ions in ferrites prepared by co-precipitation technique structure analysis of Mn-Zn ferrite using extended X-ray absorption fine structure

International Nuclear Information System (INIS)

Jeyadevan, B.; Tohji, K.; Nakatsuka, K.; Narayanasamy, A.

2000-01-01

The tetrahedral/octahedral site occupancy of non-magnetic zinc ion, added to maximize the net magnetic moment of mixed ferrites has been found to depend on the method of preparation. In this paper, we qualitatively analyze the metal ion distribution in Mn-Zn ferrite particles prepared by co-precipitation and ceramic methods using extended X-ray absorption fine structure (EXAFS) technique. The results suggest that the differences observed in the magnetic properties of the samples prepared by different methods are not only due to the difference in particle size but also due to the difference in cation distribution. The difference in cation distributions between ferrites of similar composition prepared differently has been found to depend on the crystal field stability energies of the metal ion of interest and associated cations

Influence of Powder Outgassing Conditions on the Chemical, Microstructural, and Mechanical Properties of a 14 wt% Cr Ferritic ODS Steel

Science.gov (United States)

Sornin, D.; Giroux, P.-F.; Rigal, E.; Fabregue, D.; Soulas, R.; Hamon, D.

2017-11-01

Oxide dispersion-strengthened ferritic stainless steels are foreseen as fuel cladding tube materials for the new generation of sodium fast nuclear reactors. Those materials, which exhibit remarkable creep properties at high temperature, are reinforced by a dense precipitation of nanometric oxides. This precipitation is obtained by mechanical alloying of a powder and subsequent consolidation. Before consolidation, to obtain a fully dense material, the powder is vacuumed to outgas trapped gases and species adsorbed at the surface of the powder particles. This operation is commonly done at moderate to high temperature to evacuate as much as possible volatile species. This paper focuses on the influence of outgassing conditions on some properties of the further consolidated materials. Chemical composition and microstructural characterization of different materials obtained from various outgassing cycles are compared. Finally, impact toughness of those materials is evaluated by using Charpy testing. This study shows a significant influence of the outgassing conditions on the mechanical properties of the consolidated material. However, microstructure and oxygen contents seem poorly impacted by the various outgassing conditions.

Layer-by-Layer Self-Assembled Ferrite Multilayer Nanofilms for Microwave Absorption

Directory of Open Access Journals (Sweden)

Jiwoong Heo

2015-01-01

Full Text Available We demonstrate a simple method for fabricating multilayer thin films containing ferrite (Co0.5Zn0.5Fe2O4 nanoparticles, using layer-by-layer (LbL self-assembly. These films have microwave absorbing properties for possible radar absorbing and stealth applications. To demonstrate incorporation of inorganic ferrite nanoparticles into an electrostatic-interaction-based LbL self-assembly, we fabricated two types of films: (1 a blended three-component LbL film consisting of a sequential poly(acrylic acid/oleic acid-ferrite blend layer and a poly(allylamine hydrochloride layer and (2 a tetralayer LbL film consisting of sequential poly(diallyldimethylammonium chloride, poly(sodium-4-sulfonate, bPEI-ferrite, and poly(sodium-4-sulfonate layers. We compared surface morphologies, thicknesses, and packing density of the two types of ferrite multilayer film. Ferrite nanoparticles (Co0.5Zn0.5Fe2O4 were prepared via a coprecipitation method from an aqueous precursor solution. The structure and composition of the ferrite nanoparticles were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. X-ray diffraction patterns of ferrite nanoparticles indicated a cubic spinel structure, and energy dispersive X-ray spectroscopy revealed their composition. Thickness growth and surface morphology were measured using a profilometer, atomic force microscope, and scanning electron microscope.

Dielectric properties of Al-substituted Co ferrite nanoparticles

Indian Academy of Sciences (India)

Administrator

The particle size, D, decreases with increase in Al-content. The lattice parameter, a ... a significant saving in time and energy consumption over the traditional methods. ... electrical, and magnetic properties of spinel ferrites. Cobalt ferrite based ...

Investigation of structural, optical, magnetic and electrical properties of tungsten doped Nisbnd Zn nano-ferrites

Science.gov (United States)

Pathania, Abhilash; Bhardwaj, Sanjay; Thakur, Shyam Singh; Mattei, Jean-Luc; Queffelec, Patrick; Panina, Larissa V.; Thakur, Preeti; Thakur, Atul

2018-02-01

Tungsten substituted nickel-zinc ferrite nanoparticles with chemical composition of Ni0.5Zn0.5WxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 & 1.0) were successfully synthesized by a chemical co-precipitation method. The prepared ferrites were pre sintered at 850 °C and then annealed at 1000 °C in a muffle furnace for 3 h each. This sintered powder was inspected by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM) to study the structural, optical, and magnetic properties. XRD measurement revealed the phase purity of all the nanoferrite samples with cubic spinel structure. The estimated crystallite size by X-ray line broadening is found in the range of 49-62 nm. FTIR spectra of all the samples have observed two prominent absorption bands in the range 400-700 cm-1 arising due to tetrahedral and octahedral stretching vibrations. Vibrating sample magnetometer experiments showed that the saturation magnetizations (MS) decreased with an increase in non-magnetic tungsten ion doping. The electrical resistivity of tungsten doped Nisbnd Zn nano ferrites were examined extensively as a function of temperature. With an increase in tungsten composition, resistivity was found to decrease from 2.2 × 105 Ω cm to 1.9 × 105 Ω cm which indicates the semiconducting behavior of the ferrite samples. The activation energy also decreased from 0.0264 to 0.0221 eV at x = 0.0 to x = 1.0. These low coercive field tungsten doped Nisbnd Zn ferrites are suitable for hyperthermia and sensor applications. These observations are explained in detail on the basis of various models and theories.

Lithium ferrite: The study on magnetic and complex permittivity characteristics

Directory of Open Access Journals (Sweden)

Madhavaprasad Dasari

2017-03-01

Full Text Available Lithium ferrite (Li0.5Fe2.5O4 powder was prepared by solid state reaction method, which was finally pressed and sintered at 1150 °C. The spinel structure of the lithium ferrite was confirmed by X-ray diffraction and grain size estimation was obtained from scanning electron microscope (SEM. Fourier transform infrared spectroscopy (FTIR confirmed the presence of primary and secondary absorption bands characteristic for spinel structure. The force constants were estimated using absorption bands for the lithium ferrite. Magnetization and dielectric studies were carried out for the sintered sample. Saturation magnetization (Ms of 59.6 emu/g was achieved and variation of magnetization with temperature was used to identify the Curie temperature. The complex permittivity (ε∗ for the lithium ferrite sample was obtained for wide frequency range up to 3 GHz and discussed based on available models. The Curie temperature was estimated around 480 °C and verified from both magnetization versus temperature and dielectric constant versus temperature measurements.

A study of NiZnCu-ferrite/SiO2 nanocomposites with different ferrite contents synthesized by sol-gel method

International Nuclear Information System (INIS)

Yan Shifeng; Geng Jianxin; Chen Jianfeng; Yin Li; Zhou Yunchun; Liu Leijing; Zhou Enle

2005-01-01

Ni 0.65 Zn 0.35 Cu 0.1 Fe 1.9 O 4 /SiO 2 nanocomposites with different weight percentages of NiZnCu-ferrite dispersed in silica matrix were successfully fabricated by the sol-gel method using tetraethylorthosilicate (TEOS) as a precursor of silica, and metal nitrates as precursors of NiZnCu ferrite. The thermal decomposition process of the dried gel was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The obtained Ni 0.65 Zn 0.35 Cu 0.1 Fe 1.9 O 4 /SiO 2 nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Mossbauer spectroscopy and vibrating sample magnetometry (VSM). The formation of stoichiometric NiZnCu-ferrite dispersed in silica matrix is confirmed when the weight percentage of ferrite is not more than 30%. Samples with higher ferrite content have small amount of α-Fe 2 O 3 . The transition from the paramagnetic to the ferromagnetic state is observed as the ferrite content increases from 20 to 90wt%. The magnetic properties of the nanocomposites are closely related to the ferrite content. The saturation magnetization increases with the ferrite content, while the coercivity reaches a maximum when the ferrite is 80wt% in the silica matrix

Microstructural changes and effect of variation of lattice strain on positron annihilation lifetime parameters of zinc ferrite nanocomposites prepared by high enegy ball-milling

Directory of Open Access Journals (Sweden)

Abhijit Banerjee

2012-12-01

Full Text Available Zn-ferrite nanoparticles were synthesized at room temperature by mechanical alloying the stoichiometric (1:1 mol% mixture of ZnO and α-Fe2O3 powder under open air. Formation of both normal and inverse spinel ferrite phases was noticed after 30 minutes and 2.5 hours ball milling respectively and the content of inverse spinel phase increased with increasing milling time. The phase transformation kinetics towards formation of ferrite phases and microstructure characterization of ball milled ZnFe2O4 phases was primarily investigated by X-ray powder diffraction pattern analysis. The relative phase abundances of different phases, crystallite size, r.m.s. strain, lattice parameter change etc. were estimated from the Rietveld powder structure refinement analysis of XRD data. Positron annihilation lifetime spectra of all ball milled samples were deconvoluted with three lifetime parameters and their variation with milling time duration was explained with microstructural changes and formation of different phases with increase of milling time duration.

Influence of calcination temperature on Cd{sub 0.3}Co{sub 0.7}Fe{sub 2}O{sub 4} nanoparticles: Structural, thermal and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Reddy, Ch.Venkata, E-mail: cvrphy@gmail.com [School of Mechanical Engineering, Yeungnam University, 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do 712-749 (Korea, Republic of); PrabhakarVattikuti, S.V. [School of Mechanical Engineering, Yeungnam University, 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do 712-749 (Korea, Republic of); Ravikumar, R.V.S.S.N. [Department of Physics, Acharya Nagarjuna University, AP 522510 (India); Moon, Sang Jun, E-mail: nanobiomems@dgist.ac.kr [Cybernetics Laboratory, Daegu Gyeongbuk Institute of Science and Technology (DGIST) (Korea, Republic of); Shim, Jaesool, E-mail: jshim@ynu.ac.kr [School of Mechanical Engineering, Yeungnam University, 214-1, Dae-dong, Gyeongsan-si, Gyeongsangbuk-do 712-749 (Korea, Republic of)

2015-11-15

Cadmium substituted cobalt ferrite nanoparticles are synthesis using the chemical method. The as-prepared ferrite nanoparticles are calcinated at 300 °C and 600 °C respectively. The samples are studied using; Powder XRD, SEM with EDX, TEM, FT-IR, TG-DTA and vibrating sample magnetometer (VSM) in order to study the calcination temperature effect on structural, morphological and magnetic properties. The magnetic properties, like saturation magnetization and coercivity increases with increasing the calcination temperature. This enhancement is attributed to the transition from amulti-domain to a single-domain nature. The absorption bands observed at 588 cm{sup −1} (ν{sub 1}) and 440 cm{sup −1} (ν{sub 2}) are attributed to the vibrations of tetrahedral and octahedral complexes. The TG-DTA curves reveal the thermal stability of the prepared ferrite nanoparticles. The calcination temperature influences the magnetic properties, surface morphology and crystalline size. - Highlights: • Cd{sub 0.3}Co{sub 0.7}Fe{sub 2}O{sub 4} nanoparticles synthesized using the chemical co-precipitation. • The magnetization, coercivity values increases with increasing the calcination temperature. • The calcination temperature influences the magnetic properties and crystallite size. • The FTIR spectra results confirmed the vibrations of tetrahedral and octahedral complexes.

A new fabrication route for SFR fuel using (U, Pu)O{sub 2} powder obtained by oxalic co-conversion

Energy Technology Data Exchange (ETDEWEB)

Vaudez, Stéphane, E-mail: stephane.vaudez@cea.fr [CEA, DEN, DEC, SPUA, Cadarache, F-13108 Saint-Paul-Lez-Durance (France); Belin, Renaud C.; Aufore, Laurence; Sornay, Philippe [CEA, DEN, DEC, SPUA, Cadarache, F-13108 Saint-Paul-Lez-Durance (France); Grandjean, Stéphane [CEA, DEN, DRCP, DIR, Marcoule, F-30207 Bagnols sur Cèze (France)

2013-11-15

The standard powder metallurgy preparation of SFR (Sodium Fast Reactor) oxide fuel involves UO{sub 2} and PuO{sub 2} co-milling. An alternative route, using a solid-solution of mixed oxide obtained by oxalic co-conversion as the starting material, is presented. It was used to manufacture nuclear fuels for the “COPIX” irradiation conducted in the Phenix SFR. Two processes using co-converted powders were tested to elaborate fuel pellets: (1) the Direct Process that consists in pressing and sintering the mixed oxide with the final Pu content and (2) the Dilution Process, which involves the dilution of a high Pu content mixed oxide with UO{sub 2}. After studying the structural and microstructural evolution with temperature of these innovative raw materials, the elaboration parameters were adjusted to obtain final pellets in accordance with the Phenix fuel specifications. This study demonstrates the feasibility of such new fabrication route at laboratory scale and, from a more fundamental prospect, allows a better understanding of the underlying phenomena involved during sintering.

Structural characterization of two new quaternary chalcogenides: CuCo{sub 2}InTe{sub 4} and CuNi{sub 2}InTe{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Delgado, Gerzon E.; Grima-Gallardo, Pedro; Nieves, Luis, E-mail: gerzon@ula.ve [Universidad de Los Andes, Merida (Venezuela, Bolivarian Republic of); Cabrera, Humberto [Centro Multidisciplinario de Ciencias, Instituto Venezolano de Investigaciones Cientificas (IVIC), Merida (Venezuela, Bolivarian Republic of); Glenn, Jennifer R.; Aitken, Jennifer A. [Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA (United States)

2016-11-15

The crystal structure of the chalcogenide compounds CuCo{sub 2}InTe{sub 4} and CuNi{sub 2}InTe{sub 4} , two new members of the I-II{sub 2}-III-VI{sub 4} family, were characterized by Rietveld refinement using X-ray powder diffraction data. Both materials crystallize in the tetragonal space group I4-bar 2m (No. 121), Z = 2, with a stannite-type structure, with the binaries CoTe and NiTe as secondary phases. (author)

Spectroscopy of peaks at microwave range for nanostructure SrFe{sub 12}O{sub 19} and NiFe{sub 2}O{sub 4} ferrite particles

Energy Technology Data Exchange (ETDEWEB)

Ariaee, Sina, E-mail: sina.ariaee@tabrizu.ac.ir; Mehdipour, Mostafa, E-mail: Mostafa_mehdipour67@yahoo.com; Moradnia, Mina, E-mail: mina.moradnia86@gmail.com

2017-05-01

In this paper, (SrFe{sub 12}O{sub 19} and NiFe{sub 2}O{sub 4}) nanostructure ferrite particles were synthesized via the co-precipitation of chloride salts utilizing the sodium hydroxide solution. The resulting precursors were heat-treated at 1100 °C for 4 h. After cooling in the furnace, the ferrite powders were pressed at 0.1 MPa and then sintered at 1200 °C for 4 h. The spectroscopy and characterization of peaks at the microwave range (X-band) for the nanostructure ferrite particles were investigated by the ferromagnetic resonance/transmit-line theories and Reflection Loss (RL) plots. The extracted data from these theoretical and experimental results showed that the natural ferromagnetic resonance can be lead to the narrow peaks and the width of the peaks can be related to the periodic effects. Two kinds of peaks were seen for NiFe{sub 2}O{sub 4} at X-band (8–12 GHz); the narrow peak at (9.8 GHz) was remaining unchanged and consistent while the wide one was shifted from 11 GHz to 8.5 GHz by decreasing the thickness of the samples. These phenomena were also happened for SrFe{sub 12}O{sub 19} samples. The natural resonance was not happened due to the hard magnetic properties of these nano structure particles. - Highlights: • SrFe{sub 12}O{sub 19} and NiFe{sub 2}O{sub 4} nanostructure ferrite particles were synthesized via the co-precipitation of chloride salts. • Two kinds of peaks were seen for NiFe{sub 2}O{sub 4} at X-band (8–12 GHz); these phenomena were also happened for SrFe{sub 12}O{sub 19} samples. • The narrow peaks were remained unchanged and consistent while the wide ones were shifted by decreasing the thickness of the samples. • Characterization procedure was conducted utilizing the ferromagnetic resonance/transmit-line theories and Reflection Loss (RL) plots. • It was concluded that the natural ferromagnetic resonance can be lead to the narrow peaks while the wide ones can be related to the periodic effects.

SImulator of GAlaxy Millimetre/submillimetre Emission (SIGAME): CO emission from massive z=2 main-sequence galaxies

DEFF Research Database (Denmark)

Olsen, Karen P.; Greve, Thomas R.; Brinch, Christian

2016-01-01

is condensed out of the hot and partly ionized SPH gas. The gas is subjected to far-UV radiation fields and cosmic ray ionization rates which are set to scale with the local star formation rate volume density. Level populations and radiative transport of the CO lines are solved with the 3D radiative transfer...... code lime. We have applied sígame to cosmological SPH simulations of three disc galaxies at z = 2 with stellar masses in the range ∼0.5–2 × 1011 M⊙ and star formation rates ∼40–140 M⊙ yr−1. Global CO luminosities and line ratios are in agreement with observations of disc galaxies at z ∼ 2 up.......5 and Cloud (GMC) mass spectrum does...

The significant role of the rare earth ions on the elastic and thermodynamic parameters of LiCoDy- and ZnCoCe-ferrites

Energy Technology Data Exchange (ETDEWEB)

Bishay, Samiha T. [Physics Department, Faculty of Girls for Science, Art and Education Ain Shams University, Asma Fahmi Street, Heliopolis, Cairo (Egypt)]. E-mail: dr_samiha@hotmail.com

2006-06-15

Two types of rare earth ferrites [Li{sub 0.6}Co{sub 0.1}Dy{sub x}Fe{sub 2.3-x}O{sub 4}; 0.0=2] and [Zn{sub 0.5}Co{sub 0.5}Ce{sub y}Fe{sub 2-y}O{sub 4}; 0.0=2] were prepared by standard ceramic technique with a view to investigate their elastic behavior and some essential thermodynamic parameters. The elastic properties were studied by measuring the ultrasonic velocities by adopting the pulse transmission technique. Longitudinal (V{sub L}) and shear (V{sub S}) velocities, Young's modulus (E), Debye temperature ({theta}{sub D}) and specific heat capacity (C{sub v}) have been evaluated for all the investigated samples. The rare earth content as well as its ionic radius plays a significant role in the evaluated parameters. According to the experimental results, the two investigated types of rare earth ferrite are considered as insulator magnetic solids. It was found that for each composition there exists a characteristic temperature, down to which the resonance frequency of the investigated samples drops smoothly, but above this temperature the resonance frequency stays constant. Accordingly, these samples seem to be of importance in industrial applications especially in the field of electronics.

Faraday effect in cubic and tetragonal copper ferrite CuFe.sub.2./sub.O.sub.4./sub. films—Comparative studies

Czech Academy of Sciences Publication Activity Database

Kučera, M.; Kolinský, V.; Višňovský, Š.; Chvostová, Dagmar; Venkataramani, N.; Prasad, S.; Kulkarni, P.D.; Krishnan, R.

2007-01-01

Roč. 316, - (2007), e688-e691 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100522 Keywords : Faraday rotation * magneto-optic * copper ferrite * CuFe 2 O 4 * thin film Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.704, year: 2007

Lattice parameter values and phase transitions for the Cu{sub 2}Cd{sub 1-z}Mn {sub z}GeSe{sub 4} and Cu{sub 2}Cd{sub 1-z}Fe {sub z}GeSe{sub 4} alloys

Energy Technology Data Exchange (ETDEWEB)

Quintero, E. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Tovar, R. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Quintero, M. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela)]. E-mail: mquinter@ula.ve; Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Morocoima, M. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Caldera, D. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Ruiz, J. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela); Mora, A.E. [Laboratorio de Analisis Quimico y Estructural de Materiales, Departamento de Fisica, Universidad de Los Andes, Merida 5101 (Venezuela); Briceno, M. [Laboratorio de Analisis Quimico y Estructural de Materiales, Departamento de Fisica, Universidad de Los Andes, Merida 5101 (Venezuela); Fernandez, J.L. [Laboratorio de Analisis Quimico y Estructural de Materiales, Departamento de Fisica, Universidad de Los Andes, Merida 5101 (Venezuela)

2007-04-25

X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu{sub 2}Cd{sub 1-z}Mn {sub z}GeSe{sub 4} and Cu{sub 2}Cd{sub 1-z}Fe {sub z}GeSe{sub 4} alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu{sub 2}Cd{sub 1-z}Fe {sub z}GeSe{sub 4} system, only two single solid phase fields, the tetragonal stannite {alpha} and the wurtz-stannite {delta} structures were found to occur in the diagram. For the Cu{sub 2}Cd{sub 1-z}Mn {sub z}GeSe{sub 4} system, in addition to the tetragonal stannite {alpha} and the wurtz-stannite {delta} phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling.

Temperature change of various ferrite particles with alternating magnetic field for hyperthermic application

International Nuclear Information System (INIS)

Kim, Dong-Hyun; Lee, Se-Ho; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Shim, In-Bo; Lee, Yong-Keun

2005-01-01

Various ferrites (Fe-, Li-, Ni/Zn/Cu-, Co-, Co/Ni, Ba- and Sr-ferrites) were investigated with respect to their application for hyperthermia. Temperature changes under an alternating magnetic field were observed. The area of hysteresis loop was much larger in the Ba- and Sr-ferrites than for that of the Fe-, Ni/Zn/Cu-, Li-, Co- and Co/Ni-ferrites. Co-ferrite exhibited the most applicable temperature change ΔT=19.25K (29.62W/gs), in distilled water when the field was 110A/m

Thermomagnetic properties of Co1-x Zn x Fe2O4 (x=0.1-0.5) nanoparticles

International Nuclear Information System (INIS)

Arulmurugan, R.; Vaidyanathan, G.; Sendhilnathan, S.; Jeyadevan, B.

2006-01-01

Ultra fine particles of Co 1- x Zn x Fe 2 O 4 with stoichiometric proportion (x) varying from 0.1 to 0.5 were prepared by the usual co-precipitation method. The preparation procedure favored the formation of complex Co-Zn-substituted ferrite nanoparticles. The particles were characterized by XRD. The particle size was calculated by using the Debye-Scherrer formula. The size of the particles precipitated was less than 12 nm. Thermal studies were carried out using simultaneous TG-DTA studies. TG-DTA studies confirmed the presence of associated water content in the precipitated nanoparticles and indicated that ferritization was complete. The temperature-dependent magnetization was recorded at two different fields (5 and 1 kOe). Curie temperature of the powder samples was calculated by extrapolating the linear part of the temperature-dependent magnetization data measured at 1 kOe. Thermomagnetic coefficient which is the first derivative of the temperature-dependent magnetization curve help us in understanding the redistribution of cations between the A and B sites, taking place during the process of heating in the case of nanoparticles. The temperature at which cation redistribution takes place depends on the zinc concentration. From the value of thermomagnetic coefficient and the temperature range, where k T is maximum, it is clear that Co 0.5 Zn 0.5 Fe 2 O 4 particles can be used for the preparation of temperature-sensitive ferrofluid

Construction of Z-scheme Ag{sub 2}CO{sub 3}/N-doped graphene photocatalysts with enhanced visible-light photocatalytic activity by tuning the nitrogen species

Energy Technology Data Exchange (ETDEWEB)

Song, Shaoqing [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang, Jiangxi Province 330013 (China); Meng, Aiyun [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Jiang, Shujuan [Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense, East China Institute of Technology, Nanchang, Jiangxi Province 330013 (China); Cheng, Bei [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Jiang, Chuanjia, E-mail: jiangcj2016@yahoo.com [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2017-02-28

Highlights: • Z-scheme photocatalyst composed of Ag{sub 2}CO{sub 3} and N-doped graphene (NG). • Pyridinic nitrogen species of NG spontaneously promoted plasmonic Ag formation. • Graphitic N of NG facilitated the Z-scheme transfer option and O{sub 2} adsorption. • Z-scheme Ag{sub 2}CO{sub 3}-NG showed high photocatalytic performance. - Abstract: Semiconductor-based photocatalysis has great potential in various environmental and energy applications, and Z-scheme photocatalysts have many advantages over single-component photocatalysts. The construction of a highly efficient Z-scheme photocatalytic system depends on the geometric structure arrangement, microscopic and crystalline form of the stoichiometric species, and it has not been elucidated whether the Z-scheme photocatalysts can be designed by tuning the electronic structures of cocatalysts alone. Here, using N-doped graphene (NG) as cocatalyst, we successfully constructed Z-scheme Ag{sub 2}CO{sub 3}-NG photocatalysts with enhanced activity for the photooxidative degradation of phenol pollutant. It was found that the pyridinic nitrogen species (N{sub p}) of NG could spontaneously reduce Ag{sup +} to produce plasmonic Ag nanoparticles on Ag{sub 2}CO{sub 3}-NG, while the efficiency of the photogenerated charge separation, Z-scheme transfer option, and O{sub 2} adsorption were promoted by the graphitic nitrogen species (N{sub g}). Therefore, the as-designed Z-scheme Ag{sub 2}CO{sub 3}-NG photocatalysts showed much higher activity than Ag{sub 2}CO{sub 3} and its composites with graphene oxide (GO) or reduced GO as cocatalysts in the photocatalytic degradation of phenol. Hence, our results provide a new strategy for exploring advanced Z-scheme photocatalysts with NG as cocatalyst by rationally tuning the N{sub p} and N{sub g} species.

Temperature dependent viscosity of cobalt ferrite / ethylene glycol ferrofluids

Science.gov (United States)

Kharat, Prashant B.; Somvanshi, Sandeep B.; Kounsalye, Jitendra S.; Deshmukh, Suraj S.; Khirade, Pankaj P.; Jadhav, K. M.

2018-04-01

In the present work, cobalt ferrite / ethylene glycol ferrofluid is prepared in 0 to 1 (in the step of 0.2) volume fraction of cobalt ferrite nanoparticles synthesized by co-precipitation method. The XRD results confirmed the formation of single phase spinel structure. The Raman spectra have been deconvoluted into individual Lorentzian peaks. Cobalt ferrite has cubic spinel structure with Fd3m space group. FT-IR spectra consist of two major absorption bands, first at about 586 cm-1 (υ1) and second at about 392 cm-1 (υ2). These absorption bands confirm the formation of spinel-structured cobalt ferrite. Brookfield DV-III viscometer and programmable temperature-controlled bath was used to study the relationship between viscosity and temperature. Viscosity behavior with respect to temperature has been studied and it is revealed that the viscosity of cobalt ferrite / ethylene glycol ferrofluids increases with an increase in volume fraction of cobalt ferrite. The viscosity of the present ferrofluid was found to decrease with increase in temperature.

New technique for the direct analysis of food powders confined in a small hole using transversely excited atmospheric CO(2) laser-induced gas plasma.

Science.gov (United States)

Khumaeni, Ali; Ramli, Muliadi; Deguchi, Yoji; Lee, Yong Inn; Idris, Nasrullah; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Kagawa, Kiichiro

2008-12-01

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

Efficient Visible-Light-Driven Z-Scheme Overall Water Splitting Using a MgTa2O(6-x)N(y)/TaON Heterostructure Photocatalyst for H2 Evolution.

Science.gov (United States)

Chen, Shanshan; Qi, Yu; Hisatomi, Takashi; Ding, Qian; Asai, Tomohiro; Li, Zheng; Ma, Su Su Khine; Zhang, Fuxiang; Domen, Kazunari; Li, Can

2015-07-13

An (oxy)nitride-based heterostructure for powdered Z-scheme overall water splitting is presented. Compared with the single MgTa2O(6-x)N(y) or TaON photocatalyst, a MgTa2O(6-x)N(y)/TaON heterostructure fabricated by a simple one-pot nitridation route was demonstrated to effectively suppress the recombination of carriers by efficient spatial charge separation and decreased defect density. By employing Pt-loaded MgTa2O(6-x)N(y)/TaON as a H2-evolving photocatalyst, a Z-scheme overall water splitting system with an apparent quantum efficiency (AQE) of 6.8% at 420 nm was constructed (PtO(x)-WO3 and IO3(-)/I(-) pairs were used as an O2-evolving photocatalyst and a redox mediator, respectively), the activity of which is circa 7 or 360 times of that using Pt-TaON or Pt-MgTa2O(6-x)N)y) as a H2-evolving photocatalyst, respectively. To the best of our knowledge, this is the highest AQE among the powdered Z-scheme overall water splitting systems ever reported. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation on the effects of milling atmosphere on synthesis of barium ferrite/magnetite nanocomposite

NARCIS (Netherlands)

Molaei, M.J.; Ataie, A.; Raygan, S.; Picken, S.J.

2011-01-01

In this research, barium ferrite /magnetite nanocomposites synthesized via a mechano-chemical route. Graphite was used in order to reduce hematite content of barium ferrite to magnetite to produce a magnetic nanocomposite. The effects of processing conditions on the powder characteristics were

Assesment of (Mn,Co)3O4 powders for possible coating material for SOFC/SOEC interconnects

DEFF Research Database (Denmark)

Szymczewska, D.; Molin, Sebastian; Venkatachalam, Vinothini

2015-01-01

In this work (Mn,Co)3O4 spinel powders with different Mn:Co ratio (1:1 and 1:2) and from different commercial suppliers are evaluated for possible powder for production of interconnect coatings. Sinterability of the powders is evaluated on pressed pellets sintered in oxidizing and in reducing/oxidizing...... that with appropriate powder it is possible to produce adherent protective coating with a well-controlled thickness....... atmospheres. For selected powder, coatings are then prepared by the electrophoretic deposition method on Crofer 22 APU stainless steel coupons. Effects of dispersant/iodine content and deposition voltage and times are evaluated. Thickness as a function of deposition parameters is described. Results show...

Assesment of (Mn,Co)33O4 powders for possible coating material for SOFC/SOEC interconnects

International Nuclear Information System (INIS)

Szymczewska, D.; Jasinski, P.; Molin, S.; Venkatachalam, V.; Chen, M.; Hendriksen, P.V.

2016-01-01

In this work (Mn,Co) 3 O 4 spinel powders with different Mn:Co ratio (1:1 and 1:2) and from different commercial suppliers are evaluated for possible powder for production of interconnect coatings. Sinterability of the powders is evaluated on pressed pellets sintered in oxidizing and in reducing/oxidizing atmospheres. For selected powder, coatings are then prepared by the electrophoretic deposition method on Crofer 22 APU stainless steel coupons. Effects of dispersant/iodine content and deposition voltage and times are evaluated. Thickness as a function of deposition parameters is described. Results show that with appropriate powder it is possible to produce adherent protective coating with a well-controlled thickness

Effect of cobalt ferrite (CoFe2O4) nanoparticles on the growth and development of Lycopersicon lycopersicum (tomato plants).

Science.gov (United States)

López-Moreno, Martha L; Avilés, Leany Lugo; Pérez, Nitza Guzmán; Irizarry, Bianca Álamo; Perales, Oscar; Cedeno-Mattei, Yarilyn; Román, Félix

2016-04-15

Nanoparticles (NPs) have been synthetized and studied to be incorporated in many industrial and medical applications in recent decades. Due to their different physical and chemical properties compared with bulk materials, researchers are focused to understand their interactions with the surroundings. Living organisms such as plants are exposed to these materials and they are able to tolerate different concentrations and types of NPs. Cobalt ferrite (CoFe2O4) NPs are being studied for their application in medical sciences because of their high coercivity, anisotropy, and large magnetostriction. These properties are desirable in magnetic resonance imaging, drug delivery, and cell labeling. This study is aimed to explore the tolerance of Solanum lycopersicum L. (tomato) plants to CoFe2O4 NPs. Tomato plants were grown in hydroponic media amended with CoFe2O4 nanoparticles in a range from 0 to 1000mgL(-1). Exposure to CoFe2O4 NPs did not affect germination and growth of plants. Uptake of Fe and Co inside plant tissues increased as CoFe2O4 nanoparticle concentration was increased in the media. Mg uptake in plant leaves reached its maximum level of 4.9mgg(-1) DW (dry weight) at 125mgL(-1) of CoFe2O4 NPs exposure and decreased at high CoFe2O4 NPs concentrations. Similar pattern was observed for Ca uptake in leaves where the maximum concentration found was 10mgg(-1) DW at 125mgL(-1) of CoFe2O4 NPs exposure. Mn uptake in plant leaves was higher at 62.5mgL(-1) of CoFe2O4 NPs compared with 125 and 250mgL(-1) treatments. Catalase activity in tomato roots and leaves decreased in plants exposed to CoFe2O4 NPs. Tomato plants were able to tolerate CoFe2O4 NPs concentrations up to 1000mgL(-1) without visible toxicity symptoms. Macronutrient uptake in plants was affected when plants were exposed to 250, 500 and 1000mgL(-1) of CoFe2O4 NPs. Published by Elsevier B.V.

Preparation and microwave-infrared absorption of reduced graphene oxide/Cu-Ni ferrite/Al2O3 composites

Science.gov (United States)

De-yue, Ma; Xiao-xia, Li; Yu-xiang, Guo; Yu-run, Zeng

2018-01-01

Reduced graphene oxide (RGO)/Cu-Ni ferrite/Al2O3 composite was prepared by solvothermal method, and its properties were characterized by SEM, x-ray diffraction, energy-dispersive x-ray spectroscopy and FTIR. The electromagnetic parameters in 2-18 GHz and mid-infrared (IR) spectral transmittance of the composite were measured, respectively. The results show that Cu0.7Ni0.3Fe2O4 nanoparticles with an average size of tens nanometers adsorb on surface of RGO, and meanwhile, Al2O3 nanoparticles adhere to the surface of Cu0.7Ni0.3Fe2O4 nanoparticles and RGO. The composite has both dielectric and magnetic loss mechanism. Its reflection loss is lower than -19 dB in 2-18 GHz, and the maximum of -23.2 dB occurs at 15.6 GHz. With the increasing of Al2O3 amount, its reflection loss becomes lower and the maximum moves towards low frequency slightly. Compared with RGO/Cu-Ni ferrite composites, its magnetic loss and reflection loss slightly reduce with the increasing of Al2O3 amount, and the maximum of reflection loss shifts from a low frequency to a high one. However, its broadband IR absorption is significantly enhanced owing to nano-Al2O3. Therefore, RGO/Cu-Ni ferrite/Al2O3 composites can be used as excellent broadband microwave and IR absorbing materials, and maybe have broad application prospect in electromagnetic shielding, IR absorbing and coating materials.

Synthesis of ferrite nanoparticle by milling process for preparation of single domain magnet

International Nuclear Information System (INIS)

Suryadi; Hasbiyallah; Agus S W; Nurul TR; Budhy Kurniawan

2009-01-01

Study of ferrite nanoparticle synthesis for preparation of single domain magnet by milling of scrap magnet material have been done. Sample preparation were done using disk mill continued with high energy milling (HEM). Some powder were taken after 5, 10 dan 20 hours milling using HEM-E3D. The powder were then characterized using X-Ray Fluorescence (XRF), X-Ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). XRF characterization result, confirmed by XRD analysis result, showed that the sample are of Strontium ferrite phase. Microstructure analysis result showed the occurrence of grain refining process of ferrite particle with increasing of milling time. Particle having size of nanometers successfully obtained, although in unhomogeneous distribution. Magnetic properties characterization result showed the increasing of hysteresis curve area of sample for longer milling time and sintering process. (author)

A study of magnetoplumbite-type (M-type) cobalt-titanium-substituted barium ferrite, BaCoxTixFe12-2xO19 (x = 1-6)

International Nuclear Information System (INIS)

Teh, G.B.; Saravanan, N.; Jefferson, D.A.

2007-01-01

Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe 12 O 19 were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo 3 Ti 3 Fe 6 O 19 showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected

AC and DC electrical conductivity, dielectric and magnetic properties of Co{sub 0.65}Zn{sub 0.35}Fe{sub 2-x}Mo{sub x}O{sub 4} (x = 0.0, 0.1 and 0.2) ferrites

Energy Technology Data Exchange (ETDEWEB)

Pradhan, A.K.; Saha, S. [Vidyasagar University, Department of Physics and Techno Physics, Midnapore, West Bengal (India); Nath, T.K. [Indian Institute of Technology Kharagpur, Department of Physics, Kharagpur, West Bengal (India)

2017-11-15

Cobalt-Zinc ferrites are an important material for designing multiferroic composite. The Mo (4d-transition metal) doped Cobalt-Zinc ferrites are synthesized using ceramic (solid-state reaction) method. Investigation of detailed ac and dc electrical conductivity, dielectric and magnetic properties of Co{sub 0.65}Zn{sub 0.35}Fe{sub 2-x}Mo{sub x}O{sub 4} (x = 0.0, 0.1 and 0.2) spinel ferrites have been reported here. The recorded XRD pattern confirms the formation of inverse spinel structure of the material. The dielectric dispersion has been studied in detail and the existence of non-Debye type relaxation behavior has been confirmed. The dielectric tangent loss is found to be very small at high frequency. The ac conductivity follows the correlated barrier hopping like model. Also the conduction process can be best explained on the basis of Verwey-de Boer mechanism. Magnetic phase transition of the material is estimated from magnetization vs. temperature plots. (orig.)

Evaluation of heating conditions of Ni-Zn ferrite obtained by combustion in a microwave oven

International Nuclear Information System (INIS)

Santos, Rafaela L.P.; Diniz, Veronica Cristhina S.; Vieira, Debora A.; Costa, Ana Cristina F.M.; Kiminam, R.H.G.A.

2011-01-01

This paper aims the synthesis by combustion reaction using microwave energy as heating source to obtain ferrite powders of Ni-Zn and its structural, morphological characterization. The influence of power and exposure time in the microwave oven was also investigated. The powders were prepared according to the theory of propellants and explosives using a vitreous silica crucible and urea as fuel. The powders were characterized by: XRD, BET and SEM. The resulted of XRD show only the formation of inverse spinel phase of Ni- Zn ferrite in all samples. The exposure time and power of microwave oven slightly altered the final characteristics of the powders. However, increasing the exposure time was more prominent than the increase of microwave power in both structural and morphological parameters. (author)

The magnetoelectric coupling effect in multiferroic composites based on PZT–ferrite

International Nuclear Information System (INIS)

Bartkowska, J.A.

2015-01-01

In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the values of magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the ferroelectric–ferromagnetic composite PZT–ferrite type, namely PSZTC–NiZn and PBZTN–NiZn. The main component of the ferroelectric–ferromagnetic composite was PZT type powder (with ferroelectric properties), which was synthesized using sintering of a mixture of simple oxides in solid phase. The second element of the ferroelectric–ferromagnetic composite was the ferrite powder (with ferromagnetic properties). Ferrite powder was synthesized using calcination. Next, the mixed components were synthesized using sintering of the mixture of simple oxides in a solid phase (compaction by a free sintering method). The temperature dependences of the dielectric permittivity (ε) for the different frequencies and for both multiferroic composites were investigated. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified. - Highlights: • The magnetoelectric effect at two different ferroelectric–ferromagnetic composites based on a PZT and nickel–zinc ferrite. • Multiferroics composite incorporate both ferroelectric and magnetic phases. • The mechanism of the magnetoelectric coupling between ferroelectric and magnetic properties, in multiferroic composites, is caused by the strain. • The determination of the magnetoelectric coupling coefficient based on a theoretical model and the measurements of dielectric permittivity

The magnetoelectric coupling effect in multiferroic composites based on PZT–ferrite

Energy Technology Data Exchange (ETDEWEB)

Bartkowska, J.A., E-mail: joanna.bartkowska@us.edu.pl

2015-01-15

In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the values of magnetoelectric coupling coefficient, from the temperature dependences of the dielectric permittivity for the ferroelectric–ferromagnetic composite PZT–ferrite type, namely PSZTC–NiZn and PBZTN–NiZn. The main component of the ferroelectric–ferromagnetic composite was PZT type powder (with ferroelectric properties), which was synthesized using sintering of a mixture of simple oxides in solid phase. The second element of the ferroelectric–ferromagnetic composite was the ferrite powder (with ferromagnetic properties). Ferrite powder was synthesized using calcination. Next, the mixed components were synthesized using sintering of the mixture of simple oxides in a solid phase (compaction by a free sintering method). The temperature dependences of the dielectric permittivity (ε) for the different frequencies and for both multiferroic composites were investigated. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified. - Highlights: • The magnetoelectric effect at two different ferroelectric–ferromagnetic composites based on a PZT and nickel–zinc ferrite. • Multiferroics composite incorporate both ferroelectric and magnetic phases. • The mechanism of the magnetoelectric coupling between ferroelectric and magnetic properties, in multiferroic composites, is caused by the strain. • The determination of the magnetoelectric coupling coefficient based on a theoretical model and the measurements of dielectric permittivity.

Structural and magnetic properties of cadmium substituted manganese ferrites prepared by hydrothermal route

Energy Technology Data Exchange (ETDEWEB)

Mostafa, Nasser Y., E-mail: nmost69@yahoo.com [Faculty of Science, Taif University, P.O. Box: 888, Al-Haweiah, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 41522 (Egypt); Zaki, Z.I. [Faculty of Science, Taif University, P.O. Box: 888, Al-Haweiah, Taif (Saudi Arabia); Advanced Materials Division, Central Metallurgical R and D Institute (CMRDI), P.O. Box: 87 Helwan, Cairo (Egypt); Heiba, Z.K. [Faculty of Science, Taif University, P.O. Box: 888, Al-Haweiah, Taif (Saudi Arabia); Physics Department, Faculty of Science, Ain Shams University, Cairo (Egypt)

2013-03-15

Cd-substituted manganese ferrite Mn{sub 1-x}Cd{sub x}Fe{sub 2}O{sub 4} powders with x having values 0.0, 0.1, 0.3 and 0.5 have been synthesized by hydrothermal route at 180 Degree-Sign C in presence of NaOH as mineralizer. The obtained ferrite samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The XRD analysis showed that pure single phases of cubic ferrites were obtained with x upto 0.3. However, sample with x{>=}0.5 showed hexagonal phase of cadmium hydroxide (Cd(OH){sub 2}) besides the ferrite phase. The increase in Cd-substitution upto x=0.3 leads to an increase in the lattice parameter as well as the average crystallite size of the prepared ferrites. The average crystallite size increased by increasing the Cd-content and was in the range of 39-57 nm. According to VSM results, the saturation magnetization increased with Cd ion substitution. - Highlights: Black-Right-Pointing-Pointer Hydrothermal synthesized of mono dispersed Cd-substituted MnFe{sub 2}O{sub 4} nanoparticles. Black-Right-Pointing-Pointer The change in Ms with increasing Cd-substitution was investigated Black-Right-Pointing-Pointer Pure single phases of cubic ferrites were obtained with x up to 0.3 Black-Right-Pointing-Pointer Sample with x{>=}0.5 showed hexagonal phase of Cd(OH){sub 2} beside the ferrite.

Preparation and characterization of polyol assisted ultrafine Cu–Ni–Mg–Ca mixed ferrite via co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Boobalan, T. [Park College of Engineering and Technology, Coimbatore (India); Pavithradevi, S. [Department of Physics, Government College of Technology, Coimbatore (India); Suriyanarayanan, N., E-mail: nsuri22@gmail.com [Department of Physics, PSG Polytechnic College, Coimbatore (India); Manivel Raja, M. [Defence Metallurgical Research Laboratory, Ministry of Defence, Govt. of India, Hyderabad (India); Ranjith Kumar, E., E-mail: ranjueaswar@gmail.com [Dr. NGP Institute of Technology, Coimbatore (India)

2017-04-15

Nanocrystalline spinel ferrite of composition Cu{sub 0.2}Ni{sub 0.2}Mg{sub 0.2}Ca{sub 0.4}Fe{sub 2}O{sub 4} is synthesized by wet hydroxyl co-precipitation method in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol is utilized as the medium which serves as the dissolvable and in addition a complexing specialist. The synthesized particles are annealed at various temperatures. Thermogravimetric investigation affirms that at 280 °C ethylene glycol is dissipated totally and stable phase arrangement happens over 680 °C. FTIR spectra of as synthesized and annealed at 1050 °C recorded between 400 cm{sup −1} and 4000 cm{sup −1}. Structural characterizations of all the samples are carried out by X-ray diffraction (XRD) technique. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) affirm that the particles are spherical and cubic shape with the crystallite size of 12 nm to 32 nm. Magnetic measurements are performed utilizing vibrating sample magnetometer at room temperature. - Highlights: • Polyol improves purity of the spinel ferrite. • TG curves confirm the single phase ferrite is obtained above 680 °C. • Super paramagnetic behavior is seen at lower annealing temperature. • Soft ferromagnetic behavior is obtained at 1050 °C.

Zr powder and Zr-16% Al alloy as getters for O sub 2 , H sub 2 , H sub 2 O, CO and CO sub 2 gases

Energy Technology Data Exchange (ETDEWEB)

Garg, S P [CRM Jat Coll., Hisar (India); Gulbransen, E A [Pittsburgh Univ., PA (USA); Vijendran, P [Bhabha Atomic Research Centre, Bombay (India)

1990-01-01

Both zirconium and its 16 wt% aluminium alloy react with the common gases O{sub 2}, H{sub 2}, H{sub 2}O, CO and CO{sub 2} to form zirconium oxide, hydride and carbide or carbon and a thermochemical and stoichiometric analysis has been made of the several reactions. The capacity and reactivity of 30-40 {mu} zirconium powder and pellets of a 16 wt% aluminium-zirconium alloy, ST 101 getter, were studied using a sensitive vacuum microbalance, a mass spectrometer and Debye-Scherrer X-ray diffraction. The direct hydrogen reaction at 400{sup 0}C and 10 torr pressure and a slow oxidation reaction at 250-600{sup 0}C were used to measure the availability of the materials (capacity) for getter reactions. Special care must be taken to remove water vapour and any other reactive gas from the vacuum system in using the hydrogen method. The hydrogen-getter reaction must be carried out well below 400{sup 0}C if hydrogen is to be removed completely. The reactivity of water vapour in the presence of 10 torr of hydrogen gas was studied at 400{sup 0}C. Fourteen micrograms of water vapour in the reaction system could be detected. The carbon monoxide and carbon dioxide-getter reactions were studied at 500{sup 0}C and 600{sup 0}C at 10 torr pressure. Zirconium powder reacts much faster with both gases as compared to that with St 101 getter, activity of which with oxygen has been stabilized by adding aluminium. Carbon monoxide is produced in the carbon dioxide-getter reaction under conditions of excess gas in the reaction. Carbon and carbide were not observed in the carbon monoxide-getter reaction under excess gas conditions. (author).

Neutron Powder Diffraction Studies of Ca2-xSrxCoWO6 Double Perovskites

International Nuclear Information System (INIS)

Zhou, Qingdi; Kennedy, Brendan; Elcombe, Margaret

2005-01-01

Full text: A series of double perovskite compounds of A 2-x Sr x CoWO 6 (A = Ca, Ba) were synthesized and the room- and variable-temperature structural phase transitions have been studied by synchrotron and neutron powder diffraction techniques. These studies demonstrated that the symmetry increases as the average size of the A-site cation increases. These transitions are associated with the gradual reduction and ultimately removal of the octahedral tiles of the BO 6 octahedra. Temperature dependent structural studies have been undertaken for selected samples. The transition to cubic is continuous in the three Ca doped samples studied as a function of temperature, Ca 2-x Sr x CoWO 6 x = 1.8, 1.7, 1.6, however in each case analysis of the spontaneous strain shows the transition to be tricritical rather than second order in nature. Where observed the temperature induced P2 1 /n to I4/m transition is first order as required by symmetry. (authors)>>>>

Electrochemical characterization of core@shell CoFe{sub 2}O{sub 4}/Au composite

Energy Technology Data Exchange (ETDEWEB)

Carla, Francesco [' Ugo Schiff' , Universita degli Studi di Firenze, Dipartimento di Chimica (Italy); Campo, Giulio; Sangregorio, Claudio; Caneschi, Andrea; Julian Fernandez, Cesar de; Cabrera, Lourdes I., E-mail: lourisa_cabrera@yahoo.com [Universita degli Studi di Firenze, Laboratorio di Magnetismo Molecolare, INSTM, Dipartimento di Chimica (Italy)

2013-08-15

In this paper, we address the synthesis and characterization of the core@shell composite magneto-plasmonic cobalt ferrite-gold (Co-ferrite/Au) nanosystem. The synthesis Co-ferrite/Au nanocomposite is not obvious, hence it was of interest to generate it in a simple straightforward method. Co-ferrite/Au nanocomposite was generated by synthesizing first by thermal decomposition Co-ferrite nanoparticles (NPs). On a second step, ionic gold (Au{sup 3+}) was reduced at the surface of Co-ferrite NPs by ultrasound, to obtain the metallic Au shell. The characterization of the nanomaterial was achieved by microscopy, spectroscopy, and performing magnetic measurements. However, what is attractive about our work is the use of electrochemical techniques as analytical tools. The key technique was cyclic voltammetry, which provided information about the nature and structure of the nanocomposite, allowing us to confirm the core@shell structure.

Some of Physical Properties of Nanostructured (Mg1-xCoxFe2O4 Ferrites Prepared by Sol-Gel Method

Directory of Open Access Journals (Sweden)

Muhammad Abdul Ammer Alsherefi

2018-01-01

Full Text Available Sol-gel auto combustion technique was used to prepare nanoparticles of magnesium-cobalt ferrites with the chemical formula Mg1-xCoxFe2O4 for  (x=0, 0.2, 0.4, 0.6, 0.8, 1, where x added as weight  percentages, and sintering  at temperature (1100 oC. The X-ray patterns of prepared powder has confirmed the structure of cubic spinel structure (fcc. The prepared samples were composed of nearly spherical nano particles .An average particle size of  magnesium-cobalt ferrite  were  calculated  using  Debye Scherer’s relation is equal 53.12 nm. The surface structure of the samples was investigated by Scanning Electron Microscope(SEM. The electromagnetic properties for prepared samples were investigated using Vector Network Analyzer (VNA in X-band microwave region.

Synthesis of nanocrystalline cobalt ferrite through soft chemistry methods: A green chemistry approach using sesame seed extract

Energy Technology Data Exchange (ETDEWEB)

Gingasu, Dana [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Mindru, Ioana, E-mail: imandru@yahoo.com [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Mocioiu, Oana Catalina; Preda, Silviu; Stanica, Nicolae; Patron, Luminita [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Ianculescu, Adelina; Oprea, Ovidiu [Politehnica University of Bucharest, Faculty of Chemistry, 1-7 Polizu Street, 011061, Bucharest (Romania); Nita, Sultana; Paraschiv, Ileana [National Institute for Chemical Pharmaceutical Research and Development, 112 Calea Vitan, 031299, Bucharest (Romania); Popa, Marcela; Saviuc, Crina [University of Bucharest, Faculty of Biology, Microbiology Department, Research Institute of the University of Bucharest-ICUB, Life, Environmental and Earth Sciences Division, 91-95 Splaiul Independentei, Bucharest (Romania); Bleotu, Coralia [Stefan S. Nicolau Institute of Virology, Cellular and Molecular Pathology Department, 285 Mihai Bravu Avenue, Bucharest (Romania); Chifiriuc, Mariana Carmen [University of Bucharest, Faculty of Biology, Microbiology Department, Research Institute of the University of Bucharest-ICUB, Life, Environmental and Earth Sciences Division, 91-95 Splaiul Independentei, Bucharest (Romania)

2016-10-01

The nanocrystalline cobalt ferrites (CoFe{sub 2}O{sub 4}) were obtained through self-combustion and wet ferritization methods using aqueous extracts of sesame (Sesamum indicum L) seeds. The multimetallic complex compounds were characterized by Fourier transform infrared spectroscopy (FTIR), UV-VIS spectroscopy and thermal analysis. Phase identification, morphological evolution and magnetic properties of the obtained cobalt ferrites were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), FTIR and magnetic measurements. FE-SEM investigations revealed the particle size of CoFe{sub 2}O{sub 4} obtained by wet ferritization method ranged between 3 and 20.45 nm. Their antimicrobial, anti-biofilm and cytotoxic properties were evaluated. - Highlights: • CoFe{sub 2}O{sub 4} were obtained by two chemical synthesis methods. • Sesame seed extract was used as gelling or chelating agent. • The morphological features of CoFe{sub 2}O{sub 4} nanoparticles were evaluated. • CoFe{sub 2}O{sub 4} exhibited good microbicidal and anti-biofilm features.

Synthesis of nanoparticles of manganese MnFe2O4 by co-precipitation micellar ferrite: structural and magnetic properties

International Nuclear Information System (INIS)

Alvarez-Paneque, A.; Diaz, S.; Diaz, C.; Santiago-Jacinto, E.; Reguera, E.

2008-01-01

Full text: The microemulsion method was used in reverse, shaped micelles by dodecyl of sodium (NaDBS) in toluene/water system, for MnFe2O4 manganese ferrite magnetic nanoparticles. Were also variants of heat treatments to improve the crystallinity of the material obtained. These were, treatments to reflux to 100 ° C or treatments in an inert atmosphere at temperatures that were varied between 350 and 600 ° C. The retrieved material was characterized by x-ray diffraction (XRD), transmission electron microscopy of high and low resolution (HR-TEM and TEM, respectively), Mössbauer Spectroscopy and vibrational magnetometry. Powder XRD patterns revealed the formation of phase MnFe2O4, cubic type Spinel, of space group Fd3m, accompanied by the minority phase Hematite (a-Fe203) group spatial R-3 c. The size of the nanoparticles was estimated from the profile setting from the pattern of powder by the method of Le Bail, obtaining sizes mean that varied between 5 and 25 mn depending on the heat treatment to which they were subjected. This result was corroborated from TEM micrographs. The vibrational magnetometer showed that the smaller MnFe2O4 nanoparticles, prepared following this route of synthesis They presented a superparamagnetic behavior at room temperature (coercive field and) remanence approximately zeros), which was also confirmed by the study of Mössbauer Spectroscopy. Was also the magnetically inactive layer thickness, of around 0.9 nm, responsible for the decrease in the values of saturation magnetization (as) to decrease the size of nanoparticles. Was obtained a set of nanoparticles with superparamagnetic behavior based in the MnFe2O4 around 5.9 NM in diameter and a-Fe203 around 6.6 NM, as phase secondary. They managed to get this material and the desired magnetic properties optimum crystallinity, applying heat treatment variant proposed in this work, and that It consists of making a reflux at 100 ° C, before the treatment on solid phase under flow N2

Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge)

Energy Technology Data Exchange (ETDEWEB)

Song, Sang-Hoon [Iowa State Univ., Ames, IA (United States)

2007-12-15

Magnetic and magnetoelastic properties of a series of M-substituted cobalt ferrites, CoM_xFe_2-xO₄ (M=Mn, Cr, Ga; x=0.0 to 0.8) and Ge-substituted cobalt ferrites Co_1+xGe_xFe_2-2xO₄ (x=0.0 to 0.6) have been investigated.

Cytotoxicity of ferrite particles by MTT and agar diffusion methods for hyperthermic application

International Nuclear Information System (INIS)

Kim, Dong-Hyun; Lee, Se-Ho; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Shim, In-Bo; Lee, Yong-Keun

2005-01-01

We investigated the cytotoxicity of the prepared various ferrites (Fe-, Li-, Ni/Zn/Cu-, Ba-, Sr-, Co-, Co/Ni-ferrites) using MTT assay as well as agar diffusion method. Their cytotoxicity was compared with that of alginate-encapsulated ferrites. In the MTT assay, Fe 3 O 4 and SrFe 12 O 19 ferrite showed the highest cell viability of 90%. Alginate-encapsulated Ba-ferrite was ranked mildly cytotoxic, whereas their ferrite particles were ranked cytotoxic

Fully dense anisotropic nanocomposite Sm(Co,Fe,Zr,Cu,B)z (z=7.5-12) magnets

International Nuclear Information System (INIS)

Huang, M.Q.; Turgut, Z.; Wheeler, B.; Lee, D.; Liu, S.; Ma, B.M.; Peng, Y.G.; Chu, S.Y.; Laughlin, D.E.; Horwath, J.C.; Fingers, R.T.

2005-01-01

Fully dense anisotropic nanocomposite Sm(Co 0.58 Fe 0.31 Zr 0.05 Cu 0.04 B 0.02 ) z (z=7.5-12) magnets have been synthesized via rapid hot pressing and hot deformation processes. The highest (BH) max ∼10.6 MGOe was observed for a magnet with z=10. X-ray diffraction and M-H measurements indicated that the easy magnetization direction of magnets prefers to be in the hot pressing direction. Transmission electron microscopy investigation confirmed that plastic deformation is an important route for forming magnetic anisotropy in the Sm-Co-type nanocomposite magnets. Some stripe and/or platelike patterns have been observed inside the nanograins (50-200 nm), which may present as twins, and stacking faults. The (0001) twins have been observed in the 2:17R phase

Evaluation of Antioxidant and Cytotoxicity Activities of Copper Ferrite (CuFe2O4 and Zinc Ferrite (ZnFe2O4 Nanoparticles Synthesized by Sol-Gel Self-Combustion Method

Directory of Open Access Journals (Sweden)

Samikannu Kanagesan

2016-08-01

Full Text Available Spinel copper ferrite (CuFe2O4 and zinc ferrite (ZnFe2O4 nanoparticles were synthesized using a sol-gel self-combustion technique. The structural, functional, morphological and magnetic properties of the samples were investigated by Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, Transmission electron microscopy (TEM and vibrating sample magnetometry (VSM. XRD patterns conform to the copper ferrite and zinc ferrite formation, and the average particle sizes were calculated by using a transmission electron microscope, the measured particle sizes being 56 nm for CuFe2O4 and 68 nm for ZnFe2O4. Both spinel ferrite nanoparticles exhibit ferromagnetic behavior with saturation magnetization of 31 emug−1 for copper ferrite (50.63 Am2/Kg and 28.8 Am2/Kg for zinc ferrite. Both synthesized ferrite nanoparticles were equally effective in scavenging 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH free radicals. ZnFe2O4 and CuFe2O4 nanoparticles showed 30.57% ± 1.0% and 28.69% ± 1.14% scavenging activity at 125 µg/mL concentrations. In vitro cytotoxicity study revealed higher concentrations (>125 µg/mL of ZnFe2O4 and CuFe2O4 with increased toxicity against MCF-7 cells, but were found to be non-toxic at lower concentrations suggesting their biocompatibility.

Role of Cu2+ Concentration on the Microstructure and Gas Sensing Properties of Ni1-xCuxFe2O4 (0 ≤ x ≤ 0.8 Ferrite

Directory of Open Access Journals (Sweden)

Elena Rezlescu

2008-04-01

Full Text Available The microstructure and gas sensor properties of some nanostructured soft ferrites (Ni1-xCuxFe2O4, x = 0.2, 0.4, 0.6, 0.8 are studied. Using sol-gel self-combustion technology and subsequent heat treatment were prepared ferrite powders, having molecular scale homogeneity and nanosized granulation. The scanning electron microscopy (SEM was used to investigate morphology and pore structure. The effect of operating temperature and copper content on the fundamental features of a sensor element such as sensitivity and response time towards acetone, ethanol and LPG vapour has been studied. All samples are sensitive to ethanol and acetone and have a poor sensitivity to LPG. For a large copper content (x > 0.4 the electrical response to ethanol is larger than that to acetone, at the same working temperature, of 280oC. Among the investigated ferrites, Ni0,2Cu0,8Fe2O4 composition shows the best sensitivity to ethanol (about 70 % at operating temperature of 280ºC. The gas sensitivity increases with increasing gas concentration from 25 to 150 ppm, whereas the response time decreases.

Effect of La-CO substitution on the crystal structure and magnetic properties of low temperature sintered Sr1-xLaxFe12-xCoxO19 (x=0-0.5) ferrites

Science.gov (United States)

Peng, Long; Li, Lezhong; Wang, Rui; Hu, Yun; Tu, Xiaoqiang; Zhong, Xiaoxi

2015-11-01

The La-Co substituted Sr1-xLaxFe12-xCoxO19 (x=0-0.5) ferrites with appropriate Bi2O3 additive were prepared at a low sintering temperature of 890 °C compatible with LTCC (low temperature co-fired ceramics) systems, and the effect of La-Co substitution on their crystal structure and magnetic properties was investigated. The results show that the pure M-type phase is successfully obtained when the La-Co substitution amount x does not exceed 0.3. However, the single M-type phase structure transforms to multiphase structure with further increased x, where the α-Fe2O3 phase and La2O3 phase coexist with the M-type phase. Moreover, the saturation magnetization Ms, magnetic anisotropy field Ha, intrinsic coercivity Hci, and Curie temperature TC of the ferrites depend on the La-Co substitution amount strongly, which are suggested to be determined by the partially substitution of La3+-Co2+ ions for Sr2+-Fe3+ ions with x not higher than 0.3. It is found that the obtained Sr1-xLaxFe12-xCoxO19 (x=0.2 and 0.3) ferrites can provide improved magnetic properties (Ms>62 emu/g, Ha>1400 kA/m, and Hci>320 kA/m) as low temperature sintered M-type hexaferrites for microwave LTCC applications.

Lattice parameter values and phase transitions for the Cu{sub 2}Cd{sub 1-z}Mn{sub z}SnSe{sub 4} and Cu{sub 2}Cd{sub 1-z}Fe{sub z}SnSe{sub 4} alloys

Energy Technology Data Exchange (ETDEWEB)

Moreno, E. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Quintero, M., E-mail: mquinter@ula.v [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Morocoima, M.; Quintero, E.; Grima, P.; Tovar, R.; Bocaranda, P. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Delgado, G.E.; Contreras, J.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Mora, A.E.; Briceno, J.M.; Avila Godoy, R.; Fernandez, J.L. [Laboratorio de Analisis Quimico y Estructural de Materiales, Departamento de Fisica, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Henao, J.A.; Macias, M.A. [Grupo de Investigacion en Quimica Estructural (GIQUE), Facultad de Ciencias, Escuela de Quimica, Universidad Industrial de Santander, Apartado aereo 678, Bucaramanga (Colombia)

2009-11-03

X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu{sub 2}Cd{sub 1-z}Mn{sub z}SnSe{sub 4} and Cu{sub 2}Cd{sub 1-z}Fe{sub z}SnSe{sub 4} alloy systems. The diffraction patterns were used to show the equilibrium conditions and to derive lattice parameter values. For Cu{sub 2}Cd{sub 0.8}Fe{sub 0.2}SnSe{sub 4} as well as for Cu{sub 2}Cd{sub 0.2}Fe{sub 0.8}SnSe{sub 4} the crystal structures were refined using the Rietveld method. It was found that the internal distortion parameter sigma decreases as Cd is replaced by either Mn and/or Fe. For the Cu{sub 2}Cd{sub 1-z}Mn{sub z}SnSe{sub 4} and Cu{sub 2}Cd{sub 1-z}Fe{sub z}SnSe{sub 4} alloy systems, only two single solid phase fields, the tetragonal stannite alpha(I4-bar2m) and the wurtz-stannite delta (Pmn2{sub 1}) structures were found to occur in the diagram. In addition to the tetragonal stannite alpha phase extra X-ray diffraction lines due to MnSe and/or FeSe{sub 2} were observed for as grown samples in the range 0.7 < z < 1.0. However, it was found that the amount of the extra phase decreased for the compressed samples.

Al and PEG effect on structural and physicochemical properties of CoFe{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Mostaghni, Fatemeh; Abed, Yasaman, E-mail: mostaghnif@yahoo.com [Payam Noor University (Iran, Islamic Republic of)

2017-05-15

In this work, pure and Alumina doped cobalt ferrite nanoparticles CoFe{sub 2-x}Al{sub x}O{sub 4} (for x = 0.44) have been synthesized by the sol gel method. The influence of alumina doping on the morphological and mechanical properties of CoFe{sub 2}O{sub 4} nano-particles were investigated by means of X-ray powder diffraction (XRD) and Rietveld analysis. XRD analysis confirmed that the single phase formation of pure nano particles with the expected cubic inverse spinel structure with Fd3m space group and without any impurity phase. Alumina doping were led to a decrease in the crystallite size, lattice parameter, elastic constants and magnitude of moduli. It is explained on the basis of the replacement of Fe ions with half-filled d-shell (3d{sup 5}) and larger radius by Al{sup 3+} ions with a completely filled shell (2p{sup 6}) and smaller radius. (author)

Structural and magnetic characteristics of PVA/CoFe{sub 2}O{sub 4} nano-composites prepared via mechanical alloying method

Energy Technology Data Exchange (ETDEWEB)

Rashidi, S.; Ataie, A., E-mail: aataie@ut.ac.ir

2016-08-15

Highlights: • Single phase CoFe{sub 2}O{sub 4} nano-particles synthesized in one step by mechanical alloying. • PVA/CoFe{sub 2}O{sub 4} magnetic nano-composites were fabricated via mechanical milling. • FTIR confirmed the interaction between PVA and magnetic CoFe{sub 2}O{sub 4} particles. • Increasing in milling time and PVA amount led to well dispersion of CoFe{sub 2}O{sub 4}. - Abstract: In this research, polyvinyl alcohol/cobalt ferrite nano-composites were successfully synthesized employing a two-step procedure: the spherical single-phase cobalt ferrite of 20 ± 4 nm mean particle size was synthesized via mechanical alloying method and then embedded into polymer matrix by intensive milling. The results revealed that increase in polyvinyl alcohol content and milling time causes cobalt ferrite particles disperse more homogeneously in polymer matrix, while the mean particle size and shape of cobalt ferrite have not been significantly affected. Transmission electron microscope images indicated that polyvinyl alcohol chains have surrounded the cobalt ferrite nano-particles; also, the interaction between polymer and cobalt ferrite particles in nano-composite samples was confirmed. Magnetic properties evaluation showed that saturation magnetization, coercivity and anisotropy constant values decreased in nano-composite samples compared to pure cobalt ferrite. However, the coercivity values of related nano-composite samples enhanced by increasing PVA amount due to domain wall mechanism.

Metal ferrite oxygen carriers for chemical looping combustion of solid fuels

Science.gov (United States)

Siriwardane, Ranjani V.; Fan, Yueying

2017-01-31

The disclosure provides a metal ferrite oxygen carrier for the chemical looping combustion of solid carbonaceous fuels, such as coal, coke, coal and biomass char, and the like. The metal ferrite oxygen carrier comprises MFe.sub.xO.sub.y on an inert support, where MFe.sub.xO.sub.y is a chemical composition and M is one of Mg, Ca, Sr, Ba, Co, Mn, and combinations thereof. For example, MFe.sub.xO.sub.y may be one of MgFe.sub.2O.sub.4, CaFe.sub.2O.sub.4, SrFe.sub.2O.sub.4, BaFe.sub.2O.sub.4, CoFe.sub.2O.sub.4, MnFeO.sub.3, and combinations thereof. The MFe.sub.xO.sub.y is supported on an inert support. The inert support disperses the MFe.sub.xO.sub.y oxides to avoid agglomeration and improve performance stability. In an embodiment, the inert support comprises from about 5 wt. % to about 60 wt. % of the metal ferrite oxygen carrier and the MFe.sub.xO.sub.y comprises at least 30 wt. % of the metal ferrite oxygen carrier. The metal ferrite oxygen carriers disclosed display improved reduction rates over Fe.sub.2O.sub.3, and improved oxidation rates over CuO.

Morphology and composition tailoring of Co x Fe3 - x O4 nanoparticles

Science.gov (United States)

Fernandes de Medeiros, I. A.; Madigou, V.; Lopes-Moriyama, A. L.; Pereira de Souza, C.; Leroux, Ch.

2018-01-01

Nano-octahedra of cobalt ferrite Co x Fe3 - x O4 (1 ≤ x hydrothermal method using nitrates as precursors. For the first time, single-phased nano-octahedra of cobalt-rich ferrite Co x Fe3 - x O4 ( x = 1.5) were synthesized. The nano-octahedra are crystallized in a normal spinel structure, with tetrahedral sites occupied by Co2+. This specific octahedral shape was obtained with anionic, cationic, and nonionic surfactants. The nature of the surfactant influenced the chemical composition of the powder and the size of the nano-octahedra. The {100} truncation of the octahedra is more pronounced for the small particles. For the first time, single-phased nanoparticles with as much as x = 1.8 cobalt were synthesized with ethylene glycol as solvent. These nanoparticles, around 8 nm in size, have no specific shape and possess a lacunar spinel structure similar to maghemite. The samples were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy.

Cytotoxicity of ferrite particles by MTT and agar diffusion methods for hyperthermic application

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong-Hyun [Brain Korea 21 Project for Medical Science, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Lee, Se-Ho [Brain Korea 21 Project for Medical Science, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Kim, Kyoung-Nam [Brain Korea 21 Project for Medical Science, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Kim, Kwang-Mahn [Brain Korea 21 Project for Medical Science, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Department and Research Institute of Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of); Shim, In-Bo [Department of Electronic Physics, Kookmin University, Seoul 136-702 (Korea, Republic of); Lee, Yong-Keun [Brain Korea 21 Project for Medical Science, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of) and Department and Research Institute of Dental Biomaterials and Bioengineering, Yonsei University College of Dentistry, Seoul 120-752 (Korea, Republic of)]. E-mail: leeyk@yumc.yonsei.ac.kr

2005-05-15

We investigated the cytotoxicity of the prepared various ferrites (Fe-, Li-, Ni/Zn/Cu-, Ba-, Sr-, Co-, Co/Ni-ferrites) using MTT assay as well as agar diffusion method. Their cytotoxicity was compared with that of alginate-encapsulated ferrites. In the MTT assay, Fe{sub 3}O{sub 4} and SrFe{sub 12}O{sub 19} ferrite showed the highest cell viability of 90%. Alginate-encapsulated Ba-ferrite was ranked mildly cytotoxic, whereas their ferrite particles were ranked cytotoxic.

Diphosphine- and CO-Induced Fragmentation of Chloride-bridged Dinuclear Complex and Cp*Ir(mu-Cl)(3)Re(CO)(3) and Attempted Synthesis of Cp*Ir(mu-Cl)(3)Mn(CO)(3): Spectroscopic Data and X-ray Diffraction Structures of the Pentamethylcyclopentadienyl Compounds [Cp*IrCl{(Z)-Ph2PCH = CHPPh2}][Cl]center dot 2CHCl(3) and Cp*Ir(CO)Cl-2

Energy Technology Data Exchange (ETDEWEB)

Hammons, Casey [University of North Texas; Wang, Xiaoping [ORNL; Nesterov, Vladimir [University of North Texas; Richmond, Michael G. [University of North Texas

2010-01-01

The confacial bioctahedral compound Cp*Ir(mu-Cl)(3)Re(CO)(3) (1) undergoes rapid fragmentation in the presence of the unsaturated diphosphine ligand (Z)-Ph2PCH = CHPPh2 to give the mononuclear compounds [Cp*IrCl {(Z)-Ph2PCH = CHPPh2}][Cl] (2) and fac-ClRe(CO)(3)[(Z)-Ph2PCH = CHPPh2] (3). 2 has been characterized by H-1 and P-31 NMR spectroscopy and X-ray diffraction analysis. 2 center dot 2CHCl(3) crystallizes in the monoclinic space group C2/c, a = 35.023 (8) angstrom, b = 10.189 (2) angstrom, c = 24.003 (6) angstrom, b = 103.340 (3), V = 8,335 (3) angstrom 3, Z = 8, and d(calc) = 1.647 Mg/m(3); R = 0.0383, R-w = 0.1135 for 8,178 reflections with I> 2 sigma(I). The Ir(III) center in 2 exhibits a six-coordinate geometry and displays a chelating diphosphine group. Compound 1 reacts with added CO with fragmentation to yield the known compounds Cp*Ir(CO)Cl-2 (4) and ClRe(CO)(5) (5) in near quantitative yield by IR spectroscopy. Using the protocol established by our groups for the synthesis of 1, we have explored the reaction of [Cp*IrCl2](2) with ClMn(CO)(5) as a potential route to Cp*Ir(mu-Cl)(3)Mn(CO)(3); unfortunately, 4 was the only product isolated from this reaction. The solid-state structure of 4 was determined by X-ray diffraction analysis. 4 crystallizes in the triclinic space group P-1, a = 7.4059 (4) angstrom, b = 7.8940 (4) angstrom, c = 11.8488 (7) angstrom, alpha = 80.020 (1), beta = 79.758 (1), gamma = 68.631 (1), V = 630.34 (6) angstrom(3), Z = 2, and d(calc) = 2.246 Mg/m(3); R = 0.0126, R-w = 0.0329 for 2,754 reflections with I> 2 sigma(I). The expected three-legged piano-stool geometry in 4 has been crystallographically confirmed.

Magnetic, dielectric and microwave absorption properties of rare earth doped Ni–Co and Ni–Co–Zn spinel ferrites

Energy Technology Data Exchange (ETDEWEB)

Stergiou, Charalampos, E-mail: stergiou@cperi.certh.gr

2017-03-15

In this article we analyze the electromagnetic properties of rare earth substituted Ni–Co and Ni–Co–Zn cubic ferrites in the microwave band, along with their performance as microwave absorbing materials. Ceramic samples with compositions Ni{sub 0.5}Co{sub 0.5}Fe{sub 2−x}R{sub x}O{sub 4} and Ni{sub 0.25}Co{sub 0.5}Zn{sub 0.25}Fe{sub 2−x}R{sub x}O{sub 4} (R=Y and La, x=0, 0.02), fabricated with the solid state reaction method, were characterized with regard to the complex permeability μ*(f) and permittivity ε*(f) up to 20 GHz. The rare earth substitutions basically affect the microwave μ*(f) spectra and the dynamic magnetization mechanisms of domain wall motion and magnetization rotation. Key parameters for this effect are the reduced magnetocrystalline anisotropy and the created crystal inhomogeneities. Moreover, permittivity is increased with the Y and La content, due to the enhancement of the dielectric orientation polarization. Regarding the electromagnetic wave attenuation, the prepared ferrites exhibit narrowband return losses (RL) by virtue of the cancellation of multiple reflections, when their thickness equals an odd multiple of quarter-wavelength. Interestingly, the zero-reflection conditions are satisfied in the vicinity of the ferromagnetic resonance. As the rare earth doping shifts this mechanism to lower frequencies, loss peaks with RL>46 dB occur at 4.1 GHz and 5 GHz for Y and La-doped Ni–Co–Zn spinels, whereas peaks with RL>40 dB appear at 18 GHz and 19 GHz for Y and La-doped Ni–Co spinels, respectively. The presented experimental findings underline the potential of cubic ferrites with high Co concentration in the suppression of electromagnetic reflections well above the 1 GHz region. - Highlights: • Due to cation distribution, magnetic anisotropy drops in Y and La doped samples. • Microwave permeability spectra shift to lower frequencies with rare earth doping. • Permittivity is increased due to crystal modifications

Micromagnetic simulations of spinel ferrite particles

International Nuclear Information System (INIS)

Dantas, Christine C.; Gama, Adriana M.

2010-01-01

This paper presents the results of simulations of the magnetization field ac response (at 2-12 GHz) of various submicron ferrite particles (cylindrical dots). The ferrites in the present simulations have the spinel structure, expressed here by M 1 - n Zn n Fe 2 O 4 (where M stands for a divalent metal), and the parameters chosen were the following: (a) for n=0: M={Fe, Mn, Co, Ni, Mg, Cu }; (b) for n=0.1: M = {Fe, Mg} (mixed ferrites). These runs represent full 3D micromagnetic (one-particle) ferrite simulations. We find evidences of confined spin waves in all simulations, as well as a complex behavior nearby the main resonance peak in the case of the M = {Mg, Cu} ferrites. A comparison of the n=0 and n=0.1 cases for fixed M reveals a significant change in the spectra in M = Mg ferrites, but only a minor change in the M=Fe case. An additional larger scale simulation of a 3 by 3 particle array was performed using similar conditions of the Fe 3 O 4 (magnetite; n=0, M = Fe) one-particle simulation. We find that the main resonance peak of the Fe 3 O 4 one-particle simulation is disfigured in the corresponding 3 by 3 particle simulation, indicating the extent to which dipolar interactions are able to affect the main resonance peak in that magnetic compound.

hermo-Physical and Mechanical Properties of Unsaturated Polyester /Cobalt Ferrite Composites

Directory of Open Access Journals (Sweden)

Lamees Salam Faiq

2017-04-01

Full Text Available Unsaturated polyester was used as a matrix which was filled with different percentages of cobalt ferrite using hand lay-up method. Cobalt ferrite was synthesized using solid state ceramic method with reagent of CoO and Fe2O3. Mechanical properties such tensile strength, Young's modulus and shore D hardness of the composite have been studied. All these properties have increased by 10% with increasing cobalt ferrite contents. Also the thermal properties such thermal conductivity and specific heat capacity are highly increased as the ferrite content increased, while the thermal diffusivity increased by 22 %. On the other hand dielectric strength of composite has been measured which increased by 50% by increasing the cobalt ferrite content.

The impact of the iron content on the microstructure and magnetic properties of M-type ferrites Sr0.45Ca0.25La0.30FexCo0.25O19

International Nuclear Information System (INIS)

Yang, Yujie; Liu, Xiansong; Jin, Dali

2014-01-01

Highlights: • Sr 0.45 Ca 0.25 La 0.30 Fe x Co 0.25 O 19 (10.45 ≤ x ≤ 12.25) hexaferrites were prepared by a conventional ceramic method. • The hexagonal structure is observed for the magnets and the particles are distributed evenly. • B r , H cb , H cj , and (BH) max of the magnets first increase with iron content (x) ranging from 10.45 to 11.05 and then decrease when iron content (x) ≥ 11.05. • When iron content (x) = 11.05, B r , H cb , H cj , and (BH) max of the magnets reach the maximum values. - Abstract: M-type ferrite Sr 0.45 Ca 0.25 La 0.30 Fe x Co 0.25 O 19 (10.45 ≤ x ≤ 12.25) magnetic powders and magnets were prepared by a conventional ceramic method. Phase components of the magnetic powders were examined by X-ray diffraction. There is only the magnetoplumbite-type phase in magnetic powders with iron content (x) ranging from 10.45 to 11.65. When iron content (x) ≥ 11.85, hematite (α-Fe 2 O 3 ) phase begins to occur. The morphology of the magnets was investigated by a field emission scanning electron microscopy. The magnets have formed a hexagonal structure and the particles are distributed evenly. Magnetic properties of the magnets and magnetic powders were measured by a permanent magnetic measuring equipment and a vibrating sample magnetometer, respectively. The remanence, intrinsic coercivity, magnetic induction coercivity, and maximum energy product first increase with iron content (x) of range 10.45–11.05 and then decrease when iron content (x) continues to increase. The magnetic properties at x = 11.05 reach the maximum values

Effect of zinc substitution on the structural, electrical and magnetic properties of nano-structured Ni0.5Co0.5Fe2O4 ferrites

Science.gov (United States)

Babu, K. Vijaya; Sailaja, B.; Jalaiah, K.; Shibeshi, Paulos Taddesse; Ravi, M.

2018-04-01

A series of Ni0.5Co0.5-xZnxFe2O4 (x = 0, 0.02, 0.04 and 0.06) nanoferrites were synthesized by sol-gel method using citric acid as chelating reagent. The synthesized ferrite systems are characterized by XRD, SEM, FTIR, ESR and dielectric techniques. The formation of cubic spinel phase belonging to space group Fd3m is identified from the X-ray diffraction patterns. SEM showed the particles are in spherical shape with an average grain size 5-10 nm. FTIR spectra portrait the fundamental absorption bands in the range 400-600 cm-1 relating to octahedral and tetrahedral sites. Dielectric properties are investigated over the frequency range of 20 Hz to 1 MHz at room temperature. A difference in dielectric constant (εr) and dissipation factor (tanδ) of the ferrites has been observed. The dielectric constant and dielectric loss tangent decreases exponentially with increase in frequency. The obtained results are good agreeing with the reported values.

Topotactic Synthesis of Porous Cobalt Ferrite Platelets from a Layered Double Hydroxide Precursor and Their Application in Oxidation Catalysis.

Science.gov (United States)

Ortega, Klaus Friedel; Anke, Sven; Salamon, Soma; Özcan, Fatih; Heese, Justus; Andronescu, Corina; Landers, Joachim; Wende, Heiko; Schuhmann, Wolfgang; Muhler, Martin; Lunkenbein, Thomas; Behrens, Malte

2017-09-12

Monocrystalline, yet porous mosaic platelets of cobalt ferrite, CoFe 2 O 4 , can be synthesized from a layered double hydroxide (LDH) precursor by thermal decomposition. Using an equimolar mixture of Fe 2+ , Co 2+ , and Fe 3+ during co-precipitation, a mixture of LDH, (Fe II Co II ) 2/3 Fe III 1/3 (OH) 2 (CO 3 ) 1/6 ⋅m H 2 O, and the target spinel CoFe 2 O 4 can be obtained in the precursor. During calcination, the remaining Fe II fraction of the LDH is oxidized to Fe III leading to an overall Co 2+ :Fe 3+ ratio of 1:2 as required for spinel crystallization. This pre-adjustment of the spinel composition in the LDH precursor suggests a topotactic crystallization of cobalt ferrite and yields phase pure spinel in unusual anisotropic platelet morphology. The preferred topotactic relationship in most particles is [111] Spinel ∥[001] LDH . Due to the anion decomposition, holes are formed throughout the quasi monocrystalline platelets. This synthesis approach can be used for different ferrites and the unique microstructure leads to unusual chemical properties as shown by the application of the ex-LDH cobalt ferrite as catalyst in the selective oxidation of 2-propanol. Compared to commercial cobalt ferrite, which mainly catalyzes the oxidative dehydrogenation to acetone, the main reaction over the novel ex-LDH cobalt is dehydration to propene. Moreover, the oxygen evolution reaction (OER) activity of the ex-LDH catalyst was markedly higher compared to the commercial material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanosynthesis of MFe2O4 (M = Co, Ni, and Zn Magnetic Nanoparticles for Pb Removal from Aqueous Solution

Directory of Open Access Journals (Sweden)

America R. Vazquez-Olmos

2016-01-01

Full Text Available Adsorption of Pb(II from aqueous solution using MFe2O4 nanoferrites (M = Co, Ni, and Zn was studied. Nanoferrite samples were prepared via the mechanochemical method and were characterized by X-ray powder diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, micro-Raman, and vibrating sample magnetometry (VSM. XRD analysis confirms the formation of pure single phases of cubic ferrites with average crystallite sizes of 23.8, 19.4, and 19.2 nm for CoFe2O4, NiFe2O4, and ZnFe2O4, respectively. Only NiFe2O4 and ZnFe2O4 samples show superparamagnetic behavior at room temperature, whereas CoFe2O4 is ferromagnetic. Kinetics and isotherm adsorption studies for adsorption of Pb(II were carried out. A pseudo-second-order kinetic describes the sorption behavior. The experimental data of the isotherms were well fitted to the Langmuir isotherm model. The maximum adsorption capacity of Pb(II on the nanoferrites was found to be 20.58, 17.76, and 9.34 mg·g−1 for M = Co, Ni, and Zn, respectively.

Impact of larger rare earth Pr{sup 3+} ions on the physical properties of chemically derived Pr{sub x}CoFe{sub 2−x}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pachpinde, A.M.; Langade, M.M. [Department of Chemistry, Jawahar Art Science and Commerce College Andur, Osmanabad, MS (India); Lohar, K.S.; Patange, S.M. [Materials Research Laboratory, Srikrishna Mahavidyalaya Gunjoti, Omerga, Osmanabad 413 613, MS (India); Shirsath, Sagar E., E-mail: shirsathsagar@hotmail.com [Spin Device Technology Center, Department of Information Engineering, Shinshu University, Nagano 380 8553 (Japan)

2014-01-31

Highlights: • Rare earth Pr{sup 3+} substituted CoFe{sub 2}O{sub 4}. • Sol–gel auto combustion synthesis. • XRD and IR spectra reveal the spinel structure. • Magnetization and coercivity increased with Pr{sup 3+} substitution. - Abstract: Rare earth Pr{sup 3+} ions with its larger ionic radii substituted CoFe{sub 2}O{sub 4} nanoparticles with x ranging from 0.0 to 0.1 were synthesized by sol–gel auto-combustion chemical method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM) were employed to characterize the physical properties of these ferrite nanoparticles. XRD pattern reveals the formation of cubic spinel ferrite with the signature of PrFeO{sub 3} phases for x ⩾ 0.05. SEM images show that the synthesized samples are in good homogeneity with uniformly distributed grain. The results of IR spectroscopy analysis indicated that the functional groups of cobalt spinel ferrite were formed during the sol–gel process. The cations distribution between the tetrahedral (A-site) and octahedral sites (B-site) has been estimated by XRD analysis. Room temperature magnetic measurement shows saturation magnetization and coercivity increased from 54.7 to 64.2 emu/g and 644 to 1013 Oe, respectively with the increasing Pr{sup 3+} substitution.

Effect of temperature on sintered austeno-ferritic stainless steel microstructure

Energy Technology Data Exchange (ETDEWEB)

Munez, C.J. [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, 28933 Mostoles, Madrid (Spain)], E-mail: claudio.munez@urjc.es; Utrilla, M.V.; Urena, A. [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, 28933 Mostoles, Madrid (Spain)

2008-09-08

The influence of temperature on microstructural changes of sintered austeno-ferritic steels has been investigated. PM stainless steels have been obtained by sintering mixtures of austenitic and ferritic stainless steel powders. Only temperature-induced phase transformation was observed in austenite, as a result of elements interdiffusion between both phases. Microstructural characterization was completed with atomic force microscopy (AFM) and micro- and nano-indentation test, it is revealed an increase in the hardness with respect to the solutionized materials.

The Effect of Catalyst Type on The Microstructure and Magnetic Properties of Synthesized Hard Cobalt Ferrite Nanoparticles.

Directory of Open Access Journals (Sweden)

Shaima'a Jaber Kareem

2018-02-01

Full Text Available A sol-gel process prepared the nanoparticles of hard cobalt ferrite (CoFe2O4. Cobalt nitrate hexahydrate (Co (NO32⋅6H2O, iron nitrate nonahydrate (Fe (NO33⋅9H2O with using two catalysis acid (citric acid and alkaline (hydroxide ammonium were used as precursor materials. Crystallization behavior of the CoFe2O4 nanoparticles were studied by X-ray diffraction (XRD. Nanoparticles phases can change from amorphous to spinel ferrite crystalline depending on the calcinated temperature at 600°C, with using citric acid as a catalysis without finding forgone phase, while using hydroxide ammonium was shown second phase (α-Fe2O3 with CoFe2O4. Crystallite size was measured by Scherrer’s formula about (25.327 nm and (27.119 nm respectively. Structural properties were investigated by FTIR, which was appeared main bond of (Fe-O, (Co-O, (C-O, and (H-O. Scanning electron microscopy (FE- SEM was shown the microstructure observation of cobalt ferrite and the particle size at the range about (28.77-42.97 nm. Magnetization measurements were carried out on a vibrating sample magenometer (VSM that exhibited hard spinel ferrite.

Fabrication and electromagnetic properties of flake ferrite particles based on diatomite

International Nuclear Information System (INIS)

Zhang Deyuan; Zhang Wenqiang; Cai Jun

2011-01-01

Hexagonal ferrite BaZn 1.1 Co 0.9 Fe 16 O 27 coated surfaces of diatomite flakes of low density were synthesized by a sol-gel method. The phase structures, morphologies, particle size and chemical compositions of the composites were characterized by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectroscopy. The results show that hexagonal ferrite coated diatomite flakes can be achieved, and that the coating consisted of BaZn 1.1 Co 0.9 Fe 16 O 27 nanoparticles. The vibranting sample magnetometer results reveal that the flake ferrite particles have static magnetic properties. The complex permeability and permittivity of the composites were measured in the frequency range of 1-18 GHz. The microwave absorption properties of these ferrite particles are discussed. The results indicate that the flake ferrites have the potential to be used as a lightweight broad band microwave absorber. - Highlights: → We synthesize the flake ferrite particles using diatomite as a template. → Flake ferrite particles' coating layers are constituted by BaZn 1.1 Co 0.9 Fe 16 O 27 nanoparticles. → Flake ferrite particles have good static magnetic properties.→ Flake ferrites are a kind lightweight broad band microwave absorber.

Fabrication and electromagnetic properties of flake ferrite particles based on diatomite

Energy Technology Data Exchange (ETDEWEB)

Zhang Deyuan [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China); Zhang Wenqiang, E-mail: zwqzwqzwqzwq@126.com [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China); Cai Jun, E-mail: jun_cai@buaa.edu.cn [Bionic and Micro/Nano/Bio Manufacturing Technology Research Center, Beihang University, Beijing 100191 (China)

2011-09-15

Hexagonal ferrite BaZn{sub 1.1}Co{sub 0.9}Fe{sub 16}O{sub 27} coated surfaces of diatomite flakes of low density were synthesized by a sol-gel method. The phase structures, morphologies, particle size and chemical compositions of the composites were characterized by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectroscopy. The results show that hexagonal ferrite coated diatomite flakes can be achieved, and that the coating consisted of BaZn{sub 1.1}Co{sub 0.9}Fe{sub 16}O{sub 27} nanoparticles. The vibranting sample magnetometer results reveal that the flake ferrite particles have static magnetic properties. The complex permeability and permittivity of the composites were measured in the frequency range of 1-18 GHz. The microwave absorption properties of these ferrite particles are discussed. The results indicate that the flake ferrites have the potential to be used as a lightweight broad band microwave absorber. - Highlights: > We synthesize the flake ferrite particles using diatomite as a template. > Flake ferrite particles' coating layers are constituted by BaZn{sub 1.1}Co{sub 0.9}Fe{sub 16}O{sub 27} nanoparticles. > Flake ferrite particles have good static magnetic properties. > Flake ferrites are a kind lightweight broad band microwave absorber.

Ferrite thin films: Synthesis, characterization and gas sensing properties towards LPG

Energy Technology Data Exchange (ETDEWEB)

Rao, Pratibha; Godbole, R.V. [Department of Physics, Abasaheb Garware College, Karve Road, Pune 411 004 (India); Phase, D.M. [UGC-DAE CSR Centre, Indore (India); Chikate, R.C. [Department of Chemistry, Abasaheb Garware College, Karve Road, Pune 411 004 (India); Bhagwat, Sunita, E-mail: smb.agc@gmail.com [Department of Physics, Abasaheb Garware College, Karve Road, Pune 411 004 (India)

2015-01-15

Nanocrystalline (Co, Cu, Ni, Zn) ferrite thin films have been deposited onto the Si (100) and alumina substrates by spray pyrolysis deposition technique. Respective metal chlorides and iron chloride were used as precursors. The structural properties of (Co, Cu, Ni, Zn) ferrite thin films were investigated by X-ray diffraction (XRD) technique which confirms polycrystalline nature and single phase spinel structure. The surface morphology was studied using scanning electron microscopy (SEM) which reveals spherical morphology for these films except NiFe{sub 2}O{sub 4} films that exhibit petal like structure. The optical transmittance and reflectance measurements were recorded using a double beam spectrophotometer. The optical studies reveal that the transition is direct band gap energy. The VSM analyzes reveal the predominant ferrimagnetic nature for CuFe{sub 2}O{sub 4} films. The gas sensing properties towards Liquid Petroleum Gas (LPG) revealed that ZnFe{sub 2}O{sub 4} films are sensitive at lower temperature while NiFe{sub 2}O{sub 4} films show steep rise at higher temperature. - Highlights: • (Co, Cu, Ni, Zn) ferrite thin films are synthesized by simple spray pyrolysis technique. • Homogenization of substituent within ferrite structure. • CuFe{sub 2}O{sub 4} film exhibits predominantly ferrimagnetic nature. • LPG sensing at lower temperature for ZnFe{sub 2}O{sub 4} film. • High sensitivity for NiFe{sub 2}O{sub 4} film at higher temperature due to defects created in the structure.

Key step in the synthesis of ultrafine strontium ferrite powders (SrFe{sub 12}O{sub 19}) by sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Nga, Tran Thi Viet, E-mail: vietnga@itims.edu.vn; Duong, Nguyen Phuc; Loan, To Thanh; Hien, Than Duc

2014-10-15

Highlights: • The variations in the properties of SrM powders, resulting from different parameter. • Appropriate pH, R{sub M} ratio, and T{sub ca} were adjusted to producing a single-phase nanosized SrM. • The average particle sizes were evenly distributed in the range of 80° nm to 100° nm. - Abstract: Submicron strontium hexaferrite (SrFe{sub 12}O{sub 19}) particles were synthesized using the sol–gel route. Magnetic properties and structure of strontium ferrite powders were studied at various ranges of calcination temperature (T{sub ca}) (750–900 °C), calcination time (3 min–2 h), Fe/Sr molar ratios (R{sub M}) (10.5–12), and pH (1–8). The resultant particles were investigated using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. At 750 °C, the Sr–M phase could be obtained for 3 min in air. However, single-phase Sr–M, which had stabilized magnetic properties, was obtained at T{sub ca} of 850 °C for 2 h. In solutions at pH 1, magnetic properties of the obtained sample at R{sub M} = 10.5 were found to be optimal with maximum saturation magnetization of 56 emu/g and intrinsic coercive force of 6.7 kOe.

Microstructural changes in NiFe_2O_4 ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

International Nuclear Information System (INIS)

Chauhan, Lalita; Sreenivas, K.; Bokolia, Renuka

2016-01-01

Structural properties of Nickel ferrite (NiFe_2O_4) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe_2O_4 powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe_2O_4 ceramics with a uniform microstructure and a large grain size.

Microstructural changes in NiFe2O4 ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

Science.gov (United States)

Chauhan, Lalita; Bokolia, Renuka; Sreenivas, K.

2016-05-01

Structural properties of Nickel ferrite (NiFe2O4) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe2O4 powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe2O4 ceramics with a uniform microstructure and a large grain size.

Structural parameters and resistive switching phenomenon study on Cd0.25Co0.75Fe2O4 ferrite thin film

International Nuclear Information System (INIS)

Chhaya, U.V.; Gadhvi, M.R.; Mistry, B.V.; Bhavsar, K.H.; Joshi, U.S.; Lakhani, V.K.; Modi, K.B.

2011-01-01

Cadmium substituted cobalt ferrite thin film with nominal composition Cd 0.25 Co 0.75 Fe 2 O 4 , has been grown on quartz substrate by chemical solution deposition and their structural and electrical properties have been investigated. Grazing incidence X-ray diffraction (XRD) confirmed single phase spine) structure with nanometer grain size. Atomic force microscopic analysis revealed uniform nano structured growth of about 70 nm average crystallite size. The XRD data have been used to determine the distribution of cations among the tetrahedral and octahedral sites of the spinel lattice and various structural parameters. The cation distribution determined from X-ray diffraction line intensity calculations revealed, 60% octahedral sites occupancy of Cd 2+ -ions in the composition. Four terminal I-V measurements show hysteretic curves, suggesting high resistance state (HRS) and low resistance state (LRS) in the film with polarity dependence. Maximum resistance ratio, R high /R low of 57% was observed at room temperature in the Ag/Cd 0.25 Co 0.75 Fe 2 O 4 /Ag planar structure. Observed resistance switching is attributed to combined effects, viz., in the LRS, the major fraction of cadmium occupation and electron exchange between Fe 3+ and Fe 2+ at the B-sites, whereas the HRS shows Schottky-like conduction mechanism at the Ag/Cd 0.25 Co 0.75 Fe 2 O 4 interface. (author)

Structural, electrical, magnetic and dielectric properties of rare-earth substituted cobalt ferrites nanoparticles synthesized by the co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Nikumbh, A.K., E-mail: aknik@chem.unipune.ac.in; Pawar, R.A.; Nighot, D.V.; Gugale, G.S.; Sangale, M.D.; Khanvilkar, M.B.; Nagawade, A.V.

2014-04-15

Pure nanoparticles of the rare-earth substituted cobalt ferrites CoRE{sub x}Fe{sub 2−x}O{sub 4} (where RE=Nd, Sm and Gd and x=0.1 and 0.2) were prepared by the chemical co-precipitation method. X-ray diffraction, Transmission electron microscopy (TEM), d.c. electrical conductivity, Magnetic hysteresis and Thermal analysis are utilized in order to study the effect of variation in the rare-earth substitution and its impact on particle size, magnetic properties like M{sub S}, H{sub C} and Curie temperature. The phase identification of the materials by X-ray diffraction reveals the single-phase nature of the materials. The lattice parameter increased with rare-earth content for x≤0.2. The Transmission electron micrographs of Nd-, Sm- and Gd-substituted CoFe{sub 2}O{sub 4} exhibit the particle size 36.1 to 67.8 nm ranges. The data of temperature variation of the direct current electrical conductivity showed definite breaks, which corresponds to ferrimagnetic to paramagnetic transitions. The thermoelectric power for all compound are positive over the whole range of temperature. The dielectric constant decreases with frequency and rare-earth content for the prepared samples. The magnetic properties of rare-earth substituted cobalt ferrites showed a definite hysteresis loop at room temperature. The reduction of coercive force, saturation magnetization, ratio M{sub R}/M{sub S} and magnetic moments may be due to dilution of the magnetic interaction.

Circular patch microstrip array antenna on NiCoAl ferrite substrate in C-band

International Nuclear Information System (INIS)

Kumar, Dheeraj; Pourush, P.K.S.

2010-01-01

The problem of a 4x4 circular disc array antenna (CDAA) printed on a uniaxially anisotropic ferrite (NiCoAl) substrate is treated. The effect of anisotropy on the resonant frequency of the antenna is investigated. Radiation and scattering characteristics of the antenna with normal magnetic bias field to the direction of wave propagation in the plane of ferrite are described. Calculated result for the radar cross section (RCS) of antenna presented, and it is shown that the peaks in the RCS can be moved with respect to angle of incidence by changing the magnetic bias field. This effect offers a way of minimizing the radar visibility of microstrip antennas and arrays. Results are obtained from cavity modal solutions for a circular patch antenna at its TM 11 mode.

Effect of Co deposition on oxidation behavior and electrical properties of ferritic steel for solid oxide fuel cell interconnects

Energy Technology Data Exchange (ETDEWEB)

Kruk, A.; Adamczyk, A.; Gil, A. [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland); Kąc, S. [AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science, al. Mickiewicza 30, 30-059 Krakow (Poland); Dąbek, J.; Ziąbka, M. [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland); Brylewski, T., E-mail: brylew@agh.edu.pl [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, al. Mickiewicza 30, 30-059 Krakow (Poland)

2015-09-01

In this work, a Co layer deposited on DIN 50049 steel by means of pulsed laser deposition was applied for the protection of solid oxide fuel cell (SOFC) interconnects operating on the cathode side. The coated and uncoated steel samples were oxidized in air at 1073 K for 500 h, and their microstructures as well as electrical resistances were evaluated using X-ray diffraction, atomic force microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and the 2-probe 4-point direct current method. It was demonstrated that the Co coating had reduced the oxidation rate of the steel by nearly a half. The area-specific resistance value of the coated steel was 5 × 10{sup −6} Ω·m{sup 2}, which was significantly lower than that of bare steel after 350 h of oxidation at 1073 K. Cr vaporization tests showed that the Co coating was efficient at blocking the outward diffusion of Cr. The obtained results prove that steel coated with a thin film of cobalt was suitable for use as metallic interconnect material in SOFCs operating at intermediate temperatures. - Highlights: • Co layer was deposited on ferritic steel by means of pulsed laser deposition. • Coated and bare ferritic steel samples were exposed to air at 1073 K for 500 h. • Scale growth rate on bare steel is higher than that on coated steel. • Electrical resistance for oxidized coated steel was lower than for bare steel. • Co-coated steel effectively reduced the formation of volatile Cr species.

Cation distributions on rapidly solidified cobalt ferrite

Science.gov (United States)

De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

1990-01-01

The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

Synthesis, structure and electromagnetic properties of Mn–Zn ferrite by sol–gel combustion technique

International Nuclear Information System (INIS)

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2014-01-01

The electromagnetic absorbing behaviors of a thin coating fabricated by mixing Mn–Zn ferrite with epoxy resin (EP) were studied. The spinel ferrites Mn 1−x Zn x Fe 2 O 4 (x=0.2, 0.5 and 0.8) were synthesized with citrate acid as complex agent by sol–gel combustion method. The microstructure and surface morphology of Mn–Zn ferrite powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permittivity and complex permeability of the fabricated ferrite/EP composites were investigated in terms of their contributions to the absorbing properties in the low frequency (10 MHz to 1 GHz). The microwave absorption of the prepared ferrite/EP composites could be tailored by matching the dielectric loss and magnetic loss and by controlling the doped metal ratio. The composites with the ferrite composition x=0.2 are found to show higher reflection loss compared with the composites with other compositions. It is proposed that the prepared composites can potentially be applied in electromagnetic microwave absorbing field. - Highlights: • We designed and synthesized Mn 1−x Zn x Fe 2 O 4 (x=0.2, 0.5 and 0.8), with citrate acid as complex agent by the sol–gel combustion method. • Citrate acid as the complex agent overcomes the aggregation of ferrite resulting in high purity and homogeneous particles. • We investigated the electromagnetic absorbing performance of a fabricated thin coating by introducing Mn–Zn ferrite into epoxy resin (EP). • The Mn 0.8 Zn 0.2 Fe 2 O 4 composite coatings could achieve the satisfactory absorbing value of −17 dB at 800 MHz. • The prepared composites can potentially be used for the application in electromagnetic microwave absorbing field

Crystal structures of new cuprates containing CO3 analyzed by the Rietveld method of neutron powder diffraction

International Nuclear Information System (INIS)

Miyazaki, Y.; Yamane, H.; Kajitani, T.; Hiraga, K.; Hirai, T.; Morii, Y.; Funahashi, S.

1993-01-01

New compounds containing CO 3 groups, Sr 2 CuO 2 (CO 3 ), (C 0.4 Cu 0.6 )Sr 2 (Y 0.86 Sr 0.14 )Cu 2 O 7 and (C 0.35 Cu 0.65 )Sr 2 (Y 0.73 Ce 0.27 ) 2 Cu 2 O 9 , were prepared as stable phases at 1273-1303 K in a flowing gas of O 2 -CO 2 . The crystal structures of these compounds were refined by means of the Rietveld analysis for neutron powder diffraction data collected using a high resolution powder diffractometer (HRPD) in the JRR-3M reactor hall of the Japan Atomic Energy Research Institute (JAERI). Positions of CO 3 groups were satisfactorily determined. The distances of C-O bonds in the CO 3 groups were around 1.3A and the O-C-O angles were almost equal to the ideal bond angle of 120deg. (author)

Evaluation of mechanically alloyed Cu-based powders as filler alloy for brazing tungsten to a reduced activation ferritic-martensitic steel

Science.gov (United States)

de Prado, J.; Sánchez, M.; Ureña, A.

2017-07-01

80Cu-20Ti powders were evaluated for their use as filler alloy for high temperature brazing of tungsten to a reduced activation ferritic/martensitic steel (Eurofer), and its application for the first wall of the DEMO fusion reactor. The use of alloyed powders has not been widely considered for brazing purposes and could improve the operational brazeability of the studied system due to its narrower melting range, determined by DTA analysis, which enhances the spreading capabilities of the filler. Ti contained in the filler composition acts as an activator element, reacting and forming several interfacial layers at the Eurofer-braze, which enhances the wettability properties and chemical interaction at the brazing interface. Brazing thermal cycle also activated the diffusion phenomena, which mainly affected to the Eurofer alloying elements causing in it a softening band of approximately 400 μm of thickness. However, this softening effect did not degrade the shear strength of the brazed joints (94 ± 23 MPa), because failure during testing was always located at the tungsten-braze interface.

Plasma sintering of ferritic steel reinforced with niobium carbide prepared by high energy milling

International Nuclear Information System (INIS)

Silva Junior, J.F. da; Almeida, E.O.; Gomes, U.U.; Alves Junior, C.; Messias, A.P.; Universidade Federal do Rio Grande do Norte

2010-01-01

Plasma is an ionized gas where ions are accelerated from anode to cathode surface, where the sample is placed. There are a lot of collisions on cathode surface by ions heating and sintering the sample. High energy milling (HEM) is often used to produce composite particles to be used on powder metallurgy. These particles can exhibit fine particles and high phase dispersion. This present work aim to study ferritic steels reinforced with 3%NbC prepared by HEM and sintered on plasma furnace. Ferritic steel and NbC powders were milled during 5 hours and characterized by SEM, XRD and laser scattering. Then, these composite powders were compacted in a cylindrical steel die and then sintered in a plasma furnace. Vickers microhardness tests and SEM and XRD analysis were performed on sintered samples. (author)

Thermal solid-state Z/E isomerization of 2-alkylidene-4-oxothiazolidines: effects of non-covalent interactions

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ZDRAVKO DŽAMBASKI

2011-03-01

Full Text Available Configurational isomerization of stereo-defined 5-substituted and unsubstituted 2-alkylidene-4-oxothiazolidines (1 in the solid state, giving the Z/E mixtures in various ratios, was investigated by 1H-NMR spectroscopy, X-ray powder crystallography and differential scanning calorimetry (DSC. The Z/E composition can be rationalized in terms of non-covalent interactions, involving intermolecular and intramolecular hydrogen bonding and directional non-bonded 1,5-type S×××O interactions. X-Ray powder crystallography, using selected crystalline (Z-4-oxothiazolidine substrates, revealed transformation to the amorphous state during the irreversible Z®E process. A correlation between previous results on the Z/E isomerization in solution and now in the solid state was established.

Effect of low cost iron oxide with Si additive on structural properties of Ni-Zn ferrite

International Nuclear Information System (INIS)

Ghazanfar, U.

2010-01-01

Mixed Ni-Zn ferrites (x = 0.66, 0.77, 0.88, 0.99) were prepared by double sintering ceramic method using locally available low cost Fe/sub 2/O/sub 3/ with 0.5% (by wt) of Si additive. The chemical phase analysis, carried out by X-ray powder diffraction method, confirms the major phase of Ni-Zn ferrite. Study of the effect of composition on structural properties of ferrite system revealed a decreasing trend of lattice parameters with increasing Ni content. X-ray density and mass density increase with increasing Ni content, which in turn decreases the porosity due to successive presence of Si in Fe/sub 2/O/sub 3/. This decrease in porosity along with chemical homogeneities, distribution of phases and grain formation were also observed in scanning electron micrographs. (author)

Nanocrystalline AL2 O2 powders produced by laser induced gas phase reactions

International Nuclear Information System (INIS)

Borsella, E.; Botti, S.; Martelli, S.; Zappa, G.; Giorgi, R.; Turt, S.

1993-01-01

Nanocrystalline Al 2 O 3 powders were successfully synthesized by a CO 2 laser-driven gas-phase reaction involving trimethylaluminium (Al(CH 3 ) 3 ) and nitrous-oxide (N 2 O). Ethylene (C 2 H 4 ) was added as gas sensitizer. The as-synthesized powder particles showed a considerable carbon contamination and an amorphous-like structure. After thermal treatment at 1200-1400 degrees C, the powder was transformed to hexagonal a-Al 2 O 3 with very low carbon contamination as confirmed by X-ray diffraction, X-ray photo-electron spectroscopy and chemical analysis. The calcinated powders resulted to be spherical single crystal nanoparticles with a mean size of 15-20 nm, as determined by X-ray diffraction, electron microscopy and B.E.T. specific surface measurements. The laser synthesized Al 2 O 3 particles are well suited dispersoids for intermetallic alloy technology

Thermal decomposition of barium ferrate(VI): Mechanism and formation of FeIV intermediate and nanocrystalline Fe2O3 and ferrite

International Nuclear Information System (INIS)

Machala, Libor; Sharma, Virender K.; Kuzmann, Ernö; Homonnay, Zoltán; Filip, Jan; Kralchevska, Radina P.

2016-01-01

Simple high-valent iron-oxo species, ferrate(VI) (Fe VI O 4 2− , Fe(VI)) has applications in energy storage, organic synthesis, and water purification. Of the various salts of Fe(VI), barium ferrate(VI) (BaFeO 4 ) has also a great potential as a battery material. This paper presents the thermal decomposition of BaFeO 4 in static air and nitrogen atmosphere, monitored by combination of thermal analysis, Mössbauer spectroscopy, X-ray powder diffraction, and electron-microscopic techniques. The formation of Fe IV species in the form of BaFeO 3 was found to be the primary decomposition product of BaFeO 4 at temperature around 190 °C under both studied atmospheres. BaFeO 3 was unstable in air reacting with CO 2 to form barium carbonate and speromagnetic amorphous iron(III) oxide nanoparticles (<5 nm). Above 600 °C, a solid state reaction between BaCO 3 and Fe 2 O 3 occurred, leading to the formation of barium ferrite nanoparticles, BaFe 2 O 4 (20–100 nm). - Highlights: • We explained the mechanism of thermal decomposition of barium ferrate(VI). • We confirmed the formation of Fe(IV) intermediate phase during the decomposition. • The mechanism of the decomposition is influenced by a presence of carbon dioxide.

Electromagnetic interference shielding and microwave absorption properties of cobalt ferrite CoFe2O4/polyaniline composite

Science.gov (United States)

Ismail, Mukhils M.; Rafeeq, Sewench N.; Sulaiman, Jameel M. A.; Mandal, Avinandan

2018-05-01

Improvement of microwave-absorbing materials (MAMs) is the most important research area in various applications, such as in communication, radiation medical exposure, electronic warfare, air defense, and different civilian applications. Conducting polymer, polyaniline doped with para toluene sulphonic acid (PANI-PTSA) as well as cobalt ferrite (CoFe2O4) is synthesized by sol-gel method and intensely blends in different ratios. The characterization of the composite materials, CoFe2O4/PANI-PTSA (CFP1, CFP2, CFP3 and CFP4), was performed by X-ray diffraction (XRD), atomic force microscopy (AFM) and vibrating sample magnetometry (VSM). The microwave-absorbing properties' reflection loss (dB) and important parameters, such as complex relative permittivity ( ɛ r '- jɛ r ″) and complex relative permeability ( µ r '- jµ r ″) were measured in different microwave frequencies in the X-band (8.2-12.4 GHz) region. The composite material CFP3 showed a wider absorption frequency range and maximum reflection loss of - 28.4 dB (99.8% power absorption) at 8.1 GHz and - 9.6 dB (> 90% power absorption) at 11.2 GHz, and so the composite can be used as a microwave absorber; however, it can be more suitable for application in daily life for making cell phones above 9 GHz. Also the results showed that the thicker composites like CFP3 (4 mm) exhibit obviously better EMI SE as compared with the thinner ones (0.19, 0.19, 0.3 mm); this may be related to the low transmission of the EM wave from the composites.

Structure and magnetic properties of granular NiZn-ferrite - SiO2

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Albuquerque Adriana Silva de

1999-01-01

Full Text Available Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthesized by sol-gel processing. Samples with ferrite volumetric fraction x ranging from 6% to 78% were prepared, and characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Our results show the formation of pure stoichiometric NiZn-ferrite in the SiO2 matrix for x < 34%. Above these fraction, our samples presented also small amounts of Fe2O3. Mössbauer spectroscopy revealed the superparamagnetic behaviour of the ferrimagnetic NiZn-ferrite nanoparticles. The combination of different ferrite concentration and heat treatments allowed the obtaintion of samples with saturation magnetization between 1.3 and 68 emu/g and coercivity ranging from 0 to 123 Oe, value which is two orders of magnitude higher than the coercivity of bulk NiZn-ferrite.

Host composition dependent tunable multicolor emission in the single-phase Ba2(Ln(1-z)Tb(z))(BO3)2Cl:Eu phosphors.

Science.gov (United States)

Xia, Zhiguo; Zhuang, Jiaqing; Meijerink, Andries; Jing, Xiping

2013-05-14

A new strategy based on the host composition design has been adopted to obtain efficient color-tunable emission from Ba2Ln(0.97-z)Tb(z)(BO3)2Cl:0.03Eu (Ln = Y, Gd and Lu, z = 0-0.97) phosphors. This study reveals that the single-phase Ba2Ln(1-z)Tb(z)(BO3)2Cl compounds can be applied to use allowed Eu(2+) absorption transitions to sensitize Eu(3+) emission via the energy transfer Eu(2+) → (Tb(3+))n → Eu(3+). The powder X-ray diffraction (XRD) and Rietveld refinement analysis shows single-phase Ba2Ln(1-z)Tb(z)(BO3)2Cl. As-prepared Ba2Ln(0.97-z)Tb(z)(BO3)2Cl:0.03Eu phosphors show intense green, yellow, orange and red emission under 377 nm near ultraviolet (n-UV) excitation due to a variation in the relative intensities of the Eu(2+), Tb(3+) and Eu(3+) emission depending on the Tb content (z) in the host composition, allowing color tuning. The variation in emission color is explained by energy transfer and has been investigated by photoluminescence and lifetime measurements and is further characterized by the Commission Internationale de l'éclairage (CIE) chromaticity indexes. The quantum efficiencies of the phosphors are high, up to 74%, and show good thermal stabilities up to 150 °C. This investigation demonstrates the possibility to sensitize Eu(3+) line emission by Eu(2+)via energy migration over Tb(3+) resulting in efficient color tunable phosphors which are promising for use in solid-state white light-emitting diodes (w-LEDs).

Magnetic loss, permeability, and anisotropy compensation in CoO-doped Mn-Zn ferrites

Science.gov (United States)

Beatrice, Cinzia; Dobák, Samuel; Tsakaloudi, Vasiliki; Ragusa, Carlo; Fiorillo, Fausto; Martino, Luca; Zaspalis, Vassilis

2018-04-01

Mn-Zn ferrite samples prepared by conventional solid state reaction method and sintering at 1325 °C were Co-enriched by addition of CoO up to 6000 ppm and characterized versus frequency (DC - 1GHz), peak polarization (2 mT - 200 mT), and temperature (23 °C - 120 °C). The magnetic losses at room temperature are observed to pass through a deep minimum value around 4000 ppm CoO at all polarizations values. This trend is smoothed out either by approaching the MHz range or by increasing the temperature. Conversely, the initial permeability attains its maximum value around the same CoO content, while showing moderate monotonical decrease with increasing CoO at the typical working temperatures of 80 - 100 °C. The energy losses, measured by a combination of fluxmetric and transmission line methods, are affected by the eddy currents, on the conventional 5 mm thick ring samples, only beyond a few MHz. Their assessment relies on the separation of rotational and domain wall processes, which can be done by analysis of the complex permeability and its frequency behavior. This permits one, in particular, to calculate the magnetic anisotropy and its dependence on CoO content and temperature and bring to light its decomposition into the host lattice and Co2+ temperature dependent contributions. The temperature and doping dependence of initial permeability and magnetic losses can in this way be qualitatively justified, without invoking the passage through zero value of the effective anisotropy constant upon doping.

Mössbauer and magnetic studies of nanocrystalline zinc ferrites synthesized by microwave combustion method

Energy Technology Data Exchange (ETDEWEB)

Mahmoud, Mohamed, E-mail: mamdouh-2000-2000@yahoo.com [Assiut University, Department of Physics (Egypt); Hassan, Azza Mohamed [Asuite University, Physics Department, Faculty of Sciences (Egypt); Ahmed, Mamdouh Abdel aal [Al Azhar University, Physics Department, Faculty of Science (Egypt); Zhu, Kaixin; Ganeshraja, Ayyakannu Sundaram; Wang, Junhu, E-mail: Wangjh@dicp.ac.cn [Chinese Academy Sciences, Mössbauer Effect Data Center & Laboratory of Catalysts and New Materials for Aerospace, Dalian Institute of Chemical Physics (China)

2016-12-15

Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mössbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 {sup ∘}C and 900 {sup ∘}C. Both the saturation magnetization (Ms) and the remnant magnetization (Mr) were found to be highly dependent upon the annealing temperature. Mössbauer studies show magnetic ordering in the powder even at room temperature. The Mössbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite.

Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

Science.gov (United States)

Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

2018-04-01

Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

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Torres C.

2013-01-01

Full Text Available Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer’s formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

Synthesis, characterization and gas sensitivity investigation of Ni0.5Zn0.5Fe2O4 nanoparticles

Science.gov (United States)

Ebrahimi, Hamid Reza; Parish, Mohammad; Amiri, Gholam Reza; Bahraminejad, Behzad; Fatahian, Soheil

2016-09-01

Nickel zinc ferrite nanoparticles with diameters less than 20 nm were synthesized by co-precipitation method. The synthesized nanoparticles were annealed at 500 °C. Two types of samples (powder and disk) were prepared. The disk sample was prepared by pressing the powder sample. Magnetic and structural properties of the products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and alternating gradient-force magnetometer (AGFM). The X-ray analysis shows that the formation of the synthesized nickel zinc ferrite is spinell. The average crystalline size for nickel zinc ferrite powder was found around 19 nm (calculated by Debye-Scherer formula).The formation, size and the uniformity of the samples were determined by TEM. It was found that the size of nanoparticles should be around 18 nm from the SEM image. AGFM diagrams shows that the magnetization of the powder sample at the 9 kOe is 21.5 emu/g that of disk sample is 33 emu/g. Therefore, the magnetization was increased by pressing the nickel zinc ferrite nanoparticles. Sensor sensitivity of this disk ferrite is investigated in an isolated box. For this purpose, the samples are injected to this box and six gases (ethanol, methanol, chloroform, acetonitrile, acetone and methane) are exposed to the ferrite by a mechanical gate. The acetonitrile had the best sensitivity performance.

Novel synthesis of Ni-ferrite (NiFe2O4) electrode material for supercapacitor applications

International Nuclear Information System (INIS)

Venkatachalam, V.; Jayavel, R.

2015-01-01

Novel nanocrystalline NiFe 2 O 4 has been synthesized through combustion route using citric acid as a fuel. Phase of the synthesized material was analyzed using powder X-ray diffraction. The XRD study revealed the formation of spinel phase cubic NiFe 2 O 4 with high crystallinity. The average crystallite size of NiFe 2 O 4 nanomaterial was calculated from scherrer equation. The electrochemical properties were realized by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrode material shows a maximum specific capacitance of 454 F/g with pseudocapacitive behavior. High capacitance retention of electrode material over 1000 continuous charging-discharging cycles suggests its excellent electrochemical stability. The results revealed that the nickel ferrite electrode is a potential candidate for energy storage applications in supercapacitor

Solubility limits in Mn–Mg ferrites system under hydrothermal conditions

Energy Technology Data Exchange (ETDEWEB)

Hemeda, O.M., E-mail: omhemeda@yahoo.co.uk [Physics Department, Faculty of Science, Tanta University, Tanta (Egypt); Mostafa, N.Y. [Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 41522 (Egypt); Faculty of Science, Taif University, PO Box 888, Al-Haweiah, Taif (Saudi Arabia); Abd Elkader, O.H. [Electron Microscope and Thin Films Department, National Research Center, Dokki 12622, Cairo (Egypt); Electron Microscope Unit, Zoology Department, King Saud University, Riyadh 11451 (Saudi Arabia); Ahmed, M.A. [Physics Department, Faculty of Science, Al Azhar University, Nasr City, Cairo (Egypt)

2014-09-01

In the present investigation, we successfully synthesized a pure MnFe{sub 2}O{sub 4} ferrite by the hydrothermal method. Moreover, the effect of Mg ion content on the formation of Mn{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} particles (with x varying from 0.1 to 1.0) was also investigated using XRD, SEM, TEM and Mossbauer Spectroscopy. Phases formed in the system Mn{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4}; 0.0≤x≤1.0 were investigated under hydrothermal conditions at 453 K.The produced phases were characterized by X-ray diffraction, Scanning, transmission microscopy and Mossbauer spectroscopy. The information of composition, cation distribution in the spinel structure and the particle size of the products were obtained. The spinel ferrites; Mn{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} were formed in the range 0.0≤x≤0.3. However, sample with x>0.3 showed semi-crystalline magnesium hydroxide (Mg(OH){sub 2}) and hematite (Fe{sub 2}O{sub 3}) beside the ferrite phase. For x=1.0, only magnesium hydroxide and hematite are formed without any ferrites. Particles of uniform size around 10–20 nm were obtained in the spinel structure of Mn{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} with x=0.0 and 0.1. The corresponding average crystallite size for each sample was 40.3 nm and 39.2 nm respectively. In addition, the Mossbauer spectra were analyzed into two subspectra, one for the tetrahedral A-site and the other for the octahedral B-site. The Mossbauer parameters were determined and discussed for the studied system. The cation distribution was estimated from the analysis of the Mossbauer spectra as well as the X-ray diffraction patterns. The results showed that Mg ions occupy mainly B-site while both Mn and Fe ions are distributed between A- and B-sites. - Highlights: • Mossbauer characterization of Mg–Mn ferrite prepared by hydrothermal route. • X-ray powder diffraction analysis of Mg–Mn ferrite prepared by hydrothermal route. • Solubility limit of MgMn ferrite under

Influences of Ti4+ and Mg2+ substitutions on the properties of lithium ferrites

International Nuclear Information System (INIS)

Su Hua; Zhang Huaiwu; Tang Xiaoli; Liu Baoyuan

2009-01-01

The Ti 4+ and Mg 2+ co-substituted lithium ferrites with different compositions of Zn 0.1 Li 0.45 Mn 0.1 Fe 2.35-2x (TiMg) x O 4 (x=0.0-0.5) were prepared by the ceramic standard processing. The magnetic properties and microstructure of the samples were investigated. A single phase spinel structure was confirmed by XRD in substituting range. Sintering densities continuously decreased with the increase at x value, which was attributed to the fact that the heavier Fe 3+ ions were replaced by the relatively lighter Ti 4+ and Mg 2+ ions. However, relative density of the samples had no obvious relationship with the substituting value. Saturation magnetization continuously decreased with x value, which was attributed to the decrease of resultant magnetic moment between A and B sub-lattice. Remanence decreased monotonously with x value due to the decrease of saturation magnetization and magnetocrystalline anisotropy constant. But the effect of Ti 4+ and Mg 2+ substitutions on the Br/Bs ratio values was not obvious. Coercive force was mainly determined by the microstructure and magnetocrystalline anisotropy constant of the ferrites. In this research, with the increase of Ti 4+ and Mg 2+ substitutions, the advantageous influence by the decrease of magnetocrystalline anisotropy constant was more significant than the disadvantageous influence caused by the increase of closed pores. As a result, coercive force of the ferrites also decreased monotonously with the increase at x value.

Structural characterization of ferrite nanoparticles and composite materials using synchrotron radiation

International Nuclear Information System (INIS)

Albuquerque, A.S.; Macedo, W.A.A.; Plivelic, T.; Torriani, I.L.; Jimenez, J.A.L.; Saitovich, E.B.

2001-01-01

During the last decade nanocrystalline magnetic materials have been widely studied due to the multiple technological applications. Amongst the magnetic materials of major technological interest are the soft magnetic ferrites and the granular solids formed by ferrites dispersed in non-magnetic matrices. It is a well known fact that the magnetic properties of these materials, such as coercivity, magnetic saturation and magnetization, depend on the shape, size and size distribution of the nanoparticles. For this reason, the general purpose of this work was to obtain structural information on ferrite nanoparticles (NiFe 2 O 4 and NiZnFe 2 O 4 ) and granular solids obtained by dispersion of these particles in non magnetic matrices, like SiO 2 and SnO 2 . The ferrite samples were prepared by co-precipitation and heat treated between 300 and 600 deg. C at the Applied Physics Laboratory of tile CDTN. The granular solids, with 30% in volume concentration of ferrite, were obtained by mechanical alloying with milling times (t m ) varying between 1.25 and 10 h, at the CBPF

Microstructural changes in NiFe{sub 2}O{sub 4} ceramics prepared with powders derived from different fuels in sol-gel auto-combustion technique

Energy Technology Data Exchange (ETDEWEB)

Chauhan, Lalita, E-mail: chauhan.lalita5@gmail.com; Sreenivas, K. [Department of Physics & Astrophysics, University of Delhi, Delhi-110007 (India); Bokolia, Renuka

2016-05-23

Structural properties of Nickel ferrite (NiFe{sub 2}O{sub 4}) ceramics prepared from powders derived from sol gel auto-combustion method using different fuels (citric acid, glycine and Dl-alanine) are compared. Changes in the structural properties at different sintering temperatures are investigated. X-ray diffraction (XRD) confirms the formation of single phase material with cubic structure. Ceramics prepared using the different powders obtained from different fuels show that that there are no significant changes in lattice parameters. However increasing sintering temperatures show significant improvement in density and grain size. The DL-alanine fuel is found to be the most effective fuel for producing NIFe{sub 2}O{sub 4} powders by the sol-gel auto combustion method and yields highly crystalline powders in the as-burnt stage itself at a low temperature (80 °C). Subsequent use of the powders in ceramic manufacturing produces dense NiFe{sub 2}O{sub 4} ceramics with a uniform microstructure and a large grain size.

X-ray diffraction and Moessbauer studies on superparamagnetic nickel ferrite (NiFe{sub 2}O{sub 4}) obtained by the proteic sol–gel method

Energy Technology Data Exchange (ETDEWEB)

Nogueira, N.A.S. [Departamento de Engenharia Metalúrgica e de Materiais, Centro de Tecnologia, Campus do Pici, Universidade Federal do Ceará – UFC, 60455-760 Fortaleza, CE (Brazil); Utuni, V.H.S.; Silva, Y.C. [Departamento de Física, Universidade Federal do Ceará – UFC, Campus do Pici, 60440-970 Fortaleza, CE (Brazil); Kiyohara, P.K. [Instituto de Física, Universidade de São Paulo – USP, 05315-970 São Paulo, SP (Brazil); Vasconcelos, I.F. [Departamento de Engenharia Metalúrgica e de Materiais, Centro de Tecnologia, Campus do Pici, Universidade Federal do Ceará – UFC, 60455-760 Fortaleza, CE (Brazil); Miranda, M.A.R., E-mail: marcus.a.r.miranda@gmail.com [Departamento de Física, Universidade Federal do Ceará – UFC, Campus do Pici, 60440-970 Fortaleza, CE (Brazil); Sasaki, J.M. [Departamento de Física, Universidade Federal do Ceará – UFC, Campus do Pici, 60440-970 Fortaleza, CE (Brazil)

2015-08-01

Nickel ferrite (NiFe{sub 2}O{sub 4}) nanoparticles were synthesized by the proteic sol–gel method at synthesis temperature of 250 °C, 300 °C and 400 °C, with the objective of obtaining superparamagnetic nanoparticles. Thermogravimetric analysis (TGA) and temperature-programed oxidation (TPO) presented peaks around 290 °C indicating that nickel ferrite was forming at this temperature. X-ray powder diffraction (XRPD) confirmed that the polycrystalline sample was single phased NiFe{sub 2}O{sub 4} with space group Fd3m. Scherrer equation applied to the diffraction patterns and transmission electron microscopy (TEM) images showed that the size of the nanoparticles ranged from 9 nm to 13 nm. TEM images also revealed that the nanoparticles were agglomerated, which was supported by the low values of surface area provided by the Brunauer-Emmet-Teller (BET) method. Moessbauer spectroscopy presented spectra composed of a superposition of three components: a sextet, a doublet and a broad singlet pattern. The sample synthetized at 300 °C had the most pronounced doublet pattern characteristic of superparamagnetic nanoparticles. In conclusion, this method was partially successful in obtaining superparamagnetic nickel ferrite nanoparticles, in which the synthetized samples were a mixture of nanoparticles with blocking temperature above and below room temperature. Magnetization curves revealed a small hysteresis, supporting the Moessbauer results. The sample with the higher concentration of superparamagnetic nanoparticles being the one synthetized at 300 °C. - Highlights: • Superparamagnetic nickel ferrite nanoparticles were grown by the proteic sol–gel method. • The proteic sol–gel method provided superparamagnetic nickel ferrite nanoparticles with sizes in the range of 9–13 nm. • Nickel ferrite nanoparticles were prepared at temperatures as low as 250 °C. • The nickel ferrite nanoparticles were studied by x-ray diffraction and Moessbauer.

Utilization of CO2 fixating bacterium Actinobacillus succinogenes 130Z for simultaneous biogas upgrading and bio-succinic acid production

DEFF Research Database (Denmark)

Gunnarsson, Ingólfur Bragi; Alvarado-Morales, Merlin; Angelidaki, Irini

2014-01-01

Biogas is an attractive renewable energy carrier. However, it contains CO2 which limits certain applications of biogas. Here we report a novel approach for removing CO2 from biogas and capturing it as a biochemical through a biological process. This approach entails converting CO2 into bio...... and titre, CO2 consumption rate and CH4 purity. When using biogas as the only CO2 source at 140 kPa, the CO2 consumption rate corresponded to 2.59 L CO2 L-1 d-1 with a final succinic acid titre of 14.4 g L-1. Under this pressure condition the highest succinic acid yield and biogas quality reached......-succinic acid using the bacterial strain Actinobacillus succinogenes 130Z, and simultaneously producing high purity CH4 (>95%). Results showed that when pressure during fermentation was increased from 101.325 to 140 kPa, higher CO2 solubility was achieved, thereby positively affecting final succinic acid yield...

Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

Energy Technology Data Exchange (ETDEWEB)

Wang, Sea-Fue, E-mail: sfwang@ntut.edu.tw; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

2015-11-15

In this study, the effects of grain size and the addition of CaCO{sub 3} on the magnetic and mechanical properties of Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO{sub 3} densified the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics at 1075 °C. In the pure Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO{sub 3} content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe{sub 2}CaO{sub 4} was observed, together with the disappearance of the second phase CuO. The grain size of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO{sub 3} content increased from 0 to 5 wt%. Initially rising to 807 after CaCO{sub 3} addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO{sub 3} content increased. The bending strength grew linearly with the CaCO{sub 3} content and reached twice the value for the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic with an addition of 5.0 wt% CaCO{sub 3}. The initial permeability of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic decreased substantially from 402 to 103 as the addition of CaCO{sub 3} in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic was maximized at 95 for 1.0 wt% CaCO{sub 3} addition. - Highlights: • Effects of grain size and CaCO{sub 3} on the properties of NiCuZn ferrite were studied. • Bending strength increased with grain size of the ferrite but not in the hardness. • Bending strength reached a twice value for

In-situ formation of complex oxide precipitates during processing of oxide dispersion strengthened ferritic steels

International Nuclear Information System (INIS)

Jayasankar, K.; Pandey, Abhishek; Mishra, B.K.; Das, Siddhartha

2016-01-01

Highlights: • Use of dual drive planetary ball mill for Bench scale (>1 kg) production. • X-ray diffraction and TEM were used to study transformations during sintering. • HIPped and rolled samples with nearly 99% density successfully produced. - Abstract: In fusion and fission reactor material development, ODS alloys are the most suitable candidate materials due to its high temperature creep properties and irradiation resistance properties. This paper describes the preparation of oxide dispersion strengthened alloy powder in large quantity (>1 kg batch) in dual drive planetary ball mill using pre-alloyed ferrtic steel powder with nano sized Y_2O_3. The consolidation of the powders was carried out in hot isostatic press (HIP) followed by hot rolling. 99% of the theoretical density was achieved by this method. The vickers hardness values of pressed and rolled samples were in the range of 380 ± 2HV and 719 ± 2HV, respectively. Samples were further investigated using X-ray diffraction particle size analyzer and electron microscope. Initial increase in particle size with milling was observed showing flattening of the particle. It was found that 5 h of milling time is sufficient to reduce the particle size to achieve the desired size. Transmission electron microscopy analysis of milled ODS steel powder revealed a uniform distribution of combustion synthesized nano-Y_2O_3 in ferritic steel matrix after a milling time of 5 h. Preliminary results demonstrated suitability of dual drive planetary ball mill for mass production of alloy within a short time due to various kinds of forces acting at a time during milling process. Fine monoclinic Y_2Si_2O_7 precipitates were also observed in the steel. This study explains the particle characteristics of nano Y_2O_3 dispersed ODS powder and formation of nano clusters in ODS ferritic alloy.

Chitosan-coated nickel-ferrite nanoparticles as contrast agents in magnetic resonance imaging

International Nuclear Information System (INIS)

Ahmad, Tanveer; Bae, Hongsub; Iqbal, Yousaf; Rhee, Ilsu; Hong, Sungwook; Chang, Yongmin; Lee, Jaejun; Sohn, Derac

2015-01-01

We report evidence for the possible application of chitosan-coated nickel-ferrite (NiFe 2 O 4 ) nanoparticles as both T 1 and T 2 contrast agents in magnetic resonance imaging (MRI). The coating of nickel-ferrite nanoparticles with chitosan was performed simultaneously with the synthesis of the nickel-ferrite nanoparticles by a chemical co-precipitation method. The coated nanoparticles were cylindrical in shape with an average length of 17 nm and an average width of 4.4 nm. The bonding of chitosan onto the ferrite nanoparticles was confirmed by Fourier transform infrared spectroscopy. The T 1 and T 2 relaxivities were 0.858±0.04 and 1.71±0.03 mM −1 s −1 , respectively. In animal experimentation, both a 25% signal enhancement in the T 1 -weighted mage and a 71% signal loss in the T 2 -weighted image were observed. This demonstrated that chitosan-coated nickel-ferrite nanoparticles are suitable as both T 1 and T 2 contrast agents in MRI. We note that the applicability of our nanoparticles as both T 1 and T 2 contrast agents is due to their cylindrical shape, which gives rise to both inner and outer sphere processes of nanoparticles. - Highlights: • Chitosan-coated nickel-ferrite (Ni-Fe 2 O 4 ) nanoparticles were synthesized in an aqueous system by chemical co-precipitation. • The characterization of bare and chitosan-coated nanoparticles were performed using various analytical tools, such as TEM, FTIR, XRD, and VMS. • We evaluated the coated particles as potential T 1 and T 2 contrast agents for MRI by measuring T 1 and T 2 relaxation times as a function of iron concentration. • Both T 1 and T 2 effects were also observed in animal experimentation

Structure investigations of ferromagnetic Co-Ni-Al alloys obtained by powder metallurgy.

Science.gov (United States)

Maziarz, W; Dutkiewicz, J; Lityńska-Dobrzyńska, L; Santamarta, R; Cesari, E

2010-03-01

Elemental powders of Co, Ni and Al in the proper amounts to obtain Co(35)Ni(40)Al(25) and Co(40)Ni(35)Al(25) nominal compositions were ball milled in a high-energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X-ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat-treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered gamma phase (gamma'), often appearing as twins, and a small amount of the L1(0) ordered martensite.

Magnetic Properties of Ni-Zn Ferrite Prepared with the Layered Precursor Method

International Nuclear Information System (INIS)

Zhou Xin; Hou Zhi-Ling; Li Feng; Qi Xin

2010-01-01

We prepare NiZnFe 2 O 4 soft magnetic ferrites with different molar ratios with the layered precursor method and investigate their magnetic properties. In the layered precursor, metal ions are scattered on the layer plate in a certain way on account of the effect of lowest lattice energy and lattice orientation. After high temperature calcinations, spinel ferrites with uniform structural component and single magnetic domain can be obtained, and the magnetic property is improved greatly. NiZnFe 2 O 4 ferrites prepared have the best specific saturation magnetization of 79.15 emu·g −1 , higher than that of 68 emu·g −1 prepared by the chemical co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. Meanwhile the coercivity of NiZnFe 2 O 4 ferrites prepared by layered precursor method is 14 kA·m −1 , lower than that of 50 emu·g −1 prepared by the co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Characterisation of Mn0.63Zn0.37Fe2O4 powders after intensive milling and subsequent thermal treatment

Directory of Open Access Journals (Sweden)

Labus Nebojša

2017-01-01

Full Text Available Commercial Mn-Zn powder (Mn0.63Zn0.37Fe2O4, 93 wt. % and Fe2O3 7 wt. % was milled 0.5, 1, 2 and 4 hours in a planetary ball mill. The goal was to observe intensive milling influences on oxidation and reduction processes that will happen during subsequent heating. Powders were characterized with XRD, SEM and particle seizer. Subsequent heating was monitored on TGA/DTA in an air atmosphere. After compaction of the milled powders, sintering was also performed in a dilatometric device. Sintered specimens were characterized micro structurally with SEM on a fresh breakage. Obtained differential TGA diagrams suggest intensive changes during prolonged milling of the oxidation kinetics on heating. Ferrite powders changed with milling as well as with second run heating were characterized to enable determination of the potentially best ratio of milling and heating to be applied to obtain the desired microstructure. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. OI172057 and Grant no. III45014

Structural, magnetic and gas sensing properties of nanosized copper ferrite powder synthesized by sol gel combustion technique

Energy Technology Data Exchange (ETDEWEB)

Sumangala, T.P.; Mahender, C. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Barnabe, A. [Université de Toulouse, Institut Carnot CIRIMAT – UMR CNRS-UPS-INP 5085, Université Paul Sabatier, Toulouse 31062 (France); Venkataramani, N. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Prasad, Shiva, E-mail: shiva.pd@gmail.com [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

2016-11-15

Stoichiometric nano sized copper ferrite particles were synthesized by sol gel combustion technique. They were then calcined at various temperatures ranging from 300–800 °C and were either furnace cooled or quenched in liquid nitrogen. A high magnetisation value of 48.2 emu/g signifying the cubic phase of copper ferrite, was obtained for sample quenched to liquid nitrogen temperature from 800 °C. The ethanol sensing response of the samples was studied and a maximum of 86% response was obtained for 500 ppm ethanol in the case of a furnace cooled sample calcined at 800 °C. The chemical sensing is seen to be correlated with the c/a ratio and is best in the case of tetragonal copper ferrite. - Highlights: • One of the first study on ethanol sensing of cubic copper ferrite. • In-situ High temperature XRD done shows phase transition from cubic to tetragonal. • A non-monotonic increase in magnetization was seen with calcination temperature. • A response of 86% was obtained towards 500 ppm ethanol. • Tried to correlate sensing response and ion content in spinel structure.

The Effect Of Coupling Agent On Composite Magnet Characteristic Based On Hexa ferrite (Sr M/Ba M) With Polyester And Epoxy Binder

International Nuclear Information System (INIS)

Sudirman; Ridwan; Mujamilah; Karo Karo, Aloma; Handayani, Ari; Rukihati

2004-01-01

Magnetic composites are mixtures of hexa ferrite powder and non magnetic materials such as polymers as binders. These composites have been investigated because they are light, elastic, and cheap. In this study thermoset polymer (epoxy and polyester) were used as binders. Inside study of coupling agent added effect on mechanical properties, hardness and microstructure. The composites were prepared by mixture thermoset polymer epoxy or polyester with hexa ferrite powder Sr M (SrFe 12 O 19 ) or Ba M (BaFe 12 O 19 ) with volume fraction of 40,50 and 60 % v/v, coupling agent of the Tetra Isopropyl Titanate in the amount of 5 ml or 10 ml are added before mix turing of the thermoset polymer epoxy or polyester with hexa ferrite powder. The resulting composite were characterized mechanically (tensile strength), hardness and microstructure test. The results showed that the tensile strength and hardness of the composite magnet were increased by increasing the composition of magnetic powder, either Sr M or Ba M, it caused by microstructure of particle Sr M magnetic powder 1.6 μm in the form splinter, where as the Ba M magnetic powder 1,2 μm in nodular form. Thermoset polymer epoxy as binder have tensile strength and hardness is bigger than composite magnet based on polyester, either Sr M or Ba M. The addition of coupling agent is very influenced on the tensile strength and hardness composite magnet, the more coupling magnet addition causes the more tensile strength and hardness of the composite magnet