Proceedings of the Second International Congress on Recent Developments in Air- and Structure-Borne Sound and Vibration (2nd) Held in Auburn University, Alabama on 4-6 March 1992. Volume 2

DTIC Science & Technology

1992-03-06

elastic data (uncorrected) on Lithium- Zinc and Lithium- Cadmium ferrites Ferrite Bulk X-ray Per- V Vs E n Composition density density cen- 0 3K -3 10 3 K...weight with increasing zinc and cadmium contents. In the case of Li-Cd ferrites, the values of VI/P , V s /P Vm and eD are also increases continuously...585 Wu Ounli, Nanyang Technololical University, Singapore RECIPROCITY METHOD FOR QUANTIFICATION OF AIRBORNE SOUND TRANSFER FROM MACHINERY

Effects of C and Si on strain aging of strain-based API X60 pipeline steels

NASA Astrophysics Data System (ADS)

Sung, Hyo Kyung; Lee, Dong Ho; Lee, Sunghak; Lee, Byeong-Joo; Hong, Seung-Pyo; Kim, Young-Woon; Yoo, Jang Yong; Hwang, Byoungchul; Shin, Sang Yong

2017-05-01

Four types of strain-based API X60 pipeline steels were fabricated by varying the C and Si contents, and the effects of C and Si on strain aging were investigated. The 0.05 wt% C steels consisted mainly of polygonal ferrite (PF), whereas the 0.08 wt% C steels consisted of acicular ferrite (AF). The volume fraction of AF increased with increasing C content because C is an austenite stabilizer element. The volume fractions of bainitic ferrite (BF) of the 0.15 wt% Si steels were higher than those of the 0.25 wt% Si steels, whereas the volume fractions of the secondary phases were lower. From the tensile properties before and after the aging process of the strainbased API X60 pipeline steels, the yield strength increased and the uniform and total elongation decreased, which is the strain aging effect. The strain aging effect in the strain-based API X60 pipeline steels was minimized when the volume fraction of AF was increased and secondary phases were distributed uniformly. On the other hand, an excessively high C content formed fine precipitates, and the strain aging effect occurred because of the interactions among dislocations and fine precipitates.

C-Curves for Lengthening of Widmanstätten and Bainitic Ferrite

NASA Astrophysics Data System (ADS)

Yin, Jiaqing; Leach, Lindsay; Hillert, Mats; Borgenstam, Annika

2017-09-01

Widmanstätten ferrite and bainitic ferrite are both acicular and their lengthening rate in binary Fe-C alloys and low-alloyed steels under isothermal conditions is studied by searching the literature and through new measurements. As a function of temperature, the lengthening rate can be represented by a common curve for both kinds of acicular ferrite in contrast to the separate C-curves often presented in time-temperature-transformation (TTT) diagrams. The curves for Fe-C alloys with low carbon content show no obvious decrease in rate at low temperatures down to 623 K (350 °C). For alloys with higher carbon content, the expected decrease of rate as a function of temperature below a nose was observed. An attempt to explain the absence of a nose for low carbon contents by an increasing deviation from local equilibrium at high growth rates is presented. This explanation is based on a simple kinetic model, which predicts that the growth rates for Fe-C alloys with less than 0.3 mass pct carbon are high enough at low temperatures to make the carbon pileup, in front of the advancing tip of a ferrite plate, shrink below atomic dimensions, starting at about 600 K (323 °C).

High temperature dissolution of chromium substituted nickel ferrite in nitrilotriacetic acid medium

NASA Astrophysics Data System (ADS)

Sathyaseelan, V. S.; Chandramohan, P.; Velmurugan, S.

2016-12-01

High temperature (HT) dissolution of chromium substituted nickel ferrite was carried out with relevance to the decontamination of nuclear reactors by way of chemical dissolution of contaminated corrosion product oxides present on stainless steel coolant circuit surfaces. Chromium substituted nickel ferrites of composition, NiFe(2-x)CrxO4 (x ≤ 1), was synthetically prepared and characterized. HT dissolution of these oxides was carried out in nitrilotriacetic acid medium at 160 °C. Dissolution was remarkably increased at 160 °C when compared to at 85 °C in a reducing decontamination formulation. Complete dissolution could be achieved for the oxides with chromium content 0 and 0.2. Increasing the chromium content brought about a marked reduction in the dissolution rate. About 40 fold decrease in rate of dissolution was observed when chromium was increased from 0 to 1. The rate of dissolution was not very significantly reduced in the presence of N2H4. Dissolution of oxide was found to be stoichiometric.

Microstructural Characterization and Mechanical Properties Analysis of Weld Metals with Two Ni Contents During Post-Weld Heat Treatments

NASA Astrophysics Data System (ADS)

Wu, Da-yong; Han, Xiu-lin; Tian, Hong-tao; Liao, Bo; Xiao, Fu-ren

2015-05-01

This study designed post-weld heat treatments, including reheating and tempering, associated with hot bending to investigate the microstructures, toughness, and hardness of two weld metals with different Ni contents (<1 wt pct level). The results indicated that a high Ni content decreased the ferrite transformation temperature and increased the proportion of acicular ferrite (AF). Furthermore, a high Ni content promoted the martensite/austenite (M/A) constituent formation after reheating. The promotion of the M/A formation increased the number of cementite particles, and accelerated cementite coarsening during tempering. The large-angle grain boundary density from the AF improved the toughness despite the negative effect of cementite. The strengthening contributions were calculated, and the grain refinement was the greatest. The high Ni content decreased the effective grain size with a 2 deg tolerance angle, thus enhancing the grain refinement contribution.

Influence of Al Addition Upon the Microstructure and Mechanical Property of Dual-Phase 9Cr-ODS Steels

NASA Astrophysics Data System (ADS)

Zhou, Xiaosheng; Ma, Zongqing; Yu, Liming; Huang, Yuan; Li, Huijun; Liu, Yongchang

2018-06-01

With Al addition, dual-phase oxide dispersion strengthened (ODS) steels consisting of martensite and ferrite are fabricated by spark plasma sintering. It is found that Al addition has a negligible effect on martensite lath size, while the amount and size of ferrite grains are related to the Al content. M23C6 (M = Fe, Cr) carbides have been identified within the ferrite grains or along ferrite boundaries. With increasing Al concentration, more fine Y-Al-O oxide nanoparticles are formed. Upon annealing treatment, homogeneous and refined distribution of ferrite grains is obtained, which may involve the particle-stimulated nucleation of recrystallization caused by the large sized M23C6. As Al is increased from 0.05 to 0.1 wt%, the tensile strength of the annealed steel is decreased, as well as its ductility. For the annealed 9Cr-ODS steel containing 0.1 wt% Al, in tensile loading the large sized M23C6 along ferrite boundaries would facilitate the cracking along boundaries between the hard annealed ferrite and soft annealed martensite, producing the mixed fracture of dimple and intergranular fracture.

Synthesis and characterization of CoFe2O4/polyaniline nanocomposites for electromagnetic interference applications.

PubMed

Praveena, K; Srinath, S

2014-06-01

The Cobalt ferrite (CoFe2O4) powders were synthesized by Co-precipitation method. The as prepared ferrite powders were incorporated into a polyaniline matrix at various volumetric ratios. The as prepared composites of ferrite and polyaniline powders were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM). The particle size of CoFe2O4 is found to be 20 nm. The saturation magnetization (M(s)) of all the composites was found to be decreasing with decrease of ferrite content, while coercivity (H(c)) remained at the value corresponding to pure cobalt ferrite nanopowders. The complex permittivity (epsilon' and epsilon") and permeability (mu' and mu") of composite samples were measured in the range of 1 MHz to 1.1 GHz. The value of epsilon' and mu' found to be increased with ferrite volume concentration.

The influence of Ga doping on structural magnetic and dielectric properties of NiCr0.2Fe1.8O4 spinel ferrite

NASA Astrophysics Data System (ADS)

Ajmal, Muhammad; Islam, M. U.; Ashraf, Ghulam Abbas; Nazir, Muhammad Aamir; Ghouri, M. I.

2017-12-01

A series of spinel ferrites NiCr0.2GaxFe1.8-xO4 (x=0.00, 0.002, 0.04, 0.06, 0.08) was prepared by co precipitation technique. The influence of rare earth element Ga ions the structural dielectric and magnetic properties of NiCr0.2Fe1.8O4 ferrites was investigated. The X-ray diffraction confirmed the phase precipitated out was pure spinel phase with few traces of secondary phases. The crystallite size decreases and density increases with the increases of Ga contents. The magnetic moment, saturation magnetization and remanent magnetization increased with addition of Ga ions in spinel ferrite. The dielectric constant is described that it decreases more suddenly at low frequencies as compare at higher frequencies. The decrease in dielectric loss with frequency follows Deby's relaxation phenomena. Both the variation in tan loss and dielectric loss with frequency shows a similar. AC conductivity increases with the increases of frequency which inversely proportional to concentration of Ga3+ ions follows Jonscher law. These Gallium Chromium doped nickel ferrites are very helpful for high frequency switching devices.

Fe3O4 nanoparticles decorated MWCNTs @ C ferrite nanocomposites and their enhanced microwave absorption properties

NASA Astrophysics Data System (ADS)

Zhang, Kaichuang; Gao, Xinbao; Zhang, Qian; Chen, Hao; Chen, Xuefang

2018-04-01

Fe3O4 nanoparticles decorated MWCNTs @ C ferrite nanocomposites were synthesized using a co-precipitation method and a calcination process. As one kind absorbing material, we researched the electromagnetic absorption properties of the composites that were mixed with a filler loading of 80 wt% paraffin. In addition, we studied the influence of the magnetic nanoparticle content on the absorbing properties. The results showed that the frequency corresponding to the maximum absorptions shifted to lower frequency when the magnetic nanoparticles content increased. The Fe3O4 nanoparticles decorated MWCNTs @ C ferrite nanocomposites with approximately 60% Fe3O4 nanoparticles showed the best electromagnetic absorption properties. The maximum reflection loss was -52.47 dB with a thickness of 2.0 mm at 10.4 GHz.

Effects of Natural Rubber on Microwave Absorption Characteristics of Some Li-Ni-Zn Ferrite-Thermoplastic Natural Rubber Composites

NASA Astrophysics Data System (ADS)

Abdul Hamid, Siti Atkah; Abdullah, Mustaffa Hj.; Ahmad, Sahrim Hj.; Mansor, Abdul Aziz; Yusoff, Ahmad Nazlim

2002-09-01

A microwave (Li0.5Fe0.5)0.4Ni0.3Zn0.3Fe2O4 (LNZ) ferrite was prepared by a conventional sintering method in air. Thermoplastic natural rubber (TPNR) was prepared from polypropylene (PP) and natural rubber (NR) in the ratios of 80:20, 70:30, 60:40, 50:50 and 40:60 with liquid natural rubber as a compatibilizer by a melt blending technique. LNZ ferrite-TPNR composites with 20 wt% ferrite filler were prepared using a Brabender plasticorder internal mixer. The microwave electromagnetic properties of the composites were studied in the frequency range of 0.3-13.5 GHz using a microwave vector network analyzer (MVNA). The real and imaginary components of the relative complex dielectric permittivity (\\varepsilonr*=\\varepsilonr\\prime-j\\varepsilonr\\prime\\prime) and magnetic permeability (μr*=μr\\prime-jμr\\prime\\prime) were calculated from the measured complex scattering parameters (S11* and S12*) using the Nicolson-Ross model. The dielectric and magnetic properties were found to depend on the NR and PP content in the composites. The minimum reflection loss (RL) under the matching conditions increases with increasing NR content.

La+3 effectiveness replacement on the ferrite material (Cu0,2Zn0,45LaxFe2-xO4 ) On the structural and electrical and magnetic features

NASA Astrophysics Data System (ADS)

Hussain, Farouq I.; Alaa Najem, Rusul

2018-05-01

Nano ferrite with chemical formula (Ni 0.35 Cu 0.2 Zn 0.45 Lax Fe 2-x O 4), were chemically collected utilizing sol-gel auto – combustion procedure for the values of (X=0.0, 0.025, 0.05 and 0.075). The prepared samples were calcined at (900°C) for (2h), the formation of ferrite was assured using (XRD) and (SEM) techniques. X-ray diffractometer result shows that ferrite have spinal cubic phase with a particle size ranging from (22-29 nm),the Lattice constant and density (ρx-ray) increased with La+3content while the porosity was noticed to decrease. And have been studied dielectric properties It was also observed that the value of the dielectric constant and the dielectric loss factor decreased by increasing the frequency. The increase in alternating conductivity (σa.c) was also observed with increasing frequency.

78 FR 63517 - Control of Ferrite Content in Stainless Steel Weld Metal

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-24

...The U.S. Nuclear Regulatory Commission (NRC) is issuing a revision to Regulatory Guide (RG) 1.31, ``Control of Ferrite Content in Stainless Steel Weld Metal.'' This guide (Revision 4) describes a method that the NRC staff considers acceptable for controlling ferrite content in stainless steel weld metal. It updates the guide to remove references to outdated standards and to remove an appendix that has been incorporated into relevant specifications.

Structural, morphological and electrical properties of Sn-substituted Ni-Zn ferrites synthesized by double sintering technique

NASA Astrophysics Data System (ADS)

Ali, M. A.; Uddin, M. M.; Khan, M. N. I.; Chowdhury, F.-U.-Z.; Haque, S. M.

2017-02-01

The Sn-substituted Ni-Zn ferrites, (0.0≤x≤0.30), have been synthesized by the standard double sintering technique from the oxide nanopowders of Ni, Zn, Fe and Sn. The structural and electrical properties have been investigated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistivity and dielectric measurements. From XRD data, the single cubic spinel phase has been confirmed for x≤0.1, whereas for x>0.1 an extra intermediate phase has been detected along with the cubic spinel phase of Ni-Zn ferrite. The grain size is increased due to Sn substitution in Ni-Zn ferrites. DC resistivity as a function of temperature has been measured by two probe method. The semiconducting nature has been found operative in the samples. The DC resistivity was found to decrease whilst the dielectric constant increased with increasing Sn content in Ni-Zn ferrites. The unusual behavior of the dielectric loss factor of the ferrites was explained by the Rezlescu model. The electrical relaxation of the ferrites has been studied in terms of electric modulus formalism and the time for dielectric relaxation was calculated. The contribution of grain resistance has been studied from the Cole-Cole plot. The suitability to use the as prepared samples in the miniaturized memory devices based capacitive components or energy storage principles are confirmed from the values of dielectric constant.

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

NASA Astrophysics Data System (ADS)

Othman, H. A.; Eltabey, M. M.; Ibrahim, Samia. E.; El-Deen, L. M. Sharaf; Elkholy, M. M.

2017-02-01

Co-ferrites nanoparticles that have been prepared by the co-precipitation method were added to sodium borosilicate (Na2O-B2O3-SiO2) 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 BO3 and BO4 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 MS and coercive field HC were determined. The obtained results revealed that a ferrimagnetic behavior were observed and as Co-ferrite concentration increases the values of MS and HC increase from 2.84 to 8.79 (emu/g) and from 88.4 to 736.3 Oe, respectively.

Influence of rare earth ion doping (Ce and Dy) on electrical and magnetic properties of cobalt ferrites

NASA Astrophysics Data System (ADS)

Hashim, Mohd.; Raghasudha, M.; Meena, Sher Singh; Shah, Jyoti; Shirsath, Sagar E.; Kumar, Shalendra; Ravinder, D.; Bhatt, Pramod; Alimuddin; Kumar, Ravi; Kotnala, R. K.

2018-03-01

Ce and Dy substituted Cobalt ferrites with the chemical composition CoCexDyxFe2-2xO4 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) were synthesized through the chemical route, citrate-gel auto-combustion method. The structural characterization was carried out with the help of XRD Rieveld analysis, SEM and EDAX analysis. Formation of spinel cubic structure of the ferrites was confirmed by XRD analysis. SEM and EDAX results show that the particles are homogeneous with slight agglomeration without any impurity pickup. The effect of RE ion doping (Ce and Dy) on the dielectric, magnetic and impedance studies was systematically investigated by LCR meter, Vibrating Sample Magnetometer and Impedance analyzer respectively at room temperature in the frequency range of 10 Hz-10 MHz. Various dielectric parameters viz., dielectric constant, dielectric loss and ac conductivity were measured. The dielectric constant of all the ferrite compositions shows normal dielectric dispersion of ferrites with frequency. Impedance analysis confirms that the conduction in present ferrites is majorly due to the grain boundary mechanism. Ferrite sample with x = 0.03 show high dielectric constant, low dielectric loss and hence can be utilized in high frequency electromagnetic devices. Magnetization measurements indicate that with increase in Ce and Dy content in cobalt ferrites, the magnetization values decreased and coercivity has increased.

77 FR 60478 - Control of Ferrite Content in Stainless Steel Weld Metal

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-03

...The U.S. Nuclear Regulatory Commission (NRC or the Commission) is issuing for public comment draft regulatory guide (DG), DG-1279, ``Control of Ferrite Content in Stainless Steel Weld Metal.'' This guide describes a method that the NRC staff considers acceptable for controlling ferrite content in stainless steel weld metal. Revision 4 updates the guide to remove references to outdated standards and to remove an appendix that has been incorporated into relevant specifications.

Microwave assisted scalable synthesis of titanium ferrite nanomaterials

NASA Astrophysics Data System (ADS)

Shukla, Abhishek; Bhardwaj, Abhishek K.; Singh, S. C.; Uttam, K. N.; Gautam, Nisha; Himanshu, A. K.; Shah, Jyoti; Kotnala, R. K.; Gopal, R.

2018-04-01

Titanium ferrite magnetic nanomaterials are synthesized by one-step, one pot, and scalable method assisted by microwave radiation. Effects of titanium content and microwave exposure time on size, shape, morphology, yield, bonding nature, crystalline structure, and magnetic properties of titanium ferrite nanomaterials are studied. As-synthesized nanomaterials are characterized by X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-Vis), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer measurements. XRD measurements depict the presence of two phases of titanium ferrite into the same sample, where crystallite size increases from ˜33 nm to 37 nm with the increase in titanium concentration. UV-Vis measurement showed broad spectrum in the spectral range of 250-600 nm which reveals that its characteristic peaks lie between ultraviolet and visible region; ATR-FTIR and Raman measurements predict iron-titanium oxide structures that are consistent with XRD results. The micrographs of TEM and selected area electron diffraction patterns show formation of hexagonal shaped particles with a high degree of crystallinity and presence of multi-phase. Energy dispersive spectroscopy measurements confirm that Ti:Fe compositional mass ratio can be controlled by tuning synthesis conditions. Increase of Ti defects into titanium ferrite lattice, either by increasing titanium precursor or by increasing exposure time, enhances its magnetic properties.

Significant reduction of saturation magnetization and microwave-reflection loss in barium-natural ferrite via Nd3+ substitution

NASA Astrophysics Data System (ADS)

Widanarto, W.; Ardenti, E.; Ghoshal, S. K.; Kurniawan, C.; Effendi, M.; Cahyanto, W. T.

2018-06-01

To minimize the signal degradation, many electronic devices require efficient microwave absorbers with very low reflection-losses within the X-band. We prepared a series of trivalent neodymium-ion (Nd3+) substituted barium-natural ferrite using a modified solid-state reaction method. The effect of the Nd3+-ion content on the structure, surface morphology, magnetic properties, and microwave reflection loss was studied. The composites were characterized using X-ray diffraction, a vibrating sample magnetometer, scanning electron microscopy, and a vector network analyzer. The XRD patterns of the sample without Nd3+ reveal the presence of BaFe12O19 (hexagonal) and BaFe2O4 (rhombohedral) phases. Furthermore, a new hexagonal crystal phase of Ba6Nd2Fe4O15 appeared after substituting Nd3+. The average size of the prepared barium-natural ferrite particles was estimated to be between 0.4 and 0.8 μm. Both saturation magnetization and microwave reflection losses of these barium-ferrites were significantly reduced by increasing the Nd3+ content.

Improvement of the magnetic moment of NiZn ferrites induced by substitution of Nd3+ ions for Fe3+ ions

NASA Astrophysics Data System (ADS)

Wu, Xuehang; Chen, Wen; Wu, Wenwei; Wu, Juan; Wang, Qing

2018-05-01

Four types of Ni-Zn based ferrites materials having the general formula Ni0.5Zn0.5NdxFe2-xO4 (0.0 ≤ x ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni0.5Zn0.5NdxFe2-xO4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni0.5Zn0.5NdxFe2-xO4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd3+ ions for partial Fe3+ ions do not change the spinel crystalline structure of MFe2O4. The incorporation of Nd3+ ions in place of Fe3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO3 increases with increase in Nd content. In this study, Ni0.5Zn0.5Nd0.08Fe1.92O4, calcined at 1000 °C, exhibits the highest magnetic moment (4.2954 μB) and the lowest coercivity (28.82 Oe).

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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. Themore » 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.« less

Fe(II)-substituted cobalt ferrite nanoparticles against multidrug resistant microorganisms

NASA Astrophysics Data System (ADS)

Žalnėravičius, Rokas; Paškevičius, Algimantas; Mažeika, Kęstutis; Jagminas, Arūnas

2018-03-01

The present study is focused on the determination the influence of cobalt content in the magnetic cobalt ferrite nanoparticles (Nps) on their antibacterial efficiency against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria and several Candida species, in particular C. parapsilosis and C. albicans. For the synthesis of Fe(II) substituted cobalt ferrite Nps by co-precipitation way, the L-lysine was used as the capping biocompatible agent and the particle size was successfully controlled to be in the range of 5-6.4 nm. The antimicrobial efficiencies of the CoxFe1-xFe2O4@Lys Nps, where x varies from 0.2 to 1.0, were evaluated through the quantitative analysis by comparing with that of Fe3O4@Lys Nps and L-lysine. In this way, it was evidenced that increase in the Co2+ content in the similar sized cobalt ferrite Nps resulted in an increase in their antimicrobial potency into 93.1-86.3 % for eukaryotic and into 96.4-42.7 % for prokaryotic strains. For characterization the composition, structure, and morphology of the tested herein Nps inductively coupled plasma optical emission spectrometry, X-ray diffraction, high-resolution transmission electron microscopy, Mössbauer, and FTIR spectroscopy techniques were conferred.

Transformation and precipitation in vanadium treated steels

NASA Astrophysics Data System (ADS)

Vassiliou, Andreas D.

A series of carbon manganese steels containing varying amounts of carbon, vanadium and nitrogen was investigated in relation to the solubility of VC and VN in austenite, the grain coarsening characteristics of austenite, the tempering of martensite and other structures, the transformation during continuous cooling, the effect of vanadium addition and increasing nitrogen content on the thermo-mechanical processing of austenite, and the transformation of various morphologies of austenite to ferrite.The sites for preferential nucleation and growth of ferrite were identified and the effect of ferrite grain size inhomogeneity was investigated with a view to minimising it.The C/N ratio in the V(CN) precipitates was largely controlled by C/N ratio in the steel and it was also influenced by the austenitising treatment. As expected, the solubility of VN was less than that of VC.A systematic investigation of austenitising time and temperature on the grain coarsening characteristics was carried out showing the effects of vanadium, carbon and nitrogen. It was tentatively suggested that C-C and N-N clustering in the vanadium free steels controlled the grain growth whereas in the presence of vanadium, it was shown that VN and VC pinned the austenite grain boundaries and restricted grain growth. However coarsening or solution of VC and VN allowed the grain bondaries to migrate and grain coarsening occurred. The grain coarsening temperature was controlled predominantly by VN, whilst the VC dissolved frequently below the grain coarsening temperature.In the as quenched martensite, increasing nitrogen progressively increased the as quenched hardness, and the hardness also greatly increased with increasing carbon and vanadium added together. Examining the precipitation strengthening in tempered martensite showed that in the absence of vanadium, martensite softened progressively with increasing temperature and time. Vanadium additions increased the hardness level during low temperature tempering and at higher tempering temperature introduced secondary hardening. The intensity of secondary hardening increased with increasing vanadium, whereas austenitising temperature had little or no effect. The softening after the secondary hardening was faster after austenitising at the higher temperature and when recrystallisation occurred at the highest tempering temperatures, the hardness was lower due to coarse recrystallised ferrite.Isothermal transformation studies showed that vanadium additions raised the Ar3 temperature and accelerated ferrite nucleation, whilst the growth of ferrite was delayed due to the formation of V(CN) interphase and general precipitation pinning, of the transformation front. Increasing nitrogen content in the V-steel increased the incubation period for ferrite nucleation and increasingly reduced the ferrite growth by increasing V(CN) precipitation pinning of the transformation front.Transformation during continuous cooling was examined in relation to the effect of vanadium, carbon and nitrogen together with the effect of austenitising temperature. Increasing austenitising temperature increased the austenite grain size, and it then became apparent that increasing vanadium, carbon and nitrogen increased the hardenability and raised the hardness level of the jominy curve for the non-martensitic products. (Abstract shortened by ProQuest.).

Controlled ferrite content improves weldability of corrosion-resistant steel

NASA Technical Reports Server (NTRS)

Malin, C. O.

1967-01-01

Corrosion-resistant steel that adds restrictions on chemical composition to ensure sufficient ferrite content decreases the tendency of CRES to develop cracks during welding. The equations restricting composition are based on the Schaeffler constitution diagram.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.

Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon contentmore » in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.« less

Microstructure and characterization of W-type hexaferrite Ba1-xLaxFe22+Fe163+O27 prepared by solid state method

NASA Astrophysics Data System (ADS)

Tang, Jin; Liu, Xiansong; Mehmood Ur Rehman, Khalid; Li, Dan; Li, Mingling; Yang, Yujie

2018-04-01

We report a successful preparation of Ba1-xLaxFe22+Fe163+O27 (x = 0.00-0.10) W-type hexagonal ferrites by standard ceramic method in a reduced oxygen atmosphere. In this work, the effect of the substitution La3+ rare-earth ions for Ba2+ ions on the structural and magnetic properties of the prepared samples have been studied. The phase identification of magnetic powders was performed by X-ray diffraction. The results of XRD show that the single phase was observed in the W-type ferrites with different La content. The SEM micrographs showed that the ferrites have formed the hexagonal structure. The magnetic properties of the samples were metric by a vibrating sample magnetometer. The coercivity (Hc) of the particles decreases with the increase of La content(x), while the saturation magnetization (Ms) of the particles first increases with x from 0 to 0.05, and then begins to decrease when x continues to increase. The monotonic dependence of the magnetic anisotropy field Ha and coercivity Hc on the La3+ doping amount is found to be mainly dominated by the competition between Ms and Keff.

Structural and magnetic properties of Ni1-xZnxFe2O4 synthesized through the sol-gel method

NASA Astrophysics Data System (ADS)

Guan, Beh Hoe; Zahari, Muhammad Hanif; Chuan, Lee Kean

2016-11-01

Modification of crystal structure by means of substitution would result in the modification of the overall physical properties of crystallite materials especially in ferrites. This study aims to investigate the effect of non-magnetic Zn substitution in spinel NiFe2O4 and its direct effect towards its microstructural and magnetic properties. Magnetic nanoparticles of Nickel-Zinc ferrite with the chemical formula, Ni1-xZnxFe2O4 (x=0.00, 0.25, 0.50, 0.75) were synthesized through the sol-gel route. Phase formation and structural properties of the synthesized ferrite were identified through X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Magnetic properties such as the magnetic saturation, coercivity and remanence were measured by a vibrating sample magnetometer (VSM). XRD measurements reveals successful synthesis of single-phased Nickel ferrite and Nickel—Zinc ferrite. Both crystallite and grain size shows fluctuation with increasing Zn content. The ferrites were found to be ferrimagnetic in nature and show differing values with different x values.

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

NASA Astrophysics Data System (ADS)

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.

Carbon concentration measurements by atom probe tomography in the ferritic phase of high-silicon steels

DOE PAGES

Rementeria, Rosalia; Poplawsky, Jonathan D.; Aranda, Maria M.; ...

2016-12-19

Current studies using atom probe tomography (APT) show that bainitic ferrite formed at low temperature contains more carbon than what is consistent with the paraequilibrium phase diagram. However, nanocrystalline bainitic ferrite exhibits a non-homogeneous distribution of carbon atoms in arrangements with specific compositions, i.e. Cottrell atmospheres, carbon clusters, and carbides, in most cases with a size of a few nanometers. The ferrite volume within a single platelet that is free of these carbon-enriched regions is extremely small. Proximity histograms can be compromised on the ferrite side, and a great deal of care should be taken to estimate the carbon contentmore » in regions of bainitic ferrite free from carbon agglomeration. For this purpose, APT measurements were first validated for the ferritic phase in a pearlitic sample and further performed for the bainitic ferrite matrix in high-silicon steels isothermally transformed between 200 °C and 350 °C. Additionally, results were compared with the carbon concentration values derived from X-ray diffraction (XRD) analyses considering a tetragonal lattice and previous APT studies. In conclusion, the present results reveal a strong disagreement between the carbon content values in the bainitic ferrite matrix as obtained by APT and those derived from XRD measurements. Those differences have been attributed to the development of carbon-clustered regions with an increased tetragonality in a carbon-depleted matrix.« less

Microwave magnetic properties of spinel ferrite films deposited by one-step electrochemical method

NASA Astrophysics Data System (ADS)

Zhang, Yao; Yuan, Lixin; Zhang, Xiaozhi; Zhang, Jie; Yue, Zhenxing; Li, Longtu

2017-07-01

Spinel ferrites have been widely used in microwave devices due to their excellent electromagnetic properties. In this study, two kinds of spinel ferrite films, Fe3O4 and Co xFe3-xO4, were grown on Pt(111)/Ti/SiO2/Si substrates by one-step electrochemical deposition method. The XRD and SEM characterizations demonstrated that the orientation of the ferrite films changed from (111) to (100) with the increase of depositing time. The cobalt content within Co xFe3-xO4 films was studied in detail by EDS analysis. The ferromagnetic resonance (FMR) responses of the ferrite films were measured by the flip-chip method using a vector network analyzer (VNA). It showed that the FMR frequency of Fe3O4 films reached to 10.5 GHz under an out-plane magnetic field of 5 kOe, while it reached to 27 GHz under an in-plane magnetic field of 5 kOe for Co xFe3-xO4 films. Meanwhile, whether the magnetic field was applied parallelly or perpendicularly, the resonant peaks were increased linearly with increasing the magnetic field, indicating that the films are promising candidates for applications in tunable wave-absorbing materials or other tunable frequency devices.

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

NASA Astrophysics Data System (ADS)

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.

Synthesis, structural and magnetic properties of Mg0.6Zn0.4CrxFe2-xO4 (0.0 ≤ x ≤ 2.0) nano ferrite

NASA Astrophysics Data System (ADS)

Verma, R.; Kane, S. N.; Raghuvanshi, S.; Satalkar, M.; Modak, S. S.; Mazaleyrat, F.

2018-05-01

Present study reports, effect on structural, magnetic properties of Cr doped Mg-Zn nano-ferrite: Mg0.6Zn0.4CrxFe2-xO4 (0.0≤ x≤2.0), synthesized by sol-gel auto combustion method. X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were utilized to monitor the effect of Cr substitution on structural, magnetic properties, and correlation between them. XRD confirms the formation of single phase spinel nano ferrite with particle size ranging between 3.9 - 40.5 nm, whereas EDS confirms the formation of the estimated ferrite composition. Distribution of Mg, Zn, Cr, Fe cations on tetrahedral (A), octahedral (B) site show mixed spinel structure. Increase of Cr content leads to increase of specific surface area (4.35 - 28.28 m2/g), decrease of experimental saturation magnetization at 300 K (varies between 0.57 - 40.95 Am2/kg), and theoretical magnetization at 0 K (range between 13.37 - 56.77 Am2/kg). Observed changes in coercivity values reflect soft magnetic nature of the studied ferrites.

Effects of nitrogen in shielding gas on microstructure evolution and localized corrosion behavior of duplex stainless steel welding joint

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei; Zhou, Chao

2017-05-01

The effects of nitrogen addition in shielding gas on microstructure evolution and localized corrosion behavior of duplex stainless steel (DSS) welds were studied. N2-supplemented shielding gas facilitated the primary austenite formation, suppressed the Cr2N precipitation in weld root, and increased the microhardnesses of weld metal. Furthermore, N2-supplemented shielding gas increased pitting resistance equivalent number (PREN) of austenite, but which decreased slightly PREN of ferrite. The modified double loop electrochemical potentiokinetic reactivation in 2 M H2SO4 + 1 M HCl was an effective method to study the localized corrosion of the different zones in the DSS welds. The adding 2% N2 to pure Ar shielding gas improved the localized corrosion resistance in the DSS welds, which was due to compensation for nitrogen loss and promoting nitrogen further solution in the austenite phases, suppression of the Cr2N precipitation in the weld root, and increase of primary austenite content with higher PREN than the ferrite and secondary austenite. Secondary austenite are prone to selective corrosion because of lower PREN compared with ferrite and primary austenite. Cr2N precipitation in the pure Ar shielding weld root and heat affected zone caused the pitting corrosion within the ferrite and the intergranular corrosion at the ferrite boundary. In addition, sigma and M23C6 precipitation resulted in the intergranular corrosion at the ferrite boundary.

Magneto-structural studies of sol-gel synthesized nanocrystalline manganese substituted nickel ferrites

NASA Astrophysics Data System (ADS)

Pandav, R. S.; Patil, R. P.; Chavan, S. S.; Mulla, I. S.; Hankare, P. P.

2016-11-01

Nanocrystalline NiFe2-xMnxO4 (2≥x≥0) ferrites were prepared by sol-gel method. X-ray diffraction patterns reveal that synthesized compounds are in single phase cubic spinel lattice for all the composition. The surface morphology of all the samples were studied by scanning electron microscopy. The particle size measured from transmission electron microscopy and X-ray diffraction patterns confirms the nanosized dimension of the as-prepared powder. The elemental analysis was carried out by energy dispersive X-ray analysis technique. Magnetic properties such as saturation magnetization, coercivity and remanence are studied as a function of increasing Mn concentration at room temperature. The saturation magnetization shows a decreasing trend with increase in Mn content. The substitution of manganese in the nickel ferrite affects the structural and magnetic properties of cubic spinels.

Effects of Surface-Modified MgO Nanoparticles on Inclusion Characteristics and Microstructure in Carbon Structural Steel

NASA Astrophysics Data System (ADS)

Guo, Hao; Yang, Shufeng; Li, Jingshe; Zhao, Mengjing; Chen, Zhengyang; Zhang, Xueliang; Li, Jikang

2018-05-01

An innovative approach involving chemical modification of the surface of MgO nanoparticles (NPs) for steelmaking and application of NPs to carbon structural steel has been investigated. The results show that the inclusions in the test steels were completely converted to MgAl2O4 spinel or MnS complex inclusions. The mean inclusion size decreased with increasing NP content from 0.01% to 0.03%, but increased at 0.05% because of NP aggregation. Addition of NPs increased the amount of intragranular ferrite and prevented polygonal ferrite formation, thereby enhancing the impact toughness. Impact tests showed that the dimple fractures in steel with 0.05% NP content were deeper than those in the other samples because the MgAl2O4 inclusions were larger. The surface-modified MgO NPs had a major effect on the inclusion characteristics and microstructure of carbon structural steel.

Electrical and optical properties of nickel ferrite/polyaniline nanocomposite.

PubMed

Khairy, M; Gouda, M E

2015-07-01

Polyaniline-NiFe2O4 nanocomposites (PANI-NiFe2O4) with different contents of NiFe2O4 (2.5, 5 and 50 wt%) were prepared via in situ chemical oxidation polymerization, while the nanoparticles nickel ferrite were synthesized by sol-gel method. The prepared samples were characterized using some techniques such as Fourier transforms infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Moreover, the electrical conductivity and optical properties of the nanocomposites were investigated. Pure (PANI) and the composites containing 2.5 and 5 wt% NiFe2O4 showed amorphous structures, while the one with 50 wt% NiFe2O4 showed a spinel crystalline structure. The SEM images of the composites showed different aggregations for the different nickel ferrite contents. FTIR spectra revealed to the formation of some interactions between the PANI macromolecule and the NiFe2O4 nanoparticles, while the thermal analyses indicated an increase in the composites stability for samples with higher NiFe2O4 nanoparticles contents. The electrical conductivity of PANI-NiFe2O4 nanocomposite was found to increase with the rise in NiFe2O4 nanoparticle content, probably due to the polaron/bipolaron formation. The optical absorption experiments illustrate direct transition with an energy band gap of Eg  = 1.0 for PANI-NiFe2O4 nanocomposite.

Electrical and optical properties of nickel ferrite/polyaniline nanocomposite

PubMed Central

Khairy, M.; Gouda, M.E.

2014-01-01

Polyaniline–NiFe2O4 nanocomposites (PANI–NiFe2O4) with different contents of NiFe2O4 (2.5, 5 and 50 wt%) were prepared via in situ chemical oxidation polymerization, while the nanoparticles nickel ferrite were synthesized by sol–gel method. The prepared samples were characterized using some techniques such as Fourier transforms infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Moreover, the electrical conductivity and optical properties of the nanocomposites were investigated. Pure (PANI) and the composites containing 2.5 and 5 wt% NiFe2O4 showed amorphous structures, while the one with 50 wt% NiFe2O4 showed a spinel crystalline structure. The SEM images of the composites showed different aggregations for the different nickel ferrite contents. FTIR spectra revealed to the formation of some interactions between the PANI macromolecule and the NiFe2O4 nanoparticles, while the thermal analyses indicated an increase in the composites stability for samples with higher NiFe2O4 nanoparticles contents. The electrical conductivity of PANI–NiFe2O4 nanocomposite was found to increase with the rise in NiFe2O4 nanoparticle content, probably due to the polaron/bipolaron formation. The optical absorption experiments illustrate direct transition with an energy band gap of Eg = 1.0 for PANI–NiFe2O4 nanocomposite. PMID:26199745

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiengmoon, A., E-mail: ampornw@nu.ac.th

The effects of Si on microstructure and phase transformation at elevated temperature of ferritic 31wt.%Cr-1.1wt.%C white cast irons with up to 3wt.%Si have been studied. Applications of these irons include parts requiring heat resistance at elevated temperature. The irons were produced by sand casting. The microstructure in as-cast condition and after being subjected to high temperature (700 to 1000 °C) was investigated by light microscopy, X-ray diffraction, and electron microscopy. The results revealed that the as-cast microstructure consisted mainly of primary ferrite dendrites and eutectic (ferrite + M{sub 7}C{sub 3}). Si promotes M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation in themore » irons subjected to transformation at elevated temperature, but no sigma phase was found. The extent of M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation increases proportional to the increasing transformation temperature, holding time and Si content in the irons. For the iron with 1.0wt.%Si content after holding at elevated temperatures, martensite was also found, which could be attributed to carbon accretion effects in eutectic ferrite. Si was incorporated in M{sub 23}C{sub 6} such that M{sub 23}C{sub 6} containing Si can show darker contrast under SEM-BEI as compared to M{sub 7}C{sub 3}; this is the opposite to what has been observed for the cases of typical M{sub 23}C{sub 6} and M{sub 23}C{sub 6} containing Mo or W. The results obtained are important to understand the change in properties of ferritic, high chromium irons containing Si subjected to elevated temperature.« less

Martensite phase stress and the strengthening mechanism in TRIP steel by neutron diffraction.

PubMed

Harjo, Stefanus; Tsuchida, Noriyuki; Abe, Jun; Gong, Wu

2017-11-09

Two TRIP-aided multiphase steels with different carbon contents (0.2 and 0.4 mass%) were analyzed in situ during tensile deformation by time-of-flight neutron diffraction to clarify the deformation induced martensitic transformation behavior and its role on the strengthening mechanism. The difference in the carbon content affected mainly the difference in the phase fractions before deformation, where the higher carbon content increased the phase fraction of retained austenite (γ). However, the changes in the relative fraction of martensitic transformation with respect to the applied strain were found to be similar in both steels since the carbon concentrations in γ were similar regardless of different carbon contents. The phase stress of martensite was found much larger than that of γ or bainitic ferrite since the martensite was generated at the beginning of plastic deformation. Stress contributions to the flow stress were evaluated by multiplying the phase stresses and their phase fractions. The stress contribution from martensite was observed increasing during plastic deformation while that from bainitic ferrite hardly changing and that from γ decreasing.

Effects of Cooling Conditions on Microstructure, Tensile Properties, and Charpy Impact Toughness of Low-Carbon High-Strength Bainitic Steels

NASA Astrophysics Data System (ADS)

Sung, Hyo Kyung; Shin, Sang Yong; Hwang, Byoungchul; Lee, Chang Gil; Lee, Sunghak

2013-01-01

In this study, four low-carbon high-strength bainitic steel specimens were fabricated by varying finish cooling temperatures and cooling rates, and their tensile and Charpy impact properties were investigated. All the bainitic steel specimens consisted of acicular ferrite, granular bainite, bainitic ferrite, and martensite-austenite constituents. The specimens fabricated with higher finish cooling temperature had a lower volume fraction of martensite-austenite constituent than the specimens fabricated with lower finish cooling temperature. The fast-cooled specimens had twice the volume fraction of bainitic ferrite and consequently higher yield and tensile strengths than the slow-cooled specimens. The energy transition temperature tended to increase with increasing effective grain size or with increasing volume fraction of granular bainite. The fast-cooled specimen fabricated with high finish cooling temperature and fast cooling rate showed the lowest energy transition temperature among the four specimens because of the lowest content of coarse granular bainite. These findings indicated that Charpy impact properties as well as strength could be improved by suppressing the formation of granular bainite, despite the presence of some hard microstructural constituents such as bainitic ferrite and martensite-austenite.

The effect of Si-contents on the impact properties and dynamic graphite growth for cast iron QT400-18L

NASA Astrophysics Data System (ADS)

Lipeng, Jiang; Yingdong, Qu; Rongde, Li

2018-03-01

Low temperature impact test of QT400-18L ductile iron was investigated. The microstructure and fracture morphology were analyzed by the optical microscope and scanning electron microscope. The effect of different Si content on the graphite growth by liquid quenching method was discussed. There are the highest impact energies for the cast iron with 2.1% of Si over the whole investigated temperature range (‑60 to 20 °C). With the Si element addition increased from 1.9% to 2.1%, the graphite nodulizing grade of QT400 18L is increased from 5 to 7. However the graphite nodulizing grade is reduced from 7 to 6 with Si content increasing from 2.1% to 2.3%. When the Si element addition is exceed 2.1%, the excess of Si content also leads to abnormal graphite. The large size of the abnormal graphite is equivalent to a larger microcrack in the ferrite matrix, and it is helpful for the crack propagation. Large size of abnormal graphite not only destroyed the continuity of ferritic matrix, but also it creates the stress concentration in the surrounding.

Microstructural, dielectric and magnetic properties of multiferroic composite system barium strontium titanate – nickel cobalt ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pahuja, Poonam, E-mail: poonampahuja123@gmail.com; Tandon, R. P., E-mail: ram-tandon@hotmail.com

2015-05-15

Multiferroic composites (1-x) Ba{sub 0.95}Sr{sub 0.05}TiO{sub 3} + (x) Ni{sub 0.8}Co{sub 0.2}Fe{sub 2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4) has been prepared by solid state reaction method. X-ray diffraction analysis of the composite samples confirmed the presence of both barium strontium titanate (BST) and nickel cobalt ferrite (NCF) phases. FESEM images indicated the well dispersion of NCF grains among BST grains. Dielectric constant and loss of the composite samples decreases with increase in frequency following Maxwell-Wagner relaxation mechanism. Composite sample with highest ferrite content possesses highest values of remanent and saturation magnetization.

A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

PubMed

Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

2014-12-01

Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of Ni content on stainless steel fabricated by laser melting deposition

NASA Astrophysics Data System (ADS)

Zhang, H.; Zhang, C. H.; Wang, Q.; Wu, C. L.; Zhang, S.; Chen, J.; Abdullah, Adil O.

2018-05-01

The novel stainless steel + x wt.% Ni (x = 0, 3.05, 6.10, 9.15) specimens were successfully fabricated by laser melting deposition, aiming at investigating the influence of Ni content on stainless steel structure and property. The effects of Ni content on phase compositions, microstructure, microhardness, wear and electrochemical corrosion resistance of as-deposited stainless steel were studied systematically using XRD, OM, SEM, microhardness tester, friction-wear tester and potentiodynamic polarization measurement, respectively. Experimental results showed that with the increase of Ni content, the constituent phase of the as-deposited specimen changed from ferrite phase (specimen for x = 0) to austenite phase (specimen for x = 9.15). The microstructure growth followed the principle of dendrite growth. However, the dominant microstructure varied from equiaxed dendrite to columnar dendrite with increasing Ni content. Phase transition from ferrite phase to austenite phase with the addition of Ni content resulted in the decrease of microhardness value from 643HV to 289HV. Meanwhile, the wear resistance of as-deposited specimens decreased gradually with the increasing of Ni content, which might be attributed to the fact that the wear resistance is proportional to microhardness according to Archard's law. It was noted that corrosion resistance of as-deposited stainless steel was extremely improved with the increase of Ni content. The higher Ni content specimen (specimen for x = 9.15) exhibited the best corrosion resistance among the tested specimens based on corrosion rate, which was one order of magnitude lower than that of the lower Ni content specimens (specimens for x = 0, 3.05).

Transformation Characteristics of Ferrite/Carbide Aggregate in Continuously Cooled, Low Carbon-Manganese Steels

NASA Astrophysics Data System (ADS)

Di Martino, S. F.; Thewlis, G.

2014-02-01

Transformation characteristics and morphological features of ferrite/carbide aggregate (FCA) in low carbon-manganese steels have been investigated. Work shows that FCA has neither the lamellae structure of pearlite nor the lath structure of bainite and martensite. It consists of a fine dispersion of cementite particles in a smooth ferrite matrix. Carbide morphologies range from arrays of globular particles or short fibers to extended, branched, and densely interconnected fibers. Work demonstrates that FCA forms over similar cooling rate ranges to Widmanstätten ferrite. Rapid transformation of both phases occurs at temperatures between 798 K and 973 K (525 °C and 700 °C). FCA reaction is not simultaneous with Widmanstätten ferrite but occurs at temperatures intermediate between Widmanstätten ferrite and bainite. Austenite carbon content calculations verify that cementite precipitation is thermodynamically possible at FCA reaction temperatures without bainite formation. The pattern of precipitation is confirmed to be discontinuous. CCT diagrams have been constructed that incorporate FCA. At low steel manganese content, Widmanstätten ferrite and bainite bay sizes are significantly reduced so that large amounts of FCA are formed over a wide range of cooling rates.

The influence of Cr content on the mechanical properties of ODS ferritic steels

NASA Astrophysics Data System (ADS)

Li, Shaofu; Zhou, Zhangjian; Jang, Jinsung; Wang, Man; Hu, Helong; Sun, Hongying; Zou, Lei; Zhang, Guangming; Zhang, Liwei

2014-12-01

The present investigation aimed at researching the mechanical properties of the oxide dispersion strengthened (ODS) ferritic steels with different Cr content, which were fabricated through a consolidation of mechanical alloyed (MA) powders of 0.35 wt.% nano Y2O3 dispersed Fe-12.0Cr-0.5Ti-1.0W (alloy A), Fe-16.0Cr-0.5Ti-1.0W (alloy B), and Fe-18.0Cr-0.5Ti-1.0W (alloy C) alloys (all in wt.%) by hot isostatic pressing (HIP) with 100 MPa pressure at 1150 °C for 3 h. The mechanical properties, including the tensile strength, hardness, and impact fracture toughness were tested by universal testers, while Young's modulus was determined by ultrasonic wave non-destructive tester. It was found that the relationship between Cr content and the strength of ODS ferritic steels was not a proportional relationship. However, too high a Cr content will cause the precipitation of Cr-enriched segregation phase, which is detrimental to the ductility of ODS ferritic steels.

Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

DOEpatents

Leitnaker, James M.

1981-01-01

Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015-0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

DOEpatents

Leitnaker, J.M.

Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015 to 0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

Influence of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel welding joints

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei; Zhang, Jianli

2017-02-01

The influences of microstructure and elemental partitioning on pitting corrosion resistance of duplex stainless steel joints welded by gas tungsten arc welding (GTAW) and flux-cored arc welding (FCAW) with different shielding gas compositions were studied by optical microscopy, electron backscatter diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, electron probe microanalysis, and potentiostatic and potentiodynamic polarization methods The adding 2% N2 in shielding gas facilitated primary austenite formation in GTAW weld metal (WM) and suppressed Cr2N precipitation in GTAW weld root. In the HAZ, the banded microstructure disappeared while the coarse ferrite grains maintained same orientation as the banded ferrite in the BM. In the WM, the ferrite had one single orientation throughout a grain, whereas several families of austenite appeared. The austenite both in BM and WM enriched in Ni and nitro`gen, while Cr and Mo were concentrated in the ferrite and thus no element showed clear dendritic distribution in the WM (ER2209 and E2209T1). In addition, the secondary austenite had higher Ni content but lower Cr and Mo content than the primary austenite. The N2-supplemented shielding gas promoted nitrogen solid-solution in the primary and secondary austenite. Furthermore, the secondary austenite had relatively lower pitting resistance equivalent number (PREN) than the ferrite and primary austenite, thereby resulting in its preferential corrosion. The Cr2N precipitation led to relatively poor resistance to pitting corrosion in three HAZs and pure Ar shielding GTAW weld root. The N2-supplemented shielding gas improved pitting corrosion resistance of GTAW joint by increasing PREN of secondary austenite and suppressing Cr2N precipitation. In addition, the FCAW WM had much poorer resistance to pitting corrosion than the GTAW WM due to many O-Ti-Si-Mn inclusions. In the BM, since the austenite with lower PREN compared to the ferrite, the pitting corrosion occurred at the ferrite and austenite interface or within the austenite.

Effect of free Cr content on corrosion behavior of 3Cr steels in a CO2 environment

NASA Astrophysics Data System (ADS)

Li, Wei; Xu, Lining; Qiao, Lijie; Li, Jinxu

2017-12-01

The corrosion behavior of 3Cr steels with three microstructures (martensite, bainite, combined ferrite and pearlite) in simulated oil field formation water with a CO2 partial pressure of 0.8 MPa was investigated. The relationships between Cr concentrations in corrosion scales and corrosion rates were studied. The precipitated phases that contained Cr were observed in steels of different microstructures, and free Cr content levels were compared. The results showed that steel with the martensite microstructure had the highest free Cr content, and thus had the highest corrosion resistance. The free Cr content of bainite steel was lower than that of martensite steel, and the corrosion rate of bainite steel was higher than that of martensite steel. Because large masses of Cr were combined in ferrite and pearlite steel, the corrosion rates of ferrite and pearlite steel were the highest. Free Cr content in steel affects its corrosion behavior greatly.

Physical Nature of the Processes in Structure Forming, Phase and Chemical Composition of pipe Permanent Joints when MMA Welding

NASA Astrophysics Data System (ADS)

Il'yaschenko, D. P.; Chinakhov, D. A.; Danilov, V. I.; Sadykov, I. D.

2016-04-01

The paper outlines peculiarities of structure formation, phase and chemical composition in regard to heat content in molten electrode metal beads when pipe steel (steel 09G2S) welding using power sources with various energy characteristics. Mathematical calculations indicate an inverter power source provides minor heat content into the bead of electrode metal when welding. Experimental research has pointed at 4-9 % increase in impact strength of joints produced using an inverter power source in comparison with samples produced applying a diode rectifier. The following factors can possibly give rise to the increasing impact strength: difference in microstructures of weld joints, up to 50% shortening ferritic plates in metal of weld joint, change in dimensions of ferritic grains in the heat-affected zone by as much as 17.5 %, and decrease in the extent of heat-affected zone by 50%.

Synthesis, structural, dielectric and magnetic properties of CuFe2O4/MnO2 nanocomposites

NASA Astrophysics Data System (ADS)

Ali, Kashif; Bahadur, Ali; Jabbar, Abdul; Iqbal, Shahid; Ahmad, Ijaz; Bashir, Muhammad Imran

2017-07-01

Novel nanocomposite of (1-x)CuFe2O4/xMnO2 [x=10% to 50 wt%] has been synthesized by two step wet chemical route without impurity. The x-ray diffraction analysis shows the formation of both phases with crystallite size 40-100 nm which is consist ant with estimated size of SEM.The FTIR spectra confirms the characteristics vibration of ferrites atoms at tetrahedral and octahedral sites along with Mn-O vibration mode, which also confirms the coexistence of both phases. The dielectric properties studied by LCR meter in frequency range of 1 K Hz to 2 MHz.The dielectric constant and tangent loss shows same dispersion of ferrites while a.c. conductivity decreases with increase in MnO2 contents. The real and imaginary part of impedance also calculated which shows decreasing trend at higher frequency. The magnetic characterization performed by vibrating sample magnetometer (VSM) at room temperature, which shows normal ferromagnetic behavior of ferrites but saturation magnetization and coercivity decreases with incorporation of MnO2 contents.

Frequency and field dependent dynamic properties of CoFe{sub 2−x}Al{sub x}O{sub 4} ferrite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuanr, Bijoy K.; Department of Physics, University of Colorado, 1420 Austin Bluffs Parkway, Colorado Springs, CO 80918; Mishra, S.R., E-mail: srmishra@memphis.edu

2016-04-15

Highlights: “CoFe{sub 2−x} Al{sub x}O{sub 4} ferrite nanoparticles: Static and dynamic properties” • Grain size reduction with Al{sup 3+} content. • Reduction in Ms, Hc, with increasing Al{sup 3+} content. • Increase in resonance frequency with applied field. • Decrease in resonance field with increase in Al{sup 3+} content. • Decrease in Gilbert parameter with increase in Al{sup 3+} content. - Abstract: Aluminum doped CoFe{sub 2−x}Al{sub x}O{sub 4} (0 ≤ x ≤ 0.9) nanoparticles were synthesized via auto-combustion. Formation of single phase cubic spinel structure was confirmed by X-ray diffraction (XRD) analysis. XRD analysis suggests a linear decrease in latticemore » cell parameters and grain size (90–55 nm) with the increase in Al{sup 3+} content. The saturation magnetization of samples decrease with increasing Al{sup 3+} content due to magnetic dilution effect. A concomitant linear reduction in coercivity was also observed mainly due to decrease in magnetic anisotropy. Frequency and field dependent dynamic properties of nanoparticles were studied by ferromagnetic resonance (FMR) technique. The resonance frequency increases linearly with magnetic field for all nanoparticles. Magnetic field dependent experimental absorption data (S{sub 21} vs. frequency) were compared with effective medium theory considering an effective demagnetization field and was observed to be in good agreement with each other. High Al{sup 3+} content reduces the Gilbert damping parameter thus making CoFe{sub 2−x}Al{sub x}O{sub 4} as an attractive material for high frequency applications.« less

Nano-crystalline Magnesium Substituted Cadmium Ferrites as X-band Microwave Absorbers

NASA Astrophysics Data System (ADS)

Bhongale, S. R.; Ingawale, H. R.; Shinde, T. J.; Pubby, Kunal; Bindra Narang, Sukhleen; Vasambekar, P. N.

2017-11-01

The magnetic and electromagnetic properties of nanocrystalline spinel ferrites with chemical formula MgxCd1-xFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared by oxalate co-precipitation method under microwave sintering technique were studied. The magnetic and dielectric parameters of ferrites were determined by using vibrating sample magnetometer (VSM) and vector network analyzer (VNA) respectively. Magnetic parameters such as saturation magnetizations (Ms), coercive force (Hc), remnant magnetization (Mr), Yafet-Kittel (Y-K) angle of ferrites were determined from hysteresis loops. The variation of real permittivity (ε‧), dielectric loss tangent (tanδe), real permeability (μ‧) and magnetic loss tangent (tanδm) with frequency and Mg2+content were studied in X-band frequency range. The values of ε‧, tanδe, μ‧ and tanδm of ferrites were observed to be in range of 4.2 - 6.12, 2.9 × 10-1 - 6 × 10-2, 0.6 - 1.12 and 4.5 × 10-1 - 2 × 10-3 respectively for the prepared compositions. The study of variation of reflection loss with frequency of all ferrites shows that ferrite with magnesium content x = 0.4 can be potential candidate for microwave applications in X-band.

Microstructure, Pitting Corrosion Resistance and Impact Toughness of Duplex Stainless Steel Underwater Dry Hyperbaric Flux-Cored Arc Welds

PubMed Central

Hu, Yu; Shen, Xiao-Qin; Wang, Zhong-Min

2017-01-01

Duplex stainless steel multi-pass welds were made at 0.15 MPa, 0.45 MPa, and 0.75 MPa pressure, simulating underwater dry hyperbaric welding by the flux-cored arc welding (FCAW) method, with welds of normal pressure as a benchmark. The purpose of this work was to estimate the effect of ambient pressure on the microstructure, pitting corrosion resistance and impact toughness of the weld metal. The microstructure measurement revealed that the ferrite content in the weld metal made at 0.45 MPa is the lowest, followed by that of 0.75 MPa and 0.15 MPa. The analysis of potentiodynamic polarization tests at 30 °C and 50 °C demonstrated that the pitting corrosion resistance depends on the phases of the lower pitting resistance equivalent numbers (PREN), secondary austenite and ferrite. The weld metal made at 0.45 MPa had the best resistance to pitting corrosion at 30 °C and 50 °C with the highest PRENs of secondary austenite and ferrite. The weld metal made at 0.15 MPa displayed the lowest pitting corrosion resistance at 30 °C with the lowest PREN of secondary austenite, while the weld metal made at 0.75 MPa was the most seriously eroded after being tested at 50 °C for the lowest PREN of ferrite, with large cluster pits seen in ferrite at 50 °C. The impact tests displayed a typical ductile-brittle transition because of the body-centered cubic (BCC) structure of the ferrite when the test temperature was lowered. All the weld metals met the required value of 34 J at −40 °C according to the ASTM A923. The highest ferrite content corresponded to the worst impact toughness, but the highest toughness value did not correspond to the greatest austenite content. With the decreasing of the test temperature, the drop value of absorbed energy was correlated to the ferrite content. Additionally, in this work, the weld metal made at 0.45 MPa had the best combined properties of pitting resistance and impact toughness. PMID:29258262

Microstructure, Pitting Corrosion Resistance and Impact Toughness of Duplex Stainless Steel Underwater Dry Hyperbaric Flux-Cored Arc Welds.

PubMed

Hu, Yu; Shi, Yong-Hua; Shen, Xiao-Qin; Wang, Zhong-Min

2017-12-18

Duplex stainless steel multi-pass welds were made at 0.15 MPa, 0.45 MPa, and 0.75 MPa pressure, simulating underwater dry hyperbaric welding by the flux-cored arc welding (FCAW) method, with welds of normal pressure as a benchmark. The purpose of this work was to estimate the effect of ambient pressure on the microstructure, pitting corrosion resistance and impact toughness of the weld metal. The microstructure measurement revealed that the ferrite content in the weld metal made at 0.45 MPa is the lowest, followed by that of 0.75 MPa and 0.15 MPa. The analysis of potentiodynamic polarization tests at 30 °C and 50 °C demonstrated that the pitting corrosion resistance depends on the phases of the lower pitting resistance equivalent numbers (PREN), secondary austenite and ferrite. The weld metal made at 0.45 MPa had the best resistance to pitting corrosion at 30 °C and 50 °C with the highest PRENs of secondary austenite and ferrite. The weld metal made at 0.15 MPa displayed the lowest pitting corrosion resistance at 30 °C with the lowest PREN of secondary austenite, while the weld metal made at 0.75 MPa was the most seriously eroded after being tested at 50 °C for the lowest PREN of ferrite, with large cluster pits seen in ferrite at 50 °C. The impact tests displayed a typical ductile-brittle transition because of the body-centered cubic (BCC) structure of the ferrite when the test temperature was lowered. All the weld metals met the required value of 34 J at -40 °C according to the ASTM A923. The highest ferrite content corresponded to the worst impact toughness, but the highest toughness value did not correspond to the greatest austenite content. With the decreasing of the test temperature, the drop value of absorbed energy was correlated to the ferrite content. Additionally, in this work, the weld metal made at 0.45 MPa had the best combined properties of pitting resistance and impact toughness.

Effect of sulfur content on the microstructure and toughness of simulated heat-affected zone in Ti-killed steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jyelong Lee; Yeongtsuen Pan

1993-06-01

Four Ti-killed steels were made to study the specific influence of sulfur on the inclusion, microstructure, and toughness of a simulated heat-affected zone (HAZ). The HAZ toughness was mainly determined by the volume fraction of intragranular acicular ferrite (IAF) which was closely related to the supercooling required to initiate austenite to ferrite transformation. The extent of supercooling was strongly influenced by the composition of grain boundary and inclusions. Sulfur addition up to 102 ppm caused a segregation of sulfur to the grain boundaries and a change of inclusion phase from predominantly Ti-oxides to Ti-oxysulphides and MnS. This behavior, in turn,more » suppressed the formation of IAF polygonal ferrite and promoted the formation of IAF. Further addition of sulfur elevated transformation temperature and promoted the formation of polygonal ferrite due to the refinement of grain size and the increase of grain boundary associated inclusions. A methodology was proposed to evaluate the intragranular nucleation potential of inclusions, and the results showed that Ti-oxysulphides possessed better nucleation potential for IAF than Ti-oxides and MnS. With the lowest transformation temperature and most effective nuclei, the best HAZ toughness can be obtained at sulfur content of 102 ppm due to the achievement of the maximum volume fraction of IAF.« less

Tube manufacturing and characterization of oxide dispersion strengthened ferritic steels

NASA Astrophysics Data System (ADS)

Ukai, Shigeharu; Mizuta, Shunji; Yoshitake, Tunemitsu; Okuda, Takanari; Fujiwara, Masayuki; Hagi, Shigeki; Kobayashi, Toshimi

2000-12-01

Oxide dispersion strengthened (ODS) ferritic steels have an advantage in radiation resistance and superior creep rupture strength at elevated temperature due to finely distributed Y2O3 particles in the ferritic matrix. Using a basic composition of low activation ferritic steel (Fe-12Cr-2W-0.05C), cladding tube manufacturing by means of pilger mill rolling and subsequent recrystallization heat-treatment was conducted while varying titanium and yttria contents. The recrystallization heat-treatment, to soften the tubes hardened due to cold-rolling and to subsequently improve the degraded mechanical properties, was demonstrated to be effective in the course of tube manufacturing. For a titanium content of 0.3 wt% and yttria of 0.25 wt%, improvement of the creep rupture strength can be attained for the manufactured cladding tubes. The ductility is also adequately maintained.

Synthesis of metal-doped Mn-Zn ferrite from the leaching solutions of vanadium slag using hydrothermal method

NASA Astrophysics Data System (ADS)

Liu, Shiyuan; Wang, Lijun; Chou, Kuochih

2018-03-01

Using vanadium slag as raw material, Metal-doped Mn-Zn ferrites were synthesized by multi-step processes including chlorination of iron and manganese by NH4Cl, selective oxidation of Fe cation, and hydrothermal synthesis. The phase composition and magnetic properties of synthesized metal-doped Mn-Zn ferrite were characterized by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy (TEM), X-ray photon spectra (XPS) and physical property measurement. It was found that Mn/Zn mole ratio significantly affected the magnetic properties and ZnCl2 content significantly influenced the purity of the phase of ferrite. Synthesized metal-doped Mn-Zn ferrite, exhibiting a larger saturation magnetization (Ms = 60.01 emu/g) and lower coercivity (Hc = 8.9 Oe), was obtained when the hydrothermal temperature was controlled at 200 °C for 12 h with a Mn/Zn mole ratio of 4. The effect of ZnCl2 content, Mn/Zn mole ratio and temperature on magnetic properties of the synthesized metal-doped Mn-Zn ferrite were systemically investigated. This process provided a new insight to utilize resources in the aim of obtaining functional materials.

Synthesis and Characterization of Cobalt Substituted Zinc Ferrite Nanoparticles by Microwave Combustion Method.

PubMed

Sundararajan, M; Kennedy, L John; Vijaya, J Judith

2015-09-01

Pure and cobalt doped zinc ferrites were prepared by microwave combustion method using L-arginine as a fuel. The prepared samples were characterized by various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis, Fourier transformed infrared (FT-IR) spectroscopy, photoluminescence spectroscopy and UV-Visible diffuse reflectance spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis confirmed the formation of zinc ferrites normal spinel-type structure with an average crystallite sizes in the range, 25.69 nm to 35.68 nm. The lattice parameters decreased as cobalt fraction was increased. The HR-SEM images showed nanoparticles are agglomerated. The estimated band gap energy value was found to decrease with an increase in cobalt content (1.87 to 1.62 eV). Broad visible emissions are observed in the photoluminescence spectra. A gradual increase in the coercivity and saturation magnetization (M(s)) were noted at relatively higher cobalt doping fractions.

Effect of Different Chromium Additions on the Microstructure and Mechanical Properties of Multipass Weld Joint of Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Kang, Dong Hoon; Lee, Hae Woo

2012-12-01

The correlation between the mechanical properties and ferrite volume fraction (approximately 40, 50, and 60 Ferrite Number [FN]) in duplex stainless steel weld metals were investigated by changing the Cr content in filler wires with a flux-cored arc-welding (FCAW) process. The interpass temperature was thoroughly maintained under a maximum of 423 K (150 °C), and the heat input was also sustained at a level under 15 KJ/cm in order to minimize defects. The microstructure examination demonstrated that the δ-ferrite volume fraction in the deposited metals increased as the Cr/Ni equivalent ratio increased, and consequently, chromium nitride (Cr2N) precipitation was prone to occur in the ferrite domains due to low solubility of nitrogen in this phase. Thus, more dislocations are pinned by the precipitates, thereby lowering the mobility of the dislocations. Not only can this lead to the strength improvement, but also it can accentuate embrittlement of the weld metal at subzero temperature. Additionally, the solid-solution strengthening by an increase of Cr and Mo content in austenite phase depending on the reduction of austenite proportion also made an impact on the increase of the tensile and yield strength. On the other hand, the impact test (at 293 K, 223 K, and 173 K [20 °C, -50 °C, and -100 °C]) showed that the specimen containing about 40 to 50 FN had the best result. The absorbed energy of about 40 to 50 J sufficiently satisfied the requirements for industrial applications at 223 K (-50 °C), while the ductile-to-brittle transition behavior exhibited in weldment containing 60 FN. As the test temperature decreased under 223 K (-50 °C), a narrow and deep dimple was transformed into a wide and shallow dimple, and a significant portion of the fracture surface was occupied by a flat cleavage facet with river patterns.

Microstructures and Mechanical Properties of a Wear-Resistant Alloyed Ductile Iron Austempered at Various Temperatures

NASA Astrophysics Data System (ADS)

Cui, Junjun; Chen, Liqing

2015-08-01

To further improve the mechanical performance of a new type of alloyed bainitic wear-resistant ductile iron, the effects of the various austempering temperatures have been investigated on microstructure and mechanical behaviors of alloyed ductile iron Fe-3.50C-1.95Si-3.58Ni-0.71Cu-0.92Mo-0.65Cr-0.36Mn (in weight percent). This alloyed ductile iron were firstly austenitized at 1123 K (850 °C) for 1 hour and then austempered in a salt bath at 548 K, 573 K, and 598 K (275 °C, 300 °C, and 325 °C) for 2 hours according to time-temperature-transformation diagram calculated by JMatPro software. The microstructures of austempered wear-resistant ductile irons consist of matrix of dark needle-like ferrite plus bright etching austenite and some amount of martensite and some dispersed graphite nodules. With increasing the austempering temperature, the amount of ferrite decreases in austempered ductile iron, while the amount of austenite and carbon content of austenite increases. There is a gradual decrease in hardness and increase in compressive strength with increasing austempering temperature. The increased austenite content and coarsened austenite and ferrite can lead to a hardness decrease as austempering temperature is increased. The increased compressive strength can be attributed to a decreased amount of martensitic transformation. The alloyed ductile iron behaves rather well wear resistance when the austempering is carried out at 598 K (325 °C) for 2 hours. Under the condition of wear test by dry sand/rubber wheel, the wear mechanisms of austempered ductile irons are both micro-cutting and plastic deformation.

Investigation of structural, morphological and electromagnetic properties of Mg0.25Mn0.25Zn0.5-xSrxFe2O4 ferrites

NASA Astrophysics Data System (ADS)

Rahaman, Md. D.; Nusrat, Tania; Maleque, Rumana; Hossain, A. K. M. Akther

2018-04-01

Polycrystalline Mg0.25Mn0.25Zn0.5-xSrxFe2O4 (0 ≤ x ≤ 0.20) ferrites were synthesized using the solid state reaction sintering at 1373 K and 1473 K for 4 h. The XRD patterns revealed the formation of single phase cubic spinel with Sr2FeO4 and SrFe12O19 as impurity phases. The decrement in the lattice parameter for Sr2+ substituted samples is attributed to the difference in ionic radii of cations. The crystallite size decreases with increase in Sr2+ content. Low frequency dielectric dispersion is attributed due to the Maxwell-Wagner interfacial polarization. The appearance of the peak in dielectric loss spectrum for x = 0.15 and 0.20 at 1373 K and x = 0.20 at 1473 K suggests the presence of relaxing dipoles. The loss peak shifts towards lower frequency side with Sr2+ content at 1373 K which is due to the strengthening of dipole-dipole interactions. The complex impedance spectra clearly revealed that the both grain and grain boundary effects on the electrical properties. A complex electric modulus spectrum indicates that a non-Debye type of conductivity relaxation exists. The saturation magnetization and remanence gradually decreases with Sr2+ substitution which may be due to the existence of non-magnetic phase in the space between the magnetic particles and the substitution of Zn2+ cation in Mg0.25Mn0.25Zn0.5Fe2O4 ferrite lattice by Sr2+ content. The permeability decreases significantly while the cut-off frequency increases with the Sr2+ content at 1373 K and decreases at 1473 K, obeying the Snoek's law. The decrease in permeability with Sr2+ content is attributed due to the decrease in magnetization because non-magnetic ions weaken the inter-site exchange interaction.

Incorporation of Cadmium and Nickel into Ferrite Spinel Solid Solution: X-ray Diffraction and X-ray Absorption Fine Structure Analyses.

PubMed

Su, Minhua; Liao, Changzhong; Chan, Tingshan; Shih, Kaimin; Xiao, Tangfu; Chen, Diyun; Kong, Lingjun; Song, Gang

2018-01-16

The feasibility of incorporating Cd and Ni in hematite was studied by investigating the interaction mechanism for the formation of Cd x Ni 1-x Fe 2 O 4 solid solutions (CNFs) from CdO, NiO, and α-Fe 2 O 3 . X-ray diffraction results showed that the CNFs crystallized into spinel structures with increasing lattice parameters as the Cd content in the precursors was increased. Cd 2+ ions were found to occupy the tetrahedral sites, as evidenced by Rietveld refinement and extended X-ray absorption fine structure analyses. The incorporation of Cd and Ni into ferrite spinel solid solution strongly relied on the processing parameters. The incorporation of Cd and Ni into the CNFs was greater at high x values (0.7 < x ≤ 1.0) than at low x values (0.0 ≤ x ≤ 0.7). A feasible treatment technique based on the investigated mechanism of CNF formation was developed, involving thermal treatment of waste sludge containing Cd and Ni. Both of these metals in the waste sludge were successfully incorporated into a ferrite spinel solid solution, and the concentrations of leached Cd and Ni from this solid solution were substantially reduced, stabilizing at low levels. This research offers a highly promising approach for treating the Cd and Ni content frequently encountered in electronic waste and its treatment residues.

Structural and magnetic properties of La–Co substituted Sr–Ca hexaferrites synthesized by the solid state reaction method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yujie; Liu, Xiansong, E-mail: xiansongliu@ahu.edu.cn; Jin, Dali

2014-11-15

Graphical abstract: The change of the remanence (B{sub r}) and intrinsic coercivity (H{sub cj}) with La content (x) and Co content (y) of hexagonal ferrite Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} magnets. - Highlights: • Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} hexaferrites were synthesized by the solid state reaction method. • B{sub r} continuously increases with increasing dopant contents. • H{sub cb}, H{sub cj} and (BH){sub max} for the magnets first increases and then decreases with an increase in the La–Co contents. - Abstract: Hexagonal ferrite Sr{sub 0.7−x}Ca{sub 0.3}La{sub x}Fe{sub 12−y}Co{sub y}O{sub 19} (x = 0.05–0.50; y =more » 0.04–0.40) magnetic powders and magnets were synthesized by the solid state reaction method. X-ray diffraction was employed to determine the phase compositions of the magnetic powders. There is a single magnetoplumbite phase in the magnetic powders with the substitution of La (0.05 ≤ x ≤ 0.15) and Co (0.04 ≤ y ≤ 0.12) contents. For the magnetic powders containing La (x ≥ 0.20) and Co (y ≥ 0.16), magnetic impurities begin to appear in the structure. A field emission scanning electron microscope was used to characterize the micrographs of the magnets. The magnets have formed hexagonal structures. Magnetic properties of the magnets were measured by a magnetic properties test instrument. The remanence continuously increases with increasing dopant contents. Whereas, the magnetic induction coercivity, intrinsic coercivity and maximum energy product for the magnets first increases and then decreases with an increase in the La–Co contents.« less

Synthesis and study of structural, microstructural and dielectric properties of Ce3+ doped Co-Ni ferrites for automotive applications

NASA Astrophysics Data System (ADS)

Srinivasamurthy, K. M.; Angadi, V. Jagadeesha; Kumar, P. Mohan; Nagaraj, B. S.; Deepthy, P. R.; Pasha, U. Mahaboob; Rudraswamy, B.

2018-05-01

Nano crystalline spinel ferrites of Co0.5Ni0.5CexFe2-xO4 (x=0.01, 0.015, 0.02, 0.025 and 0.03) was prepared by modified solution combustion method using a mixture of fuels for the first time. The influence of rare earth Ce3+ substitution at the Fe3+ site on the structural, microstructural and dielectric properties of Co0.5Ni0.5CexFe2-xO4 was investigated. The X-ray diffraction (XRD) studies confirmed the formation of monophasic nano crystalline samples without any secondary phases. The crystallite size decreases and density increases with the increases of Ce3+ contents. Surface morphology was studied through Scanning Electron Microscopy (SEM). Dielectric properties of these ferrites have been studied at room temperature using impedance analyzer in the frequency range up to 20 MHz. The effect of frequency and composition on dielectric constant (ɛ'), dielectric loss (tanδ) and ac conductivity (σac) have been discussed in terms of hopping of charge carriers (Fe2+↔Fe3+). The decrease in dielectric loss with frequency follows Debye's relaxation phenomena. Both the variation in tan loss and dielectric loss with frequency shows a similar. AC conductivity increases with the increases of frequency which directly proportional to concentration of Ce3+ ions follows Jonscher law. These Cerium doped Cobalt-nickel ferrites are very helpful for automotive applications.

Influence of heat input in electron beam process on microstructure and properties of duplex stainless steel welded interface

NASA Astrophysics Data System (ADS)

Zhang, Zhiqiang; Jing, Hongyang; Xu, Lianyong; Han, Yongdian; Zhao, Lei; Lv, Xiaoqing; Zhang, Jianyang

2018-03-01

The influence of heat input in electron beam (EB) process on microstructure, mechanical properties, and pitting corrosion resistance of duplex stainless steel (DSS) welded interface was investigated. The rapid cooling in EB welding resulted in insufficient austenite formation. The austenite mainly consisted of grain boundary austenite and intragranular austenite, and there was abundant Cr2N precipitation in the ferrite. The Ni, Mo, and Si segregation indicated that the dendritic solidification was primarily ferrite in the weld. The weld exhibited higher hardness, lower toughness, and poorer pitting corrosion resistance than the base metal. The impact fractures of the welds were dominated by the transgranular cleavage failure of the ferrite. The ferrite was selectively attacked because of its lower pitting resistance equivalent number than that of austenite. The Cr2N precipitation accelerated the pitting corrosion. In summary, the optimised heat input slightly increased the austenite content, reduced the segregation degree and ferrite texture intensity, decreased the hardness, and improved the toughness and pitting corrosion resistance. However, the effects were limited. Furthermore, optimising the heat input could not suppress the Cr2N precipitation. Taking into full consideration the microstructure and properties, a heat input of 0.46 kJ/mm is recommended for the EB welding of DSS.

Characterization of X80 and X100 Microalloyed Pipeline Steel Using Quantitative X-ray Diffraction

NASA Astrophysics Data System (ADS)

Wiskel, J. B.; Li, X.; Ivey, D. G.; Henein, H.

2018-06-01

Quantitative X-ray diffraction characterization of four (4) X80 and three (3) X100 microalloyed steels was undertaken. The effect of through-thickness position, processing parameters, and composition on the measured crystallite size, microstrain, and J index (relative magnitude of crystallographic texture) was determined. Microstructure analysis using optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron-backscattered diffraction was also undertaken. The measured value of microstrain increased with increasing alloy content and decreasing cooling interrupt temperature. Microstructural features corresponding to crystallite size in the X80 steels were both above and below the detection limit for quantitative X-ray diffraction. The X100 steels consistently exhibited microstructure features below the crystallite size detection limit. The yield stress of each steel increased with increasing microstrain. The increase in microstrain from X80 to X100 is also associated with a change in microstructure from predominantly polygonal ferrite to bainitic ferrite.

Thermal effects of laser marking on microstructure and corrosion properties of stainless steel.

PubMed

Švantner, M; Kučera, M; Smazalová, E; Houdková, Š; Čerstvý, R

2016-12-01

Laser marking is an advanced technique used for modification of surface optical properties. This paper presents research on the influence of laser marking on the corrosion properties of stainless steel. Processes during the laser beam-surface interaction cause structure and color changes and can also be responsible for reduction of corrosion resistance of the surface. Corrosion tests, roughness, microscopic, energy dispersive x-ray, grazing incidence x-ray diffraction, and ferrite content analyses were carried out. It was found that increasing heat input is the most crucial parameter regarding the degradation of corrosion resistance of stainless steel. Other relevant parameters include the pulse length and pulse frequency. The authors found a correlation between laser processing parameters, grazing incidence x-ray measurement, ferrite content, and corrosion resistance of the affected surface. Possibilities and limitations of laser marking of stainless steel in the context of the reduction of its corrosion resistance are discussed.

Synthesis, characterization and magnetic properties of MWCNTs decorated with Zn-substituted MnFe2O4 nanoparticles using waste batteries extract

NASA Astrophysics Data System (ADS)

Gabal, M. A.; Al-Harthy, E. A.; Al Angari, Y. M.; Abdel Salam, M.; Asiri, A. M.

2016-06-01

Mn1-xZnxFe2O4 (x=0.2-0.8) nano-crystals, synthesized from recycling of Zn-C batteries, were successfully self-assembled alongside multi-walled carbon nanotubes (MWCNTs) via an environmentally friend sucrose auto-combustion method. The effect of Zn-content on structural and magnetic properties were investigated and discussed. XRD revealed the formation of single-phase ferrites. DTA-TG experiment showed that the auto-combustion reaction finished at about 350 °C. TEM exhibited that the MWCNTs are well decorated with ferrite particles. Hysteresis loop measurements revealed ferromagnetic behavior, with saturation magnetization decrease by the addition of MWCNTs or increasing Zn-Content. The kinetics of methylene blue dye (MB) removal using MWCNTs/Mn0.8Zn0.2Fe2O nano-composite was investigated and discussed.

The Influence of Different Metal Ions on the Absorption Properties of Nano-Nickel Zinc Ferrite

PubMed Central

Ma, Zhijun; Mang, Changye; Weng, Xingyuan; Si, Liwei; Zhao, Haitao

2018-01-01

The hydrothermal method was used to dope different amounts of Co2+, Mn2+, and Cu2+ in nano-nickel zinc ferrite powder. X-ray diffraction (XRD), a scanning electron microscopy (TEM), and a vector network analyzer (VNA) were used to explore the influence of doping on particle size, morphology, and electromagnetic wave absorption performance. Pure nanometer cobalt nickel zinc ferrite phase was prepared using the hydrothermal method with an increasing Co2+ content. Results showed that the grain type structure changed from a spherical structure to an irregular quadrilateral structure with the average particle size increasing from 35 nm to 60 nm. The lattice constant increased from 0.8352 to 0.8404 nm with Co2+ doping. The increasing Co2+ can change the position of the absorption peak, increase the bandwidth of the absorber, and improve the performance of the materials in GHz low frequency. The doping ratio of Mn2+ can affect the size of the lattice constant, but nanocrystals are easy to reunite without improving the electromagnetic loss. However, the absorbance performance decreases. For the doping of Cu2+, there is an agglomeration phenomenon. When the doping quantity is 0.15, the absorbing wave performance becomes better. PMID:29641477

The Influence of Different Metal Ions on the Absorption Properties of Nano-Nickel Zinc Ferrite.

PubMed

Ma, Zhijun; Mang, Changye; Weng, Xingyuan; Zhang, Qi; Si, Liwei; Zhao, Haitao

2018-04-11

The hydrothermal method was used to dope different amounts of Co 2+ , Mn 2+ , and Cu 2+ in nano-nickel zinc ferrite powder. X-ray diffraction (XRD), a scanning electron microscopy (TEM), and a vector network analyzer (VNA) were used to explore the influence of doping on particle size, morphology, and electromagnetic wave absorption performance. Pure nanometer cobalt nickel zinc ferrite phase was prepared using the hydrothermal method with an increasing Co 2+ content. Results showed that the grain type structure changed from a spherical structure to an irregular quadrilateral structure with the average particle size increasing from 35 nm to 60 nm. The lattice constant increased from 0.8352 to 0.8404 nm with Co 2+ doping. The increasing Co 2+ can change the position of the absorption peak, increase the bandwidth of the absorber, and improve the performance of the materials in GHz low frequency. The doping ratio of Mn 2+ can affect the size of the lattice constant, but nanocrystals are easy to reunite without improving the electromagnetic loss. However, the absorbance performance decreases. For the doping of Cu 2+ , there is an agglomeration phenomenon. When the doping quantity is 0.15, the absorbing wave performance becomes better.

Structural and magnetic properties of calcium doped nickel ferrite nanoparticles by co-precipitation method

NASA Astrophysics Data System (ADS)

Vigneswari, T.; Raji, P.

2017-01-01

It is a truism that a sequence of calcium doped nickel ferrite (with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanoparticles are combined by co-precipitation technique. X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) scrutinize the formation of single-phase inverse spinel structure in all the compositions. The lattice framework increases with the increase in calcium concentration and it exhibits the development of unit cell. Crystallite size in the range of 22-34 nm is viewed and also augmented the level of calcium. The elemental composition of pure and calcium doped nickel ferrite has been procured from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Energy Dispersive X-ray analysis (EDX). It is interesting to note that the substitution of calcium increasingly exerts influence on the magnetic characteristics. These observations paved the way for the room temperature of magnetization measurements. The saturation magnetization and the experimental value of magnetic moment are noticed to enlarge initially up to x = 0.2, and then decrease incessantly with increase in the Ca content x. The increase and the decrease of saturation magnetization have widely been expounded by Neel's collinear two-sublattice model and Yafet-Kittel (Y-K) three-sub lattice model.

Effect of Annealing Temperature on Microstructure and Mechanical Properties of Hot-Dip Galvanizing DP600 Steel

NASA Astrophysics Data System (ADS)

Hai-yan, Sun; Zhi-li, Liu; Yang, Xu; Jian-qiang, Shi; Lian-xuan, Wang

Hot-dip galvanizing dual phase steel DP600 steel grade with low Si was produced by steel plant and experiments by simulating galvanizing thermal history. The microstructure was observed and analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effect of different annealing temperatures on the microstructure and mechanical properties of dual-phase steel was also discussed. The experimental results show that the dual-phase steel possesses excellent strength and elongation that match EN10346 600MPa standards. The microstructure is ferrite and martensite. TEM micrograph shows that white ferrite with black martensite islands inlay with a diameter of around 1um and the content of 14 18%. The volume will expand and phase changing take the form of shear transformation when ferrite converted to martensite. So there are high density dislocations in ferrite crystalline grain near martensite. The martensite content growing will be obvious along with annealing temperature going up. But the tendency will be weak when temperature high.

Nanoscale Engineering of Multiferroic Hybrid Composites for Micro- and Nano-scale Devices

DTIC Science & Technology

2012-09-14

saturation field of the nickel ferrite layer [7]. The ME coupling dE coefficient is conventionally defined as am =— (5), where E and H denote the electric...of Co- ferrite in granular composites measured at different electric fields Voltage(V) 0 To realize the first objective a series of NBT-CFO...sample with intermediate (30%) content of Co- ferrite [publications 3,5]. The effect of the electric field on ferromagnetic resonance curves is

Irradiation response of delta ferrite in as-cast and thermally aged cast stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhangbo; Lo, Wei-Yang; Chen, Yiren

To enable the life extension of Light Water Reactors (LWRs) beyond 60 years, it is critical to gain adequate knowledge for making conclusive predictions to assure the integrity of duplex stainless steel reactor components, e.g. primary pressure boundary and reactor vessel internal. Microstructural changes in the ferrite of thermally aged, neutron irradiated only, and neutron irradiated after being thermally aged cast austenitic stainless steels (CASS) were investigated using atom probe tomography. The thermal aging was performed at 400 °C for 10,000 h and the irradiation was conducted in the Halden reactor at ~315 °C to 0.08 dpa (5.6 × 10more » 19 n/cm 2 E > 1 MeV). Low dose neutron irradiation at a dose rate of 5 × 10 -9 dpa/s was found to induce spinod,al decomposition in the ferrite of as-cast microstructure, and further to enhance the spinodal decomposition in the thermally aged cast alloys. Regarding the G-phase precipitates, the neutron irradiation dramatically increases the precipitate size, and alters the composition of the precipitates with increased, Mn, Ni, Si and Mo and reduced Fe and Cr contents. Lastly, The results have shown that low dose neutron irradiation can further accelerate the degradation of ferrite in a duplex stainless steel at the LWR relevant condition.« less

Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

NASA Astrophysics Data System (ADS)

Zhong, X. C.; Guo, X. J.; Zou, S. Y.; Yu, H. Y.; Liu, Z. W.; Zhang, Y. F.; Wang, K. X.

2018-04-01

Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

Irradiation response of delta ferrite in as-cast and thermally aged cast stainless steel

DOE PAGES

Li, Zhangbo; Lo, Wei-Yang; Chen, Yiren; ...

2015-08-08

To enable the life extension of Light Water Reactors (LWRs) beyond 60 years, it is critical to gain adequate knowledge for making conclusive predictions to assure the integrity of duplex stainless steel reactor components, e.g. primary pressure boundary and reactor vessel internal. Microstructural changes in the ferrite of thermally aged, neutron irradiated only, and neutron irradiated after being thermally aged cast austenitic stainless steels (CASS) were investigated using atom probe tomography. The thermal aging was performed at 400 °C for 10,000 h and the irradiation was conducted in the Halden reactor at ~315 °C to 0.08 dpa (5.6 × 10more » 19 n/cm 2 E > 1 MeV). Low dose neutron irradiation at a dose rate of 5 × 10 -9 dpa/s was found to induce spinod,al decomposition in the ferrite of as-cast microstructure, and further to enhance the spinodal decomposition in the thermally aged cast alloys. Regarding the G-phase precipitates, the neutron irradiation dramatically increases the precipitate size, and alters the composition of the precipitates with increased, Mn, Ni, Si and Mo and reduced Fe and Cr contents. Lastly, The results have shown that low dose neutron irradiation can further accelerate the degradation of ferrite in a duplex stainless steel at the LWR relevant condition.« less

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

NASA Astrophysics Data System (ADS)

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.

Tensile properties and impact toughness of S30408 stainless steel and its welded joints at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Ding, Huiming; Wu, Yingzhe; Lu, Qunjie; Xu, Ping; Zheng, Jinyang; Wei, Lijun

2018-06-01

Designing a cryogenic pressure vessel based on the mechanical properties of the austenitic stainless steel (ASS) at its cryogenic operating temperature fully utilizes the potential of the material at low temperatures, resulting in lightweight and compact products. A series of tensile tests and impact tests were carried out in a wide range of 77-293 K, to investigate the mechanical properties of S30408 base metal (BM) and welded joints (WJ) at cryogenic temperatures. As the temperature decreases, yield stress (Rp0.2) and ultimate tensile stress (Rm) increase significantly thanks to the low-temperature strengthening effects. To estimate strengths at cryogenic temperatures, quadratic polynomial model was used to accurately predict the variations of Rp0.2 and Rm from 77 K to 293 K. As an important phase in the WJ, ferrite presents a radial pattern and an inhomogeneity in the WJ's cross-section. Due to the formation of ferrite in the WJ, the WJ has higher Rp0.2 and lower Rm , Charpy absorbed energy and lateral expansion compared with the BM. Strain-induced martensite transformation is an important role influencing the deformation of ASS at low temperatures. In this study, less martensite amount was measured in the weldment zone with higher Nickel equivalents which stabilize the austenite phase at cryogenic temperatures. Additionally, due to higher ferrite content and more precipitates forming, the SAW joints has lower Rm and impact toughness than PAW + GTAW joints. To ensure the structural integrity and safety, the PAW + GTAW method should be chosen and ferrite content be controlled.

Carbonate fuel cell anodes

DOEpatents

Donado, R.A.; Hrdina, K.E.; Remick, R.J.

1993-04-27

A molten alkali metal carbonates fuel cell porous anode of lithium ferrite and a metal or metal alloy of nickel, cobalt, nickel/iron, cobalt/iron, nickel/iron/aluminum, cobalt/iron/aluminum and mixtures thereof wherein the total iron content including ferrite and iron of the composite is about 25 to about 80 percent, based upon the total anode, provided aluminum when present is less than about 5 weight percent of the anode. A process is described for production of the lithium ferrite containing anode by slipcasting.

Carbonate fuel cell anodes

DOEpatents

Donado, Rafael A.; Hrdina, Kenneth E.; Remick, Robert J.

1993-01-01

A molten alkali metal carbonates fuel cell porous anode of lithium ferrite and a metal or metal alloy of nickel, cobalt, nickel/iron, cobalt/iron, nickel/iron/aluminum, cobalt/iron/aluminum and mixtures thereof wherein the total iron content including ferrite and iron of the composite is about 25 to about 80 percent, based upon the total anode, provided aluminum when present is less than about 5 weight percent of the anode. A process for production of the lithium ferrite containing anode by slipcasting.

Simple Magnetic Device Indicates Thickness Of Alloy 903

NASA Technical Reports Server (NTRS)

Long, Pin Jeng; Rodriguez, Sergio; Bright, Mark L.

1995-01-01

Handheld device called "ferrite indicator" orginally designed for use in determining ferrite content of specimen of steel. Placed in contact with specimen and functions by indicating whether magnet attracted more strongly to specimen or to calibrated reference sample. Relative strength of attraction shows whether alloy overlay thinner than allowable.

Structural and electromagnetic characterization of Co-Mn doped Ni-Sn ferrites fabricated via micro-emulsion route

NASA Astrophysics Data System (ADS)

Ali, Rajjab; Azhar Khan, Muhammad; Manzoor, Alina; Shahid, Muhammad; Farooq Warsi, Muhammad

2017-11-01

Ni0.5Sn0.5CoxMnxFe2-2xO4 ferrites with x = 0.0-0.8 have been prepared by the micro-emulsion method, using CTAB as a surfactant material. X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and vibrational sample magnetometer (VSM) were used to investigate the effects of Co and Mn substitutions on cationic distribution, crystallite size, lattice constant, spectral, magnetic and dielectric properties. Lattice constant and crystallite size were found to increase from 7.4 to 9.25 Å and from 11.8 to 19.7 nm respectively with increasing substitution of Co and Mn ions. Saturation magnetization (MS) gradually increased from 20.5 to 47.6 emu/g with increase in the value of x. However, Coercivity increased from 152.7 to 462.4 Oe up to x = 0.4 and then it decreased thereafter. The dielectric constant, complex dielectric constant and tan loss (tanδ) were observed to decrease with increase in frequency, depicting the semiconductor behavior of the ferrites. Dc resistivity was observed to decrease considerably upon addition of Co and Mn content. The outcome for the tunable magnetic properties and achieved modification of the synthesized nanocrystallites may be chosen for tremendous applications; such as miniaturized memory devices that are based on the energy storage principles and capacitive components.

Delta-Ferrite Distribution in a Continuous Casting Slab of Fe-Cr-Mn Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Chen, Chao; Cheng, Guoguang

2017-10-01

The delta-ferrite distribution in a continuous casting slab of Fe-Cr-Mn stainless steel grade (200 series J4) was analyzed. The results showed that the ferrite fraction was less than 3 pct. The "M" type distribution was observed in the thickness direction. For the distribution at the centerline, the maximum ferrite content was found in the triangular zone of the macrostructure. In addition, in this zone, the carbon and sulfur were severely segregated. Furthermore, an equilibrium solidification calculation by Thermo-Calc® software indicates that the solidification mode of the composition in this triangular zone is the same as the solidification mode of the averaged composition, i.e., the FA (ferrite-austenite) mode. None of the nickel-chromium equivalent formulas combined with the Schaeffler-type diagram could predict the ferrite fraction of the Cr-Mn stainless steel grade in a reasonable manner. The authors propose that more attention should be paid to the development of prediction models for the ferrite fraction of stainless steels under continuous casting conditions.

Structural, magnetic and spectral properties of Gd and Dy co-doped dielectrically modified Co-Ni (Ni0.4Co0.6Fe2O4) ferrites

NASA Astrophysics Data System (ADS)

Ditta, Allah; Khan, Muhammad Azhar; Junaid, Muhammad; Khalil, R. M. Arif; Warsi, Muhammad Farooq

2017-02-01

Gadolinium (Gd) and Dysprosium (Dy) co-doped Ni-Co (Ni0.4Co0.6Fe2O4) 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/cm3) 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-1 (υ2) to 600 cm-1 (υ1) 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.

Humidity effects on adhesion of nickel-zinc ferrite in elastic contact with magnetic tape and itself

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Kusaka, T.; Maeda, C.

1985-01-01

The effects of humidity on the adhesion of Ni-Zn ferrite and magnetic tape in elastic contact with a Ni-Zn ferrite hemispherical pin in moist nitrogen were studied. Adhesion was independent of normal load in dry, humid, and saturated nitrogen. Ferrites adhere to ferrites in a saturated atmosphere primarily from the surface tension effects of a thin film of water adsorbed on the ferrite surfaces. The surface tension of the water film calculated from the adhesion results was 48 times 0.00001 to 56 times 0.00001 N/cm; the accepted value for water is 72.7 x 0.00001 N/cm. The adhesion of ferrite-ferrite contacts increased gradually with increases in relative humidity to 80 percent, but rose rapidly above 80 percent. The adhesion at saturation was 30 times or more greater than that below 80 percent relative humidity. Although the adhesion of magnetic tape - ferrite contacts remained low below 40 percent relative humidity and the effect of humidity was small, the adhesion increased considerably with increasing relative humidity above 40 percent. The changes in adhesion of elastic contacts were reversible on humidifying and dehumidifying.

High Temperature Strengthening in 12Cr-W-Mo Steels by Controlling the Formation of Delta Ferrite

NASA Astrophysics Data System (ADS)

Wang, Shushen; Chang, Li; Lin, Deye; Chen, Xiaohua; Hui, Xidong

2014-09-01

Novel 12Cr-W-Mo-Co heat resistance steels (HRSs) with excellent mechanical properties have been developed for ultra-supercritical (USC) applications above 923 K (650 °C). The thermal analysis of the present steels indicates that the remelting temperature of secondary phases is increased by Co alloying, resulting in the improvement of microstructural stability. Delta ferrite in these HRSs is completely suppressed as the content of Co is increased up to 5 pct. The room temperature tensile strength (TS), yield strength (YS), and the elongation (EL) of the HRS with 5 pct Co reach 887.9, 652.6 MPa, and 21.07 pct, respectively. At 948 K (675 °C), the TS and YS of the HRS with 5 pct Co attain 360 and 290 MPa, respectively, which are higher than those of T/P122 steel by 27.4 and 22.1 pct, respectively. TEM study of the microstructure confirmed that the strengthening effects for these 12Cr-W-Mo-Co HRSs are attributed to the suppression of delta ferrite, the formation of fine martensitic laths with substructure, dislocation networks and walls, and the precipitation of second nanoscale phases.

Boride Formation Induced by pcBN Tool Wear in Friction-Stir-Welded Stainless Steels

NASA Astrophysics Data System (ADS)

Park, Seung Hwan C.; Sato, Yutaka S.; Kokawa, Hiroyuki; Okamoto, Kazutaka; Hirano, Satoshi; Inagaki, Masahisa

2009-03-01

The wear of polycrystalline cubic boron nitride (pcBN) tool and its effect on second phase formation were investigated in stainless steel friction-stir (FS) welds. The nitrogen content and the flow stress were analyzed in these welds to examine pcBN tool wear. The nitrogen content in stir zone (SZ) was found to be higher in the austenitic stainless steel FS welds than in the ferritic and duplex stainless steel welds. The flow stress of austenitic stainless steels was almost 1.5 times larger than that of ferritic and duplex stainless steels. These results suggest that the higher flow stress causes the severe tool wear in austenitic stainless steels, which results in greater nitrogen pickup in austenitic stainless steel FS welds. From the microstructural observation, a possibility was suggested that Cr-rich borides with a crystallographic structure of Cr2B and Cr5B3 formed through the reaction between the increased boron and nitrogen and the matrix during FS welding (FSW).

Effects of Mn and Al on the Intragranular Acicular Ferrite Formation in Rare Earth Treated C-Mn Steel

NASA Astrophysics Data System (ADS)

Song, Mingming; Song, Bo; Yang, Zhanbing; Zhang, Shenghua; Hu, Chunlin

2017-07-01

The influence of Al, Mn and rare earth (RE) on microstructure of C-Mn steel was investigated. The capacities of different RE inclusions to induce intragranular acicular ferrite (AF) formation were compared. Result shows that RE treatment could make C-Mn steel from large amounts of intragranular AF. Al killed is detrimental to the formation of intragranular AF in RE-treated C-Mn steel. An upper bainite structure would replace the AF when Al content increased to 0.027 mass %. The optimal Mn content to form AF is about 0.75-1.31 mass %. The effective RE inclusion which could induce AF nucleation is La2O2S. When patches of MnS are attached on the surface of La2O2S inclusion, AF nucleation capacity of RE-containing inclusion could enlarge obviously. The existence of manganese-depleted zone and low lattice misfit would be the main reason of La-containing inclusion inducing AF nucleation in C-Mn steel.

[Synthesis and spectral characteristic of Ga-Fe3O4 at room temperature].

PubMed

Wang, Jing; Deng, Tong; Yang, Cai-Qin; Lin, Yu-Long; Wang, Wei; Wu, Hai-Yan

2008-03-01

Gallium bearing ferrites with different gallium content were synthesized by oxidation of ferrous and gallium ions under alkaline condition and room temperature. The samples were subjected to IR, XRD, Mossbauer spectral analysis and magnetization characterization. The results indicated that the green-rust intermediate phase would be produced during the procedure of Ga-Fe3O4 formation, and the green-rust intermediate phase was converted to ferrites with spinel structure during the drying under hot-N2 atmosphere. With the introduction of gallium into the spinel structure, the interplanar crystal spacing of the spinel structure decreased, as indicated from XRD spectra, and the lattice vibration of M(T)-O-M(o) moved to the high-frequency resulting from IR spectra. A small amount gallium introduction entered the tetrahedral sites preferentially rather than the octahedral sites, and increasing gallium introduction would enhance the occupation of octahedral sites. Furthermore, a small content of gallium in the initial solution could prevent the formation of non-magnetic Fe2O3.

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

NASA Astrophysics Data System (ADS)

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).

Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

NASA Astrophysics Data System (ADS)

Kim, Young Min; Shin, Sang Yong; Lee, Hakcheol; Hwang, Byoungchul; Lee, Sunghak; Kim, Nack J.

2007-08-01

This study is concerned with the effects of V and Mo addition on tensile and Charpy impact properties of API X70 linepipe steels. Twelve kinds of steel specimens were produced by varying V and Mo additions and rolling conditions. The addition of V and Mo promoted the formation of acicular ferrite (AF), banitic ferrite (BF), and martensite-austenite (MA) constituents, while suppressing the formation of polygonal ferrite (PF) or pearlite (P). The tensile test results indicated that the tensile strength of the specimens rolled in the two-phase region increased with the addition of V and Mo, while the yield strength did not vary much in these specimens except the water-cooled specimens, which showed the increased yield strength with addition of Mo. The tensile strength of specimens rolled in the single-phase region followed by water cooling increased with increasing V and Mo contents. The yield strength, however, did not vary much with increasing V content or with addition of Mo to the low-V alloy. In these specimens, a substantial increase in the strengths was achieved only when Mo was added to the high-V alloy. The specimens rolled in the single-phase region had higher upper-shelf energy (USE) and lower ductile-brittle transition temperature (DBTT) than the specimens rolled in the two-phase region, because their microstructures were composed of AF and fine PF. According to the electron backscatter diffraction (EBSD) analysis data, the effective grain size in AF was determined by crystallographic packets composed of a few fine grains having similar orientations. Thus, the decreased DBTT in the specimens rolled in the single-phase region could be explained by the decrease in the overall effective grain size due to the presence of AF having smaller effective grain size.

Magnetic, Electric and Optical Properties of Mg-Substituted Ni-Cu-Zn Ferrites

NASA Astrophysics Data System (ADS)

Kabbur, S. M.; Ghodake, U. R.; Kambale, Rahul C.; Sartale, S. D.; Chikhale, L. P.; Suryavanshi, S. S.

2017-10-01

The Ni0.25- x Mg x Cu0.30Zn0.45Fe2O4 ( x = 0.00 mol, 0.05 mol, 0.10 mol, 0.15 mol, 0.20 mol and 0.25 mol) magnetic oxide system was prepared by a sol-gel auto-combustion method using glycine as a fuel. X-ray diffraction study reveals the formation of pure spinel lattice symmetry along with the presence of a small fraction of unreacted Fe2O3 phase as a secondary phase due to incomplete combustion reaction between fuel and oxidizer. The lattice constant ( a) was found to decrease with the increase of Mg2+ content; the average crystallite size ( D) is observed in the range of 26.78-33.14 nm. At room temperature, all the samples show typical magnetic hysteresis loops with the decrease of magnetic moment ( n B) of Ni-Cu-Zn ferrites with the increase of Mg2+ content. The intrinsic vibrational absorption bands for the tetrahedral and octahedral sites of the spinel structure were confirmed by infrared (IR) spectroscopy. The optical parameters such as refractive index ( η), velocity of IR waves ( v) and jump rates ( J 1, J 2, J) were studied and found to be dependent on the variation of the lattice constant. The Curie temperature ( T c) of Ni-Cu-Zn mixed ferrite was found to decrease with Mg2+ addition. The composition x = 0.15 mol.% with a low dielectric loss tangent of 2% seems to have potential for multilayer chip inductor applications at a wide range of frequencies.

Electron Backscatter Diffraction Analysis of Joints Between AISI 316L Austenitic/UNS S32750 Dual-Phase Stainless Steel

NASA Astrophysics Data System (ADS)

Shamanian, Morteza; Mohammadnezhad, Mahyar; Amini, Mahdi; Zabolian, Azam; Szpunar, Jerzy A.

2015-08-01

Stainless steels are among the most economical and highly practicable materials widely used in industrial areas due to their mechanical and corrosion resistances. In this study, a dissimilar weld joint consisting of an AISI 316L austenitic stainless steel (ASS) and a UNS S32750 dual-phase stainless steel was obtained under optimized welding conditions by gas tungsten arc welding technique using AWS A5.4:ER2594 filler metal. The effect of welding on the evolution of the microstructure, crystallographic texture, and micro-hardness distribution was also studied. The weld metal (WM) was found to be dual-phased; the microstructure is obtained by a fully ferritic solidification mode followed by austenite precipitation at both ferrite boundaries and ferrite grains through solid-state transformation. It is found that welding process can affect the ferrite content and grain growth phenomenon. The strong textures were found in the base metals for both steels. The AISI 316L ASS texture is composed of strong cube component. In the UNS S32750 dual-phase stainless steel, an important difference between the two phases can be seen in the texture evolution. Austenite phase is composed of a major cube component, whereas the ferrite texture mainly contains a major rotated cube component. The texture of the ferrite is stronger than that of austenite. In the WM, Kurdjumov-Sachs crystallographic orientation relationship is found in the solidification microstructure. The analysis of the Kernel average misorientation distribution shows that the residual strain is more concentrated in the austenite phase than in the other phase. The welding resulted in a significant hardness increase in the WM compared to initial ASS.

Effect of composition and austenite deformation on the transformation characteristics of low-carbon and ultralow-carbon microalloyed steels

NASA Astrophysics Data System (ADS)

Cizek, P.; Wynne, B. P.; Davies, C. H. J.; Muddle, B. C.; Hodgson, P. D.

2002-05-01

Deformation dilatometry has been used to simulate controlled hot rolling followed by controlled cooling of a group of low- and ultralow-carbon microalloyed steels containing additions of boron and/or molybdenum to enhance hardenability. Each alloy was subjected to simulated recrystallization and nonrecrystallization rolling schedules, followed by controlled cooling at rates from 0.1 °C/s to about 100 °C/s, and the corresponding continuous-cooling-transformation (CCT) diagrams were constructed. The resultant microstructures ranged from polygonal ferrite (PF) for combinations of slow cooling rates and low alloying element contents, through to bainitic ferrite accompanied by martensite for fast cooling rates and high concentrations of alloying elements. Combined additions of boron and molybdenum were found to be most effective in increasing steel hardenability, while boron was significantly more effective than molybdenum as a single addition, especially at the ultralow carbon content. Severe plastic deformation of the parent austenite (>0.45) markedly enhanced PF formation in those steels in which this microstructural constituent was formed, indicating a significant effective decrease in their hardenability. In contrast, in those steels in which only nonequilibrium ferrite microstructures were formed, the decreases in hardenability were relatively small, reflecting the lack of sensitivity to strain in the austenite of those microstructural constituents forming in the absence of PF.

Long term high temperature oxidation characteristics of La and Cu alloyed ferritic stainless steels for solid oxide fuel cell interconnects

NASA Astrophysics Data System (ADS)

Swaminathan, Srinivasan; Lee, Young-Su; Kim, Dong-Ik

2016-09-01

To ensure the best performance of solid oxide fuel cell metallic interconnects, the Fe-22 wt.% Cr ferritic stainless steels with various La contents (0.006-0.6 wt.%) and Cu addition (1.57 wt.%), are developed. Long-term isothermal oxidation behavior of these steels is investigated in air at 800 °C, for 2700 h. Chemistry, morphology, and microstructure of the thermally grown oxide scale are examined using XPS, SEM-EDX, and XRD techniques. Broadly, all the steels show a double layer consisting of an inner Cr2O3 and outer (Mn, Cr)3O4. Distinctly, in the La-added steels, binary oxides of Cr, Mn and Ti are found at the oxide scale surface together with (Mn, Cr)3O4. Furthermore, all La-varied steels possess the metallic Fe protrusions along with discontinuous (Mn, Cr)3O4 spinel zones at the oxide scale/metal interface and isolated precipitates of Ti-oxides in the underlying matrix. Increase of La content to 0.6 wt.% is detrimental to the oxidation resistance. For the Cu-added steel, Cu is found to segregate strongly at the oxide scale/metal interface which inhibits the ingress of oxygen thereby suppressing the subscale formation of (Mn, Cr)3O4. Thus, Cu addition to the Fe-22Cr ferritic stainless steels benefits the oxidation resistance.

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

NASA Astrophysics Data System (ADS)

Wang, Sea-Fue; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

2015-11-01

In this study, the effects of grain size and the addition of CaCO3 on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 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 CaCO3 densified the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics at 1075 °C. In the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO3 content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe2CaO4 was observed, together with the disappearance of the second phase CuO. The grain size of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO3 content increased from 0 to 5 wt%. Initially rising to 807 after CaCO3 addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO3 content increased. The bending strength grew linearly with the CaCO3 content and reached twice the value for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with an addition of 5.0 wt% CaCO3. The initial permeability of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic decreased substantially from 402 to 103 as the addition of CaCO3 in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic was maximized at 95 for 1.0 wt% CaCO3 addition.

Strengthening mechanisms and mechanical properties of high interstitial stainless steel for drill collar and its corrosion resistance

NASA Astrophysics Data System (ADS)

Lee, Eunkyung

Two types (CN66, CN71) of high interstitial stainless steels (HISSs) were investigated for down-hole application in sour gas well environments. Experiments were designed to identify factors that have a significant effect on mechanical properties. The three factors examined in the study were carbon + nitrogen content (0.66 or 0.71 mass %), cooling rate in quenching (air or water), and heat treatment time (2 or 4 hours). The results showed that the cooling rate, C+N content, and the two-factor interaction of these variables have a significant effect on the mechanical properties of HISSs. Based on the statistical analysis results on mechanical properties, extensive analyses were undertaken to understand the strengthening mechanisms of HISSs. Microstructure analysis revealed that a pearlite phase with a high carbide and/or nitride content is dissolved in the matrix by heat treatment at 1,200 ºC which is considered the dissolution to increase the concentration of interstitial elements in steels. The distribution of elements in HISSs was investigated by quantitative mapping using EPMA, which showed that the high carbon concentration (carbide/cementite) area was decreased by increases in both the cooling rate and C+N content. The ferrite volume fraction of each specimen is increased by an increase in cooling rate, because there is insufficient time to form austenite from retained ferrite. The lattice expansion of HISS was investigated by the calculation of lattice parameters under various conditions, and these investigations confirm the solid solution strengthening effect on HISSs. CN66 with heat treatment at fast cooling has the highest wear resistance; a finding that was consistent with hardening mechanisms that occur due to an increased ferrite volume fraction. In addition, precipitates on the surface and the chemical bonding of chromium were investigated. As the amount of CrN bonding increased, the wear resistance also increased. This study also assessed the corrosion resistance properties of HISSs and shows that the alloys developed in the present study effectively resist attack by sour acid gas and salt water by immersion tests using sour-brine environment and salt water. In addition, electrochemical polarization tests show that the corrosion pitting potential of the heat treated HISSs in sodium chloride solution is the highest among the benchmark alloys. This result shows that this alloy resists corrosion well under the high temperature and high pressure conditions in the presence of high-pressure H2S and CO 2 sour gas well environments.

Study the effect of Gd3+ incorporation into nanocrystalline (Ni-Ti) substituted Mn-Zn ferrites on its structure and functional properties

NASA Astrophysics Data System (ADS)

Rady, K. E.; Shams, M. S.

2017-03-01

Ferrite samples with general chemical formula Mn0.9Zn0.1Ni0.05Ti0.05GdtFe1.9-tO4; (0.0≤ t≤0.05; step 0.01) were prepared using solid state reaction technique and the effect of Gd3+ ions incorporation on its physical properties has been studied. From the obtained results, XRD analysis reveals that the samples have a cubic spinel single phase structure for 0.0≤ t≤0.02; while for t≥0.03 a small peak of secondary phase (Gd3Fe5O12) appears and becomes more noticeable with increasing Gd content. The lattice parameter (a) of the prepared samples was found to be initially increases and then decreases with increasing Gd content which may be attributed to the difference in the ionic radii of the cations involved and the solubility limit of Gd3+ ions. The crystallite size of the samples was estimated using Scherrer's equation and ranged from 96 nm to 107 nm. A vibrating sample magnetometer (VSM) was used at room temperature in order to study the effect of Gd content on the magnetic hysteresis parameters of the prepared ferrites such as saturation magnetization and coercivity. DC molar magnetic susceptibility (χM) for the prepared samples was measured using Faraday's method as a function of temperature and the Curie temperature was calculated from the magnetic susceptibility measurements. Also the DC resistivity of the samples was measured at room temperature. The obtained results show that, the substitution by Gd3+ ions improves the electrical properties of the samples by increasing it DC electrical resistivity by 118% and consequently decreases it eddy current loss while the saturation magnetization slightly decreased by 14% only. The sample of t=0.01 shows a high dc magnetic susceptibility, high saturation magnetization (43.1 emu/g), high electric resistivity 12×103 Ω.m and high Curie temperature (496 K), which is useful in some technological applications such as transformer and inductor cores.

Synthesis, microstructure, and magnetic properties of monosized Mn x Zn y Fe3 − x − y O4 ferrite nanocrystals

PubMed Central

2013-01-01

We report the synthesis and characterization of ferrite nanocrystals which exhibit high crystallinity and narrow size distributions. The three types of samples including Zn ferrite, Mn ferrite, and Mn-Zn ferrite were prepared via a non-aqueous nanoemulsion method. The structural, chemical, and magnetic properties of the nanocrystals are analyzed by transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and physical property measurement system. The characterization indicates that the three types of ferrite nanocrystals were successfully produced, which show well-behaved magnetic properties, ferrimagnetism at 5 K and superparamagnetism at 300 K, respectively. In addition, the magnetization value of the ferrites increases with the increasing concentration of Mn. PMID:24344630

Synthesis and characterization of structural and magnetic properties of polyaniline-cobalt ferrite (PA-CoFe) nanocomposites

NASA Astrophysics Data System (ADS)

Thakur, Sonika; Kaur, Parminder; Singh, Lakhwant

2018-05-01

The growing interest in the investigation of the properties of modified conducting polymers stems from their potential applications in various fields such as in sensing and catalytic devices. The present work reports the modification of conducting polymer polyaniline with cobalt ferrite (CoFe) nanoparticles, where CoFe nanoparticles are added in different successive weight percents. The composite samples were synthesized by in-situ chemical oxidative polymerization technique. The density of the samples has been found to increase with an increase in the CoFe content. Structural analysis of the synthesized sample has been done using X-ray diffraction studies. Perusal of the hysteresis curves of the prepared samples depicts that the introduction of CoFe into the polymer matrix leads to enhancement in the ferromagnetic behavior of the synthesized samples, suggesting that these nanocomposites have excellent microwave absorbing capacity.

Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

NASA Astrophysics Data System (ADS)

Verma, Jagesvar; Taiwade, Ravindra V.

2016-11-01

This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

Advanced characterization techniques in understanding the roles of nickel in enhancing strength and toughness of submerged arc welding high strength low alloy steel multiple pass welds in the as-welded condition

NASA Astrophysics Data System (ADS)

Sham, Kin-Ling

Striving for higher strength along with higher toughness is a constant goal in material properties. Even though nickel is known as an effective alloying element in improving the resistance of a steel to impact fracture, it is not fully understood how nickel enhances toughness. It was the goal of this work to assist and further the understanding of how nickel enhanced toughness and maintained strength in particular for high strength low alloy (HSLA) steel submerged arc welding multiple pass welds in the as-welded condition. Using advanced analytical techniques such as electron backscatter diffraction, x-ray diffraction, electron microprobe, differential scanning calorimetry, and thermodynamic modeling software, the effect of nickel was studied with nickel varying from one to five wt. pct. in increments of one wt. pct. in a specific HSLA steel submerged arc welding multiple pass weldment. The test matrix of five different nickel compositions in the as-welded and stress-relieved condition was to meet the targeted mechanical properties with a yield strength greater than or equal to 85 ksi, a ultimate tensile strength greater than or equal to 105 ksi, and a nil ductility temperature less than or equal to -140 degrees F. Mechanical testing demonstrated that nickel content of three wt. pct and greater in the as-welded condition fulfilled the targeted mechanical properties. Therefore, one, three, and five wt. pct. nickel in the as-welded condition was further studied to determine the effect of nickel on primary solidification mode, nickel solute segregation, dendrite thickness, phase transformation temperatures, effective ferrite grain size, dislocation density and strain, grain misorientation distribution, and precipitates. From one to five wt. pct nickel content in the as-welded condition, the primary solidification was shown to change from primary delta-ferrite to primary austenite. The nickel partitioning coefficient increased and dendrite/cellular thickness was refined. Austenite decomposition temperatures into different ferrite products were also suppressed to refine the effective ferrite grain size with increasing nickel. Finally, dislocation density and strain increased and a more preferred orientation behavior was observed. At five wt. pct nickel, a precipitate in the form of MnNi3 or FeNi3 was observed. Its presence in both inter and intragranular regions enhanced strength and toughness by limiting the ferrite grain size and precipitation strengthening.

Effects of Manganese Content on Solidification Structures, Thermal Properties, and Phase Transformation Characteristics in Fe-Mn-Al-C Steels

NASA Astrophysics Data System (ADS)

Yang, Jian; Wang, Yu-Nan; Ruan, Xiao-Ming; Wang, Rui-Zhi; Zhu, Kai; Fan, Zheng-Jie; Wang, Ying-Chun; Li, Cheng-Bin; Jiang, Xiao-Fang

2015-04-01

To assist developments of the continuous-casting technology of Fe-Mn-Al-C steels, the solidification structures and the thermal properties of Fe-Mn-Al-C steel ingots with different manganese contents have been investigated and the phase transformation characteristics have been revealed by FactSage (CRCT-ThermFact Inc., Montréal, Canada). The results show that the thermal conductivity of the 0Mn steel is the highest, whereas the thermal conductivity of the 8Mn steel is slightly higher than that of the 17Mn steel. Increasing the manganese content promotes a columnar solidification structure and coarse grains in steel. With the increase of manganese content, the mass fraction of austenite phase is increased. Finally, a single austenite phase is formed in the 17Mn steel. The mean thermal expansion coefficients of the steels are in the range from 1.3 × 10-5 to 2.3 × 10-5 K-1, and these values increase with the increase of manganese content. The ductility of the 17Mn steel and the 8Mn steel are higher than 40 pct in the temperature range from 873 K to 1473 K (600 °C to 1200 °C), and the cracking during the straightening operation should be avoided. However, the ductility of the 0Mn steel is lower than 40 pct at 973 K and 1123 K (700 °C and 850 °C), which indicates that the temperature of the straightening operation during the continuous-casting process should be above 1173 K (900 °C). Manganese has the effect of enlarging the austenite phase region and reducing the δ-ferrite phase region and α-ferrite phase region. At the 2.1 mass pct aluminum level, the precipitate temperature of AlN is high. Thus, the formed AlN is too coarse to deteriorate the hot ductility of steel.

Low activation ferritic alloys

DOEpatents

Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

1986-01-01

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Low activation ferritic alloys

DOEpatents

Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

1985-02-07

Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

Investigation on the structures and magnetic properties of carbon or nitrogen doped cobalt ferrite nanoparticles.

PubMed

Cao, Derang; Pan, Lining; Li, Jianan; Cheng, Xiaohong; Zhao, Zhong; Xu, Jie; Li, Qiang; Wang, Xia; Li, Shandong; Wang, Jianbo; Liu, Qingfang

2018-05-21

Carbon or nitrogen doped cobalt ferrite nanoparticles were synthesized in the air by a facile calcination process. X-ray diffraction, mapping, X-ray photoelectron spectroscopy, and mössbauer spectra results indicate that the nonmetal elements as the interstitial one are doped into cobalt ferrite nanoparticles. The morphologies of doped cobalt ferrite nanoparticles change from near-spherical to irregular cubelike shapes gradually with the increased carbon or nitrogen concentration, and their particles sizes also increase more than 200 nm. Furthermore, the saturation magnetization of carbon doped cobalt ferrite is improved. Although the saturation magnetization of N-doped cobalt ferrite is not enhanced obviously due to the involved hematite, they also do not drop drastically. The results reveal an approach to synthesize large scale ferrite nanoparticles, and improve the magnetic properties of ferrite nanoparticles, and also provide the potential candidates to synthesis co-doped functional magnetic materials.

Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Y.; Alexandreanu, B.; Natesan, K.

2014-11-01

Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3more » were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.« less

Ferrite grain refinement in low carbon Cu–P–Cr–Ni–Mo weathering steel at various temperatures in the (α + γ) region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chunling, E-mail: zhangchl@ysu.edu.cn; School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300401; Zhang, Mengmeng

2016-03-15

Self-designed Cu–P–Cr–Ni–Mo weathering steel was subjected to compression test to determine the mechanism of ferrite grain refinement from 750 °C to 925 °C. Optical microscopic images showed that ferrite grain size declined, whereas the ferrite volume fraction increased with increasing compression temperature. Electron backscatter diffraction patterns revealed that several low-angle boundaries shifted to high-angle boundaries, thereby generating fine ferrite grains surrounded by high-angle boundaries. Numerous low-angle boundaries were observed within ferrite grains at 750 °C, which indicated the existence of pre-eutectoid ferrite. Results showed that ferrite grain refinement could be due to continuous dynamic recrystallization at 750 °C and 775more » °C, and deformation-induced ferrite transformation could be the main mechanism at 800 °C and 850 °C. Fine equiaxed ferrite grains with size ranging from 1.77 μm to 2.69 μm were produced in the (α + γ) dual-phase region. - Graphical abstract: There is a close relationship between the microstructure evolution and flow curves during deformation. Fine equiaxed ferrite grains with size ranging from 1.77 μm to 2.69 μm were achieved in the (α + γ) dual-phase region. Ferrite grain refinement could be due to continuous dynamic recrystallization at 750 °C and 775 °C, and deformation-induced ferrite transformation at 800 °C and 850 °C. The occurrence of deformation-induced ferrite transformation and continuous dynamic recrystallization can be monitored by analysis of flow curves and microstructures. Deformation-induced ferrite transformation leads to the dynamic softening in flow curve when temperature just below A{sub r3}, while the dynamic softening in flow curve is ferrite continuous dynamic recrystallization (Special Fig. 5b). - Highlights: • Compression deformation was operated at temperatures from 750 °C to 925 °C at a strain rate of 0.1 s–1, and a strain of 1.2. • Fine equiaxed ferrite grains of ~1.77–2.19 μm were obtained at 750 °C and 775 °C via continuous dynamic recrystallization. • Ferrite grain size of ~2.31–2.69 μm at 800 °C and 850 °C can be obtained by deformation-induced ferrite transformation. • With decreasing deformation temperature the average grain size of ferrite decreased while volume fraction increased. • Ferrite refinement was from deformation-induced ferrite to continuous dynamic recrystallization as temperature reduced.« less

An influence of a Glass Braze Composition on the Properties of Li-Ti Ferrite Joints

NASA Astrophysics Data System (ADS)

Lin, Panpan; Lin, Tiesong; He, Peng; Sekulic, Dusan P.; Zhao, Mengyuan; Wang, Shulei

2017-04-01

The influence of the chemical composition of Bi2O3-B2O3-SiO2-ZnO glass brazes on (i) the microstructure, (ii) the mechanical and (iii) the dielectric properties of Li-Ti ferrite joints was systematically investigated. The Bi5(Ti3Fe)O15 whisker and a white block phase consisting of Bi12SiO2 and Bi24B2O39 were observed in the joints of Li-Ti ferrite/Bi25-Ba and Li-Ti ferrite/glass brazes, respectively, containing a higher content of Bi2O3. No crystalline phase was detected in the Li-Ti ferrite/Bi25 and Li-Ti ferrite/Bi20 joints. The joint strength reached the maximum of 48 MPa in the Li-Ti ferrite/Bi25-Ba couples. It is assumed that this is mainly due to the strengthening effect of Bi5(Ti3Fe)O15 whiskers. The bonding temperature (700°C) had little effect on the dielectric properties of Li-Ti ferrite. Moreover, compared to the Bi25-Ba glass brazes, the Bi25 and Bi20 glass brazes had a less pronounced influence on the dielectric properties of joints. Different glass brazes can be tailored to different requirements depending on specific application and joint property requirements.

Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir; Shamanian, Morteza; Eskandarian, Masoomeh

In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreasedmore » the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased.« less

Temperature dependent viscosity of cobalt ferrite / ethylene glycol ferrofluids

NASA Astrophysics Data System (ADS)

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.

Moessbauer studies in zinc-manganese ferrites for use in measuring small velocities and accelerations with great precision

NASA Technical Reports Server (NTRS)

Escue, W. T.; Gupta, R. G.; Mendiratta, R. G.

1975-01-01

Mossbauer spectroscopy was used for a systematic study of the magnetic behavior of manganese and zinc in mixed ferrites. It was observed that Zn2+ has preference to substitute Mn2+ at interstitial sites where the metal ions are tetrahedrally coordinated with four oxygen neighbors. The internal magnetic hyperfine field at the tetrahedral iron site is larger than that at the octahedral site. The relaxation effects were observed to play an important role as the zinc contents were increased, while the spin-correlation time and the magnetic field were observed to decrease in strength. It is concluded that Mossbauer effect data on complex materials, when used in conjunction with other data, can provide useful insight into the origin of the microscopic properties of magnetic materials.

Synthesis of ferrites obtained from heavy metal solutions using wet method.

PubMed

Yang, Ji; Peng, Juan; Liu, Kaicheng; Guo, Rui; Xu, Dianliang; Jia, Jinping

2007-05-08

Wet method was employed to the treatment of heavy metal-contaminated wastewater, and Zn(x)Fe(3-x)O(4), Ni(x)Fe(3-x)O(4) and Cr(x)Fe(3-x)O(4) (0Cr(3+) and the influence of the three ions on sample thermostability is Zn(2+)>Ni(2+)>Cr(3+).

Improvement of the Coercivity of Cobalt Ferrites Induced by Substitution of Sr2+ Ions for Co2+ Ions

NASA Astrophysics Data System (ADS)

Zhou, Kaiwen; Chen, Wen; Wu, Xuehang; Wu, Wenwei; Lin, Cuiwu; Wu, Juan

2017-07-01

Spinel Co1- x Sr x Fe2O4 ( x = 0.0, 0.1, 0.2, and 0.3) ferrites have been successfully synthesized by calcining a mixture of oxalates in air. X-ray diffraction study shows that the sample with the concentration of x = 0 has a single spinel phase CoFe2O4 structure and the samples with concentrations of x = 0.1-0.3 have a small amount of foreign phase SrFe12O19 and/or Sr7Fe10O22 along the spinel phase. The lattice parameter of the ferrites at first increases with increasing Sr2+ content, then decreases to x = 0.3 due to the large ionic radius of Sr2+ (0.144 nm) as compared to Co2+ (0.072 nm); for higher doping levels, part of the Sr2+ ions could not enter the tetrahedral (A) and/or octahedral (B) sites but forms a second phase Sr7Fe10O22. The addition of Sr2+ ions decreases the average crystallite size of Co1- x Sr x Fe2O4, which is attributed to the foreign phase Sr7Fe10O22 and/or SrFe12O19 restraining the growth of the Co1- x Sr x Fe2O4 crystallite. The trend of specific saturation magnetization ( Ms), remanence ( Mr), and anisotropy constant ( K eff) decreases with the increase in Sr2+ content, whereas that of coercivity is increased. In this study, Co0.8Sr0.2Fe2O4 obtained at 800°C exhibits the highest coercivity (1699.25 ± 40.78 Oe), and Co0.7Sr0.3Fe2O4 obtained at 900°C exhibits the highest squareness (0.470 ± 0.008).

Influence of cobalt on structural and magnetic properties of nickel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ati, Ali A.; Othaman, Zulkafli; Samavati, Alireza

2013-11-01

Improving the magnetic response of nanocrystalline nickel ferrites is the key issue in high density recording media. A series of cobalt substituted nickel ferrite nanoparticles with composition Ni(1-x)CoxFe2O4, where 0.0 ⩽ x ⩽ 1.0, are synthesized using co-precipitation method. The XRD spectra revealed the single phase spinel structure and the average sizes of nanoparticles are estimated to be 16-19 nm. These sizes are small enough to achieve the suitable signal to noise ratio in the high density recording media. The lattice parameter and coercivity shows monotonic increment with the increase of Co contents ascribed to the larger ionic radii of the cobalt ion. The specific saturation magnetization (Ms), remanent magnetization (Mr) and the coercivity (Hc) of the spinel ferrites are further improved by the substitutions of Co+2 ions. The values of Ms for NiFe2O4 and CoFe2O4 are found to be 43.92 and 78.59 emu/g, respectively and Hc are in the range of 51-778 Oe. The FTIR spectra of the spinel phase calcinated at 600 °C exhibit two prominent fundamental absorption bands in the range of 350-600 cm-1 assigned to the intrinsic stretching vibrations of the metal at the tetrahedral and octahedral sites. The role played by the Co ions in improving the structural and magnetic properties are analyzed and understood. Our simple, economic and environmental friendly preparation method may contribute towards the controlled growth of high quality ferrite nanopowders, potential candidates for recording.

Metallurgical and Corrosion Characterization of POST Weld Heat Treated Duplex Stainless Steel (uns S31803) Joints by Friction Welding Process

NASA Astrophysics Data System (ADS)

Asif M., Mohammed; Shrikrishna, Kulkarni Anup; Sathiya, P.

2016-02-01

The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080∘C, 1150∘C and 1200∘C with 15min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080∘C followed by water quench and at 1150∘C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov-Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100∘C and that for oil quenching was around 1140∘C. The pit depths were found to be in the range of 100nm and width of 1.5-2μm.

Corrosion behavior of oxide dispersion strengthened ferritic steels in supercritical water

NASA Astrophysics Data System (ADS)

Gao, Wenhua; Guo, Xianglong; Shen, Zhao; Zhang, Lefu

2017-04-01

The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer.

Surfactant assisted synthesis of aluminum doped SrFe{sub 10}Al{sub 2}O{sub 19} hexagonal ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neupane, D., E-mail: dneupane@memphis.edu; Wang, L.; Mishra, S. R.

2015-05-07

M-type aluminum doped SrFe{sub 10}Al{sub 2}O{sub 19} were synthesized via co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The effects of CTAB content (x = 0, 1, 3, and 9 wt. %) on the formation, structure, morphology, magnetic, and dielectric properties of the SrFe{sub 10}Al{sub 2}O{sub 19} nanoparticles were investigated. X-ray diffraction results show elimination of α-Fe{sub 2}O{sub 3} phase from samples prepared using CTAB. Morphological changes including grain and crystallite size was noticed with the increase in the CTAB content. With the increase in CTAB, powder particles grew in hexagonal plates. A linear increase in saturation magnetization, Ms, with CTABmore » content was observed from 56.5 emu/g at 0% CTAB to 66.4 emu/g at 9% CTAB. This is a net increase of 17.5% in Ms. The coercivity (Hc ∼ 5700 Oe) of sample reached maximum at 1% CTAB and reduced with further CTAB content reaching to a minimum value of 4488 Oe at 9% CTAB. A slight increase in Curie temperature (735 K) was also observed for samples synthesized using CTAB as compared to that of sample prepared in the absence of CTAB (729 K). Samples synthesized with CTAB show higher dielectric constants as compared to samples prepared without CTAB, while dielectric constant for all samples show decrease in value with the increase in frequency. These results imply that CTAB may act as a crystallization master, controlling the nucleation and growth of SrFe{sub 10}Al{sub 2}O{sub 19} crystal. The study delineates the scope of improving magnetic properties of ferrites without substitution of metal ions.« less

High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Henry, Michael F.; Savage, Warren F.

1984-07-01

Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures, and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques. The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs. Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase (NbCrN), sigma phase, and stringered phases rich in Mn and Cr.

Response of Phase Transformation Inducing Heat Treatments on Microstructure and Mechanical Properties of Reduced Activation Ferritic-Martensitic Steels of Varying Tungsten Contents

NASA Astrophysics Data System (ADS)

Chandravathi, K. S.; Laha, Kinkar; Sasmal, C. S.; Parameswaran, P.; Nandagopal, M.; Tailor, H. M.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

2014-09-01

Microstructure and mechanical properties of 9Cr-W-0.06Ta Reduced Activation Ferritic-Martensitic (RAFM) steels having various tungsten contents ranging from 1 to 2 wt pct have been investigated on subjecting the steels to isothermal heat treatments for 5 minutes at temperatures ranging from 973 K to 1473 K (700 °C to 1200 °C) (below Ac1 to above Ac3) followed by oil quenching and tempering at 1033 K (760 °C) for 60 minutes. The steels possessed tempered martensite structure at all the heat-treated conditions. Prior-austenitic grain size of the steels was found to decrease on heating in the intercritical temperature range (between Ac1 and Ac3) and at temperatures just above the Ac3 followed by increase at higher heating temperatures. All the steels suffered significant reduction in hardness, tensile, and creep strength on heating in the intercritical temperature range, and the reduction was less for steel having higher tungsten content. Strength of the steels increased on heating above Ac3 and was higher for higher tungsten content. Transmission Electron Microscopy (TEM) investigations of the steels revealed coarsening of martensitic substructure and precipitates on heating in the intercritical temperature range, and the coarsening was relatively less for higher tungsten content steel, resulting in less reduction in tensile and creep strength on intercritical heating. Tensile and creep strengths of the steels at different microstructural conditions have been rationalized based on the estimated inter-barrier spacing to dislocation motion. The study revealed the uniqueness of inter-barrier spacing to dislocation motion in determining the strength of tempered martensitic steels subjected to different heat treatments.

Hot-rolling of reduced activation 8CrODS ferritic steel

NASA Astrophysics Data System (ADS)

Wu, Xiaochao; Ukai, Shigeharu; Leng, Bin; Oono, Naoko; Hayashi, Shigenari; Sakasegawa, Hideo; Tanigawa, Hiroyasu

2013-11-01

The 8CrODS ferritic steel is based on J1-lot developed for the advanced fusion blanket material to increase the coolant outlet temperature. A hot-rolling was conducted at the temperature above Ar3 of 716 °C, and its effect on the microstructure and tensile strength in 8CrODS ferritic steel was evaluated, comparing together with normalized and tempered specimen. It was confirmed that hot-rolling leads to slightly increased fraction of the ferrite and highly improved tensile strength. This ferrite was formed by transformation from the hot-rolled austenite during cooling due to fine austenite grains induced by hot-rolling. The coarsening of the transformed ferrite in hot-rolled specimen can be attributed to the crystalline rotation and coalescence of the similar oriented grains. The improved strength of hot-rolled specimen was ascribed to the high dislocation density and replacement of easily deformed martensite with the transformed coarse ferrite.

Austenitic-ferritic stainless steels: A state-of-the-art review

NASA Astrophysics Data System (ADS)

Voronenko, B. I.

1997-10-01

Austenitic-ferritic stainless steels, more commonly known as duplex stainless steels, or DSS for short, consist of two basic phases. One is austenite, A, and the other is ferrite, F, present in about equal amounts (but not less than 30% each). The two phases owe their corrosion resistance to the high chromium content. Compared to austenitic stainless steels, ASS, they are stronger (without sacrificing ductility), resist corrosion better, and cost less due to their relatively low nickel content. DSS can be used in an environment where standard ASS are not durable enough, such as chloride solutions (ships, petrochemical plant, etc.). Due to their low nickel content and the presence of nickel, DSS have good weldability. However, they have a limited service temperature range (from -40 to 300°) because heating may cause them to give up objectionable excess phases and lower the threshold of cold brittleness in the heat-affected zone of welded joints. State-of-the art DSS are alloyed with nitrogen to stabilize their austenite, and in this respect the nitrogen does the job of nickel. Also, nitrogen enhances the strength and resistance to pitting and improves the structure of welds.

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti-Containing Weld Metals of X80 Pipeline Steel

NASA Astrophysics Data System (ADS)

Wang, Bingxin; Liu, Xianghua; Wang, Guodong

2018-06-01

X80 steel weld metals with Ti contents of 0.003 to 0.13 pct were prepared by the single-pass submerged-arc welding process. The effects of Ti content in weld metals on the constituent phases of inclusions and chemical compositions of the constituent phases, as well as the potency of acicular ferrite (AF) nucleation on the inclusions were investigated. Moreover, the crystallographic orientation relationship between the AF and inclusion was examined. The results show that with an increase in Ti content, the primary constituent phases of the inclusions change from the (Mn-Al-Si-O) compound to a mixture of spinel and pseudobrookite solid solutions, and eventually to pseudobrookite. The spinel solid solution is characterized by the MnTi2O4 constituent. Compared to pseudobrookite, spinel has a lower Ti concentration, but a significantly higher Mn content. In the case of the presence of a considerable amount of spinel, the Mn element is enriched strongly in the inclusions, resulting in the development of a Mn-depleted zone (MDZ) in the matrix around the inclusions, which enhances the driving force for AF formation. AF shows the Baker-Nutting orientation relationship with MnTi2O4. The formation of MDZ and the presence of the Baker-Nutting orientation relationship promote the ability of inclusions to nucleate the intragranular AF.

Inclusion Characteristics and Acicular Ferrite Nucleation in Ti-Containing Weld Metals of X80 Pipeline Steel

NASA Astrophysics Data System (ADS)

Wang, Bingxin; Liu, Xianghua; Wang, Guodong

2018-03-01

X80 steel weld metals with Ti contents of 0.003 to 0.13 pct were prepared by the single-pass submerged-arc welding process. The effects of Ti content in weld metals on the constituent phases of inclusions and chemical compositions of the constituent phases, as well as the potency of acicular ferrite (AF) nucleation on the inclusions were investigated. Moreover, the crystallographic orientation relationship between the AF and inclusion was examined. The results show that with an increase in Ti content, the primary constituent phases of the inclusions change from the (Mn-Al-Si-O) compound to a mixture of spinel and pseudobrookite solid solutions, and eventually to pseudobrookite. The spinel solid solution is characterized by the MnTi2O4 constituent. Compared to pseudobrookite, spinel has a lower Ti concentration, but a significantly higher Mn content. In the case of the presence of a considerable amount of spinel, the Mn element is enriched strongly in the inclusions, resulting in the development of a Mn-depleted zone (MDZ) in the matrix around the inclusions, which enhances the driving force for AF formation. AF shows the Baker-Nutting orientation relationship with MnTi2O4. The formation of MDZ and the presence of the Baker-Nutting orientation relationship promote the ability of inclusions to nucleate the intragranular AF.

The Effects of High Al2O3 on the Metallurgical Properties of Sinter

NASA Astrophysics Data System (ADS)

Yu, Wen-tao; Zuo, Hai-bin; Zhang, Jian-liang; Zhang, Tao

Sintering-pot tests and metallurgical performances of sinter with 4 kind of different Al2O3 contents are experimented in this paper. Results show: when the Al2O3 contents increase from 2.0% to 3.5%, acicular calcium ferrites in mine phase will be gradually replaced by plate-like iron calcium. The increase of Al2O3 contents will lead to the addition of liquid viscosity and the reduction of permeability of sinter bed. Sintering time will be prolonged. The rate of yield is stable basically but production is low; besides, the increase of liquid viscosity will decrease of drum strength. The change of permeability of the material layer will make RDI+3.15 decrease first and then increase when Al2O3 contents changed from 2.0% to 3.5%. RI of sinter shows a contrary trend because many open voids are formed by deterioration of liquidity first and then pores closed.

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orozco, C.; Melendez, A.; Manadhar, S.

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2O 4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–xMo xO 4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7more » g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+) for higher x while in a mixed chemical valence state (Mo 4+, Mo 5+, Mo 6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.« less

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

DOE PAGES

Orozco, C.; Melendez, A.; Manadhar, S.; ...

2017-09-26

Here, we report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe 2O 4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe 2–xMo xO 4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 Å coupled with a significant increase in density from 5.4 to 5.7more » g/cm 3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the chemistry of Mo is complex in these CFMO compounds; Mo ions exist in the lower oxidation state (Mo 4+) for higher x while in a mixed chemical valence state (Mo 4+, Mo 5+, Mo 6+) for lower x values. From the temperature-dependent magnetization, the samples show ferrimagnetic behavior including the pristine CFO. From the isothermal magnetization measurements, we find almost 2-fold decrease in coercive field ( H c) from 2143 to 1145 Oe with the increase in Mo doping up to 30%. This doping-dependent H c is consistently observed at all the temperatures measured (4, 100, 200, and 300 K). Furthermore, the saturation magnetization estimated at 4 K and at 1.5 T (from M–H loops) goes through a peak at 92 emu/g (at 15% Mo doping) from 81 emu/g (pristine CFO), and starts decreasing to 79 emu/g (at 30% Mo doping). The results demonstrate that the crystal structure, microstructure, and magnetic properties can be tuned by controlling the Mo-content in the CFMO materials.« less

Use of double and triple-ion irradiation to study the influence of high levels of helium and hydrogen on void swelling of 8-12% Cr ferritic-martensitic steels

NASA Astrophysics Data System (ADS)

Kupriiyanova, Y. E.; Bryk, V. V.; Borodin, O. V.; Kalchenko, A. S.; Voyevodin, V. N.; Tolstolutskaya, G. D.; Garner, F. A.

2016-01-01

In accelerator-driven spallation (ADS) devices, some of the structural materials will be exposed to intense fluxes of very high energy protons and neutrons, producing not only displacement damage, but very high levels of helium and hydrogen. Unlike fission flux-spectra where most helium and hydrogen are generated by transmutation in nickel and only secondarily in iron or chromium, gas production in ADS flux-spectra are rather insensitive to alloy composition, such that Fe-Cr base ferritic alloys also generate very large gas levels. While ferritic alloys are known to swell less than austenitic alloys in fission spectra, there is a concern that high gas levels in fusion and especially ADS facilities may strongly accelerate void swelling in ferritic alloys. In this study of void swelling in response to helium and hydrogen generation, irradiation was conducted on three ferritic-martensitic steels using the Electrostatic Accelerator with External Injector (ESUVI) facility that can easily produce any combination of helium to dpa and/or hydrogen to dpa ratios. Irradiation was conducted under single, dual and triple beam modes using 1.8 MeV Cr+3, 40 keV He+, and 20 keV H+. In the first part of this study we investigated the response of dual-phase EP-450 to variations in He/dpa and H/dpa ratio, focusing first on dual ion studies and then triple ion studies, showing that there is a diminishing influence on swelling with increasing total gas content. In the second part we investigated the relative response of three alloys spanning a range of starting microstructure and composition. In addition to observing various synergisms between He and H, the most important conclusion was that the tempered martensite phase, known to lag behind the ferrite phase in swelling in the absence of gases, loses much of its resistance to void nucleation when irradiated at large gas/dpa levels.

Effect of abrasive grit size on wear of manganese-zinc ferrite under three-body abrasion

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1987-01-01

Wear experiments were conducted using replication electron microscopy and reflection electron diffraction to study abrasion and deformed layers produced in single-crystal Mn-Zn ferrites under three-body abrasion. The abrasion mechanism of Mn-Zn ferrite changes drastically with the size of abrasive grits. With 15-micron (1000-mesh) SiC grits, abrasion of Mn-Zn ferrite is due principally to brittle fracture; while with 4- and 2-micron (4000- and 6000-mesh) SiC grits, abrasion is due to plastic deformation and fracture. Both microcracking and plastic flow produce polycrystalline states on the wear surfaces of single-crystal Mn-Zn ferrites. Coefficient of wear, total thickness of the deformed layers, and surface roughness of the wear surfaces increase markedly with an increase in abrasive grit size. The total thicknesses of the deformed layers are 3 microns for the ferrite abraded by 15-micron SiC, 0.9 microns for the ferrite abraded by 4-micron SiC, and 0.8 microns for the ferrite abraded by 1-micron SiC.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.

In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modifiedmore » alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.« less

Abrasion and deformed layer formation of manganese-zinc ferrite in sliding contact with lapping tapes

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Tanaka, K.

1986-01-01

Wear experiments were conducted using replication electron microscopy and reflection electron diffraction to study abrasion and the deformed layers produced in single-crystal Mn-Zn ferrite simulated heads during contact with lapping tapes. The crystaline state of the head is changed drastically during the abrasion process. Crystalline states ranging from nearly amorphous to highly textured polycrystalline can be produced on the wear surface of a single-crystal Mn-Zn ferrite head. The total thickness of the deformed layer was approximately 0.8 microns. This thickness increased as the load and abrasive grit size increased. The anisotropic wear of the ferrite was found to be inversely proportional to the hardness of the wear surface. The wear was lower in the order 211 111 10 0110. The wear of the ferrite increased markedly with an increase in sliding velocity and abrasive grit size.

Effects of thermomechanical processing on the microstructure and mechanical properties of a Ti-V-N steel

NASA Astrophysics Data System (ADS)

Dogan, B.; Collins, L. E.; Boyd, J. D.

1988-05-01

Based on studies of austenite deformation behavior and continuous-cooling-transformation behavior of a Ti-V microalloyed steel by cam plastometer and quench-deformation dilatometer, respectively, plate rolling schedules were designed to produce (i) recrystallized austenite, (ii) unrecrystallized austenite, (iii) deformed ferrite + unrecrystallized austenite. The effects of austenite condition and cooling rate on the final microstructure and mechanical properties were investigated. To rationalize the variation in final ferrite grain size with different thermomechanical processing schedules, it is necessary to consider the kinetics of ferrite grain growth in addition to the density of ferrite nucleation sites. The benefit of dilatometer studies in determining the optimum deformation schedule and cooling rate for a given steel is domonstrated. A wide range of tensile and impact properties results from the different microstructures studied. Yield strength is increased by increasing the amount of deformed ferrite, bainite, or martensite, and by decreasing the ferrite grain size. Impact toughness is most strongly influenced by ferrite grain size and occurrence of rolling plane delaminations.

Effect of alloying elements and coiling temperature on the recrystallization behavior and the bainitic transformation in TRIP steels

NASA Astrophysics Data System (ADS)

Han, Seongho; Seong, Hwangoo; Ahn, Yeonsang; Garcia, C. I.; DeArdo, A. J.; Kim, Inbae

2009-08-01

The effects of alloying elements and coiling temperature on recrystallization behavior and bainitic transformation were investigated based on 0.07C-Mn-Cr-Nb steel with a low carbon equivalent. Based on the ferrite recrystallization behavior, the proper intercritical annealing temperature of all studied steels was suggested to produce TRIP steel with good strength and elongation balance. All steels coiled at 550 °C showed much faster ferrite recrystallization behavior than steels coiled at 700 °C. In addition to the coiling temperature, the effect of increasing carbon content on the ferrite recrystallization was minor at a coiling temperature of 550 °C, but much more prominent at a coiling temperature of 700 °C. The highest Mo added steel showed the best strength and elongation balance, and the highest carbon and Mo added steel showed the highest tensile strength at a coiling temperature of 550 °C. The steel containing a higher amount of elemental Al (0.7 wt.% Al) exhibited much better elongation than the lower Al added steel (0.04 wt.% Al) in TS 780 MPa grade, about 24 % and 19 %, respectively.

Growth of Nanoscale Nickel Ferrite on Carbonaceous Matrix- A Novel Method of Turning Harmful Particulates into a Functional Nanocomposite: An XAFS Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pattanaik, S.; Huggins, F; Huffman, G

2010-01-01

Particulate matter (PM) emission from residual oil combustion typically consists of carbonaceous material accompanied by inorganic matter notably transition metal sulfates. Often a minor sulfide form is found in the coarse fraction while an oxide form is more common in the fine and ultrafine fractions. A composite comprising of nanoscale nickel ferrite dispersed on carbonaceous matrix has been obtained following liberation of metal sulfates from the fine PM - a novel method of turning harmful particulates into a functional nanocomposite without the need for elaborate preparation using expensive precursors. The nickel ferrite content in the composite varies with the Fe/Nimore » ratio in particulate, fuel type, and combustion condition. Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific atom pair correlations within the spinel ferrite from which the relative occupancy of the cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II) has strong preference for the octahedral site, while Fe(III) prefers both sites which is consistent with that of an inverted spinel ferrite.« less

Growth of nanoscale nickel ferrite on carbonaceous matrix--A novel method of turning harmful particulates into a functional nanocomposite: An XAFS study.

PubMed

Pattanaik, Sidhartha; Huggins, Frank E; Huffman, Gerald P

2010-06-15

Particulate matter (PM) emission from residual oil combustion typically consists of carbonaceous material accompanied by inorganic matter notably transition metal sulfates. Often a minor sulfide form is found in the coarse fraction while an oxide form is more common in the fine and ultrafine fractions. A composite comprising of nanoscale nickel ferrite dispersed on carbonaceous matrix has been obtained following liberation of metal sulfates from the fine PM--a novel method of turning harmful particulates into a functional nanocomposite without the need for elaborate preparation using expensive precursors. The nickel ferrite content in the composite varies with the Fe/Ni ratio in particulate, fuel type, and combustion condition. Such variation may lead to the composite exhibiting diverse physical behaviors. Detailed structure and cation distribution in dispersed ferrite have been studied using Fe and Ni K-edges XAFS spectroscopy. Peaks are identified in the radial structure function with specific atom pair correlations within the spinel ferrite from which the relative occupancy of the cations in the octahedral and tetrahedral sites can be discerned. The results show that Ni(II) has strong preference for the octahedral site, while Fe(III) prefers both sites which is consistent with that of an inverted spinel ferrite. Copyright 2010 Elsevier B.V. All rights reserved.

Microwave processed NiMg ferrite: Studies on structural and magnetic properties

NASA Astrophysics Data System (ADS)

Chandra Babu Naidu, K.; Madhuri, W.

2016-12-01

Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required. Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties (vice sintering and frequency dependence of electrical and magnetic properties) with the current technological trends. Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies. These technologies demand low temperature sinter-ability of ferrites. This article presents low temperature microwave sintered Ni-Mg ferrites of general chemical formula Ni1-xMgxFe2O4 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) for potential applications as transformer core materials. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively. The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of 308 K-873 K and 42 Hz-5 MHz.

Synthesis and magnetic properties of tin spinel ferrites doped manganese

NASA Astrophysics Data System (ADS)

El Moussaoui, H.; Mahfoud, T.; Habouti, S.; El Maalam, K.; Ben Ali, M.; Hamedoun, M.; Mounkachi, O.; Masrour, R.; Hlil, E. K.; Benyoussef, A.

2016-05-01

In this work we report the synthesis, the microstructural characterization and the magnetic properties of tin spinel ferrites doped manganese (Sn1-xMnxFe2O4 with x=0.25, 0.5, 0.75, and 1) nanoparticles prepared by co-precipitation method. The effect of annealing temperature on the structure, morphology and magnetic properties of Sn0.5Mn0.5Fe2O4 has been investigated. The synthesized nanoparticle sizes have been controlled between 4 and 9 nm, with uniform spherical morphology as confirmed by transmission electron microscopy (TEM). All the samples prepared possess single domain magnetic. The nanoparticles of Sn0.5Mn0.5Fe2O4 with 4 nm in diameter have a blocking temperature close to 100 K. In addition, the cation distribution obtained from the X-ray diffraction of this sample was confirmed by magnetic measurement. For the Sn1-xMnxFe2O4; (0≤x≤1) samples, the magnetization and coercive fields increase when the augmentation of Mn content increases. For x=0.5, such parameters decrease when the calcination temperature increases.

Dielectric and magnetic studies of Cr+3 doped nickel ferrite by combustion method

NASA Astrophysics Data System (ADS)

Parveez, Asiya; Shekhawat, M. S.; Sindhu, S.; Srikanth, C.; Nayeem, Firdous; Mohd. Shariff, S.; Sinha, R. R.; Chaudhuri, Arka; Khader, S. Abdul

2018-05-01

Cr+3 doped nickel ferrite nanoparticles having the basic composition NiCrxFe2-xO4 (x=0, 0.1, 0.15, 0.2, 1) were prepared using auto combustion method. Structural, dielectric, a.c conductivity and magnetic properties of these samples, which are sintered at 800°C were studied. The structures of the synthesized samples were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the synthesized samples. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The dielectric constant (ɛ') and dielectric loss factor (ɛ″) of nanocrystalline nickel ferrites were investigated as a function of frequency and Cr+3 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. The dependence of ɛ' and ɛ″ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization, which is in agreement with the Koop's theory. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in NiCrxFe2-xO4 nanoferrites are in conformity with the electron hopping model. The magnetic properties of Cr+3 doped nano-nickel ferrite were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization decreases along with the increase in chromium content.

Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

PubMed

Yin, H; Casey, P S; Chow, G M

2012-11-01

Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

A preliminary investigation of high dose ion irradiation response of a lanthana-bearing nanostructured ferritic steel processed via spark plasma sintering

NASA Astrophysics Data System (ADS)

Pasebani, Somayeh; Charit, Indrajit; Guria, Ankan; Wu, Yaqiao; Burns, Jatuporn; Butt, Darryl P.; Cole, James I.; Shao, Lin

2017-11-01

A nanostructured ferritic steel with nominal composition of Fe-14Cr-1Ti-0.3Mo-0.5La2O3 (wt.%) was irradiated with Fe+2 ions at 475 °C for 100, 200, 300 and 400 dpa. Grain coarsening was observed for the samples irradiated for 200-400 dpa resulting in an increase of the average grain size from 152 nm to 620 nm. Growth of submicron grains at higher radiation doses is due to decreased pinning effect imparted by Cr-O rich nanoparticles (NPs) that underwent coarsening via Ostwald ripening. Dislocation density consistently increased with increasing irradiation dose at 300 and 400 dpa. The mean radius of lanthanum-containing nanoclusters (NCs) decreased and their number density increased above 200 dpa, which is likely due to solutes ejection caused by ballistic dissolution and irradiation-enhanced diffusion. Chromium, titanium, oxygen and lanthanum content of nanoclusters irradiated at 200 dpa and higher got reduced by almost half the initial value. The reduction in size of the nanoclusters accompanied with their higher number density and higher dislocation density led to significant radiation hardening with increasing irradiation dose.

Influence of Sn-Mg co-substitution on the microstructural and magnetic characteristics of M-type SrCaLa hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Huang, Duohui; Shao, Juxiang; Tang, Jin; Ur Rehman, Khalid Mehmood; Wu, Zhen

2018-04-01

Sn-Mg co-substituted M-type SrCaLa hexaferrites Sr0.5Ca0.2La0.3Fe12.0-2x(SnMg)xO19 (0.0 ≤ x ≤ 0.5) have been synthesized by ball milling and calcining. The results of X-ray diffraction show that a single magnetoplumbite phase is exhibited in all the samples and no impurity phase is observed in the structure. Lattice constants (c and a) increase with increasing Sn-Mg content (x) from 0.0 to 0.5. Platelet like structure exhibited by FE-SEM micrographs confirms the hexagonal structure of the synthesized samples. The saturation magnetization (Ms) first increases with increasing SnMg content (x) from 0.0 to 0.1, and then decreases when Sn-Mg content (x) ≥ 0.1. The remanent magnetization (Mr), Mr/Ms ratio, coercivity (Hc), magnetic anisotropy field (Ha) and first anisotropy constant (K1) decrease with increasing Sn-Mg content (x) from 0.0 to 0.5.

Effect of the chemical composition and the structural and phases states of materials on hydrogen retention

NASA Astrophysics Data System (ADS)

Chernov, I. I.; Stal'tsov, M. S.; Kalin, B. A.; Bogachev, I. A.; Guseva, L. Yu.; Korshunov, S. N.

2017-07-01

The results of investigation of the effect of chemical composition and structural and phase states of reactor steels and vanadium alloys on their capture and retention of hydrogen introduced into the materials in various ways are presented. It is shown that, in the case of identical conditions of hydrogen introduction, the amount of hydrogen captured by austenitic steels is substantially higher than that captured by ferritic/ martensitic steels. At the same time, the EP450 ODS ferritic/martensitic steel dispersion-strengthened with nanosized yttrium oxide particles retains a substantially higher amount of hydrogen as compared to that retained in the EP450 matrix steel. The alloying of vanadium with tungsten, zirconium, and titanium leads to an increase in the amount of retained hydrogen. The effect of titanium content on hydrogen retention is found to be nonmonotonic; the phenomenon is explained from a physical view point.

Microstructural and Electrochemical Evaluation of Fusion Welded Low-Nickel and 304 SS at Different Heat Input

NASA Astrophysics Data System (ADS)

Bansod, Ankur V.; Patil, Awanikumar P.; Moon, Abhijeet P.; Shukla, Sourabh

2017-12-01

The present research study investigates the effect of heat input using E 308 electrode (controlled by welding current, i.e., 70, 85 and 100 A) on microstructure, mechanical properties and corrosion behavior of low-nickel and 304 stainless steel (SS) weldments produced by shielded metal arc welding technique. SEM investigation shows that with the higher heat input, δ-ferrite content was reduced. Dendrite and inter-dendritic length is also reduced by lowering the heat input. For all the heat inputs, it is observed that δ-ferrite content was higher in 304 stainless steel (SS) as compared to that of low-nickel austenitic stainless steel (Cr-Mn SS). Considering the heat input for Cr-Mn SS, coarse grains were observed in the heat-affected zone region. For low heat input (LHI), tensile fracture surface has exhibited river-like pattern with dimple appearance. Corrosion studies show better pitting resistance for low heat input (LHI) samples due to higher δ-ferrite present in the weld region. Similarly, higher interphase corrosion resistance is observed in both the SS grades causing more dissolution in the LHI samples.

Concepts for the development of nanoscale stable precipitation-strengthened steels manufactured by conventional methods

DOE PAGES

Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.; ...

2014-11-11

In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modifiedmore » alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.« less

The Microstructure and Pitting Resistance of Weld Joints of 2205 Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Wu, Mingfang; Liu, Fei; Pu, Juan; Anderson, Neil E.; Li, Leijun; Liu, Dashuang

2017-11-01

2205 duplex stainless steel (DSS) was welded by submerged arc welding. The effects of both heat input and groove type on the ferrite/austenite ratio and elemental diffusion of weld joints were investigated. The relationships among welding joint preparation, ferrite/austenite ratio, elemental diffusion, and pitting corrosion resistance of weld joints were analyzed. When the Ni content of the weld wire deposit was at minimum 2-4% higher than that of 2205 DSS base metal, the desired ratio of ferrite/austenite and elemental partitioning between the austenite and ferrite phases were obtained. While the pitting sensitivity of weld metal was higher than that of base metal, the self-healing capability of the passive film of weld metal was better than that of the base metal when a single V-type groove was used. Furthermore, the heat input should be carefully controlled since pitting corrosion occurred readily in the coarse-grained heat-affected zone near the fusion line of welded joints.

Structural, dielectric and magnetic properties of nickel substituted cobalt ferrite nanoparticles: Effect of nickel concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velhal, Ninad B.; Patil, Narayan D.; Puri, Vijaya R., E-mail: vijayapuri1@gmail.com

2015-09-15

Nickel substituted cobalt ferrite nanoparticles with composition Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 1.0) was synthesized using simple, low temperature auto combustion method. The X-ray diffraction patterns reveal the formation of cubic phase spinel structure. The crystallite size varies from 30-44 nm with the nickel content. Porous and agglomerated morphology of the bulk sample was displayed in the scanning electron microscopy. Micro Raman spectroscopy reveals continuous shift of E{sub g} and E{sub g}(2) stokes line up to 0.8 Ni substitution. The dispersion behavior of the dielectric constant with frequency and the semicircle nature of the impedance spectramore » show the cobalt nickel ferrite to have high resistance. The ferromagnetic nature is observed in all the samples, however, the maximum saturation magnetization was achieved by the 0.4 Ni substituted cobalt ferrite, which is up to the 92.87 emu/gm at 30K.« less

Impedance spectroscopy studies in cobalt ferrite-reduced graphene oxide nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Supriya, Sweety, E-mail: sweety@iitp.ac.in; Kumar, Sunil, E-mail: sunil.pph13@iitp.ac.in; Kar, Manoranjan, E-mail: mano@iitp.ac.in

2016-05-06

(1-x)Cobalt ferrite-(x)reduced graphene oxidenanocomposites with x=0, 0.1, 0.2 and 0.3 were prepared by the ultrasonic method. The crystal symmetry modification due to reduced graphene oxide and cobalt ferrite interaction has been studied by employing the X-ray diffraction technique. Morphology of the samples was studied by the Field emission scanning electron microscopy (FE-SEM). Study on electrical properties of the cobalt ferrite-reduced graphene oxide nanocomposites explores the possible application of these composites as anode material. Impedance decreases with an increase in frequency as well as temperature, which supports an increase in ac electrical conductivity. The modified Debye relaxation model can explain themore » behavior of impedance in cobalt ferrite-reduced graphene oxide nanocomposites.« less

Fusion welding process

DOEpatents

Thomas, Kenneth C.; Jones, Eric D.; McBride, Marvin A.

1983-01-01

A process for the fusion welding of nickel alloy steel members wherein a ferrite containing pellet is inserted into a cavity in one member and melted by a welding torch. The resulting weld nugget, a fusion of the nickel containing alloy from the members to be welded and the pellet, has a composition which is sufficiently low in nickel content such that ferrite phases occur within the weld nugget, resulting in improved weld properties. The steel alloys encompassed also include alloys containing carbon and manganese, considered nickel equivalents.

Studies of structural, morphological, electrical, and magnetic properties of Mg-substituted Co-ferrite materials synthesized using sol-gel autocombustion method

NASA Astrophysics Data System (ADS)

Mammo, Tulu Wegayehu; Murali, N.; Sileshi, Yonatan Mulushoa; Arunamani, T.

2017-10-01

In this work,a nonmagnetic Mg partially substituted in CoFe2O4 was considered and has been shown to have an impact on structural, electrical and magnetic properties of ferrite materials with Co1-xMgxFe2O4 (x = 0, 0.25, 0.45, and 0.75) forms. Sol-gel synthesis route has been followed to synthesize these materials using citric acid as a fuel. Structural parameters were calculated from powder X-ray diffraction data. X-ray diffraction revealed that all the samples synthesized are pure cubic spinel structured materials with space group of Fd 3 ̅m and the lattice constant varying with Mg concentration. From the field emission scanning electron microscopy (FESEM) microstructure characterizations it has been shown that the synthesized materials are well defined crystalline structured with inhomogeneous grain sizes. Besides, the grain sizes were shown to decrease with increase of Mg-content. Fourier transform Infrared (FT-IR) characterization showed the cation vibrations and stretching of other groups in the wave number range of 400-4000 cm-1. The DC resistivity measurements showed an enhanced resistivity of the samples, in the order of 107 Ω cm, at the highest concentration of Mg. VSM magnetic properties analysis revealed that the Coercive force decreases with increase of Mg concentration whereas the saturation magnetization varies with Mg content.

Effects of titanium on ferrite continuous cooling transformation curves of high-thickness Cr-Mo steels

NASA Astrophysics Data System (ADS)

Lee, Sang-Hoon; Na, Hye-Sung; Park, Gi-Deok; Kim, Byung-Hoon; Song, Sang-Woo; Kang, Chung-Yun

2013-09-01

The effect of Ti on the ferrite-phase transformation in the middle portion of high-thickness Cr-Mo steel vessels was studied. The phase diagrams and ferrite continuous cooling transformation (CCT) curves were calculated thermodynamically, and dilatometry tests were performed to determine the start and finish times of the ferrite transformation. When the Ti concentration was 0.015 mass%, Δ( F s - F f ) of ferrite CCT curve decreased owing to an increase in the concentration of Mn dissolved as a result of (Mn, Ti) oxide formation. When the Ti concentration was 0.03 mass% or greater, the ferrite CCT curves shifted considerably to the right along the time axis owing to an increase in Ti oxide formation and the precipitation of Ti4C2S2, both of which affect the concentration of Mn dissolved in the austenite matrix. As a result, a completely bainitic structure was obtained when the Ti concentration was 0.03 mass% or greater.

Atomistic simulation of the influence of Cr on the mobility of the edge dislocation in Fe(Cr) alloys

NASA Astrophysics Data System (ADS)

Hafez Haghighat, S. M.; Terentyev, D.; Schäublin, R.

2011-10-01

In this work Fe-Cr compounds, as model alloys for the ferritic base steels that are considered as main candidates for the structural materials of the future fusion reactors, are studied using molecular dynamics simulations. The Cr or so-called α' precipitates, which are obstacles to dislocations, affect mechanical properties, leading to hardening and loss of ductility. The flow stress to move an edge dislocation in a Cr solid solution in pure Fe is studied as a function of Cr content. The strength of a nanometric Cr precipitate as obstacle to an edge dislocation in pure Fe is investigated as a function of its Cr content. Results show that with increasing Cr content the precipitate obstacle strength increases, with a strong sensitivity to the local atomic order. Temperature induces a monotonic decrease of the flow stress of the Cr solid solution and of the Cr precipitate obstacle strength.

Effect of cobalt doping level of ferrites in enhancing sensitivity of analytical performances of carbon paste electrode for simultaneous determination of catechol and hydroquinone.

PubMed

Lakić, Mladen; Vukadinović, Aleksandar; Kalcher, Kurt; Nikolić, Aleksandar S; Stanković, Dalibor M

2016-12-01

This work presents the simultaneous determination of catechol (CC) and hydroquinone (HQ), employing a modified carbon paste electrode (CPE) with ferrite nanomaterial. Ferrite nanomaterial was doped with different amount of cobalt and this was investigated toward simultaneous oxidation of CC and HQ. It was shown that this modification strongly increases electrochemical characteristics of the CPE. Also, electrocatalytic activity of such materials strongly depends on the level of substituted Co in the ferrite nanoparticles. The modified electrodes, labeled as CoFerrite/CPE, showed two pairs of well-defined redox peaks for the electrochemical processes of catechol and hydroquinone. Involving of ferrite material in the structure of CPE, cause increase in the potentials differences between redox couples of the investigated compounds, accompanied with increases in peaks currents. Several important parameters were optimized and calibration curves, with limits of detection (LOD) of 0.15 and 0.3µM for catechol and hydroquinone, respectively, were constructed by employing amperometric detection. Effect of possible interfering compounds was also studied, and proposed method was successfully applied for CC and HQ quantification in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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.

EFFECT OF HEAT TREATMENT ON (Cr, Fe)7C3/γ-Fe COATINGS IN SITU SYNTHESIZED BY VACUUM ELECTRON BEAM IRRADIATION

NASA Astrophysics Data System (ADS)

Lu, Binfeng; Chen, Yunxia; Xu, Mengjia

(Cr, Fe)7C3/γ-Fe composite layer has been in situ synthesized on a low carbon steel surface by vacuum electron beam VEB irradiation. The synthesized samples were then subdued to different heat treatments to improve their impaired impact toughness. The microstructure, impact toughness and wear resistance of the heat-treated samples were studied by means of optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), microhardness tester, impact test machine and tribological tester. After heat treatment, the primary and eutectic carbides remained in their original shape and size, and a large number of secondary carbides precipitated in the iron matrix. Since the Widmanstatten ferrite in the heat affected zone (HAZ) transformed to fine ferrite completely, the impact toughness of the heat-treated samples increased significantly. The microhardness of the heat-treated samples decreased slightly due to the decreased chromium content in the iron matrix. The wear resistance of 1000∘C and 900∘C heat-treated samples was almost same with the as-synthesized sample. While the wear resistance of the 800∘C heat-treated one decreased slightly because part of the austenite matrix had transformed to ferrite matrix, which reduced the bonding of carbides particulates.

Effect of Al-Si Coating on Weld Microstructure and Properties of 22MnB5 Steel Joints for Hot Stamping

NASA Astrophysics Data System (ADS)

Lin, Wenhu; Li, Fang; Wu, Dongsheng; Chen, Xiaoguan; Hua, Xueming; Pan, Hua

2018-03-01

22MnB5 hot stamping steels are gradually being used in tailor-welded blank applications. In this experiment, 1-mm-thick Al-Si coated and de-coated 22MnB5 steels were laser-welded and then hot-stamped. The chemical compositions, solidification process, microstructure and mechanical properties were investigated to reveal the effect of Al-Si coating and heat treatment. In the welded condition, the coated joints had an Al content of approximately 2.5 wt.% in the fusion zone and the de-coated joints had 0.5 wt.% Al. The aluminum promoted the δ-ferrite formation as the skeletal structure during solidification. In the high-aluminum weld, the microstructure consisted of martensite and long and band-like δ-ferrite. Meanwhile, the low-aluminum weld was full of lath martensite. After the hot stamping process, the δ-ferrite fraction increased from 10 to 24% in the coated joints and the lath martensite became finer in the de-coated joints. The tensile strengths of the coated joints or de-coated joints were similar to that before hot stamping, but the strength of the coated joints was reduced heavily after hot stamping compared to the de-coated joints and base material. The effect of δ-ferrite on the tensile properties became stronger when the fusion zone was soft and deformed first in the hot-stamped specimens. The coated weld showed a brittle fracture surface with many cleavage planes, and the de-coated weld showed a ductile fracture surface with many dimples in hot-stamped conditions.

Influence of pH on the physical and electromagnetic properties of Mg–Mn ferrite synthesized by a solution combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lwin, Nilar, E-mail: nilarlwin111@gmail.com; School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang; Othman, Radzali, E-mail: radzali@utem.edu.my

The synthesis of nano-crystalline Mg–Mn ferrites by a solution combustion method using citric acid and ammonia was investigated by varying the pH of the precursor solution, which played an important role in controlling the morphology of the synthesized powders. The phase formation, microstructure and electromagnetic properties were studied using X-ray diffraction, scanning electron microscopy, impedance analyzer and vibrating sample magnetometer. Single phase pure spinel Mg–Mn ferrite powders were obtained for all the samples at different pH (< 1, 3, 5, 7, 9). The results showed that an increase of pH improves the crystallinity of the Mg–Mn ferrite nanoparticles. The averagemore » grain size of sintered samples was found to decrease from 2 μm to 0.5 μm with increasing pH values from pH < 1 to pH 9, respectively. The dielectric constant of the samples with different pH is in the range of 7–12 from frequencies of 1 MHz to 1 GHz. The highest saturation magnetization (30.04 emu/g) was obtained for the sample with pH < 1. - Highlights: • Mg–Mn ferrites were synthesized by a solution combustion method with different pH. • Auto-combustion process resulted in the formation of single phase spinel ferrite. • An increase of pH improves the crystallinity of the Mg–Mn ferrite nanoparticles. • pH variation has influence on phase formation and morphology of the ferrite.« less

Effect of Rolling and Subsequent Annealing on Microstructure, Microtexture, and Properties of an Experimental Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Mandal, Arka; Patra, Sudipta; Chakrabarti, Debalay; Singh, Shiv Brat

2017-12-01

A lean duplex stainless steel (LDSS) has been prepared with low-N content and processed by different thermo-mechanical schedules, similar to the industrial processing that comprised hot-rolling, cold-rolling, and annealing treatments. The microstructure developed in the present study on low-N LDSS has been compared to that of high-N LDSS as reported in the literature. As N is an austenite stabilizer, lower-N content reduced the stability of austenite and the austenite content in low-N LDSS with respect to the conventional LDSS. Due to low stability of austenite in low-N LDSS, cold rolling resulted in strain-induced martensitic transformation and the reversion of martensite to austenite during subsequent annealing contributed to significant grain refinement within the austenite regions. δ-ferrite grains in low-N LDSS, on the other hand, are refined by extended recovery mechanism. Initial solidification texture (mainly cube texture) within the δ-ferrite region finally converted into gamma-fiber texture after cold rolling and annealing. Although MS-brass component dominated the austenite texture in low-N LDSS after hot rolling and cold rolling, that even transformed into alpha-fiber texture after the final annealing. Due to the significant grain refinement and formation of beneficial texture within both austenite and ferrite, good combination of strength and ductility has been achieved in cold-rolled and annealed sample of low-N LDSS steel.

Wear-resistant and electromagnetic absorbing behaviors of oleic acid post-modified ferrite-filled epoxy resin composite coating

NASA Astrophysics Data System (ADS)

Wang, Wenjie; Zang, Chongguang; Jiao, Qingjie

2015-03-01

The post-modified Mn-Zn ferrite was prepared by grafting oleic acid on the surface of Mn-Zn ferrite to inhibit magnetic nanoparticle aggregation. Fourier Transform Infrared (FT-IR) spectroscopy was used to characterize the particle surfaces. The friction and electromagnetic absorbing properties of a thin coating fabricated by dispersing ferrite into epoxy resin (EP) were investigated. The roughness of the coating and water contact angle were measured using the VEECO and water contact angle meter. Friction tests were conducted using a stainless-steel bearing ball and a Rockwell diamond tip, respectively. The complex permittivity and complex permeability of the composite coating were studied in the low frequency (10 MHz-1.5 GHz). Surface modified ferrites are found to improve magnetic particles dispersion in EP resulting in significant compatibility between inorganic and organic materials. Results also indicate that modified ferrite/EP coatings have a lower roughness average value and higher water contact angle than original ferrite/EP coatings. The enhanced tribological properties of the modified ferrite/EP coatings can be seen from the increased coefficient value. The composite coatings with modified ferrite are observed to exhibit better reflection loss compared with the coatings with original ferrite.

Surface chemistry, friction, and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to the surfaces of the ferrites in sliding. Previously announced in STAR as N83-19901

Surface chemistry, friction and wear of Ni-Zn and Mn-Zn ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron and Auger electron spectroscopy analysis were used in sliding friction experiments. These experiments were conducted with hot-pressed polycrystalline Ni-Zn and Mn-Zn ferrites, and single-crystal Mn-Zn ferrite in contact with various transition metals at room temperature in both vacuum and argon. The results indicate that Ni2O3 and Fe3O4 were present on the Ni-Zn ferrite surface in addition to the nominal bulk constituents, while MnO2 and Fe3O4 were present on the Mn-Zn ferrite surface in addition to the nominal bulk constituents. The coefficients of friction for the ferrites in contact with metals were related to the relative chemical activity of these metals. The more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites were correlated with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite does strengthen the metal-ferrite contact and increase the friction. The ferrites exhibit local cracking and fracture with sliding under adhesive conditions. All the metals transferred to he surfaces of the ferrites in sliding.

Synthesis, characterization and low temperature electrical conductivity of Polyaniline/NiFe2O4 nanocomposites

NASA Astrophysics Data System (ADS)

Prasanna, G. D.; Prasad, V. B.; Jayanna, H. S.

2015-02-01

Conducting polymer/ferrite nanocomposites with an organized structure provide a new functional hybrid between organic and inorganic materials. The most popular among the conductive polymers is the polyaniline (PANI) due to its wide application in different fields. In the present work nickel ferrite (NiFe2O4) nanoparticles were prepared by sol-gel citrate-nitrate method with an average size of 21.6nm. PANI/NiFe2O4 nanoparticles were synthesized by a simple general and inexpensive in-situ polymerization in the presence of NiFe2O4 nanoparticles. The effects of NiFe2O4 nanoparticles on the dc-electrical properties of polyaniline were investigated. The structural components in the nanocomposites were identified from Fourier Transform Infrared (FTIR) spectroscopy. The crystalline phase of nanocomposites was characterized by X-Ray Diffraction (XRD). The Scanning Electron Micrograph (SEM) reveals that there was some interaction between the NiFe2O4 particles and polyaniline and the nanocomposites are composed of polycrystalline ferrite nanoparticles and PANI. The dc conductivity of polyaniline/NiFe2O4 nanocomposites have been measured as a function of temperature in the range of 80K to 300K. It is observed that the room temperature conductivity cRT decreases with increase in the relative content of NiFe2O4. The experimental data reveals that the resistivity increases for all composites with decrease of temperature exhibiting semiconductor behaviour.

Stabilization of scandium rich spinel ferrite CoFe{sub 2−x}Sc{sub x}O{sub 4} (x≤1) in thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lefevre, Christophe, E-mail: christophe.lefevre@ipcms.unistra.fr; Roulland, François; Thomasson, Alexandre

2015-12-15

Scandium rich cobalt ferrites Co{sub y}Fe{sub 3−x−y}Sc{sub x}O{sub 4} with y~1 never obtained in bulk could be stabilized in pulsed laser deposited thin films. Scandium contents of up to x=1 are reached. The cell parameter increases versus x as awaited when considering the size of scandium. It is equal to 0.8620 nm for x=1, significantly higher than that of CoFe{sub 2}O{sub 4} (0.8396 nm). The lattice mismatch between the MgO (100) substrate and the scandium-containing spinel leads to an increased roughness. Cobalt is displaced from the octahedral site by Sc and mainly occupies the tetrahedral sites for high x values.more » - Graphical abstract: Magnification of the XRD patterns recorded on thin films of CoFe{sub 2-x}Sc{sub x}O{sub 4} for x=0, 0.45, 1 and 1.2, the arrows denote the (004) and (008) diffraction lines of the spinel phase.« less

Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe-Cu Alloys with Addition of Ni

NASA Astrophysics Data System (ADS)

Crozet, C.; Verdier, M.; Lay, S.; Antoni-Zdziobek, A.

2018-07-01

α/γ phase transformations occurring in Fe-10Cu-xNi alloys (0 ≤ x ≤ 15 in mass%) were studied using X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy and chemical analysis, combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobe analysis with wavelength dispersive spectrometry. The influence of cooling rate on the microstructure was investigated using ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastable transformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate. Moreover, most of the Cu phase precipitates on cooling giving rise to a fine distribution of Cu particles in the ferrite grains. For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in the quenched alloy for each composition. The change in hardness is correlated to the effect of Ni solid solution, transformation structure and size of Cu particles.

Structural and magnetic study of Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} nanoferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L.; Rai, B.K.; Mishra, S.R.

2015-05-15

Graphical abstract: Hyperfine field of individual sites (inset) and weighted average hyperfine field as a function of Al{sup 3+} content for Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4}. - Highlights: • Grain size reduction with Al{sup 3+} substitution. • Preferred occupancy of Al{sup 3+} at B site for higher Al{sup 3+} content. • Reduction in Ms, Tc, and hyperfine field with increasing Al{sup 3+} content. • Size dependent variation in coercivity. • Changes in isomer shift due to competing effect of volume and substitution. - Abstract: Nanostructured Al{sup 3+} doped Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} (x = 0.0, 0.2, 0.4,more » 0.6, 0.8, and 1.0) ferrites were synthesized via the wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 °C. With the doping of Al{sup 3+}, the particle size of Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. The main two absorption bands in IR spectra were observed around 600 cm{sup −1} and 400 cm{sup −1} corresponding to stretching vibration of tetrahedral and octahedral group Fe{sup 3+}–O{sup 2−}. Saturation magnetization and hyperfine field values decreased linearly with Al{sup 3+} due to magnetic dilution and the relative strengths of Fe–O–Me (Me = Fe, Ni, Zn, and Al) superexchanges. The coercive field showed an inverse dependence on ferrite particle size with minimum value of 82 Oe for x = 0.4. A continuous drop in Curie temperature was observed with the Al{sup 3+} substitution. From the Moessbauer spectral analysis and X-ray diffraction analysis, it is deduced that Al{sup 3+} for x < 0.4 has no obvious preference for either tetrahedral or octahedral site but has a greater preference for the B site for x > 0.4. In nutshell the study presents detailed structural and magnetic, and Moessbauer analysis of Ni{sub 0.75}Zn{sub 0.25}Fe{sub 2−x}Al{sub x}O{sub 4} ferrites.« less

Studies on Electrical and Magnetic Properties of Mg-Substituted Nickel Ferrites

NASA Astrophysics Data System (ADS)

Chavan, Pradeep; Naik, L. R.; Belavi, P. B.; Chavan, Geeta; Ramesha, C. K.; Kotnala, R. K.

2017-01-01

The semiconducting polycrystalline ferrite materials with the general formula Ni1- x Mg x Fe2O4 were synthesized by using the solid state reaction method. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrographs, and atomic force microscopy techniques were utilized to study the structural parameters. XRD confirms the formation of single phase cubic spinel structure of the ferrites. The crystallite sizes of ferrites determined using the Debye-Scherer formula ranges from 0.963 μm to 1.069 μm. The cation distribution of ferrite shows that Mg2+ ions occupy a tetrahedral site ( A-site) and the Ni2+ ion occupy an octahedral site ( B-site) whereas Fe3+ ions occupies an octahedral as well as a tetrahedral site. The study of elastic parameters such as the longitudinal modulus, rigidity modulus, Young's modulus, bulk modulus, and Debye temperature were estimated using the FTIR technique. The decrease of direct current (DC) resistivity with increase in temperature indicates the semiconducting nature of ferrites. The dielectric constant as well as loss tangent decreases with increase in frequency, and at still higher frequencies, they are almost constant. This shows usual dielectric dispersion behavior attributed to the Maxwell-Wagner type of interfacial polarization and is in accordance with Koop's phenomenological theory. The linear increase of alternating current conductivity with increase of frequency shows the small polaron hopping type of conduction mechanism in all the ferrites. The magnetic properties such as saturation magnetization ( M s ), magnetic moment, coercivity, remnant magnetization ( M r ), and the ratio of M r /M s was estimated using the M-H loop.

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

Effect of powder compaction on radiation-thermal synthesis of lithium-titanium ferrites

NASA Astrophysics Data System (ADS)

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

2017-01-01

Effect of powder compaction on the efficiency of thermal and radiation-thermal synthesis of lithium-substituted ferrites was investigated by X-Ray diffraction and specific magnetization analysis. It was shown that the radiation-thermal heating of compacted powder reagents mixture leads to an increase in efficiency of lithium-titanium ferrites synthesis.

Neutron diffraction and ferromagnetic resonance studies on plasma-sprayed MnZn ferrite films

NASA Astrophysics Data System (ADS)

Yan, Q. Y.; Gambino, R. J.; Sampath, S.; Huang, Q.

2005-02-01

The magnetic properties of MnZn ferrites are affected by the plasma spray process. It is found that improvements can be made by annealing the ferrite films at 500°C-800°C. The annealing induced magnetic property changes are studied by neutron diffraction and ferromagnetic resonance techniques. The increase of the saturation magnetization is attributed to the cation ordering within the spinel lattice, which increases the magnetic moment per ferrite formula. The refinements on the neutron diffraction data suggest that the redistribution of the cation during annealing neither starts from a fully disordered state nor ends to a fully ordered state. The decrease of the coercivity is analyzed with the domain wall pinning model. The measurements on the magnetostriction and residual stress indicate that coercive mechanisms arising from the magnetoelastic energy term are not dominant in these ferrite films. The decrease of the coercivity for annealed ferrite films is mainly attributed to the decrease of the effective anisotropic field, which may result from the homogenization of the film composition and the reduction of the microstructural discontinuity (e.g., cracks, voids, and splat boundaries).

Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Shen; Sun, Aizhi; Xu, Wenhuan

This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz.more » In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078« less

Nanophase cobalt, nickel and zinc ferrites: synchrotron XAS study on the crystallite size dependence of metal distribution.

PubMed

Nordhei, Camilla; Ramstad, Astrid Lund; Nicholson, David G

2008-02-21

Nanophase cobalt, nickel and zinc ferrites, in which the crystallites are in the size range 4-25 nm, were synthesised by coprecipitation and subsequent annealing. X-Ray absorption spectroscopy using synchrotron radiation (supported by X-ray powder diffraction) was used to study the effects of particle size on the distributions of the metal atoms over the tetrahedral and octahedral sites of the spinel structure. Deviations from the bulk structure were found which are attributed to the significant influence of the surface on very small particles. Like the bulk material, nickel ferrite is an inverse spinel in the nanoregime, although the population of metals on the octahedral sites increases with decreasing particle size. Cobalt ferrite and zinc ferrite take the inverse and normal forms of the spinel structure respectively, but within the nanoregime both systems show similar trends in being partially inverted. Further, in zinc ferrite, unlike the normal bulk structure, the nanophase system involves mixed coordinations of zinc(ii) and iron(iii) consistent with increasing partial inversion with size.

Hot Ductility Behaviors in the Weld Heat-Affected Zone of Nitrogen-Alloyed Fe-18Cr-10Mn Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Moon, Joonoh; Lee, Tae-Ho; Hong, Hyun-Uk

2015-04-01

Hot ductility behaviors in the weld heat-affected zone (HAZ) of nitrogen-alloyed Fe-18Cr-10Mn austenitic stainless steels with different nitrogen contents were evaluated through hot tension tests using Gleeble simulator. The results of Gleeble simulations indicated that hot ductility in the HAZs deteriorated due to the formation of δ-ferrite and intergranular Cr2N particles. In addition, the amount of hot ductility degradation was strongly affected by the fraction of δ-ferrite.

Effect of Low-Temperature Sensitization on the Corrosion Behavior of AISI Type 304L SS Weld Metal in Simulated Groundwater

NASA Astrophysics Data System (ADS)

Suresh, Girija; Nandakumar, T.; Viswanath, A.

2018-04-01

The manuscript presents the investigations carried out on the effect of low-temperature sensitization (LTS) of 304L SS weld metal on its corrosion behavior in simulated groundwater, for its application as a canister material for long-term storage of nuclear vitrified high-level waste in geological repositories. AISI type 304L SS weld pad was fabricated by multipass gas tungsten arc welding process using 308L SS filler wire. The as-welded specimens were subsequently subjected to carbide nucleation and further to LTS at 500 °C for 11 days to simulate a temperature of 300 °C for 100-year life of the canister in geological repositories. Delta ferrite (δ-ferrite) content of the 304L SS weld metal substantially decreased on carbide nucleation treatment and further only a marginal decrease occurred on LTS treatment. The microstructure of the as-welded consisted of δ-ferrite as a minor phase distributed in austenite matrix. The δ-ferrite appeared fragmented in the carbide-nucleated and LTS-treated weld metal. The degree of sensitization measured by double-loop electrochemical potentokinetic reactivation method indicated an increase in carbide nucleation treatment when compared to the as-welded specimens, and further increase occurred on LTS treatment. Potentiodynamic anodic polarization investigations in simulated groundwater indicated a substantial decrease in the localized corrosion resistance of the carbide-nucleated and LTS 304L SS weld metals, when compared to the as-welded specimens. Post-experimental micrographs indicated pitting as the primary mode of attack in the as-welded, while pitting and intergranular corrosion (IGC) occurred in the carbide-nucleated weld metal. LTS-treated weld metal predominantly underwent IGC attack. The decrease in the localized corrosion resistance of the weld metal after LTS treatment was found to have a direct correlation with the degree of sensitization and the weld microstructure. The results are detailed in the manuscript.

Effect of Low-Temperature Sensitization on the Corrosion Behavior of AISI Type 304L SS Weld Metal in Simulated Groundwater

NASA Astrophysics Data System (ADS)

Suresh, Girija; Nandakumar, T.; Viswanath, A.

2018-05-01

The manuscript presents the investigations carried out on the effect of low-temperature sensitization (LTS) of 304L SS weld metal on its corrosion behavior in simulated groundwater, for its application as a canister material for long-term storage of nuclear vitrified high-level waste in geological repositories. AISI type 304L SS weld pad was fabricated by multipass gas tungsten arc welding process using 308L SS filler wire. The as-welded specimens were subsequently subjected to carbide nucleation and further to LTS at 500 °C for 11 days to simulate a temperature of 300 °C for 100-year life of the canister in geological repositories. Delta ferrite ( δ-ferrite) content of the 304L SS weld metal substantially decreased on carbide nucleation treatment and further only a marginal decrease occurred on LTS treatment. The microstructure of the as-welded consisted of δ-ferrite as a minor phase distributed in austenite matrix. The δ-ferrite appeared fragmented in the carbide-nucleated and LTS-treated weld metal. The degree of sensitization measured by double-loop electrochemical potentokinetic reactivation method indicated an increase in carbide nucleation treatment when compared to the as-welded specimens, and further increase occurred on LTS treatment. Potentiodynamic anodic polarization investigations in simulated groundwater indicated a substantial decrease in the localized corrosion resistance of the carbide-nucleated and LTS 304L SS weld metals, when compared to the as-welded specimens. Post-experimental micrographs indicated pitting as the primary mode of attack in the as-welded, while pitting and intergranular corrosion (IGC) occurred in the carbide-nucleated weld metal. LTS-treated weld metal predominantly underwent IGC attack. The decrease in the localized corrosion resistance of the weld metal after LTS treatment was found to have a direct correlation with the degree of sensitization and the weld microstructure. The results are detailed in the manuscript.

MHD Effects of a Ferritic Wall on Tokamak Plasmas

NASA Astrophysics Data System (ADS)

Hughes, Paul E.

It has been recognized for some time that the very high fluence of fast (14.1MeV) neutrons produced by deuterium-tritium fusion will represent a major materials challenge for the development of next-generation fusion energy projects such as a fusion component test facility and demonstration fusion power reactor. The best-understood and most promising solutions presently available are a family of low-activation steels originally developed for use in fission reactors, but the ferromagnetic properties of these steels represent a danger to plasma confinement through enhancement of magnetohydrodynamic instabilities and increased susceptibility to error fields. At present, experimental research into the effects of ferromagnetic materials on MHD stability in toroidal geometry has been confined to demonstrating that it is still possible to operate an advanced tokamak in the presence of ferromagnetic components. In order to better quantify the effects of ferromagnetic materials on tokamak plasma stability, a new ferritic wall has been installated in the High Beta Tokamak---Extended Pulse (HBT-EP) device. The development, assembly, installation, and testing of this wall as a modular upgrade is described, and the effect of the wall on machine performance is characterized. Comparative studies of plasma dynamics with the ferritic wall close-fitting against similar plasmas with the ferritic wall retracted demonstrate substantial effects on plasma stability. Resonant magnetic perturbations (RMPs) are applied, demonstrating a 50% increase in n = 1 plasma response amplitude when the ferritic wall is near the plasma. Susceptibility of plasmas to disruption events increases by a factor of 2 or more with the ferritic wall inserted, as disruptions are observed earlier with greater frequency. Growth rates of external kink instabilities are observed to be twice as large in the presence of a close-fitting ferritic wall. Initial studies are made of the influence of mode rotation frequency on the ferritic effect, as well as observations of the effect of the ferritic wall on disruption halo currents.

Low-Temperature Aging of Delta-Ferrite in 316L SS Welds; Changes in Mechanical Properties and Etching Properties

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Shimizu, Keita; Watanabe, Yutaka

Thermal aging embrittlement of LWR components made of stainless cast (e.g. CF-8 and CF-8M) is a potential degradation issue, and careful attention has been paid on it. Although welds of austenitic stainless steels (SSs) have γ-δ duplex microstructure, which is similar to that of the stainless cast, examination on thermal aging characteristics of the SS welds is very limited. In order to evaluate thermal aging behavior of weld metal of austenitic stainless steel, the 316L SS weld metal has been prepared and changes in mechanical properties and in etching properties at isothermal aging at 335°C have been investigated. The hardness of the ferrite phase has increased with aging, while the hardness of austenite phase has stayed same. It has been suggested that spinodal decomposition has occurred in δ-ferrite by the 335°C aging. The etching rates of δ-ferrite at immersion test in 5wt% hydrochloric acid solution have been also investigated using an AFM technique. The etching rate of ferrite phase has decreased consistently with the increase in hardness of ferrite phase. It has been thought that this characteristic is also caused by spinodal decomposition of ferrite into chromium-rich (α') and iron-rich (α).

Thermomechanical processing of microalloyed powder forged steels and a cast vanadium steel

NASA Astrophysics Data System (ADS)

Dogan, B.; Davies, T. J.

1985-09-01

The effects of controlled rolling on transformation behavior of two powder forged (P/F) microalloyed vanadium steels and a cast microalloyed vanadium steel were investigated. Rolling was carried out in the austenitic range below the recrystallization temperature. Equiaxed grain structures were produced in specimens subjected to different reductions and different cooling rates. The ferrite grain size decreased with increasing deformation and cooling rate. Ferrite nucleated on second phase particles, deformation bands, and on elongated prior austenite grain boundaries; consequently a high fractional ferrite refinement was achieved. Deformation raised the ferrite transformation start temperature while the time to transformation from the roll finish temperature decreased. Cooling rates in the cast steel were higher than in P/F steels for all four cooling media used, and the transformation start temperatures of cast steels were lower than that of P/F steel. Intragranular ferrite nucleation, which played a vital role in grain refinement, increased with cooling rate. Fully bainitic microstructures were formed at higher cooling rates in the cast steel. In the P/F steels inclusions and incompletely closed pores served as sites for ferrite nucleation, often forming a ‘secondary’ ferrite. The rolling schedule reduced the size of large pores and particle surface inclusions and removed interconnected porosity in the P/F steels.

Precipitation behavior of σ phase in fusion zone of dissimilar stainless steel welds during multi-pass GTAW process

NASA Astrophysics Data System (ADS)

Hsieh, Chih-Chun; Chang, Tao-Chih; Lin, Dong-Yih; Chen, Ming-Che; Wu, Weite

2007-10-01

The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten are welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of σ→ϱ+λ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.

Influence of microscopic strain heterogeneity on the formability of martensitic stainless steel

NASA Astrophysics Data System (ADS)

Bettanini, Alvise Miotti; Delannay, Laurent; Jacques, Pascal J.; Pardoen, Thomas; Badinier, Guillaume; Mithieux, Jean-Denis

2017-10-01

Both finite element modeling and mean field (Mori-Tanaka) modeling are used to predict the strain partitioning in the martensite-ferrite microstructure of an AISI 410 martensitic stainless steel. Numerical predictions reproduce experimental trends according to which macroscopic strength is increased when the dissolution of carbides leads to carbon enrichment of martensite. However, the increased strength contrast of ferrite and martensite favours strain localization and high stress triaxiality in ferrite, which in turn promotes ductile damage development.

Effect of Cu2+ substitution on the magnetic properties of co-precipitated Ni-Cu-Zn ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ramakrishna, K. S.; Srinivas, Ch.; Tirupanyam, B. V.; Ramesh, P. N.; Meena, S. S.; Potukuchi, D. M.; Sastry, D. L.

2017-05-01

Spinel ferrite nanoparticles with chemical equation NixCu0.1Zn0.9-xFe2O4 (x = 0.5, 0.6, 0.7) have been synthsized using co-precipitation method followed by heat treatment at a temperature of 200 °C for 2h. The results of XRD, FE-SEM and VSM studies are reported. XRD patterns confirm the formation of cubic spinel phase of ferrite samples along with small amount of a secondary phase of α-Fe2O3 whose concentration decreases as Ni2+ concentration increases. The crystallite sizes (in the range of 7.5-13.9 nm) increase and the lattice parameter decreases with increase in Ni2+ ion concentration. These values are comparable to those of NiZn ferrite without Cu substitution. It has been observed that there is a considerable reduction in saturation magnetisation (Ms). This and differences in other magnetic parameters are attributed to considerable changes in cation distribution or core shell interactions of NiZn ferrite with 10 mole% Cu substitution in the place of Zn.

Structural transitions and multiferroic properties of high Ni-doped BiFeO3

NASA Astrophysics Data System (ADS)

Betancourt-Cantera, L. G.; Bolarín-Miró, A. M.; Cortés-Escobedo, C. A.; Hernández-Cruz, L. E.; Sánchez-De Jesús, F.

2018-06-01

Nickel doped bismuth ferrite powders, BiFe1-x NixO3 (0 ≤ x ≤ 0.5), were synthesized by high-energy ball milling followed by an annealing at 700 °C. A detailed study about the substitution of Fe3+ by Ni2+ on the crystal structure and multiferroic properties is presented. The X-ray diffraction patterns reveal the formation of rhombohedral structure with small amounts of Bi2Fe4O9 as a secondary phase for x < 0.1. Also it is inferred the stabilization of a Bi25FeO40, sillenite phase, as the amount of Ni2+ substitution increases, reaching up 95.23% of sillenite for x = 0.5. The magnetic behavior indicates the frustration of the G-antiferromagnetic order typical of the un-doped BiFeO3, caused by the presence of small amounts of Ni2+ (x < 0.1) on the structure. The DC conductivity exhibited a little increment with increasing Ni content (up to x = 0.1). Although the conductivity increases, for nickel concentrations of 0.2-0.5, the bismuth ferrites doped with nickel retain their property of being an electrical insulating material. Behavior modifications of electrical conductivity, permittivity and dielectric loss versus frequency are related with crystal structure transformations, when nickel concentration is increased.

Effect of tritium and decay helium on the fracture toughness properties of stainless steel weldments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, M. J.; West, S.; Tosten, M. H.

2008-07-15

J-Integral fracture toughness tests were conducted on tritium-exposed-and- aged Types 304L and 21-6-9 stainless steel weldments in order to measure the combined effects of tritium and its decay product, helium-3 on the fracture toughness properties. Initially, weldments have fracture toughness values about three times higher than base-metal values. Delta-ferrite phase in the weld microstructure improved toughness provided no tritium was present in the microstructure. After a tritium-exposure-and-aging treatment that resulted in {approx}1400 atomic parts per million (appm) dissolved tritium, both weldments and base metals had their fracture toughness values reduced to about the same level. The tritium effect was greatermore » in weldments (67 % reduction vs. 37% reduction) largely because the ductile discontinuous delta-ferrite phase was embrittled by tritium and decay helium. For both base metals and weldments, fracture toughness values decreased with increasing decay helium content in the range tested (50-800 appm). (authors)« less

TRITIUM AND DECAY HELIUM EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL WELDMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, M; Scott West, S; Michael Tosten, M

2007-08-31

J-Integral fracture toughness tests were conducted on tritium-exposed-and-aged Types 304L and 21-6-9 stainless steel weldments in order to measure the combined effects of tritium and its decay product, helium-3 on the fracture toughness properties. Initially, weldments have fracture toughness values about three times higher than base-metal values. Delta-ferrite phase in the weld microstructure improved toughness provided no tritium was present in the microstructure. After a tritium-exposure-and-aging treatment that resulted in {approx}1400 atomic parts per million (appm) dissolved tritium, both weldments and base metals had their fracture toughness values reduced to about the same level. The tritium effect was greater inmore » weldments (67 % reduction vs. 37% reduction) largely because the ductile discontinuous delta-ferrite interfaces were embrittled by tritium and decay helium. Fracture toughness values decreased for both base metals and weldments with increasing decay helium content in the range tested (50-200 appm).« less

Preparation and microwave absorbing properties of carbon/cobalt ferromagnetic composites.

PubMed

Li, Wangchang; Qiao, Xiaojing; Zhao, Hui; Wang, Shuman; Ren, Qingguo

2013-02-01

Carbon/cobalt ferromagnetic light composites with high performance of microwave absorbing properties were prepared by hydrothermal method using starch and hollow cobalt ferrites. It was concluded that after carbonization the spinel structure ferrites changed to Co3Fe7 alloys and the temperature of graphitization was significantly decreased for the catalytic of CoFe2O4/Co3Fe7. The increase of carbon content, and exist of CoFe2O4/Co3Fe7 heightened the microwave absorbing properties. Electromagnetic parameters were tested with 40% of the titled materials and 60% of paraffin wax composites by using HP8722ES vector network analyzer. The reflection was also simulated through transmission line theory. The microwave absorbers exhibited a maximum reflection loss -43 dB and the electromagnetic wave absorption less than -10 dB was found to exceed 3.0 GHz between 11.6 GHz and 15 GHz for an absorber thickness of 2 mm.

Magnetic and electric modulus properties of In substituted Mg–Mn–Cu ferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaiser, M., E-mail: m_kaiser17@hotmail.com

2016-01-15

Highlights: • Ferrite of composition Mg{sub 1−y}Cu{sub y}Mn{sub 0.1}In{sub x}Fe{sub 1.9−x}O{sub 4} with (0.0 ≤ x ≤ 0.4; y = 0.0; 0.1) has been synthesized. • Electric, magnetic and Mössbauer studies have been investigated. • The real and imaginary parts of electric modulus follow the Arrhenius law. • Saturation magnetization increases up to x = 0.2 and thereafter it decreases. • Good agreement between the magnetic and Mössbauer effect studies. - Abstract: Ferrite of composition Mg{sub (1−y)}Cu{sub (y)}Mn{sub (0.1)}In{sub (x)}Fe{sub (1.9−x)}O{sub 4} with (0.0 ≤ x ≤ 0.4; y = 0.0 and y = 0.1) has been synthesized by solidmore » state reaction technique. X-ray diffraction (XRD) patterns of the samples indicated the formation of single-phase cubic spinel structure up to 0.2 and mixed phase for samples x ≥ 0.3. Vibrating sample magnetometer (VSM) measurements indicated that the saturation magnetization increases up to x = 0.2 and thereafter it decreases. Electric modulus analysis was used as a tool to analyze the electrical behavior of the samples. The activation energies extracted from real M′ (ω) and imaginary M″ (ω) peaks were found to follow the Arrhenius law. The area ratio of Fe{sup 3+} at the tetrahedral A- and octahedral B-sites was deduced from the spectral analysis of Mössbauer measurements. The results give evidence that In{sup 3+} replaces Fe{sup 3+} at A-site in the range (0.0 < x ≤ 0.2). As the In{sup 3+} content increases; it replaces Fe at B-site.« less

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

NASA Astrophysics Data System (ADS)

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.

Structural, Optical and Magnetic Properties of Ni-Zn Ferrite Nanoparticles Prepared by a Microwave Assisted Combustion Method.

PubMed

Vijaya, J Judith; Bououdina, M

2016-01-01

Ni-doped ZnFe₂O₄(Ni(x)Zn₁₋xFe₂O₄; x = 0.0 to 0.5) nanoparticles were synthesized by a simple microwave combustion method. The X-ray diffraction confirms the presence of cubic spinel ZnFe₂O₄for all compositions. The lattice parameter decreases with an increase in Ni content resulting in the reduction of lattice strain. High resolution scanning electron microscope images revealed that the as-prepared samples are crystalline with particle size distribution in 40-50 nm range. Optical properties were determined by UV-Visible diffuse reflectance and photoluminescence spectroscopy respectively. The saturation magnetization (Ms) shows the super paramagnetic nature of the sample for x = 0.0-0.2, whereas for x = 0.3-0.5, it shows ferromagnetic nature. The Ms value is 1.638 emu/g for pure ZnFe₂O₄ sample and it increases with increase in Ni content.

Controlled cobalt doping in biogenic magnetite nanoparticles

PubMed Central

Byrne, J. M.; Coker, V. S.; Moise, S.; Wincott, P. L.; Vaughan, D. J.; Tuna, F.; Arenholz, E.; van der Laan, G.; Pattrick, R. A. D.; Lloyd, J. R.; Telling, N. D.

2013-01-01

Cobalt-doped magnetite (CoxFe3 −xO4) nanoparticles have been produced through the microbial reduction of cobalt–iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe2+ site with Co2+, with up to 17 per cent Co substituted into tetrahedral sites. PMID:23594814

Controlled cobalt doping in biogenic magnetite nanoparticles.

PubMed

Byrne, J M; Coker, V S; Moise, S; Wincott, P L; Vaughan, D J; Tuna, F; Arenholz, E; van der Laan, G; Pattrick, R A D; Lloyd, J R; Telling, N D

2013-06-06

Cobalt-doped magnetite (CoxFe3 -xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe(2+) site with Co(2+), with up to 17 per cent Co substituted into tetrahedral sites.

Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir; Shamanian, Morteza; Eskandarian, Masoomeh

The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientationmore » relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld metal. • Weld metal had the lowest texture intensity and ratio of low angle and CSL boundaries.« less

Analysis of ferrite nanoparticles in the flow of ferromagnetic nanofluid.

PubMed

Muhammad, Noor; Nadeem, Sohail; Mustafa, M T

2018-01-01

Theoretical analysis has been carried out to establish the heat transport phenomenon of six different ferromagnetic MnZnFe2O4-C2H6O2 (manganese zinc ferrite-ethylene glycol), NiZnFe2O4-C2H6O2 (Nickel zinc ferrite-ethylene glycol), Fe2O4-C2H6O2 (magnetite ferrite-ethylene glycol), NiZnFe2O4-H2O (Nickel zinc ferrite-water), MnZnFe2O4-H2O (manganese zinc ferrite-water), and Fe2O4-H2O (magnetite ferrite-water) nanofluids containing manganese zinc ferrite, Nickel zinc ferrite, and magnetite ferrite nanoparticles dispersed in a base fluid of ethylene glycol and water mixture. The performance of convective heat transfer is elevated in boundary layer flow region via nanoparticles. Magnetic dipole in presence of ferrites nanoparticles plays a vital role in controlling the thermal and momentum boundary layers. In perspective of this, the impacts of magnetic dipole on the nano boundary layer, steady, and laminar flow of incompressible ferromagnetic nanofluids are analyzed in the present study. Flow is caused by linear stretching of the surface. Fourier's law of heat conduction is used in the evaluation of heat flux. Impacts of emerging parameters on the magneto-thermomechanical coupling are analyzed numerically. Further, it is evident that Newtonian heating has increasing behavior on the rate of heat transfer in the boundary layer. Comparison with available results for specific cases show an excellent agreement.

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

NASA Astrophysics Data System (ADS)

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.

Effect of the adsorption of lithium and borate species on the zeta potential of particles of cobalt ferrite, nickel ferrite, and magnetite.

PubMed

Barale, M; Lefèvre, G; Carrette, F; Catalette, H; Fédoroff, M; Cote, G

2008-12-01

Zetametric measurements on suspensions of oxide particles (cobalt ferrite, nickel ferrite, and magnetite) representative of corrosion products from primary circuits of pressurized water reactors were performed at 25 and 70 degrees C in the presence of lithium and borate species. No effect of lithium ions was observed. Borate species cause a decrease of the isoelectric point (IEP), attributed to the sorption of borate as a negative complex MOB(OH)3(-). A predictive model based on thermodynamic calculations (2-pK and diffuse layer models) of the surface acidity constants from the data of acid-base titrations combined with an empirical relationship between the surface potential Psi 0 and the zeta potential determined by zetametry was developed. A whole set of parameters valid at 25 degrees C, in a range of ionic strength between 10(-4) and 10(-2) molL(-1) and in a range of pH between 4 and 8, was determined for this model. Increase of temperature to 70 degrees C in the presence of borate results in a decrease of IEP for cobalt ferrite and an increase of the IEP for nickel ferrite.

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.

In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Cr eq/Ni eq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Cr eq/Ni eqmore » (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Cr eq/Ni eq. Primary ferrite solidification was observed above 1.75 Cr eq/Ni eq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).« less

Laser weldability of 21Cr-6Ni-9Mn stainless steel: Part II - Weldability diagrams

DOE PAGES

Tate, Stephen B.; Javernick, Daniel Anthony; Lienert, Thomas J.; ...

2016-11-02

In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser welded type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and 7 other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of type 21-6-9. Three travel speeds were used to show the changes in minimum Cr eq/Ni eq for primary ferrite solidification as solidification rate increase d with travel speed . Primary austenite solidification was observed below 1.55 Cr eq/Ni eqmore » (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed , a mix of solidification modes were displayed for alloys from 1.55-1.75 Cr eq/Ni eq. Primary ferrite solidification was observed above 1.75 Cr eq/Ni eq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Lastly, variable cracking behavior was found in alloys with primary austenite solidification, but in general cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P+0.2S).« less

Effect on the structural, DC resistivity and magnetic properties of Zr and Cu co-SubstitutedNi0.5Zn0.5Fe2O4using sol-gel auto-combustion method

NASA Astrophysics Data System (ADS)

Jalaiah, K.; Vijaya Babu, K.; Chandra mouli, K.; Subba Rao, P. S. V.

2018-04-01

The Zr and Cu co-substituted Ni0.5Zn0.5Fe2O4 ferrite nanoparticles have been synthesized by the sol-gel auto combustion method. The XRD patterns confirmed single phase cubic spinel structure for present ferrite systems. The substitution of co-dopants in the spinel structure initially decreases the lattice parameter from x = 0.00 to 0.08 and thereafter increases and the same tendency reflecting in cell volume. The DC resistivity was initially increased later followed the decreasing trend; however the drift mobility of all ferrite samples appears to be in opposite phenomenon to DC resistivity. The saturation magnetization and net magnetic moments of all ferrite samples are decreasing with increasing dopant concentration. The coercive field and Y-K angles are increased with dopant concentration. The initial permeability of all samples is decreased with increasing dopant concentration. The Q-Factor for all samples shows the narrow frequency band with increasing frequency.

Characterization of nitrogen effects in high energy density weldments of Nitronic 40 stainless steel

NASA Astrophysics Data System (ADS)

Pfeif, Erik Andrew

Variation in the welding environment for laser beam welding and electron beam welding can alter the resulting weld chemical composition, microstructure and therefore the mechanical properties. The room temperature mechanical properties of Nitronic 40 stainless steel weld metal from three different heats containing 0.24, 0.28, and 0.31 wt. pct. nitrogen were evaluated for continuous mode Ytterbium doped Fiber laser welds conducted with argon and nitrogen shielding gases, and for electron beam welds. The bulk nitrogen contents were monitored and the resulting properties were then related to microstructural features measured using Electron BackScatter Diffraction (EBSD). Traditional tensile testing of weld metal is conducted on composite tensile bars consisting of base metal and weld metal often leading to failure in the region adjacent to the weld due to strength mismatch at the weld interface. These tests provide composite strength but do not specifically determine the mechanical properties of the heterogeneous weld metal. In this research, microtensile testing was conducted to characterize the properties of the different regions of the weld. The microtensile testing procedures were developed using two geometries of tensile bars measuring the properties through the thickness of 3 mm full penetration welds. In all cases an increase in the strength of the weld metal was found to occur, though the electron beam welds exhibited a higher strength than the laser welds. Standard predictive equations were found to under-predict the strength of the laser welds, even when average grain size or intercept distances were measured. The contribution of nitrogen solid solution strengthening was consistent at approximately 513 MPa per wt. pct. nitrogen. Similar cooling rates and heat inputs allow for a comparison across high energy density welding techniques. Though microstructural differences through the depth of the weld metal were observed as nitrogen vaporization decreased and cooling rates increased. Vermicular ferrite, lacy ferrite and intercellular ferrite were identified as predicted in prior research done on high nitrogen austenitic stainless steels. The resulting laser weld metal microstructures were analyzed with EBSD for grain size and ferrite content measurements, while grain boundary character was determined for a Hansen model used for multi-scale mechanical property measurements. It was found that the low angle grain boundaries were the predominant microstructural feature responsible for strengthening within the weld metal and that this contribution must be accounted for when predicting yield strength of the weld metal.

Feasibility of low-cost magnetic rail designs by integrating ferrite magnets and NdFeB magnets for HTS Maglev systems

NASA Astrophysics Data System (ADS)

Sun, R. X.; Deng, Z. G.; Gou, Y. F.; Li, Y. J.; Zheng, J.; Wang, S. Y.; Wang, J. S.

2015-09-01

Permanent magnet guideway (PMG) is an indispensable part of high temperature superconducting (HTS) Maglev systems. Present PMGs are made of NdFeB magnets with excellent performance and cost much. As another permanent magnet material, the ferrite magnet is weak at magnetic energy product and coercive force, but inexpensive. So, it is a possible way to integrate the ferrite and NdFeB magnets for cutting down the cost of present PMGs. In the paper, the equivalent on magnetic field intensity between ferrite magnets and NdFeB magnets was evaluated by finite element simulation. According to the calculation results, the magnetic field of the PMG integrating ferrite magnets and NdFeB magnets can be increased remarkably comparing with the pure ferrite PMG. It indicates that low-cost PMG designs by integrating the two permanent magnet materials are feasible for the practical HTS Maglev system.

Magnetic filtration process, magnetic filtering material, and methods of forming magnetic filtering material

DOEpatents

Taboada-Serrano, Patricia; Tsouris, Constantino; Contescu, Cristian I; McFarlane, Joanna

2013-10-08

The present invention provides magnetically responsive activated carbon, and a method of forming magnetically responsive activated carbon. The method of forming magnetically responsive activated carbon typically includes providing activated carbon in a solution containing ions of ferrite forming elements, wherein at least one of the ferrite forming elements has an oxidation state of +3 and at least a second of the ferrite forming elements has an oxidation state of +2, and increasing pH of the solution to precipitate particles of ferrite that bond to the activated carbon, wherein the activated carbon having the ferrite particles bonded thereto have a positive magnetic susceptibility. The present invention also provides a method of filtering waste water using magnetic activated carbon.

Effect of Heat Input on Microstructure Evolution and Mechanical Properties in the Weld Heat-Affected Zone of 9Cr-2W-VTa Reduced Activation Ferritic-Martensitic Steel for Fusion Reactor

NASA Astrophysics Data System (ADS)

Moon, Joonoh; Lee, Chang-Hoon; Lee, Tae-Ho; Kim, Hyoung Chan

2015-01-01

The phase transformation and mechanical properties in the weld heat-affected zone (HAZ) of a reduced activation ferritic/martensitic steel were explored. The samples for HAZs were prepared using a Gleeble simulator at different heat inputs. The base steel consisted of tempered martensite and carbides through quenching and tempering treatment, whereas the HAZs consisted of martensite, δ-ferrite, and a small volume of autotempered martensite. The prior austenite grain size, lath width of martensite, and δ-ferrite fraction in the HAZs increased with increase in the heat input. The mechanical properties were evaluated using Vickers hardness and Charpy V-notch impact test. The Vickers hardness in the HAZs was higher than that in the base steel but did not change noticeably with increase in the heat input. The HAZs showed poor impact property due to the formation of martensite and δ-ferrite as compared to the base steel. In addition, the impact property of the HAZs deteriorated more with the increase in the heat input. Post weld heat treatment contributed to improve the impact property of the HAZs through the formation of tempered martensite, but the impact property of the HAZs remained lower than that of base steel.

Analysis of ferrite nanoparticles in the flow of ferromagnetic nanofluid

PubMed Central

Nadeem, Sohail; Mustafa, M. T.

2018-01-01

Theoretical analysis has been carried out to establish the heat transport phenomenon of six different ferromagnetic MnZnFe2O4—C2H6O2 (manganese zinc ferrite-ethylene glycol), NiZnFe2O4—C2H6O2 (Nickel zinc ferrite-ethylene glycol), Fe2O4—C2H6O2 (magnetite ferrite-ethylene glycol), NiZnFe2O4—H2O (Nickel zinc ferrite-water), MnZnFe2O4—H2O (manganese zinc ferrite-water), and Fe2O4—H2O (magnetite ferrite-water) nanofluids containing manganese zinc ferrite, Nickel zinc ferrite, and magnetite ferrite nanoparticles dispersed in a base fluid of ethylene glycol and water mixture. The performance of convective heat transfer is elevated in boundary layer flow region via nanoparticles. Magnetic dipole in presence of ferrites nanoparticles plays a vital role in controlling the thermal and momentum boundary layers. In perspective of this, the impacts of magnetic dipole on the nano boundary layer, steady, and laminar flow of incompressible ferromagnetic nanofluids are analyzed in the present study. Flow is caused by linear stretching of the surface. Fourier’s law of heat conduction is used in the evaluation of heat flux. Impacts of emerging parameters on the magneto—thermomechanical coupling are analyzed numerically. Further, it is evident that Newtonian heating has increasing behavior on the rate of heat transfer in the boundary layer. Comparison with available results for specific cases show an excellent agreement. PMID:29320488

Structuring in fast-quenched ferrite compositions under plasma spraying

NASA Astrophysics Data System (ADS)

Lepeshev, A. A.; Karpov, I. V.; Ushakov, A. V.; Nagibin, G. E.; Dorozhkina, E. A.; Karpova, O. N.; Demin, V. G.; Shaikhadinov, A. A.

2017-06-01

The influence of the quench rate on structuring in spinel ferrites has been studied. It has been found that, when the quench rate is increased, the equilibrium spinel structure gradually becomes disordered. At the first stage, the statistically homogeneous (or almost homogeneous) redistribution of cations over crystal lattice sites has been observed. Then, the fcc lattice of the anion framework breaks down, the translational symmetry disappears, and topological chaos arises. The resulting cluster structural state is thermodynamically unstable, and heating of quenched ferrites causes stepwise energy liberation. As a result, the activity of ferrite powders in solid-state and catalytic reactions rises.

Structural analysis of aluminium substituted nickel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Singh, H. S.; Sangwa, Neha

2018-05-01

Aluminium substituted nickel ferrite nanoparticles were synthesized by High Energy Ball milling (HEBM) of the mixture of α-NiO, α-Al2O3 and α-Fe2O3 followed by annealing at 1000˚C. X-ray diffraction (XRD) and Energy dispersive spectroscopy analysis (EDS) characterization was done for Aluminium substituted nickel ferrite. The structural analysis reveals the formation of the single phase compound. The average grain size was estimated by X-ray diffraction technique ranges from 30 to 10 nm with the increasing concentration of Aluminium. EDS spectra conforms the homogeneous mixing and purity of ferrite.

Effect of solution treatment on microstructure and properties of duplex stainless steel

NASA Astrophysics Data System (ADS)

Wang, X. Y.; Luo, J. M.; Huang, L. Q.; Wang, H. B.; Ma, C. W.

2017-09-01

The influence of solution treatment on microstructure and properties of 2205 duplex stainless steel (DSS) was studied. The microstructure, precipitates and corrosion resisting property were observed and analyzed by means of optical microscopy (OM), scanning electron microscopy (SEM) and electrochemical methods. The results showed that a large number of brittle σ-phase precipitates, which deteriorate the plasticity and corrosion resistance of the material, were easy to produce in the duplex stainless steel under the low temperature. The precipitation of σ-phase can be decreased and the plasticity and corrosion resistance can be improved by increasing solution temperature. In addition, the ferrite content increases with the increase of solution temperature, while less affected by cooling rate.

The Influence of the Induced Ferrite and Precipitates of Ti-bearing Steel on the Ductility of Continuous Casting Slab

NASA Astrophysics Data System (ADS)

Qian, Guoyu; Cheng, Guoguang; Hou, Zibing

2015-11-01

In order to investigate the loss of the ductility of Ti-bearing ship plate steel under 1000 °C, where the ductility begins to reduce rapidly, so the hot ductility of Ti-bearing ship plate steel has been obtained using the Gleeble 1500 thermal-mechanical simulator and also the studies about the effect of grain boundary ferrite films and precipitates containing Ti on the ductility has been carried out. The result showed that the TiN particles precipitating at 950 °C with a larger size and smaller volume fraction cannot effectively suppress the occurrence of recrystallization and the ductility still retains at a high level, although R.A. value presents a certain degree of decline compared with 1000 °C. A large number of smaller Ti(C,N) particles precipitate at 900 °C and can induce the formation of a very small amount of fine grain boundary ferrite, which deteriorates the adhesion strength of the grain boundary, so the R.A. value rapidly reduces to less than 50%. When the temperature falls to close Ae3 (827 °C), the amount of the grain boundary ferrite films increase due to the ferrite phase transformation, but the ferrite film thickness becomes more uneven at the same time, which results in the increase of strain concentration and plays a leading role in causing the decrease of ductility, so the R.A. value has been kept less than 40% as the temperature cooling to 800 °C from 850 °C. When the temperature further decreases, the ductility starts to recover due to the increase of average ferrite film thickness to a greater degree which greatly reduces the strain concentration of the grain boundary.

Influence of low nickel (0.09 wt%) content on microstructure and toughness of P91 steel welds

NASA Astrophysics Data System (ADS)

Arivazhagan, B.; Vasudevan, M.; Kamaraj, M.

2015-05-01

Modified 9Cr-1Mo (P91) steel is widely used as a high temperature structural material in the fabrication of power plant components. Alloying elements significantly influences the microstructure and mechanical properties of P91 steel weldments. The alloying elements manganese and nickel significantly influence the lower critical phase transformation temperature (AC1) as well as tempering response of welds. In the existing published information there was wide spread use of high Mn+Ni filler wire. In the present study, weldment preparation was completed using GTA filler wire having low Nickel content (Mn+Ni of 0.58 wt% including nickel content of 0.09 wt%). Microstructure and mechanical properties characterization was done. There is a requirement on minimum toughness of 47 Joules for P91 steel tempered welds at room temperature. Microstructural observation revealed that the GTA welds have low δ-ferrite content (<0.5%) in the martensite matrix. In the as-weld condition, the toughness was 28 Joules whereas after PWHT at 760 °C-2 h it was 115 Joules. In the present study, toughness of low nickel weld was higher due to low δ-ferrite content (<0.5%), multipass grain refinement and weld metal deposition of single pass per layer of weldment.

Effect of arsenic content and quenching temperature on solidification microstructure and arsenic distribution in iron-arsenic alloys

NASA Astrophysics Data System (ADS)

Xin, Wen-bin; Song, Bo; Huang, Chuan-gen; Song, Ming-ming; Song, Gao-yang

2015-07-01

The solidification microstructure, grain boundary segregation of soluble arsenic, and characteristics of arsenic-rich phases were systematically investigated in Fe-As alloys with different arsenic contents and quenching temperatures. The results show that the solidification microstructures of Fe-0.5wt%As alloys consist of irregular ferrite, while the solidification microstructures of Fe-4wt%As and Fe-10wt%As alloys present the typical dendritic morphology, which becomes finer with increasing arsenic content and quenching temperature. In Fe-0.5wt%As alloys quenched from 1600 and 1200°C, the grain boundary segregation of arsenic is detected by transmission electron microscopy. In Fe-4wt%As and Fe-10wt%As alloys quenched from 1600 and 1420°C, a fully divorced eutectic morphology is observed, and the eutectic Fe2As phase distributes discontinuously in the interdendritic regions. In contrast, the eutectic morphology of Fe-10wt%As alloy quenched from 1200°C is fibrous and forms a continuous network structure. Furthermore, the area fraction of the eutectic Fe2As phase in Fe-4wt%As and Fe-10wt%As alloys increases with increasing arsenic content and decreasing quenching temperature.

Investigations of structural transformation within metal (austenite chromium-manganese steel) at the external surface of steam superheating tubes

NASA Astrophysics Data System (ADS)

Bogachev, V. A.; Pshechenkova, T. P.; Shumovskaya, M. A.

2016-04-01

The elemental composition of an altered layer at the external surface of a steam superheating tube of grade DI59 steel is investigated after long-term operation. It is shown that the layer is located between a scale and a matrix and depleted by silicon, manganese, copper, and chromium with the maximum oxidizer affinity, enriched by iron and nickel to 90%, and mainly composed of the α-Fe phase (ferrite) with the ferromagnetic properties. The layer formed as a result of selective oxidation and diffusion from the matrix into the metal scale with the less standard free energy of the formation of sulfides and oxides. A magnetic ferrite meter is used in the experimental investigation of the layer evolution by testing grade DI59 steel for heat resistance in air environment at temperatures of 585, 650, and 700°C for 15 × 103 h; creep at a temperature of 750°C and a stress of 60 MPa; and long-term strength at temperatures of 700 and 750°C and stresses of from 30 to 80 MPa. Specimens for tests are made of tubes under as-received conditions. The relationship between the ferrite phase content in the surface metal layer and the temperature and time of test is determined. The dependence is developed to evaluate the equivalent temperature for operation of the external surface of steam superheating tubes using data of magnetic ferritometry. It is shown that operation temperatures that are determined by the ferrite phase content and the σ phase concentration in the metal structure of steam superheating tubes with the significant operating time are close. It is proposed to use magnetic ferritometry for revelation of thermal nonuniformity and worst tubes of steam superheaters of HPP boilers.

Could binary mixture of Nd-Ni ions control the electrical behavior of strontium-barium M-type hexaferrite nanoparticles?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Farooq, Saima

2011-05-15

Research highlights: {yields} Strontium-barium hexaferrites (Sr{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19}) in single magnetoplumbite phase solid structure are synthesized by the co-precipitation method. {yields} Structural and electrical properties of Nd-Ni substituted ferrites are investigated. {yields} These ferrite materials possess high electrical resistivity (108 {Omega} cm) that is essential to curb the eddy current loss, which is pre-requisite for surface mount devices. -- Abstract: Cationic substitution in M-type hexaferrites is considered to be an important tool for modification of their electrical properties. This work is part of our comprehensive study on the synthesis and characterization of Nd-Ni doped strontium-barium hexaferrite nanomaterials ofmore » nominal composition Sr{sub 0.5}Ba{sub 0.5-x}Nd{sub x}Fe{sub 12-y}Ni{sub y}O{sub 19} (x = 0.00-0.10; y = 0.00-1.00). Doping with this binary mixture modulates the physical and electrical properties of strontium-barium hexaferrite nanoparticles. Structural and electrical properties of the co-precipitated ferrites are investigated using state-of-the-art techniques. The results of X-ray diffraction analysis reveal that the lattice parameters and cell volume are inversely related to the dopant content. Temperature dependent DC-electrical resistivity measurements infer that resistivity of strontium-barium hexaferrites decreases from 1.8 x 10{sup 10} to 2.0 x 10{sup 8} {Omega} cm whereas the drift mobility, dielectric constant and dielectric loss tangent are directly related to the Nd-Ni content. The results of the study demonstrate a relationship between the modulation of electrical properties of substituted ferrites and nature of cations and their lattice site occupancy.« less

Austenitizing Temperature Effects on the Martensitic Transformation, Microstructural Characteristics, and Mechanical Performance of Modified Ferritic Heat-Resistant Steel

NASA Astrophysics Data System (ADS)

Zhou, Xiaosheng; Liu, Yongchang; Liu, Chenxi; Yu, Liming; Li, Huijun

2018-06-01

The martensitic transformation, microstructural characteristics, and mechanical performance of modified ferritic heat-resistant steels under various austenitizing conditions were investigated by differential scanning calorimetry, microstructural examination, and mechanical tests. When the austenitizing temperature was as high as 1200 °C, a considerable amount of δ-ferrite formed, and the austenite grain size was seen to decrease. Higher austenitizing temperatures were found to promote martensite formation, but retard martensite growth, and the lath width increased as the austenitizing temperature increased. After tempering, rod-like and granular M23C6 carbides appeared within the tempered martensite, the average size and composition of which were dependent on the austenitizing conditions. When the austenitizing temperature was 1050 °C, granular MX with sizes less than 6 nm were identified in the δ-ferrite, while for other austenitizing temperatures, plate MX was inside the δ-ferrite. At 1200 °C, the length of the plate MX was as high as 100 nm, and the number density of plate MX decreased. The steel austenitized at 1150 °C exhibited the best tensile performance. It was found that the presence of a large amount of δ-ferrite would initiate cracking, thereby impeding the tensile strength.

Effects of oleic acid surface coating on the properties of nickel ferrite nanoparticles/PLA composites.

PubMed

Yin, Hong; Chow, Gan-Moog

2009-11-01

Nickel ferrite nanoparticles with or without oleic acid surface coating were mixed with poly(D,L-lactide) (PLA) by double emulsion method. If the nanoparticles were prepared without oleic acid coating, they adsorbed on the PLA surface. If the nanoparticles were coated with oleic acid, they could be readily encapsulated within the PLA microspheres. A slight depression in glass transition temperature was found in all composites and it could be related to the interfacial energies between nanoparticles and PLA. Optimum mixed composite was achieved by reducing interfacial energy. However, loading capacity was limited in this composite. Increasing the amount of nickel ferrite nanoparticles was not useful to increase loading capacity. Cytotoxicity of the composite decreased significantly when nickel ferrite nanoparticles were effectively encapsulated in PLA microspheres. (c) 2008 Wiley Periodicals, Inc.

Corrosion behavior in high heat input welded heat-affected zone of Ni-free high-nitrogen Fe–18Cr–10Mn–N austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moon, Joonoh, E-mail: mjo99@kims.re.kr; Ha, Heon-Young; Lee, Tae-Ho

2013-08-15

The pitting corrosion and interphase corrosion behaviors in high heat input welded heat-affected zone (HAZ) of a metastable high-nitrogen Fe–18Cr–10Mn–N austenitic stainless steel were explored through electrochemical tests. The HAZs were simulated using Gleeble simulator with high heat input welding condition of 300 kJ/cm and the peak temperature of the HAZs was changed from 1200 °C to 1350 °C, aiming to examine the effect of δ-ferrite formation on corrosion behavior. The electrochemical test results show that both pitting corrosion resistance and interphase corrosion resistance were seriously deteriorated by δ-ferrite formation in the HAZ and their aspects were different with increasingmore » δ-ferrite fraction. The pitting corrosion resistance was decreased by the formation of Cr-depleted zone along δ-ferrite/austenite (γ) interphase resulting from δ-ferrite formation; however it didn't depend on δ-ferrite fraction. The interphase corrosion resistance depends on the total amount of Cr-depleted zone as well as ferrite area and thus continuously decreased with increasing δ-ferrite fraction. The different effects of δ-ferrite fraction on pitting corrosion and interphase corrosion were carefully discussed in terms of alloying elements partitioning in the HAZ based on thermodynamic consideration. - Highlights: • Corrosion behavior in the weld HAZ of high-nitrogen austenitic alloy was studied. • Cr{sub 2}N particle was not precipitated in high heat input welded HAZ of tested alloy. • Pitting corrosion and interphase corrosion show a different behavior. • Pitting corrosion resistance was affected by whether or not δ-ferrite forms. • Interphase corrosion resistance was affected by the total amount of δ-ferrite.« less

Structural and magnetic properties of Ni0.8M0.2Fe2O4 (M = Cu, Co) nano-crystalline ferrites

NASA Astrophysics Data System (ADS)

Vijaya Babu, K.; Satyanarayana, G.; Sailaja, B.; Santosh Kumar, G. V.; Jalaiah, K.; Ravi, M.

2018-06-01

Nano-crystalline nickel ferrites are interesting materials due to their large physical and magnetic properties. In the present work, two kinds of spinel ferrites Ni0.8M0.2Fe2O4 (M = Cu, Co) are synthesized by using sol-gel auto-combustion method and the results are compared with NiFe2O4. The structural properties of synthesized ferrites are determined by using X-ray powder diffraction; scanning electron microscope and Fourier transform infrared spectroscopy. The cation distribution obtained from X-ray diffraction show that cobalt/copper occupies only tetrahedral site in spinel lattice. The lattice constant increases with the substitution of cobalt/copper. The structural parameters like bond lengths, tetrahedral and octahedral edges have been varied with the substitution. The microstructural study is carried out by using SEM technique and the average grain size is increased with nickel ferrite. The initial permeability (μi) is improving with the substitution. The observed g-value from ESR is approximately equal to standard value.

Induction of apoptosis in cancer cells by NiZn ferrite nanoparticles through mitochondrial cytochrome C release.

PubMed

Al-Qubaisi, Mothanna Sadiq; Rasedee, Abdullah; Flaifel, Moayad Husein; Ahmad, Sahrim Hj; Hussein-Al-Ali, Samer; Hussein, Mohd Zobir; Zainal, Zulkarnain; Alhassan, Fatah H; Taufiq-Yap, Yun H; Eid, Eltayeb E M; Arbab, Ismail Adam; Al-Asbahi, Bandar A; Webster, Thomas J; El Zowalaty, Mohamed Ezzat

2013-01-01

The long-term objective of the present study was to determine the ability of NiZn ferrite nanoparticles to kill cancer cells. NiZn ferrite nanoparticle suspensions were found to have an average hydrodynamic diameter, polydispersity index, and zeta potential of 254.2 ± 29.8 nm, 0.524 ± 0.013, and -60 ± 14 mV, respectively. We showed that NiZn ferrite nanoparticles had selective toxicity towards MCF-7, HepG2, and HT29 cells, with a lesser effect on normal MCF 10A cells. The quantity of Bcl-2, Bax, p53, and cytochrome C in the cell lines mentioned above was determined by colorimetric methods in order to clarify the mechanism of action of NiZn ferrite nanoparticles in the killing of cancer cells. Our results indicate that NiZn ferrite nanoparticles promote apoptosis in cancer cells via caspase-3 and caspase-9, downregulation of Bcl-2, and upregulation of Bax and p53, with cytochrome C translocation. There was a concomitant collapse of the mitochondrial membrane potential in these cancer cells when treated with NiZn ferrite nanoparticles. This study shows that NiZn ferrite nanoparticles induce glutathione depletion in cancer cells, which results in increased production of reactive oxygen species and eventually, death of cancer cells.

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

NASA Astrophysics Data System (ADS)

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.

Electrical and morphological properties of magnetocaloric nano ZnNi ferrite

NASA Astrophysics Data System (ADS)

Hemeda, O. M.; Mostafa, Nasser Y.; Abd Elkader, Omar H.; Hemeda, D. M.; Tawfik, A.; Mostafa, M.

2015-11-01

A series of Zn1-xNixFe2O4 nano ferrite (with x=0, 0.2, 0.4, 0.6, 0.8, and 1) compositions were synthesized using the combustion technique. The powder samples were characterized by XRD. The X-ray analysis showed that the samples were single phase spinel cubic structure. The AC resistivity decreases by increasing the frequency from 1 kHz to 10 kHz. As the frequency of the applied field increases the hopping of charge carrier also increase, thereby decreasing the resistivity. A shift in dielectric maximum is observed toward higher temperature with increasing the Ni content from 536 K to 560 K at 1 kHz. The HRTEM (high resolution TEM) images of four compositions have lattice spacing which confirms the crystalline nature of the samples. The surface morphology SEM of the sample consists of some grains with relatively homogenies distribution with an average size varying from 0.85 to 0.92 μm. The values for entropy change in this work are still small but are significally higher than the values that have been reported for iron oxide nanoparticle. The magnetic entropy change was calculated from measurements of M (H, T) where H is the magnetic field and T is the temperature. The maximum value of entropy change (ΔS) obtained near Curie temperature which makes these material candidates for magnetocaloric applications.

Effect of heat input on microstructure and properties of hybrid fiber laser-arc weld joints of the 800 MPa hot-rolled Nb-Ti-Mo microalloyed steels

NASA Astrophysics Data System (ADS)

Wang, X.-N.; Zhang, S.-H.; Zhou, J.; Zhang, M.; Chen, C.-J.; Misra, R. D. K.

2017-04-01

Hybrid fiber laser-arc welding (HLAW) process was applied to a novel hot-rolled Nb-Ti-Mo microalloyed steels of 8 mm thickness. The steel is primarily used to manufacture automotive and construction machinery components, etc. To elucidate the effect of heat input on geometry, microstructure and mechanical properties, different heat inputs (3.90, 5.20 and 7.75 kJ/cm) were used by changing the welding speeds. With increased heat input, the depth/width of penetration was decreased, and the geometry of fusion zone (FZ) changed to "wine cup-like" shape. In regard to the microstructural constituents, the martensite content was decreased, but granular bainite (GB) content was increased. The main microstructural difference was in the FZ cross-section at 7.75 kJ/cm because of the effect of thermal source on the top and bottom. The microstructure of the top part consisted of GB, grain boundary ferrite, and acicular ferrite, while the bottom part was primarily lath martensite. The hardness distribution was similar for different heat inputs. Hardness in FZ, coarse-grained HAZ and mixed-grained HAZ was higher than the base metal (BM), but for the fine-grained HAZ was similar or marginally less than the base metal (BM). Tensile strain was concentrated in the BM such that the fracture occurred in this region. In summary, the geometry, microstructure, and mechanical properties of weld joints were superior at heat input of 5.20 kJ/cm.

Preparation and investigation of dc conductivity and relative permeability of epoxy/Li-Ni-Zn ferrite composites

NASA Astrophysics Data System (ADS)

Darwish, M. A.; Saafan, S. A.; El-Kony, D.; Salahuddin, N. A.

2015-07-01

Ferrite nanoparticles - having the compositions Li(x/2)(Ni0.5Zn0.5)(1-x)Fe(2+x/2)O4 (x=0, 0.2, 0.3) - have been prepared by the co-precipitation method. The prepared powders have been divided into groups and sintered at different temperatures (373 K, 1074 K and 1473 K). X-Ray diffraction analysis (XRD) for all samples has confirmed the formation of the desired ferrites with crystallite sizes within the nanoscale (<100 nm). The dc conductivity, the relative permeability and the magnetization of the ferrite samples have been investigated and according to the results, the sample Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 sintered at 1473 K has been chosen to prepare the composites. The particle size of this sample has been recalculated by using JEOL JEM-100SX transmission electron microscope and it has been found about 64.7 nm. Then, a pure epoxy sample and four pristine epoxy resin /Li0.15(Ni0.5Zn0.5)0.7 Fe2.15O4 composites have been prepared using different ferrite contents (20%, 30%, 40%, and 50%) wt.%. These samples have been characterized by Fourier transform infrared (FTIR) spectroscopy and their dc conductivity, relative permeability and magnetization have also been investigated. The obtained results indicate that the investigated composites may be promising candidates for practical applications such as EMI suppressor and high frequency applications.

Analysis of Ductile-Brittle Transition Temperatures for Controlled-Rolled, Microalloyed, C-Mn Based Steels.

DTIC Science & Technology

1988-05-01

This deformation gives an increase in friction stress without much further reduction in grain size. Solid solution and precipitation strengthening are...finishing temperatures because of the measured effect of Mo on lowering the ferrite transformation temperature (I). The precipitation of NbC in the...unchanged. Very probably, Mo, through its solid solution strengthening of ferrite, particularly at 760°C in the austenite-ferrite region, caused the

Factors that determine the level of the yield strength and the return of the yield-point elongation in low-alloy ferrite-martensite steels

NASA Astrophysics Data System (ADS)

Fonstein, N.; Kapustin, M.; Pottore, N.; Gupta, I.; Yakubovsky, O.

2007-09-01

The results of laboratory investigations of dual-phase steels with different contents of carbon and alloying elements after the controlled cooling from the two-phase field and the final low-temperature tempering are presented. It is shown that the ratio of the yield strength to the tensile strength of dual-phase steels, just as the return of the yield-point elongation, depends on the volume fraction of martensite, temperature of the martensite transformation of the austenite component, quenching stresses, concentration of carbon in ferrite, and the temperature of the final tempering.

Study of Zn-Cu Ferrite Nanoparticles for LPG Sensing

PubMed Central

Jain, Anuj; Baranwal, Ravi Kant; Bharti, Ajaya; Vakil, Z.; Prajapati, C. S.

2013-01-01

Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc-copper ferrite, Zn(1−x)CuxFe2O4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples synthesized. With increasing copper concentration, the crystallite size was found to be increased from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy there exhibits porous structure of particles throughout the samples. The pellets of the samples are prepared for LPG sensing characteristics. The sensing is carried out at different operating temperatures (200, 225, and 250°C) with the variation of LPG concentrations (0.2, 0.4, and 0.6 vol%). The maximum sensitivity of 55.33% is observed at 250°C operating for the 0.6 vol% LPG. PMID:23864833

Co2+Ti4+ substituted Z-type barium ferrite with enhanced imaginary permeability and resonance frequency

NASA Astrophysics Data System (ADS)

Li, Z. W.; Guoqing, Lin; Chen, Linfeng; Yuping, Wu; Ong, C. K.

2006-03-01

Co2+Ti4+ substitution for Fe3+ in Co2Z (Ba3Co2Fe24O41) has been prepared. The crystal structure and static and high-frequency magnetic properties have been studied for Ba3Co2+xTixFe24-2xO41 and the corresponding ferrite/polymer composites. As compared to the general Co2Z ferrite/polymer composite, the CoTi substituted ferrite/polymer composite with x=1.0 has a high natural resonance frequency (4.5 GHz), due to its large out-of-plane anisotropy fields Hθ. Furthermore, the maximum imaginary permeability μmax'' is increased by about 50%. The increase is attributed to a decreased damping coefficient, based on the curve-fitted results to the complex permeability spectra. The composites are good electromagnetic attenuation materials with low reflectivity and broad bandwidth at microwave frequencies.

Coupling and power transfer efficiency enhancement of modular and array of planar coils using in-plane ring-shaped inner ferrites for inductive heating applications

NASA Astrophysics Data System (ADS)

Kilic, V. T.; Unal, E.; Demir, H. V.

2017-07-01

We propose and demonstrate a highly effective method of enhancing coupling and power transfer efficiency in inductive heating systems composed of planar coils. The proposed method is based on locating ring-shaped ferrites in the inner side of the coils in the same plane. Measurement results of simple inductive heating systems constructed with either a single or a pair of conventional circular coils show that, with the in-plane inner ferrites, the total dissipated power of the system is increased by over 65%. Also, with three-dimensional full electromagnetic solutions, it is found that power transfer efficiency of the system is increased up to 92% with the inner ferrite placement. The proposed method is promising to be used for efficiency enhancement in inductive heating applications, especially in all-surface induction hobs.

Structural and ambient/sub-ambient temperature magnetic properties of Er-substituted cobalt-ferrites synthesized by sol-gel assisted auto-combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prathapani, Sateesh; Department of Metallurgical Engineering and Materials Science, IIT-Bombay, Mumbai 400076; Jayaraman, Tanjore V., E-mail: ddas@uohyd.ernet.in, E-mail: tvjayaraman@gmail.com

2014-07-14

Er-substituted cobalt-ferrites CoFe{sub 2−x}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04) were synthesized by sol-gel assisted auto-combustion method. The precursor powders were calcined at 673–873 K for 4 h, subsequently pressed into pellets and sintered at 1273 K for 4 h. X-ray diffraction (XRD) confirmed the presence of the spinel phase for all the compositions and, additional orthoferrite phase for higher compositions (x = 0.03 and 0.04). The XRD spectra and the Transmission Electron Microscopy micrographs indicate that the nanocrystalline particulates of the Er-substituted cobalt ferrites have crystallite size of ∼120–200 nm. The magnetization curves show an increase in saturation magnetization (M{sub S}) and coercivity (H{sub C}) for Er-substituted cobalt-ferrites atmore » sub-ambient temperatures. M{sub S} for CoFe{sub 2}O{sub 4}, CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.97}Er{sub 0.03}O{sub 4} peak at 89.7 Am{sup 2}/kg, 89.3 Am{sup 2}/kg, 88.8 Am{sup 2}/kg, and 87.1 Am{sup 2}/kg, respectively, at a sub-ambient temperature of ∼150 K. H{sub C} substantially increases with decrease in temperature for all the compositions, while it peaks at x = 0.01−0.02 at all temperatures. The combination of Er content—x ∼ 0.02 and the temperature—∼5 K provides the maximum H{sub C} ∼ 984 kA/m. Er-substituted cobalt-ferrites have higher cubic anisotropy constant, K{sub 1}, compared to pure cobalt-ferrite at ambient/sub-ambient temperatures. K{sub 1} gradually increases for all compositions in the temperature decreasing from 300 to 100 K. While K{sub 1} peaks at ∼150 K for pure cobalt-ferrite, it peaks at ∼50 K for CoFe{sub 0.99}Er{sub 0.01}O{sub 4}, CoFe{sub 0.98}Er{sub 0.02}O{sub 4}, and CoFe{sub 0.96}Er{sub 0.04}O{sub 4}. The M{sub S} (∼88.7 Am{sup 2}/kg), at 5 K, for Er substituted cobalt-ferrite is close to the highest values reported for Sm and Gd substituted cobalt-ferrites. The M{sub S} (∼83.5 Am{sup 2}/kg) at 300 K for Er-substituted cobalt-ferrite is the highest among the lanthanide series element substituted cobalt-ferrites. The H{sub C} (at 5 K) for Er substituted cobalt-ferrite is close to the highest values observed for La, Ce, Nd, Sm, and Gd substituted cobalt-ferrites.« less

Performance of ferritic stainless steels for automobile muffler corrosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarutani, Y.; Hashizume, T.

1995-11-01

Corrosion behavior of ferritic stainless steels was studied in artificial exhaust gas condensates containing corrosive ions such as Cl{sup {minus}} and SO{sub 3}{sup 2{minus}}. Continuous immersion tests in flasks and Dip and Dry tests by using the alternate corrosion tester with a heating system clarified the effects of chromium and molybdenum additions on the corrosion resistance of a ferritic stainless steel in the artificial exhaust gas condensates. Effects of surface oxidation on the corrosion behavior were investigated in a temperature range of 573K to 673K. Oxidation of 673K reduced the corrosion resistance of the ferritic stainless steels in the artificialmore » environment of the automobile muffler. Particulate matter deposited on the muffler inner shell from the automobile exhaust gas was also examined. Deposited particulate matter increased the corrosion rate of the ferritic stainless steel. Finally, the authors also investigated the corrosion of the automobile mufflers made of Type 436L ferritic stainless steel with 18% chromium-1.2% molybdenum after 24 months, in Japan. The sets of results clarified that Type 436L ferritic stainless steel as the material for the automobile muffler exhibited acceptable corrosion resistance.« less

Influence of La3+ Substitution on Structure, Morphology and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite

PubMed Central

Dasan, Y. K.; Guan, B. H.; Zahari, M. H.; Chuan, L. K.

2017-01-01

Lanthanum substituted Ni-Zn ferrite nanoparticles (Ni0.5Zn0.5LaxFe1-xO4; 0.00 ≤x≤ 1.00) synthesized by sol-gel method were presented. X-ray diffraction patterns reveal the typical single phase spinel cubic ferrite structure, with the traces of secondary phase for lanthanum substituted nanocrystals. In addition, the structural analysis also demonstrates that the average crystallite size varied in the range of 21–25 nm. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. Surface morphology of both substituted and unsubstituted Ni-Zn ferrite nanoparticle samples was studied using FESEM technique and it indicates a significant increase in the size of spherical shaped particles with La3+ substitution. Magnetic properties of all samples were analyzed using vibrating sample magnetometer (VSM). The results revealed that saturation magnetization (Ms) and coercivity (Hc) of La3+ substituted samples has decreased as compared to the Ni-Zn ferrite samples. Hence, the observed results affirm that the lanthanum ion substitution has greatly influenced the structural, morphology and magnetic properties of Ni-Zn ferrite nanoparticles. PMID:28081257

Influence of La3+ Substitution on Structure, Morphology and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite.

PubMed

Dasan, Y K; Guan, B H; Zahari, M H; Chuan, L K

2017-01-01

Lanthanum substituted Ni-Zn ferrite nanoparticles (Ni0.5Zn0.5LaxFe1-xO4; 0.00 ≤x≤ 1.00) synthesized by sol-gel method were presented. X-ray diffraction patterns reveal the typical single phase spinel cubic ferrite structure, with the traces of secondary phase for lanthanum substituted nanocrystals. In addition, the structural analysis also demonstrates that the average crystallite size varied in the range of 21-25 nm. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. Surface morphology of both substituted and unsubstituted Ni-Zn ferrite nanoparticle samples was studied using FESEM technique and it indicates a significant increase in the size of spherical shaped particles with La3+ substitution. Magnetic properties of all samples were analyzed using vibrating sample magnetometer (VSM). The results revealed that saturation magnetization (Ms) and coercivity (Hc) of La3+ substituted samples has decreased as compared to the Ni-Zn ferrite samples. Hence, the observed results affirm that the lanthanum ion substitution has greatly influenced the structural, morphology and magnetic properties of Ni-Zn ferrite nanoparticles.

Factors Affecting the Inclusion Potency for Acicular Ferrite Nucleation in High-Strength Steel Welds

NASA Astrophysics Data System (ADS)

Kang, Yongjoon; Jeong, Seonghoon; Kang, Joo-Hee; Lee, Changhee

2016-06-01

Factors affecting the inclusion potency for acicular ferrite nucleation in high-strength weld metals were investigated and the contribution of each factor was qualitatively evaluated. Two kinds of weld metals with different hardenabilities were prepared, in both, MnTi2O4-rich spinel formed as the predominant inclusion phase. To evaluate the factors determining the inclusion potency, the inclusion characteristics of size, phase distribution in the multiphase inclusion, orientation relationship with ferrite, and Mn distribution near the inclusion were analyzed. Three factors affecting the ferrite nucleation potency of inclusions were evaluated: the Baker-Nutting (B-N) orientation relationship between ferrite and the inclusion; the formation of an Mn-depleted zone (MDZ) near the inclusion; and the strain energy around the inclusion. Among these, the first two factors were found to be the most important. In addition, it was concluded that the increased chemical driving force brought about by the formation of an MDZ contributed more to the formation of acicular ferrite in higher-strength weld metals, because the B-N orientation relationship between ferrite and the inclusion was less likely to form as the transformation temperature decreased.

Effect of Nitrogen on Transformation Behaviors and Microstructure of V-N Microalloyed Steel

NASA Astrophysics Data System (ADS)

Zhao, Baochun; Zhao, Tan; Li, Guiyan; Lu, Qiang

Multi-pass deformation simulation tests were performed on V-N microalloyed steels with different nitrogen addition by using a Gleeble-3800 thermo-mechanical simulator and the corresponding continuous cooling transformation (CCT) diagrams were determined by thermal dilation method and metallographic method. The deformed austenite transformation behavior and resultant microstructure of the tested steels were studied. Furthermore, the effect of nitrogen addition on the transformation behavior and microstructure evolution was analyzed. The results show that the transformed microstructures in the three tested steels are ferrite, pearlite and bainite respectively while the transformation temperatures are not the same. For the two tested steel with higher nitrogen additions, higher ferrite start temperature and critical cooling rates are observed. Furthermore, an increase in nitrogen addition leads to increasing quantities of ferrite and the transformed ferrite is smaller in size. The hardness test results reveal that the hardness number increases with increasing nitrogen addition at low cooling rate while the value tends to be smaller due to increasing nitrogen addition at high cooling rate. Therefore, the hardness number of the steel with high nitrogen addition is not so sensitive to cooling rate as that of the steel with low nitrogen addition.

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

Duplex stainless steel fracture surface analysis using X-ray fractography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajanna, K.; Pathiraj, B.; Kolster, B.H.

1997-02-01

The fatigue fracture surface of a duplex stainless steel was analyzed using x-ray fractography. A lower than average austenite content was observed at the fracture surface due to the transformation of austenite into deformation-induced martensite. The influence of fatigue cycling on the transformation was confined to a depth of about 30 {micro}m below the fracture surface. X-ray analyses of both the ferrite-martensite and the austenite phases indicated residual stresses ({sigma}{sub r}) increasing with depth from the fracture surface and reaching a maximum some tens of microns below the fracture surface. The lower {sigma}{sub r} observed at the fracture surface hasmore » been attributed to the stress relaxation effects caused by the new fracture surfaces created in the crack growth process. The observed decrease in full width at half maximum (FWHM) in the ferrite-martensite phase was presumed to be due to the dynamic recovery effect that was likely to occur within the material close to the crack tip as a consequence of fatigue cycling.« less

USSR and Eastern Europe Scientific Abstracts, Materials Science and Metallurgy. Number 40.

DTIC Science & Technology

1976-11-01

means of increasing the deformability of two- phase martensite - ferrite steels during subsequent cold rolling, as well as austenite- ferrite steels ...carbon steel , VT-4 titanium alloy and M-l copper . The specimens were placed in July 1972 and removed in April 1974. Tables are given summarizing...between the degree of development of the a -*• y conversion at the deformation focus in steels of the martensite - ferrite class and the position of

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia-Mateo, Carlos, E-mail: cgm@cenim.csic.es

Since the major strengthening mechanisms in nanocrystalline bainitic steels arise from the exceptionally small size of the bainitc ferrite plate, accurate determination of this parameter is fundamental for quantitative relating the microstructure to the mechanical properties. In this work, the thickness of the bainitic ferrite subunits obtained by different bainitic heat treatments was determined in two steels, with carbon contents of 0.3 and 0.7 wt.%, from SEM and TEM micrographs. As these measurements were made on 2D images taken from random sections, the method includes some stereological correction factors to obtain accurate information. Finally, the determined thicknesses of bainitic ferritemore » plates were compared with the crystallite size calculated from the analysis of X-ray diffraction peak broadening. Although in some case the values obtained for crystallite size and plate thickness can be similar, this study confirms that indeed they are two different parameters. - Highlights: •Bainitic microstructure in a nanostructured and sub-micron steel •Bainitic ferrite plate thickness measured by SEM and TEM •Crystallite size determined by X-ray analysis.« less

Induction of apoptosis in cancer cells by NiZn ferrite nanoparticles through mitochondrial cytochrome C release

PubMed Central

Al-Qubaisi, Mothanna Sadiq; Rasedee, Abdullah; Flaifel, Moayad Husein; Ahmad, Sahrim Hj; Hussein-Al-Ali, Samer; Hussein, Mohd Zobir; Zainal, Zulkarnain; Alhassan, Fatah H; Taufiq-Yap, Yun H; Eid, Eltayeb EM; Arbab, Ismail Adam; Al-Asbahi, Bandar A; Webster, Thomas J; Zowalaty, Mohamed Ezzat El

2013-01-01

The long-term objective of the present study was to determine the ability of NiZn ferrite nanoparticles to kill cancer cells. NiZn ferrite nanoparticle suspensions were found to have an average hydrodynamic diameter, polydispersity index, and zeta potential of 254.2 ± 29.8 nm, 0.524 ± 0.013, and −60 ± 14 mV, respectively. We showed that NiZn ferrite nanoparticles had selective toxicity towards MCF-7, HepG2, and HT29 cells, with a lesser effect on normal MCF 10A cells. The quantity of Bcl-2, Bax, p53, and cytochrome C in the cell lines mentioned above was determined by colorimetric methods in order to clarify the mechanism of action of NiZn ferrite nanoparticles in the killing of cancer cells. Our results indicate that NiZn ferrite nanoparticles promote apoptosis in cancer cells via caspase-3 and caspase-9, downregulation of Bcl-2, and upregulation of Bax and p53, with cytochrome C translocation. There was a concomitant collapse of the mitochondrial membrane potential in these cancer cells when treated with NiZn ferrite nanoparticles. This study shows that NiZn ferrite nanoparticles induce glutathione depletion in cancer cells, which results in increased production of reactive oxygen species and eventually, death of cancer cells. PMID:24204141

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Williams; Zhao, Ji-Cheng

Cost effective and high performance alloys that are capable of operating at 760 °C or higher for extended periods of time under a very aggressive environment are critically required for the design and development of advanced ultrasupercritical (AUSC) boilers and steam turbines. Finely dispersed Laves phase precipitates have been shown by Takeyama and co-workers to be a viable strengthening mechanism in high temperature austenitic steels. There is currently no straightforward theory that can predict what other intermetallic phases can serve as potent precipitation-strengthening phases for steels; thus we employed a highly effective dual-anneal diffusion multiple (DADM) approach to screen formore » viable strengthening precipitates over a wide range of compositions. From the Fe-Co-Cr-Ni-Mo DADMs, the Fe-Cr-Mo based Chi phase was identified as a new strengthening phase for high temperature ferritic steels; and from the Fe-Mn-Cr-Nb-Ni-Mo-FeAl DADMs, the Laves phase was identified as a viable strengthening precipitate in Fe-Mn and Fe-Ni based austenitic steels. After identification of viable strengthening phases from the DADMs that covered compositions in the basic ternary and quaternary systems, we employed computation thermodynamics to perform multicomponent alloy design and optimization. For the new the Chi-phase strengthened steels, we performed thermodynamic calculations to vary the volume fraction of the Chi phase and introduced Nb and carbon to promote the formation of stable carbides for grain size control during solution heat treatment. For the Fe-Ni-Mn based austenitic steels, we performed extensive parametric optimization of compositions in order to reduce the expensive Ni content, add Cr and Al for oxidation resistance, and balance the alloying contents (Ni, Mn, Cr, Al, Mo) to suppress the ferritic phase and promote the austenitic matrix phase. Four steels (two ferritic + two austenitic) were designed and tested. The two Chi-phase strengthened ferritic steels exhibited excellent oxidation resistance and good creep-rupture strength at moderate temperatures, considering their ferritic matrix that usually results in lower creep resistance than austenitic steels. These steels showed brittleness and sample-to-sample variability in ductility. The low ductility might be due to the macro segregation during solidification or the significant grain growth during the solution heat treatments. We believe there is no inherent brittleness based on the chemistry of the steels. The creep-rupture performance of the steels is comparable to the 9Cr steels. Due to their ferritic matrix, the new Chi-phase strengthened ferritic steels may not be suited for the 760 °C AUSC applications, but they are very good candidates for intermediate temperature applications due to their outstanding oxidation resistance and high strength. Further study is required to find the source of low and highly variable ductility. We believe the compositions of the Chi-phase strengthened steels are not inherently brittle. The Chi-phase strengthened ferritic steels may also be excellent candidates for intermediate-temperature and room-temperature cast stainless steels, thus we highly recommend further investigations. The two Mn-containing austenitic steels based on the Laves phase showed good ductility, excellent oxidation resistance (slightly inferior to the two ferritic steels) at high temperatures and moderate creep strength. The creep-strength of the two austenitic steels based on the Larson-Miller parameters is higher than that of the traditional 316 stainless steels, but lower than the alumina-forming alloys (AFAs) developed at Oak Ridge National Laboratories. We do not recommend high priority in further studying these compositions unless higher Cr alloys are required for hot-corrosion resistance.« less

Atom probe study of vanadium interphase precipitates and randomly distributed vanadium precipitates in ferrite.

PubMed

Nöhrer, M; Zamberger, S; Primig, S; Leitner, H

2013-01-01

Atom probe tomography and transmission electron microscopy were used to examine the precipitation reaction in the austenite and ferrite phases in vanadium micro-alloyed steel after a thermo-mechanical process. It was observed that only in the ferrite phase precipitates could be found, whereupon two different types were detected. Thus, the aim was to reveal the difference between these two types. The first type was randomly distributed precipitates from V supersaturated ferrite and the second type V interphase precipitates. Not only the arrangement of the particles was different also the chemical composition. The randomly distributed precipitates consisted of V, C and N in contrast to that the interphase precipitates showed a composition of V, C and Mn. Furthermore the randomly distributed precipitates had maximum size of 20 nm and the interphase precipitates a maximum size of 15 nm. It was assumed that the reason for these differences is caused by the site in which they were formed. The randomly distributed precipitates were formed in a matrix consisting mainly of 0.05 at% C, 0.68 at% Si, 0.03 at% N, 0.145 at% V and 1.51 at% Mn. The interphase precipitates were formed in a region with a much higher C, Mn and V content. Copyright © 2013 Elsevier Ltd. All rights reserved.

Influence of hydrostatic pressure on the switching time and switching coefficient of NiZnCo ferrites

NASA Astrophysics Data System (ADS)

Romanowski, S.; Goldberg, S.

1980-04-01

Results of the investigation of the effect of hydrostatic pressure on the pulse performance of NiZnCo ferrites with square hysteresis loop are given. It is stated that with increasing hydrostatic pressure, the threshold field strength increases, the switching coefficient value decreases, while the switching time value may increase monotonically or reach a maximum depending on the magnetizing field strength.

Effect of Sintering Temperature on Magnetic Core-Loss Properties of a NiCuZn Ferrite for High-Frequency Power Converters

NASA Astrophysics Data System (ADS)

Yan, Yi; Ngo, Khai D. T.; Hou, Dongbin; Mu, Mingkai; Mei, Yunhui; Lu, Guo-Quan

2015-10-01

In an effort to find a magnetic material for making low-loss magnetic components for high-power-density converters, we investigated the magnetic core-loss characteristics of a commercial NiCuZn ferrite (LSF 50) at 5 MHz as a function of the sintering temperature of the ferrite powder. The ferrite powder was compacted into toroid cores and then sintered at 850°C, 900°C, 950°C, 1000°C, and 1050°C for 2 h. The sintered densities of the cores increased at higher sintering temperatures. The magnetic properties of the sintered cores—complex permeability and core-loss density—were measured. We found that both the real and imaginary parts of the relative permeability increased with sintering temperature. The core-loss results at 5 MHz showed that the cores sintered at 950°C and 1000°C had the lowest core-loss densities, being two to three times lower than that of a commercial NiZn ferrite (4F1) core. Microstructures of the sintered cores were examined by scanning electron microscopy; the grains grew significantly at higher sintering temperatures.

Influence of thermo-mechanical treatment in ferritic phase field on microstructure and mechanical properties of reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Prakash; Vanaja, J.; Laha, K.; Nageswara Rao, G. V. S.

2018-03-01

The present study focuses on the evaluation of microstructure and mechanical properties of reduced activation ferritic-martensitic (RAFM) steel (9Cr-1W-0.06Ta) subjected to thermo-mechanical treatment (TMT) in ferritic phase field. The results obtained were compared with the steel in conventional normalised plus tempered (N+T) condition. The microstructure of the steel in N+T and TMT conditions was assessed by optical and scanning electron microscopes. Hardness, tensile and creep studies were carried out and the results were correlated with the microstructural studies. While the TMT processed steel resulted in coarser prior austenite grains and exhibited ferritic microstructure with large distribution of fine M23C6 and MX precipitates, the N+T steel reveals tempered martensitic structure with finer prior austenitic grains with coarser M23C6 and MX precipitates. Although ferritic structure is present in TMT processed steel, it exhibits better tensile and creep rupture strengths than N+T steel due to the presence of increased dislocation density and finer distribution of precipitates.

Solidification and solidification cracking in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Savage, Warren F.

1986-04-01

The solidification behavior of three heats of nitrogen-strengthened austenitic stainless steel was examined and was correlated with solidification mode predictions and with hot cracking resistance. The heat of NITRONIC* 50 solidified by the austenitic-ferrite mode, and the NITRONIC 50W and NITRONIC 50W - Nb heats solidified by the ferritic-austenitic mode. This behavior was in good agreement with predictions based on Espy’s formulas for Cr and Ni equivalents. Both the NITRONIC 50W and NITRONIC 50W + Nb welds contained primary delta-ferrite, with the latter weld and the NITRONIC 50 weld also containing some eutectic ferrite. Solute profiles in austenite near the eutectic ferrite showed decreasing Fe and increasing Cr, Ni, Mn, and Mo relative to austenite in the dendrite cores. Numerous Nb-rich precipitates were found on the eutectic ferrite/austenite interfaces and within the eutectic ferrite. The precipitates were mainly Nb(C, N), with some Z-phase, a Nb-rich nitride, also detected. One instance of the transformation of eutectic ferrite to sigma-phase was observed to have occurred during cooling of the NITRONIC 50 weld. Hot cracking was seen in the NITRONIC 50 and NITRONIC 50W + Nb welds and resulted from the formation of a niobium carbonitride eutectic in the interdendritic regions. In the absence of Nb, the NITRONIC 50W heat formed no observable eutectic constituents and did not hot crack. The presence of hot cracks in the NITRONIC 50W + Nb weld indicates that solidification by the ferritic-austenitic mode did not counteract the effects of small Nb additions.

Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

PubMed

Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

2014-05-14

Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C.

Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel.

PubMed

Guo, Yanjun; Hu, Jincheng; Li, Jin; Jiang, Laizhu; Liu, Tianwei; Wu, Yanping

2014-09-12

The effect of annealing temperature (1000-1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and potentiostatic critical pitting temperature (CPT). The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP). The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN) of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN.

Effect of Annealing Temperature on the Mechanical and Corrosion Behavior of a Newly Developed Novel Lean Duplex Stainless Steel

PubMed Central

Guo, Yanjun; Hu, Jincheng; Li, Jin; Jiang, Laizhu; Liu, Tianwei; Wu, Yanping

2014-01-01

The effect of annealing temperature (1000–1150 °C) on the microstructure evolution, mechanical properties, and pitting corrosion behavior of a newly developed novel lean duplex stainless steel with 20.53Cr-3.45Mn-2.08Ni-0.17N-0.31Mo was studied by means of optical metallographic microscopy (OMM), scanning electron microscopy (SEM), magnetic force microscopy (MFM), scanning Kelvin probe force microscopy (SKPFM), energy dispersive X-ray spectroscopy (EDS), uniaxial tensile tests (UTT), and potentiostatic critical pitting temperature (CPT). The results showed that tensile and yield strength, as well as the pitting corrosion resistance, could be degraded with annealing temperature increasing from 1000 up to 1150 °C. Meanwhile, the elongation at break reached the maximum of 52.7% after annealing at 1050 °C due to the effect of martensite transformation induced plasticity (TRIP). The localized pitting attack preferentially occurred at ferrite phase, indicating that the ferrite phase had inferior pitting corrosion resistance as compared to the austenite phase. With increasing annealing temperature, the pitting resistance equivalent number (PREN) of ferrite phase dropped, while that of the austenite phase rose. Additionally, it was found that ferrite possessed a lower Volta potential than austenite phase. Moreover, the Volta potential difference between ferrite and austenite increased with the annealing temperature, which was well consistent with the difference of PREN. PMID:28788201

Spinel NixZn1-xFe2O4 (0.0 ≤ x ≤ 1.0) nano-photocatalysts: Synthesis, characterization and photocatalytic degradation of methylene blue dye

NASA Astrophysics Data System (ADS)

Padmapriya, G.; Manikandan, A.; Krishnasamy, V.; Jaganathan, Saravana Kumar; Antony, S. Arul

2016-09-01

Spinel NixZn1-xFe2O4 (x = 0.0 to 1.0) nanoparticles were successfully synthesized by a simple microwave combustion method (MCM) using metal nitrates as raw materials and glycine as the fuel. The structural, morphological and opto-magnetic properties of the spinel NixZn1-xFe2O4 ferrites were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern, UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). Powder XRD, and EDX analysis was confirmed the formation of pure phase of spinel ferrites. HR-SEM and HR-TEM analysis was confirmed the formation of sphere like-particle morphology of the samples with smaller agglomeration. VSM analysis clearly showed the superparamagnetic and ferromagnetic nature of the samples. The Ms value is 3.851 emu/g for undoped ZnFe2O4 sample and it increased with increase in Ni content. Photo-catalytic degradation (PCD) of methylene blue (MB) dye using the samples were carried out and observed good PCD results.

Effect of Er doping on the structural and magnetic properties of cobalt-ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prathapani, Sateesh; Vinitha, M.; Das, D., E-mail: ddse@uohyd.ernet.in

2014-05-07

Nanocrystalline particulates of Er doped cobalt-ferrites CoFe{sub (2−x)}Er{sub x}O{sub 4} (0 ≤ x ≤ 0.04), were synthesized, using sol-gel assisted autocombustion method. Co-, Fe-, and Er- nitrates were the oxidizers, and malic acid served as a fuel and chelating agent. Calcination (400–600 °C for 4 h) of the precursor powders was followed by sintering (1000 °C for 4 h) and structural and magnetic characterization. X-ray diffraction confirmed the formation of single phase of spinel for the compositions x = 0, 0.01, and 0.02; and for higher compositions an additional orthoferrite phase formed along with the spinel phase. Lattice parameter of the doped cobalt-ferrites was higher than that of pure cobalt-ferrite.more » The observed red shift in the doped cobalt-ferrites indicates the presence of induced strain in the cobalt-ferrite matrix due to large size of the Er{sup +3} compared to Fe{sup +3}. Greater than two-fold increase in coercivity (∼66 kA/m for x = 0.02) was observed in doped cobalt-ferrites compared to CoFe{sub 2}O{sub 4} (∼29 kA/m)« less

Effect of Pipe Body Alloy on Weldability of X80 Steel

NASA Astrophysics Data System (ADS)

Kong, Xianglei; Huang, Guojian; Fu, Kuijun; Liu, Fangfang; Huang, Minghao; Zhang, Yinghui

Effect of Mo, Ni, and Cr on impact property of pipe seam and heat-affected zone (HAZ) of X80 steel was investigated by thermal simulation test and butt welding test. The results showed that, there was an obvious relationship between strip's composition and the toughness of weld and HAZ, the more content of Mo, Ni and less of Cr in the strip matrix, the better of impact toughness of weld and HAZ. Metallographic microscope was used to compare microstructures of welding specimens, every welded seam microstructure was mainly acicular ferrite (AF) and a little volume of proeutectoid ferrite (PF), and with some granular precipitations on original austenite grain boundary, the difference was that there were more PF and less precipitations of the specimen with more content of Mo, Ni and less of Cr in the strip matrix. Because of the high price of Mo and Ni, alloy design must be considered comprehensively with the cost and property requirements in the production.

Exploring Reaction Conditions to Improve the Magnetic Response of Cobalt-Doped Ferrite Nanoparticles

PubMed Central

Galarreta, Itziar; Gil de Muro, Izaskun; Lezama, Luis

2018-01-01

With the aim of studying the influence of synthesis parameters in structural and magnetic properties of cobalt-doped magnetite nanoparticles, Fe3−xCoxO4 (0 < x < 0.15) samples were synthetized by thermal decomposition method at different reaction times (30–120 min). The Co ferrite nanoparticles are monodisperse with diameters between 6 and 11 nm and morphologies depending on reaction times, varying from spheric, cuboctahedral, to cubic. Chemical analysis and X-ray diffraction were used to confirm the composition, high crystallinity, and pure-phase structure. The investigation of the magnetic properties, both magnetization and electronic magnetic resonance, has led the conditions to improve the magnetic response of doped nanoparticles. Magnetization values of 86 emu·g−1 at room temperature (R.T.) have been obtained for the sample with the highest Co content and the highest reflux time. Magnetic characterization also displays a dependence of the magnetic anisotropy constant with the varying cobalt content. PMID:29370104

Optimization of the behavior of CTAB coated cobalt ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Kumari, Mukesh; Bhatnagar, Mukesh Chander

2018-05-01

In this work, we have synthesized cetyltrimethyl ammonium bromide (CTAB) mixed cobalt ferrite (CoFe2O4) nanoparticles (NPs) using sol-gel auto-combustion method taking a different weight percent ratio of CTAB i.e., 0%, 1%, 2%, 3% and 4% with respect to metal nitrates. The morphological, structural and magnetic properties of these NPs are characterized by high resolution transmitted electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectrometer and physical property measurement system (PPMS). It has been found that saturation magnetization of cobalt ferrite increases with increase in crystalline size of the NPs. Saturation magnetization and crystallite size both were found to be lowest in the case of sample containing 2% CTAB.

Contributions from research on irradiated ferritic/martensitic steels to materials science and engineering

NASA Astrophysics Data System (ADS)

Gelles, D. S.

1990-05-01

Ferritic and martensitic steels are finding increased application for structural components in several reactor systems. Low-alloy steels have long been used for pressure vessels in light water fission reactors. Martensitic stainless steels are finding increasing usage in liquid metal fast breeder reactors and are being considered for fusion reactor applications when such systems become commercially viable. Recent efforts have evaluated the applicability of oxide dispersion-strengthened ferritic steels. Experiments on the effect of irradiation on these steels provide several examples where contributions are being made to materials science and engineering. Examples are given demonstrating improvements in basic understanding, small specimen test procedure development, and alloy development.

Combustion synthesis and structural analysis of nanocrystalline nickel ferrite at low temperature regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugavel, T., E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Raj, S. Gokul, E-mail: gokulrajs@hotmail.com, E-mail: shanmugavelnano@gmail.com; Rajarajan, G.

2015-06-24

Combustion synthesis of single phase Nickel ferrite was successfully achieved at low temperature regime. The obtained powders were calcinated to increase the crystallinity and their characterization change due to calcinations is investigated in detail. Citric acid used as a chelating agent for the synthesis of nickel ferrite. Pure single phase nickel ferrites were found at this low temperature. The average crystalline sizes were measured by using powder XRD measurements. Surface morphology was investigated through Transmission Electron Microscope (TEM). Particle size calculated in XRD is compared with TEM results. Magnetic behaviour of the samples is analyzed by using Vibrating Sample Magnetometermore » (VSM). Saturation magnetization, coercivity and retentivity are measured and their results are discussed in detail.« less

Bainitic stabilization of austenite in low alloy sheet steels

NASA Astrophysics Data System (ADS)

Brandt, Mitchell L.

The stabilization of retained austenite in 'triple phase' ferrite/bainite/austenite sheet steels by isothermal bainite transformation after intercritical annealing has been studied in 0.27C-1.5Si steels with 0.8 to 2.4Mn. Dilatometric studies show that cooling rates comparable to CAPL processing result in approximately 30% conversion of austenite to epitaxial ferrite, but the reaction can be suppressed by the faster cooling rate of salt bath quenching. Measured isothermal transformation kinetics at 350 to 450sp°C shows a maximum overall rate near 400sp°C. X-ray diffraction shows that the amount of austenite retained from 400sp°C treatment peaks at 3 minutes but the carbon content increases monotonically to a saturation level. The stability of austenite in this type of steel has been quantified for the first time by direct measurement of the characteristic Msbsps{sigma} temperature. With variations in processing conditions and test temperatures, the tensile uniform ductility has been correlated with the amount and stability of retained austenite, while maintaining a constant 3% flow of 83 ksi. Consistent with previous transformations plasticity studies an optimal austenite stability is found at approximately 10 K above the Msbsps{sigma} temperature, demonstrating a maximum uniform ductility of 44% for an austenite content of 16%. Correlations indicate that desired uniform ductility levels of 20 to 25% could be achieved with only approximately 5% austenite if stability is optimized by placing Msbsps{sigma} 10 K below ambient temperature. Measured uniform ductility in plane strain tension shows similar trends with processing conditions, but models predict that stress state effects will shift the Msbsps{sigma} temperature approximately 5 K higher than that for uniaxial tension. The measured dependence of Msbsps{sigma} on austenite composition and particle size has been modeled via heterogeneous nucleation theory. The composition dependence is consistent with contributions from the transformation chemical driving force and the interfacial frictional work from solution hardening. An inverse dependence on the log of the particle volume is consistent with statistics of heterogeneous nucleation. The observed austenite carbon content at the end of bainitic transformation is consistent with paraequilibrium calculations adding a stored energy term to the bainitic ferrite. The model predicts that optimal austenite stability for maximum uniform ductility can be achieved at fixed particle size by lowering Mn and/or reducing the isothermal bainite transformation temperature.

Acoustic emission-microstructural relationships in ferritic steels. Part 2: The effect of tempering

NASA Astrophysics Data System (ADS)

Scruby, C. B.; Wadley, H. N. G.

1985-07-01

Tempering of Fe-3.25 wt%Ni alloys with carbon contents of between 0.057 and 0.49 wt% leads to a pronounced acoustic emission activity during ambient temperature tensile testing. The maximum emission occurs from samples tempered approx. 250 deg C and appears only weakly influenced by carbon content. Mechanical property determinations link the maximum to a precipitation hardening effect. A model involving the cooperative motion of dislocations over distances corresponding to the lath-packet dimension is proposed. The mechanism responsible for cooperative motion is believed to be a precipitate shearing process, the first time such a process has been proposed for quenched and tempered ferritic steels. A second, much weaker source of emission has been identified in material subjected to prolonged tempering at 625 deg C. The mechanism responsible for this emission is believed to be the sudden multiplication and propagation of dislocations during microyield events. No evidence has been found to support the view that carbide fracture in quenched and tempered steels is a direct source of acoustic emission. The microstructural states in which most quenched and tempered steels are used in practice, generate very little detectable acoustic emission either during deformation or fracture, irrespective of carbon content.

Microstructural development of cobalt ferrite ceramics and its influence on magnetic properties

NASA Astrophysics Data System (ADS)

Kim, Gi-Yeop; Jeon, Jae-Ho; Kim, Myong-Ho; Suvorov, Danilo; Choi, Si-Young

2013-11-01

The microstructural evolution and its influence on magnetic properties in cobalt ferrite were investigated. The cobalt ferrite powders were prepared via a solid-state reaction route and then sintered at 1200 °C for 1, 2, and 16 h in air. The microstructures from sintered samples represented a bimodal distribution of grain size, which is associated with abnormal grain growth behavior. And thus, with increasing sintering time, the number and size of abnormal grains accordingly increased but the matrix grains were frozen with stagnant grain growth. In the sample sintered for 16 h, all of the matrix grains were consumed and the abnormal grains consequently impinged on each other. With the appearance of abnormal grains, the magnetic coercivity significantly decreased from 586.3 Oe (1 h sintered sample) to 168.3 Oe (16 h sintered sample). This is due to the magnetization in abnormal grains being easily flipped. In order to achieve high magnetic coercivity of cobalt ferrite, it is thus imperative to fabricate the fine and homogeneous microstructure.

Welding of 316L Austenitic Stainless Steel with Activated Tungsten Inert Gas Process

NASA Astrophysics Data System (ADS)

Ahmadi, E.; Ebrahimi, A. R.

2015-02-01

The use of activating flux in TIG welding process is one of the most notable techniques which are developed recently. This technique, known as A-TIG welding, increases the penetration depth and improves the productivity of the TIG welding. In the present study, four oxide fluxes (SiO2, TiO2, Cr2O3, and CaO) were used to investigate the effect of activating flux on the depth/width ratio and mechanical property of 316L austenitic stainless steel. The effect of coating density of activating flux on the weld pool shape and oxygen content in the weld after the welding process was studied systematically. Experimental results indicated that the maximum depth/width ratio of stainless steel activated TIG weld was obtained when the coating density was 2.6, 1.3, 2, and 7.8 mg/cm2 for SiO2, TiO2, Cr2O3, and CaO, respectively. The certain range of oxygen content dissolved in the weld, led to a significant increase in the penetration capability of TIG welds. TIG welding with active fluxes can increase the delta-ferrite content and improves the mechanical strength of the welded joint.

Microstructure design of low alloy transformation-induced plasticity assisted steels

NASA Astrophysics Data System (ADS)

Zhu, Ruixian

The microstructure of low alloy Transformation Induced Plasticity (TRIP) assisted steels has been systematically varied through the combination of computational and experimental methodologies in order to enhance the mechanical performance and to fulfill the requirement of the next generation Advanced High Strength Steels (AHSS). The roles of microstructural parameters, such as phase constitutions, phase stability, and volume fractions on the strength-ductility combination have been revealed. Two model alloy compositions (i.e. Fe-1.5Mn-1.5Si-0.3C, and Fe-3Mn-1Si-0.3C in wt%, nominal composition) were studied. Multiphase microstructures including ferrite, bainite, retained austenite and martensite were obtained through conventional two step heat treatment (i.e. intercritical annealing-IA, and bainitic isothermal transformation-BIT). The effect of phase constitution on the mechanical properties was first characterized experimentally via systematically varying the volume fractions of these phases through computational thermodynamics. It was found that martensite was the main phase to deteriorate ductility, meanwhile the C/VA ratio (i.e. carbon content over the volume fraction of austenite) could be another indicator for the ductility of the multiphase microstructure. Following the microstructural characterization of the multiphase alloys, two microstructural design criteria (i.e. maximizing ferrite and austenite, suppressing athermal martensite) were proposed in order to optimize the corresponding mechanical performance. The volume fraction of ferrite was maximized during the IA with the help of computational thermodyanmics. On the other hand, it turned out theoretically that the martensite suppression could not be avoided on the low Mn contained alloy (i.e. Fe- 1.5Mn-1.5Si-0.3C). Nevertheless, the achieved combination of strength (~1300MPa true strength) and ductility (˜23% uniform elongation) on the low Mn alloy following the proposed design criteria fulfilled the requirement of the next generation AHSS. To further optimize the microstructure such that the designed criteria can be fully satisfied, further efforts have been made on two aspects: heat treatment and alloy addition. A multi-step BIT treatment was designed and successfully reduced the martensite content on the Fe-1.5Mn-1.5Si-0.3C alloy. Microstructure analysis showed a significant reduction on the volume fraction of martensite after the multi-step BIT as compared to the single BIT step. It was also found that, a slow cooling rate between the two BIT treatments resulted in a better combination of strength and ductility than rapid cooling or conventional one step BIT. Moreover, the athermal martensite formation can be fully suppressed by increasing the Mn content (Fe-3Mn-1Si-0.3C) and through carefully designed heat treatments. The athermal martensite-free alloy provided consistently better ductility than the martensite containing alloy. Finally, a microstructure based semi-empirical constitutive model has been developed to predict the monotonic tensile behavior of the multiphase TRIP assisted steels. The stress rule of mixture and isowork assumption for individual phases was presumed. Mecking-Kocks model was utilized to simulate the flow behavior of ferrite, bainitic ferrite and untransformed retained austenite. The kinetics of strain induced martensitic transformation was modeled following the Olson-Cohen method. The developed model has results in good agreements with the experimental results for both TRIP steels studied with same model parameters.

Role of Bi3+ substitution on structural, magnetic and optical properties of cobalt spinel ferrite

NASA Astrophysics Data System (ADS)

Anjum, Safia; Sehar, Fatima; Awan, M. S.; Zia, Rehana

2016-04-01

Bismuth-doped cobalt ferrite CoBi x Fe(2- x)O4 with x = 0, 0.1,0.2, 0.3, 0.4, 0.5 have been prepared using powder metallurgy route. The structural, morphological, elemental, magnetic and optical properties have been investigated using X-ray diffractometer, Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-rays, vibrating sample magnetometer and ultraviolet-visible spectrometer, respectively. X-ray diffractometer analysis confirms the formation of single-phase cubic spinel structure. As the substitution of larger ionic radii Bi3+ ions increases in cobalt ferrite which is responsible to increase the lattice parameters and decrease the crystallite size. SEM micrographs revealed the spherical shape of the particles with the nonuniform grain boundaries. The saturation magnetization decreases and bandgap energy increases as the concentration of non-magnetic Bi3+ ions increases.

The As-Quenched Microstructure and Tempering Behaviour of Rapidly Solidified Tungsten Steels.

DTIC Science & Technology

1980-06-12

probably either martensite or a mixture of martensite and 6-ferrite. In the investigations by Jama and Thursfield 16 Tuli et al 17,18 and Sare1 , higher...ferrite clooe to the foil surface, 17,18 while in the work of Tuli et al 𔄁, the 6-ferrite existed as cells surrounded by regions of austenite, M 2 C and...present work lies between the experimental 17,18 1 results of Tuli et al and that of Sare , on the scale of increasing cooling rate, and is in

Temperature and frequency characteristics of low-loss MnZn ferrite in a wide temperature range

NASA Astrophysics Data System (ADS)

Sun, Ke; Lan, Zhongwen; Yu, Zhong; Xu, Zhiyong; Jiang, Xiaona; Wang, Zihui; Liu, Zhi; Luo, Ming

2011-05-01

A low-loss Mn0.7Zn0.24Fe2.06O4 ferrite has been prepared by a solid-state reaction method. The MnZn ferrite has a high initial permeability, μi (3097), a high saturation induction, Bs (526 mT), a high Curie temperature, Tc (220 °C), and a low core loss, PL (≤ 415 kW/m3) in a wide temperature (25-120 °C) and frequency (10-100 kHz) range. As the temperature increases, an initial decrease followed by a subsequent increase of hysteresis loss, Ph, and eddy current loss, Pe is observed. Both Ph and Pe increase with increasing frequency. When f ≥ 300 kHz, a residual loss, Pr, appears. Pe increases with increasing temperature and frequency. The temperature and frequency dependence of Ph can be explained by irreversible domain wall movements, Pe by the skin effect, and Pr by domain wall resonance, respectively.

Influence of Ni-Cr substitution on the magnetic and electric properties of magnesium ferrite nanomaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Ahmad, Zahoor; Meydan, Turgut

2012-02-15

Graphical abstract: Variation of saturation magnetization (M{sub S}) and magnetocrystalline anisotropy coefficient (K{sub 1}) with Ni-Cr content for Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5). Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} are synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer High field regime of M-H loops are modeled using Law of Approach to saturation. Black-Right-Pointing-Pointer A considerable increase in the value of M{sub S} from 148 kA/m to 206 kA/m is achieved Black-Right-Pointing-Pointer {rho}{sup RT} enhanced to the order of 10{sup 9} {Omega}cm at potential operational range around 300 K. -- Abstract: The effect of variationmore » of composition on the structural, morphological, magnetic and electric properties of Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5) nanocrystallites is presented. The samples were prepared by novel polyethylene glycol (PEG) assisted microemulsion method with average crystallite size of 15-47 nm. The microstructure, chemical, and phase analyses of the samples were studied by the scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray fluorescence (ED-XRF), and X-ray diffraction (XRD). Compositional variation greatly affected the magnetic and structural properties. The high-field regimes of the magnetic loops are modelled using the Law of Approach (LOA) to saturation in order to extract information about their anisotropy and the saturation magnetization. Thermal demagnetization measurements are carried out using VSM and significant enhancement of the Curie temperature from 681 K to 832 K has been achieved by substitution of different contents of Ni-Cr. The dc-electrical resistivity ({rho}{sup RT}) at potential operational range around 300 K is increased from 7.5 Multiplication-Sign 10{sup 8} to 4.85 Multiplication-Sign 10{sup 9} {Omega}cm with the increase in Ni-Cr contents. Moreover, the results of the present study provide sufficient evidence to show that the electric and magnetic properties of Mg-ferrite have been improved significantly by substituting low contents of Ni-Cr.« less

The effect of Bi substitution on the microstructure and magnetic properties of the Sr0.4Ba0.3La0.3Fe12-xBixO19 hexagonal ferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Liu, Xiansong; Shao, Juxiang; Feng, Shuangjiu; Huang, Duohui; Li, Mingling

2017-01-01

Bi3+ ions doped M-type hexaferrites, Sr0.4Ba0.3La0.3Fe12-xBixO19 (0≤x≤0.7), were prepared by the ceramic process. The phase components of the magnetic powders were investigated by X-ray diffraction. The results show that a single magnetoplumbite phase is obtained for the magnetic powders with x from 0 to 0.2, and BiFeO3 as a second phase appears when Bi content (x)≥0.3. The micrographs of the sintered magnets were observed by a field emission scanning electron microscopy. The sintered magnets are formed of hexagonal-shaped crystals. The magnetic properties of the sintered magnets were measured at room temperature by a permanent magnetic measuring system. The remanence (Br) first increases with x from 0 to 0.2, and then decreases when Bi content (x)≥0.2. The intrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) firstly decrease quickly with x from 0 to 0.1, and then increase linearly when Bi content (x)≥0.1. The maximum energy product [(BH)max] increases with x from 0 to 0.3, and then decreases when Bi content (x)≥0.3. The ratio Hk/Hcj ratio first increases with Bi content (x) from 0 to 0.4. And the Hk/Hcj ratio decreases when x≥0.4.

Modified ferrite core-shell nanoparticles magneto-structural characterization

NASA Astrophysics Data System (ADS)

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.

Thermal expansion characteristics of Fe-9Cr-0.12C-0.56Mn-0.24V-1.38W-0.06Ta (wt.%) reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Subramanian, Raju; Tripathy, Haraprasanna; Rai, Arun Kumar; Hajra, Raj Narayan; Saibaba, Saroja; Jayakumar, Tammana; Rajendra Kumar, Ellappan

2015-04-01

The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic-martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered α-ferrite phase exhibited a smooth quadratic increase with temperature, while that of γ-austenite remained fairly linear up to 1273 K. The results suggest that α-ferrite + Carbides → γ-austenite transformation occurs upon continuous heating in the temperature range, 1146 ⩽ T ⩽ 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered α-ferrite and γ-austenite phases are estimated to be about 1.48 × 10-5 and 2.4 × 10-5 K-1 respectively. The magnetic contribution to relative thermal dilatation (Δl/l298)mag is found to be small and negative, as compared to phonon contribution.

Ultrasonic agitation-floating classification of nano-sized Ba-Mg ferrites particles formed by using self-propagating high temperature synthesis and fabrication of nickel-ferrites thin sheet by pulse-electroforming.

PubMed

Choi, Yong

2013-01-01

Nickel-nano-sized ferrites composites sheet for electromagnetic shielding was produced by pulse-electroforming in a modified nickel sulfamate solution. The ferrite particles were prepared by self-propagating high temperature synthesis (SHS) followed by mechanical milling, and classified with an ultrasonic agitation-floating unit to obtain about 100 nm in size. Average combustion temperature and combustion propagating rate during SHS reaction were 1190 K and 5.8 mm/sec at the oxygen pressure of 1.0 MPa, respectively. The nickel-ferrite composite sheet had preferred orientation which (100) pole clearly concentrated to normal direction, whereas, (110) and (111) poles tended to split to the longitudinal direction, respectively. Maximum magnetization, residual magnetization and coercive force of the nano-sized ferrites were 27.13 A x m2/kg, 6.4 A x m2/kg and 14.58 kA/m, respectively. Complex permeability of the composites decreased with an increase in frequency, and its real value (mu'r) had the maximum at about 0.3 GHz. The dielectric constants of the composites were epsilon'r = 6.7 and epsilon"r = 0.

Mechanical Performance of Ferritic Martensitic Steels for High Dose Applications in Advanced Nuclear Reactors

NASA Astrophysics Data System (ADS)

Anderoglu, Osman; Byun, Thak Sang; Toloczko, Mychailo; Maloy, Stuart A.

2013-01-01

Ferritic/martensitic (F/M) steels are considered for core applications and pressure vessels in Generation IV reactors as well as first walls and blankets for fusion reactors. There are significant scientific data on testing and industrial experience in making this class of alloys worldwide. This experience makes F/M steels an attractive candidate. In this article, tensile behavior, fracture toughness and impact property, and creep behavior of the F/M steels under neutron irradiations to high doses with a focus on high Cr content (8 to 12) are reviewed. Tensile properties are very sensitive to irradiation temperature. Increase in yield and tensile strength (hardening) is accompanied with a loss of ductility and starts at very low doses under irradiation. The degradation of mechanical properties is most pronounced at <0.3 T M ( T M is melting temperature) and up to 10 dpa (displacement per atom). Ferritic/martensitic steels exhibit a high fracture toughness after irradiation at all temperatures even below 673 K (400 °C), except when tested at room temperature after irradiations below 673 K (400 °C), which shows a significant reduction in fracture toughness. Creep studies showed that for the range of expected stresses in a reactor environment, the stress exponent is expected to be approximately one and the steady state creep rate in the absence of swelling is usually better than austenitic stainless steels both in terms of the creep rate and the temperature sensitivity of creep. In short, F/M steels show excellent promise for high dose applications in nuclear reactors.

Effects of Controlled Cooling-Induced Ferrite-Pearlite Microstructure on the Cold Forgeability of XC45 Steel

NASA Astrophysics Data System (ADS)

Hu, Chengliang; Chen, Lunqiang; Zhao, Zhen; Gong, Aijun; Shi, Weibing

2018-05-01

The combination of hot/warm and cold forging with an intermediate controlled cooling process is a promising approach to saving costs in the manufacture of automobile parts. In this work, the effects of the ferrite-pearlite microstructure, which formed after controlled cooling, on the cold forgeability of a medium-carbon steel were investigated. Different specimens for both normal and notched tensile tests were directly heated to high temperature and then cooled down at different cooling rates, producing different ferrite volume fractions, ranging from 6.69 to 40.53%, in the ferrite-pearlite microstructure. The yield strength, ultimate tensile strength, elongation rate, percentage reduction of area, and fracture strain were measured by tensile testing. The yield strength, indicating deformation resistance, and fracture strain, indicating formability, were used to evaluate the cold forgeability. As the ferrite volume fraction increased, the cold forgeability of the dual-phase ferritic-pearlitic steel improved. A quantitatively relationship between the ferrite volume fraction and the evaluation indexes of cold forgeability for XC45 steel was obtained from the test data. To validate the mathematical relationship, different tensile specimens machined from real hot-forged workpieces were tested. There was good agreement between the predicted and measured values. Our predictions from the relationship for cold forgeability had an absolute error less than 5%, which is acceptable for industrial applications and will help to guide the design of combined forging processes.

Study of the preparation of NI-Mn-Zn ferrite using spent NI-MH and alkaline Zn-Mn batteries

NASA Astrophysics Data System (ADS)

Xi, Guoxi; Xi, Yuebin; Xu, Huidao; Wang, Lu

2016-01-01

Magnetic nanoparticles of Ni-Mn-Zn ferrite have been prepared by a sol-gel method making use of spent Ni-MH and Zn-Mn batteries as source materials. Characterization by X-ray diffraction was carried out to study the particle size. The presence of functional groups was identified by Fourier transform infrared spectroscopy. From studies by thermogravimetry and differential scanning calorimetry, crystallization occurred at temperatures above 560 °C. The magnetic properties of the final products were found to be directly influenced by the average particle size of the product. The Ms values increase and the Hc values decrease as the size of the Ni-Mn-Zn ferrite particles increases.

The nature of temper brittleness of high-chromium ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarrak, V.I.; Suvorova, S.O.; Golovin, I.S.

The reasons for development of {open_quotes}475{degrees}C brittleness{close_quotes} of high-chromium ferritic steels are considered from the standpoint of fracture mechanics. It is shown that the general rise in the curve of temperature-dependent local flow stress has the decisive influence on the position of the ductile-to-brittle transformation temperature and the increase in it as the result of a hold at temperatures of development of brittleness. The established effect is related to the change in the parameters determining dislocation mobility, that is, the activation energy of dislocation movement in high-chromium ferrite and the resistance to microplastic deformation, both caused by processes of separationmore » into layers of high-chromium ferrite and decomposition of the interstitial solid solution.« less

Structure formation in grade 20 steel during equal-channel angular pressing and subsequent heating

NASA Astrophysics Data System (ADS)

Dobatkin, S. V.; Odesskii, P. D.; Raab, G. I.; Tyutin, M. R.; Rybalchenko, O. V.

2016-11-01

The structure formation and the mechanical properties of quenched and tempered grade 20 steel after equal-channel angular pressing (ECAP) at various true strains and 400°C are studied. Electron microscopy analysis after ECAP shows a partially submicrocrystalline and partially subgrain structure with a structural element size of 340-375 nm. The structural element size depends on the region in which the elements are formed (polyhedral ferrite, needle-shaped ferrite, tempered martensite, and pearlite). Heating of the steel after ECAP at 400 and 450°C increases the fraction of high-angle boundaries and the structural ferrite element size to 360-450 nm. The fragmentation and spheroidization of cementite lamellae of pearlite and subgrain coalescence in the regions of needle-shaped ferrite and tempered martensite take place at a high ECAP true strain and heating temperature. Structural refinement ensures considerable strengthening, namely, UTS 742-871 MPa at EL 11-15.3%. The strength slightly increases, whereas the plasticity slightly decreases when the true strain increases during ECAP. After ECAP and heating, the strength and plastic properties of the grade 20 steel remain almost the same.

Characterization of Austempered Ferritic Ductile Iron

NASA Astrophysics Data System (ADS)

Dakre, Vinayak S.; Peshwe, D. R.; Pathak, S. U.; Likhite, A. A.

2018-04-01

The ductile iron (DI) has graphite nodules enclose in ferrite envelop in pearlitic matrix. The pearlitic matrix in DI was converted to ferritic matrix through heat treatment. This heat treatment includes austenitization of DI at 900°C for 1h, followed by furnace cooling to 750°C & hold for 1h, then again furnace cooling to 690°C hold for 2h, then samples were allowed to cool in furnace. The new heat treated DI has graphite nodules in ferritic matrix and called as ferritic ductile iron (FDI). Both DIs were austenitized at 900°C for 1h and then quenched into salt bath at 325°C. The samples were soaked in salt bath for 60, 120, 180, 240 and 300 min followed by air cooling. The austempered samples were characterized with help of optical microscopy, SEM and X-ray diffraction analysis. Austempering of ferritic ductile iron resulted in finer ausferrite matrix as compared to ADI. Area fraction of graphite, ferrite and austenite were determining using AXIOVISION-SE64 software. Area fraction of graphite was more in FDI than that of as cast DI. The area fraction of graphite remains unaffected due to austempering heat treatment. Ausferritic matrix coarsened (feathered) with increasing in austempering time for both DI and FDI. Bulk hardness test was carried on Rockwell Hardness Tester with load of 150 kgf and diamond indenter. Hardness obtained in as cast DI is 28 HRC which decreased to 6 HRC in FDI due conversion of pearlitic matrix to ferritic matrix. Hardness is improved by austempering process.

Inductively heated shape memory polymer for the magnetic actuation of medical devices.

PubMed

Buckley, Patrick R; McKinley, Gareth H; Wilson, Thomas S; Small, Ward; Benett, William J; Bearinger, Jane P; McElfresh, Michael W; Maitland, Duncan J

2006-10-01

Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.

Formation of nickel and copper ferrites in ceramics: a potential reaction in the reuse of iron-rich sludge incineration ash.

PubMed

Shih, Kaimin

2012-12-01

This study investigates potential solid-state reactions for the stabilization of hazardous metals when reusing the incineration ash from chemically enhanced primary treatment (CEPT) sludge to fabricate ceramic products. Nickel and copper were used as examples of hazardous metals, and the iron content in the reaction system was found to play a major role in incorporating these hazardous metals into their ferrite phases (NiFe2O4 and CuFe2O4). The results from three-hour sintering experiments on NiO + Fe2O3 and CuO + Fe2O3 systems clearly demonstrate the potential for initiating metal incorporation mechanisms using an iron-containing precursor at attainable ceramic sintering temperatures (above 750 degrees C). Both ferrite phases were examined using a prolonged leaching experiment modified from the widely used toxicity characteristic leaching procedure (TCLP) to evaluate their long-term metal leachability. The leaching results indicate that both the NiFe2O4 and the CuFe2O4 products were significantly superior to their oxide forms in immobilizing hazardous metals.

Simulation Kinetics of Austenitic Phase Transformation in Ti+Nb Stabilized IF and Microalloyed Steels

NASA Astrophysics Data System (ADS)

Ghosh, Sumit; Dasharath, S. M.; Mula, Suhrit

2018-05-01

In the present study, the influence of cooling rates (low to ultrafast) on diffusion controlled and displacive transformation of Ti-Nb IF and microalloyed steels has been thoroughly investigated. Mechanisms of nucleation and formation of non-equiaxed ferrite morphologies (i.e., acicular ferrite and bainitic ferrite) have been analyzed in details. The continuous cooling transformation behavior has been studied in a thermomechanical simulator (Gleeble 3800) using the cooling rates of 1-150 °C/s. On the basis of the dilatometric analysis of each cooling rate, continuous cooling transformation (CCT) diagrams have been constructed for both the steels to correlate the microstructural features at each cooling rate in different critical zones. In the case of the IF steel, massive ferrite grains along with granular bainite structures have been developed at cooling rates > 120 °C/s. On the other hand, a mixture of lath bainitic and lath martensite structures has been formed at a cooling rate of 80 °C/s in the microalloyed steel. A strong dependence of the cooling rates and C content on the microstructures and mechanical properties has been established. The steel samples that were fast cooled to a mixture of bainite ferrite and martensite showed a significant improvement of impact toughness and hardness (157 J, for IF steel and 174 J for microalloyed steel) as compared to that of the as-received specimens (133 J for IF steel and 116 J for microalloyed steel). Thus, it can be concluded that the hardness and impact toughness properties are correlated well with the microstructural constituents as indicated by the CCT diagram. Transformation mechanisms and kinetics of austenitic transformation to different phase morphologies at various cooling rates have been discussed in details to correlate microstructural evolution and mechanical properties.

Simulation Kinetics of Austenitic Phase Transformation in Ti+Nb Stabilized IF and Microalloyed Steels

NASA Astrophysics Data System (ADS)

Ghosh, Sumit; Dasharath, S. M.; Mula, Suhrit

2018-04-01

In the present study, the influence of cooling rates (low to ultrafast) on diffusion controlled and displacive transformation of Ti-Nb IF and microalloyed steels has been thoroughly investigated. Mechanisms of nucleation and formation of non-equiaxed ferrite morphologies (i.e., acicular ferrite and bainitic ferrite) have been analyzed in details. The continuous cooling transformation behavior has been studied in a thermomechanical simulator (Gleeble 3800) using the cooling rates of 1-150 °C/s. On the basis of the dilatometric analysis of each cooling rate, continuous cooling transformation (CCT) diagrams have been constructed for both the steels to correlate the microstructural features at each cooling rate in different critical zones. In the case of the IF steel, massive ferrite grains along with granular bainite structures have been developed at cooling rates > 120 °C/s. On the other hand, a mixture of lath bainitic and lath martensite structures has been formed at a cooling rate of 80 °C/s in the microalloyed steel. A strong dependence of the cooling rates and C content on the microstructures and mechanical properties has been established. The steel samples that were fast cooled to a mixture of bainite ferrite and martensite showed a significant improvement of impact toughness and hardness (157 J, for IF steel and 174 J for microalloyed steel) as compared to that of the as-received specimens (133 J for IF steel and 116 J for microalloyed steel). Thus, it can be concluded that the hardness and impact toughness properties are correlated well with the microstructural constituents as indicated by the CCT diagram. Transformation mechanisms and kinetics of austenitic transformation to different phase morphologies at various cooling rates have been discussed in details to correlate microstructural evolution and mechanical properties.

Strontium hexaferrite (SrFe12O19) based composites for hyperthermia applications

NASA Astrophysics Data System (ADS)

Rashid, Amin Ur; Southern, Paul; Darr, Jawwad A.; Awan, Saifullah; Manzoor, Sadia

2013-10-01

Mixed phase composites of SrFe12O19/MgFe2O4/ZrO2 were prepared via the citrate gel technique as potential candidate materials for magnetic hyperthermia. Structural and magnetic properties of the samples were studied using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and a vibrating sample magnetometer. XRD and FE-SEM data confirm that magnesium ferrite and zirconium oxide phases increased with increasing Mg and Zr content in the precursors. Magnetization loops for the composites were measured at room temperature and showed significant variation of saturation magnetization, coercivity and remanence depending on the amount of the highly anisotropic Sr-hexaferrite phase. The sample with the highest Mg and Zr content had the lowest coercivity (80 Oe) and saturation magnetization (41 emu/g). The composite samples each were exposed to a 214 kHz alternating magnetic field of amplitude 22 Oe and a significant heating effect was observed in selected samples, which suggests potential for use in magnetic hyperthermia.

Oxygen nonstoichiometry and thermodynamic quantities in solid solution SrFe1-xSnxO3-δ

NASA Astrophysics Data System (ADS)

Merkulov, O. V.; Markov, A. A.; Leonidov, I. A.; Patrakeev, M. V.; Kozhevnikov, V. L.

2018-06-01

The oxygen content (3-δ) variations in tin substituted derivatives SrFe1-xSnxO3-δ, where x = 0.05, 0.1, 0.17 and 0.25, of perovskite-like strontium ferrite, have been studied by coulometric titration measurements within oxygen partial pressure (pO2) range 10-19-10-2 atm at 800-950 °С. The obtained dependencies of (3-δ) from pO2 and temperature are used for calculations of partial molar thermodynamic functions of oxygen in the oxide structure. It is found that a satisfactory explanation of the experimental results can be attained within frameworks of the ideal solution model with ion and electron defects appearing in the result of oxidation and disproportionation of iron cations. The increase of the oxidation reaction enthalpy with tin content is consistent with the increase of the unit cell parameter, i.e., the stretch and relaxation of Fe-O chemical bonds.

Effect of Auxiliary Preheating of the Filler Wire on Quality of Gas Metal Arc Stainless Steel Claddings

NASA Astrophysics Data System (ADS)

Shahi, Amandeep S.; Pandey, Sunil

2008-02-01

Weld cladding is a process for producing surfaces with good corrosion resistant properties by means of depositing/laying of stainless steels on low-carbon steel components with an objective of achieving maximum economy and enhanced life. The aim of the work presented here was to investigate the effect of auxiliary preheating of the solid filler wire in mechanized gas metal arc welding (GMAW) process (by using a specially designed torch to preheat the filler wire independently, before its emergence from the torch) on the quality of the as-welded single layer stainless steel overlays. External preheating of the filler wire resulted in greater contribution of arc energy by resistive heating due to which significant drop in the main welding current values and hence low dilution levels were observed. Metallurgical aspects of the as welded overlays such as chemistry, ferrite content, and modes of solidification were studied to evaluate their suitability for service and it was found that claddings obtained through the preheating arrangement, besides higher ferrite content, possessed higher content of chromium, nickel, and molybdenum and lower content of carbon as compared to conventional GMAW claddings, thereby giving overlays with superior mechanical and corrosion resistance properties. The findings of this study not only establish the technical superiority of the new process, but also, owing to its productivity-enhanced features, justify its use for low-cost surfacing applications.

High yttria ferritic ODS steels through powder forging

NASA Astrophysics Data System (ADS)

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.

Effect of solution annealing temperature on precipitation in 2205 duplex stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwar, A., E-mail: akashiwar@gmail.com; Vennela, N. Phani, E-mail: phanivennela@gmail.com; Kamath, S.L., E-mail: kamath@iitb.ac.in

2012-12-15

In the present study, effect of solution annealing temperature (1050 Degree-Sign C and 1100 Degree-Sign C) and isothermal ageing (700 Degree-Sign C: 15 min to 6 h) on the microstructural changes in 2205 duplex stainless steel has been investigated systematically. Scanning electron microscopy and X-ray diffraction were adopted to follow the microstructural evolution, while an energy dispersive spectrometer attached to scanning electron microscope was used to obtain localised chemical information of various phases. The ferritic matrix of the two phase 2205 duplex stainless steel ({approx} 45% ferrite and {approx} 55% austenite) undergoes a series of metallurgical transformations during ageing-formation ofmore » secondary austenite ({gamma}{sub 2}) and precipitation of Cr and Mo rich intermetallic (chi-{chi} and sigma-{sigma}) phases. For solution annealing at 1050 Degree-Sign C, significant amount of carbides were observed in the ferrite grains after 1 h of ageing at 700 Degree-Sign C. {chi} Phase precipitated after the precipitation of carbides-preferentially at the ferrite-ferrite and also at the ferrite-austenite boundaries. {sigma} Phase was not observed in significant quantity even after 6 h of ageing. The sequence of precipitation in samples solution annealed at 1050 Degree-Sign C was found to be carbides {yields} {chi} {yields} {sigma}. On the contrary, for samples solution annealed at 1100 Degree-Sign C, the precipitation of {chi} phase was negligible. {chi} Phase precipitated before {sigma} phase, preferentially along the ferrite-ferrite grain boundaries and was later consumed in the {sigma} phase precipitation. The {sigma} phase precipitated via the eutectoid transformation of ferrite to yield secondary austenite {gamma}{sub 2} and {sigma} phase in the ferrite and along the ferrite-austenite grain boundaries. An increase in the volume fraction of {gamma}{sub 2} and {sigma} phase with simultaneous decrease in the ferrite was evidenced with ageing. - Highlights: Black-Right-Pointing-Pointer Effect of solution annealing temperature on microstructural evolution is studied. Black-Right-Pointing-Pointer {chi} Phase precipitated preferentially in the samples solution annealed at 1050 Degree-Sign C. Black-Right-Pointing-Pointer {sigma} Phase precipitated preferentially in the samples solution annealed at 1100 Degree-Sign C. Black-Right-Pointing-Pointer For SA at 1050 Degree-Sign C, the sequence of precipitation was carbides {yields} {chi} phase {yields} {sigma} phase. Black-Right-Pointing-Pointer For SA at 1100 Degree-Sign C, {sigma} phase precipitated via the eutectoid reaction: ferrite (F) {yields} {sigma} + {gamma}{sub 2}.« less

High Strength-High Ductility Combination Ultrafine-Grained Dual-Phase Steels Through Introduction of High Degree of Strain at Room Temperature Followed by Ultrarapid Heating During Continuous Annealing of a Nb-Microalloyed Steel

NASA Astrophysics Data System (ADS)

Deng, Yonggang; Di, Hongshuang; Hu, Meiyuan; Zhang, Jiecen; Misra, R. D. K.

2017-07-01

Ultrafine-grained dual-phase (UFG-DP) steel consisting of ferrite (1.2 μm) and martensite (1 μm) was uniquely processed via combination of hot rolling, cold rolling and continuous annealing of a low-carbon Nb-microalloyed steel. Room temperature tensile properties were evaluated and fracture mechanisms studied and compared to the coarse-grained (CG) counterpart. In contrast to the CG-DP steel, UFG-DP had 12.7% higher ultimate tensile strength and 10.7% greater uniform elongation. This is partly attributed to the increase in the initial strain-hardening rate, decrease in nanohardness ratio of martensite and ferrite. Moreover, a decreasing number of ferrite grains with {001} orientation increased the cleavage fracture stress and increased the crack initiation threshold stress with consequent improvement in ductility UFG-DP steel.

Water-vapor effects on friction of magnetic tape in contact with nickel-zinc ferrite

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1984-01-01

The effects of humidity of moist nitrogen on the friction and deformation behavior of magnetic tape in contact with a nickel-zinc ferrite spherical pin were studied. The results indicate that the coefficient of friction is markedly dependent on the ambient relative humidity. Although the coefficient of friction remains low below 40-percent relative humidity, it increases rapidly with increasing relative humidity above 40 percent. The general ambient environment of the tape does not have any effect on the friction behavior if the area where the tape is in sliding contact with the ferrite pin is flooded with controlled nitrogen. The response time for the friction of the tape to humidity changes is about 10 sec. The effect of friction as a function of relative humidity on dehumidifying is very similar to that on humidifying. A surface softening of the tape due to water vapor increases the friction of the tape.

Lanthanum ion substituted cobalt ferrite nanoparticles and their hyperthermia efficiency

NASA Astrophysics Data System (ADS)

Demirci, Ç. E.; Manna, P. K.; Wroczynskyj, Y.; Aktürk, S.; van Lierop, J.

2018-07-01

We investigated the structural, compositional, and magnetic properties as well as the AC magnetic hyperthermic response of CoFe2-xLaxO4 (x = 0.0, 0.2, 0.5) nanoparticles. We found that the La3+ ions substituted into the Fe3+ ion sites, and resulted in an increased magnetocrystalline anisotropy with x, and altered the time-dependent magnetism. To provide a better understanding of the AC magnetic hyperthermia response, a series of temperature versus time measurements were done by varying the magnetic field amplitude, the carrier medium viscosity and the concentration of the nanoparticles as parameters that governed the heating efficiency. A decrease of specific loss power was observed with an increase of the viscosity of the carrier medium for x = 0 and x = 0.25 substituted Co-ferrite nanoparticles, while a small increase was observed with the x = 0.1 La3+ substituted Co-ferrite nanoparticles (due to their higher intrinsic magnetocrystalline anisotropy).

Perpendicular Biased Ferrite Tuned Cavities for the Fermilab Booster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romanov, Gennady; Awida, Mohamed; Khabiboulline, Timergali

2014-07-01

The aging Fermilab Booster RF system needs an upgrade to support future experimental program. The important feature of the upgrade is substantial enhancement of the requirements for the accelerating cavities. The new requirements include enlargement of the cavity beam pipe aperture, increase of the cavity voltage and increase in the repetition rate. The modification of the present traditional parallel biased ferrite cavities is rather challenging. An alternative to rebuilding the present Fermilab Booster RF cavities is to design and construct new perpendicular biased RF cavities, which potentially offer a number of advantages. An evaluation and a preliminary design of themore » perpendicular biased ferrite tuned cavities for the Fermilab Booster upgrade is described in the paper. Also it is desirable for better Booster performance to improve the capture of beam in the Booster during injection and at the start of the ramp. One possible way to do that is to flatten the bucket by introducing second harmonic cavities into the Booster. This paper also looks into the option of using perpendicularly biased ferrite tuners for the second harmonic cavities.« less

K-Band Latching Switches

NASA Technical Reports Server (NTRS)

Piotrowski, W. S.; Raue, J. E.

1984-01-01

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4 nanoparticles synthesized by honey mediated sol-gel combustion method

NASA Astrophysics Data System (ADS)

Singh Yadav, Raghvendra; Kuřitka, Ivo; Vilcakova, Jarmila; Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Tkacz, Jakub; Švec, Jiří; Enev, Vojtěch; Hajdúchová, Miroslava

2017-12-01

In this work CoFe2O4 spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g-1 at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g-1 at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1-107 Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4 spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory devices and for microwave applications.

Comparison Between Different Processing Schedules for the Development of Ultrafine-Grained Dual-Phase Steel

NASA Astrophysics Data System (ADS)

Karmakar, Anish; Sivaprasad, S.; Nath, S. K.; Misra, R. D. K.; Chakrabarti, Debalay

2014-05-01

A comparative study was carried out on the development of ultrafine-grained dual-phase (DP) (ferrite-martensite) structures in a low-carbon microalloyed steel processed using two thermomechanical processing routes, (i) intercritical deformation and (ii) warm-deformation and intercritical annealing. The samples were deformed using Gleeble3500® simulator, maintaining a constant total strain ( ɛ = 1) and strain rate ( = 1/s). Evolution of microstructure and micro-texture was investigated by SEM, TEM, and EBSD. Ultrafine-grained DP structures could be formed by careful selection of deformation temperature, T def (for intercritical deformation) or annealing temperature, T anneal (for warm-deformation and annealing). Overall, the ferrite grain sizes ranged from 1.5 to 4.0 μm, and the sizes and fractions of the uniformly distributed fine-martensitic islands ranged from 1.5 to 3.0 μm and 15 to 45 pct, respectively. Dynamic strain-induced austenite-to-ferrite transformation followed by continuous (dynamic) recrystallization of the ferrite dictated the grain refinement during intercritical deformation, while, continuous (static) recrystallization by pronounced recovery dictated the grain refinement during the warm-deformation and the annealing. Regarding intercritical deformation, the samples cooled to T def indicated finer grain size compared with the samples heated to T def, which are explained in terms of the effects of strain partitioning on the ferrite and the heating during deformation. Alpha-fiber components dominated the texture in all the samples, and the fraction of high-angle boundaries (with >15 deg misorientation) increased with the increasing T def or T anneal, depending on the processing schedule. Fine carbide particles, microalloyed precipitates and austenitic islands played important roles in defining the mechanism of grain refinement that involved retarding conventional ferrite recrystallization and ferrite grain growth. With regard to the intercritical deformation, warm-deformation followed by annealing is a simpler process to control in the rolling mill; however, the need for high-power rolling mill and controlled annealing facility imposes industrial challenges.

Kinetics and mechanism of nickel ferrite formation under high temperature ultrasonic treatment.

PubMed

Baranchikov, Alexander Ye; Ivanov, Vladimir K; Tretyakov, Yuri D

2007-02-01

The effect of simultaneous ultrasonic and thermal treatment on kinetics and mechanism of nickel ferrite formation was studied. It was established that sonication leads to notable increase of the mean rate of this reaction and decrease of effective activation energy from 190+/-5 to 125+/-7 kJ/mol. XRD data show that ultrasonic treatment significantly affects the microstructure of both initial reagent (Fe(2)O(3)) and reaction product (NiFe(2)O(4)) thus promoting formation of well developed reaction zone. A general model of ferrite formation mechanism under high temperature ultrasonic treatment was proposed.

Microstructure, magnetic and microwave absorptive behavior of doped W-type hexaferrite nanoparticles prepared by co-precipitation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gordani, Gholam Reza, E-mail: gordani@gmail.com; Mohseni, Marzieh; Ghasemi, Ali

2016-04-15

Highlights: • High frequency properties of substituted W-type Sr-hexaferrite. • Saturation magnetization of samples is decreased with increasing of dopants content. • The ferrite sample covers about 6 GHz of bandwidth in K{sub u} band. • The optimum substituted samples can be used as a potential magnetic loss material. • Sample contain x = 0.4 of dopants have shown greater than 90% of reflection loss. - Abstract: Substituted W-type hexaferrite nanoparticles of SrZn{sub 2−x}Co{sub x/2}Ni{sub x/2}Fe{sub 16}O{sub 27} were synthesized by a chemical co-precipitation method. The X-ray diffraction results confirmed that W-type ferrite was identified as the main phase inmore » whole samples in the range of x = 0–0.4. According to magnetic hysteresis loops, with increasing of substituted cations, saturation of magnetization increased and coercivity decreased due to crystalline site occupation of Zn with Ni and Co cations. The microwave reflection loss analysis results in the K{sub u} band (12–18 GHz) show that the highest value of reflection loss of samples was −29.11 dB at frequency of 14.57 GHz with an absorption bandwidth of more than 6 GHz by choosing reflection loss value of −10 dB as a reference. The results indicate that, the sample with appropriate amount of substituted cations hold great promise for microwave device applications.« less

Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

NASA Astrophysics Data System (ADS)

Lu, Z.; Faulkner, R. G.; Morgan, T. S.

2008-12-01

High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 × 10 -6 dpa/s) at 400 °C and 28 dpa (1.7 × 10 -6 dpa/s) at 465 °C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided (˜15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

A facile microwave synthetic route for ferrite nanoparticles with direct impact in magnetic particle hyperthermia.

PubMed

Makridis, A; Chatzitheodorou, I; Topouridou, K; Yavropoulou, M P; Angelakeris, M; Dendrinou-Samara, C

2016-06-01

The application of ferrite magnetic nanoparticles (MNPs) in medicine finds its rapidly developing emphasis on heating mediators for magnetic hyperthermia, the ever-promising "fourth leg" of cancer treatment. Usage of MNPs depends largely on the preparation processes to select optimal conditions and effective routes to finely tailor MNPs. Microwave heating, instead of conventional heating offers nanocrystals at significantly enhanced rate and yield. In this work, a facile mass-production microwave hydrothermal synthetic approach was used to synthesize stable ferromagnetic manganese and cobalt ferrite nanoparticles with sizes smaller than 14 nm from metal acetylacetonates in the presence of octadecylamine. Prolonging the reaction time from 15 to 60 min, led to ferrites with improved crystallinity while the sizes are slight increased. The high crystallinity magnetic nanoparticles showed exceptional magnetic heating parameters. In vitro application was performed using the human osteosarcoma cell line Saos-2 incubated with manganese ferrite nanoparticles. Hyperthermia applied in a two cycle process, while AC magnetic field remained on until the upper limit of 45 °C was achieved. The comparative results of the AC hyperthermia efficiency of ferrite nanoparticles in combination with the in vitro study coincide with the magnetic features and their tunability may be further exploited for AC magnetic hyperthermia driven applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Combined effect of demagnetizing field and induced magnetic anisotropy on the magnetic properties of manganese-zinc ferrite composites

NASA Astrophysics Data System (ADS)

Babayan, V.; Kazantseva, N. E.; Moučka, R.; Sapurina, I.; Spivak, Yu. M.; Moshnikov, V. A.

2012-01-01

This work is devoted to the analysis of factors responsible for the high-frequency shift of the complex permeability (μ*) dispersion region in polymer composites of manganese-zinc (MnZn) ferrite, as well as to the increase in their thermomagnetic stability. The magnetic spectra of the ferrite and its composites with polyurethane (MnZn-PU) and polyaniline (MnZn-PANI) are measured in the frequency range from 1 MHz to 3 GHz in a longitudinal magnetization field of up to 700 Ое and in the temperature interval from -20 °С to +150 °С. The approximation of the magnetic spectra by a model, which takes into account the role of domain wall motion and magnetization rotation, allows one to determine the specific contribution of resonance processes associated with domain wall motion and the natural ferromagnetic resonance to the μ*. It is established that, at high frequencies, the μ* of the MnZn ferrite is determined solely by magnetization rotation, which occurs in the region of natural ferromagnetic resonance when the ferrite is in the “single domain” state. In the polymer composites of the MnZn ferrite, the high-frequency permeability is also determined mainly by the magnetization rotation; however, up to high values of magnetizing fields, there is a contribution of domain wall motion, thus the “single domain” state in ferrite is not reached. The frequency and temperature dependence of μ* in polymer composites are governed by demagnetizing field and the induced magnetic anisotropy. The contribution of the induced magnetic anisotropy is crucial for MnZn-PANI. It is attributed to the elastic stresses that arise due to the domain wall pinning by a polyaniline film adsorbed on the surface of the ferrite during in-situ polymerization.

Microwave combustion synthesis of Co1-xZnxFe2O4 (0⩽x⩽0.5): Structural, magnetic, optical and vibrational spectroscopic studies.

PubMed

Sundararajan, M; Kennedy, L John; Vijaya, J Judith; Aruldoss, Udaya

2015-04-05

Nanostructured pure and zinc doped cobalt ferrites (Co1-xZnxFe2O4 where x fraction ranging from 0 to 0.5) were prepared by microwave combustion method employing urea as a fuel. The nanostructured samples were characterized by using various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy, energy dispersive X-ray analysis, UV-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and Fourier transformed infrared (FT-IR) spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis and the FT-IR spectroscopy revealed the formation of cobalt ferrite cubic spinel-type structure. The average crystallite sizes for the samples were in the range of 3.07-11.30 nm. The direct band gap (Eg) was estimated using Kubelka-Munk method and is obtained from the UV-vis spectra. The band gap value decreased with an increase in zinc fraction (2.56-2.17 eV). The violet and green emission observed in the photoluminescence spectra revealed that cobalt ferrites are governed by defect controlled processes. The elemental analysis of zinc doped cobalt ferrites were obtained from energy dispersive X-ray (EDX) analysis. From the magnetic measurements, it is observed that cobalt ferrite and zinc doped cobalt ferrite systems fall under the soft ferrite category. The saturation magnetization (Ms) value of undoped cobalt ferrite is 14.26 emu/g, and it has reached a maximum of 29.61 emu/g for Co0.7Zn0.3Fe2O4. Copyright © 2014 Elsevier B.V. All rights reserved.

Control of Microstructures and the Practical Properties of API X80 Grade Heavy-Wall High-Frequency Electric Resistance-Welded Pipe with Excellent Low-Temperature Toughness

NASA Astrophysics Data System (ADS)

Goto, Sota; Nakata, Hiroshi; Toyoda, Shunsuke; Okabe, Takatoshi; Inoue, Tomohiro

2017-10-01

This paper describes development of heavy-walled API X80 grade high-frequency electric resistance-welded (HFW) line pipes and conductor-casing pipes with wall thicknesses up to 20.6 mm. A fine bainitic-ferrite microstructure, which is preferable for low-temperature toughness, was obtained by optimizing the carbon content and applying the thermomechanical controlled hot-rolling process. As a result, the Charpy ductile-brittle transition temperature (DBTT) was well below 227 K (-46 °C) in the base metal of the HFW line pipe. When the controlled hot-rolling ratio (CR) was increased from 23 to 48 pct, the area average grain size decreased from 15 to 8 μm. The dependence of CTOD properties on CR was caused by the largest grain which is represented by the area average grain size. No texture development due to the increase of CR from 23 to 48 pct was observed. In addition, because controlled in-line heat treatment of the longitudinal weld seam also produced the fine bainitic-ferrite microstructure at the weld seam, DBTT was lower than 227 K (-46 °C) at the weld portion. The developed pipes showed good girth weldability without preheat treatment, and fracture in the tensile test initiated from the base metal in all cases.

Microstructure, Hardness, and Corrosion Behavior of TiC-Duplex Stainless Steel Composites Fabricated by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Han, Ying; Zhang, Wei; Sun, Shicheng; Chen, Hua; Ran, Xu

2017-08-01

Duplex stainless steel composites with various weight fractions of TiC particles are prepared by spark plasma sintering. Ferritic 434L and austenitic 316L stainless steel powders are premixed in a 50:50 weight ratio and added with 3-9 wt.% TiC. The compacts are sintered in the solid state under vacuum conditions at 1223 K for 5 min. The effects of TiC content on the microstructure, hardness, and corrosion resistance of duplex stainless steel composites fabricated by powder metallurgy are evaluated. The results indicate that the TiC particulates as reinforcements can be distributed homogeneously in the steel matrix. Densification of sintered composites decreases with increasing TiC content. M23C6 carbide precipitates along grain boundary, and its neighboring Cr-Mo-depleted region is formed in the sintered microstructure, which can be eliminated subsequently with appropriate heat treatment. With the addition of TiC, the hardness of duplex stainless steel fabricated by powder metallurgy can be markedly enhanced despite increased porosity in the composites. However, TiC particles increase the corrosion rate and degrade the passivation capability, particularly for the composite with TiC content higher than 6 wt.%. Weakened metallurgical bonding in the composite with high TiC content provides the preferred sites for pitting nucleation and/or dissolution.

Implantable ferrite antenna for biomedical applications

NASA Astrophysics Data System (ADS)

Fazeli, Maxwell L.

We have developed an implantable microstrip patch antenna with dimensions of 10x10x1.28 mm, operating around the Industrial, Scientific and Medical (ISM) band (2.4-2.5 GHz). The antenna is characterized in skin-mimicking gels and compared with simulation results. The experimental measurements are in good agreement with simulations, having a -16 dB reflection coefficient and -18 dBi realized gain at resonance, with a 185 MHz -10 dB bandwidth. The simulated effects of ferrite film loading on antenna performance are investigated, with comparisons made for 5 and 10 microm thick films, as well as for 10 microm thick films with varying magnetic loss (tan delta micro = 0.05, 0.1 and 0.3). Our simulations reveal that the addition of 10 microm thick magnetic layers has effectively lowered the resonant frequency by 70 MHz, while improving return loss and -10 dB bandwidth by 3 dB and 40 MHz, respectively, over the uncoated antenna. Ferrite film coating also improved realized gain within the ISM band, with largest gain increases at resonance found for films having lower magnetic loss. Additionally, the gain (G) variance at ISM band limits, Delta Gf(2.5GHz)-f (2.4GHz), decreased from 1.97 to 0.44 dBi for the antenna with 10 microm films over the non-ferrite antenna. The measured dip-coated NiCo ferrite films effectively reduces the antenna resonance by 110 MHz, with a 4.2 dB reflection coefficient improvement as compared to an antenna without ferrite. The measured ferrite antenna also reveals a 6 dBi and 35 MHz improvement in realized gain and -10 dB bandwidth, respectively, at resonance. Additionally, the ferrite-coated antenna shows improved directivity, with wave propagation attenuated at the direction facing the body internal. These results indicate that implantable antenna miniaturization and reliable wireless communication in the operating frequency band can be realized with ferrite loading.

The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

NASA Astrophysics Data System (ADS)

Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

2016-04-01

Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

Effect of W and N on mechanical properties of reduced activation ferritic/martensitic EUROFER-based steel grades

NASA Astrophysics Data System (ADS)

Puype, A.; Malerba, L.; De Wispelaere, N.; Petrov, R.; Sietsma, J.

2018-04-01

The C, N, and W content in EUROFER97, a 9CrWVTa reduced-activation ferritic/martensitic (RAFM) steel, was varied to obtain an experimental assessment of the main effects of the compositional variation on the mechanical properties and microstructural characteristics of six different experimental grades. Light optical microscopy (LOM) and electron back-scattered diffraction (EBSD) revealed in almost all cases a fine tempered lath martensite structure. Analyses of transmission electron micrographs, together with inductively coupled plasma mass spectrometry (ICPMS) and energy-dispersive x-ray spectroscopy (EDS) data, shows the precipitation state and spatial distribution of MxCy (M = Cr, W and Fe) and MX (M = V and/or Ta, X = C or N) carbonitrides within the matrix. The mechanical characterization of the six different steel grades was carried out by means of A50 tensile testing and Charpy tests on standard specimens (55 × 10 × 10 mm3). Lowering the carbon content and keeping the nitrogen content higher than 0.02 wt%, leads to a reduction of the ductile-to-brittle-transition-temperature (DBTT) in comparison with EUROFER97-2. The addition of tungsten further reduces the DBTT to - 94 °C, while maintaining good tensile strength and elongation.

Characterization of corrosion phenomena and kinetics on T91 ferritic/martensitic steel exposed at 450 and 550 °C to flowing Pb-Bi eutectic with 10-7 mass% dissolved oxygen

NASA Astrophysics Data System (ADS)

Tsisar, Valentyn; Schroer, Carsten; Wedemeyer, Olaf; Skrypnik, Aleksandr; Konys, Jürgen

2017-10-01

Corrosion behavior of two heats of T91 ferritic/martensitic steel, with slightly different Cr content, was investigated in flowing (2 m/s) Pb-Bi with 10-7 mass%O at 450 and 550 °C. The observed corrosion modes are: protective scale formation; accelerated oxidation and solution-based corrosion attack. Accelerated oxidation at 450 °C results in general metal recession of about 10 μm after ∼9000 h exposure and ∼15 μm at 550 °C after 2000 h. More severe and local solution-based corrosion results in a maximum depth of attack of 50-960 μm and 115-190 μm, correspondingly. Incubation period for solution-based corrosion is 500-5000 h at 450 °C and ≤500 h at 550 °C. The slightly higher chromium content in one of the heat of T91 steel prolongs the incubation period by improving the stability of the Cr-based oxide film.

Microstructure and microwave magnetic properties of Low-Firing Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrite

NASA Astrophysics Data System (ADS)

Xie, Fei; Jia, Lijun; Shen, Qihang; Qiu, Hua; Zhang, Huaiwu

2018-03-01

Low firing temperature and excellent gyromagnetic properties such as high remanence square ratio and narrow ferromagnetic resonance line width are required for the application in nonreciprocal microwave ferrite devices based on low temperature cofired ceramics (LTCC) technology. In this research, Bi2O3-Li2CO3 mixture was introduced as the sintering agent to lower the sintering temperature of Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrite. The influence of Bi2O3-Li2CO3 mixture upon the phase composition, composite microstructures and gyromagnetic properties of LiZnTiMn ferrite sintered at low temperature has been investigated for LTCC integration applications. With a proper amount of Bi2O3-Li2CO3 mixture, the sintering temperature of LiZnTiMn ferrite successfully reduced to below 900°C from 1100°C without degradation of magnetic properties, meanwhile, both of saturation flux density and remanence square ratio were increased.

Antimicrobial function of Nd3+-doped anatase titania-coated nickel ferrite composite nanoparticles: a biomaterial system.

PubMed

Rana, S; Rawat, J; Sorensson, M M; Misra, R D K

2006-07-01

The present study describes and makes a relative comparison of the antimicrobial function of undoped and neodymium-doped titania coated-nickel ferrite composite nanoparticles processed by uniquely combining the reverse micelle and chemical hydrolysis approaches. This methodology facilitates the formation of undoped and doped photocatalytic titania shells and a magnetic ferrite core. The ferrite core is needed to help in the removal of particles from the sprayed surface using a small magnetic field. Doping of the titania shell with neodymium significantly enhances the photocatalytic and anti-microbial function of the core-shell composite nanoparticles without influencing the magnetic characteristics of the nickel ferrite core. The increased performance is believed to be related to the inhibition of electron-hole recombination and a decrease in the band gap energy of titania. The retention of magnetic strength ensures controlled movement of the composite nanoparticles by the magnetic field, facilitating their application as removable anti-microbial photocatalyst nanoparticles. The consistent behavior of the composite nanoparticles points to the viability of the synthesis process adopted.

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Hernández-Gómez, P.; Muñoz, J. M.; Valente, M. A.; Torres, C.; de Francisco, C.

2013-01-01

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.

An X-ray absorption spectroscopy study of the inversion degree in zinc ferrite nanocrystals dispersed on a highly porous silica aerogel matrix.

PubMed

Carta, D; Marras, C; Loche, D; Mountjoy, G; Ahmed, S I; Corrias, A

2013-02-07

The structural properties of zinc ferrite nanoparticles with spinel structure dispersed in a highly porous SiO(2) aerogel matrix were compared with a bulk zinc ferrite sample. In particular, the details of the cation distribution between the octahedral (B) and tetrahedral (A) sites of the spinel structure were determined using X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the zinc ferrite spinel structures varies with particle size. In particular, in the bulk microcrystalline sample, Zn(2+) ions are at the tetrahedral sites and trivalent Fe(3+) ions occupy octahedral sites (normal spinel). When particle size decreases, Zn(2+) ions are transferred to octahedral sites and the degree of inversion is found to increase as the nanoparticle size decreases. This is the first time that a variation of the degree of inversion with particle size is observed in ferrite nanoparticles grown within an aerogel matrix.

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

NASA Astrophysics Data System (ADS)

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.

Controlled synthesis and microwave absorption properties of Ni0.6Zn0.4Fe2O4/PANI composite via an in-situ polymerization process

NASA Astrophysics Data System (ADS)

Wang, Min; Ji, Guangbin; Zhang, Baoshan; Tang, Dongming; Yang, Yi; Du, Youwei

2015-03-01

The binary composites of conducting polyaniline (PANI) and nickle zinc ferrite were synthesized by an in-situ polymerization process, and the electromagnetic absorption properties of the composites were also investigated. The FT-IR spectra present the peaks of PANI (1562, 1481, 1301, 1109, and 799 cm-1) and the bonds of NiZn ferrite (579 and 390 cm-1), indicating the existence of both NiZn ferrite particles and PANI in the composites. With the increasing ratio of nickle zinc ferrite, the composites distributes in irregular compared with pure PANI and Ni0.6Zn0.4Fe2O4. The TG curves of the pure PANI and PANI/Ni0.6Zn0.4Fe2O4 composites with different molar ratios clearly show the increase percentage of the ferrite in the composites. Furthermore, we found that the excellent electromagnetic absorption properties and wide absorption bandwidth can be achieved by adjusting proper molar ratios Ni0.6Zn0.4Fe2O4 to PANI. The maximum reflection loss of Ni0.6Zn0.4Fe2O4/PANI can reach to -41 dB at 12.8 GHz and the bandwidth exceeding -10 dB can reach to 5 GHz with the absorber thickness of 2.6 mm at the molar ratio of 1:2. This can be attributed to the enhancing magnetic loss and the better impedance matching. Therefore, Ni0.6Zn0.4Fe2O4/PANI ferrite composites can become a new kind of candidate in the field of the microwave absorbing.

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

NASA Astrophysics Data System (ADS)

Momeni, Amir; Kazemi, Shahab; Bahrani, Ali

2013-10-01

The hot deformation characteristics of 1.4462 duplex stainless steel (DSS) were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100°C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-Hollomon parameter ( Z) increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6.×1015 (ln Z=35.5), a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction (EBSD) confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

Effect of austempering temperature and time on mechanical properties of SAE 9260 steel

NASA Astrophysics Data System (ADS)

Dalwatkar, Ranjit; Prabhu, N.; Singh, R. K. P.

2018-04-01

This work describes the effect of austempering heat treatment on microstrcuture and mechanical properties of SAE 9260 steel. Steel samples, austenitized at 900 °C for one hour, were isothermally heat treated in the temperature range 300,325 and 350 °C for different times. Microstructural characterization was carried out using optical and scanning electron microscopes. The microstructure of the austempered samples consisted of bainitic ferrite and retained austenite. The volume fraction of retained austenite was determined using X-ray diffraction. Isothermal heat treatment at 350 °C for 20 min, resulted in a retained austenite content of around 38% in the microstructure. Increase in isothermal transformation temperature led to an increase in the fraction of retained austenite. Also, good combination of strength and ductility was obtained in the samples with increased amounts of retained austenite.

Structural elucidation and magnetic behavior evaluation of Cu-Cr doped BaCo-X hexagonal ferrites

NASA Astrophysics Data System (ADS)

Azhar Khan, Muhammad; Hussain, Farhat; Rashid, Muhammad; Mahmood, Asif; Ramay, Shahid M.; Majeed, Abdul

2018-04-01

Ba2-xCuxCo2CryFe28-yO46 (x = 0.0, 0.1, 0.2, 0.3, 0.4, y = 0.0, 0.2, 0.4, 0.6, 0.8) X-type hexagonal ferrites were synthesized via micro-emulsion route. The techniques which were applied to characterize the prepared samples are as follows: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dielectric measurements and vibrating sample magnetometer (VSM). The structural parameters i.e. lattice constant (a, c), cell volume (V), X-ray density, bulk density and crystallite size of all the prepared samples were obtained using XRD analysis. The lattice parameters 'a' and 'c' increase from 5.875 Å to 5.934 Å and 83.367 Å to 83.990 Å respectively. The crystallite size of investigated samples lies in the range of 28-32 nm. The magnetic properties of all samples have been calculated by vibrating sample magnetometer (VSM) analysis. The increase in coercivity (Hc) was observed with the increase of doping contents. It was observed that the coercivity (Hc) of all prepared samples is inversely related to the crystalline size which reflects that all materials are super-paramagnetic. The dielectric parameters i.e. dielectric constant, dielectric loss, tangent loss etc were obtained in the frequency range of 1 MHz-3 GHz and followed the Maxwell-Wagner's model. The significant variation the dielectric parameters are observed with increasing frequency. The maximum Q value is obtained at ∼2 GHz due to which these materials are used for high frequency multilayer chip inductors.

Electroplating sludge derived zinc-ferrite catalyst for the efficient photo-Fenton degradation of dye.

PubMed

Cao, Zhenbang; Zhang, Jia; Zhou, Jizhi; Ruan, Xiuxiu; Chen, Dan; Liu, Jianyong; Liu, Qiang; Qian, Guangren

2017-05-15

A zinc-dominant ferrite catalyst for efficient degradation of organic dye was prepared by the calcination of electroplating sludge (ES). Characterizations indicated that zinc ferrite (ZnFe 2 O 4 ) coexisted with Fe 2 O 3 structure was the predominant phase in the calcined electroplating sludge (CES). CES displayed a high decolorization ratio (88.3%) of methylene blue (MB) in the presence of H 2 O 2 combined with UV irradiation. The high efficiency could be ascribed to the photocatalytic process induced by ZnFe 2 O 4 and the photo-Fenton dye degradation by ferrous content, and a small amount of Al and Mg in the sludge might also contribute to the catalysis. Moreover, the degradation capability of dye by CES was supported by the synthetic ZnFe 2 O 4 with different Zn to Fe molar ratio (n(Zn): n(Fe)), as 84.81%-86.83% of dye was removed with n(Zn): n(Fe) ranged from 1:0.5 to 1:3. All synthetic ferrite samples in the simulation achieved adjacent equilibrium decolorization ratio, the flexible proportioning of divalent metal ions (M 2+ ) to trivalent metal ions (M 3+ ) applied in the synthesis indicated that the catalyst has a high availability. Therefore, an efficacious catalyst for the degradation of dye can potentially be derived from heavy metal-containing ES, it's a novel approach for the reutilization of ES. Copyright © 2016 Elsevier Ltd. All rights reserved.

The effect of highly activated hopping process on the physical properties of Co-Zn-La ferrite

NASA Astrophysics Data System (ADS)

Ahmed, M. A.; EL-Sayed, M. M.; EL-Desoky, M. M.

2010-01-01

Samples of Co 1-xZn xLa yFe 2-yO 4, 0.1≤ x≤0.9, y=0.25, were prepared using standard ceramic technique. X-ray investigations were carried out in order to assure the formation of the samples in single spinel phase. The dielectric constant ε´ was measured at different temperatures as the function of frequencies ranging from 100 kHz to 3 MHz for the investigated samples. The dielectric constant ε´ increases with temperature up to transition temperature T(ε´) and decreases with frequency. ε´ decreases also with increasing Zn content. Tε´ increases continuously with Zn content depending on frequency. The magnetic susceptibility for the prepared samples was measured using Faraday's method at different temperatures as the function of the magnetic field intensity. The magnetic parameters were calculated from the magnetic susceptibility data, in the temperature range 300-800 K at three different magnetic field intensities of 720, 1070 and 1380 Oe. The data show a decrease in the magnetic susceptibility till it reaches the Curie temperature TC. It is noted that the effective magnetic moment ( μeff.) gives the same trend as that of TC with Zn content.

Effects of cooling time and alloying elements on the microstructure of the gleeble-simulated heat-affected zone of 22% Cr duplex stainless steels

NASA Astrophysics Data System (ADS)

Hsieh, Rong-Iuan; Liou, Horng-Yih; Pan, Yeong-Tsuen

2001-10-01

The effects of austenite stabilizers, such as nitrogen, nickel, and manganese, and cooling time on the microstructure of the Gleeble simulated heat-affected zone (HAZ) of 22% Cr duplex stainless steels were investigated. The submerged are welding was performed for comparison purposes. Optical microscopy (OM) and transmission electron microscopy (TEM) were used for microscopic studies. The amount of Cr2N precipitates in the simulated HAZ was determined using the potentiostatic electrolysis method. The experimental results indicate that an increase in the nitrogen and nickel contents raised the δ to transformation temperature and also markedly increased the amount of austenite in the HAZ. The lengthened cooling time promotes the reformation of austenite. An increase in the austenite content reduces the supersaturation of nitrogen in ferrite matrix as well as the precipitation tendency of Cr2N. The optimum cooling time from 800 to 500 °C (Δ t 8/5) obtained from the Gleeble simulation is between 30 and 60 s, which ensures the austenite content in HAZ not falling below 25% and superior pitting and stress corrosion cracking resistance for the steels. The effect of manganese on the formation of austenite can be negligible.

On the S-phase formation and the balanced plasma nitriding of austenitic-ferritic super duplex stainless steel

NASA Astrophysics Data System (ADS)

de Oliveira, Willian R.; Kurelo, Bruna C. E. S.; Ditzel, Dair G.; Serbena, Francisco C.; Foerster, Carlos E.; de Souza, Gelson B.

2018-03-01

The different physical responses of austenite (γ) and ferrite (α) iron structures upon nitriding result in technical challenges to the uniform modification of α-γ materials, as the super duplex stainless steel (SDSS). The effects of voltage (7-10 kV), frequency and pulse width on the nitrogen plasma immersion ion implantation of SDSS (α ∼ 56%, γ ∼ 44%) were investigated, correlated with structural, morphological and mechanical analyses. By controlling the treatment power, temperatures ranged from 292 °C to 401 °C. Despite the overall increase in hardness for any of the employed parameters (from ∼6 GPa to ∼15 GPa), the structure of individual grains was strikingly dissimilar at the same temperatures, depending on the energetic conditions of implantation. Modified-α grains containing iron nitrides (ε-Fe2-3N, γ‧ -Fe4N) presented intense brittleness, whereas the expanded phase γN (S-phase) laid principally in modified-γ grains, exhibiting ductile-like deformation features and thicker layers. The γN was the dominant phase in both α-γ grains at ∼401 °C, providing them with balanced structure and mechanical behavior. These phenomena corroborate with γN as mediator of the process, through a mechanism involving the nitrogen-promoted ferrite to austenite conversion and nitrides dissolution at high temperatures. An approximately linear correlation of the γN content with respect to the ion energy per pulse was demonstrated, which properly embodies limiting effects to the treatment. This can be a parameter for the α-γ steel surface modification, consisting in a better adjustment to obtain more precise control along with temperature.

Development of Duplex Stainless Steels by Field-Assisted Hot Pressing: Influence of the Particle Size and Morphology of the Powders on the Final Mechanical Properties

NASA Astrophysics Data System (ADS)

García-Junceda, A.; Rincón, M.; Torralba, J. M.

2018-01-01

The feasibility of processing duplex stainless steels with promising properties using a powder metallurgical route, including the consolidation by field-assisted hot pressing, is assessed in this investigation. The influence of the particle size and morphology of the raw austenitic and ferritic powders on the final microstructure and properties is also evaluated for an austenitic content of 60 wt pct. In addition, the properties of a new microconstituent generated between the initial constituents are analyzed. The maximum sintered density (98.9 pct) and the best mechanical behavior, in terms of elastic modulus, nanohardness, yield strength, ultimate tensile strength, and ductility, are reached by the duplex stainless steel processed with austenitic and ferritic gas atomized stainless steel powders.

Spectral emissivity of candidate alloys for very high temperature reactors in high temperature air environment

NASA Astrophysics Data System (ADS)

Cao, G.; Weber, S. J.; Martin, S. O.; Sridharan, K.; Anderson, M. H.; Allen, T. R.

2013-10-01

Emissivity measurements for candidate alloys for very high temperature reactors were carried out in a custom-built experimental facility, capable of both efficient and reliable measurements of spectral emissivities of multiple samples at high temperatures. The alloys studied include 304 and 316 austenitic stainless steels, Alloy 617, and SA508 ferritic steel. The oxidation of alloys plays an important role in dictating emissivity values. The higher chromium content of 304 and 316 austenitic stainless steels, and Alloy 617 results in an oxide layer only of sub-micron thickness even at 700 °C and consequently the emissivity of these alloys remains low. In contrast, the low alloy SA508 ferritic steel which contains no chromium develops a thicker oxide layer, and consequently exhibits higher emissivity values.

Low laser power micro-Raman study of Co{sub (1−x)}Mn{sub (x)}Fe{sub 2}O{sub 4} prepared by flash combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baraliya, J. D.

2016-05-23

Manganese substituted Cobalt ferrites of composition with nominal formula Co{sub (1−x)}Mn{sub (x)}Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) prepared by the Flash Combustion Method(FCM). The single phase spinel formation of nano ferrites was confirmed by X-ray diffraction techniques and micro - Raman spectroscopy. The particle size calculated from the Scherrer formula varied within 13 to 17 nm. Lattice parameter, nano particle size, and cation distribution were quantified as a function of the Mn-content in the range x = 0.0 to 1.0. Micro-Raman spectroscopic studies yielded convincing evidence for a transformation of the structure.

Effects of iron deficiency on anisotropy and ferromagnetic resonance linewidth in Bi-doped LiZn ferrite

NASA Astrophysics Data System (ADS)

Jiang, Xiaona; Wang, Wei; Yu, Zhong; Sun, Ke; Lan, Zhongwen; Zhang, Xinran; Harris, Vincent G.

2017-05-01

Bi-doped LiZn ferrites with different iron deficiencies were fabricated by a conventional ceramic method. Anisotropy constant (K1) was calculated and ferromagnetic resonance (FMR) linewidth (ΔH) was investigated. Crystalline anisotropy broadening linewidth (ΔHa) and porosity broadening linewidth (ΔHp) were derived by an approximate calculation based on dipolar narrowing theory, which play a significant role in contributions to FMR linewidth and occupy more than 90 % of ΔH. Physical and static magnetic properties of LiZn ferrite with iron deficiency are presented, which supports a decline in linewidths with increasing iron deficiency. Iron deficiency makes K1, ΔHa and ΔHp reduce. The results also show that ΔHp is the majority of contributions to ΔH in Bi-doped LiZn ferrite and densification is an effective method to decrease ΔH.

Thermo-mechanical process for treatment of welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, R K

1980-03-01

Benefits from thermo-mechanical processing (TMP) of austenitic stainless steel weldments, analogous to hot isostatic pressing (HIP) of castings, most likely result from compressive plastic deformation, enhanced diffusion, and/or increased dislocation density. TMP improves ultrasonic inspectability of austenitic stainless steel welds owing to: conversion of cast dendrites into equiaxed austenitic grains, reduction in size and number of stringers and inclusions, and reduction of delta ferrite content. TMP induces structural homogenization and healing of void-type defects and thus contributes to an increase in elongation, impact strength, and fracture toughness as well as a significant reduction in data scatter for these properties. Anmore » optimum temperature for TMP or HIP of welds is one which causes negligible grain growth and an acceptable reduction in yield strength, and permits healing of porosity.« less

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, Stephen S.; White, Josh; Hosemann, Peter

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. We measured the oxidation kinetic constant (k) as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3–5 orders of magnitude lower across the experimental temperature range. Our results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Density functional calculations of the Mössbauer parameters in hexagonal ferrite SrFe12O19

NASA Astrophysics Data System (ADS)

Ikeno, Hidekazu

2018-03-01

Mössbauer parameters in a magnetoplumbite-type hexagonal ferrite, SrFe12O19, are computed using the all-electron band structure calculation based on the density functional theory. The theoretical isomer shift and quadrupole splitting are consistent with experimentally obtained values. The absolute values of hyperfine splitting parameters are found to be underestimated, but the relative scale can be reproduced. The present results validate the site-dependence of Mössbauer parameters obtained by analyzing experimental spectra of hexagonal ferrites. The results also show the usefulness of theoretical calculations for increasing the reliability of interpretation of the Mössbauer spectra.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

DOE PAGES

Parker, Stephen S.; White, Josh; Hosemann, Peter; ...

2017-11-03

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. We measured the oxidation kinetic constant (k) as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3–5 orders of magnitude lower across the experimental temperature range. Our results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Oxidation Kinetics of Ferritic Alloys in High-Temperature Steam Environments

NASA Astrophysics Data System (ADS)

Parker, Stephen S.; White, Josh; Hosemann, Peter; Nelson, Andrew

2018-02-01

High-temperature isothermal steam oxidation kinetic parameters of several ferritic alloys were determined by thermogravimetric analysis. The oxidation kinetic constant ( k) was measured as a function of temperature from 900°C to 1200°C. The results show a marked increase in oxidation resistance compared to reference Zircaloy-2, with kinetic constants 3-5 orders of magnitude lower across the experimental temperature range. The results of this investigation supplement previous findings on the properties of ferritic alloys for use as candidate cladding materials and extend kinetic parameter measurements to high-temperature steam environments suitable for assessing accident tolerance for light water reactor applications.

Welding Behavior of Free Machining Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

BROOKS,JOHN A.; ROBINO,CHARLES V.; HEADLEY,THOMAS J.

2000-07-24

The weld solidification and cracking behavior of sulfur bearing free machining austenitic stainless steel was investigated for both gas-tungsten arc (GTA) and pulsed laser beam weld processes. The GTA weld solidification was consistent with those predicted with existing solidification diagrams and the cracking response was controlled primarily by solidification mode. The solidification behavior of the pulsed laser welds was complex, and often contained regions of primary ferrite and primary austenite solidification, although in all cases the welds were found to be completely austenite at room temperature. Electron backscattered diffraction (EBSD) pattern analysis indicated that the nature of the base metalmore » at the time of solidification plays a primary role in initial solidification. The solid state transformation of austenite to ferrite at the fusion zone boundary, and ferrite to austenite on cooling may both be massive in nature. A range of alloy compositions that exhibited good resistance to solidification cracking and was compatible with both welding processes was identified. The compositional range is bounded by laser weldability at lower Cr{sub eq}/Ni{sub eq} ratios and by the GTA weldability at higher ratios. It was found with both processes that the limiting ratios were somewhat dependent upon sulfur content.« less

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y3Fe5O12 ferrites

PubMed Central

Chen, Fu; Wang, Xian; Nie, Yan; Li, Qifan; Ouyang, Jun; Feng, Zekun; Chen, Yajie; Harris, Vincent G.

2016-01-01

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3−xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4–8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to −5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits. PMID:27320039

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y3Fe5O12 ferrites.

PubMed

Chen, Fu; Wang, Xian; Nie, Yan; Li, Qifan; Ouyang, Jun; Feng, Zekun; Chen, Yajie; Harris, Vincent G

2016-06-20

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3-xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4-8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to -5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits.

Effect of heat input on dissimilar welds of ultra high strength steel and duplex stainless steel: Microstructural and compositional analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tasalloti, H., E-mail: hamed.tasalloti.kashani@stu

The effect of heat input on the microstructure and compositional heterogeneity of welds of direct-quenched ultra high strength steel (Optim 960 QC) and duplex stainless steel (UNS S32205) was studied. The dissimilar welds were made using GMAW with a fully austenitic filler wire. In addition to grain coarsening in the heat affected zone (HAZ) of the ferritic side, it was found that an increase in heat input correlatively increased the proportional volume of bainitic to martensitic phases. Coarse ferritic grains were observed in the duplex HAZ. Higher heat input, however, had a beneficial effect on the nucleation of austenite inmore » the HAZ. Heat input had a regulatory effect on grain growth within the austenitic weld and more favorable equiaxed austenite was obtained with higher heat input. On the ferritic side of the welds, macrosegregation in the form of a martensitic intermediate zone was observed for all the cooling rates studied. However, on the duplex side, macrosegregation in the fusion boundary was only noticed with higher cooling rates. Microstructural observations and compositional analysis suggest that higher heat input could be beneficial for the structural integrity of the weld despite higher heat input increasing the extent of adverse coarse grains in the HAZ, especially on the ferritic side. - Highlights: •The effect of heat input on dissimilar welds of UHSS and DSS was studied. •Transmutation of the microstructure was discussed in detail. •The influence of heat input on compositional heterogeneity of welds was described. •Higher heat input enhanced bainitic transformation on the ferritic side. •Macrosegregation was affected by the amount of heat input on the DSS side.« less

High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer at Gakushuin University (RINT 2500V, Cr Kα, 45 kV, 250 mA). Composition analysis of the recovered samples was made using SEM-DES. The RIETAN-2000 program was used to perform the Rietveld refinement. The results of the high-pressure phase relation experiments show that stability field of single phase of MgAl2O4-Mg2SiO4 solid solutions spreads at lower pressure than that of pure MgAl2O4 calcium ferrite. The lowest pressure at which the calcium ferrite solid solution can be synthesized is about 23 GPa. The maximum solubility of Mg2SiO4 component is about 35%. Lattice parameters of pure MgAl2O4 calcium ferrite were determined as a = 9.9495(6) Å, b = 8.6466(5) Å, c = 2.7901(2) Å ( Pbnm space group) by the Rietveld refinement. Obtained atomic positions for calcium ferrite-type MgAl2O4 are very similar to those of CaFe2O4 calcium ferrite. Lattice parameters of MgAl2O4-Mg2SiO4 calcium ferrite solid solutions with various compositions indicate that c-axis does not change with the composition and that a- and b-axes have a linear increase and decrease trend with increasing Mg2SiO4 component, respectively.

Si-Ca species modification and microwave sintering for NiZn ferrites

NASA Astrophysics Data System (ADS)

Yang, Yin-Ju; Sheu, Ching-Iuan; Cheng, Syh-Yuh; Chang, Horng-Yi

2004-12-01

NiZn ferrite particles were precoated with Si-Ca precursor by sol-gel method. Thus convention-sintered particles exhibited small grain size about 2 μm and lowered magnetic permeability as well as increased coercive magnetic field effectively. Microwave sintering could suppress grain growth as the same result of conventional sintering specimens with SiO2-CaO precoating. In microwave process, the grain growth inhibition expressed more obviously for the SiO2-CaO precoated specimens. The magnetic permeability (∼300) after SiO2-CaO precoating became lower than original ferrite (∼800) without SiO2-CaO precoating in conventional sintering. However, the magnetic permeability was lowered no matter whether SiO2-CaO precoating in microwave process. On the other hand, microwave sintering possessed short processing time, for example, 1250 °C/5 min, to prohibit ZnO volatilization in accompanied with grain size reduction. Therefore, such contribution increased resistivity to about 12×106 Ω cm compared to 3×106 Ω cm of original NiZn ferrite. The large coercive magnetic field (Hc) was ascribed to the superposition of small grain size and stress induced by microwave sintering.

Phase stability in thermally-aged CASS CF8 under heavy ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Miller, Michael K.; Chen, Wei-Ying

2015-07-01

The stability of the microstructure of a cast austenitic stainless steel (CASS), before and after heavy ion irradiation, was investigated by atom probe tomography (APT). A CF8 ferrite-austenite duplex alloy was thermally aged at 400 degrees C for 10,000 h. After this treatment, APT revealed nanometer-sized G-phase precipitates and Fe-rich alpha and Cr-enriched alpha' phase separated regions in the ferrite. The thermally-aged CF8 specimen was irradiated with 1 MeV Kr ions to a fluence of 1.88 x 10(19) ions/m(2) at 400 degrees C. After irradiation, APT analysis revealed a strong spatial/dose dependence of the G-phase precipitates and the alpha-alpha' spinodalmore » decomposition in the ferrite. For the G-phase precipitates, the number density increased and the mean size decreased with increasing dose, and the particle size distribution changed considerably under irradiation. The inverse coarsening process can be described by recoil resolution. The amplitude of the alpha-alpha' spinodal decomposition in the ferrite was apparently reduced after heavy ion irradiation. (C) 2015 Elsevier B.V. All rights reserved« less

Effect of microalloying elements on microstructure and properties of quenched and tempered constructional steel

NASA Astrophysics Data System (ADS)

Ma, Qingshen; Huang, Leqing; Di, Guobiao; Wang, Yanfeng; Yang, Yongda; Ma, Changwen

2017-09-01

The effects of microalloying elements Nb, V and Ti on microstructure and properties of quenched and tempered steel were studied. Results showed that the addition of microalloying elements led to the formation of bainite and increased strength, while the austenization and ferrite transformation temperature was barely affected, i.e. 10°C. Microalloying elements shortened the incubation time for bainite transformation by refinement of austenite grain, and decreased the hardenability by forming carbides and therefore reducing the carbon content of super-cooled austenite. Either of them promoted the bainite transformation. The better tempering stability was ascribed to the as hot-rolled bainite microstructure and secondary carbide precipitation during tempering.

Low Mn alloy steel for cryogenic service

DOEpatents

Morris, J.W. Jr.; Niikura, M.

A ferritic cryogenic steel which has a relatively low (about 4 to 6%) manganese content and which has been made suitable for use at cryogenic temperatures by a thermal cycling treatment followed by a final tempering. The steel includes 4 to 6% manganese, 0.02 to 0.06% carbon, 0.1 to 0.4% molybdenum and 0 to 3% nickel.

Neutron Absorbing Alloys

DOEpatents

Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

2004-05-04

The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

Low Mn alloy steel for cryogenic service and method of preparation

DOEpatents

Morris, Jr., John W.; Niikura, Masakazu

1981-01-01

A ferritic cryogenic steel which has a relatively low (about 4-6%) manganese content and which has been made suitable for use at cryogenic temperatures by a thermal cycling treatment followed by a final tempering. The steel includes 4-6% manganese, 0.02-0.06% carbon, 0.1-0.4% molybdenum and 0-3% nickel.

Phase Transformation Behavior of Medium Manganese Steels with 3 Wt Pct Aluminum and 3 Wt Pct Silicon During Intercritical Annealing

NASA Astrophysics Data System (ADS)

Sun, Binhan; Fazeli, Fateh; Scott, Colin; Yue, Stephen

2016-10-01

Medium manganese steels alloyed with sufficient aluminum and silicon amounts contain high fractions of retained austenite adjustable to various transformation-induced plasticity/twinning-induced plasticity effects, in addition to a reduced density suitable for lightweight vehicle body-in-white assemblies. Two hot rolled medium manganese steels containing 3 wt pct aluminum and 3 wt pct silicon were subjected to different annealing treatments in the present study. The evolution of the microstructure in terms of austenite transformation upon reheating and the subsequent austenite decomposition during quenching was investigated. Manganese content of the steels prevailed the microstructural response. The microstructure of the leaner alloy with 7 wt pct Mn (7Mn) was substantially influenced by the annealing temperature, including the variation of phase constituents, the morphology and composition of intercritical austenite, the Ms temperature and the retained austenite fraction. In contrast, the richer variant 10 wt pct Mn steel (10Mn) exhibited a substantially stable ferrite-austenite duplex phase microstructure containing a fixed amount of retained austenite which was found to be independent of the variations of intercritical annealing temperature. Austenite formation from hot band ferrite-pearlite/bainite mixtures was very rapid during annealing at 1273 K (1000 °C), regardless of Mn contents. Austenite growth was believed to be controlled at early stages by carbon diffusion following pearlite/bainite dissolution. The redistribution of Mn in ferrite and particularly in austenite at later stages was too subtle to result in a measureable change in austenite fraction. Further, the hot band microstructure of both steels contained a large fraction of coarse-grained δ-ferrite, which remained almost unchanged during intercritical annealing. A recently developed thermodynamic database was evaluated using the experimental data. The new database achieved a better agreement with the experimental results for the 7Mn steel compared with the existing commercial TCFE database; however, some discrepancy in the predicted phase fractions and compositions still existed. The phase transformation behavior of the two steels during annealing and its implication on the design of high aluminum-silicon medium manganese steels were discussed in detail.

Effect of temperature on the magnetic properties of nano-sized M-type barium hexagonal ferrites

NASA Astrophysics Data System (ADS)

Tchouank Tekou Carol, T.; Sharma, Jyoti; Mohammed, J.; Kumar, Sachin; Srivastava, A. K.

2017-07-01

The application of M-type hexagonal ferrites in electronic devices is increasing with technological advancement. This is due to the possibility of improving the physical and magnetic properties to suit the desired application. Enhanced magnetic properties make hexagonal ferrites suitable for hyper frequency and radar absorbing application. In this paper, we investigated the effect of heat-treatment temperature on the structural and magnetic properties of M-type barium hexagonal ferrites with chemical composition Ba1-xAlxFe12-yMnyO19 (x=0.6 and y=0.3) synthesized by sol-gel auto-combustion method and sintered at 750°C, 850°C, 950°C and 1050°C. Characterisations of the prepared samples were done using Fourier transform-infrared (FT-IR), and vibrating sample magnetometer (VSM). The formation of M-type hexaferrite has been confirmed from XRD. The presence of two prominent peaks between 400 cm-1 and 600 cm-1 in the spectra of Fourier transform-infrared spectroscopy (FT-IR) also shows the formation of ferrite phase. Saturation magnetisation (MS), remnant magnetisation (Mr), coercivity (Hc) and squareness ratio (SR) were calculated from the M-H loop obtained from vibrating sample magnetometer (VSM).

Influence of ferrite phase in alite-calcium sulfoaluminate cements

NASA Astrophysics Data System (ADS)

Duvallet, Tristana Yvonne Francoise

Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition. The mechanical data were equivalent to OPC strengths for some compositions with 25% ferrite. This preliminary work constitutes the first research phase of this novel cement and requires additional research for its improvement. Topics for additional research are identified in this dissertation. KEYWORDS: alite, calcium sulfoaluminate, ferrite, low-energy cement, triisopropanolamine.

Investigation on Static Softening Behaviors of a Low Carbon Steel Under Ferritic Rolling Condition

NASA Astrophysics Data System (ADS)

Dong, Haifeng; Cai, Dayong; Zhao, Zhengzheng; Wang, Zhiyong; Wang, Yuhui; Yang, Qingxiang; Liao, Bo

2010-03-01

The study aims to postulate a theoretical hypothesis for the finishing period of ferritic rolling technique of the low carbon steel. The static softening behavior during multistage hot deformation of a low carbon steel has been studied by double hot compression tests at 700-800 °C and strain rate of 1 s-1 using a Gleeble-3500 simulator. Interrupted deformation is conducted with interpass times varying from 1 to 100 s after achieving a true strain of 0.5 in the first stage. The results indicate that the flow stress value at the second deformation is lower than that at the first one, and the flow stress drops substantially. The static softening effects increase with the increase of deformation temperature, holding temperature, and interpass time. The value of the ferritic static softening activation energy is obtained, and the static softening kinetics is modeled by the Avrami equation.

Effect of annealing on particle size, microstructure and gas sensing properties of Mn substituted CoFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Kumar, E. Ranjith; Kamzin, A. S.; Janani, K.

2016-11-01

Microstructure, morphological and gas sensor studies of Mn substituted cobalt ferrite nanoparticles synthesized by a simple evaporation method and auto- combustion method. The influence of heat treatment on phase and particle size of spinel ferrite nanoparticles were determined by X-ray diffraction and Mossbauer spectroscopy. The XRD study reveals that the lattice constant and crystallite size of the samples increases with the increase of annealing temperature. Last one was confirmed by Mossbauer data. The lowest size of particles of MnCoFe2O4 (~3 nm) is obtained by auto combustion method. The spherical shaped nanoparticles are recorded by TEM. Furthermore, conductance response of Mn-Co ferrite nanomaterial was measured by exposing the material to reducing gas like liquefied petroleum gas (LPG) which showed a sensor response of ~0.19 at an optimum operating temperature of 250 °C.

The role of nickel in radiation damage of ferritic alloys

DOE PAGES

Osetsky, Y.; Anento, Napoleon; Serra, Anna; ...

2014-11-26

According to modern theory, damage evolution under neutron irradiation depends on the fraction of self-interstitial atoms (SIAs) produced in the form of one-dimensional glissile clusters. These clusters, having a low interaction cross-section with other defects, are absorbed mainly by grain boundaries and dislocations, creating the so-called production bias. It is known empirically that the addition of certain alloying elements influences many radiation effects, including swelling; however, the mechanisms are unknown in many cases. In this study, we report the results of an extensive multi-technique atomistic level modeling study of SIA clusters mobility in body-centered cubic Fe–Ni alloys. We have foundmore » that Ni interacts strongly with the periphery of clusters, affecting their mobility. The total effect is defined by the number of Ni atoms interacting with the cluster at the same time and can be significant, even in low-Ni alloys. Thus a 1 nm (37SIAs) cluster is practically immobile at T < 500 K in the Fe–0.8 at.% Ni alloy. Increasing cluster size and Ni content enhances cluster immobilization. Finally, this effect should have quite broad consequences in void swelling, matrix damage accumulation and radiation induced hardening and the results obtained help to better understand and predict the effects of radiation in Fe–Ni ferritic alloys.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khader, S. Abdul, E-mail: khadersku@gmail.com; Parveez, Asiya; Sankarappa, T., E-mail: sankarappa@rediffmail.com

The Magneto-electric composites (x) Ni{sub 0.7}Co{sub 0.1}Cu{sub 0.2}Fe{sub 2}O{sub 4} + (1-x) BaTiO{sub 3} (x=10%, 20% and 30%) were synthesized by sintering mixtures of highly ferroelectric BaTiO{sub 3} (BT) and highly magneto-strictive component Ni{sub 0.7}Co{sub 0.1}Cu{sub 0.2}Fe{sub 2}O{sub 4} (NCCF). The presences of constituent phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for NCCF ferrite phase and tetragonal perovskite structure for BT and, both spinel and pervoskite structures for synthesized ME composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscopemore » (FESEM). Frequency and composition dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at room temperature using Hioki LCR Hi-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The hysteresis behavior was studied to understand the magnetic ordering in the synthesized composites using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khader, S. Abdul, E-mail: khadersku@gmail.com; Sankarappa, T., E-mail: sankarappa@rediffmail.com; Giridharan, N. V.

The Magneto-electric composites (x) Mg{sub 0.2}Cu{sub 0.3}Zn{sub 0.5}Fe{sub 2}O{sub 4} + (1-x) Ba{sub 0.8}Zr{sub 0.2}TiO{sub 3} (x=15%,30%,45%) were synthesized by sintering mixtures of highly ferroelectric Ba{sub 0.8}Zr{sub 0.2}TiO{sub 3} (BZT) and highly magneto-strictive component Mg{sub 0.2}Cu{sub 0.3}Zn{sub 0.5}Fe{sub 2}O{sub 4} (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM).more » Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The magnetic properties of synthesized composites were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.« less

Structural, dielectric and magnetic studies of (x) Ni0.7Co0.1Cu0.2Fe2O4 + (1-x) BaTiO3 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Parveez, Asiya; Giridharan, N. V.; Sankarappa, T.

2016-05-01

The Magneto-electric composites (x) Ni0.7Co0.1Cu0.2Fe2O4 + (1-x) BaTiO3 (x=10%, 20% and 30%) were synthesized by sintering mixtures of highly ferroelectric BaTiO3 (BT) and highly magneto-strictive component Ni0.7Co0.1Cu0.2Fe2O4 (NCCF). The presences of constituent phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for NCCF ferrite phase and tetragonal perovskite structure for BT and, both spinel and pervoskite structures for synthesized ME composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency and composition dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at room temperature using Hioki LCR Hi-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The hysteresis behavior was studied to understand the magnetic ordering in the synthesized composites using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.

Structural, dielectric and magnetic studies of (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Giridharan, N. V.; Chaudhuri, Arka; Sankarappa, T.

2016-05-01

The Magneto-electric composites (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 (x=15%,30%,45%) were synthesized by sintering mixtures of highly ferroelectric Ba0.8Zr0.2TiO3 (BZT) and highly magneto-strictive component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The magnetic properties of synthesized composites were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.

Cation distribution correlated with magnetic properties of cobalt ferrite nanoparticles defective by vanadium doping

NASA Astrophysics Data System (ADS)

Heiba, Zein K.; Mohamed, Mohamed Bakr; Ahmed, S. I.

2017-11-01

Nanoparticles cobalt ferrite, vacancies defective through vanadium substitution for iron, were synthesized by a sol-gel method. Two systems CoFe2-xVxO4 (0.0 ≤ x ≤ 0.25) and CoFe2-1.67xVxO4 (x = 0.1, 0.2) were prepared. The crystal structure, microstructure and magnetic properties were investigated using XRD, SEM and VSM magnetometer. The occupancy of tetrahedral and octahedral sites by different cations was determined by Rietveld analysis and correlated with magnetic measurements. Vanadium resides at octahedral sites up to x = 0.10, while for higher values it resides mainly at octahedral sites with a lesser amount at the tetrahedrons. Upon increasing the vanadium content, the cell parameter decreases and the bond lengths of the tetrahedral and octahedral sites change opposite to each other. The change in the coercivity and saturation magnetization is correlated with cation distribution. For the same amount of doping x, the iron deficient samples CoFe2-1.67xVxO4 have saturation magnetization obviously reduced than the corresponding samples in CoFe2-xVxO4. The spin canting between cations in A- and B- sites was discussed in details based on Yafet-Kittel triangular arrangement model.

Deformation-Induced Dissolution and Precipitation of Nitrides in Austenite and Ferrite of a High-Nitrogen Stainless Steel

NASA Astrophysics Data System (ADS)

Shabashov, V. A.; Makarov, A. V.; Kozlov, K. A.; Sagaradze, V. V.; Zamatovskii, A. E.; Volkova, E. G.; Luchko, S. N.

2018-02-01

Methods of Mössbauer spectroscopy and electron microscopy have been used to study the effect of the severe plastic deformation by high pressure torsion in Bridgman anvils on the dissolution and precipitation of chromium nitrides in the austenitic and ferritic structure of an Fe71.2Cr22.7Mn1.3N4.8 high-nitrogen steel. It has been found that an alternative process of dynamic aging with the formation of secondary nitrides affects the kinetics of the dissolution of chromium nitrides. The dynamic aging of ferrite is activated with an increase in the deformation temperature from 80 to 573 K.

Impacts of neodymium on structural, spectral and dielectric properties of LiNi0.5Fe2O4 nanocrystalline ferrites fabricated via micro-emulsion technique

NASA Astrophysics Data System (ADS)

Gilani, Zaheer Abbas; Warsi, Muhammad Farooq; Khan, Muhammad Azhar; Shakir, Imran; Shahid, Muhammad; Anjum, Muhammad Naeem

2015-09-01

Soft ferrites are technologically advanced smart materials and their properties can be tailored by controlling the chemical composition and judicial choice of the metal elements. In this article we discussed the effect of rare earth neodymium (Nd3+) on various properties of LiNi0.5NdxFe2-xO4 spinel ferrites. These ferrites have been synthesized by facile micro-emulsion route and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), a.c. electrical conductivity and thermal analysis. The influence of Nd3+ doping on structural and electrical parameters has been investigated. XRD analysis revealed the formation of single cubic spinel structure for x≤0.07. Few traces of secondary phase (NdFeO3) were found for x≥0.105. The secondary phase induced owing to the solubility limit of Nd3+ cations in these ferrites. The lattice parameter (a) and crystallite size (D) both exhibit non-linear relation. The values of "a" and "D" were found in the range 8.322-8.329 Å and 25-32 nm respectively. These variations were attributed to the larger ionic radius of Nd3+ cations as compared to the host cations and lattice strain produced in these ferrites. The dielectric parameters were studied in the range 1 MHz to 3 GHz and these parameters were damped by Nd3+ incorporation and also by increasing the frequency. The reduced dielectric parameters observed in wide frequency range proposed that these nanocrystalline ferrites are potential candidates for fabricating the devices which are required to operate at GHz frequencies.

Modulation in magnetic exchange interaction, core shell structure and Hopkinson's peak with chromium substitution into Ni0.75Co0.25Fe2O4 nano particles

NASA Astrophysics Data System (ADS)

Uday Bhasker, S.; Choudary, G. S. V. R. K.; Reddy, M. V. Ramana

2018-05-01

The ever growing applications and ever evolving challenges of magnetic nano particles has been motivating the researchers from various disciplines towards this area of magnetic nano particles. Cation substitutional effect on the magnetic structure of the nanoparticles forms a crucial aspect in their applications. Here the environmentally benign auto combustion method was employed to synthesize chromium substituted nickel cobalt ferrite (Ni0.75Co0.25Fe2-xCrxO4; x = 0, 0.10, 0.15) nano particles, from aqueous metal nitrate solutions. Chromium substitution has shown its effect on the structural, magnetic and electrical properties of Ni0.75Co0.25Fe2O4. Structural and phase analysis of the prepared samples show increased phase purity of ferrite sample with increasing Cr substitution. The TEM (Transmission Electron Microscope) image confirms the nano size of the particles, EDS (Energy dispersive X-ray Spectroscopy) has supported the stoichiometry of the prepared samples and FTIR (Fourier-transform infrared spectroscopic) analysis confirms the spinel structure and also suggests cation redistributions with chromium substitution. VSM (Vibrational Sample Magnetometer) is used to study the magnetic properties through magnetic hysteresis (M-H) loop and magnetic Hopkinson effect. All samples show hysteresis and show reduction in magnetic properties with increase in chromium content. The thermo magnetic study shows Hopkinson peak(s) in the magnetization vs. temperature (M-T) graph and also shows variation in the nature of Hopkinson peak with chromium substitution. Possible reasons for the changes in the nature of the peak are discussed.

Small-scale characterisation of irradiated nuclear materials: Part I – Microstructure

DOE PAGES

Edmondson, P. D.; London, A.; Xu, A.; ...

2014-11-26

The behaviour of nanometre-scale precipitates in oxide dispersion strengthened (ODS) ferritic alloys and tungsten-rhenium alloys for nuclear applications has been examined by atom probe tomography (APT). Low Re content tungsten alloys showed no evidence of Re clustering following self-ion irradiation whereas the 25 at.% Re resulted in cluster formation. The size and composition of clusters varied depending on the material form during irradiation (pre-sharpened needle or bulk). Lastly, these results highlight the care that must be taken in interpreting data from ion irradiated pre-sharpened needles due to the presence of free surfaces. Self-ion irradiation of the ODS ferritic alloy resultedmore » in a change in the composition of the clusters, indicating a transition from a near-stoichiometric Y 2Ti 2O 7 composition towards a Ti 2YO 5.« less

Electromagnetic non-destructive technique for duplex stainless steel characterization

NASA Astrophysics Data System (ADS)

Rocha, João Vicente; Camerini, Cesar; Pereira, Gabriela

2016-02-01

Duplex stainless steel (DSS) is a two-phase (ferrite and austenite) material, which exhibits an attractive combination of mechanical properties and high corrosion resistance, being commonly employed for equipment of petrochemical plants, refining units and oil & gas platforms. The best properties of DSS are achieved when the phases are in equal proportions. However, exposition to high temperatures (e.g. welding process) may entail undesired consequences, such as deleterious phases precipitation (e.g. sigma, chi) and different proportion of the original phases, impairing dramatically the mechanical and corrosion properties of the material. A detailed study of the magnetic behavior of DSS microstructure with different ferrite austenite ratios and deleterious phases content was accomplished. The non destructive method evaluates the electromagnetic properties changes in the material and is capable to identify the presence of deleterious phases into DSS microstructure.

Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

NASA Astrophysics Data System (ADS)

Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2018-05-01

Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

Al3+ ions dependent structural and magnetic properties of Co-Ni nano-alloys.

PubMed

Kadam, R H; Alone, Suresh T; Gaikwad, Anil S; Birajdar, A P; Shirsath, Sagar E

2014-06-01

Ferrite samples with a chemical formula Co0.5Ni0.5Al(x)Fe(2-x)O4 (where x = 0.0, 0.25, 0.5, 0.75 and 1.0) were synthesized by sol-gel auto-combustion method. The synthesized samples were annealed at 600 degrees C for 4 h. An analysis of X-ray diffraction (XRD) patterns reveals the formation of single phase cubic spinel structure. The lattice parameter decreased linearly with the increasing Al content x. Nano size of the powders were confirmed by the transmission electron micrographs (TEM). Particle size, bulk density decreased whereas specific surface area and porosity of the samples increased with the Al substitution. Cation distribution of constituent ions shows linear dependence of Al substitution. Based on the cation distribution obtained from XRD data, structural parameters such as lattice parameters, ionic radii of available sites and the oxygen parameter 'u' is calculated. Saturation magnetization (M(s)), magneton number (n(B)) and coercivity (H(c)) decreased with the Al substitution. Possible explanation for the observed structural and magnetic behavior with various Al content are discussed.

Oxidation Behavior of Ferritic Stainless Steels under SOFC Interconnect Exposure Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhenguo; Walker, Matthew S.; Singh, Prabhakar

The oxidation of ferritic stainless steels has been studied under solid oxide fuel cell (SOFC) interconnect “dual” exposure conditions, i.e. simultaneous exposure to air on one side of the sample, and moist hydrogen on the other side. This paper focuses on the oxidation behavior of ferritic stainless steels during the isothermal oxidation in the dual environments. It was found that scales grown on the air side under these dual exposure conditions can be significantly different from scales grown on samples exposed to air on both sides. In contrast, no substantial difference was observed between the scales grown on the fuelmore » side of the dual atmosphere samples and scales grown on samples exposed to moist hydrogen on both sides. AISI430, with 17% Cr, suffered localized attack via formation of Fe2O3 hematite-rich nodules on the air side of dual exposure samples, while the spinel top layer of the air side scale of Crofer22 APU (23% Cr) was enriched in iron. For E-brite, with the highest Cr content (27%), no unusual phases were found in the scale on the air side, but it was noticed the air side scale was less dense and appeared to be more prone to defects than the scale grown in air only. The anomalous oxidation behavior of ferritic stainless steels on the air side of dual exposure specimens is related to the transport of hydrogen through the steel and its subsequent presence in the air side scale.« less

Aluminide slurry coatings for protection of ferritic steel in molten nitrate corrosion for concentrated solar power technology

NASA Astrophysics Data System (ADS)

Audigié, Pauline; Bizien, Nicolas; Baráibar, Ignacio; Rodríguez, Sergio; Pastor, Ana; Hernández, Marta; Agüero, Alina

2017-06-01

Molten nitrates can be employed as heat storage fluids in solar concentration power plants. However molten nitrates are corrosive and if operating temperatures are raised to increase efficiencies, the corrosion rates will also increase. High temperature corrosion resistant coatings based on Al have demonstrated excellent results in other sectors such as gas turbines. Aluminide slurry coated and uncoated P92 steel specimens were exposed to the so called Solar Salt (industrial grade), a binary eutectic mixture of 60 % NaNO3 - 40 % KNO3, in air for 2000 hours at 550°C and 580°C in order to analyze their behavior as candidates to be used in future solar concentration power plants employing molten nitrates as heat transfer fluids. Coated ferritic steels constitute a lower cost technology than Ni based alloy. Two different coating morphologies resulting from two heat treatment performed at 700 and 1050°C after slurry application were tested. The coated systems exhibited excellent corrosion resistance at both temperatures, whereas uncoated P92 showed significant mass loss from the beginning of the test. The coatings showed very slow reaction with the molten Solar Salt. In contrast, uncoated P92 developed a stratified, unprotected Fe, Cr oxide with low adherence which shows oscillating Cr content as a function of coating depth. NaFeO2 was also found at the oxide surface as well as within the Fe, Cr oxide.

Recent advances in nanosized Mn-Zn ferrite magnetic fluid hyperthermia for cancer treatment.

PubMed

Lin, Mei; Huang, Junxing; Sha, Min

2014-01-01

This paper reviews the recent research and development of nanosized manganese zinc (Mn-Zn) ferrite magnetic fluid hyperthermia (MFH) for cancer treatment. Mn-Zn ferrite MFH, which has a targeted positioning function that only the temperature of tumor tissue with magnetic nanoparticles can rise, while normal tissue without magnetic nanoparticles is not subject to thermal damage, is a promising therapy for cancer. We introduce briefly the composition and properties of magnetic fluid, the concept of MFH, and features of Mn-Zn ferrite magnetic nanoparticles for MFH such as thermal bystander effect, universality, high specific absorption rate, the targeting effect of small size, uniformity of hyperthermia temperature, and automatic temperature control and constant temperature effect. Next, preparation methods of Mn-Zn ferrite magnetic fluid are discussed, and biocompatibility and biosecurity of Mn-Zn ferrite magnetic fluid are analyzed. Then the applications of nanosized Mn-Zn ferrite MFH in cancer are highlighted, including nanosized Mn-Zn ferrite MFH alone, nanosized Mn-Zn ferrite MFH combined with As2O3 chemotherapy, and nanosized Mn-Zn ferrite MFH combined with radiotherapy. Finally, the combination application of nanosized Mn-Zn ferrite MFH and gene-therapy is conceived, and the challenges and perspectives for the future of nanosized Mn-Zn ferrite MFH for oncotherapy are discussed.

Low-Temperature Aging Characteristics of Type 316L Stainless Steel Welds: Dependence on Solidification Mode

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Watanabe, Yutaka

2008-06-01

Thermal aging embrittlement of light water reactor (LWR) components made of stainless steel cast has been recognized as a potential degradation issue, and careful attention has been paid to it. Although welds of austenitic stainless steels have γ-δ duplex microstructure, which is similar to that of the stainless steel cast, examination of the thermal aging characteristics of the stainless steel welds is very limited. In this investigation, two types of type 316L stainless steel weld metal with different solidification modes were prepared using two kinds of filler metals having tailored Ni equivalent and Cr equivalent. Differences between the two weld metals in the morphology of microstructure, in the composition of δ-ferrite, and in hardening behaviors with isothermal aging at 335 °C have been investigated. The hardness of the ferrite phase has increased with aging time, while the hardness of austenite phase has stayed the same. The mottled aspect has been observed in δ-ferrite of aged samples by transmission electron microscopy (TEM) observation. These characteristics suggest that spinodal decomposition has occurred in δ-ferrite by aging at 335 °C. The age-hardening rate of δ-ferrite was faster for the primary austenite solidification mode (AF mode) sample than the primary ferrite solidification mode (FA mode) sample in the initial stage of the aging up to 2000 hours. It has been suggested that the solidification mode can affect the kinetics of spinodal decomposition.

The phases and magnetic properties of (Ti, Co), and Cr doped Zn 2Y-type hexagonal ferrite

NASA Astrophysics Data System (ADS)

Chang, Y. H.; Wang, C. C.; Chin, T. S.; Yen, F. S.

1988-04-01

The phases and magnetic properties of Y-type hexagonal ferrite, Ba 2Zn 2 (Ti, Co) yFe 12-2 yO 22 doped with two sets of ions, (Ti, Co) and Cr were studied. In (Ti, Co) - doped ferrites the second phase appears at y ⩾ 0.6, which is a spinel type with the formula of (Zn 1-ηCo η)(Fe 2-δCo δ)O 4. Two resonant peaks are observed in ESR studies at the fields of 1020 and 2430 Oe, respectively, at a frequency of 9.684 GHz. The linewidth increases with the addition of the dopants. In chromium doped ferrite, two phases are identified as the amount of chromium is up to 0.2: spinel type of Zn(Fe 2-ɛCr ɛ)O 4 and orthorhombic BaCr 2O 4. Although the amount of Cr used does not influence the resonant field of the unique peak of the derivative curves from ESR, it eventually enlarges the linewidth.

A review of recent progress in coatings, surface modifications and alloy developments for solid oxide fuel cell ferritic stainless steel interconnects

NASA Astrophysics Data System (ADS)

Shaigan, Nima; Qu, Wei; Ivey, Douglas G.; Chen, Weixing

Ferritic stainless steels have become the standard material for solid oxide fuel cell (SOFC) interconnect applications. The use of commercially available ferritic stainless steels, not specifically designed for interconnect application, however, presents serious issues leading to premature degradation of the fuel cell stack, particularly on the cathode side. These problems include rapidly increasing contact resistance and volatilization of Cr from the oxide scales, resulting in cathode chromium poisoning and cell malfunction. To overcome these issues, a variety of conductive/protective coatings, surface treatments and modifications as well as alloy development have been suggested and studied over the past several years. This paper critically reviews the attempts performed thus far to mitigate the issues associated with the use of ferritic stainless steels on the cathode side. Different approaches are categorized and summarized and examples for each case are provided. Finally, directions and recommendations for the future studies are presented.

The effects of particle size and surface coating on the cytotoxicity of nickel ferrite.

PubMed

Yin, H; Too, H P; Chow, G M

2005-10-01

The safety and toxicity of nanoparticles are of growing concern despite their significant scientific interests and promising potentials in many applications. The properties of nanoparticles depend not only on the size but also the structure, microstructure and surface coating. These in turn are controlled by the synthesis and processing conditions. The dependence of cytotoxicity on particle size and on the presence of oleic acid as surfactant on nickel ferrite particles were investigated in vitro using the Neuro-2A cell line as a model. For nickel ferrite particles without oleic acid prepared by ball milling, cytotoxicity was independent of particle size within the given mass concentrations and surface areas accessible to the cells. For nickel ferrite particles coated with oleic acid prepared by the polyol method, the cytotoxicity significantly increased when one or two layers of oleic acid were deposited. Large particles (150+/-50 nm diameter) showed a higher cytotoxicity than smaller particles (10+/-3 nm diameter).

Characterization of phase properties and deformation in ferritic-austenitic duplex stainless steels by nanoindentation and finite element method

DOE PAGES

Schwarm, Samuel C.; Kolli, R. Prakash; Aydogan, Eda; ...

2016-11-03

The phase properties and deformation behavior of the δ–ferrite and γ–austenite phases of CF–3 and CF–8 cast duplex stainless steels were characterized by nanoindentation and microstructure-based finite element method (FEM) models. We evaluated the elastic modulus of each phase and the results indicate that the mean elastic modulus of the δ–ferrite phase is greater than that of the γ–austenite phase, and the mean nanoindentation hardness values of each phase are approximately the same. Furthermore, the elastic FEM model results illustrate that greater von Mises stresses are located within the δ–ferrite phase, while greater von Mises strains are located in themore » γ–austenite phase in response to elastic deformation. The elastic moduli calculated by FEM agree closely with those measured by tensile testing. Finally, the plastically deformed specimens exhibit an increase in misorientation, deformed grains, and subgrain structure formation as measured by electron backscatter diffraction (EBSD).« less

Characterization of phase properties and deformation in ferritic-austenitic duplex stainless steels by nanoindentation and finite element method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwarm, Samuel C.; Kolli, R. Prakash; Aydogan, Eda

The phase properties and deformation behavior of the δ–ferrite and γ–austenite phases of CF–3 and CF–8 cast duplex stainless steels were characterized by nanoindentation and microstructure-based finite element method (FEM) models. We evaluated the elastic modulus of each phase and the results indicate that the mean elastic modulus of the δ–ferrite phase is greater than that of the γ–austenite phase, and the mean nanoindentation hardness values of each phase are approximately the same. Furthermore, the elastic FEM model results illustrate that greater von Mises stresses are located within the δ–ferrite phase, while greater von Mises strains are located in themore » γ–austenite phase in response to elastic deformation. The elastic moduli calculated by FEM agree closely with those measured by tensile testing. Finally, the plastically deformed specimens exhibit an increase in misorientation, deformed grains, and subgrain structure formation as measured by electron backscatter diffraction (EBSD).« less

Study on microstructural changes in thermally-aged stainless steel weld-overlay cladding of nuclear reactor pressure vessels by atom probe tomography

NASA Astrophysics Data System (ADS)

Takeuchi, T.; Kameda, J.; Nagai, Y.; Toyama, T.; Nishiyama, Y.; Onizawa, K.

2011-08-01

The effect of thermal aging on microstructural changes was investigated in stainless steel weld-overlay cladding composed of 90% austenite and 10% δ-ferrite phases using atom probe tomography (APT). In as-received materials subjected to cooling process after post-welding heat treatments (PWHT), a slight fluctuation of the Cr concentration was already observed due to spinodal decomposition in the ferrite phase but not in the austenitic phase. Thermal aging at 400 °C for 10,000 h caused not only an increase in the amplitude of spinodal decomposition but also the precipitation of G phases with composition ratios of Ni:Si:Mn = 16:7:6 in the ferrite phase. The chemical compositions of M 23C 6 type carbides seemed to be formed at the austenite/ferrite interface were analyzed. The analyses of the magnitude of the spinodal decomposition and the hardness implied that the spinodal decomposition was the main cause of the hardening.

Effect of vanadium doping on structural and magnetic properties of defective nano-nickel ferrite

NASA Astrophysics Data System (ADS)

Heiba, Zein K.; Mohamed, Mohamed Bakr; Wahba, Adel Maher; Almalowi, M. I.

2018-04-01

Nano-nickel ferrites defected by vanadium doping (NiV x Fe2-1.67 x O4, 0 ≤ x ≤ 0.25) were prepared using a simple sol gel method. Rietveld analysis revealed a nonmonotonic change in lattice parameter, oxygen parameter and magnetization upon doping with vanadium. Cation distributions suggested from either Rietveld analysis or from experimental magnetic moments were in a good agreement. For low doping values ( x = 0.05), vanadium was residing mainly in octahedral sites, while for samples with vanadium content ( x ≥ 0.1) a significant part of vanadium ions resided at tetrahedral sites; a result which has been confirmed by the analysis of Fourier-transform infrared (FTIR) spectrums obtained for the samples. The transmission electron microscope (TEM) image showed fine spherical particles with size of ˜ 11 nm. All samples showed a superparamagnetic nature with a nonmonotonic change of either magnetization ( M S) or coercivity (H C) with the content of nonmagnetic V5+. The cation occupancies indicated presence of an enormous number of vacancies through doping with high valence cation V5+, making present samples potential electrodes for Li- or Na-ion batteries.

Additive manufacturing of complex-shaped graded TiC/steel composites

DOE PAGES

Levy, Asaf; Miriyev, Aslan; Elliott, Amy; ...

2017-01-12

Complex-shaped TiCx ceramic preforms with a gradient of carbon content in the titanium carbide phase (x changes from 0.7 to 0.98) were fabricated for the first time by Binder jet 3D printing technology. The complex-shaped preforms were infiltrated with molten carbon steel (0.7 wt.%C). Thermodynamic considerations showed that carbon could be transferred from titanium carbide to steel and vice versa according to the initial concentration of carbon (activity) in both phases. After infiltration, solidification and slow cooling, a microstructural gradient was obtained throughout the steel matrix from ferrite, in the region where the steel was in contact with titanium carbidemore » of low carbon content (x=0.7), to pearlite, in the region where the steel underwent interactions with stoichiometric titanium carbide (x=0.98). After annealing at 900°C and quenching in oil, a structural gradient in the steel matrix from ferrite to martensite was obtained, resulting in a hardness gradient of 700-1600 HV. The suggested processing approach allows for fabrication of complex-shaped graded composites with the desired property gradient suitable for a wide range of practical applications.« less

Additive manufacturing of complex-shaped graded TiC/steel composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levy, Asaf; Miriyev, Aslan; Elliott, Amy

Complex-shaped TiCx ceramic preforms with a gradient of carbon content in the titanium carbide phase (x changes from 0.7 to 0.98) were fabricated for the first time by Binder jet 3D printing technology. The complex-shaped preforms were infiltrated with molten carbon steel (0.7 wt.%C). Thermodynamic considerations showed that carbon could be transferred from titanium carbide to steel and vice versa according to the initial concentration of carbon (activity) in both phases. After infiltration, solidification and slow cooling, a microstructural gradient was obtained throughout the steel matrix from ferrite, in the region where the steel was in contact with titanium carbidemore » of low carbon content (x=0.7), to pearlite, in the region where the steel underwent interactions with stoichiometric titanium carbide (x=0.98). After annealing at 900°C and quenching in oil, a structural gradient in the steel matrix from ferrite to martensite was obtained, resulting in a hardness gradient of 700-1600 HV. The suggested processing approach allows for fabrication of complex-shaped graded composites with the desired property gradient suitable for a wide range of practical applications.« less

Synthesis, morphology and electrical properties of Co2+ substituted NiCuZn ferrites for MLCI applications

NASA Astrophysics Data System (ADS)

Kabbur, S. M.; Waghmare, S. D.; Ghodake, U. R.; Suryavanshi, S. S.

2018-04-01

Co2+ is a fast relaxing ion which can enhance microwave properties. This work focuses on the synthesis and analysis of Ni0.25-xCoxCu0.30Zn0.45Fe2O4 (x = 0.00, 0.05, 0.01, 0.15, 0.20 and 0.25) ferrites by auto combustion method using glycine as the chelating agent. From X-ray Diffraction (XRD) spectra, the structural parameters are analysed. The lattice parameter (a) decreases due to smaller ionic radius of Co2+ (0.072 nm) which replaces Ni2+ (0.078 nm). Bulk density and porosity measurements show that there are pores and lattice imperfections. The cation distribution of the ferrites based on Neel's two sublattice model is proposed. Transmission Electron Micrographs (TEM) indicate narrow size distribution of spherical shaped nanoparticles. DC electrical resistivity (ρD.C.) is very important factor of low temperature sintered ferrites for MLCI applications. Electroplating of the devices is much affected by electrical resistivity. Maximum DC resistivity (2.89 × 106 Ω-cm) is observed for the sample with x=0.20. The dielectric parameters (ɛ', ɛ″ and tan δ) decrease as the alternating field increases which is due to space charge distribution and hopping mechanism. AC resistivity (ρAC) decreases with frequency, increased concentration of Fe2+ ions induces electron hopping: Fe3+ ↔ Fe2+ at B sites thereby reducing the resistivity. The low dielectric loss factor of 0.07 for x=0.20 ferrite indicates that the sample can be potential candidate for MLCI applications.

The Development of Ni-Containing Cryogenic Steels and Their Industrial Manufacturing

NASA Astrophysics Data System (ADS)

Wang, Meng; Xie, Zhang-long; Li, Cheng-gang; Liu, Zheng-yu

China has become one the largest energy consumer in the world due to the rapid growth of its economy, leading to the steady increase in the consumption of LPG, LEG and LNG in recent years. Therefore, urgent demands for the steels to be able to contain liquefied gases had emerged. Nickel containing cryogenic steels had been mainly used for liquefied gas tanks as ferritic cryogenic materials, but there are still many problems in regard of industrial production. In the present work, the optimized processing routes for 5Ni and 9Ni steels were developed at laboratory. The effect of Ni addition on the microstructure and cryogenic toughness of Ni containing steels was investigated. The results showed that the prior austenite grain size decreased from 19.8µm to 18.2µm and the ductile-brittle transition temperature decreased as Ni content increased from 5% to 9%. The quenched and tempered microstructures in 5Ni and 9Ni steels were consisted of tempered martensite and small amount of reversed austenite, with the microstructure of 5Ni steel only containing only 0.3%reversed austenite and a large amount of dispersive cementite was precipitated on ferritic matrix. With the increase of Ni addition up to 9%, the volume fraction of reversed austenite increased to about 5% and cementite precipitation was eliminated because the reversed austenite had absorbed carbon atoms from the matrix. It has been shown that cementite was harmful to the toughness of the steelas a hard second phase because it was easy for cracks' initiation and propagation when the cementite was precipitated at grain boundaries or lath boundaries. Fine grain size, more reversed austenite and less cementite precipitation are worked out to be the key factors to decrease the ductile-brittle transition temperature of 9Ni steel.

Effect of neodymium substitutions on electromagnetic properties in low temperature sintered NiCuZn ferrite

NASA Astrophysics Data System (ADS)

Wu, C. P.; Tung, M. J.; Ko, W. S.; Wang, Y. P.; Tong, S. Y.; Yang, M. D.

2015-11-01

Nd3+ ions substituted Ni0.37Cu0.14Zn0.52Fe2O4 (Nd3+ ions content=0, 0.01, 0.04, 0.6, 1.5 wt%) were prepared by the usual standard ceramic method at 1030 °C sintering temperature, and the composition dependence of the physical and magnetic properties has been investigated. SEM micrographs and EDX analysis revealed that it is no obvious impurities up to Nd3+ ions content wt%=0.04. For higher Nd3+ ions content samples (0.6 and 1.5 wt%), there are two kind of impurities Cu-rich and Nd-rich iron oxide phase. The saturation magnetization of the 0.01 wt% Nd3+ions content sample is higher as result of that the A-B sites distance and YK-angles are shorter and smaller. The saturation magnetization of 0.04-1.5 wt% Nd3+ ion content sample are reduced, since the total magnetic moments of the AB site are decreased. For the 0.6 wt% sample, the Curie temperature increasing is as result of the Cu-rich iron oxide separating out. The maximum enhancements of permeability μ‧ are improved to 11.2% (0.04 wt%) and 29.2% (0.6 wt%) at the 6.7 and 13.8 MHz, respectively. However, it is notice that small amount substitutions of Nd3+ increase the high frequency electromagnetic characteristics, can be applied to NFC technology and WPT technologies.

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides

PubMed Central

Tseng, Kuang-Hung; Lin, Po-Yu

2014-01-01

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO2 leads to a satisfactory surface appearance compared to that of the TIG weld made with Al2O3. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO2, the TIG welding with nanoparticle SiO2 has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al2O3 does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO2 uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al2O3 results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides. PMID:28788704

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides.

PubMed

Tseng, Kuang-Hung; Lin, Po-Yu

2014-06-20

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO₂ and Al₂O₃ were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO₂ leads to a satisfactory surface appearance compared to that of the TIG weld made with Al₂O₃. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO₂, the TIG welding with nanoparticle SiO₂ has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al₂O₃ does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO₂ uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al₂O₃ results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides.

A Study of the Microstructural Basis for the Strength and Toughness Properties of Water-Quenched and Air-Cooled HSLA-100, HSLA-100 with Increased Copper, and a ULCB Steel

DTIC Science & Technology

1991-09-01

martensite . Howell reported previously the presence of polygonal ferrite and copper precipitates in... copper precipitates were found throughout the acicular ferrite and martensite laths; most frequently decorating dislocations. The precipitates congregated...evidently precipitate out into the transformation products; resulting in the observed e- copper precipitates . These small, ductile particles lead

Effect of 120 MeV 28Si9+ ion irradiation on structural and magnetic properties of NiFe2O4 and Ni0.5Zn0.5Fe2O4

NASA Astrophysics Data System (ADS)

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

2018-05-01

NiFe2O4, Ni0.5Zn0.5Fe2O4 samples were synthesized using sol-gel auto combustion method, and irradiated by using 120 MeV 28Si9+ ion with ion fluence of 1×1012 ions/cm2. Characterization of pristine, irradiated samples were done using X-Ray Diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX) and Vibrating Sample Magnetometer (VSM). XRD validates the single phase nature of pristine, irradiated Ni- Zn nano ferrite except for Ni ferrite (pristine, irradiated) where secondary phases of α-Fe2O3 and Ni is observed. FE- SEM images of pristine Ni, Ni-Zn ferrite show inhomogeneous nano-range particle size distribution. Presence of diamagnetic ion (Zn2+) in NiFe2O4 increases oxygen positional parameter (u 4¯3m ), experimental, theoretical saturation magnetization (Msexp., Msth.), while decreases the grain size (Ds) and coercivity (Hc). With irradiation Msexp., Msth. increases but not much change are observed in Hc. New antistructure modeling for the pristine, irradiated Ni and Ni-Zn ferrite samples was used for describing the surface active centers.

Yttria-Stabilized Zirconia Ceramic Deposition on SS430 Ferritic Steel Grown by PLD - Pulsed Laser Deposition Method

NASA Astrophysics Data System (ADS)

Khalid Rivai, Abu; Mardiyanto; Agusutrisno; Suharyadi, Edi

2017-01-01

Development of high temperature materials are one of the key issues for the deployment of advanced nuclear reactors due to higher temperature operation. One of the candidate materials for that purpose is ceramic-coated ferritic steel that one of the functions is to be a thermal barrier coating (TBC). Thin films of YSZ (Ytrria-Stabilized Zirconia) ceramic have been deposited on a SS430 ferritic steel using Pulsed Laser Deposition (PLD) at Center For Science and Technology of Advanced Materials laboratory - National Nuclear Energy Agency of Indonesia (BATAN). The thin film was deposited with the chamber pressure range of 200-225 mTorr, the substrate temperature of 800oC, and the number of laser shots of 3×104, 6×104 and 9×104. Afterward, the samples were analyzed using Scanning Electron Microscope - Energy Dispersive X-ray Spectroscope (SEM-EDS), X-Ray Diffractometer (XRD), Atomic Force Microscope (AFM) and Vickers hardness tester. The results showed that the YSZ could homogeneously and sticky deposited on the surface of the ferritic steel. The surfaces were very smoothly formed with the surface roughness was in the range of 70 nm. Furthermore, thickness, composition of Zr4+ dan Y3+, the crystallinity, and hardness property was increased with the increasing the number of the shots.

Oriented nanometric aggregates of partially inverted zinc ferrite: One-step processing and tunable high-frequency magnetic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sai, Ranajit, E-mail: ranajit@ecei.tohoku.ac.jp; Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore; Endo, Yasushi

2015-05-07

In this work, it is demonstrated that the in situ growth of oriented nanometric aggregates of partially inverted zinc ferrite can potentially pave a way to alter and tune magnetocrystalline anisotropy that, in turn, dictates ferromagnetic resonance frequency (f{sub FMR}) by inducing strain due to aggregation. Furthermore, the influence of interparticle interaction on magnetic properties of the aggregates is investigated. Mono-dispersed zinc ferrite nanoparticles (<5 nm) with various degrees of aggregation were prepared through decomposition of metal-organic compounds of zinc (II) and iron (III) in an alcoholic solution under controlled microwave irradiation, below 200 °C. The nanocrystallites were found to possess highmore » degree of inversion (>0.5). With increasing order of aggregation in the samples, saturation magnetization (at 5 K) is found to decrease from 38 emu/g to 24 emu/g, while coercivity is found to increase gradually by up to 100% (525 Oe to 1040 Oe). Anisotropy-mediated shift of f{sub FMR} has also been measured and discussed. In essence, the result exhibits an easy way to control the magnetic characteristics of nanocrystalline zinc ferrite, boosted with significant degree of inversion, at GHz frequencies.« less

Effect of sintering on structure and magnetic properties of Mn-doped Zn ferrite

NASA Astrophysics Data System (ADS)

Farheen, Atiya; Singh, Rajender

2018-05-01

The Mn-doped zinc ferrites, MnxZn1-xFe2O4 (x= 0 and 0.1) were prepared using co-precipitation method. The as-prepared samples were sintered at different temperatures. The x-ray diffraction pattern for all the samples confirms single phase spinel structure with Fd-3m space group. The lattice parameters have been estimated using Rietveld fitting. The magnetic moment is found to increase with Mn-doping. The magnetization increases as the sintering temperature increases up to 1200°C. The as-prepared samples are super paramagnetic, while the sintered samples are ferrimagnetic in nature.

Controlling the size and magnetic properties of nano CoFe2O4 by microwave assisted co-precipitation method

NASA Astrophysics Data System (ADS)

Prabhakaran, T.; Mangalaraja, R. V.; Denardin, Juliano C.

2018-02-01

In this report, cobalt ferrite nanoparticles synthesized using microwave assisted co-precipitation method was reported. Efforts have been made to control the particles size, distribution, morphology and magnetic properties of cobalt ferrite nanoparticles by varying the concentration of NaOH solution and microwave irradiation time. It was observed that the rate of nucleation and crystal growth was influenced by the tuning parameters. In that way, the average crystallite size of single phase cobalt ferrite nanoparticles was controlled within 9-11 and 10-12 nm with an increase of base concentration and microwave irradiation time, respectively. A narrow size distribution of nearly spherical nanoparticles was achieved through the present procedure. A soft ferromagnetism at room temperature with the considerable saturation magnetization of 58.4 emu g-1 and coercivity of 262.7 Oe was obtained for the cobalt ferrites synthesized with 2.25 M of NaOH solution for 3 and 7 min of microwave irradiation time, respectively. The cobalt ferrite nanoparticles synthesized with a shorter reaction time of 3-7 min was found to be advantageous over other methods that involved conventional heating procedures and longer reaction time to achieve the better magnetic properties for the technological applications.

Dielectric and impedance study of praseodymium substituted Mg-based spinel ferrites

NASA Astrophysics Data System (ADS)

Farid, Hafiz Muhammad Tahir; Ahmad, Ishtiaq; Ali, Irshad; Ramay, Shahid M.; Mahmood, Asif; Murtaza, G.

2017-07-01

Spinel ferrites with nominal composition MgPryFe2-yO4 (y = 0.00, 0.025, 0.05, 0.075, 0.10) were prepared by sol-gel method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The dielectric properties of all the samples as a function of frequency (1 MHz-3 GHz) were measured at room temperature. The dielectric constant and complex dielectric constant of these samples decreased with the increase of praseodymium concentration. In the present spinel ferrite, Cole-Cole plots were used to separate the grain and grain boundary's effects. The substitution of praseodymium ions in Mg-based spinel ferrites leads to a remarkable rise of grain boundary's resistance as compared to the grain's resistance. As both AC conductivity and Cole-Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. AC activation energy was lower than dc activation energy. Temperature dependence normalized AC susceptibility of spinel ferrites reveals that MgFe2O4 exhibits multi domain (MD) structure with high Curie temperature while on substitution of praseodymium, MD to SD transitions occurs. The low values of conductivity and low dielectric loss make these materials best candidate for high frequency application.

Magnetic and dielectric behavior of chromium substituted Co-Mg ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Jadoun, Priya; Jyoti, Prashant, B. L.; Dolia, S. N.; Bhatnagar, D.; Saxena, V. K.

2016-05-01

The chromium doped Co-Mg ferrite with composition Co0.5Mg0.5Cr0.2Fe1.8O4 has been synthesized using sol-gel auto combustion method. The crystal structure has been analyzed by X-ray diffraction (XRD) technique. XRD pattern reveals the formation of single phase cubic spinel structure. The magnetic measurements show ferromagnetic behavior at room temperature and large coercivity is observed on cooling down the temperature to 20 K. Dielectric constant (ɛ') and dielectric loss tangent (tan δ) have been determined at room temperature as a function of frequency in the frequency range 75 kHz to 80 MHz. The decrease in dielectric constant with increasing frequency attributes to Maxwell Wagner model and conduction mechanism in ferrites.

Influence of metallic additives on manganese ferrites sintering

NASA Astrophysics Data System (ADS)

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.

Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

NASA Astrophysics Data System (ADS)

Wang, S. F.; Li, Q.; Zu, X. T.; Xiang, X.; Liu, W.; Li, S.

2016-12-01

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M2+ ion active sites were coordinated by -OH of the water molecules except for EDTA anions. The MFe2O4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe2O4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly.

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

NASA Astrophysics Data System (ADS)

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.

The role of processing route on the microstructure of 14YWT nanostructured ferritic alloy

NASA Astrophysics Data System (ADS)

Mazumder, B.; Parish, C. M.; Bei, H.; Miller, M. K.

2015-10-01

Nanostructured ferritic alloys have outstanding high temperature creep properties and enhanced tolerance to radiation damage over conventional ferritic alloys. To achieve these properties, NFAs are fabricated by mechanical alloying of metallic and yttria powders. Atom probe tomography has demonstrated that milling times of at least 40 h are required to produce a uniform distribution of solutes in the flakes. After milling and hot extrusion, the microstructure consists of α-Fe, high number densities of Ti-Y-O-vacancy-enriched nanoclusters, and coarse Y2Ti2O7 and Ti(O,C,N) precipitates on the grain boundaries. In contrast, the as-cast condition consists of α-Fe with 50-100 μm irregularly-shaped Y2Ti2O7 pyrochlore precipitates with smaller embedded precipitates with the Y3Al5O12 (yttrium-aluminum garnet) crystal structure indicating that this traditional processing route is not a viable approach to achieve the desired microstructure. The nano-hardnesses were also substantially different, i.e., 4 and 8 GPa for the as-cast and as-extruded conditions, respectively. These variances can be explained by the microstructural differences and the effects of the high vacancy content introduced by mechanical alloying, and the strong binding energy of vacancies with O, Ti, and Y atoms that retard diffusion.

Influence of Cu-Cr substitution on structural, morphological, electrical and magnetic properties of magnesium ferrite

NASA Astrophysics Data System (ADS)

Yonatan Mulushoa, S.; Murali, N.; Tulu Wegayehu, M.; Margarette, S. J.; Samatha, K.

2018-03-01

Cu-Cr substituted magnesium ferrite materials (Mg1 - xCuxCrxFe21 - xO4 with x = 0.0-0.7) have been synthesized by the solid state reaction method. XRD analysis revealed the prepared samples are cubic spinel with single phase face centered cubic. A significant decrease of ∼41.15 nm in particle size is noted in response to the increase in Cu-Cr substitution level. The room temperature resistivity increases gradually from 0.553 × 105 Ω cm (x = 0.0) to 0.105 × 108 Ω cm (x = 0.7). Temperature dependent DC-electrical resistivity of all the samples, exhibits semiconductor like behavior. Cu-Cr doped materials can be suitable to limit the eddy current losses. VSM result shows pure and doped magnesium ferrite particles show soft ferrimagnetic nature at room temperature. The saturation magnetization of the samples decreases initially from 34.5214 emu/g for x = 0.0 to 18.98 emu/g (x = 0.7). Saturation magnetization, remanence and coercivity are decreased with doping, which may be due to the increase in grain size.

Modification of the Structure of Low-Carbon Pipe Steel by Helical Rolling, and the Increase in Its Strength and Cold Resistance

NASA Astrophysics Data System (ADS)

Derevyagina, L. S.; Gordienko, A. I.; Pochivalov, Yu. I.; Smirnova, A. S.

2018-01-01

The paper reports the investigation results on the microstructure and mechanical properties of low-carbon pipe steel after helical rolling. The processing of the steel leads to the refinement of ferritic grains from 12 (for the coarse-grained state) to 5 μm, to the strengthening of ferrite by carbide particles, a decrease in the total fraction of perlite grains, a more uniform alternation of ferrite and perlite, and the formation of regions with bainitic structure. The mechanical properties of the steel have been determined in the conditions of static and dynamic loading in the range of test temperatures from +20 to-70°C. As a result of processing, the ultimate tensile strength increases (from 650 to 770 MPa at a rolling temperature from 920°C) and the viscoplastic properties at negative temperatures are improved significantly. The ductile-brittle transition temperature of the rolled steel decreases from-32 to-55°C and the impact toughness at the test temperature-40°C increases eight times compared to the initial state of the steel.

Superparamagnetic behavior of heat treated Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ferrite nanoparticles studied by Mössbauer spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srinivas, Ch., E-mail: srinivas.chintoju75@gmail.com; Prasad, S. A. V.; Singh, S. B.

2016-05-23

Nanoparticles of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ferrite have been synthesized by co-precipitation method. XRD and Mössbauer spectroscopic results of Mg{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} annealed at 200 °C, 500 °C and 800 °C are reported. It was observed that the crystallite size increases and the lattice parameter decreases with increase in annealing temperature. The observed decrease in lattice strain supports the increase in crystallite size. The Mössbauer spectra of the samples annealed at 200 °C and 500 °C exhibits superparamagnetic doublets whereas the Mössbauer spectrum of the sample annealed at 800 °C exhibits paramagnetic doublet along with weak sextetmore » of hyperfine interaction. The values of isomer shift resemble the presence of high spin iron ions. The studied ferrite nanoparticles are suitable for biomedical applications. The results are incorporated employing core-shell model and cation redistribution.« less

Alternate current magnetic property characterization of nonstoichiometric zinc ferrite nanocrystals for inductor fabrication via a solution based process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yun, Hongseok; Kim, Jungkwun; Allen, Mark G.

2016-03-21

We investigate the ac magnetic behavior of solution processable, non-stoichiometric zinc ferrite nanocrystals with a series of sizes and zinc concentrations. Nearly monodisperse Zn{sub x}Fe{sub 3−x}O{sub 4} nanocrystals (x = 0–0.25) with an average size ranging from 7.4 nm to 13.8 nm are synthesized by using a solvothermal method. All the nanocrystals are in a superparamagnetic state at 300 K, which is confirmed by Superconductive Quantum Interference Device magnetometry. Due to the doping of non-magnetic Zn{sup 2+} into A site of ferrite, the saturation magnetization of nanocrystals increases as the size and Zn concentration increases. The ac magnetic permeability measurements at radio frequencies reveal thatmore » the real part of the magnetic permeability of similarly sized ferrite nanocrystals can be enhanced by almost twofold as the Zn{sup 2+} doping level increases from 0 to 0.25. The integration of 12.3 nm Zn{sub 0.25}Fe{sub 2.75}O{sub 4} nanocrystals into a toroidal inductor and a solenoid inductor prepared via a simple solution cast process yields a higher quality factors than air core inductors with the same geometries up to 5 MHz and 9 MHz, respectively, which is in the regime of the switching frequencies for the advanced integrated power converters.« less

Unraveling the Effect of Thermomechanical Treatment on the Dissolution of Delta Ferrite in Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Rezayat, Mohammad; Mirzadeh, Hamed; Namdar, Masih; Parsa, Mohammad Habibi

2016-02-01

Considering the detrimental effects of delta ferrite stringers in austenitic stainless steels and the industrial considerations regarding energy consumption, investigating, and optimizing the kinetics of delta ferrite removal is of vital importance. In the current study, a model alloy prone to the formation of austenite/delta ferrite dual phase microstructure was subjected to thermomechanical treatment using the wedge rolling test aiming to dissolve delta ferrite. The effect of introducing lattice defects and occurrence of dynamic recrystallization (DRX) were investigated. It was revealed that pipe diffusion is responsible for delta ferrite removal during thermomechanical process, whereas when the DRX is dominant, the kinetics of delta ferrite dissolution tends toward that of the static homogenization treatment for delta ferrite removal that is based on the lattice diffusion of Cr and Ni in austenite. It was concluded that the optimum condition for dissolution of delta ferrite can be defined by the highest rolling temperature and strain in which DRX is not pronounced.

Effects of heat input on pitting corrosion in super duplex stainless steel weld metals

NASA Astrophysics Data System (ADS)

Shin, Yong taek; Shin, Hak soo; Lee, Hae woo

2012-12-01

Due to the difference in reheating effects depending on the heat input of subsequent weld passes, the microstructure of the weld metal varies between acicular type austenite and a mixture of polygonal type and grain boundary mixed austenite. These microstructural changes may affect the corrosion properties of duplex stainless steel welds. This result indicates that the pitting resistance of the weld can be strongly influenced by the morphology of the secondary austenite phase. In particular, the ferrite phase adjacent to the acicular type austenite phase shows a lower Pitting Resistance Equivalent (PRE) value of 25.3, due to its lower chromium and molybdenum contents, whereas the secondary austenite phase maintains a higher PRE value of more than 38. Therefore, it can be inferred that the pitting corrosion is mainly due to the formation of ferrite phase with a much lower PRE value.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

NASA Astrophysics Data System (ADS)

Sakthivel, T.; Vasudevan, M.; Laha, K.; Parameswaran, P.; Chandravathi, K. S.; Mathew, M. D.; Bhaduri, A. K.

2011-06-01

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160-280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower δ-ferrite content, alignment of columnar grain with δ-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

Atomic engineering of mixed ferrite and core-shell nanoparticles.

PubMed

Morrison, Shannon A; Cahill, Christopher L; Carpenter, Everett E; Calvin, Scott; Harris, Vincent G

2005-09-01

Nanoparticulate ferrites such as manganese zinc ferrite and nickel zinc ferrite hold great promise for advanced applications in power electronics. The use of these materials in current applications requires fine control over the nanoparticle size as well as size distribution to maximize their packing density. While there are several techniques for the synthesis of ferrite nanoparticles, reverse micelle techniques provide the greatest flexibility and control over size, crystallinity, and magnetic properties. Recipes for the synthesis of manganese zinc ferrite, nickel zinc ferrite, and an enhanced ferrite are presented along with analysis of the crystalline and magnetic properties. Comparisons are made on the quality of nanoparticles produced using different surfactant systems. The importance of various reaction conditions is explored with a discussion on the corresponding effects on the magnetic properties, particle morphology, stoichiometry, crystallinity, and phase purity.

Metal-ceramic joint assembly

DOEpatents

Li, Jian

2002-01-01

A metal-ceramic joint assembly in which a brazing alloy is situated between metallic and ceramic members. The metallic member is either an aluminum-containing stainless steel, a high chromium-content ferritic stainless steel or an iron nickel alloy with a corrosion protection coating. The brazing alloy, in turn, is either an Au-based or Ni-based alloy with a brazing temperature in the range of 9500 to 1200.degree. C.

In situ TEM study of G-phase precipitates under heavy ion irradiation in CF8 cast austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Wei-Ying; Li, Meimei; Zhang, Xuan

2015-09-01

Thermally-aged cast austenitic stainless steels (CASS) CF8 was irradiated with 1 MeV Kr ions at 300, 350 and 400°C to 1.88x10^15 ions/cm2 (~3 dpa) at the IVEM-Tandem Facility at the Argonne National Laboratory. Before irradiation, the distribution of G-phase precipitates in the ferrite showed strong spatial variations, and both their size and density were affected by the ferrite-austenite phase boundary and presence of M23C6 carbides. Under 300°C irradiation, in-situ TEM observation showed G-phase precipitates were relatively unchanged in the vicinity of the phase boundary M23C6 carbides, while the density of G-phase precipitates increased with increasing dose within the ferrite matrix.more » Coarsening of G-phase precipitates was observed in the vicinity of phase boundary M23C6 carbides at 350°C and 400°C.« less

Development of new generation reduced activation ferritic-martenstic steels for advanced fusion reactors

DOE PAGES

Tan, Lizhen; Snead, Lance Lewis; Katoh, Yutai

2016-05-26

International development of reduced activation ferritic-martensitic (RAFM) steels has focused on 9 wt percentage Cr, which primarily contain M 23C 6 (M = Cr-rich) and small amounts of MX (M = Ta/V, X = C/N) precipitates, not adequate to maintain strength and creep resistance above ~500 °C. To enable applications at higher temperatures for better thermal efficiency of fusion reactors, computational alloy thermodynamics coupled with strength modeling have been employed to explore a new generation RAFM steels. The new alloys are designed to significantly increase the amount of MX nanoprecipitates, which are manufacturable through standard and scalable industrial steelmaking methods.more » Preliminary experimental results of the developed new alloys demonstrated noticeably increased amount of MX, favoring significantly improved strength, creep resistance, and Charpy impact toughness as compared to current RAFM steels. Furthermore, the strength and creep resistance were comparable or approaching to the lower bound of, but impact toughness was noticeably superior to 9–20Cr oxide dispersion-strengthened ferritic alloys.« less

Surface enhancement of cold work tool steels by friction stir processing with a pinless tool

NASA Astrophysics Data System (ADS)

Costa, M. I.; Verdera, D.; Vieira, M. T.; Rodrigues, D. M.

2014-03-01

The microstructure and mechanical properties of enhanced tool steel (AISI D2) surfaces produced using a friction stir welding (FSW) related procedure, called friction stir processing (FSP), are analysed in this work. The surface of the tool steel samples was processed using a WC-Co pinless tool and varying processing conditions. Microstructural analysis revealed that meanwhile the original substrate structure consisted of a heterogeneous distribution of coarse carbides in a ferritic matrix, the transformed surfaces consisted of very small carbides, homogenously distributed in a ferrite- bainite- martensite matrix. The morphology of the surfaces, as well as its mechanical properties, evaluated by hardness and tensile testing, were found to vary with increasing tool rotation speed. Surface hardness was drastically increased, relative to the initial hardness of bulk steel. This was attributed to ferrite and carbide refinement, as well as to martensite formation during solid state processing. At the highest rotation rates, tool sliding during processing deeply compromised the characteristics of the processed surfaces.

Investigations on structural, optical and magnetic properties of Dy-doped zinc ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Vinosha, P. Annie; Deepapriya, S.; Rodney, John. D.; Das, S. Jerome

2018-04-01

A persuasive and thriftily feasible homogeneous co-precipitation route was adopted to fabricate dysprosium (Dy) doped zinc ferrite (Zn1-xDyxFe2O4)nanoparticles in order to examine their structural, optical and magnetic properties. Theas-synthesized Zn1-xDyxFe2O4 was studied for its momentous applications in photo-degradation of organic Methylene Blue (MB) dye. The paper marksthe connotation of zinc ferrite nanocatalyst in Photo-Fenton degradation. The chemical composition of dysprosium has a decisive feature of this research work. From X-ray diffraction analysis (XRD), spinel phase formation of theas-synthesized Zn1-xDyxFe2O4 nanoparticles was observedand the crystallite size was foundto increase as the doping concentration increased. Theabsorption bands peaked between 600-400 cm-l waspragmatic by Fourier Transform Infrared spectral analysis (FTIR). Transmission Electron Microscopy (TEM) micrograph elucidated the morphology and the speck size of as-synthesized nanoparticles. Surface area and pore size were determined by Brunauer-Emmett-Teller (BET) technique.

Synthesis and Characterization of Zirconium Substituted Cobalt Ferrite Nanopowders

DOE PAGES

Rus, S. F.; Vlazan, P.; Herklotz, A.

2016-01-01

Nanocrystalline ferrites; CoFe 2O 4 (CFO) and CoFe 1.9Zr 0.1O 4 (CFZO) have been synthesized through chemical coprecipitation method. Moreover, the role played by the zirconium ions in improving the magnetic and structural properties is analyzed. X-ray diffraction revealed a single-phase cubic spinel structure for both materials, where the crystallite size increases and the lattice parameter decreases with substitution of Zr. The average sizes of the nanoparticles are estimated to be 16-19 nm. These sizes are small enough to achieve the suitable signal to noise ratio in the high density recording media. An increase in the saturation magnetization with themore » substitution of Zr suggests the preferential occupation of Zr 4+ ions in the tetrahedral sites. A decrease in the coercivity values indicates the reduction of magneto-crystalline anisotropy. We investigated spinel ferrites can be used also in recoding media due to the large value of coercivity 1000 Oe which is comparable to those of hard magnetic materials.« less

In situ TEM study of G-phase precipitates under heavy ion irradiation in CF8 cast austenitic stainless steel

NASA Astrophysics Data System (ADS)

Chen, Wei-Ying; Li, Meimei; Zhang, Xuan; Kirk, Marquis A.; Baldo, Peter M.; Lian, Tiangan

2015-09-01

Thermally-aged cast austenitic stainless steels (CASS) CF8 was irradiated with 1 MeV Kr ions at 300, 350 and 400 °C to 1.88 × 1019 ions/m2 (∼3 dpa) at the IVEM-Tandem Facility at the Argonne National Laboratory. Before irradiation, the distribution of G-phase precipitates in the ferrite showed spatial variations, and both their size and density were affected by the ferrite-austenite phase boundary and presence of M23C6 carbides. Under 300 °C irradiation, in situ TEM observation showed G-phase precipitates were relatively unchanged in the vicinity of the phase boundary M23C6 carbides, while the density of G-phase precipitates increased with increasing dose within the ferrite matrix. Coarsening of G-phase precipitates was observed in the vicinity of phase boundary M23C6 carbides at 350 °C and 400 °C.

Cobalt ferrite based magnetostrictive materials for magnetic stress sensor and actuator applications

NASA Technical Reports Server (NTRS)

Jiles, David C. (Inventor); Paulsen, Jason A. (Inventor); Snyder, John E. (Inventor); Lo, Chester C. H. (Inventor); Ring, Andrew P. (Inventor); Bormann, Keith A. (Inventor)

2008-01-01

Magnetostrictive material based on cobalt ferrite is described. The cobalt ferrite is substituted with transition metals (such manganese (Mn), chromium (Cr), zinc (Zn) and copper (Cu) or mixtures thereof) by substituting the transition metals for iron or cobalt to form substituted cobalt ferrite that provides mechanical properties that make the substituted cobalt ferrite material effective for use as sensors and actuators. The substitution of transition metals lowers the Curie temperature of the material (as compared to cobalt ferrite) while maintaining a suitable magnetostriction for stress sensing applications.

Microstructure and partitioning behavior characteristics in low carbon steels treated by hot-rolling direct quenching and dynamical partitioning processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yun-jie; Li, Xiao-lei; Yuan, Guo, E-mail: yuan

2016-11-15

In this work, a new process and composition design are proposed for “quenching and partitioning” or Q&P treatment. Three low carbon steels were treated by hot-rolling direct quenching and dynamical partitioning processes (DQ&P). The effects of proeutectoid ferrite and carbon concentration on microstructure evolution and mechanical properties were investigated. The present work obtained DQ&P prototype steels with good mechanical properties and established a new notion on compositions for Q&P processing. Microstructures were characterized by means of electro probe microanalyzer (EPMA), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD), especially the morphology andmore » size of retained austenite. Mechanical properties were measured by uniaxial tensile tests. The results indicated that introducing proeutectoid ferrite can increase the volume fraction of retained austenite and thus improve mechanical properties. TEM observation showed that retained austenite included the film-like inter-lath austenite and blocky austenite located in martensite/ferrite interfaces or surrounded by ferrites. It was interesting that when the carbon concentration is as low as ~ 0.078%, the film-like inter-lath untransformed austenite cannot be stabilized to room temperature and almost all of them transformed into twin martensite. The blocky retained austenite strengthened the interfaces and transformed into twin martensite during the tensile deformation process. The PSEs of specimens all exceeded 20 GPa.%. - Highlights: •This study focused on a new process: Q&P process applying dynamical partitioning. •Ferrite can increase the volume fraction of retained austenite. •The film-like austenite and the blocky austenite were observed. •The low carbon steels treated by new process reached PSEs higher than 20 GPa.%.« less

Ferrite film growth on semiconductor substrates towards microwave and millimeter wave integrated circuits

NASA Astrophysics Data System (ADS)

Chen, Z.; Harris, V. G.

2012-10-01

It is widely recognized that as electronic systems' operating frequency shifts to microwave and millimeter wave bands, the integration of ferrite passive devices with semiconductor solid state active devices holds significant advantages in improved miniaturization, bandwidth, speed, power and production costs, among others. Traditionally, ferrites have been employed in discrete bulk form, despite attempts to integrate ferrite as films within microwave integrated circuits. Technical barriers remain centric to the incompatibility between ferrite and semiconductor materials and their processing protocols. In this review, we present past and present efforts at ferrite integration with semiconductor platforms with the aim to identify the most promising paths to realizing the complete integration of on-chip ferrite and semiconductor devices, assemblies and systems.

Physiological Remediation of Cobalt Ferrite Nanoparticles by Ferritin

NASA Astrophysics Data System (ADS)

Volatron, Jeanne; Kolosnjaj-Tabi, Jelena; Javed, Yasir; Vuong, Quoc Lam; Gossuin, Yves; Neveu, Sophie; Luciani, Nathalie; Hémadi, Miryana; Carn, Florent; Alloyeau, Damien; Gazeau, Florence

2017-01-01

Metallic nanoparticles have been increasingly suggested as prospective therapeutic nanoplatforms, yet their long-term fate and cellular processing in the body is poorly understood. Here we examined the role of an endogenous iron storage protein - namely the ferritin - in the remediation of biodegradable cobalt ferrite magnetic nanoparticles. Structural and elemental analysis of ferritins close to exogenous nanoparticles within spleens and livers of mice injected in vivo with cobalt ferrite nanoparticles, suggests the intracellular transfer of degradation-derived cobalt and iron, entrapped within endogenous protein cages. In addition, the capacity of ferritin cages to accommodate and store the degradation products of cobalt ferrite nanoparticles was investigated in vitro in the acidic environment mimicking the physiological conditions that are present within the lysosomes. The magnetic, colloidal and structural follow-up of nanoparticles and proteins in the lysosome-like medium confirmed the efficient remediation of nanoparticle-released cobalt and iron ions by ferritins in solution. Metal transfer into ferritins could represent a quintessential process in which biomolecules and homeostasis regulate the local degradation of nanoparticles and recycle their by-products.

Structural and electrical properties of nickel substituted cadmium ferrite

NASA Astrophysics Data System (ADS)

Chethan, B.; Raj Prakash, H. G.; Vijayakumari, S. C.; Ravikiran, Y. T.

2018-05-01

Spinal nano-sized Cadmium ferrite (CD) and Nickel substituted cadmium ferrite (NSCF) were fabricated by sol-gel auto combustion method. The formation of spinal structure of ferrite materials was confirmed by X-ray diffraction (XRD) analysis. The crystallites size of CF and NSCF as determined by Scherrer's formula were found to be 24.73 nm and 17.70 nm respectively. comparative study of Fourier transform infrared spectroscopy (FTIR) of CF and NSCF revealed tetrahedral absorption bands shifted slightly towards higher frequency where as octahedral bands shifted towards lower frequency side confirming interfacial interaction between Ni and CF. The AC conductivity (σ), loss tangent (tan δ) and complex plane impedance plots for both CF and NSCF are determined at various frequencies ranging from 50 kHz to 5 MHz and comparatively analyzed. The increase in AC conductivity of the NSCF nano particles as compared to CF was explained in the light of hopping model. The impedance measurement of NSCF show presence of a semi-circle corresponding to the grain boundary resistance and hence shows that the conductivity takes place largely through grain boundaries.

Crystal structure and mechanical strain in polycrystalline ferrite films on polycrystalline sapphire substrates

NASA Astrophysics Data System (ADS)

Bogdanovich, M. P.

1996-10-01

We have grown films of magnesium, lithium, zinc, and nickel-zinc ferrites, varying in thickness from 0.5 to 8 μm on polycrystalline sapphiresubstrates by coating the surface of the substrate with an aqueous nitric acid solution of salts of the elements which compose the ferrite. The lattice parameter of the ferrite film increases with the film thickness and becomes constant at thicknesses greater than 8 μm. We have determined the ratio of the theoretical strength limit to the macroscopic one in the film based on the change in the interplanar distance d 220 and the lattice parameter calculated from it, under the assumption that the change Δa(h)=a ∞=a(h) results from macroscopic stresses in the film. This ratio shows that when h=1 μm the microstresses in the film are an order of magnitude smaller than the theoretical strength limit. At larger film thicknesses this macroscopic stress becomes even lower, and at the external surface of thick films it goes completely to zero.

Magneto Tuning of a Ferrite Dielectric Resonator Antenna Based on LiFe5O8 Matrix

NASA Astrophysics Data System (ADS)

de Morais, J. E. V.; de Castro, A. J. N.; Oliveira, R. G. M.; do Carmo, F. F.; Sales, A. J. M.; Sales, J. C.; Silva, M. A. S.; Gouveia, D. X.; Costa, M. M.; Rodrigues, A. R.; Sombra, A. S. B.

2018-04-01

LiFe5O8 (LFO) spinel-like material has been studied for use in ferrite resonator antennas (FRAs). Antenna parameters such as gain and return loss were greatly affected when an external magnetic field was applied to the FRA. The temperature coefficient of the resonant frequency (τ f ) for the FRA presented a value of - 482.16 ppm/°C. The magnetic hysteresis results showed that the LFO was a soft ferrite, considering the values of the remanent magnetization (M r = 5.95 emu g-1), coercive field (0.76 mT), and saturation magnetization (32.15 emu g-1). The magnetodielectric resonator presented a tuning effect in the resonant frequency as a function of the external magnetic field. The antenna bandwidth was also affected by the presence of the magnetic field. LFO is a soft ferrite with applications in microwave circuits, antennas, and devices for operation at microwave frequencies due to its magnetization and demagnetization properties. Impedance study revealed increasing conductivity from room to higher temperature with low activation energy (0.36 eV).

An investigation on microstructure and mechanical property of thermally aged stainless steel weld overlay cladding

NASA Astrophysics Data System (ADS)

Cao, X. Y.; Zhu, P.; Ding, X. F.; Lu, Y. H.; Shoji, T.

2017-04-01

Microstructural evolution and mechanical property change of E308L stainless steel weld overlay cladding aged at 400 °C for 400, 1000 and 5000 h were investigated by transmission electron microscope (TEM) and small punch test (SPT). The results indicated that thermal aging had no obvious effect on the volume fraction of ferrite, but can cause microstructural evolution by spinodal decomposotion and G-phase precipitation in the ferrite phase. Spinodal decomposition took place after aging up to 1000 h, while G-phase formed along dislocations, and growed up to 2-11 nm after aging for 5000 h. The total energy for inducing deformation and fracture by the small punch tests decreased with the increase of thermal aging time, and this decline was associated with spinodal decomposition and G-phase precipitation. Plastic deformation of the aged ferrite proceeded via formation of curvilinear slip bands. Nucleation of microcracks occurred at the δ/γ interface along the slip bands. The hardening of the ferrite and high stress concentration on δ/γ phase interface resulted in brittle fracture and phase boundary separation after thermal aging.

Physiological Remediation of Cobalt Ferrite Nanoparticles by Ferritin

PubMed Central

Volatron, Jeanne; Kolosnjaj-Tabi, Jelena; Javed, Yasir; Vuong, Quoc Lam; Gossuin, Yves; Neveu, Sophie; Luciani, Nathalie; Hémadi, Miryana; Carn, Florent; Alloyeau, Damien; Gazeau, Florence

2017-01-01

Metallic nanoparticles have been increasingly suggested as prospective therapeutic nanoplatforms, yet their long-term fate and cellular processing in the body is poorly understood. Here we examined the role of an endogenous iron storage protein – namely the ferritin – in the remediation of biodegradable cobalt ferrite magnetic nanoparticles. Structural and elemental analysis of ferritins close to exogenous nanoparticles within spleens and livers of mice injected in vivo with cobalt ferrite nanoparticles, suggests the intracellular transfer of degradation-derived cobalt and iron, entrapped within endogenous protein cages. In addition, the capacity of ferritin cages to accommodate and store the degradation products of cobalt ferrite nanoparticles was investigated in vitro in the acidic environment mimicking the physiological conditions that are present within the lysosomes. The magnetic, colloidal and structural follow-up of nanoparticles and proteins in the lysosome-like medium confirmed the efficient remediation of nanoparticle-released cobalt and iron ions by ferritins in solution. Metal transfer into ferritins could represent a quintessential process in which biomolecules and homeostasis regulate the local degradation of nanoparticles and recycle their by-products. PMID:28067263

Study of structural and magnetic properties of cobalt ferrite nanoparticles sintered at different temperature

NASA Astrophysics Data System (ADS)

Kumari, Mukesh; Bhatnagar, Mukesh Chander

2018-05-01

Cobalt ferrite (CFO) has been synthesized in the form of nanoparticles (NPs) through sol-gel auto-combustion method. The prepared NPs of CFO were sintered for four hours at various temperatures from 300°C to 900°C. The physical properties of the sintered samples have been optimized using X-ray diffraction (XRD), Raman spectroscopy and physical properties measurement system (PPMS). The XRD and Raman studies have confirmed the cubic spinel phase formation of CFO NPs. XRD results showed that as we increase the sintering temperature the crystallite size of particles increases. Whereas the magnetic studies revealed that the saturation magnetization (MS) increases while the coercivity (HC) of nanoparticles decreases with increase of sintering temperature.

Structural and magnetic properties of Ni-Zn and Ni-Zn-Co ferrites

NASA Astrophysics Data System (ADS)

Knyazev, A. V.; Zakharchuk, I.; Lähderanta, E.; Baidakov, K. V.; Knyazeva, S. S.; Ladenkov, I. V.

2017-08-01

Ni-Zn and Ni-Zn-Co ferrite powders with nominal compositions Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 were prepared by the solid-state reaction synthesis with periodic regrinding during the calcination at 1073 K. The structure of Ni0.5Zn0.5Fe2O4 and Ni0.5Zn0.3Co0.2Fe2O4 was refined assuming space group F d-3m. Scanning electron microscopy revealed the average sizes of the crystalline ferrite particles are 130-630 nm for Ni0.5Zn0.5Fe2O4 and 140-350 nm for Ni0.5Zn0.3Co0.2Fe2O4. The room temperature saturation magnetizations are 59.7 emu/g for Ni0.5Zn0.5Fe2O4 and 57.1 emu/g for Ni0.5Zn0.3Co0.2Fe2O4. The coercivity of the samples is found to be much larger than that of bulk ferrites and increases with Co introduction. The Curie temperature tends to increase upon Zn substitution by Co, as well. The temperature dependences of magnetization measured using zero-field cooled and field cooled protocols exhibit large spin frustration and spin-glass-like behavior.

Cation distribution in NiZn-ferrite films determined using x-ray absorption fine structure

NASA Astrophysics Data System (ADS)

Harris, V. G.; Koon, N. C.; Williams, C. M.; Zhang, Q.; Abe, M.

1996-04-01

We have applied extended x-ray absorption fine structure (EXAFS) spectroscopy to study the cation distribution in a series of spin-sprayed NiZn-ferrite films, Ni0.15ZnyFe2.85-yO4 (y=0.16, 0.23, 0.40, 0.60). The Ni, Zn, and Fe EXAFS were collected from each sample and analyzed to Fourier transforms. Samples of Ni-ferrite, Zn-ferrite, and magnetite were similarly studied as empirical standards. These standards, together with EXAFS data generated from the theoretical EXAFS FEFF codes, allowed the correlation of features in the Fourier transforms with specific lattice sites in the spinel unit cell. We find that the Ni ions reside mostly on the octahedral (B) sites whereas the Zn ions are predominantly on the tetrahedral (A) sites. The Fe ions reside on both A and B sites in a ratio determined by the ratio of Zn/Fe. The addition of Zn displaces a larger fraction of Fe cations onto the B sites serving to increase the net magnetization. The fraction of A site Ni ions is measured to increase peaking at ≊25% for y=0.6. At higher Zn concentrations (y≥0.5) the lattice experiences local distortions around the Zn sites causing a decrease in the superexchange resulting in a decrease in the net magnetization.

Synthesis, structural, dielectric and magnetic properties of polyol assisted copper ferrite nano particles

NASA Astrophysics Data System (ADS)

Pavithradevi, S.; Suriyanarayanan, N.; Boobalan, T.

2017-03-01

Nanocrystalline copper ferrite CuFe2O4 is synthesized by co-precipitation method in ethylene glycol as chelating agent, using sodium Hydroxide as precipitator at pH 8. The as synthesized CuFe2O4 is annealed at temperatures of 350 °C, 700 °C, and 1050 °C for 2 h respectively. The thermal analysis of the synthesized sample is done by TG technique. It is shown that at 260 °C ethylene glycol has evaporated completely and after 715 °C, spinel ferrite is formed with a cubic structure. The calculated lattice parameters are in agreement with the reported values. FTIR spectra of CuFe2O4 nano particles are as synthesized and annealed at 1050 °C and recorded between 400 cm-1 and 4000 cm-1. It shows that when the temperature increases ethylene glycol gradually evaporates. Finally, nano crystalline single phase spinel ferrite is obtained. X-ray diffraction (XRD) and electron diffraction (EDS) studies show that the sample is indexed as the face centered cubic spinel structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the particles are flaky and spherical with the crystallite size in the range of 25-34 nm. From the dielectric studies, the dielectric constant decreases as the frequency increases. Low value of dielectric loss at higher frequencies suggests that the material is suitable for high frequency applications. AC conductivity increases with frequency. The magnetic properties of the samples are measured using a vibrating sample magnetometer (VSM) at room temperature, which shows that the sample exhibited a typical super paramagnetic behavior at low temperature. The saturation magnetization, remanant magnetism, and coercivity increases with applied field.

Influence of Bi(3+)-doping on the magnetic and Mössbauer properties of spinel cobalt ferrite.

PubMed

Gore, Shyam K; Mane, Rajaram S; Naushad, Mu; Jadhav, Santosh S; Zate, Manohar K; Alothman, Z A; Hui, Biz K N

2015-04-14

The influence of Bi(3+)-doping on the magnetic and Mössbauer properties of cobalt ferrite (CoFe2O4), wherein the Fe(3+) ions are replaced by the Bi(3+) ions to form CoBixFe2-xO4 ferrites, where x = 0.0, 0.05, 0.1, 0.15 or 0.2, has been investigated. The structural and morphological properties of undoped and doped ferrites, synthesized chemically through a self-igniting sol-gel method, are initially screened using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy measurements. The changes in magnetic moment of ions, their coupling with neighboring ions and cation exchange interactions are confirmed from the Mössbauer spectroscopy analysis. The effect of Bi(3+)-doping on the magnetic properties of CoFe2O4 ferrite is examined from the vibrating sample magnetometry spectra. Saturation magnetization and coercivity values are increased initially and then decreased, as result of Bi(3+)-doping. The obtained results with improved saturation magnetization (from 26.36 to 44.96 emu g(-1)), coercivity (from 1457 to 1863 Oe) and remanence magnetization (from 14.48 to 24.63 emu g(-1)) on 0.1-0.15 mol Bi(3+)-doping of CoBixFe2-xO4 demonstrate the usefulness for magnetic recording and memory devices.

Growth, structure, morphology, and magnetic properties of Ni ferrite films

PubMed Central

2013-01-01

The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4. PMID:23622034

Growth, structure, morphology, and magnetic properties of Ni ferrite films.

PubMed

Dong, Chunhui; Wang, Gaoxue; Guo, Dangwei; Jiang, Changjun; Xue, Desheng

2013-04-27

The morphology, structure, and magnetic properties of nickel ferrite (NiFe2O4) films fabricated by radio frequency magnetron sputtering on Si(111) substrate have been investigated as functions of film thickness. Prepared films that have not undergone post-annealing show the better spinel crystal structure with increasing growth time. Meanwhile, the size of grain also increases, which induces the change of magnetic properties: saturation magnetization increased and coercivity increased at first and then decreased. Note that the sample of 10-nm thickness is the superparamagnetic property. Transmission electron microscopy displays that the film grew with a disorder structure at initial growth, then forms spinel crystal structure as its thickness increases, which is relative to lattice matching between substrate Si and NiFe2O4.

Influence of hydrogen on the corrosion behavior of stainless steels in lithium

NASA Astrophysics Data System (ADS)

Shulga, A. V.

2008-02-01

Corrosion behavior of several stainless steels in lithium and lithium with 0.05%H has been examined. Corrosion tests were performed under static conditions at 600 and 700 °C in the austenitic stainless steel of the type AISI 304 containers. Intensive formation of σ-phase of the composition Fe 50Cr 43Mo 3Ni 4 on the surface of austenitic stainless steels of the type AISI 316 at 700 °C for 1000 h was established as a result of isothermal mass transfer. Addition of 0.05%H in the form of LiH to lithium resulted in an increase in the quantity of the σ-phase. After corrosion tests of ferritic/martensitic steel in lithium at 700 °C for 1000 h the formation of the γ-phase was observed. In Li + 0.05%H besides the γ-phase was also formed the σ-phase. The features of decarburization of investigated stainless steels were examined using the direct method of activation autoradiography on carbon. Addition of 0.05%H in lithium significantly decreased the carbon content in the decarburization zone of austenitic stainless steel Fe-18Cr-15Ni-0.15C-0.23B without a noticeable change in the thickness of the decarburization zone. Decarburization of ferritic/martensitic stainless steel was less than of austenitic stainless steel using the same corrosion tests.

Effect of Adding Cerium on Microstructure and Morphology of Ce-Based Inclusions Formed in Low-Carbon Steel

PubMed Central

Adabavazeh, Z.; Hwang, W. S.; Su, Y. H.

2017-01-01

Intra-granular Acicular Ferrite (IAF), as one of the most well-known desirable microstructure of ferrite with a chaotic crystallographic orientation, can not only refine the microstructure and retard the propagation of cleavage crack but also provide excellent combination of strength and toughness in steel. The effect of adding cerium on microstructure and controlling proper cerium-based inclusions in order to improve properties in low-carbon commercial steel (SS400) were investigated. The type of inclusions can be controlled by changing S/O ratio and Ce content. Without Ce modification, MnS is a dominate inclusion. After adding Ce, the stable inclusion phases change from AlCeO3 to Ce2O2S. The optimum amount of cerium, 0.0235 wt.%, lead in proper grain refinement and formation of cerium oxide, oxy-sulfide and sulfide inclusions. Having a high amount of cerium results in increasing the number of inclusions significantly as a result it cannot be effective enough and the inclusions will act like barriers for others. It is found that the inclusions with a size of about 4∼7 μm can serve as heterogeneous nucleation sites for AF formation. Thermodynamic calculations have been applied to predict the inclusion formation in this molten steel as well, which show a good agreement with experimental one. PMID:28485376

Oxidation behavior and area specific resistance of La, Cu and B alloyed Fe-22Cr ferritic steels for solid oxide fuel cell interconnects

NASA Astrophysics Data System (ADS)

Swaminathan, Srinivasan; Ko, Yoon Seok; Lee, Young-Su; Kim, Dong-Ik

2017-11-01

Two Fe-22 wt% Cr ferritic stainless steels containing varying concentrations of La (0.14 or 0.52 wt%), Cu (0.17 or 1.74 wt%) and B (48 or 109 ppm) are investigated with respect to oxidation behavior and high temperature area specific resistance (ASR) of the surface oxide scales. To determine the oxidation resistance of developed steels, continuous isothermal oxidation is carried out at 800 °C in air, for 2000 h, and their thermally grown oxide scale is characterized using dynamic SIMS, SEM/EDX, XRD and GI-XRD techniques. To assess their electrical performance, the ASR measurement by four-point probe method is conducted at 800 °C in air, for 400 h. In higher La content steel, the La-oxides at the scale/alloy interface promotes the oxygen transport which resulted in sub-surface oxidation of Mn, Cr, Ti and Al. Moreover, the inward growth of oxides contributes to increase of Fe-Cr alloy protrusions within the scale, which reduced the ASR. In contrast, sub-surface oxidation is reduced in high Cu-alloyed steel by segregated Cu at the scale/alloy interface. Thus, addition of Cu is effective to oxidation resistance and also to better electrical performance. However, no obvious impact of B on the scale sequence and/or ASR is observed.

Corrosion behavior of magnetic ferrite coating prepared by plasma spraying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yi; Wei, Shicheng, E-mail: wsc33333@163.com; Tong, Hui

Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surfacemore » of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.« less

Effects of Thermal Aging on Material Properties, Stress Corrosion Cracking, and Fracture Toughness of AISI 316L Weld Metal

NASA Astrophysics Data System (ADS)

Lucas, Timothy; Forsström, Antti; Saukkonen, Tapio; Ballinger, Ronald; Hänninen, Hannu

2016-08-01

Thermal aging and consequent embrittlement of materials are ongoing issues in cast stainless steels, as well as duplex, and high-Cr ferritic stainless steels. Spinodal decomposition is largely responsible for the well-known "748 K (475 °C) embrittlement" that results in drastic reductions in ductility and toughness in these materials. This process is also operative in welds of either cast or wrought stainless steels where δ-ferrite is present. While the embrittlement can occur after several hundred hours of aging at 748 K (475 °C), the process is also operative at lower temperatures, at the 561 K (288 °C) operating temperature of a boiling water reactor (BWR), for example, where ductility reductions have been observed after several tens of thousands of hours of exposure. An experimental program was carried out in order to understand how spinodal decomposition may affect changes in material properties in Type 316L BWR piping weld metals. The study included material characterization, nanoindentation hardness, double-loop electrochemical potentiokinetic reactivation (DL-EPR), Charpy-V, tensile, SCC crack growth, and in situ fracture toughness testing as a function of δ-ferrite content, aging time, and temperature. SCC crack growth rates of Type 316L stainless steel weld metal under simulated BWR conditions showed an approximate 2 times increase in crack growth rate over that of the unaged as-welded material. In situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40 pct over the corresponding at-temperature air-tested values. Material characterization results suggest that spinodal decomposition is responsible for the degradation of material properties measured in air, and that degradation of the in situ properties may be a result of hydrogen absorbed during exposure to the high-temperature water environment.

Development of a monolithic ferrite memory array

NASA Technical Reports Server (NTRS)

Heckler, C. H., Jr.; Bhiwandker, N. C.

1972-01-01

The results of the development and testing of ferrite monolithic memory arrays are presented. This development required the synthesis of ferrite materials having special magnetic and physical characteristics and the development of special processes; (1) for making flexible sheets (laminae) of the ferrite composition, (2) for embedding conductors in ferrite, and (3) bonding ferrite laminae together to form a monolithic structure. Major problems encountered in each of these areas and their solutions are discussed. Twenty-two full-size arrays were fabricated and fired during the development of these processes. The majority of these arrays were tested for their memory characteristics as well as for their physical characteristics and the results are presented. The arrays produced during this program meet the essential goals and demonstrate the feasibility of fabricating monolithic ferrite memory arrays by the processes developed.

An experimental study of the local electronic structure of B-site gallium doped bismuth ferrite powders

NASA Astrophysics Data System (ADS)

Gholam, Turghunjan; Ablat, Abduleziz; Mamat, Mamatrishat; Wu, Rong; Aimidula, Aimierding; Bake, Muhammad Ali; Zheng, Lirong; Wang, Jiaou; Qian, Haijie; Wu, Rui; Ibrahim, Kurash

2017-08-01

The un-doped and gallium (Ga) doped multiferroic bismuth ferrite (BiFeO3) compounds were successfully synthesized by the hydrothermal technique. This is then followed by a series of detailed investigations into the influence of Ga doping on the structural, morphological, optical and magnetic properties of BiFe1 - xGaxO3 (0 ≤ x ≤ 0.15). X-ray diffraction (XRD) analyses reveal that B-site doping of Ga may lead to the transformation of its crystal structure from a rhombohedral with a space group of R3c to an orthorhombic with a space group of Pbnm phase. The scanning electron microscope (SEM) images show that doping with Ga causes a significant reduction in particle size, when compared to un-doped BiFeO3. X-ray absorption near-edge structure (XANES) spectra have also shown that as the substitution of Ga increases, the Fe K and Bi LIII-edge absorption spectra shift towards higher energy site. It also implies that doping of Ga affects the local structures of both Bi and Fe atoms. Distinct transmission band fluctuations, as shown by Fourier transform infrared (FT-IR) spectra, can provide significant evidence for a transformation in crystal structure, following the increase of Ga concentration. The magnetization hysteresis measurements show that the magnetization decreases when Ga content is x ≥ 0.05. Such a phenomenon mainly stems from the substitution of Fe for an excessive amount of Ga, resulting in reduction of both valence fluctuations and the magnetization in the BiFe1 - xGaxO3 system.

Novel technique to suppress hydrocarbon contamination for high accuracy determination of carbon content in steel by FE-EPMA

PubMed Central

Yamashita, Takako; Tanaka, Yuji; Yagoshi, Masayasu; Ishida, Kiyohito

2016-01-01

In multiphase steels, control of the carbon contents in the respective phases is the most important factor in alloy design for achieving high strength and high ductility. However, it is unusually difficult to determine the carbon contents in multiphase structures with high accuracy by electron probe microanalysis (EPMA) due to the unavoidable effect of hydrocarbon contamination during measurements. We have investigated new methods for suppressing hydrocarbon contamination during field emission (FE) EPMA measurements as well as a conventional liquid nitrogen trap. Plasma cleaner inside the specimen chamber results in a improvement of carbon-content determination by point analysis, increasing precision tenfold from the previous 0.1 mass%C to 0.01 mass%C. Stage heating at about 100 °C dramatically suppresses contamination growth during continuous point measurement and mapping. By the combination of above two techniques, we successfully visualized the two-dimensional carbon distribution in a dual-phase steel. It was also noted that the carbon concentrations at the ferrite/martensite interfaces were not the same across all interfaces, and local variation was observed. The developed technique is expected to be a powerful tool for understanding the mechanisms of mechanical properties and microstructural evolution, thereby contributing to the design of new steel products with superior properties. PMID:27431281

Advanced Microwave Ferrite Research (AMFeR): Phase Three

DTIC Science & Technology

2008-07-31

lApril 1, 2006 thru June 30, 2008 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Advanced Microwave Ferrite Research (AMFeR): Phase Three 5b. GRANT NUMBER...Advance Microwave Ferrite Research (AMFeR), Phase III project. The purpose of this research endeavor is to devise ferrite materials for microwave, self...biased circulator applications. The central task of the project is to fabricate ferrites that have a high magnetic saturation, high coercivity and low

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

NASA Astrophysics Data System (ADS)

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.

Experimental evidence for the magnetic moment directions of Cr2+ and Cr3+ cations in the spinel ferrites Cux1Crx2Fe3-x1-x2O4

NASA Astrophysics Data System (ADS)

Zhang, X. Y.; Xu, J.; Li, Z. Z.; Qi, W. H.; Tang, G. D.; Shang, Z. F.; Ji, D. H.; Lang, L. L.

2014-08-01

(A)[B]2O4 spinel ferrite samples with the composition Cux1Crx2Fe3-x1-x2O4 (0.0≤x1≤0.284 and 1.04≥x2≥0.656) were prepared by a chemical co-precipitation method. X-ray diffraction patterns indicated that the samples had a single-phase cubic spinel structure. It is interesting that the saturation magnetization of the samples increased when Cu2+ or Cu3+ (with 1 or 2μB of magnetic moment) substituted for Cr2+ or Cr3+ (with 4 or 3μB), which cannot be obviously explained if the magnetic moments of Cr2+ and Cr3+ cations are assumed to be parallel to those of the Fe and Cu cations. However, with the assumption that the magnetic moments of Cr2+ and Cr3+ cations are antiparallel to the Fe and Cu cation moments in spinel ferrites, the dependence on the Cu doping level of the sample magnetic moments at 10 K was fitted successfully, using the quantum-mechanical potential barrier model earlier proposed by our group. Using the cation distributions obtained in the fitting process, the experimental observation that the magnetic moment of the samples increased with increasing Cu doping level was explained. This work therefore provides experimental evidence that the magnetic moments of the Cr2+ and Cr3+ cations are antiparallel to those of the Fe and Cu cations in spinel ferrites.

Influence of cold isostatic pressing on the magnetic properties of Ni-Zn-Cu ferrite

NASA Astrophysics Data System (ADS)

Le, Trong Trung; Valdez-Nava, Zarel; Lebey, Thierry; Mazaleyrat, Frédéric

2018-04-01

In power electronics, there is the need to develop solutions to increase the power density of converters. Interleaved multicellular transformers allow interleaving many switching cells and, as a result, a possible increase in the power density. This converter is often composed of a magnetic core having the function of an intercell transformer (ICT) and, depending on the complexity of the designed architecture, its shape could be extremely complex. The switching frequencies (1-10 MHz) for the new wide band gap semiconductors (SiC, GaN) allow to interleave switching cell at higher frequencies than silicon-based semiconductors (<1 MHz). Intercell transformers must follow this increase in frequency times-fold the number of switching cells. Current applications for ICT transformers use Mn-Zn based materials, but their limit in frequency drive raises the need of higher frequency magnetic materials, such Ni-Zn ferrites. These materials can operate in medium and high power converters up to 10 MHz. We propose to use Ni0,30Zn0,57Cu0,15Fe2O4 ferrite and to compress it by cold isostatic pressing (CIP) into a a green ceramic block and to machine it to obtain the desired ICT of complex shape prior sintering. We compare the magnetic permeability spectra and hysteresis loops the CIP and uniaxially pressed ferrites. The effect of temperature and sintering time as well as high-pressure on properties will be presented in detail. The magnetic properties of the sintered cores are strongly dependent on the microstructure obtained.

Comparative cytotoxic response of nickel ferrite nanoparticles in human liver HepG2 and breast MFC-7 cancer cells.

PubMed

Ahamed, Maqusood; Akhtar, Mohd Javed; Alhadlaq, Hisham A; Khan, M A Majeed; Alrokayan, Salman A

2015-09-01

Nickel ferrite nanoparticles (NPs) have received much attention for their potential applications in biomedical fields such as magnetic resonance imaging, drug delivery and cancer hyperthermia. However, little is known about the toxicity of nickel ferrite NPs at the cellular and molecular levels. In this study, we investigated the cytotoxic responses of nickel ferrite NPs in two different types of human cells (i.e., liver HepG2 and breast MCF-7). Nickel ferrite NPs induced dose-dependent cytotoxicity in both types of cells, which was demonstrated by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT), neutral red uptake (NRU) and lactate dehydrogenase (LDH) assays. Nickel ferrite NPs were also found to induce oxidative stress, which was evident by the depletion of glutathione and the induction of reactive oxygen species (ROS) and lipid peroxidation. The mitochondrial membrane potential due to nickel ferrite NP exposure was also observed. The mRNA levels for the tumor suppressor gene p53 and the apoptotic genes bax, CASP3 and CASP9 were up-regulated, while the anti-apoptotic gene bcl-2 was down-regulated following nickel ferrite NP exposure. Furthermore, the activities of apoptotic enzymes (caspase-3 and caspase-9) were also higher in both types of cells treated with nickel ferrite NPs. Cytotoxicity induced by nickel ferrite was efficiently prevented by N-acetyl cysteine (ROS scavenger) treatment, which suggested that oxidative stress might be one of the possible mechanisms of nickel ferrite NP toxicity. We also observed that MCF-7 cells were slightly more susceptible to nickel ferrite NP exposure than HepG2 cells. This study warrants further investigation to explore the potential mechanisms of different cytotoxic responses of nickel ferrite NPs in different cell lines. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biodiesel Production by Aspergillus niger Lipase Immobilized on Barium Ferrite Magnetic Nanoparticles

PubMed Central

El-Batal, Ahmed I.; Farrag, Ayman A.; Elsayed, Mohamed A.; El-Khawaga, Ahmed M.

2016-01-01

In this study, Aspergillus niger ADM110 fungi was gamma irradiated to produce lipase enzyme and then immobilized onto magnetic barium ferrite nanoparticles (BFN) for biodiesel production. BFN were prepared by the citrate sol-gel auto-combustion method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy with energy dispersive analysis of X-ray (SEM/EDAX) analysis. The activities of free and immobilized lipase were measured at various pH and temperature values. The results indicate that BFN–Lipase (5%) can be reused in biodiesel production without any treatment with 17% loss of activity after five cycles and 66% loss in activity in the sixth cycle. The optimum reaction conditions for biodiesel production from waste cooking oil (WCO) using lipase immobilized onto BFN as a catalyst were 45 °C, 4 h and 400 rpm. Acid values of WCO and fatty acid methyl esters (FAMEs) were 1.90 and 0.182 (mg KOH/g oil), respectively. The measured flash point, calorific value and cetane number were 188 °C, 43.1 MJ/Kg and 59.5, respectively. The cloud point (−3 °C), pour point (−9 °C), water content (0.091%) and sulfur content (0.050%), were estimated as well. PMID:28952576

Biodiesel Production by Aspergillus niger Lipase Immobilized on Barium Ferrite Magnetic Nanoparticles.

PubMed

El-Batal, Ahmed I; Farrag, Ayman A; Elsayed, Mohamed A; El-Khawaga, Ahmed M

2016-05-12

In this study, Aspergillus niger ADM110 fungi was gamma irradiated to produce lipase enzyme and then immobilized onto magnetic barium ferrite nanoparticles (BFN) for biodiesel production. BFN were prepared by the citrate sol-gel auto-combustion method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy with energy dispersive analysis of X-ray (SEM/EDAX) analysis. The activities of free and immobilized lipase were measured at various pH and temperature values. The results indicate that BFN-Lipase (5%) can be reused in biodiesel production without any treatment with 17% loss of activity after five cycles and 66% loss in activity in the sixth cycle. The optimum reaction conditions for biodiesel production from waste cooking oil (WCO) using lipase immobilized onto BFN as a catalyst were 45 °C, 4 h and 400 rpm. Acid values of WCO and fatty acid methyl esters (FAMEs) were 1.90 and 0.182 (mg KOH/g oil), respectively. The measured flash point, calorific value and cetane number were 188 °C, 43.1 MJ/Kg and 59.5, respectively. The cloud point (-3 °C), pour point (-9 °C), water content (0.091%) and sulfur content (0.050%), were estimated as well.

A high-voltage pulse transformer with a modular ferrite core

NASA Astrophysics Data System (ADS)

Liu, Z.; Winands, G. J. J.; Yan, K.; Pemen, A. J. M.; Van Heesch, E. J. M.

2008-01-01

A high ratio (winding ratio of 1:80) pulse transformer with a modular ferrite core was developed for a repetitive resonant charging system. The magnetic core is constructed from 68 small blocks of ferrites, glued together by epoxy resin. This allows a high degree of freedom in choosing core shape and size. Critical issues related to this modular design are the size tolerance of the individual ferrite blocks, the unavoidable air gap between the blocks, and the saturation of the core. To evaluate the swing of the flux density inside the core during the charging process, an equivalent circuit model was introduced. It was found that when a transformer is used in a resonant charging circuit, the minimal required volume of the magnetic material to keep the core unsaturated depends on the coupling coefficient of the transformer and is independent of the number of turns of the primary winding. Along the flux path, 17 small air gaps are present due to the inevitable joints between the ferrite blocks. The total air gap distance is about 0.67mm. The primary and secondary windings have 16 turns and 1280 turns, respectively, and the actually obtained ratio is about 1:75.4. A coupling coefficient of 99.6% was obtained. Experimental results are in good agreement with the model, and the modular ferrite core works well. Using this transformer, the high-voltage capacitors can be charged up to more than 70kV from a low-voltage capacitor with an initial charging voltage of about 965V. With 26.9J energy transfer, the increased flux density inside the core was about 0.23T, and the core remains unsaturated. The energy transfer efficiency from the primary to the secondary was around 92%.

Magnetic and High-Frequency Dielectric Parameters of Divalent Ion-Substituted W-Type Hexagonal Ferrites

NASA Astrophysics Data System (ADS)

Ali, Akbar; Grössinger, R.; Imran, Muhammad; Khan, M. Ajmal; Elahi, Asmat; Akhtar, Majid Niaz; Mustafa, Ghulam; Khan, Muhammad Azhar; Ullah, Hafeez; Murtaza, Ghulam; Ahmad, Mukhtar

2017-02-01

Polycrystalline W-type hexagonal ferrites with chemical formulae Ba0.5Sr0.5 Co2- x Me x Fe16O27 ( x = 0, 0.5, Me = Mn, Mg, Zn, Ni) have been prepared using sol-gel autocombustion. It has been reported in our earlier published work that all the samples exhibit a single-phase W-type hexagonal structure which was confirmed by x-ray diffraction (XRD) analysis. The values of bulk density lie in the range of 4.64-4.78 g/cm3 for all the samples which are quite high as compared to those for other types of hexaferrites. It was also observed that Zn-substituted ferrite reflects the highest (14.7 × 107 Ω-cm) whereas Mn-substituted ferrite has the lowest (11.3 × 107 Ω-cm) values of direct current (DC) electrical resistivity. The observed values of saturation magnetization ( M s) are found to be in the range of 62.01-68.7 emu/g depending upon the type of cation substitution into the hexagonal lattice. All the samples exhibit a typical soft magnetic character with low values of coercivity ( H c) that are in the range of 26-85 Oe. These ferrites may be promising materials for microwave absorbers due to their higher saturation magnetization and low coercivities. Both the dielectric constant and tangent loss decrease with increasing frequency in the lower frequency region and become constant in the higher frequency region. The much lower dielectric constant obtained in this study makes the investigated ferrites very useful for high-frequency applications, i.e. dielectric resonators and for camouflaging military targets such as ships, tanks and aircrafts, etc.

The effect of Mg dopants on magnetic and structural properties of iron oxide and zinc ferrite thin films

NASA Astrophysics Data System (ADS)

Saritaş, Sevda; Ceviz Sakar, Betul; Kundakci, Mutlu; Yildirim, Muhammet

2018-06-01

Iron oxide thin films have been obtained significant interest as a material that put forwards applications in photovoltaics, gas sensors, biosensors, optoelectronic and especially in spintronics. Iron oxide is one of the considerable interest due to its chemical and thermal stability. Metallic ion dopant influenced superexchange interactions and thus changed the structural, electrical and magnetic properties of the thin film. Mg dopped zinc ferrite (Mg:ZnxFe3-xO4) crystal was used to avoid the damage of Fe3O4 (magnetite) crystal instead of Zn2+ in this study. Because the radius of the Mg2+ ion in the A-site (tetrahedral) is almost equal to that of the replaced Fe3+ ion. Inverse-spinel structure in which oxygen ions (O2-) are arranged to form a face-centered cubic (FCC) lattice where there are two kinds of sublattices, namely, A-site and B-site (octahedral) interstitial sites and in which the super exchange interactions occur. In this study, to increase the saturation of magnetization (Ms) value for iron oxide, inverse-spinal ferrite materials have been prepared, in which the iron oxide was doped by multifarious divalent metallic elements including Zn and Mg. Triple and quaternary; iron oxide and zinc ferrite thin films with Mg metal dopants were grown by using Spray Pyrolysis (SP) technique. The structural, electrical and magnetic properties of Mg dopped iron oxide (Fe2O3) and zinc ferrite (ZnxFe3-xO4) thin films have been investigated. Vibrating Sample Magnetometer (VSM) technique was used to study for the magnetic properties. As a result, we can say that Mg dopped iron oxide thin film has huge diamagnetic and of Mg dopped zinc ferrite thin film has paramagnetic property at bigger magnetic field.

Sol gel method for synthesis of semiconducting ferrite and the study of FTIR, DTA, SEM and CV

NASA Astrophysics Data System (ADS)

Alva, Sagir; Hua, Tang Ing; Kalmar Nizar, Umar; Wahyudi, Haris; Sundari, Rita

2018-03-01

In this study, a sol gel method using citric acid as anionic surfactant is used for synthesis of magnesium ferrite. Calcinations of magnesium ferrite at temperature (300°C, 600°C and 800°C) have been conducted after sol gel process. Characterization study of the prepared magnesium ferrite related to calcinations using Fourier transform infrared spectrometry (FTIR), Differential thermogravic analysis (DTA), and Scanning electron microscope (SEM) has been discussed. The study of Cyclic voltammetry (CV) of the prepared magnesium ferrite has been examined to assay the semiconducting behavior of magnesium ferrite in relation to its electrochemical behavior.

TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tosten, M; Michael Morgan, M

2008-12-12

A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similarmore » in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.« less

Investigation of Microwave Monolithic Integrated Circuit (MMIC) Non-Reciprocal Millimeterwave Components

DTIC Science & Technology

1991-09-01

nickel zinc ferrite films and (2) sputtering of barium hexaferrites with C-axis oriented normally to the film plane. The SSP tech- nique potential for...M-Wave, Components, Ferrites, Films , Yig, Nickel, Zinc , Hexagonal, R96E Measurements, Frequency, Magnetic, Barium Ferrite 17. SECURITY CLASSIFICATION...techniques to integrate millimeter-wave ferrite devices with GaAs VI&Cs. APPROACH Our approach was to deposit ferrite thin films on GaAs sub- strates in a

Soft ferrite cores characterization for integrated micro-inductors

NASA Astrophysics Data System (ADS)

Nguyen, Yen Mai; Lopez, Thomas; Laur, Jean-Pierre; Bourrier, David; Charlot, Samuel; Valdez-Nava, Zarel; Bley, Vincent; Combettes, Céline; Brunet, Magali

2013-12-01

Ferrite-based micro-inductors are proposed for hybrid integration on silicon for low-power medium frequency DC-DC converters. Due to their small coercive field and their high resistivity, soft ferrites are good candidates for a magnetic core working at moderate frequencies in the range of 5-10 MHz. We have studied several soft ferrites including commercial ferrite film and U70 and U200 homemade ferrites. The inductors are fabricated at wafer level using micromachining and assembling techniques. The proposed process is based on a sintered ferrite core placed in between thick electroplated copper windings. The low profile ferrite cores of 1.2 × 2.6 × 0.2 mm3 are produced by two methods from green tape-casted films and ferrite powder. This paper presents the magnetic characterization of the sintered ferrite films cut and printed in rectangular shape and sintered at different temperatures. The comparison is made in order to find out the best material for the core that can reach the required inductance (470 nH at 6 MHz) under 0.6A current DC bias and that generate the smallest losses. An inductance density of 285 nH/ mm2 up to 6 MHz was obtained for ESL 40011 cores that is much higher than the previously reported devices. The small size of our devices is also a prominent point.

High-temperature steam oxidation testing of select advanced replacement alloys for potential core internals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Lizhen; Pint, Bruce A.

2017-05-19

Coupons from a total of fourteen commercial and custom fabricated alloys were exposed to 1 bar full steam with ~10 ppb oxygen content at 600 and 650°C. The coupons were weighed at 500-h intervals with a total exposure time of 5,000 h. The fourteen alloys are candidate alloys selected under the ARRM program, which include three ferritic steels (Grade 92, 439, and 14YWT), three austenitic stainless steels (316L, 310, and 800), seven Ni-base superalloys (X750, 725, C22, 690, 625, 625 direct-aging, and 625- plus), and one Zr-alloy (Zr–2.5Nb). Among the alloys, 316L and X750 are served as reference alloys formore » low- and high-strength alloys, respectively. The candidate Ni-base superalloy 718 was procured too late to be included in the tests. The corrosion rates of the candidate alloys can be approximately interpreted by their Cr, Ni and Fe content. The corrosion rate was significantly reduced with increasing Cr content and when Ni content is above ~15 wt%, but not much further reduced when Fe content is less than ~55 wt%. Simplified thermodynamics analyses of the alloy oxidation provided reasonable indications for the constituents of oxide scales formed on the alloys and explanations for the porosity and exfoliation phenomena because of the nature of specific types of oxides.« less

Preparation of high-permeability NiCuZn ferrite.

PubMed

Hu, Jun; Yan, Mi

2005-06-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 degrees C to 930 degrees C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 degrees C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 degrees C because the microstructure of the NiZn ferrite sintered at 930 degrees C is more uniform and compact than that of the NiZn ferrite sintered at 1200 degrees C. The high permeability of 1700 and relative loss coefficient tandelta/mu(i) of 9.0x10(-6) at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite.

Magnetic properties of Ni-Cu-Mn ferrite system

NASA Astrophysics Data System (ADS)

Roumaih, Kh.

2011-10-01

Three groups according to the substitution of Cu 2+ and Mn 3+ in the system Ni 1-xCu xFe 2-yMn yO 4 ferrite with x = 0.2, 0.5, 0.8, and y varying from 0.0 to 1.0 in steps of 0.25 are prepared by solid state reactions. The phases of the Ni 1-xCu xFe 2-yMn yO 4 ferrite have been confirmed by X-ray diffraction (XRD). The results demonstrate that all of the synthesized materials are spinel with cubic unit cell and the lattice constant increased with increases of the Cu and Mn ions for all samples. The hyperfine interaction was studied by the Mössbauer spectroscopy at room temperature for all samples. The spectra of all samples show two well-resolved Zeeman patterns corresponding to A- and B-sites. The hyperfine field decreases with increasing Cu and Mn ions concentration. The Curie temperature, TC, was calculated from the temperature dependence of magnetization curves. The hysteresis curve recorded at room temperature shows that the samples are ferrimagnetic materials. The cation distribution was estimated from the results of Mössbauer spectroscopy and magnetic measurements.

Characterization and frequency-thermal response of electrical properties of Cu nanoferrite prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Moghadasi, Fatemeh S.; Daadmehr, Vahid; Kashfi, Monire

2016-10-01

In this paper, we have synthesized copper ferrite nanocrystals using sol-gel method. X-ray diffraction (XRD) analysis confirms that the ferrite has cubic spinal structure and shows Jahn-Teller effect. Also, scan electron microscope (SEM) image demonstrates that grains are nano size order. We showed that the dielectric properties are compatible with the Maxwell-Wagner model and phenomenological Koop's theory. Loss tangent and conductivity of the ferrite have been measured to have small values of 2.4 and 2×10-7 S/m, respectively at room temperature and at 12 Hz. Conductivity has been investigated in terms of localized hopping mechanism and good obedience of Jonscher's law was observed. Variation of activation energy was studied and showed a transition temperature of 443 °K. The electrical modulus shows relaxation of interfacial polarization with relaxation time of 0.318 ms at 24 °C and 15.9 μs at 72 °C. In Impedance spectroscopy, we observed the effects of grain and grain boundary. By increasing temperature, capacity and conduction would increase which show easier polarization process and a semiconducting behavior. Also, relaxation times are shifted to smaller values to represent increasing the electrons mobility.

Influence of carboxylic acid type on microstructure and magnetic properties of polymeric complex sol-gel driven NiFe2O4

NASA Astrophysics Data System (ADS)

Hessien, M. M.; Mostafa, Nasser Y.; Abd-Elkader, Omar H.

2016-01-01

Citric, oxalic and tartaric acids were used for synthesis of NiFe2O4 using polymeric complex precursor route. The dry precursor gels were calcined at various temperatures (400-1100 °C) for 2 h. All carboxylic acids produce iron-deficient NiFe2O4 with considerable amount of α-Fe2O3 at 400 °C. Increase in the annealing temperature caused reaction of α-Fe2O3 with iron-deficient ferrite phase. The amount of initially formed α-Fe2O3 is directly correlated with stability constant and inversely correlated with the decomposition temperature of Fe(III) carboxylate precursors. In case of tartaric acid precursor, single phase of the ferrite was obtained at 450 °C. However, in case of oxalic acid and citric acid precursors, single phase ferrite was obtained at 550 °C and 700 °C, respectively. The lattice parameters were increased with increasing annealing temperature and with decreasing the amount of α-Fe2O3. Maximum saturation magnetization (55 emu/g) was achieved using tartaric acid precursor annealed at 1100 °C.

New scheme for cation distribution and electrical characterization of nanocrystalline aluminum doped magnesium ferrite MgAlxFe2-xO4

NASA Astrophysics Data System (ADS)

Zaki, H. M.; Al-Heniti, S.; Al Shehri, N.

2014-03-01

MgAlxFe2-xO4 (x=0.0 up to 1 step 0.2) was prepared using co-precipitation method. The value of lattice constant is found to decrease with increasing Al3+ concentration. The particle size of the samples calculated using the Sherrer formula was obtained in the range of 15-28 nm. The two main bands corresponding to tetrahedral and octahedral sites were observed to be around 600 cm-1 and 450 cm-1, respectively. These bands are shifted to high frequencies with more doping of Al3+ ions which may be attributed to the decrease in the mean radius of the tetrahedral and octahedral sites. The threshold frequency (νth) for the electronic transition decreases with increasing the Al3+content. The tetrahedral force constant (KT) increases continuously with Al3+ concentration.The bandwidth of the tetrahedral site is found to increase gradually with the Al3+ content. The validity of the proposed cation distribution is confirmed by considering the X-ray intensity ratios of diffraction lines sensitive to the tetrahedral and octahedral sites. DC conductivity measurements exhibited metallic and semiconductor-like behavior with temperature for all compositions. The decrease of Curie temperature with the increase of non-magnetic ions of aluminum indicates their preference to the octahedral sites as well and confirms the validity of the cation distribution.

Internal hydrogen-induced subcritical crack growth in austenitic stainless steels

NASA Astrophysics Data System (ADS)

Huang, J. H.; Altstetter, C. J.

1991-11-01

The effects of small amounts of dissolved hydrogen on crack propagation were determined for two austenitic stainless steel alloys, AISI 301 and 310S. In order to have a uniform distribution of hydrogen in the alloys, they were cathodically charged at high temperature in a molten salt electrolyte. Sustained load tests were performed on fatigue precracked specimens in air at 0 ‡C, 25 ‡C, and 50 ‡C with hydrogen contents up to 41 wt ppm. The electrical potential drop method with optical calibration was used to continuously monitor the crack position. Log crack velocity vs stress intensity curves had definite thresholds for subcritical crack growth (SCG), but stage II was not always clearly delineated. In the unstable austenitic steel, AISI 301, the threshold stress intensity decreased with increasing hydrogen content or increasing temperature, but beyond about 10 wt ppm, it became insensitive to hydrogen concentration. At higher concentrations, stage II became less distinct. In the stable stainless steel, subcritical crack growth was observed only for a specimen containing 41 wt ppm hydrogen. Fractographic features were correlated with stress intensity, hydrogen content, and temperature. The fracture mode changed with temperature and hydrogen content. For unstable austenitic steel, low temperature and high hydrogen content favored intergranular fracture while microvoid coalescence dominated at a low hydrogen content. The interpretation of these phenomena is based on the tendency for stress-induced phase transformation, the different hydrogen diffusivity and solubility in ferrite and austenite, and outgassing from the crack tip. After comparing the embrittlement due to internal hydrogen with that in external hydrogen, it is concluded that the critical hydrogen distribution for the onset of subcritical crack growth is reached at a location that is very near the crack tip.

Magnetic and dielectric behavior of chromium substituted Co-Mg ferrite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jadoun, Priya, E-mail: priya4jadoun@gmail.com; Jyoti,; Prashant, B. L.

The chromium doped Co-Mg ferrite with composition Co{sub 0.5}Mg{sub 0.5}Cr{sub 0.2}Fe{sub 1.8}O{sub 4} has been synthesized using sol-gel auto combustion method. The crystal structure has been analyzed by X-ray diffraction (XRD) technique. XRD pattern reveals the formation of single phase cubic spinel structure. The magnetic measurements show ferromagnetic behavior at room temperature and large coercivity is observed on cooling down the temperature to 20 K. Dielectric constant (ε’) and dielectric loss tangent (tan δ) have been determined at room temperature as a function of frequency in the frequency range 75 kHz to 80 MHz. The decrease in dielectric constant with increasing frequency attributesmore » to Maxwell Wagner model and conduction mechanism in ferrites.« less

Synthesis, characterization and antistructure modeling of Ni nano ferrite

NASA Astrophysics Data System (ADS)

Kane, S. N.; Raghuvanshi, S.; Satalkar, M.; Reddy, V. R.; Deshpande, U. P.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

We report the role played by cation distribution in determining magnetic properties by comparing dry gel, thermally annealed Ni ferrite prepared by sol-gel auto-combustion technique. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Mössbauer spectroscopy were used to characterize the samples. Both XRD and Mössbauer measurements validate the formation of spinel phase with grain diameter 39.13-45.53 nm. First time antistructural modeling for Ni ferrite is reported to get information on active surface centers. Decrease of Debye temperature θD in annealed sample shows enhancement of lattice vibrations. With thermal annealing experimental and Néel magnetic moment (nBe, nBN) increases, suggesting migration of Ni2+ from B to A site with concurrent migration of Fe3+ from A to B site (non-equilibrium cationic distribution), affecting magnetic properties.

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

NASA Astrophysics Data System (ADS)

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.

Dielectric and magnetic behavior of nanocrystalline Cu{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4} ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jadoun, Priya, E-mail: priya4jadoun@gmail.com; Sharma, Jyoti; Prashant, B. L.

2016-05-23

The mixed copper cobalt ferrite nanoparticles (Cu{sub 0.4}Co{sub 0.6}Fe{sub 2}O{sub 4}) have been synthesized by sol-gel auto combustion route with aqueous metal nitrates and citric acid as the precursor. The crystal structure has been analyzed by X-Ray diffraction (XRD) method. XRD reveals the formation of single phase cubic spinel structure. The Scanning Electron Microscopy (SEM) is used for morphological studies. The dielectric measurements at room temperature show the decrease in dielectric constant with increasing frequency which is attributed to Maxwell Wagner model and conduction mechanism in ferrites.The magnetic measurements show ferromagnetic behavior at room temperature and large coercivity is observedmore » on cooling down the temperature to 20 K.« less

Atmosphere

NASA Astrophysics Data System (ADS)

Ghosh, D.; Mitra, S. K.

2014-05-01

This paper investigates the high-temperature corrosion behavior of microstructurally different regions of the weldment of 9 Cr-1 Mo steel used in thermal power plant boiler in SO2 + O2 environment. The weldment is produced by tungsten inert gas welding method, and the different regions of the weldment (weld metal, heat-affected zone, and base metal) are exposed in SO2 + O2 (ratio 2:1) environment at 973 K for 120 h. The reaction kinetics and corrosion growth rate of different regions of weldment in isothermal condition are evaluated. The post corroded scales of the different specimens are studied in SEM, EDS, and XRD. The results indicate that the weld metal shows higher corrosion rate followed by HAZ and base metal. The higher rate of corrosion of weldmetal is mainly attributed to the least protective inner scale of Cr2O3 with minimum Cr Content. This is due to the formation of delta ferrite, which leads to the precipitation of the Cr-based secondary phases and depletes the free Cr from the matrix. The thermal cycles during welding at high temperature are favorable for the formation of delta ferrite. On the other hand, in absence of delta ferrite, the base metal and HAZ regions of the weldment show lower corrosion rate than weld metal. The difference in corrosion rate in the three regions of the weldment is supplemented by post-corroded scale characterizations.

Effect of cooling after welding on microstructure and mechanical properties of 12 Pct Cr steel weld metals

NASA Astrophysics Data System (ADS)

Cai, Guang-Jun; Andrén, Hans-Olof; Svensson, Lars-Erik

1997-07-01

The microstructure of three 12 pct cr steel weld metals with different nickel and nitrogen contents was studied in as-welded condition and after postweld heat treatment with and without intercooling. Tensile strength and impact toughness of the weld metals were investigated in different postweld heat treatment conditions. In weld metals heat treated without intercooling, austenite decomposed by a eutectoid reaction that resulted in M23C6 aggregates around retained δ-ferrite. Two morphologies of M2N and MN precipitates were found in a low-dislocation α-ferrite. It was concluded that these phases were also transformed from austenite. In weld metals heat treated with intercooling, M23C6 precipitates were smaller and more homogeneously distributed. Different MN precipitates were found in the tempered martensite. The fracture mode of the weld metals at room temperature was mainly transgranular cleavage with some fibrous fracture. Intercooling treatment improved Charpy impact toughness of the 12 pct Cr steel weld metals substantially. It was found that the important microstructural factors affecting the impact toughness of the weld metals which were heat treated without intercooling were the sizes of the α-ferrite grains, nonmetallic inclusions, and M23C6 aggregates. For the weld metals heat treated with intercooling, the factors which affect the toughness of the weld metals were the sizes of martensite packets and nonmetallic inclusions.

A preliminary ferritic-martensitic stainless steel constitution diagram

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balmforth, M.C.; Lippold, J.C.

1998-01-01

This paper describes preliminary research to develop a constitution diagram that will more accurately predict the microstructure of ferritic and martensitic stainless steel weld deposits. A button melting technique was used to produce a wide range of compositions using mixtures of conventional ferritic and martensitic stainless steels, including types 403, 409, 410, 430, 439 and 444. These samples were prepared metallographically, and the vol-% ferrite and martensite was determined quantitatively. In addition, the hardness and ferrite number (FN) were measured. Using this data, a preliminary constitution diagram is proposed that provides a more accurate method for predicting the microstructures ofmore » arc welds in ferritic and martensitic stainless steels.« less

Preparation of high-permeability NiCuZn ferrite*

PubMed Central

Hu, Jun; Yan, Mi

2005-01-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 °C to 930 °C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 °C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 °C because the microstructure of the NiZn ferrite sintered at 930 °C is more uniform and compact than that of the NiZn ferrite sintered at 1200 °C. The high permeability of 1700 and relative loss coefficient tanδ/μi of 9.0×10−6 at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite. PMID:15909348

Effect of microstructural evolution by isothermal aging on the mechanical properties of 9Cr-1WVTa reduced activation ferritic/martensitic steels

NASA Astrophysics Data System (ADS)

Park, Min-Gu; Lee, Chang-Hoon; Moon, Joonoh; Park, Jun Young; Lee, Tae-Ho; Kang, Namhyun; Chan Kim, Hyoung

2017-03-01

The influence of microstructural changes caused by aging condition on tensile and Charpy impact properties was investigated for reduced activation ferritic-martensitic (RAFM) 9Cr-1WVTa steels having single martensite and a mixed microstructure of martensite and ferrite. For the mixed microstructure of martensite and ferrite, the Charpy impact properties deteriorated in both as-normalized and tempered conditions due to the ferrite and the accompanying M23C6 carbides at the ferrite grain boundaries which act as path and initiation sites for cleavage cracks, respectively. However, aging at 550 °C for 20-100 h recovered gradually the Charpy impact toughness without any distinct drop in strength, as a result of the spheroidization of the coarse M23C6 carbides at the ferrite grain boundaries, which makes crack initiation more difficult.

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

NASA Astrophysics Data System (ADS)

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 milling and analyzed for magnetic core loss dependence on particle size, cure temperature, and microstructure of both coating and core powder. We present a significant increase in core loss related to eddy current loss from coating particles sintering and Fe grain growth. Lastly, a more resistive coating material, NiZnCu-ferrite, is applied for improved resistivity, which leads to lower eddy current loss and improved magnetic performance. By highlighting the importance of microstructure and composition on magnetic properties, a closer look at interfacial features and local microstrain are necessary and accomplished in this work. Future developments of ferrite-based SMC coatings are required to transform the use of electromagnetic devices in today's society.

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

NASA Astrophysics Data System (ADS)

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 the modern electronics industry.

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... ferrite with acrylic ester polymer (generic). 721.10223 Section 721.10223 Protection of Environment... manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance and significant new uses... manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to reporting under this section for...

Microstructural Evolution During Cold Rolling and Subsequent Annealing in Low-Carbon Steel with Different Initial Microstructures

NASA Astrophysics Data System (ADS)

Ogawa, Toshio; Dannoshita, Hiroyuki; Maruoka, Kuniaki; Ushioda, Kohsaku

2017-08-01

Microstructural evolution during cold rolling and subsequent annealing of low-carbon steel with different initial microstructures was investigated from the perspective of the competitive phenomenon between recrystallization of ferrite and reverse phase transformation from ferrite to austenite. Three kinds of hot-rolled sheet specimens were prepared. Specimen P consisted of ferrite and pearlite, specimen B consisted of bainite, and specimen M consisted of martensite. The progress of recovery and recrystallization of ferrite during annealing was more rapid in specimen M than that in specimens P and B. In particular, the recrystallized ferrite grains in specimen M were fine and equiaxed. The progress of ferrite-to-austenite phase transformation during intercritical annealing was more rapid in specimen M than in specimens P and B. In all specimens, the austenite nucleation sites were mainly at high-angle grain boundaries, such as those between recrystallized ferrite grains. The austenite distribution was the most uniform in specimen M. Thus, we concluded that fine equiaxed recrystallized ferrite grains were formed in specimen M, leading to a uniform distribution of austenite.

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

NASA Astrophysics Data System (ADS)

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.

Phase stability in thermally-aged CASS CF8 under heavy ion irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Miller, Michael K.; Chen, Wei-Ying

2015-07-01

The stability of the microstructure of a cast austenitic stainless steel (CASS), before and after heavy ion irradiation, was investigated by atom probe tomography (APT). A CF8 ferrite–austenite duplex alloy was thermally aged at 400 °C for 10,000 h. After this treatment, APT revealed nanometer-sized G-phase precipitates and Fe-rich α and Cr-enriched α' phase separated regions in the ferrite. The thermally-aged CF8 specimen was irradiated with 1 MeV Kr ions to a fluence of 1.88 × 10 19 ions/m 2 at 400 °C. After irradiation, APT analysis revealed a strong spatial/dose dependence of the G-phase precipitates and the α–α' spinodalmore » decomposition in the ferrite. For the G-phase precipitates, the number density increased and the mean size decreased with increasing dose, and the particle size distribution changed considerably under irradiation. The inverse coarsening process can be described by recoil resolution. The amplitude of the α–α' spinodal decomposition in the ferrite was apparently reduced after heavy ion irradiation.« less

Characterization of grain boundary conductivity of spin-sprayed ferrites using scanning microwave microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, J.; Nicodemus, T.; Zhuang, Y., E-mail: yan.zhuang@wright.edu

2014-05-07

Grain boundary electrical conductivity of ferrite materials has been characterized using scanning microwave microscope. Structural, electrical, and magnetic properties of Fe{sub 3}O{sub 4} spin-sprayed thin films onto glass substrates for different length of growth times were investigated using a scanning microwave microscope, an atomic force microscope, a four-point probe measurement, and a made in house transmission line based magnetic permeameter. The real part of the magnetic permeability shows almost constant between 10 and 300 MHz. As the Fe{sub 3}O{sub 4} film thickness increases, the grain size becomes larger, leading to a higher DC conductivity. However, the loss in the Fe{sub 3}O{submore » 4} films at high frequency does not increase correspondingly. By measuring the reflection coefficient s{sub 11} from the scanning microwave microscope, it turns out that the grain boundaries of the Fe{sub 3}O{sub 4} films exhibit higher electric conductivity than the grains, which contributes loss at radio frequencies. This result will provide guidance for further improvement of low loss ferrite materials for high frequency applications.« less

Effect of Zn-doping on structural and magnetic properties of copper ferrite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gautam, Nisha; Thirupathi, Gadipelly; Singh, Rajender

2016-05-23

The nanoparticles of CuFe{sub 2}O{sub 4} (CF) and Cu{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (CZF) were synthesized using co-precipitation method to study the effect of Zn doping in Cu-ferrite. The X-ray diffraction (XRD) patterns were well fitted with two-phase structure using Rietveld analysis as Fd-3 m space group (spinel system) and C12/c1 space group (monoclinic system CuO-phase). The average crystallite size of the CF and CZF nanoparticles for spinel structure are 6 and 7 nm respectively. The spinel phase fraction is increased from 56% to 71% with Zn-doping of 20% in CF. The transmission electron micrograph analysis showed the narrow size distribution formore » CZF nanoparticles. The magnetization plots as a function of magnetic field (M (H)) of CF and CZF nanoparticles indicate superparamagnetic behavior. The magnetization is increased with Zn-doping in CF. The stable spinel Cu-ferrite can be obtained with Zn-doping in CF.« less

TEM Studies of Boron-Modified 17Cr-7Ni Precipitation-Hardenable Stainless Steel via Rapid Solidification Route

NASA Astrophysics Data System (ADS)

Gupta, Ankur; Bhargava, A. K.; Tewari, R.; Tiwari, A. N.

2013-09-01

Commercial grade 17Cr-7Ni precipitation-hardenable stainless steel has been modified by adding boron in the range 0.45 to 1.8 wt pct and using the chill block melt-spinning technique of rapid solidification (RS). Application of RS has been found to increase the solid solubility of boron and hardness of 17Cr-7Ni precipitation-hardenable stainless steel. The hardness of the boron-modified rapidly solidified alloys has been found to increase up to ~280 pct after isochronal aging to peak hardness. A TEM study has been carried out to understand the aging behavior. The presence of M23(B,C)6 and M2(B,C) borocarbides and epsilon-carbide in the matrix of austenite and ferrite with a change in heat treatment temperature has been observed. A new equation for Creq is also developed which includes the boron factor on ferrite phase stability. The study also emphasizes that aluminum only takes part in ferrite phase stabilization and remains in the solution.

Oxidative stress mediated apoptosis induced by nickel ferrite nanoparticles in cultured A549 cells.

PubMed

Ahamed, Maqusood; Akhtar, Mohd Javed; Siddiqui, Maqsood A; Ahmad, Javed; Musarrat, Javed; Al-Khedhairy, Abdulaziz A; AlSalhi, Mohamad S; Alrokayan, Salman A

2011-05-10

Due to the interesting magnetic and electrical properties with good chemical and thermal stabilities, nickel ferrite nanoparticles are being utilized in many applications including magnetic resonance imaging, drug delivery and hyperthermia. Recent studies have shown that nickel ferrite nanoparticles produce cytotoxicity in mammalian cells. However, there is very limited information concerning the toxicity of nickel ferrite nanoparticles at the cellular and molecular level. The aim of this study was to investigate the cytotoxicity, oxidative stress and apoptosis induction by well-characterized nickel ferrite nanoparticles (size 26 nm) in human lung epithelial (A549) cells. Nickel ferrite nanoparticles induced dose-dependent cytotoxicity in A549 cells demonstrated by MTT, NRU and LDH assays. Nickel ferrite nanoparticles were also found to induce oxidative stress evidenced by generation of reactive oxygen species (ROS) and depletion of antioxidant glutathione (GSH). Further, co-treatment with the antioxidant L-ascorbic acid mitigated the ROS generation and GSH depletion due to nickel ferrite nanoparticles suggesting the potential mechanism of oxidative stress. Quantitative real-time PCR analysis demonstrated that following the exposure of A549 cells to nickel ferrite nanoparticles, the level of mRNA expressions of cell cycle checkpoint protein p53 and apoptotic proteins (bax, caspase-3 and caspase-9) were significantly up-regulated, whereas the expression of anti-apoptotic proteins (survivin and bcl-2) were down-regulated. Moreover, activities of caspase-3 and caspase-9 enzymes were also significantly higher in nickel ferrite nanoparticles exposed cells. To the best of our knowledge this is the first report showing that nickel ferrite nanoparticles induced apoptosis in A549 cells through ROS generation and oxidative stress via p53, survivin, bax/bcl-2 and caspase pathways. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Gain and Bandwidth Enhancement of Ferrite-Loaded CBS Antenna Using Material Shaping and Positioning

NASA Astrophysics Data System (ADS)

Askarian Amiri, Mikal

Loading a cavity-backed slot (CBS) antenna with ferrite material and applying a biasing static magnetic field can be used to control its resonant frequency. Such a mechanism results in a frequency reconfigurable antenna. However, placing a lossy ferrite material inside the cavity can reduce the gain or negatively impact the impedance bandwidth. This thesis develops guidelines, based on a non-uniform applied magnetic field and non-uniform magnetic field internal to the ferrite specimen, for the design of ferrite-loaded CBS antennas which enhance their gain and tunable bandwidth by shaping the ferrite specimen and judiciously locating it within the cavity. To achieve these objectives, it is necessary to examine the influence of the shape and relative location of the ferrite material, and also the proximity of the ferrite specimen from the probe on the DC magnetic field and RF electric field distributions inside the cavity. The geometry of the probe and its impacts on figures-of-merit of the antenna is of interest as well. Two common cavity backed-slot antennas (rectangular and circular cross-section) were designed, and corresponding simulations and measurements were performed and compared. The cavities were mounted on 30 cm × 30 cm perfect electric conductor (PEC) ground planes and partially loaded with ferrite material. The ferrites were biased with an external magnetic field produced by either an electromagnet or permanent magnets. Simulations were performed using FEM-based commercial software, Ansys' Maxwell 3D and HFSS. Maxwell 3D is utilized to model the non-uniform DC applied magnetic field and non-uniform magnetic field internal to the ferrite specimen; HFSS however, is used to simulate and obtain the RF characteristics of the antenna. To validate the simulations they were compared with measurements performed in ASU's EM Anechoic Chamber. After many examinations using simulations and measurements, some optimal designs guidelines with respect to the gain, return loss and tunable impedance bandwidth, were obtained and recommended for ferrite-loaded CBS antennas.

Removal of phosphate from water by amine-functionalized copper ferrite chelated with La(III).

PubMed

Gu, Wei; Li, Xiaodi; Xing, Mingchao; Fang, Wenkan; Wu, Deyi

2018-04-01

Eutrophication has become a worldwide environmental problem and removing phosphorus from water/wastewater before discharge is essential. The purpose of our present study was to develop an efficient material in terms of both phosphate adsorption capacity and magnetic separability. To this end, we first compared the performances of four spinel ferrites, including magnesium, zinc, nickel and copper ferrites. Then we developed a copper ferrite-based novel magnetic adsorbent, by synthesizing 1,6-hexamethylenediamine-functionalized copper ferrite(CuFe 2 O 4 ) via a single solvothermal synthesis process followed by LaCl 3 treatment. The materials were characterized with X-ray diffraction, transmission electron microscope, vibrating sample magnetometer, Fourier transform infrared spectra and N 2 adsorption-desorption. The maximum adsorption capacity of our material, calculated from the Langmuir adsorption isotherm model, attained 32.59mg/g with a saturation magnetization of 31.32emu/g. Data of adsorption kinetics were fitted well to the psuedo-second-order model. Effects of solution pH and coexisting anions (Cl - , NO 3 - , SO 4 2- ) on phosphate adsorption were also investigated, showing that our material had good selectivity for phosphate. But OH - competed efficiently with phosphate for adsorption sites. Furthermore, increasing both NaOH concentration and temperature resulted in an enhancement of desorption efficiency. Thus NaOH solution could be used to desorb phosphate adsorbed on the material for reuse, by adopting a high NaOH concentration and/or a high temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of milling atmosphere on structural and magnetic properties of Ni-Zn ferrite nanocrystalline

NASA Astrophysics Data System (ADS)

Hajalilou, Abdollah; Hashim, Mansor; Ebrahimi-Kahrizsangi, Reza; Masoudi Mohamad, Taghi

2015-04-01

Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres (argon, air, and oxygen), milling time (from 0 to 30 h) and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600 °C for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated. Project supported by the University Putra Malaysia Graduate Research Fellowship Section.

Martensitic/ferritic steels as container materials for liquid mercury target of ESS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Y.

1996-06-01

In the previous report, the suitability of steels as the ESS liquid mercury target container material was discussed on the basis of the existing database on conventional austenitic and martensitic/ferritic steels, especially on their representatives, solution annealed 316 stainless steel (SA 316) and Sandvik HT-9 martensitic steel (HT-9). Compared to solution annealed austenitic stainless steels, martensitic/ferritic steels have superior properties in terms of strength, thermal conductivity, thermal expansion, mercury corrosion resistance, void swelling and irradiation creep resistance. The main limitation for conventional martensitic/ferritic steels (CMFS) is embrittlement after low temperature ({le}380{degrees}C) irradiation. The ductile-brittle transition temperature (DBTT) can increase asmore » much as 250 to 300{degrees}C and the upper-shelf energy (USE), at the same time, reduce more than 50%. This makes the application temperature range of CMFS is likely between 300{degrees}C to 500{degrees}C. For the present target design concept, the temperature at the container will be likely controlled in a temperature range between 180{degrees}C to 330{degrees}C. Hence, CMFS seem to be difficult to apply. However, solution annealed austenitic stainless steels are also difficult to apply as the maximum stress level at the container will be higher than the design stress. The solution to the problem is very likely to use advanced low-activation martensitic/ferritic steels (LAMS) developed by the fusion materials community though the present database on the materials is still very limited.« less

Influence of Annealing on the Depth Microstructure of the Shot Peened Duplex Stainless Steel at Elevated Temperature

NASA Astrophysics Data System (ADS)

Feng, Qiang; She, Jia; Xiang, Yong; Wu, Xianyun; Wang, Chengxi; Jiang, Chuanhai

The depth profiles of residual stresses and lattice parameters in the surface layers of shot peened duplex stainless steel at elevated temperature were investigated utilizing X-ray diffraction analysis. At each deformation depth, residual stress distributions in both ferrite and austenite were studied by X-ray diffraction stress analysis which is performed on the basis of the sin2ψ method and the lattice parameters were explored by Rietveld method. The results reveal that difference changes of depth residual compressive stress profiles between ferrite and austenite under the same annealing condition are resulted from the diverse coefficient of thermal expansion, dislocation density, etc. for different phases in duplex stainless steel. The relaxations of depth residual stresses in austenite are more obvious than those in ferrite. The lattice parameters decrease in the surface layer with the extending of annealing time, however, they increase along the depth after annealing for 16min. The change of the depth lattice parameters can be ascribed to both thermal expansion and the relaxation of residual stress. The different changes of microstructure at elevated temperature between ferrite and austenite are discussed.

Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

NASA Astrophysics Data System (ADS)

Isasti, Nerea; Jorge-Badiola, Denis; Taheri, Mitra L.; Uranga, Pello

2013-08-01

A complete microstructural characterization and phase transformation analysis has been performed for several Nb and Nb-Mo microalloyed low-carbon steels using electron backscattered diffraction (EBSD) and dilatometry tests. Compression thermomechanical schedules were designed resulting in the undeformed and deformed austenite structures before final transformation. The effects of microalloying additions and accumulated deformation were analyzed after CCT diagram development and microstructural quantification. The resulting microstructures ranged from polygonal ferrite and pearlite at slow cooling ranges, to a combination of quasipolygonal ferrite and granular ferrite for intermediate cooling rates, and finally, to bainitic ferrite with martensite for fast cooling rates. The addition of Mo promotes a shift in the CCT diagrams to lower transformation start temperatures. When the amount of Nb is increased, CCT diagrams show little variations for transformations from the undeformed austenite and higher initial transformation temperatures in the transformations from the deformed austenite. This different behavior is due to the effect of niobium on strain accumulation in austenite and its subsequent acceleration of transformation kinetics. This article shows the complex interactions between chemical composition, deformation, and the phases formed, as well as their effect on microstructural unit sizes and homogeneity.

Microstructure, crystallography and nucleation mechanism of NANOBAIN steel

NASA Astrophysics Data System (ADS)

Huang, Yao; Zhao, Ai-min; He, Jian-guo; Wang, Xiao-pei; Wang, Zhi-gang; Qi, Liang

2013-12-01

The microstructure of bainite ferrite in NANOBAIN steel transformed at different temperatures was investigated by scanning electron microscopy, transmission electron microscopy, electron back-scattered diffraction, and vickers hardness tester in detail. It is found that the average width of bainitic ferrite (BF) plates can be refined to be thinner with the reduction of temperature (473-573 K), and the bainitic ferrite plates can reach up to 20-74 nm at 473 K. Crystallographic analysis reveals that the bainitic ferrite laths are close to the Nishiyama-Wasserman orientation relationship with their parent austenite. Temperature shows a significant effect on the variant selection, and a decrease in temperature generally weakens the variant selection. Thermodynamic analyses indicates that the Lacher, Fowler and Guggenheim (LFG) model is more suitable than the Kaufman, Radcliffe and Cohen (KRC) model dealing with NANOBAIN steel at a low temperature range. The free energy change Δ G γ→BF is about -1500 J·mol-1 at 473 K, which indicates that nucleation in NANOBAIN steel is the shear mechanism. Finally, the formation of carbon poor regions is thermodynamically possible, and the existence of carbon poor regions can greatly increase the possibility of the shear mechanism.

Nanoscale-driven crystal growth of hexaferrite heterostructures for magnetoelectric tuning of microwave semiconductor integrated devices.

PubMed

Hu, Bolin; Chen, Zhaohui; Su, Zhijuan; Wang, Xian; Daigle, Andrew; Andalib, Parisa; Wolf, Jason; McHenry, Michael E; Chen, Yajie; Harris, Vincent G

2014-11-25

A nanoscale-driven crystal growth of magnetic hexaferrites was successfully demonstrated at low growth temperatures (25-40% lower than the temperatures required often for crystal growth). This outcome exhibits thermodynamic processes of crystal growth, allowing ease in fabrication of advanced multifunctional materials. Most importantly, the crystal growth technique is considered theoretically and experimentally to be universal and suitable for the growth of a wide range of diverse crystals. In the present experiment, the conical spin structure of Co2Y ferrite crystals was found to give rise to an intrinsic magnetoelectric effect. Our experiment reveals a remarkable increase in the conical phase transition temperature by ∼150 K for Co2Y ferrite, compared to 5-10 K of Zn2Y ferrites recently reported. The high quality Co2Y ferrite crystals, having low microwave loss and magnetoelectricity, were successfully grown on a wide bandgap semiconductor GaN. The demonstration of the nanostructure materials-based "system on a wafer" architecture is a critical milestone to next generation microwave integrated systems. It is also practical that future microwave integrated systems and their magnetic performances could be tuned by an electric field because of the magnetoelectricity of hexaferrites.

Y3Fe5O12 nanoparticulate garnet ferrites: Comprehensive study on the synthesis and characterization fabricated by various routes

NASA Astrophysics Data System (ADS)

Niaz Akhtar, Majid; Azhar Khan, Muhammad; Ahmad, Mukhtar; Murtaza, G.; Raza, Rizwan; Shaukat, S. F.; Asif, M. H.; Nasir, Nadeem; Abbas, Ghazanfar; Nazir, M. S.; Raza, M. R.

2014-11-01

The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified conventional mixed oxide (MCMO) on the structure, morphology and magnetic properties of the (Y3Fe5O12) garnet ferrites have been studied in the present work. The samples of Y3Fe5O12 were sintered at 950 °C and 1150 °C (by SG and SC methods). For MCMO route the sintering was done at 1350 °C for 6 h. Synthesized samples prepared by various routes were investigated using X-ray diffraction (XRD) analysis, Field emission scanning electron microscopy (FESEM), Impedance network analyzer and transmission electron microscopy (TEM). The structural analysis reveals that the samples are of single phase structure and shows variations in the particle sizes and cells volumes, prepared by various routes. FESEM and TEM images depict that grain size increases with the increase of sintering temperature from 40 nm to 100 nm.Magnetic measurements reveal that garnet ferrite synthesized by sol gel method has high initial permeability (60.22) and low magnetic loss (0.0004) as compared to other garnet ferrite samples, which were synthesized by self combustion and MCMO methods. The M-H loops exhibit very low coercivity which enables the use of these materials in relays and switching devices fabrications. Thus, the garnet nanoferrites with low magnetic loss prepared by different methods may open new horizon for electronic industry for their use in high frequency applications.

Low temperature synthesis and enhanced electrical properties by substitution of Al3+ and Cr3+ in Co-Ni nanoferrites

NASA Astrophysics Data System (ADS)

Pervaiz, Erum; Gul, I. H.

2013-10-01

Aluminum and chromium substituted Co-Ni spinel nanoferrites were prepared by sol-gel auto combustion method. Structural parameters along with electrical and magnetic properties have been investigated in the present work. Crystallite sizes of nano ferrite estimated from the peak (311) lies in the range of 13-21 nm ±2 nm and compared with crystallite sizes calculated from Williamsons-Hall plots. DC electrical resistivity variations due to the concentration of aluminum and chromium in the host ferrite have been measured from 368 K to 573 K. Increase in the room temperature DC electrical resistivity was observed up to a concentration x=0.2 and then decreases for x >0.2. Dielectric parameters (real and imaginary part of complex permittivity, dielectric loss tangent) were studied as a function of frequency (20 Hz-5 MHz) and a decrease in the dielectric parameters was observed due to substitution of nickel, aluminum and chromium ions in cobalt nanoferrites. AC conductivity, complex impedance and complex electrical modulus were studied as a function of frequency for the conduction and relaxation mechanisms in the present ferrite system. Saturation magnetization, coercivity, canting angles and magneto crystalline anisotropy variations with composition were observed and presented for the present ferrites under an applied magnetic field of 10 kOe at room temperature. It was found that both magnetization and coercivity decreases with increase in the concentration of aluminum and chromium along with a decrease in the anisotropy parameters. High DC resistivity with low dielectric parameters of the present nanoferrites make them suitable for high frequency and electromagnetic wave absorbing devices. High purity mixed Co-Ni-Al-Cr nanoferrites have been prepared by sol-gel auto combustion method. DC electrical resistivity increases due to substitution of Al3+ and Cr3+. Complex permittivity decrease for Co-Ni-Al-Cr nanoferrites. Detailed AC response analysis has been presented for mixed Co-Ni-Al-Cr nanoferrites. Magnetization and coercively reduces for Al3+ and Cr3+ doped Co-Ni ferrite nanoparticles showing that material is becoming soft magnetic.

Study of gamma ray energy absorption and exposure buildup factors for ferrites by geometric progression fitting method

NASA Astrophysics Data System (ADS)

Raut, S. D.; Awasarmol, V. V.; Shaikh, S. F.; Ghule, B. G.; Ekar, S. U.; Mane, R. S.; Pawar, P. P.

2018-04-01

The gamma ray energy absorption and exposure buildup factors (EABF and EBF) were calculated for ferrites such as cobalt ferrite (CoFe2O4), zinc ferrite (ZnFe2O4), nickel ferrite (NiFe2O4) and magnesium ferrite (MgFe2O4) using five parametric geometric progression (G-P fitting) formula in the energy range 0.015-15.00 MeV up to the penetration depth 40 mean free path (mfp). The obtained data of absorption and exposure buildup factors have been studied as a function of incident photon energy and penetration depth. The obtained EABF and EBF data are useful for radiation dosimetry and radiation therapy.

Structural, optical, dielectric and magnetic studies of gadolinium-added Mn-Cu nanoferrites

NASA Astrophysics Data System (ADS)

Kanna, R. Rajesh; Lenin, N.; Sakthipandi, K.; Kumar, A. Senthil

2018-05-01

Spinel ferrite with the general formula Mn1-xCuxFe1.85Gd0.15O4 (x = 0.2, 0.4, 0.6 and 0.8) was synthesized using the standard sonochemical method. The structure, optical, morphology, dielectric and magnetic properties of the prepared Mn1-xCuxFe1.85Gd0.15O4 nanoferrites were exhaustively investigated using various characterization techniques. The phase purity, secondary phase and crystallite parameters were studied from X-ray diffraction patterns. Fourier transform infrared spectra showed two absorption bands of transition metal oxides in the frequency range from 400 to 650 cm-1, which are related to asymmetric stretching modes of the spinel ferrites (AB2O4). Raman spectra have five active modes illustrating the vibration of O2- ions at both tetrahedral (A) site and octahedral (B) site ions. The wide and narrow scan spectrum from X-ray photoelectron spectroscopy results confirmed the presence of Mn, Cu, Gd, Fe, C and O elements in the composition. The oxidation state and core level of the photo electron peaks of Mn 2p, Cu 2p, Gd 3d, Fe 2p and O 1s were analyzed. The influence of the Cu2+ concentration in Mn1-xCuxFe1.85Gd0.15O4 on the morphology, varying from nanorods, nanoflakes to spherical, was explored on the basis of scanning electron microscopy images. Ultraviolet diffuse reflectance spectroscopy studies indicated that the optical bandgap (5.12-5.32 eV) of the nanoferrites showed an insulating behavior. The dielectric constant, loss tangent and complex dielectric constant values decreased with an increase in frequency with the addition of Gd3+ content. A vibrating sample magnetometer showed that the prepared nanoferrites had a soft ferromagnetic nature. The magnetic parameter changed markedly with an increase in the Cu content in Mn1-xCuxFe1.85Gd0.15O4 nanoferrites. The optical, dielectric and magnetic properties were considerably enhanced with the addition of Gd3+ ions in the spinel nanoferrites.

Magnetic induction spectroscopy (MIS)-probe design for cervical tissue measurements.

PubMed

Wang, Jau-Yi; Healey, Timothy; Barker, Anthony; Brown, Brian; Monk, Chris; Anumba, Dilly

2017-05-01

Gradiometers have the advantage of increasing measuring sensitivity, which is particularly useful in magnetic induction spectroscopy (MIS) for bio-impedance measurements. Traditional gradiometers use a pair of field sensing coils equally distant and on opposite sides of a drive coil, which provides high immunity to interference. In this paper, a ferrite-cored coaxial gradiometer probe of 29 mm diameter has been developed for measuring the impedance spectra of cervical tissues in vivo. It consists of a ferrite rod with outer ferrite confinement screening in order to eliminate the signals from surrounding tissue. The magnetic screening efficiency was compared with an air-cored gradiometer probe. For both gradiometer probes, a drive coil and two sensing coils were wound on a borosilicate glass former aligned coaxially with two sensing coils equidistant from the drive coil. The signal sensitivity of those two MIS gradiometers has been measured using saline samples with a conductivity range between 0.1 and 1.1 S m -1 . Finite element methods using COMSOL Multiphysics have been used to simulate the distribution of sensitivity to conductivity over the face of each probe and with depth. The ferrite-cored probe has a sensitivity confined to the volume defined by the gap between the ferrite core and outer tube of ferrite while the air-cored probe without any magnetic shielding had a wide sensitivity over the face and the side of the probe. Four saline samples and one of distilled water with conductivities from 0.1 to 1.1 S m -1 have been used to make conductivity measurements at frequencies of 50 kHz, 100 kHz, and 300 kHz. The measurement accuracy of the air-cored MIS probe was 0.09 S m -1 at 50 kHz, improving to 0.05 S m -1 at 300 kHz. For the ferrite-cored MIS probe, the measurement accuracy was 0.28 S m -1 at 50 kHz, improving to 0.04 S m -1 at 300 kHz. In vivo measurements on human hand have been performed using both types of gradiometers and the conductivity is consistent with reported data.

Sigma phases in an 11%Cr ferritic/martensitic steel with the normalized and tempered condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yinzhong, E-mail: shenyz@sjtu.edu.cn

At the present time 9–12% Cr ferritic/martensitic (F/M) steels with target operating temperatures up to 650 °C and higher are being developed in order to further increase thermal efficiency so as to reduce coal consumption and air pollution. An 11% Cr F/M steel was prepared by reference to the nominal chemical composition of SAVE12 steel with an expected maximum use temperature of 650 °C. The precipitate phases of the 11% Cr F/M steel normalized at 1050 °C for 0.5 h and tempered at 780 °C for 1.5 h were investigated by transmission electron microscopy. Except for Cr-/Cr-Fe-Co-rich M{sub 23}C{sub 6},more » Nb-/V-/Ta-Nb-/Nd-rich MX, Fe-rich M{sub 5}C{sub 2}, Co-rich M{sub 3}C and Fe-Co-rich M{sub 6}C phases previously identified in the steel, two types of sigma phases consisting of σ-FeCr and σ-FeCrW were found to be also present in the normalized and tempered steel. Identified σ-FeCr and σ-FeCrW phases have a simple tetragonal crystal structure with estimated lattice parameters a/c = 0.8713/0.4986 and 0.9119/0.5053 nm, respectively. The compositions in atomic pct of the observed sigma phases were determined to be approximately 50Fe-50Cr for the σ-FeCr, and 30Fe-55Cr-10W in addition to a small amount of Ta, Co and Mn for the σ-FeCrW. The sigma phases in the steel exhibit various blocky morphologies, and appear to have a smaller amount compared with the dominant phases Cr-rich M{sub 23}C{sub 6} and Nb-/V-/Ta-Nb-rich MX of the steel. The σ-FeCr phase in the steel was found to precipitate at δ-ferrite/martensite boundaries, suggesting that δ-ferrite may rapidly induce the formation of sigma phase at δ-ferrite/martensite boundaries in high Cr F/M steels containing δ-ferrite. The formation mechanism of sigma phases in the steel is also discussed in terms of the presence of δ-ferrite, M{sub 23}C{sub 6} precipitation, precipitation/dissolution of M{sub 2}X, and steel composition. - Highlights: •Precipitate phases in normalized and tempered 11%Cr F/M steel are presented in detail. • σ-FeCr phase, 50Fe50Cr (in at.%), was identified in normalized and tempered 11%Cr F/M steel. • σ-FeCrW phase, 30Fe55Cr10W (in at.%), was identified in normalized and tempered 11%Cr F/M steel. • Sigma phase in the 11%Cr F/M steel was found to precipitate at δ-ferrite/martensite boundaries. • δ-ferrite may rapidly induce the sigma phase formation at δ-ferrite/martensite boundaries.« less

Assessment of Stress Corrosion Cracking Resistance of Activated Tungsten Inert Gas-Welded Duplex Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Alwin, B.; Lakshminarayanan, A. K.; Vasudevan, M.; Vasantharaja, P.

2017-12-01

The stress corrosion cracking behavior of duplex stainless steel (DSS) weld joint largely depends on the ferrite-austenite phase microstructure balance. This phase balance is decided by the welding process used, heat input, welding conditions and the weld metal chemistry. In this investigation, the influence of activated tungsten inert gas (ATIG) and tungsten inert gas (TIG) welding processes on the stress corrosion cracking (SCC) resistance of DSS joints was evaluated and compared. Boiling magnesium chloride (45 wt.%) environment maintained at 155 °C was used. The microstructure and ferrite content of different weld zones are correlated with the outcome of sustained load, SCC test. Irrespective of the welding processes used, SCC resistance of weld joints was inferior to that of the base metal. However, ATIG weld joint exhibited superior resistance to SCC than the TIG weld joint. The crack initiation and final failure were in the weld metal for the ATIG weld joint; they were in the heat-affected zone for the TIG weld joint.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Yun; Wu, Xiaohan; Li, Qifan

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 lossmore » 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.« less

Comparative Cytogenetic Study on the Toxicity of Magnetite and Zinc Ferrite Nanoparticles in Sunflower Root Cells

NASA Astrophysics Data System (ADS)

Foca-nici, Ecaterina; Capraru, Gabriela; Creanga, Dorina

2010-12-01

In this experimental study the authors present their results regarding the cellular division rate and the percentage of chromosomal aberrations in the root meristematic cells of Helianthus annuus cultivated in the presence of different volume fractions of magnetic nanoparticle suspensions, ranging between 20 and 100 microl/l. The aqueous magnetic colloids were prepared from chemically co-precipitated ferrites coated in sodium oleate. Tissue samples from the root meristeme of 2-3 day old germinated seeds were taken to prepare microscope slides following Squash method combined with Fuelgen techniques. Microscope investigation (cytogenetic tests) has resulted in the evaluation of mitotic index and chromosomal aberration index that appeared diminished and respectively increased following the addition of magnetic nanoparticles in the culture medium of the young seedlings. Zinc ferrite toxic influence appeared to be higher than that of magnetite, according to both cytogenetic parameters.

Structural and magnetic properties of ytterbium substituted spinel ferrites

NASA Astrophysics Data System (ADS)

Alonizan, Norah H.; Qindeel, Rabia

2018-06-01

Chemical co-precipitation route adopted to synthesize the magnetic materials. In the present work, iron is replaced by ytterbium ion in manganese-based spinel ferrites. The yield chemically represented by MnYb x Fe2- x O4 ( x = 0.00, 0.025, 0.05, 0.075, 0.10) and its structural, magnetic and electrical properties were observed. The cubic structure of spinel ferrites was confirmed by X-ray diffraction analysis. Spherically shaped grains were perceived in SEM pictures and size lessened with the growth of ytterbium concentration. SEM profile also shows little irregularity in spherical particles. The substitution of ytterbium (Yb) results in the enhancement of electrical resistivity. The resistivity was reduced with the gradual increase in temperature from 303 to 693 K. The trend of activation energy was found to be similar to that of room temperature resistivity. The coercivity of samples was raised with Yb-ion substitution while saturation magnetization and remanence reduced.

Hardening of ODS ferritic steels under irradiation with high-energy heavy ions

NASA Astrophysics Data System (ADS)

Ding, Z. N.; Zhang, C. H.; Yang, Y. T.; Song, Y.; Kimura, A.; Jang, J.

2017-09-01

Influence of the nanoscale oxide particles on mechanical properties and irradiation resistance of oxide-dispersion-strengthened (ODS) ferritic steels is of critical importance for the use of the material in fuel cladding or blanket components in advanced nuclear reactors. In the present work, impact of structures of oxide dispersoids on the irradiation hardening of ODS ferritic steels was studied. Specimens of three high-Cr ODS ferritic steels containing oxide dispersoids with different number density and average size were irradiated with high-energy Ni ions at about -50 °C. The energy of the incident Ni ions was varied from 12.73 MeV to 357.86 MeV by using an energy degrader at the terminal so that a plateau of atomic displacement damage (∼0.8 dpa) was produced from the near surface to a depth of 24 μm in the specimens. A nanoindentor (in constant stiffness mode with a diamond Berkovich indenter) and a Vickers micro-hardness tester were used to measure the hardeness of the specimens. The Nix-Gao model taking account of the indentation size effect (ISE) was used to fit the hardness data. It is observed that the soft substrate effect (SSE) can be diminished substantially in the irradiated specimens due to the thick damaged regions produced by the Ni ions. A linear correlation between the nano-hardeness and the micro-hardness was found. It is observed that a higher number density of oxide dispersoids with a smaller average diameter corresponds to an increased resistance to irradiation hardening, which can be ascribed to the increased sink strength of oxides/matrix interfaces to point defects. The rate equation approach and the conventional hardening model were used to analyze the influence of defect clusters on irradiation hardening in ODS ferritic steels. The numerical estimates show that the hardening caused by the interstitial type dislocation loops follows a similar trend with the experiment data.