scholarly journals Role of Disordered Precursor in L10 Phase Formation in FePt-Based Nanocomposite Magnet

2021 ◽  
Vol 7 (11) ◽  
pp. 149
Author(s):  
Alina Daniela Crisan ◽  
Ioan Dan ◽  
Ovidiu Crisan
Keyword(s):  
Permanent Magnets ◽  
Magnetic Measurements ◽  
Phase Evolution ◽  
Annealed Sample ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
Spectra Analysis ◽  
Annealing Temperatures ◽  
Wide Range

In order to prove the usefulness of having a structurally disordered precursor to the formation of FePt L10 phase and to facilitate the co-existence of exchange coupled hard and soft magnetic phases with optimized magnetic properties in various conditions of annealing, a Fe-Pt-Zr-B melt spun alloy has been synthesized and detailed structural and magnetic investigations have been undertaken to probe its phase evolution during annealing. The dynamics of formation of the hard magnetic L10 phase during the gradual disorder–order phase transformation has been monitored by using a complex combination of X-ray diffraction methods and 57Fe Mössbauer spectroscopy methods, over a wide range of annealing temperatures. Multiple phases co-existing in the annealed sample microstructures, observed in XRD, have been reconfirmed by the Mössbauer spectra analysis and, moreover, accurate quantitative data have been acquired in what concerns the relative abundance of each of the observed crystalline phases in every stage of annealing. It is shown that the formation of the hard magnetic phase, emerging from the chemically disordered precursor, is gradual and occurs via complex mechanisms, involving the presence of a disordered Fe-Zr-B-rich intergranular region which contributes to an increase in the abundance of the L10 phase for higher annealing temperatures. Magnetic measurements have confirmed the good performances of these alloys in terms of coercivity and remanence. These results contribute to the development of these alloys as the next generation of rare earth, free permanent magnets.

Influence of Alloying Additions on Enhancement of Soft Magnetic Properties Effect and Crystallization in FeXSiB (X=Cu, V, Co, Zr, Nb) Amorphous Alloys

2007 ◽  
Vol 130 ◽  
pp. 171-174 ◽  
Author(s):  
Z. Stokłosa ◽  
G. Badura ◽  
P. Kwapuliński ◽  
Józef Rasek ◽  
G. Haneczok ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Crystallization Process ◽  
Annealing Temperature ◽  
Magnetic Measurements ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
X Ray ◽  
Second Stage ◽  
Transmission Electron

The crystallization and optimization of magnetic properties effects in FeXSiB (X=Cu, V, Co, Zr, Nb) amorphous alloys were studied by applying X-ray diffraction methods, high resolution transmission electron microscopy (HRTEM), resistometric and magnetic measurements. The temperatures of the first and the second stage of crystallization, the 1h optimization annealing temperature and the Curie temperature were determined for different amorphous alloys. Activation energies of crystallization process were obtained by applying the Kissinger method. The influence of alloy additions on optimization effect and crystallization processes was carefully examined.

Synthesis of Fe2O3/CNTs for the Fast Removal of Tetracycline from Aqueous Solutions

2014 ◽  
Vol 915-916 ◽  
pp. 933-941 ◽  
Author(s):  
Zhong Jie Zhang ◽  
Chang Yu Lu ◽  
Wei Huang ◽  
Wei Sheng Guan ◽  
Yue Xin Peng
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Magnetic Measurements ◽  
Ferrite Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Wide Range ◽  
Fast Removal ◽  
Scanning Electron

The effective remove to tetracycline still remains a big challenge for scientists. In this work, we used a new method for preparing functional magnetic CNTS with ferrite nanoparticles. A wide range of techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurements were applied to characterize the obtained Fe2O3/CNTs. Moreover, we have also studied the properties of adsorbent to tetracycline. In addition, we have found that the Fe2O3/CNTs are better reusable adsorbent than other traditional adsorbents by magnetic separation recycling method.

Effect of Ferric Oxide Nanoparticles Incorporation on Structure and Electrical Properties of Modified BNKT Ceramics

2019 ◽  
Vol 798 ◽  
pp. 182-187
Author(s):  
Pharatree Jaita ◽  
Supalak Manotham ◽  
Ratabongkot Sanjoom ◽  
Narumon Lertcumfu ◽  
Tawee Tunkasiri
Keyword(s):  
Electrical Properties ◽  
Electric Field ◽  
Ferric Oxide ◽  
Phase Evolution ◽  
Maximum Temperature ◽  
Oxide Nanoparticles ◽  
X Ray Diffraction ◽  
Spectra Analysis ◽  
Average Grain Size ◽  
Electric Field Induced Strain

The BNKBST30 + 3 vol% Fe2O3 ceramic was fabricated via a solid-state mixed oxide and sintered 1125°C for 2 h. The effects of ferric oxide nanoparticles (Fe2O3) additive on phase evolution, microstructure and electrical properties, i.e. dielectric, ferroelectric and electric field-induced strain, of BNKBST30 ceramic was investigated. The obtain ceramic was well sintered and densely with high density of 5.78 g/cm3. X-ray diffraction pattern and Raman spectra analysis showed a single perovskite with a mixed rhombohedral (R3c) and tetragonal (P4bm) phases. The obtained ceramic had a cubic-like grain shape with an average grain size of 0.82 µm. The dielectric constant as a function of temperature curves exhibited broad transition peaks at maximum temperature (Tm). The ceramic also showed good dielectric (er = 1085, tan d = 0.0496, er,max = 6099, Tm = 296 °C), ferroelectric (Pr = 27.18 µC/cm2, Ec = 20.32 kV/cm, Rsq = 0.95), and electric field-induced strain properties (Smax = 0.22 %, Sneg = - 0.08 %, d*33 = 440 pm/V). The obtained results indicated that the studied ceramic is considered as candidate for lead-free electromechanical applications.

Fourfold Magnetic Anisotropy of CoPd Alloy, Obtained by Solid State Reactions in Epitaxal Pd/hcp-Сo and Pd/fcc-Co Bilayers

2015 ◽  
Vol 233-234 ◽  
pp. 571-574
Author(s):  
V.G. Myagkov ◽  
L.E. Bykova ◽  
V.S. Zhigalov ◽  
I.A. Tambasov ◽  
G.N. Bondarenko ◽  
...  
Keyword(s):  
Solid State ◽  
Magnetocrystalline Anisotropy ◽  
Magnetic Measurements ◽  
Anisotropy Constant ◽  
Solid State Reactions ◽  
Atomic Composition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Annealing Temperatures ◽  
Disordered Phase

The solid-state reaction between epitaxial hcp-Co (110) and fcc-Co (001) thin films and Pd layers was investigated at annealing temperatures between 250 and 650 °C using X-ray diffraction and magnetic measurements. No significant intermixing of the layers occurs at annealing temperatures below 400 °C. For the atomic composition 1Co:1Pd after annealing at 450 °C the disordered solid solution fcc-CoxPd1-x is formed on the Pd/hcp-Co (110) and Pd/fcc-Co (001) interfaces. Epitaxial relationships CoPd (110)〈-111〉 || MgO(001)〈100〉 and CoPd (001)〈100〉 || MgO(001)〈100〉 between the nucleated disordered phase CoPd and the substrate MgO(001) were determined for Pd/hcp-Co (110) and Pd/fcc-Co (001) bilayers, respectively. The first magnetocrystalline anisotropy constant of the disordered CoPd phase ​​K1CoPd = - (1.8 ± 0.4)·104 J/m3 for the (110) and (001) orientations was obtained.

Nanostructured NiFe2O4 Soft Magnetic Ferrite

2001 ◽  
Vol 703 ◽  
Author(s):  
Zongtao Zhang ◽  
Y. D. Zhang ◽  
T. D. Xiao ◽  
Shihui Ge ◽  
Mingzhong Wu ◽  
...  
Keyword(s):  
Magnetic Measurements ◽  
Initial Permeability ◽  
High Resistivity ◽  
Crystallographic Structure ◽  
Ceramic Processing ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
Calcination Temperatures ◽  
Transmission Electron ◽  
Improved Performance

ABSTRACTNiFe2O4 is an important high frequency soft magnetic material due to its ultra high resistivity; however, its initial permeability is rather low. Conventional magnetic ferrites are manufactured through ceramic processing. In an effort to explore innovative approaches for fabricating ferrite materials with improved performance, a study of fabricating nanostructured NiFe2O4 using wet chemical approaches has been carried out. The synthetic NiFe2O4 precursor was synthesized by a citrate reaction method followed by calcinating at various temperatures. Systematic studies concerning the crystallographic structure, the nanostructure and morphology of the particle, the phase homogeneity, the conditions for chemical reaction completion, and the magnetic properties have been carried out using x-ray diffraction, transmission electron microscopy, and magnetic measurements. The results show that by using a citrate reaction approach, pure phase and stoichiometric NiFe2O4 can be fabricated easily, and the particle size can be controlled on a nanometer scale, even at high calcination temperatures. In addition, a comparative study of the NiFe2O4 fabricated by conventional ceramic processing and this new citrate processing will be presented.

Correlation of Stress and Phase Evolution in Thin Ta Films On Si (100) During Thermal Testing

2002 ◽  
Vol 750 ◽  
Author(s):  
B. L. French ◽  
J. C. Bilello
Keyword(s):  
Stress Responses ◽  
Phase Evolution ◽  
Stress Generation ◽  
Thermal Testing ◽  
X Ray Diffraction ◽  
Thermal Tests ◽  
Mechanical Responses ◽  
As Stress ◽  
Radiation Laboratory

ABSTRACTIn this study the stress and morphology of Ta coatings sputtered on Si (100) substrates were monitored in situ and in real-time during thermal testing to allow interruptions at critical events in the coatings' stress evolution. These observations were carried out using white beam Laue transmission diffraction topography/radiography and a high-temperature sample stage at the Stanford Synchrotron Radiation Laboratory (SSRL). The structure of specimens from interrupted thermal tests was then analyzed using x-ray diffraction θ-2θ scans. The structure and phases present in the film at different stages of the thermal test were correlated with specific mechanical responses in the coating such as stress generation. This information was employed to elucidate the role of phase evolution in the respective stress responses of films deposited in high and low-pressure regimes.

scholarly journals Magnetic Phase Coexistence and Hard–Soft Exchange Coupling in FePt Nanocomposite Magnets

Nanomaterials ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1618
Author(s):  
O. Crisan ◽  
I. Dan ◽  
P. Palade ◽  
A. D. Crisan ◽  
A. Leca ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Squid Magnetometry ◽  
X Ray Diffraction ◽  
Soft Magnetic ◽  
Magnetic Phases ◽  
X Ray ◽  
Annealing Temperatures ◽  
Nanocomposite Magnets ◽  
Inflection Points

With the aim of demonstrating phase coexistence of two magnetic phases in an intermediate annealing regime and obtaining highly coercive FePt nanocomposite magnets, two alloys of slightly off-equiatomic composition of a binary Fe-Pt system were prepared by dynamic rotation switching and ball milling. The alloys, with a composition Fe53Pt47 and Fe55Pt45, were subsequently annealed at 400 °C and 550 °C and structurally and magnetically characterized by means of X-ray diffraction, 57Fe Mössbauer spectrometry and Superconducting Quantum Interference Device (SQUID) magnetometry measurements. Gradual disorder–order phase transformation and temperature-dependent evolution of the phase structure were monitored using X-ray diffraction of synchrotron radiation. It was shown that for annealing temperatures as low as 400 °C, a predominant, highly ordered L10 phase is formed in both alloys, coexisting with a cubic L12 soft magnetic FePt phase. The coexistence of the two phases is evidenced through all the investigating techniques that we employed. SQUID magnetometry hysteresis loops of samples annealed at 400 °C exhibit inflection points that witness the coexistence of the soft and hard magnetic phases and high values of coercivity and remanence are obtained. For the samples annealed at 500 °C, the hysteresis loops are continuous, without inflection points, witnessing complete exchange coupling of the hard and soft magnetic phases and further enhancement of the coercive field. Maximum energy products comparable with values of current permanent magnets are found for both samples for annealing temperatures as low as 500 °C. These findings demonstrate an interesting method to obtain rare earth-free permanent nanocomposite magnets with hard–soft exchange-coupled magnetic phases.

scholarly journals Precipitation of CaCO3 Polymorphs from Aqueous Solutions: The Role of pH and Sulphate Groups

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 178 ◽  
Author(s):  
Iris Cuesta Mayorga ◽  
José Manuel Astilleros ◽  
Lurdes Fernández-Díaz
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Reaction Times ◽  
Precipitation Process ◽  
X Ray Diffraction ◽  
Wide Range ◽  
Ph Conditions ◽  
High Concentrations ◽  
Edx Microanalysis

In this work, we aimed to experimentally study the nucleation and growth of CaCO3 phases precipitated from supersaturated aqueous solutions in the presence of varying concentrations of sulphate oxyanion. The experiments were conducted under pH conditions close to neutral (7.6) and by considering a wide range of initial (SO42−)/(CO32−) ratios (0 to approx. 68) in the aqueous solution. We paid special attention to the evolution of the precipitates during ageing within a time framework of 14 days. The mineralogy, morphology, and composition of the precipitates were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and EDX microanalysis. The concentration of sulphate ions in the reacted aqueous solution was studied by ICPs. The experimental results showed that the mineral composition of the precipitate recovered in each run varied with the (SO42−)/(CO32−) ratio in the parental solution, which influenced the mineral evolution of the precipitates during ageing. We observed that high concentrations of sulphate in the aqueous solution stabilized the vaterite precipitates and inhibited calcite formation. Furthermore, aragonite never precipitated directly from the solution, and it was only formed via a dissolution-precipitation process in solutions with a high (SO42−)/(CO32−) ratio after long reaction times. Finally, gypsum only precipitated after long ageing in those aqueous solutions with the highest concentration of sulphate. The reaction pathways during ageing, the morphology of the calcite crystals, and the composition of vaterite and calcite were discussed considering both kinetic and thermodynamic factors. These results showed a considerably more complex behavior of the system than that observed in experiments conducted under higher pHs and supersaturation levels and lower (SO42−)/(CO32−) ratios in the aqueous phase.

scholarly journals Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 896
Author(s):  
Alina Daniela Crisan ◽  
Aurel Leca ◽  
Cristina Bartha ◽  
Ioan Dan ◽  
Ovidiu Crisan
Keyword(s):  
Phase Transformation ◽  
Permanent Magnets ◽  
Diffusion Processes ◽  
Magnetic Measurements ◽  
Low Cost ◽  
Antiphase Boundary ◽  
Rapid Quenching ◽  
Annealed Sample ◽  
Scanning Calorimetry ◽  
Ε Phase

Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets.

Measurement of Residual Stresses by X-ray Diffraction Near Simulated Heat Affected Zones in Austenitic Stainless Steels

1990 ◽  
Vol 34 ◽  
pp. 623-631
Author(s):  
V. S. Iyer ◽  
R. W. Hendricks ◽  
S. A. David
Keyword(s):  
Residual Stresses ◽  
Austenitic Stainless Steels ◽  
Maximum Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wide Range ◽  
Rate Maximum ◽  
Computer Controlled ◽  
Made In

AbstractSimulated heat-affected zones (HAZs) were made in austenitic sta.inless steel specimens using a Gleeble. The samples were heated to temperatures as high as 1100°C by computer controlled resistance heating. By controlling the heating rate, maximum temperature, and cooling rate, a wide range of residual stresses were introduced in the specimens. Stress measurements were made using X-ray diffraction. It was found that significant stress gradients were produced in the simulated HAZs, and that all stresses were compressive in nature, both in the longitudinal and transverse directions. These results are not representative of the residual stresses determined in the HAZs of real welds, thus calling into question some aspects of the role of the Gleeble in such simulations.

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