Glycol-thermal Method Research Articles

The effect of particle size on structural and magnetic properties of Zn0.5Co0.5Fe2O4 prepared by glycol-thermal technique

Zn0.5Co0.5Fe2O4 fine particles with grain size of about 9 mm were synthesized using the glycol-thermal method. Grain size increased to about 22 mm after annealing from 400 °C to 1100 °C. The X-ray diffraction (XRD) analysis confirmed formation of a single phase cubic structure of the compounds investigated. TEM images revealed agglomerated particles with spherical shapes and confirm particles sizes indicated by XRD data. Mössbauer spectra showed broad spectra due to fine particles which indicate ferrimagnetic ordered spin state. A general increase in hyperfine fields after annealing at temperatures above 500 °C due to increasing particle size relates well with saturation magnetization which increased to about 75 em/g after annealing at 1100 °C. The almost zero coercive fields at about 300 K and “S” shaped magnetization curves relating well with the “hump” in ZFC curve reveal superparamagnetic fine particles. An increase from about 0.1 kOe at room temperature to 3 kOe at 10 K due to spin freezing has been observed.

Structural, Mössbauer spectroscopy and magnetic study of Co1−xCdxFe2O4 ferrite synthesized by glycol-thermal method

The Cd2+ substituted Co1-xFe2O4 with concentrations of (0 ≤ x ≤ 0.7) nano ferrites were synthesized using the glycol-thermal method. X-ray diffraction (XRD) and Fourier-transformed infrared (FT-IR) spectroscopy confirmed the structural formation and nanocrystalline structure of spinel ferrites. Samples possess a cubic spinel lattice structure with crystallite sizes varying between 5.1 nm and 15.5 nm. Transmission electron microscopy (TEM) revealed fine particles which are nearly spherical in shape. The 57Fe Mössbauer spectral studies showed an ordered magnetic spin state for x ≤ 0.5 which transforms to a paramagnetic phase for x ≥ 0.6 due to the weakening of super-exchange interactions. The saturation magnetization (MS) was the highest at x = 0 with a value of 73.3 emu/g and fluctuated between 44.3 emu/g and 19.8 emu/g after the addition of non-magnetic Cd2+ ions. The field dependence of dM/dH curves reveals the finite size effect which leads to the frustration in magnetic moments.

Influence of rare-earth elements (RE = Ce, Nd, Gd) on structural, ESR and Mössbauer spectroscopy studies of Ni0.5Co0.5RE0.03Fe1.97O4 synthesized by glycol-thermal method

Nanocrystalline Ni0.5Co0.5RE0.03Fe1.97O4 (RE = Ce, Nd, Gd) were synthesized by glycol-thermal method. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results confirm the formation of single-phase spinel ferrite. The crystallite sizes ranged from 6.29 nm to 9.41 nm which was comparable to results obtained using Williamson-Hall (W–H) method. Lattice parameters were found to vary from 8.356 Å to 8.370 Å depending on an ionic radii of a substituted rare-earth elements. Large specific surface areas ranging between 120 m2/g and 160 m2/g were associated with smaller crystallite sizes. Scanning electron microscope (SEM) revealed homogeneous and clustered nanoparticles. The energy dispersive X-ray (EDS) spectra revealed the existence of nickel (Ni), cobalt (Co), iron (Fe), and oxygen (O) in an undoped sample. The additional characteristic peaks of cerium (Ce), neodymium (Nd) and gadolinium (Gd) were observed for doped samples. The electron spin resonance (ESR) results demonstrated g-values ranging between 3.10 and 3.79 which indicated strong exchange interaction between nanoparticles, type of morphology, and crystalline nature of particles. These high g-values make Ni0.5Co0.5RE0.03Fe1.97O4 (RE = Ce, Nd, Gd) materials suitable for applications in high-frequency devices. The Mössbauer spectroscopy results revealed the formation of broadened Zeeman lines and quadrupole-split lines as well as the presence of the Fe3+ ions at B sites in the samples.

Synthesis, Electron Spin Resonance and Photoluminescence properties of Sm3+ ion doped Zn-Mn nanoferrites synthesized by glycol-thermal method

Nanocrystalline Zn0.5Mn0.5SmxFe2-xO4 (0 ≤ x ≤ 0.05) with average crystallite sizes varying between 12 and 17 nm were synthesized by the glycol-thermal process. X-ray diffraction (XRD) analysis confirmed a single-phase cubic spinel structure in all the compounds. Substituting a smaller Fe3+ ion with a larger rare-earth (RE) Sm3+ ion has affected the distribution of metal ions on tetrahedral (A) and octahedral (B) sites. In this work, a comprehensive study has been carried out on nanocrystalline particles of RE Sm3+ ion doped into Zn-Mn ferrite to estimate intrinsic strain through Williamson-Hall (W–H) analysis. The results were compared with those obtained from the Debye Scherrer equation. Tensile microstrain within the nanocrystals were detected from W-H plots for x = 0, 0.01,0.02 and 0,05 samples, while compressive microstrain was observed for x = 0.02 and 0.05 samples. A scanning electron microscope (SEM) has been used to study the morphology of nanoparticles and it revealed spherical-shaped nanoparticles. Energy dispersive X-rays (EDX) confirmed the phase purity and the elemental composition with no impurity elements were observed. Crystallite sizes affect electron spin resonance (ESR) signal intensity and the line width. The g-values fluctuated ranging from 2.31 to 2.51 due to fluctuating crystallite sizes. Photoluminescence (PL) displayed a blue-violet emission with maxima centred at 418 nm and 438 nm under the excitation wavelength of 320 nm. The electron spin resonance and photoluminescence results show that the Sm doped Zn-Mn ferrites are promising candidates for applications in blue LEDs.

Magnetic Characterization of Co and Zn Nano Ferrites: Property Consideration for Oil-Spill Clean Up

Nano-magnetic particles are significantly finding applications in environmental remediation. This work studied the magnetic properties of Co and Zn nano-ferrites, CoFe2O4 and ZnFe2O4 respectively, with considerations for the properties that are desirable for oil spill cleanup. The ferrite nanoparticles were synthesized by the glycol-thermal method at 200 ºC for 6 hours using a stirred pressure reactor. Single phase spinel crystal structures were obtained for both samples as determined by an X-ray diffraction (XRD) machine. The high-resolution transmission electron microscope and surface electron microscope images showed nano structures. The magnetic properties and magnetic hyperfine parameters were determined using a lakeshore vibrating sample magnetometer and 57Fe Mössbauer spectroscopy. The XRD peaks were consistent with that of a single phase spinel structure. No impurity phase was detected. The nano-ferrites have crystallite sizes of about 10 nm and 17 nm for CoFe2O4 and ZnFe2O4. The nano almost-spherical nature of the samples was also confirmed from their morphology studies. The saturation magnetization of CoFe2O4 and ZnFe2O4 were about 50 emu/g and 30 emu/g respectively. They both exhibited superparamagnetic properties with a component of para-magnetism observed in ZnFe2O4 nano-ferrites. CoFe2O4 nano-ferrites exhibited better desired property for oil spill cleanup. The ZnFe2O4 nano-ferrites showed tendencies of slow response to magnetic field, however, it is more environmentally friendly. The magnetic hyperfine parameters and the isomer shift values for CoFe2O4 and ZnFe2O4 showed strong internal magnetic fields and the obtained values are consistent with spinel structure. The oxidation state of Fe was observed to be Fe3+. Due to the low coercivity and high magnetization values, these particles could be considered as potential candidates for oil spill cleanup. These desirable magnetic properties will improve the recyclability of the nanoparticles using low applied magnetic fields.

Chitosan, Polyethylene Glycol and Polyvinyl Alcohol Modified MgFe2O4 Ferrite Magnetic Nanoparticles in Doxorubicin Delivery: A Comparative Study In Vitro

Cancer-based magnetic theranostics has gained significant interest in recent years and can contribute as an influential archetype in the effective treatment of cancer. Owing to their excellent biocompatibility, minute sizes and reactive functional surface groups, magnetic nanoparticles (MNPs) are being explored as potential drug delivery systems. In this study, MgFe2O4 ferrite MNPs were evaluated for their potential to augment the delivery of the anticancer drug doxorubicin (DOX). These MNPs were successfully synthesized by the glycol-thermal method and functionalized with the polymers; chitosan (CHI), polyvinyl alcohol (PVA) and polyethylene glycol (PEG), respectively, as confirmed by Fourier transform infrared (FTIR) spectroscopy. X-ray diffraction (XRD) confirmed the formation of the single-phase cubic spinel structures while vibrating sample magnetometer (VSM) analysis confirmed the superparamagnetic properties of all MNPs. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) revealed small, compact structures with good colloidal stability. CHI-MNPs had the highest DOX encapsulation (84.28%), with the PVA-MNPs recording the lowest encapsulation efficiency (59.49%). The 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) cytotoxicity assays conducted in the human embryonic kidney (HEK293), colorectal adenocarcinoma (Caco-2), and breast adenocarcinoma (SKBR-3) cell lines showed that all the drug-free polymerized MNPs promoted cell survival, while the DOX loaded MNPs significantly reduced cell viability in a dose-dependent manner. The DOX-CHI-MNPs possessed superior anticancer activity (<40% cell viability), with approximately 85.86% of the drug released after 72 h in a pH-responsive manner. These MNPs have shown good potential in enhancing drug delivery, thus warranting further optimizations and investigations.

The effect of particle size on structural and magnetic properties of Sm3+ ion substituted Zn-Mn nanoferrites synthesized by glycol-thermal method

Zn0.5Mn0.5SmxFe2-xO4 (0 ≤ x 0.05) fine powders with average crystallite sizes in the range 12–17 nm were synthesized by glycol-thermal reaction. The as-prepared compounds were subjected to thermal annealing process at 1100 °C, after which the crystallite sizes increased to about 60 nm. XRD analysis confirmed a single-phase cubic spinel structure in all the compounds investigated. TEM images showed nearly spherical particles with uniform particle size distributions. SEM and FTIR have been used to study morphology and confirm phase formation, respectively. The Mössbauer spectrum for Zn0.5Mn0.5Fe2O4 (x = 0) at room temperature may be resolved into two quadrupole doublets indicative of paramagnetic spin state. Sm3+ substituted compounds showed weak sextets in addition to broad doublets attributed to some particle magnetic moments in ordered magnetic phase. The Mössbauer spectra of the compounds annealed at 1100 °C exhibit magnetic split sextets indicative of ordered magnetic phase. The compounds have small coercive fields and high saturation magnetization (40 emu/g to 60 emu/g) which reduce with increasing Sm3+ content due to the paramagnetic nature of Sm3+ ions. Magnetic measurements as a function of field and temperature in as-prepared particles showed superparamagnetic behaviour with average moment of about ≈104μB. The average particle size obtained from the magnetic data corresponds well with that estimated from XRD analysis.

Assessing the structural, morphological and magnetic properties of polymer-coated magnesium-doped cobalt ferrite (CoFe2O4) nanoparticles for biomedical application

In this study, we have functionalised cobalt ferrite (CoFe2O4) nanoparticles (NPs) by doping with a natural bio-mineral magnesium (Mg) and coating with three polymers to enhance biocompatibility and feasibility for therapeutic applications. The glycol-thermal method was employed to synthesise CoFe2O4 and Mg0.5Co0.5Fe2O4 NPs. The latter NPs were functionalised with chitosan (CHI), poly-ethylene glycol (PEG) and poly-vinyl alcohol (PVA) to produce CHI-Mg0.5Co0.5Fe2O4, PEG-Mg0.5Co0.5Fe2O4 and PVA-Mg0.5Co0.5Fe2O4. The structure and morphology of NPs were characterized using transmission electron microscopy (TEM), high resolution TEM (HR-TEM), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy and nanoparticle tracking analysis (NTA). Magnetic measurements were carried out using a vibrating sample magnetometer (VSM). XRD patterns confirmed inverse cubic spinel phase structure typical of ferrite NPs. NPs exhibited spherical shape with average size diameters of ranging between 8 nm and 11 nm. Coating increased these average size diameters up to 13 nm. Zeta potential measurements indicated low colloidal stability of the NPs which improved considerably with PEG and PVA coating. FTIR confirmed surface modifications seen in additional peaks characterised by amine and carbonyl groups for chitosan and PEG/PVA, respectively. CoFe2O4 NPs exhibited high saturation magnetisations of 73.861 emu/g. This value decreased with magnesium-doping and polymer-coating due to shielding effect. In vitro cytotoxicity analysis demonstrated significant tolerability of coated Mg0.5Co0.5Fe2O4 NPs at concentrations of 800 μg/ml in cervical cancer (HeLa) cell lines. Conclusively, these polymer-coated ferrites present feasible nanocarriers in magneto-targeted drug delivery.

Surface-coating of Mg0.5Co0.5Fe2O4 nanoferrites and their in vitro cytotoxicity

Magnetic nanoparticles (MNPs) are attractive for biomedical applications, as contrast agents for magnetic resonance imaging, hyperthermia treatments, cell labelling, magneto-targeted therapy and drug delivery. Spinel ferrites represent a class of MNPs with unique optical, electrical and magnetic properties. In this study, we synthesized, characterized and evaluated the cytotoxicity of polymer-coated Mg0.5Co0.5Fe2O4 MNPs in human embryonic kidney (HEK293) and cervical carcinoma (HeLa) cells, to determine their future potential in drug/gene delivery. Mg0.5Co0.5Fe2O4 ferrites were synthesized via a glycol-thermal method, and functionalized with chitosan (CS), polyethylene glycol (PEG) and polyvinyl alcohol (PVA). The morphology and structure of all MNPs were characterized using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopy. Magnetic measurements at 14 kOe, confirmed the superparamagnetic nature of all MNPs, while XRD patterns confirmed typical single-phase cubic spinel structures with average crystallite size < 12 nm, which decreased upon coating. TEM and NTA displayed small, spherical particles, with some agglomeration, and improved colloidal stability (zeta potential > − 30 mV). In vitro cytotoxicity using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and sulforhodamine B (SRB) assays, confirmed moderate to low cytotoxicity in the HEK293 cells, with lower cell viability observed in the HeLa cells, supporting their use in biomedical applications.

Structural and Magnetic Studies of CoFe2 O 4 Ferrite, CoFe2 O 4/CoFe2 Nanocomposites and CoFe2 Nano-alloy

Nanoferrite of CoFe2 O 4 was synthesized using the glycol-thermal method at 200 ∘C for 6 h. The nanocomposites and nano-alloy were produced by the reduction of the ferrite using different amounts of activated charcoal at 900 ∘C for 3 h in high-purity flowing argon atmosphere. Complete reduction yields the nano-alloy phase while partial reduction produces the nanocomposites. XRD measurements of the nanoferrite showed a single-phase spinel structure with an average crystallite size of about 10 nm. The CoFe2 nano-alloy was obtained at an activated charcoal molar ratio of n C=6. The HRTEM of all the reduced samples showed clear differences. 57Fe Mossbauer spectra measurements of the reduced samples showed the transformation of the spinel structure to the composite and alloy phase. Mossbauer fits showed that Fe 3+ was reduced to Fe 2+ with lower magnetic hyperfine fields observed in the reduced samples. Magnetization measurements for reduced samples show significant enhancement. The coercivity of the fully reduced samples of the nanoferrite was observed to be less dependent on temperature.

Glycolthermal synthesis of Bi2MoO6 nanoplates and their photocatalytic performance

Bi2MoO6 nanoplates were successfully synthesized by a glycolthermal method at 160°C for 12h. Pure orthorhombic Bi2MoO6 nanoplates were characterized by X-ray diffraction, scanning electron microscopy and UV–visible absorption spectroscopy. The effect of reaction temperature and length of reaction time on phase and morphology of the as-synthesized products was investigated. The 2.75eV energy gap was investigated by UV−visible spectroscopy and was responsible for the photocatalysis. Photocatalytic performance of the Bi2MoO6 nanoplates evaluated through the degradation of rhodamine B under Xe light irradiation was 98.20% within 120min.

The Magnetic Properties of Mn0.3Mg0.2Zn0.5Fe2O4 and Mn0.3Mg0.2Co0.5Fe2O4: The Effect of Milling

Mn0.3Mg0.2Zn0.5Fe2O4 and Mn0.3Mg0.2Co0.5Fe2O4 nanoparticles with particle diameters of about 13nm were synthesized by glycol-thermal method. The as-prepared specimens were then milled at different times up to 50h and the single phase spinel structure confirmed by X-ray diffraction. The properties for the as-prepared and milled samples for the two systems were deduced and contrasted. Significant changes induced by milling in particle size, magnetization, coercive field and hyperfine parameters are reported. 57Fe Mössbauer spectra at room temperature show ordered magnetic spin states in both Mn0.3Mg0.2Zn0.5Fe2O4 and Mn0.3Mg0.2Co0.5Fe2O4 by magnetization measurements.

Synthesis, structural and magnetic properties of ZnxMg1−xFe2O4 nanoferrites

Abstract Zn x Mg 1 − x Fe 2 O 4 nanoparticles ( 0 ≤ x ≤ 1 in steps of 0.1) have been produced by centrifugation using the low temperature glycol-thermal method at 200 °C. Single-phase formation was confirmed by X-ray powder diffraction which revealed a well-defined cubic spinel structure with space group Fd3m. HRTEM and TEM were also used for the morphology studies. The crystallite size of the compounds ranged from 10.6 to 22.2 nm. A strong correlation was found between X-ray density and Zn-concentration, x . The magnetic properties as a function x were investigated by using 57 Fe Mossbauer spectroscopy, magnetization measurements using a Lakeshore vibrating sample magnetometer (VSM) at room temperature. We also report VSM measurement on a cryogen free measurement system at isothermal temperatures between 4 K and 300 K in external applied magnetic fields of up to 5 T. For x 0.8 , the room-temperature Mossbauer results show that the samples were transformed from paramagnetic state to magnetic ordered state. The temperature-dependences of saturation magnetization and coercive field follow the modified Bloch's law and Kneller's law, respectively. Strong correlation between saturation magnetization M S ( 0 ) and crystallite size D is observed. Two distinct composition ranges with Zn content are identified for which M S ( 0 ) variation with x is explained by the Neel and Yafet–Kittel models.

Structural and magnetic studies of (Mg, Sr)0.2Mn0.1Co0.7Fe2O4 nanoferrites

The (Mg, Sr)0.2Mn0.1Co0.7Fe2O4 nanoferrites were synthesized at low reaction temperature of 200°C using the glycol–thermal method. Single-phase cubic spinel structure and nanoparticle structure of the synthesized samples were confirmed by X-ray diffraction and high-resolution transmission electron microscope. The results show that the produced powders of the as-prepared samples have average crystallite size of about 8nm. The evolutions of the magnetic properties as a function of composition, annealing temperature (300–1000°C) under argon atmosphere or measuring temperature (4–300K) were investigated by 57Fe Mössbauer spectroscopy, vibration sample magnetometer and superconducting quantum interference device. The Mössbauer spectra indicate ferrimagnetic behavior of the compounds. Significant increase in coercive field with the reduction in measuring temperature is obtained for Sr0.2Mn0.1Co0.7Fe2O4 and Mg0.2Mn0.1Co0.7Fe2O4 which have large coercive fields of 3.02 and 10.70kOe at 4K respectively compared to about 0.05kOe at room temperature. The coercive fields and saturation magnetizations appear to vary with measuring temperature according to Kneller’s law and modified Bloch’s law respectively.

Magnetic properties of nanosized Mg0.5Mn0.5(RE)0.1Fe1.9O4 ferrites synthesized by glycol–thermal method

Nanosized Mg0.5Mn0.5(RE)0.1Fe1.9O4 ferrites, where RE are the rare earth elements, have been synthesized by the glycol–thermal method from pure metal chlorides. The as-prepared samples in the form of powders were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The XRD and HRTEM data show formation of the single-phase cubic spinel structure. The grain sizes are found in the range 9–15nm. Magnetic properties of the as-prepared samples were obtained at room temperature by 57Fe-Mössbauer spectroscopy and by a vibrating sample magnetometer. The distributions of Fe3+ ions were also deduced from Mössbauer measurements. The variations of grain size, lattice parameter, coercive field, magnetizations are presented as a function of the number of (RE)3+ 4f electrons. Our results show the evidence for superparamagnetic behavior of the rare earth substituted compounds. The highest grain size and magnetizations are obtained for the Gd substituted sample. We also find strong correlation of the saturation magnetizations, grain sizes and microstrains with the de Gennes factor.

Tetracycline-ferrite nanocomposites formed via high-energy ball milling and the influence of milling conditions

High-energy ball milling was used to mediate the formation of nanocomposites containing tetracycline and magnetic nanoparticles. Tetracycline-HCl was ball milled for 1, 3, 5, 15, and 30h under argon or air atmosphere with preformed Mg0.5Zn0.5Fe2O4 nanoferrites prepared by glycolthermal method. The structural, thermal, and magnetic properties of these novel materials and the effect of milling atmosphere on composition, crystallinity and cation distribution were then characterized by ICP-OES, DSC/TGA, XRPD, ATR-IR, UV–Vis and Mössbauer spectroscopy. Tetracycline underwent rapid and consecutive metal coordination events in the milling process to yield complexes characterized by bathochromic shifts in its electronic spectra and suppression of electronic absorbance at 365nm. Changes in stretching vibrations due to the A-ring carbonyl (1616cm−1), amide II nitrogen (1602cm−1), and CO bond (1039cm−1) indicate Mg-type interactions imposed on the metals. Exothermic oxidation of the drug at 235°C disappeared after 5h milling with the nanoferrites, and the composites formed remained thermostable up to 500°C. Tetracycline-nanoferrites (Tet-NF) are magnetic-ordered materials with a well-defined spinel-type structure. Analysis of the Mössbauer data suggests that the milling time and atmosphere have significant influence on cation distributions in Tet-NF composites.

Controlling morphologies of Bi2S3 nanostructures synthesized by glycolthermal method

Single crystalline orthorhombic Bi2S3 nanostructures with different morphologies were synthesized by the 180°C and 12h glycolthermal reactions, using ethylene glycol, propylene glycol and polyethylene glycol with different molecular weights as solvents. The as-synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). In the present research, different solvents played the role in the product morphologies. A formation mechanism of Bi2S3 nanostructures was also proposed.

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1−x Fe2O4 Ferrites Nanoparticles

Mn x Co1−x Fe2O4 ferrites compounds (0≤x≤0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13 nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700 °C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. 57Co Mossbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200 °C). Significant changes in magnetization properties and Mossbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.

Mössbauer and Magnetic Studies of Co0.5Mn0.5Fe2O4 and Mn0.1Mg0.2Co0.7 Fe2O4 Nanoferrites

We report the magnetic properties of Mn0.5Co0.5Fe2O4 and Mn0.1Mg0.2Co0.7Fe2O4 nanoferrites. The compounds were synthesized by a glycol-thermal method with average particle sizes of about 13 nm and 8 nm, respectively. The Mossbauer measurements were done at 300 K. The distribution of cations between tetrahedral (A) and octahedral (B) sites is investigated. The Mossbauer spectra indicate ferrimagnetic behavior of the compound. Field cooled (FC) and zero field cooled (ZFC) magnetizations were performed by a Superconducting Quantum Interference Device (SQUID) magnetometer from 4–380 K. Variation of the magnetizations with the applied fields (up to 50 kOe) were recorded at isothermal temperatures 4, 50, 100, 200 and 300 K. An increase in FC magnetization is observed with increasing applied field. This is explained based on superparamagnetic behavior of the particles.

Direct NO decomposition over a Ce–Mn mixed oxide modified with alkali and alkaline earth species and CO 2-TPD behavior of the catalysts

A Ce–Mn mixed oxide with the Mn/(Ce + Mn) molar ratio of 0.25 (designated as CeMn) was prepared by the glycolthermal method, and NO decomposition activities of CeMn modified with various species (alkali and alkaline earth species and noble metals) were examined. Although CeMn itself exhibited only a low activity for the direct decomposition of NO into N 2 and O 2, CeMn modified with alkali or alkaline earth species exhibited significant activities. The CO 2-TPD experiment indicated that the NO decomposition activity of the catalysts was correlated with their basicities. The highest NO conversion was achieved by a Ba/CeMn system. The NO conversion on the Ba/CeMn catalyst increased with increasing reaction temperature, and 67% of NO conversion was attained at 800 °C. This catalyst retained a high activity (50% at 800 °C) even in the presence of 5% CO 2 in the feed gas.