VSM Characterization Research Articles

Synthesis of finest superparamagnetic carbon-encapsulated magnetic nanoparticles by a plasma expansion method for biomedical applications

This paper demonstrates fine size-controlled synthesis of superparamagnetic carbon-encapsulated iron nanoparticles, by a supersonic plasma jet assisted rapid, bulk-production process, by manipulation of the pressure in the sample collection chamber. Transmission electron microscopy and small angle x-ray scattering measurements confirmed the formation of single-crystals with a narrow size distribution, having core average size of 5.0 nm and encapsulated by an ultrathin carbon coating, for sub-mbar pressure. VSM and Mossbauer characterization established the nanocrystallites to be superparamagnetic in nature, with saturation magnetization 67 emu/g and coercive field 7.4 Oe. Controlled plasma heating during synthesis led to the burning down of extra carbon that resulted in further enhancement of the magnetization of the product. Graphitization of the encapsulating layers also enhanced, which could successfully protect the metallic core from oxidation, as well as improved its cyto-compatibility. This purified sample could be ideal for targeted drugs delivery and water treatment applications. Another sample was processed through controlled reaction with oxygen, the as-synthesized sample having magnetic properties approaching that of the first sample, which may be more attractive especially for water treatment processes because of the simpler single-step processing of the material.

A new synthesis of SmCo5 particles with high magnetic performance through spray pyrolysis

SmCo5 particles were synthesized by a spray pyrolysis process with in situ hydrogen (H2) reduction. The as-synthesized particles showed homogenous elemental distribution and low crystallization. The crystallization of the as-synthesized SmCo5 particles was further increased by annealing at 700 °C in Ar environment. After the annealing, the SEM images showed that surface roughness of the particles was increased due to the reordering of the atoms, the XRD patterns showed that the crystallization of the particles was increased, and VSM characterization showed that the magnetic properties were improved. Finally, the magnetic properties of SmCo5 particles synthesized in this report were compared with those in other reports. It was concluded that this paper proposed an easy way to synthesize high purity SmCo5 particles with high magnetic performance.

Enhanced Cr(VI) removal from acidic solutions using biochar modified by Fe3O4@SiO2-NH2 particles

Fe3O4@SiO2-NH2 magnetic particles with core-shell structure were attached on carboxylated biochar derived from phoenix tree leaves to synthesize a novel magnetic biochar for removing Cr(VI) ions from acidic solutions. FSEM, FTEM, XRD characterizations of the synthesized magnetic biochar revealed that the Fe3O4@SiO2-NH2 magnetic particles distributed uniformly on the surface or macrospores of carboxylated biochar by strong chemical bonding. The Cr(VI) ions adsorption capacity of magnetic biochar was 27.2mg·g−1, surpassing original carboxylated biochar (18.2mg·g−1). VSM and XPS characterizations demonstrated that the attached Fe3O4@SiO2-NH2 magnetic particles not only endowed biochar with perfect magnetic property (23emu·g−1) but also provided complexing sites for binding Cr(III) cations reduced from Cr(VI) anions. The Cr(VI) ions removal by magnetic biochar contained three steps: (1) adsorption of Cr(VI) anions by protonated functional groups; (2) reduction of Cr(VI) anions to Cr(III) cations by electron-donor groups; and (3) chelation of Cr(III) cations by amine groups. The adsorption recycling test showed that magnetic biochar kept 85% of its initial Cr(VI) adsorption capacity at the sixth cycle, and the Fe leakage under pH1.0 was smaller than 0.25mg·L−1. The results indicated that this novel magnetic biochar was applicable for the practical treatment of Cr(VI)-containing wastewater.

Properties of [formula omitted]/graphene nanohydrid synthesized by a simple hydrothermal/solution mixing method

α-Fe2O3/graphene nanohybrid with different graphene nanosheets (GN) compositions are prepared by a simple hydrothermal/solution mixing method. The XRD patterns reveal that α-Fe2O3 nanoparticles (NP’S) are successfully anchored on the GNs. Suppression of Fe signal and increase of C signal are evidenced from EDX spectra. TEM images show that the as prepared nanohybrids have packed structure of NP’S on GNs with some voids. Vibrational bands in the FTIR studies confirm the fabrication of α-Fe2O3/GNs nanohybrids. DRUV spectra suggest that band gap reduces from 1.74(2) to 1.47(5) with GNs composition. VSM characterization reveals that saturation magnetization shifts toward field axis, while Morin transition temperature increases with GNs composition.

Evolution of structural and magnetic phases in Nd doped BiFeO3 multiferroics with sintering time

The effect of sintering time on the evolution of structural and magnetic phases has been studied in Bi0.8Nd0.2FeO3 multiferroic. These multiferroics were prepared by normal solid state reaction technique. XRD, NPD and VSM characterizations were performed to explore the structural and magnetic properties and correlation between these. The refinement of the XRD patterns using FullProf program show, mixed phase having rhombohedral (R3c)+orthorhombic (Pnma) symmetry in sample sintered for 1h. For sample sintered for two hours, crystal structure was found to be mixed phase with rhombohedral (R3c)+orthorhombic (Pbam) symmetry and the sample sintered for three hours, it crystallized in pure orthorhombic (Pbam) symmetry. The octahedral tilting is thus found to be changing systematically with the variation of sintering time. The refinement of the neutron diffractions patterns confirms the XRD results of structural evolution with sintering time. The magnetic moment undergoes change in the direction of their preferential alignment from c-axis to along a-axis in the 3h sintered sample. The M-H loops shows significant enhancement in magnetization from 0.17455emu/g to 0.35872emu/g with increase in sintering time from 1 to 3h. The enhancement in the magnetization is attributed to increase in the canting angle between magnetic spins. Also, the observation of exchange bias effect with discontinuous variation in exchange bias field indicates the presence of magnetic anisotropy. The magnetic moments obtained through the magnetic refinement of NPD patterns are found to decrease from 4.6 μB to 3.8 μB with increase in sintering time from 1 to 3h.

A spray pyrolysis synthesis of MnFe2O4/SnO2 yolk/shell composites for magnetically recyclable photocatalyst

The MnFe2O4/SnO2 yolk/shell structured composites were synthesized through an organics assisted spray pyrolysis process. The yolk/shell structure of as-synthesized particles was confirmed by both SEM and TEM, indicating that solid MnFe2O4 particle was captured inside a hollow SnO2 particle. The crystallization was investigated by XRD, which confirmed the existence of both SnO2 and MnFe2O4 phases. The VSM characterization showed that the yolk/shell structure had good magnetic properties. The photocatalytic performance of MnFe2O4/SnO2 yolk/shell particles was investigated through a methyl orange degradation reaction under UV irradiation. The stability of the particles was also investigated by running the reactions in four cycles.

A novel approach to preparing polystyrene/Fe3O4 multihollow microspheres with porous walls

A novel approach is presented here to prepare polystyrene/Fe3O4 multihollow microspheres with porous walls. Water-in-oil-in water (W/O/W) double emulsion was developed in mini-emulsion system with the help of amphipathic Fe3O4 nanoparticles dispersed in oil phase. A γ-ray irradiation from 60Co source initiated the radical polymerization and controlled the reaction degree. Most of polymerization took place in mini-droplets of monomer developed during mini-emulsification process. Therefore, every mini-droplet of monomer with water inside can act like soft template, and polymerization helps to solidify such soft template and successfully reserve and transfer the morphology of these water-in-oil mini-droplets to solid microspheres. Multihollow structure was developed after drying since water inside of microspheres evaporated. Superparamagnetic property was also confirmed by VSM characterization on nanocomposites. Finally, the mechanism of forming such structure was preliminarily elucidated.

Effect of Ba+2 ion on structural, magnetic and microwave properties of screen printed BaxSr1-XFe12O19 thick films

The present paper reports the structural, magnetic and microwave properties of screen printed thick films of BaxSr1-XFe12O19 (BSF) (x = 0.0–1.0) synthesized via simple auto combustion technique followed by screen printing technique. The samples were characterized for various characterizations such as XRD, SEM, FT-IR, Micro-Raman, and VSM and microwave characterization. The X-ray diffraction patterns show that formations of hexagonal crystal structure with crystallite in the range 41.55 to 55.44 nm. The FT-IR and Micro-Raman spectroscopy also supports to the formation of hexagonal crystal structure with P63mmc space group. The surface morphology clearly reveals the distribution of Ba+2 ions on the surface of strontium hexaferrite. The substitution of Ba+2 ions strongly affect the saturation magnetization and microwave properties of barium strontium hexaferrite. The 60% Ba+2 ion substituted film shows maximum crystallite size of 55.44 nm and it shows highest magnetic moment of 76.62 emu/gm. The BSF thick films show broad band microwave absorption in the 8–18 GHz frequency range for all the compositions with a maximum of around 68% for the 60% Ba+2 ion substituted film.

Magnetic MSP@ZrO₂ microspheres with yolk-shell structure: designed synthesis and application in highly selective enrichment of phosphopeptides.

Magnetic yolk-shell MSP@ZrO2 microspheres consisting of a movable magnetic supraparticle (MSP) core and a crystalline ZrO2 shell were synthesized via a two-step controlled "sol-gel" approach for the first time. First, a large amount of the generated hydrolyzate Zr(OH)4 was firmly fixed onto the surface of the cross-linked polymethylacrylic acid matrix via a strong hydrogen-bonding interaction between Zr(OH)4 and the carboxyl groups. Then a calcination process was adopted to convert the Zr(OH)4 into a continuous ZrO2 shell and simultaneously make the ZrO2 shell crystallized. At the same time, the polymer matrix could be selectively removed to form a yolk-shell structure, which has better dispersibility and higher adsorbing efficiency of phosphopeptides than its solid counterpart. The formation mechanism of such yolk-shell microspheres could be reasonably proved by the results of TEM, TGA, VSM, XRD, and FT-IR characterization. By taking advantage of the unique properties, the yolk-shell MSP@ZrO2 exhibited high specificity and great capability in selective enrichment of phosphopeptides, and a total of 33 unique phosphopeptides mapped to 33 different phosphoproteins had been identified from 1 mL of human saliva. This result clearly demonstrated that the yolk-shell MSP@ZrO2 has great performance in purifying and identifying the low-abundant phosphopeptides from real complex biological samples. Moreover, the synthetic method can be used to produce hybrid yolk-shell MSP@ZrO2-TiO2.

Preparation of novel magnetic hollow mesoporous silica microspheres and their efficient adsorption

Magnetic hollow mesoporous silica microspheres (MHMSs) were successfully prepared by employing yolk-shell magnetic silica spheres as the template together with the coating of tetraethoxysilane (TEOS)/hexadecyl trimethoxysilane (C16TMS) hybrid. The microstructure and properties of MHMSs were studied by TEM, SEM, XRD, BET, and VSM characterizations. The average diameter of MHMSs was about 300nm and the mesoporous shell thickness was totally around 70nm. The 11nm magnetite nanoparticles were homogeneously embedded in the mesoporous silica shell. Meanwhile, the adsorption and separation process of Rhodamine B were carried out to demonstrate that the material could be used for the adsorbent.

Carbon Combustion Synthesis and Magnetic Properties of Cobalt Ferrite Nanoparticles

Cobalt ferrite CoFe2O4 crystalline nanoparticles (50-100 nm) were produced by carbon combustion synthesis of oxides (CCSO). In this combustion synthesis process, the exothermic oxidation of carbon generates a thermal reaction wave that propagates through the solid reactants mixture of CoO and Fe2O3 converting it to cobalt ferrite. The extensive emission of CO2 increased the porosity and friability of the product. The quenching front method combined with XRD and VSM characterization revealed that crystalline CoFe2O4 particles formed in the early stage of the combustion, before the temperature reached its maximum. The maximum value of the coercivity of the quenched product within the front region was 940 Oe with a magnetization of 15 emu/g. The as-synthesized ferrites had hard magnetic properties with coercivity of 700 Oe and saturation magnetization of up to 47 emu/g