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Abstract  

X-ray, magnetic and differential thermal analysis and thermogravimetric (DTA-TG) measurements of Fe2O3 nanoparticles surrounded by amorphous SiO2were carried out. The mass loss above 370 K could be attributed to the dehydration. The broadened exothermic peak around 900 K was observed by the DTA analysis. Considering the results of the X-ray and magnetic analyses, this anomaly was interpreted as due to the g- to a-transition in the present Fe2O3nanoparticle system. The broadness of the peak and thus the gradual progress of the transformation would be attributed to the stress caused by the amorphous SiO2 network surrounding extremely small particles.

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Summary Ni1-xZnxFe2O4 (0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2 were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tb were observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.

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Abstract

Cobalt nanoparticles were synthesized using continuous-flow (CF) chemistry in a stainless steel microreactor for the first time at high output based on the ethanol hydrazine alkaline system (EHAS) producing a yield as high as 1 g per hour [1, 2]. Continuous-flow (CF) synthetic chemistry provides uninterrupted product formation allowing for advantages including decreased preparation time, improved product quality, and greater efficiency. This successful synthetic framework in continuous-flow of magnetic Co nanoparticles indicates feasibility for scaled-up production. The average particle size by transmission electron microscopy (TEM) of the as-synthesized cobalt was 30±10 nm, average crystallite size by Scherrer analysis (fcc phase) was 15±2 nm, and the estimated magnetic core size was 6±1 nm. Elemental surface analysis (X-ray photoelectron spectroscopy [XPS]) indicates a thin CoO surface layer. As-synthesized cobalt nanoparticles possessed a saturation magnetization (M s) of 125±1 emu/g and coercivity (H c) of 120±5 Oe. The actual M s is expected to be greater since the as-synthesized cobalt mass was not weight-corrected (nonmagnetic mass: reaction by-products, solvent, etc.). Our novel high-output, continuous-flow production (>1 g/hr) of highly magnetic cobalt nanoparticles opens an avenue toward industrial-scale production of several other single element magnetic nanomaterials.

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Journal of Thermal Analysis and Calorimetry
Authors: J. R. Azevedo, R. H. Sizilio, M. B. Brito, A. M. B. Costa, M. R. Serafini, A. A. S. Araújo, M. R. V. Santos, A. A. M. Lira and R. S. Nunes

with other crosslink agents [ 4 ]. These features make it an interesting target in drug delivery systems. Chitosan/tripolyphosphate (TPP) nanoparticles prepared by ionotropic gelation method have been increasingly studied for controlled

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Journal of Thermal Analysis and Calorimetry
Authors: N. Ivashchenko, V. Tertykh, V. Yanishpolskii, J. Skubiszewska-Zięba, R. Leboda and S. Khainakov

Introduction Preparation of metal nanoparticles is a field of current interest in material chemistry because of possible emerging of new physical and chemical properties when the particle sizes approach the nanometer range [ 1

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Journal of Thermal Analysis and Calorimetry
Authors: Eudes Lorençon, Rodrigo G. Lacerda, Luiz O. Ladeira, Rodrigo R. Resende, André S. Ferlauto, Ulf Schuchardt and Rochel M. Lago

Introduction Carbon nanotubes (CNTs) have been intensely investigated due to their unique chemical, mechanical, and electrical behavior. The inherent properties of CNTs make them versatile supports for metallic nanoparticles

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Acta Physiologica Hungarica
Authors: Teodora Mocan, S. Clichici, L. Agoşton-Coldea, L. Mocan, Ş Şimon, I. Ilie, A. Biriş and Adriana Mureşan

Apopa P, Qian Y, Shao R, Guo NL, Schwegler-Berry D, Pacurari M, Porter D, Shi X, Vallyathan V, Flynn D: Iron oxide nanoparticles induce human microvascular endothelial cell permeability through reactive oxygen

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Journal of Thermal Analysis and Calorimetry
Authors: Rabia Nazir, Muhammad Mazhar, Tehmina Wakeel, Muhammad J. Akhtar, Muhammad Siddique, Muhammad Nadeem, Nawazish A. Khan and Muhammad R. Shah

investigations on mechanism of pyrolysis of anhydrous trisbipyridineiron(II) chloride under controlled temperature and ambient pressure and characterization of the residual mass and found that the complex degrades to iron nanoparticles under given conditions

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capability of decomposing a wide variety of organics [ 1 , 2 ]. Controlled synthesis and characterization of nanoparticles is rapidly becoming a very important research area due to their unique shape and size-dependent properties [ 3 , 4 ]. When the size of

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improved, different types of these nanoparticles have been produced. SiO 2 nanoparticle, TiO 2 nanoparticle, and Al 2 O 3 nanoparticle are the most important pigments among these. ZnO nanoparticles, due to the excellent properties which could produce

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