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RISS 인기검색어
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- 저자 : Mirjana Jovicic (검색결과 2 건)
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Modification of Cellulose and Rutile Welding Electrode Coating by Infiltrated TiO2 Nanoparticles
Sebastian Balos,Leposava Sidjanin,Miroslav Dramicanin,Danka Labus,Branka Pilic,Mirjana Jovicic 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3
In this paper, a novel method of infiltration of TiO2 nanoparticles into the coating of the cellulose and rutile shielded metal arc welding electrode is shown. Tensile properties and strength of weld metals were correlated to the chemical composition of the weld metals, ferrite type, and non-metallic inclusion type, size and composition. As infiltration time is increased in the cellulose electrodes, the non-metallic inclusion count increases and their size decreases. They act as inoculants and lead to the replacement of Widmanstaetten with the finegrained acicular ferrite which increases the mechanical properties of the welds. The modification of rutile electrodes with low and medium infiltration time also refines the microstructure and increases the mechanical properties. Specimens welded with rutile electrodes infiltrated at maximum duration exhibited the lowest mechanical properties due to the relatively large non-metallic inclusions that act as void nucleation sites and the appearance of large grain allotriomorphic ferrite in the weld metal.
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Ultrasmall iron oxide nanoparticles: Magnetic and NMR relaxometric properties
Branka Babic-Stojic,Vukoman Jokanovic,Dusan Milivojevic,Miroslav Pozek,Zvonko Jaglicic,Darko Makovec,Natasa Jovic Orsini,Mirjana Markovic,Katarina Arsikin,Verica Paunovic 한국물리학회 2018 Current Applied Physics Vol.18 No.2
Ultrasmall iron oxide (USPIO) nanoparticles, with diameter mostly less than 3 nm dispersed in an organic carrier fluid were synthesized by polyol route. The evolution of ZFC-FC magnetization curves with temperature, as well as the shift of the ac susceptibility peaks upon changing the frequency, reveal that the nanoparticles in the fluid are non-interacting and superparamagnetic with the blocking temperature TB ~10 K. The M€ossbauer spectra analysis proposed the core/shell structure of the nanoparticles consisting of stoichiometric g-Fe2O3 core and non-stoichiometric shell. The nanoparticle surface layer has a great influence on their properties which is principally manifested in significant reduction of the magnetization and in a large increase in magnetic anisotropy. Magnetic moments do not saturate in fields up to 5 T, even at the lowest measured temperature, T ¼ 5 K. The average magnetic particle diameter is changed from 1.3 to 1.8 nm with increasing magnetic field from 0 to 5 T which is noticeably smaller than the particle sizes measured by TEM. The estimated effective magnetic anisotropy constant value, Keff ¼ 2 105 J/m3, is two orders of magnitude higher than in the bulk maghemite. Measurements of the longitudinal and transverse NMR relaxivity parameters on water diluted nanoparticle dispersions at 1.5 T gave the values r1 ¼ 0.028 mmol1 s1, r2 ¼ 0.050 mmol1 s1 and their ratio r2/r1 ¼ 1.8. Continuous increase of the T1-weighted MRI signal intensity with increasing Fe concentration in the nanoparticle dispersions was observed which makes this ferrofluid to behave as a positive T1 contrast agent.
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