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Research paper thumbnail of Synthesis of coprecipitated strontium hexaferrite nanoparticles in the presence of polyvinyl alcohol

Journal of Magnetism and Magnetic Materials, 2011

Strontium hexaferrite (SrFe12O19) nanoparticles were synthesized by the chemical coprecipitation ... more Strontium hexaferrite (SrFe12O19) nanoparticles were synthesized by the chemical coprecipitation method and using polyvinyl alcohol (PVA) as a protective agent. The synthesized samples were characterized by differential thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, particle size analyzer, sedimentation test and vibrating sample magnetometer. In the presence of PVA, the single-phase SrFe12O19 nanoparticles were obtained at low temperature of 650°C. The average particle size of SrFe12O19 precursor was 15nm, which increased to 61nm after calcination at 650°C. The magnetic measurements indicated that PVA decreased coercivity from 4711 to 3216Oe with particle size reduction. The results showed that PVA as a protective agent could be effective in decreasing the particle size, calcination temperature and coercivity of SrFe12O19 nanoparticles.

Research paper thumbnail of Magnetic properties of Sn–Mg substituted strontium hexaferrite nanoparticles synthesized via coprecipitation method

Journal of Alloys and Compounds, 2011

Nanoparticles of Sn-Mg substituted strontium hexaferrite with the composition of SrFe 12−x (Sn 0.... more Nanoparticles of Sn-Mg substituted strontium hexaferrite with the composition of SrFe 12−x (Sn 0.5 Mg 0.5 ) x O 19 (x = 0.0-1.0) were synthesized by chemical coprecipitation method. Deionized water/ethanol (50/50) was used as the solvent. The single phase strontium hexaferrites were obtained at pH 13 and Fe 3+ /Sr 2+ molar ratio of 9 after calcination at 800 • C. The mean particle size of samples was decreased from 82 to 56 nm with increasing the Sn-Mg content from x = 0.0 to x = 0.8. The effect of Sn-Mg substitution on magnetic properties of hexaferrites was studied using vibrating-sample magnetometer. It was found that increasing the Sn-Mg from x = 0.0 to x = 0.8 reduced the coercivity from 4728.9 to 1455.5 Oe and increased the saturation magnetization from 51.34 to 65.49 emu/g. A vector network analyzer was used to investigate the microwave absorption properties. According to microwave measurements, doped strontium hexaferrite composites had much more effective electromagnetic absorption properties than undoped strontium hexaferrite composite.

Research paper thumbnail of Investigation of the effective parameters on the synthesis of strontium hexaferrite nanoparticles by chemical coprecipitation method

Journal of Alloys and Compounds, 2012

In this work, synthesis of nanostructured NiFe 2 O 4 powders by coprecipitation method using nove... more In this work, synthesis of nanostructured NiFe 2 O 4 powders by coprecipitation method using novel precursors, followed by calcination was investigated for the first time. The synthesis was started by dissolving Fe and Ni chlorides and ammonium ferrous sulfate in deionized water. After stirring, the precipitating agent of NaOH was added to the solution and after 1 h aging, the resultant precipitates were washed with deionized water and acetone. Then the powder was characterized and the effects of different parameters such as molarity of precipitant, calcination temperature and the molar ratio of Ni 2+ ion to the total iron ions were studied. It is concluded that an increase in molarity of precipitant can decrease the calcination temperature. The best conditions giving a single phase Ni-ferrite were using of 2.2 molar NaOH, calcination temperature of 900°C and the molar ratio of nickel to iron as 0.5. The crystallite size of resulting ferrites was below 50 nm.

Research paper thumbnail of New High-Resolution Solution for Measuring Degree of Sensitization of Duplex Stainless Steel 2205 Using Double-Loop Electrochemical Potentiodynamic Reactivation Technique

Corrosion, 2013

ABSTRACT In the present work, a new high-resolution solution for measuring degree of sensitizatio... more ABSTRACT In the present work, a new high-resolution solution for measuring degree of sensitization (DOS) of duplex stainless steel (DSS) 2205 (UNS S31803) by double loop-electrochemical potentiodynamic reactivation (DL-EPR) technique was obtained and the solution parameters were optimizing using the Taguchi method. Sensitized samples in three different conditions were chosen and five solution main factors including acid and two types of depassivator concentrations, scan rate, and surface roughness were considered. To reduce the number of experiments, Taguchi orthogonal array (OA) was used. The resulting optimal condition was to be 0.5 M sulfuric acid (H2SO4), 0.002 M sodium thiosulfate (Na2S2O3), 0.02 M sodium chloride (NaCl), and 120 grid in surface roughness and 30 mV/min scan rate. By introducing the new solution, a DOS value of 78% was obtained in the DSS2205 sample sensitized at 850 degrees C for 40 min. Moreover, topography variations of non-sensitized and sensitized samples measured by atomic force microscopy elucidated the mechanism of austenite/ferrite boundary attack and carbide precipitates formation in sensitized samples extended to the ferrite phase.

Research paper thumbnail of Synthesis of coprecipitated strontium hexaferrite nanoparticles in the presence of polyvinyl alcohol

Journal of Magnetism and Magnetic Materials, 2011

Strontium hexaferrite (SrFe12O19) nanoparticles were synthesized by the chemical coprecipitation ... more Strontium hexaferrite (SrFe12O19) nanoparticles were synthesized by the chemical coprecipitation method and using polyvinyl alcohol (PVA) as a protective agent. The synthesized samples were characterized by differential thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, particle size analyzer, sedimentation test and vibrating sample magnetometer. In the presence of PVA, the single-phase SrFe12O19 nanoparticles were obtained at low temperature of 650°C. The average particle size of SrFe12O19 precursor was 15nm, which increased to 61nm after calcination at 650°C. The magnetic measurements indicated that PVA decreased coercivity from 4711 to 3216Oe with particle size reduction. The results showed that PVA as a protective agent could be effective in decreasing the particle size, calcination temperature and coercivity of SrFe12O19 nanoparticles.

Research paper thumbnail of Magnetic properties of Sn–Mg substituted strontium hexaferrite nanoparticles synthesized via coprecipitation method

Journal of Alloys and Compounds, 2011

Nanoparticles of Sn-Mg substituted strontium hexaferrite with the composition of SrFe 12−x (Sn 0.... more Nanoparticles of Sn-Mg substituted strontium hexaferrite with the composition of SrFe 12−x (Sn 0.5 Mg 0.5 ) x O 19 (x = 0.0-1.0) were synthesized by chemical coprecipitation method. Deionized water/ethanol (50/50) was used as the solvent. The single phase strontium hexaferrites were obtained at pH 13 and Fe 3+ /Sr 2+ molar ratio of 9 after calcination at 800 • C. The mean particle size of samples was decreased from 82 to 56 nm with increasing the Sn-Mg content from x = 0.0 to x = 0.8. The effect of Sn-Mg substitution on magnetic properties of hexaferrites was studied using vibrating-sample magnetometer. It was found that increasing the Sn-Mg from x = 0.0 to x = 0.8 reduced the coercivity from 4728.9 to 1455.5 Oe and increased the saturation magnetization from 51.34 to 65.49 emu/g. A vector network analyzer was used to investigate the microwave absorption properties. According to microwave measurements, doped strontium hexaferrite composites had much more effective electromagnetic absorption properties than undoped strontium hexaferrite composite.

Research paper thumbnail of Investigation of the effective parameters on the synthesis of strontium hexaferrite nanoparticles by chemical coprecipitation method

Journal of Alloys and Compounds, 2012

In this work, synthesis of nanostructured NiFe 2 O 4 powders by coprecipitation method using nove... more In this work, synthesis of nanostructured NiFe 2 O 4 powders by coprecipitation method using novel precursors, followed by calcination was investigated for the first time. The synthesis was started by dissolving Fe and Ni chlorides and ammonium ferrous sulfate in deionized water. After stirring, the precipitating agent of NaOH was added to the solution and after 1 h aging, the resultant precipitates were washed with deionized water and acetone. Then the powder was characterized and the effects of different parameters such as molarity of precipitant, calcination temperature and the molar ratio of Ni 2+ ion to the total iron ions were studied. It is concluded that an increase in molarity of precipitant can decrease the calcination temperature. The best conditions giving a single phase Ni-ferrite were using of 2.2 molar NaOH, calcination temperature of 900°C and the molar ratio of nickel to iron as 0.5. The crystallite size of resulting ferrites was below 50 nm.

Research paper thumbnail of New High-Resolution Solution for Measuring Degree of Sensitization of Duplex Stainless Steel 2205 Using Double-Loop Electrochemical Potentiodynamic Reactivation Technique

Corrosion, 2013

ABSTRACT In the present work, a new high-resolution solution for measuring degree of sensitizatio... more ABSTRACT In the present work, a new high-resolution solution for measuring degree of sensitization (DOS) of duplex stainless steel (DSS) 2205 (UNS S31803) by double loop-electrochemical potentiodynamic reactivation (DL-EPR) technique was obtained and the solution parameters were optimizing using the Taguchi method. Sensitized samples in three different conditions were chosen and five solution main factors including acid and two types of depassivator concentrations, scan rate, and surface roughness were considered. To reduce the number of experiments, Taguchi orthogonal array (OA) was used. The resulting optimal condition was to be 0.5 M sulfuric acid (H2SO4), 0.002 M sodium thiosulfate (Na2S2O3), 0.02 M sodium chloride (NaCl), and 120 grid in surface roughness and 30 mV/min scan rate. By introducing the new solution, a DOS value of 78% was obtained in the DSS2205 sample sensitized at 850 degrees C for 40 min. Moreover, topography variations of non-sensitized and sensitized samples measured by atomic force microscopy elucidated the mechanism of austenite/ferrite boundary attack and carbide precipitates formation in sensitized samples extended to the ferrite phase.

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