• Journal of Magnetics
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• 제20권3호
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• pp.246-251
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• 2015

This study was aimed to study the effect of Zn content on the hyperfine parameters and the structural variation of $Ni_{1-x}Zn_xFe_2O_4$ for x = 0, 0.2, 0.4, 0.6, and 0.8. To achieve this, a sol-gel route was used for the preparation of samples and the obtained ferrites were investigated by X-ray diffraction, scanning electron microscopy, and $M{\ddot{o}}ssbauer$ spectroscopy. The formation of spinel phase without any impurity peak was identified by X-ray diffraction of all the samples. Moreover, the estimated crystallite size by X-ray line broadening indicates a decrease with increasing Zn content. This result was in agreement with the scanning electron microscopy result, indicating the reduction in grain growth with further zinc substitution. The room-temperature $M{\ddot{o}}ssbauer$ spectra show that the hyperfine fields at both the A and B sites decreased with increasing Zn content; however, the rate of reduction is not the same for different sites. Moreover, the best fit parameter showed that the quadrupole splitting values of B site increased from the pure nickel ferrite to the sample with x = 0.8.

• 한국재료학회지
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• 제28권7호
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• 한국세라믹학회지
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• 제38권12호
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• pp.1162-1166
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• 2001

석유화학 공정 중 Styrene(SM) 공정에서 발생되는 산화철 폐촉매는 산업 폐기물로서 전량 매립되고 있는데, 이를 출발 원료로 사용하여 NiZn-페라이트를 합성하였고 그 자기적 특성을 조사하였다. 산화철 폐축매 펠렛을 분쇄한 후 NiO 및 ZnO를 혼합하여 90$0^{\circ}C$에서 하소하고 123$0^{\circ}C$에서 5시간 소결하여 스핀넬형 페라이트 소결체를 얻었다. N $i_{x}$ Z $n_{1-x}$F $e_2$ $O_4$(x=0.36, 0.50, 0.66)조성에 대하여 초투자율을 측정하였고, S-parameter를 측정하여 반사 감쇄량을 계산하였다. 산화철 폐촉매를 이용하여 X-band 주파수 영역에서 높은 전자파 흡수능을 갖는 전파흡수체를 제조할 수 있음을 확인하였다.다.

• 대한금속재료학회지
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• 제48권12호
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• pp.1090-1096
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• 2010

This pitting corrosion study of welded joints of austenitic stainless steels (AISI 304L and 316L) has addressed the differentiating solidification mode using three newly introduced filler wires with a flux-cored arc welding process (FCAW). The delta ferrite (${\delta}$-ferrite) content in the welded metals increased with an increasing equivalent weight ratio of chromium/nickel ($Cr_{eq}/Ni_{eq}$). Ductility dip cracking (DDC) was observed in the welded metal containing ferrite with none of AISI 304L and 0.1% of AISI 316L. The potentiodynamic anodic polarization results revealed that the $Cr_{eq}/Ni_{eq}$ ratio in a 3.5% NaCl solution didn't much affect the pitting potential ($E_{pit}$). The AISI 316L welded metals with ${\ddot{a}}$-ferrite content of over 10% had a superior $E_{pit}$ value. Though the AISI 316L welded metal with 0.1% ferrite had larger molybdenum contents than AISI 304L specimens, it showed a similar $E_{pit}$ value because the concentration of chloride ions and the corrosion product induced severe damage near the DDC.

• Corrosion Science and Technology
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• 제13권4호
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• pp.145-151
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• 2014

The objectives of this study are to investigate the effect of the concentration ratios of Ni and Fe ions on crud deposition onto the fuel cladding surface in the simulated primary environments of a pressurized water reactor. Crud deposition tests were conducted in the Ni and Fe concentration ratios of 20:20 ppm, 39:1 ppm and 1:39 ppm at $325^{\circ}C$ for 14 days. In the case of the same Ni and Fe ion ratio (20:20), nickel ferrite with a polyhedral shape was formed. Nickel oxide deposits with a needle shape were formed in the condition of high Ni to Fe ion ratio (39:1), While polyhedral iron oxide and needle-like nickel oxide formed in the condition of low Ni to Fe ion ratio (1:39). The amount of deposits increased, when Fe oxides were formed. This indicates that Fe rich oxides stimulated Ni oxide deposition.

• Corrosion Science and Technology
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• 제23권1호
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• pp.11-19
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• 2024

A Fe-Ni Bainitic steel as a weathering steel application was developed by combining its excellent mechanical properties and corrosion resistance in maritime environments. Nickel concentration (0.4-3 wt%) and inverted austempering multi-step (IAM) process were primary determinants of the microstructure of the Fe-Ni Bainitic steel. The initial austempering steel was performed at 300 ℃ for 600 seconds to obtain a partly bainitic transformation. The steel was heated again for 1800 s at 450 ℃. The microstructure was comprised of ferrite, a blocky martensite/austenite island, and a homogeneous lath-shape bainite structure with widths ranging from 4.67 to 6.89 ㎛. The maximum strength, 1480 MPa, was obtained with 3 wt% nickel. In this study, corrosion behavior was investigated utilizing potentiodynamic and electrochemical impedance spectroscopy (EIS) tests. A higher nickel content in Fe-Ni Bainitic steel refined the grain size, improved the bainite fraction, lowered the corrosion rate to 0.0257 mmpy, and increased the charge transfer of film resistance to 1369 Ω.

• 자원리싸이클링
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• 제9권2호
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• pp.11-17
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• 2000

니켈의 소비량은 계속 중가 추세에 있으며, 이와 함께 2차전지, 페라이트 페촉매는 사용 후의 폐기물이 연속적으로 발생하고 있다. 이들 중 본 연구에서는 Ni-Cd 2차전지 폐기물을 이용하여 니켈 회수를 수행하였다 폐전지의 구성은 니켈이 24wt% 칠이 30wt%, 카드뮴이 18.5wt%, 그리고 산소와 절연물 등으로 이루어져 있었다. 금속 회수의 방법은 침출 후 용매 추출법을 적용하였다. 염산침출에서는 1N 이상의 농도에서 카드뮴이 100% 침출되었고, 니켈은 20,000ppm이상 침출되어 70%이상의 침출율을 보였다. 산침출에서 얻은 침출액은 30vol%의 MSP-8로서 카드뮴만 추출하고 니켈은 잔류액으로 분리할 수 있었다. 그리고 암모늄염에 의한 침출에서는 $NH_4NO_3$에 의한 침출 시 니켈과 카드뮴만을 선택적으로 침출하는데 우수하였다. 질산암모늄에 의해 얻은 침출액 중의 Ni LIX계 추출제를 이용하여 100% 회수할 수 있었고, 잔류액 중의 카드뮴은 D2EHPA로 75% 이상 회수할 수 있었다.

• Journal of Magnetics
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• 제19권2호
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• pp.111-115
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• 2014

X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) were used to investigate the influence of Ni ions on the structural, electronic, and magnetic properties of nickel-ferrites ($Ni_xFe_{3-x}O_4$). Spinel $Ni_xFe_{3-x}O_4$ ($x{\leq}0.96$) samples were prepared as polycrystalline thin films on $Al_2O_3$ (0001) substrates, using a sol-gel method. XRD patterns of the nickel-ferrites indicate that as the Ni composition increases (x > 0.3), a structural phase transition takes place from cubic to tetragonal lattice. The XPS results imply that the Ni ions in $Ni_xFe_{3-x}O_4$ substitute for the octahedral sites of the spinel lattice, mostly with the ionic valence of +2. The minority-spin d-electrons of the $Ni^{2+}$ ions are mainly distributed below the Fermi level ($E_F$), at around 3 eV; while those of the $Fe^{2+}$ ions are distributed closer to $E_F$ (~1 eV below $E_F$). The magnetic hysteresis curves of the $Ni_xFe_{3-x}O_4$ films measured by VSM show that as x increases, the saturation magnetization ($M_s$) linearly decreases. The decreasing trend is primarily attributable to the decrease in net spin magnetic moment, by the $Ni^{2+}$ ($2{\mu}_B$) substitution for octahedral $Fe^{2+}$ ($4{\mu}_B$) site.

• 한국표면공학회지
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• 제50권3호
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.

• Journal of Magnetics
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• 제14권2호
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• pp.75-79
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• 2009

Nickel (Ni) and ferrite ($Fe_3O_4$, $NiFe_2O_4$) nanoparticles were synthesized by LGC using both wire feeding (WF) and micron powder feeding (MPF) systems. Phase evolution and magnetic properties were then investigated. The Ni nanopowder included magnetic-ordered phases. The LGC synthesis yielded spherical particles with large coercivity while the abnormal initial magnetization curve for Ni indicated a non-collinear magnetic structure between the core and surface layer of the particles. Since the XRD pattern cannot actually distinguish between magnetite ($Fe_3O_4$) and maghemite (${\gamma}-Fe_2O_3$) as they have a spinel type structure, the phase of the iron oxide in the samples was unveiled by $M{\ddot{o}}ssbauer$ spectroscopy. The synthesized Ni-ferrite consisted of single domain particles, including an unusual ionic state. The synthesized nanopowder bore an active surface due to the defects that affected abnormal magnetic properties.