• Resources Recycling
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• v.12 no.4
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• pp.30-37
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• 2003

A kinetics study on the dissolution reaction of zinc-ferrite has been made with aqueous sulfuric acid in various temperature and concentration. Fraction reacted(R) and apparent rate constant(K) increased with increasing temperature and concentration of sulfuric acid solution. The rate of dissolution is shown by $1-(1-K)^{1/3}=Kt$ for the initial stage of the reaction in aqueous sulfuric acid, where K is apparent rate constant, R is fraction reacted and t is reaction time, respectively. Activation energy associated with reaction was determined to be 16.3 kcal/mole. The dissolution of zinc-ferrite in sulfuric acid solution is dissolved by sto-ichiometric composition, but Fe and Zn did not dissolved, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.971-972
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• 2006

Mechanochemical synthesis of zinc ferrite, $ZnFe_2O_4$, was attempted from a powder mixture of iron (III) oxide, alpha-$Fe_2O_3$ and zinc (II) oxide, ZnO. Nanocrystalline zinc ferrite, $ZnFe_2O_4$ powders were successfully synthesized only bymilling for 30 hours. Evidence of the $ZnFe_2O_4$ formation was absent for the powders milled for 10 and 20 hours; the milling lowered the crystallinity of the starting materials. Heating after milling enhanced the formation of $ZnFe_2O_4$, crystal growth of $ZnFe_2O_4$ and the unreacted starting materials. The unreacted starting materials decreased their amounts by heating at higher temperatures.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.351-356
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• 1997

The origin of the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was investigated. Initial permeability showed maximum with hematite content while there was no significant change in microstructure. Saturation magnetization increased with hematite content. So the variation of initial permeability was not explained on the basis of microstructural change or saturation magnetization. Temperature dependence of initial permeability revealed magnetocrystalline anisotropy was the origin of the variation of initial permeability. The change in magnetocrystalline anisotropy was ascribed to the variation in ferrous ion concentration. Therefore the variation of initial permeability in manganese-zinc ferrite polycrystals with a content of hematite was due to ferrous ion concentration via magnetocrystalline anisotropy.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.703-709
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• 2006

We report on the synthesis of highly uniform, single phase zinc and cobalt thin films prepared by the Liquid Phase Deposition (LPD) method. X-Ray diffraction, TGA and EDX measurements support the assumption that the as deposited films are constituted by a mixture of crystallized FeOOH and amorphous M(OH)$_2$ (M=Co, Zn) which is converted upon heat treatment in air at 600?C into the corresponding zinc ferrites. The films with adjustable chemical compositions are identified with a crystal structure as spinel-type and present a spherical or rod-like microstructure, depending on the both the nature and concentration of the divalent transition metal ions. Zinc ferrite thin films present a superparamagnetic behavior above blocking temperatures which decrease with increasing the Zn content and are ferromagnetic at 5 K with coercivities ranging between 797.8 and 948.5 Oe, whereas the cobalt ferrite films are ferromagnetic at room temperature with magnetic characteristics strongly dependent on the chemical composition.

• Journal of Environmental Health Sciences
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• v.17 no.1
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• pp.39-49
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• 1991

고온에서 황화수소(H$_{2}$S)를 제거하기 위한 흡착제를 개발할 목적으로 ZnO에 $Fe_{2}O_{3}$를 5~50 atomic %까지 첨가시켜 제조한 다공성 흡착제와 황화수소와의 반응(sulfidation)을 thermogravimetric analyzer (Shimadzu DT-30)로 수행하였으며, 고정층세서 zinc ferrite 흡착제의 흡착능을 측정하였다. 반응온도는723$^{\circ}$K~973$^{\circ}$K범위이며, 반응기체는 황화수소(2vol.%)와 질소와 혼합기체로서 total gas flow rate는 200ml/min으로 고정시켰다. Grain Model을 사용하여 실험데이터를 분석한 결과 전화율이 낮을 때 zinc ferrite와 황화수소 반응의 율속단계는 화학반응이었고 황화수소 농도에 대해 1차 반응이었다. 실험한 흡착제 중 10 atomic %의 $Fe_{2}O_{3}$를 첨가하여 제조한 zinc ferrite형 흡착제가 반응속도, 흡착능, 그리고 재생성면에서 우수한 흡착제로 밝혀졌다.

• Advances in nano research
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• v.13 no.5
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• pp.437-451
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• 2022

Synthesis approaches usually affect the physical and chemical properties of ferrites. This helps ferrite materials to design them for desired applications. Some of these methods are mechanical milling, ultrasonic method, micro-emulsion, co-precipitation, thermal decomposition, hydrothermal, microwave-assisted, sol-gel, etc. These methods are extensively reviewed by taking example of ZnFe₂O₄. These methods also affect the microstructure and local structure of ferrite which ultimately affect the physical and chemical properties of ferrites. Various spectroscopic techniques such as Raman spectroscopy, Fourier Transform Infrared spectroscopy, Ultra Violet-Visible spectroscopy, Mossbauer spectroscopy, extended x-ray absorption fine structure, and electron paramagnetic resonance are found helpful to reveal this information. Hence, the basic principle and the usefulness of these techniques to find out appropriate information in ZnFe₂O₄ nanoparticles is elaborated in this review.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.71-75
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• 2007

Ultrasonic irradiation in a solution during the chemical reaction may accelerate the rate of the reaction and the crystallization at low temperature. We have synthesized nanometer sized zinc ferrite particles using chemical co-precipitation technique through a sonochemical method with surfactant such as oleic acid. The thermal behaviour of the zinc ferrite was determined by the thermoanalytical techniques (TGA-DSC). Powder X-ray diffraction measurements show that the samples have the spinel structure. Magnetic properties measurement were performed using a superconducting quantum interference device (SQUID) magnetometer.

• Resources Recycling
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• v.17 no.1
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• pp.66-72
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• 2008

Fundamental studies for the synthesis of Mn-Zn ferrite powder were investigated using a series of leaching and coprecipitation processes from spent alkaline manganese batteries. Zinc and Manganese dissolution rates obtained at the reaction conditions of 100g/L pulp density, 3.0M $H_2SO_4$, $60^{\circ}C$ and 200 rpm with 30 ml $H_2O_2$ as a reducing agent were more than 97.9% and 93.9% and coprecipitation of Mn-Zn ferrite powder was performed according to various reaction conditions such as temperature, time and amount of $O_2$ gas injection using the leaching solution. As a result of coprecipitation, Mn-Zn ferrite could be synthesized directly at low temperature in the reaction condition pH 12, $80^{\circ}C$, $O_2$ 1.3 L/min. and 400 rpm. The synthesized Mn-Zn ferrite powder was spherical powder of $0.143{\mu}m$ particle size and had a saturation magnetization about 80 emu/g.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1123-1130
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• 1995

In the preparation of manganese zinc ferrite powders by alcoholic dehydration of citrate/formate solution. The effect of pH change on precipitation was investigated. The pH range for obtaining stable precipitates was studied. The glassy phase was obtained when the pH value of solution is higher than 5, and the formation mechanism of glassy phase was suggested. Below pH 5, the stable precipitates were formed, and the optimal pH was 2. Formation of glassy phase was accounted for the change of surface charge by pH change. The change of surface charge is caused by the interparticular agglomeration. The precipitate was redissolved into the water on the surface of precipitate itself and through the polymerization, it agglomerated. This mechanism is tought to be similar to that of viscous flow.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.114-114
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• 2017