• Journal of the Korean Chemical Society
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• v.49 no.1
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• pp.47-55
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• 2005

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1701-1704
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• 2006

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4197-4200
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• 2012

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.231-237
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• 2013

Thermodynamic modeling of the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ complex ferrite system has been adopted as a rational approach to establish routes to better synthesis conditions for pure phase $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ complex ferrite. Quantitative analysis of the different reaction equilibria involved in the precipitation of $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ from aqueous solutions has been used to determine the optimum synthesis conditions. The spinel ferrites, such as magnetite and substitutes for magnetite, with the general formula $MFe_2O_4$, where M= $Fe^{2+}$, $Co^{2+}$, and $Ni^{2+}$ are prepared by coprecipitation of $Fe^{3+}$ and $M^{2+}$ ions with a stoichiometry of $M^{2+}/Fe^{3+}$= 0.5. The average particle size of the as synthesized $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$, measured by transmission electron microscopy (TEM), is 14.2 nm, with a standard deviation of 3.5 nm the size when calculated using X-ray diffraction (XRD) is 16 nm. When $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ ferrite is annealed at elevated temperature, larger grains are formed by the necking and mass transport between the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ ferrite nanoparticles. Thus, the grain sizes of the $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ gradually increase as heat treatment temperature increases. Based on the results of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimeter (DSC) analysis, it is found that the hydroxyl groups on the surface of the as synthesized ferrite nanoparticles finally decompose to $Ni_{0.5}Zn_{0.4}Cu_{0.1}Fe_2O_4$ crystal with heat treatment. The results of XRD and TEM confirmed the nanoscale dimensions and spinel structure of the samples.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.2
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• pp.164-171
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• 2007

This experiment was conducted to investigate heavy metal speciation and bioavailability from soil to the edible parts of water dropwort near industrial complex. The soils and water dropwort were collected from the paddies cultivating water dropwort(10 sites), stream sediments(5 sites), and background soils(3 sites) near industrial complex. The total concentrations of Cd Cu, and Ni were higher than those of permissible level for soil contamination(Cd 3, Cu 100, Ni $50mg\;kg^{-1}$ in soil) suggested by Kloke(1979). Dominant chemical forms of Cd in paddies cultivating water dropwort and stream sediments were exchangeable form(49.1-56.3%), and those of Cu, Zn, and Ni were Fe and Mn oxide bound and residual forms. The mobility factor of heavy metals in paddies cultivating water dropwort and stream sediments was in the order Cd>Zn>Ni>Cu>Pb, specially, the mobility factor of Cd (62-72%) were relatively higher than that of other metals in soils. The total concentrations of Cd in soils showed significant positive correlation with the ratios of exchangeable and Fe and Mn oxide bound forms, while correlated negatively with residual form. Heavy metal contents in root parts were higher than those in top parts of water dropwort. The bioavailability of water dropwort varied considerably between the different parts and heavy metals. Cd, Cu and Ni contents in water dropwort were correlated with each fractions in soils. Specially, the exchangeable form of Cd and Ni in soils showed significant positive correlation with the those contents of water dropwort.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.28-231
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• 1999

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3765-3770
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• 2010

Selective oxidation of olefins has been carried out in water medium with tert-butylhydroperoxide (TBHP, 70% aqueous) as an oxidant using polymer-anchored Ni(II) complex as a catalyst. Several parameters were varied to optimize the reaction conditions. Under the optimized reaction conditions olefins gave selectively allylic oxidation products. The present polymer anchored Ni(II) complex can be recycled five times without any appreciable loss in catalytic activity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.462-467
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• 2014

In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about $1{\mu}m$ and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6~4 while those values at above 500 MHz were decreased 0.4~2.5 according to the change of contents of FeSiCr and Fe50Ni powders. As a result, the reflection loss can be moved to the lower frequency from 2~3 GHz to 1~1.5 GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.632-638
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• 2014

We investigated the effects of DMAB (Borane dimethylamine complex, C2H10BN) in electroless Ni-B film with addition of DMAB as reducing agent for electroless Ni plating. The electroless Ni-B films were formed by electroless plating of near neutral pH (pH 6.5 and pH 7) at $50^{\circ}C$. The electroless plated Ni-B films were coated on screen printed Ag pattern/PET (polyethylene terephthalate). According to the increase of DMAB (from 0 to 1 mole), the deposition rate and the grain size of electroless Ni-B film increased and the boron (B) content also increased. In crystallinity of electroless Ni-B films, an amorphization reaction was enhanced in the formation of Ni-B film with an increasing content of DMAB; the Ni-B film with < 1 B at.% had a weak fcc structure with a nano crystalline size, and the Ni-B films with > 5 B at.% had an amorphous structure. In addition, the Ni-B film was selectively grown on the printed Ag paste layer without damage to the PET surface. From this result, we concluded that formation of electroless Ni-B film is possible by a neutral process (~green process) at a low temperature of $50^{\circ}C$.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.87-91
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• 2003

This study was carried out to investigate the heavy metal distributions of soils in the vicinity of Shi-Hwa industrial complex region, where the air pollutants from industrial area could affect the soil environment of near residential and green areas. The ranges of contents of As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn in soils were 0.58~3.81, ND~0.91, 0.15~6.33, ND~l.86, 0.14~110.27, ND~l.17, 0.04~10.59, 1.16~86.48 and 1.83~212.65 mg/kg, respectively. For all industrial, residential and green areas, the heavy metal contents were much lower than the standard of Korean Soil Environmental Preservation Act or the critical concentration which phytotoxicity is considered to be possible. Mean values of contents of As were similar in industrial, residential and green areas. However, the mean values of contents of Cd and Cr in industrial area were higher 10 and 5 times than those in residential and green area, respectively. And also the mean values of contents of Co, Cu, Hg, Ni, Pb and Zn in industrial area were higher 2~3 times than those in residential and green area.