• Journal of information and communication convergence engineering
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• v.7 no.1
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• pp.72-77
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• 2009

Three different procedures for adding Pd compounds to $SnO_2$ particles have been investigated. These processes are: (1) coprecipitation; (2) dried powder impregnation; and (3) calcined powder impregnation. The microstructures of $SnO_2$ particles have been analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). In the coprecipitaion method, the process does not restrain the growth of $SnO_2$ particles and it forms huge agglomerates. In the dried powder impregnation method, the process restrains the growth of $SnO_2$ particles and the surfaces of the agglomerates have many minute pores. In the calcined powder impregnation method, the process restrains the growth of $SnO_2$ particles further and the agglomerates have a lot more minute pores. The sensitivity ($S=R_{air}/R_{gas}$) of the $SnO_2$ gas sensor made by the calcined powder impregnation process shows the highest value (S = 21.5 at 5350 ppm of $C_3H_8$) and the sensor also indicates the lowest operating temperature of around $410^{\circ}C$. It is believed that the best result is caused by the plenty of minute pores at the surface of the microstructure and by the catalyst Pd that is dispersed at the surface rather than the inside of the agglomerate. Schematic models of Pd distribution in and on the three different $SnO_2$ particles are presented.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.257-257
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.346-346
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.258-258
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.95.2-95
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• 2000

• Analytical Science and Technology
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• v.5 no.4
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• pp.425-431
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• 1992

The concentration and determination of trace phosphate ion was studied by $La(OH)_3$ coprecipitaiton. Phosphate ions in 1.0L samples were coprecipitated with lanthanium hydroxide at pH 9.5 adjusted with ammonia solution. The precipitates were floated with the aid of mixed surfactant(1:8 sodium oleate/sodium dodecyl sulfate) and nitrogen gas bubbles. The floated precipitate was collected in suction flask from the solution. The precipitate were washed with dil. ammonia solution and dissolved in sulfuric acid. The phosphate ion in the concentrated solution was finally determinated by UV/VIS spectrophotometry using the molybdenium blue method. The proposed method could be applied to the determination of phosphate ion in tap water and river water.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.31-36
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• 2003

In this study, nano-sized NiCuZn-ferrites for the multi-layered chip inductor application were prepared by a coprecipitation method and its electromagnetic properties were analyzed. Also, the property of low temperature sintering were studied with the initial heat treatment of powder.$(Ni_{0.4-x}Cu_xZn_{0.60})_{1+w}(Fe_2O_4)_{1-w}$ (x=0.2, w=0.03) were calcined at $300^{circ}C~750^{circ}C.$ The sintered NiCuZn-ferrites at $900^{\circ}C$ showed good apparent density $4.90g/cm^3,$ and magnetic properties of initial permeability 164 and quality factor 72. As the calcination temperature increase, the grain size of NiCuZn-ferrite increased with irregular grain distribution and its magnetic properties were deteriorated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.247-250
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• 1999

In this study, three kinds of Mn-Zn ferrite/Ni-Zn ferrite/$Ni_2Y$ ferroxplana prepared by the coprecipitation method was compounded with silicon rubber, and thereafter made ring-type specimens with various compositional ratio. The material constant of ferrite/rubber composite absorbers was obtaibed by the 2-port method. The material constants of the ferrite/rubber composite absorber with various compositional ratio of three kinds of ferrite were used to design the matching frequency and thickness with the impedance matching map. We were able to predict the matching condition from the design method.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1381-1389
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• 2007

Wastewater discharged by industrial activities of metal finishing and electroplating units is often contaminated by a variety of toxic or otherwise harmful substances which have a negative effects on the water environment. The treatment method of heavy metal-cyanide complexes wastewater by alkaline chlorination have already well-known($1^{st}$ Oxidation: pH 10, reaction time 30 min, ORP 350 mV, $2^{nd}$ Oxidation: ORP 650 mV). In this case, the efficiency for the removal of ferro/ferri cyanide by this general alkaline chlorination is very high as 99%. But the permissible limit of Korean waste-water discharge couldn't be satisfied. The initial concentration of cyanide was 374 mg/L(the Korean permissible limit of cyanide is 1.0 mg/L max.). So a particular focus was given to the treatment of heavy metal-cyanide complexes wastewater by $Zn^{+2}/Fe^{+2}$ ion and coprecipitation after alkaline chlorination. And we could meet the Korean permissible limit of cyanide(the final concentration of cyanide: 0.30 mg/L) by $Zn^{+2}/Fe^{+2}$ ion and coprecipitation(reaction time: 30 min, pH: 8.0, rpm: 240). The removal of Chromium ion by reduction(pH: 2.0 max, ORP: 250 mV) and the precipitation of metal hydroxide(pH: 9.5) is treated as 99% of removal efficiency. The removal of Copper and Nickel ion has been treated by $Na_2S$ coagulation-flocculation as 99% min of the efficiency(pH: $9.09\sim10.0$, dosage of $Na_2S:0.5\sim3.0$ mol). It is important to note that the removal of ferro/ferri cyanide of heavy metal-cyanide complexes wastewater should be employed by $Zn^{+2}/Fe^{+2}$ ion and coprecipitation as well as the alkaline chlorination for the Korean permissible limit of waste-water discharge.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1406-1408
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• 1994

In recently, there is growing demand for microwave absorbing matrial, and for the design method of microwave absorber. We developed a new method to design the matching frequency and matrial thick for ferrite/rubber composite absorber. Ni-Zn ferrite prepared with coprecipitation was compounded with silicon rubber, and, subsequently, pressed to ring specimen. The matrial constant of the ferrite/rubber composite absorber was used to design the matching frequency and matrial thick with matching map. In this study, we could predict matching condition from the design method. Foremore, using matching boundary map, we could also predict the condition of over 20[dB] attenuation.