• Journal of the Korean Chemical Society
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• v.39 no.8
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• pp.627-634
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• 1995

Layered double hydroxides ($Mg-Al-CO_3$ systems, LDH), which are hydrotalcite-like anionic clay minerals, having different $Mg^{2+}\;to\;Al^{3+}$ ratio were synthesized by coprecipitation method. The subsequent products were characterized by the following methods; elemental analysis, X-ray powder diffraction, thermal analysis (DSC and TGA), FT-IR and $^{27}$Al-MAS NMR. X-ray powder patterns showed that the products formed were layered structure materials. Two heat absorption peaks were observed around 20 ∼280$^{\circ}C$ (surface water and interlayer water) and 280∼500$^{\circ}C$ (water from lattice hydroxide and carbon dioxide from interlayer carbonate) in DSC diagrams, and they were quantitatively analyzed by TGA diagrams (in case LDH4 16.2% and 28.6% respectively). FT-IR spectra indicate that the interlayer carbonate ions occupied symmetrical sites between two adjacent layers in a parallel direction. $^{27}$Al-MAS NMR spectra show only single resonance (8.6 ppm) of the octahedrally coordinated aluminum similar magnesium. When LDH4 was calcined at 560$^{\circ}C$ for 3 hours in air, its layered structure was destroyed giving a mixed metal oxide. However it readily became rehydrated in aqueous chromate solution to its original structure.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.284-288
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• 2004

To improve mechanical properties of $Al_2$O$_3$/ZrO$_2$composites have been controlled dispersion of ultra low size ZrO$_2$ particles in $Al_2$O$_3$ ceramics by polymeric precursor method (Pechini process). In case of coprecipitation or mechanical mixing of ZrO$_2$ powders with $Al_2$O$_3$, homogeneous dispersion and controlling the ZrO$_2$ size were relatively difficult due to high sintering temperature. So the polyesterization process of Zr/Y(NO$_3$)$_3$-citric acid solution in ethylene glycol with the commercial sub-micron sized o(-alumina powder (Sumitomo AES-11(0.4 ${\mu}{\textrm}{m}$)) was adopted in order to obtain homogeneous dispersion of ZrO$_2$ in A1203. By this partial polyesterization process, the homogeneous dispersion of relatively low sized ZrO$_2$in $Al_2$O$_3$/ZrO$_2$composites was achieved at 1450∼1$600^{\circ}C$ of sintering temperature range and their mechanical properties were measured.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.53-63
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• 1992

M/BM -series catalysts, $MoO_3$ supported on ${\alpha}-Bi_2Mo_3O_{12}$ were also prepared by impregnation method. BM/M-series catalysts, ${\alpha}-Bi_2Mo_3O_{12}$ supported on $MoO_3$ were also prepared by coprecipitation. Structure and catalytic properties of the two phase catalysts were studied by means of using nitrogen adsorption, X-ray diffraction, and scanning electron microscopy. The reaction test for the selective oxidation of propylene to acrolein over Bi-molybdate catalysts was studied using a fixed-bed reactor system. In M/BM-series catalysts, $MoO_3$ was dispersed on ${\alpha}-Bi_2Mo_3O_{12}$, and the crystal structure of ${\alpha}-Bi_2Mo_3O_{12}$ remains unchanged by the presence of excess $MoO_3$. However the surface morphology and bulk structure of BM/M-series catalysts were altered probably because the precipitated $Bi(OH)_3$ reacted with $MoO_3$ during the calcination to form ${\alpha}-Bi_2Mo_3O_{12}$ phase. The results of propylene oxidation on both series catalysts showed that the reaction took place over the surface of ${\alpha}-Bi_2Mo_3O_{12}$ particle and the role of excess $MoO_3$ was to supply oxygen to ${\alpha}-Bi_2Mo_3O_{12}$. These increasing effects on activity were also observed in the mechanical mixtures of ${\alpha}-Bi_2Mo_3O_{12}$ and $MoO_3$.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.328-332
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• 2010

In this study, porous ZnO sphere and Cu-ZnO composite were synthesized by coprecipitation method in diethylene glycol solvent. The physicochemical properties of as-prepared composite materials were characterized by SEM, XRD, $N_2$-sorption and $H_2$-TPR. A series of porous Cu-ZnO with different Cu contents (0, 6.6, 21.3, 36.4, 54.6, 77.8 wt%) was investigated for CO oxidation activity in a fixed bed reactor system. With increasing Cu content in Cu-ZnO the surface area and micropore volume of Cu-ZnO are decreased and Cu (36.4 wt%)-ZnO shows higher activity for CO oxidation compared to the others.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.886-893
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• 2001

We synthesized $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ powders by coprecipitation, citration and solid-state reactions. The oxygen permeation membranes were fabricated by cold isostatic pressing of the synthesized powders, followed by sintering in air. All powders and membranes consist of perovskite phases. The coprecipitated powders showed the highest surface area ($7.5m^2/g$) but strontium deficiency was found during washing and filtering in the process. The membrane with lower relative density was fabricated by citration method. On the other hand, solid state reacted powders had high relative density (95%), and mechanical properties showed superior properties. Especially, the composition of the solid-state reacted powders was relatively well-controlled.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.667-675
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• 1994

The precipitate flotation using $La(OH)_3$ as a coprecipitant was studied for the simultaneous determination of trace three elements in a sea water. Several experimental conditions such as pH, coprecipitant and surfactant were investigated with an artificial sea water. To remove the influence of Cr(VI) the Cr(VI) was reduced to Cr(III) using $NaBH_4$ prior to the flotation. Trace amounts of Cu(II), Co(II) and total Cr in 1.0 l sea water was coprecipitated together with the precipitation of $La(OH)_3$ in the solution of pH 9.8 adjusted with 3.OM NaOH solution. The precipitate was floated by using a mixed surfactant (1 to 8 of each 0.5% ethanolic sodium oleate and sodium dodecylsulfate solution) by bubbling a nitrogen gas. The floats was separated and filtrated from the mother liquor by suction. The precipitate was dissolved in 7.0 M $HNO_3$ solution and then marked to 25.0 ml with a deionized water. These elements were determined by graphite fumace atomic absorption spectrophotometry. This method was applied to determine the elements in the sea water of the Eastern and Western coasts. And the recoveries were over 90.0% in the samples into which given amounts of the analyte elements were spiked.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.102-106
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• 2006

Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers. in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. We have synthesized magnetite $(Fe_3O_4)$ nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 2 to 8nm by controlling the sodium oleate concentration. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with sodium oleate and chitosan have been prepared. Nanoparticles, both oleate-coated and chitosan-coated, have been characterized by several techniques. Atomic farce microscope (AFM) was used to image the coated nanoparticles. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the magnetite nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles.

• Journal of the Korean Magnetics Society
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• v.16 no.4
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• pp.221-227
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• 2006

We have synthesized uniform nanometer sized magnetite particles using chemical coprecipitation technique through a sonochemical method with surfactant such as oleic acid. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetite nanoparticles is surface phase morphology and biopolymer-microspheres for Application Medical. Magnetite nanoparticles coated biopolymer. Atomic Force Microscope (AFM) was used to image the coated nanoparticles. Magnetic colloid suspensions containing particles with sodium oleate, chitosan and $\beta$-glucan have been prepared. The morphology of the magnetic biopolymer microsphere particles were characterized using optical microscope. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the biopolymer microspheres and magnetite coated biopolymer including magnetite nanoparticles. Magnetic Resonance (MR) imaging was used to investigate biopolymer coated nanoparticles and biopolymer microspheres.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.120-125
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• 2008

In this study, NiCoZn ferrites with the variation of sintering temperature and chemical composition were prepared by the coprecipitation. Microstructures Crystal structure of NiCoZn ferrites were analyzed by XRD and their electric magnetic characteristics were analyzed by LCR meter and their morphology observed by SEM. We identified that these powders have a typical NiCoZn spinel structure and nanoparticles average size of 40 nm. The impurity, the initial permeability and the Q factor value are the lowest of sintered NiCoZn ferrite at $1250^{\circ}C$. Also, we measured S-parameter for $(Ni_{0.4}Co_{0.1}Zn_{0.5})Fe_2O_4$ which showed a maximum reflection loss of -3.1 dB at 6 GHz for the 2 mm thick sample. From this result, we found that the NiCoZn ferrite can be used in ferrite microwave-absorbing application at a higher frequency region (> 6 GHz).

• Journal of Adhesion and Interface
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• v.19 no.3
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• pp.106-112
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• 2018

Recently, the hyperthermia treatment of malignant tissues has gained great attention as a biocompatible and benign method that facilitates successful cancer therapy compared to radiation and chemotherapy. In this study, superparamagnetic ($Fe_3O_4$) iron oxide nanoparticles (IONP) coated with biocompatible polymer (IONP@P(MPC/FOM)) for the purpose of hyperthermia treatment were prepared and related characterization were performed. IONPs with having 15 nm diameter were first prepared by coprecipitation and followed by surface modification with 4-cyanopentanoic acid dithiobenzoate (CTP) for reversible addition-fragmentation chain transfer (RAFT) copolymerization by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and fluorescein O-methacrylate (FOM) to form corona layer of P(MPC/FOM) on the surface of the IONP. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the morphology and hydrodynamic size of the IONP@P(MPC/FOM) and thermogravimetric analysis (TGA) confirmed the formation of P(MPC/FOM) corona layer, respectively. Exposing IONP dispersion to alternating magnetic field suggests that the IONP@P(MPC/FOM) aqueous dispersion with 0.2 wt.% can be used for hyperthermia treatment.