• Journal of Magnetics
• /
• v.14 no.4
• /
• pp.165-167
• /
• 2009

Nano-sized Yttrium iron garnet (YIG;$Y_3Fe_5O_{12}$) particles have been synthesized by using coprecipitation and a heat treatment process. The YIG particles were made using a nitrate or a chloride salt solution. The pH concentration of the solution was fixed at 12. Spherical shaped YIG particles were made with a size of about 20 nm. The magnetization value of the particles was smaller than the bulk value but their coercive field showed a high value.

• 한국해양학회지
• /
• v.15 no.1
• /
• pp.66-70
• /
• 1980

A method for the determination of dissolved species of Cd, Co, Cu, Ni, Pb and Zn in sea water by flame atomic absorption spectrophotometry (AAS) is described. Prior to analysis by AAS, these elements are concentrated by coprecipitation with iron pyrrolidinedithiocarbamate at pH 3 because of matrix effects and their low concentration levels in sea water. The detection limits are 0.01, 0.04, 0.02, 0.05, 0.08, and 0.03$\mu\textrm{g}$/l, and the relative standard deviations are 1.0, 2.4, 1.3, 2.9, 2.0 and 2.9% for Cd, Co, Cu, Ni, Pb and Zn, respectively. The method is shown to be satisfactory in terms of recovery and precision for the determination of these metals in sea water.

• Journal of the Korean Ceramic Society
• /
• v.27 no.2
• /
• pp.244-248
• /
• 1990

The effect of Nd3+ on the electrical and optical properties in PZT ceramics were investigated. The powders were prepared by the coprecipitation method using the salt solutions and Nd3+ was partially substituted for Pb2+ of Pb(Zr0.54 Ti0.46)O3. The coprecipitate were obtained under pH 11.8-12 and the single phase of PLZT powders were synthesized at about 500$^{\circ}C$. In the case of specimens with 4at.% of Nd which were sintered at 1250$^{\circ}C$ for 55 hours under 1atm, showed 50% of transmittance for 600nm(wave length).

• Journal of the Korean Ceramic Society
• /
• v.26 no.4
• /
• pp.532-538
• /
• 1989

The properties and sinterabilities of the ZrO2-3m/oY2O3 powders prepared by coprecipitation were investigated. The specific surface area and the total proe volume were decreased with the increasing pH of the sediments. The partially stabilized zirconia powders were fine powders with high specific surface area. The powders prepared by freeze drying method showed low tendency for agglomeration, and the powders obtained from spray drying method showed fine powders and narrow pore size distribution. At 140$0^{\circ}C$, their relative densities were up to 96%.

• Electrical & Electronic Materials
• /
• v.9 no.9
• /
• pp.906-910
• /
• 1996

Ferroxplana N $i_{2}$Y(B $a_{2}$N $i_{2}$F $e_{12}$ $O_{22}$ ) magnetic particles, which is one of the hexagonal ferrite were synthesized by a coprecipitation method. The coprecipitates were prepared by adding aqueous solution of BaC $I_{2}$ - 2 $H_{2}$O, NiC $I_{2}$ - 6 $H_{2}$O and FeC $I_{3}$ - 6 $H_{2}$O(of which the mole ratio is $Ba^{+2}$ : N $i^{+2}$ : F $e^{3+}$= 1 : 1 : 6) to a mixture of NaOH and N $a_{2}$C $O_{3}$. The shape of Ferroxplana N $i_{2}$Y magnetic particles obtained at 1, 100(.deg. C) was hexagonal plate-like, average particle size and aspect ratio were 2(.mu.m) and 7, respectively.y.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1342-1344
• /
• 1994

Silver-Nickel alloy has been used as a electrical contact material for low voltage, low current. Since the solubility between Ag and Ni is very low, it is difficult to produce Ag-Ni alloy by using conventional melting method and disperse Ni powder homogeneously in Ag matrix. In this study we have been produced fine Ag-Ni alloy powder by using coprecipitation method. Firstly, we have produced silver-nickel nitrate solution by dissolving the Ag and Ni ingot in nitric acid solution and then, coprecipitate (Ag, Ni)carbonate dropping Ag-Ni nitrate solution to sodium carbonate solution. (Ag, Ni) carbonate is heat-treated in $H_2$ atmosphere, $400^{\circ}C$ and it has been analysed by TGA, SEM, XRD, ICP. It is represented Silver-Nickel alloy powder in the particle range of $0.1{\sim}0.5{\mu}m$.

• Journal of the Korean Ceramic Society
• /
• v.30 no.12
• /
• pp.1023-1028
• /
• 1993

To obtain a single phase of Ba2Ti9O20 at lower temperature than previious other researches. We investigated the effect of Zr substitution for predetermined portions of Ti in Ba2Ti9O20. In this study, the four compounds(x=0, 0.028, 0.048, 0.068) of Ba2(Ti1-xZrx)9O20 were prepared by coprecipitation reaction of BaCl2, TiCl4 and ZrOCl2 with (NH4)2CO3 and NH4OH as the coprecipitating agents and pH regulators, in queous solution. Owing to 4.8 mol% addition, the single phase of Ba2Ti9O20 showing high Q was obtained at 115$0^{\circ}C$ which is lower by 25$0^{\circ}C$ than the temperature in case of mechanical mixtures of BaCO3 and TiO2.

• Journal of the Korean Ceramic Society
• /
• v.23 no.4
• /
• pp.11-16
• /
• 1986

$BaTiO_3$ ceramics powder was prepared by coprecipitation method either in oxalic acid solution or in potassium hydroxide solution. Thermal decomposition of coprecipitated $BaTiO(C_2O_4)_2$.$4H_2O$ powder in oxalic acid solution was investigated by means of Themogravimetry Differential Thermal Analysis and X-ray Diffraction Analysis. Low temperature decomposition of coprecipitated $BaTiO(C_2O_4)_2$.$4H_2O$ caused narrow particle size distribution whereas high temperature decomposition caused fairly wide particle size distribution by partial sintering. As the reaction time increased the average particle size of coprecipitated $BaTiO_3$ powder in KOH solution was increased. The most narrow paticle size distribution was obtained when the coprecipi-tates were ripened for 4hrs.

• Journal of the Korean Ceramic Society
• /
• v.26 no.2
• /
• pp.242-248
• /
• 1989

The powder properties and sinterability of ZrO2-8m/o Y2O3 prepared by coprecipitation were investigated. The specific surface area and the total pore volume were increased with increasing pH of sediment and using of ethyl alcohol for washing. The powders of prepared by freeze drying method were showed the smallest particle size and lowest agglomerate rate, and the powders obtained from spray drying method were showed porous structure. At 130$0^{\circ}C$, their relative density were 94-96%, so these sintered bodies have revealed high sinterability in spite of low sintering temperature.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.10
• /
• pp.1512-1514
• /
• 2005

Catalytic properties of Ni-Zr$O_2$ catalysts prepared by coprecipitation have been studied for the gas-phase hydrogenation of 1,3-butadiene to butenes. The coprecipitation method led to the solid solution of Ni-Zr$O_2$, which contains highly resistant Ni species to thermal reduction with H2. Nickel species of the solid solution were highly dispersed in the ZrO2 lattice, so that the reduced catalysts were selective for hydrogenation of 1,3-butadiene to butenes (99.9%) even in the presence of 1-butene.