• E2M - 전기 전자와 첨단 소재
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• 제9권9호
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• pp.906-910
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• 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.

• 한국세라믹학회지
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• 제20권2호
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• pp.107-114
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• 1983

Formation of Strontium titanate from the products of coprecipitation takes place at 110$0^{\circ}C$ which is 200-30$0^{\circ}C$ lower than that from mechanical mixtures of $SrCO_3$ and $TiO_2$. This is apparently due to the nature of the compounds formed by the reaction of mixtures of aqueous solutions of $SrCl_2$ and $TiCl_4$ with an ammoniacal solution of ammoni-um carbonate and ammonium hydroxide. A procedure is described for preparing strontium titanyl oxalate tetrahydrate in the several mole ratio of $TiCl_4$ to $SrCl_2$. STrontium titanyl oxalates decompose to titanate at elevated temperature. The coprecipitates and the fired specimen were subjected to examined thermal and X-ray analyses and microstruc-ture by SEM.

• 한국세라믹학회지
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• 제26권3호
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• pp.395-401
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• 1989

The concentrations of Cu(II), Y(III) and Ba(II) ionic species in aqueous solution due to the formation of Cu2+-oxalate-complex have been theoretically calculated with respect to pH and their solubility diagrams could be obtained. It was verified from the calculation that the excess of Cu2+ and Ba2+ should be added in order to obtain oxalate coprecipitates with the molar ratio of Y : Ba : Cu=1 : 2 : 3. The exact amount of excess species has been calculated with respect to the initial concentrations of metal ions and pH.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1140-1142
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• 1993

It has been prepared by a coprecipitation method for Ferroxplana $Ni_2Y\;(Ba_2Ni_2Fe_{12}O_{22}$ magnetic particles, which is one of the Hexagonal ferrite. The coprecipitates were synthesized by adding aqueous solution of $BaCl_2{\cdot}2H_2O,\;NiCl_2{\cdot}6H_2O\;and\;FeCl_2{\cdot}4H_2O$ (of which the mole ratio is $Ba^{2+}:Ni^{2+}:Fe^{2+}$=1:1:6) to a mixture of NaOH and $Na_2CO_3$ solution. The shape of Ferroxplana $Ni_2Y$ magnetic particles obtained at the calcined temperature 1,100($^{\circ}C$) was hexagonal plate-like, average particle size was 2(${\mu}m$), and aspect ratio was more than 7.

• 한국세라믹학회지
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• 제40권6호
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• pp.577-582
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• 2003

공침전물을 원료로 사용한 수열합성법을 통해 저온에서 미립의 BaTiO$_3$ 분말을 합성하였다. 출발물질로는 BaCl$_2$와 TiCl$_4$ 의 수용액을 사용하였다 이들의 혼합용액을 제조한 다음 과산화물 형태의 침전을 얻기 위해 과산화수소수($H_2O$$_2$)를 첨가하였으며 이렇게 준비된 용액을 암모니아수에 적하하여 공침전물을 얻었다. 이 과산화공침전물을 수열합성의 원료로 사용하였으며 반응온도와 시간 및 pH를 달리하면서 합성하였다. pH 13 이상이 요구되어 강염기인 KOH나 NaOH를 사용하는 일반적인 수열합성법과 달리 암모나아수로도 얻을 수 있는 pH 12 이하에서 perovskite BaTiO$_3$가 합성되었으며, 11$0^{\circ}C$ 이상에서 균일하고 미세한 BaTiO$_3$ 분말을 합성할 수 있었다. 13$0^{\circ}C$ 이상에서 얻은 분말의 경우 합성시간과 관계없이 일정한 물성을 보여주었다. 이렇게 합성된 분말은 76 $m^2$/g의 높은 비표면적을 보였으며 20 nm 이하의 미세한 일차입자들이 약하게 결합된 응집체를 이루고 있었다. 수열합성분말을 이용하여 l150~120$0^{\circ}C$의 온도범위에서 소결한 시편의 소결특성 및 유전 물성을 평가하였다.

• Journal of Pharmaceutical Investigation
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• 제10권3호
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• pp.33-45
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• 1980

In order to increase the solubility of metoclopramide, various ratio coprecipitates with polyvinylpyrrolidone (M.W. 40,000) were prepared. The experiments of the solubility, physicochemical characteristics were quantitatively developed. The solubility increased as the ratio of rnetoclopramide to polyvinylpyrrolidone in metoclopramide-polyvinylpyrrolindone coprecipitate increased. In powder state, the dissolution rate of metoclopramide-polyvinylpyrrolidone coprecipitate was greater than that of metoclopramide and metoclopramide-polyvinylpyrrolidone physical mixture. Dissolution characteristics of non-disintegrating disk with constant surfacearea was in accord with Noyes-Nernst equation. The intrinsic dissolution rate, G, at $37^{\circ}C$ was $3.98{\times}10^{-7}M/cm^2{\cdot}min$ for metoclopramide, $2.26{\times}10^{-6}\;M/cm^2{\cdot}min$ for 1 : 5 metoclopramide-polyvinylpyrrolidone coprecipitate, respectively. Accordingly, activation energy of metoclopramide was 15,061cal/M, 9,178cal/M for 1 : 5 metoclopramide-polyvinylpyrrolidone coprecipitate and the activation energy decreased as the coprecipitate was formed. X-ray diffraction study revealed the fact that metoclopramide was crystalline, in contrast, there was no crystallinity evident in the 1 : 5 metoclopramide-polyvinylpyrrolidone coprecipitate. There was no difference between physical mixture and coprecipitate in TLC, UV and NMR studies. From the comparision between physical mixture and coprecipitate in IR spectrum, the interaction such as association between metoclopramide and polyvinylpyrrolidone was considered. But the association was easily dissociated in methanol solution.

• 한국재료학회지
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• 제4권5호
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• pp.541-549
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• 1994

공침법으로 제조된 비정질 $PbTiO_{3}$전구체의 결정화거동과 구조적 변화를 XRD, 라만스펙트럼, TEM, RDF등으로 조사하였다. 전구체는 이온안정제로 $H_2O_2$혹은 $NH_4NO_3$를 사용하여 제조된 질산납과 사염화티탄의 혼합수용액으로부터 $45^{\circ}C$, pH 9에서 제조되었다. 이온안정제로 $H_2O_2$를 사용한 경우보다 $NH_4NO_3$를 사용하여 제조된 공침물이 더 낮은 온도에서 결정화가 시작되며 결정화의 활성화에너지도 더 작은 값을 가진다. 비정질의 공침물은 transient phase를 거쳐 결정 $PbTiO_{3}$로 변태된다. 비정질 상태의 평균 원자거리는 열처리온도의 증가에 따라 감소한다.

• 한국자기학회지
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• 제16권3호
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• pp.163-167
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• 2006

초음파 조사 및 계면활성제 첨가에 따른 입자의 변화를 연구하기 위하여 침전법, 음향화학적 침전법 그리고 게면활성제를 첨가한 음향화학적 침전법으로 나노 입자를 합성하였고, X-선 회절실험을 통하여 마그네타이트가 합성된 것을 확인하였다. 침전법, 음향화학적 침전법으로 합성한 입자의 크기는 계면활성제를 첨가한 음향화학적 침전법으로 합성한 입자보다 크게 얻어졌고, 초음파 출력이 증가 할수록 크기는 증가하였다. 계면활성제로 올레인 산을 첨가한 음향화학적 기법에서는 게면활성제의 농도에 따라 입자 크기를 선택적으로 조절하여 합성할 수 있었고, 단순 침전법이나 음향화학적 기법에서 보다 생성되는 입자의 크기 분포가 좁게 나타났다. 마그네타이트 나노 입자들의 자기적 특성을 SQUID를 통하여 분석한 결과, 실온에서 모두 초상자성 거동을 보이는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제24권4호
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• pp.534-544
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• 2014

The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, $SO_4{^{2-}}$ in the inoculated red earth soil decreased acutely after incubation. The shift in the microbial community composite in the inoculated soil was analyzed through denaturing gradient gel electrophoresis. Results revealed the potential cooperative effect of microbial Fe(III) reduction and sulfate reduction on copper immobilization. After exposure to air for 144 h, more than 50% of the immobilized Cu was remobilized from the anaerobic matrices; aqueous sulfate increased significantly. Sequential extraction analysis demonstrated that the organic matter/sulfide-bound Cu increased by 52% after anaerobic incubation relative to the abiotic treatment but decreased by 32% after oxidation, indicating the generation and oxidation of Cu-sulfide coprecipitates in the inoculated red earth soil. These findings suggest that the immobilization of copper could be enhanced by mediating microbial Fe(III) reduction with sulfate reduction under anaerobic conditions. The findings have an important implication for bioremediation in Cu-contaminated and Fe-rich soils, especially in acid-mine-drainage-affected sites.

• 한국세라믹학회지
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• 제38권11호
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• pp.1023-1029
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• 2001

육방정 페라이트 $Co_2$Z(B $a_3$ $Co_2$F $e_{24}$ $O_{41}$ )를 여러 공침-산화 방법으로 제조하여 생성과정을 연구하였으며, 적절한 제조 방법을 결정하였다. 산화 및 공침 순서를 다르게 하여 $Ba^{2+}$, $Co^{2+}$, F $e^{2+}$ 등의 염화물 혼합 수용액으로부터 $Co_2$Z 조성의 수산화물을 제조하였다. 그리고 열처리 온도에 따른 생성상의 변화를 열분석(DTA/TGA), 분말 X-선 회절분석, 주사전자현미경 등을 이용하여 관찰하였다. $Co_2$Z 상은 출발물질이 비정질에 가까운 산수산화철($\delta$-FeOOH)일 경우에만 관찰되었으며, $Ba_3$F $e_{32}$ $O_{51}$ , BaF $e_{12}$ $O_{19}$ (M형), $Ba_2$ $Co_2$F $e_{12}$ $O_{22}$ (Y형)로부터 생성되었다. 염화물 혼합 수용액을 산화시킨 다음 침전하여 합성한 공침물은 110$0^{\circ}C$부터 $Co_2$Z가 생성되었다.