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황산제1철(FeSO₄7H₂O)과 수산화나트륨(NaOH) 용액에 혼합 당량비(R=2NaOH/FeSO₄)에 따라 혼합한 후 air bubbling을 통해 마그네타이트(Magnetite, Fe₃O₄)의 합성 최적조건을 조사하였다. 생성된 물질을 XRD분석, SEM관찰에 의해 검토하였고, BET surface area 측정을 하였다. 당량비가 1이하일 때는(R<1) 지오타이트(goethite, α-FeOOH)가 합성되었고 당량비가 1이상일 때는(R<1) 마그네타이트(Fe₃O₄)가 직접 합성되었다. 합성한 마그네타이트(Fe₃O₄)와 이 Fe₃O₄ 합성시에 NiCl₂를 0.01vol(%) 첨가한 시료를 수소가스로 350℃에서 4시간 동안 100ml/min 로흘려 환원시켜 산소결함마그네타이트(Fe₃O?)를 만들었다. 이것을 이용하여 이산화탄소(CO₂)의 분해반응을 조사하였다. 이산화탄소는 산소결함마그네타이트(Fe₃O?)에 의해 45분내에 거의 100% 분해되었다. 반응후 산소결함마그네타이트(Fe3O?) 표면에 탄소가 석출되어 있었으며, 이것을 650℃에서 수소가스와 반응 시켜 메탄(CH₄)으로 되었음을 확인 하였다. The optimum conditions were studied for the formation of Magnetite (Fe₃O₄) by air bubbling. The suspensions obtained by mixing Ferrous sulfate (FeSO₄ · 7H₂O) and S-odium Hydroxide (NaOH) solution in various values equivalent ratio(R=2NaOH/FeSO₄). The oxidation product were then examined X-ray diffraction. SEM, BET surface area determination. Equivalent ratio less 1 (R<1) formed Goethite (α-FeOOH) and equivalent ratio excess 1 (R<1) magnetite (Fe₃O₄) is formed directly. The oxygen-deficit magnetite (Fe₃O?), which is obtained by flowing H₂ gas (100ml/min) through the synthesis magnetite added NiCl₂ 0.01 vol(5) at 350℃ for 4hr. CO₂ decomposition for the oxygen-deficient magnetite nearly 100% (in 45min of the reaction time) at 350℃. These elemental carbon on the surface of the oxygen-deficient magnetite were found to be readily into CH₄ by the reaction with H₂gas at 650℃.
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Zn_χFe_(3-χ)O_4(0.003<X<0.08) was synthesized by air oxidation method for the decomposition of carbon dioxide. We investigated the characteristics of catalyst, the form of methane by gas chromatograph after decomposition of carbon dioxide and kinetic parameter. Zn_χFe_(3-χ)O_4(0.003<X<0.08) was spinel type structure. The surface areas of catalysts(Zn_χFe_(3-χ)O_4(0.003<X<0.08)) were 15~27 ㎡/g. The shape of Zn_0.003Fe_2.997O_4 was sphere. The optimum temperature for the decomposition of carbon dioxide into carbon was 350℃. Zn_0.003Fe_2.997O_4 showed the 85% decomposition rate of carbon dioxide and the degree of reduction by hydrogen(δ) of Zn_0.003Fe_2.997O_4 was 0.32. At 350℃, the reaction rate constant and activation energy of Zn_0.003Fe_2.997O_3.68 for the decomposition of carbon dioxide into carbon were 3.10 psi^(1-α)/min and 0.98 kcal/mole respectively. After the carbon dioxide was decomposed, the carbon which was absorbed on the catalyst surface was reacted with hydrogen and it became methane.
In the batch system, the mathematical modelling was done on the CO₂ decomposition reaction using the LiMn₂O₄ catalyst of 100-120 mesh. The porosity of catalysts and the amount of adsorption were observed by the mathematical analysis. The chemical reaction was mainly reacted at the surface reaction of catalysts more than pore of catalysts. The variety of concentration and real values in the catalysts were predicted and amount of adsorption was calculated. By the mathematical analysis, the adsorption of surface was superior to that of inner face of pore. In case of the identical weight of catalysts, the rate of CO₂ decomposition was increasing by increasing CO₂ concentrations.
Zn_χFe_(3-χ)O_4(0.003<X<0.08) was synthesized by air oxidation method for the decomposition of carbon dioxide. We investigated the characteristics of catalyst, the form of methane by gas chromatograph after decomposition of carbon dioxide and kinetic parameter. Zn_χFe_(3-χ)O_4(0.003<X<0.08) was spinel type structure. The surface areas of catalysts(Zn_χFe_(3-χ)O_4(0.003<X<0.08)) were 15~27 m^2/g. The shape of Zn_0.003Fe_2.997O_4 was sphere. The optimum temperature for the decomposition of carbon dioxide into carbon was 350℃. Zn_0.003Fe_2.997O_4 showed the 85% decomposition rate of carbon dioxide and the degree of reduction by hydrogen(δ) of Zn_0.003Fe_2.997O_4 was 0.32. At 350℃, the reaction rate constant and activation energy of Zn_0.003Fe_2.997O_3.68 for the decomposition of carbon dioxide into carbon were 3.10 psi^(??-??)/min and 0.98 kcal/mole respectively. After the carbon dioxide was decomposed, the carbon which was absorbed on the catalyst surface was reacted with hydrogen and it became methane.
The oxides in perovskite type, LaMO₃ (M=Ni, Cr, Fe, Co), compared with gas sensors which have been used, were synthesised and then examined sensor response comparatively in order to make a thick film gas sensor having a good gas selectivity, durability and simple manufacturing. The oxides in perovskite type, LaFe_(1-x)O₃(x=0.2, 0,4, 0.6, 0.8), which a part of Fe was replaced with Co, were examined with regard to their electric resistance with variable temperature and sensor response for carbon monoxide gas.
Correlation of catalytic activity for the oxidation of CO and sensor response to CO was investigated. The perovskite-type oxides prepared by partial substitution of LaFeO₃with other 3d transition metal M to give LaFe₁_хMхO₃. The catalytic activity of LaFe₁_хCOхO₃(x=0 to 0.2) increase in X, but the highest sensor response was achieved at x=0.1. It was found that the sensor response increased in proportion to the catalytic activity, provided that the apparent activation energy for electrical conduction was unaffected by the substitution.
황산제1철(FeSO₄ㆍ 7H₂O)과 수산화나트륨(NaOH) 수용액의 당량비를 1.00으로 혼합한 후 여기에 NiO수용액을 0.03, 0.05, 3.00mole%로 첨가하여 NiO-magnetite를 합성하다. 합성물질의 구조를 X-ray diffraction(XRD), SEM관찰에 의해 검토하였고 BET법을 이용한 Surface area를 관찰하였다. 각각의 mole%로 합성한 NiO-magnetite를 300℃, 350℃, 400℃, 450℃에서 수소(H₂)가스를 100ml/min 속도로 4시간 동안 공급하면서 환원시켜 산소결함 NiO-magmetite(NiO-Fe₃O₄-δ)를 제조하였다. 이 산소결함 NiO-magnetite를 이용하여 각각의 온도에서 이산탄소(CO₂)의 분해반응을 조사하였다. 이산화탄소는 10분내에 90%이상 분해되었다. 산소결함 NiO-magnetite의 표면에 탄소가 석출되었으며 이 탄소가 650℃에서 수소(H₂)가스와 반응하여 메탄(CH₄)으로 되었음을 확인하였다. 또한 NiO-magnetite를 이용한 이산화탄소 분해반의 반응차수와 각각의 온도에서 분해반응에 대한 반응속도상수를 구하였고 NiO-magnetite를 이용한 이산화탄소의 분해반응의 활성화에너지를 구했다. 본 실험에서 반응차수(n)는 0.9차이며 반응속도상수와 아레니우스법칙을 이용해 얻은 활성화는 51 ∼73kJ/mol임을 알았다. The solution of FeSO₄ㆍ 7H₂O and NaOH solution were prepared at the equivalent ratios 1.00. 0.03, 0.05, 0.30, 3.00mole% of NiO solution was added to the mixture. NiO-magnetite was synthesized by Air-bubbling. The character of the material synthesized thereby X-ray diffraction, SEM, TG-DTA. The surface area was measured by the BET method. The NiO-magnetite was supplied with hydrogen gas for 4 hours to be reduced to oxygen-deficit NiO-magnetite. By using the oxygen-deficit NiO-magnetite, the decomposition of CO₂ was observed 300℃, 350℃, 400℃, 450℃. More than 90% of CO₂ was decomposed in 10 minutes. Elementary carbone depoosited on the surface of NiO-magnetite. Then these carbones reacted with hydrogen gas to became methane at 650℃. The reaction order was found by using intergrated concentration changes with time. The activation energy for the decomposition of CO₂ was found by employing the Arrhenius law. Consequently, the reaction order turned out to be 0.9 and the activation energy was 51 to 73kJ/mol.
The industrial synthesis of BaTiO₃, used widely in ferroelectric materials, has generally been manufactured by solid state reactions between TiO₂and BaCO₃. But it is very difficult to get an uniformity of component. Another difficulty is that this process needs very high temperature. In this synthesis BaTiO(C₂O₄)₂·4H₂O has been synthesized with BaCl₂, TiCl₄, and H₂C₂O₄through an aqueous synthesis and BaTiO₃, having the structure of perovskitetype, has been prepared by the calcining to 900℃. I have experimented with several conditions of synthesis so that the mole ratio of BaO to TiO₂in the component of BaTiO₃is one to one. While BaTiO₃ is synthesized, the solution of TiCl₄and BaCl₂is maintained in an ice bath to prevent the hydrolysis of TiCl₄·H₂C₂O₄added to the mixed solution. BaCl₂is added to 1% more than the theoretical quantity and H₂C₂O₄is added in excess of 10%. The properties of temp-dielectric constants have been studied in order to evaluate the dielectric properties of samples. The result is that the dielectric constant, at ordinary temperature, increases slowly from 1450, very quickly from around 120℃, and when curie-point is 125℃, the dielectric constant is 8100. Therefore BaTiO₃, by aqueous synthesis, can be used as the dielectric because the components are homogeneous. Ⅰ. 緖 論 Ⅱ. 實驗方法 1. 試 藥 2. 試料의 合成 3. 測 定 1) 化學分析 2) X-線 回折分析 3) 密度測定 4) 誘電率 測定 Ⅲ. 結果 및 考察 1. 試料의 合成과 確認 2. 最適 ????燒溫度 3. 溫度-誘電率 特性 Ⅳ. 結 論
The sample used in the extraction of titanium dioxide was ilmenite. This ilmenite was mined from So-Yeonpeong-Do. The ilmenite was mixed with potassium tetraborate which was used as a solvent, and heated to a high temperature for the fused reaction. It was cooled down to room temperature. Then, potassium borates were extracted from this product by boiling water, and KFe???? Ti₃O?? by hot 0.5M-H₂SO₄. Through this reaction Ti??⁴ was extracted and TiO₂ was produced from the remaining raffinate. The reaction temperature and time were changed to find the optimum point. It was observed that the optimum time and temperature for the formation and the reaction were 45 minutes and 1050℃ respectively. Also unreacted potassium borates which were extracted by water and solidified after evaporation can be used as a solvent again. The recovery factor of the rutile was 78.2%.
Several condition for the spectrophotometric determination of gallium and indium with 4-(2-Pyridylazo)-resorcinol [PAR] have been studied. The color solution of gallium-PAR, indium-PAR shows a maximum absorption at 504nm, 510nm, and follow Beer's law over a range of a to 15㎍/25ml, 2 to 30㎍/25ml of gallium and indium The molar extinction coeffecient at 504nm, 510nm are estimated to be 102,000, 86, 400. The absorbancy of the solution is kept constant for 20hrs and is not affected by temperature between 13~35℃. Since iron(Ⅲ), cobalt, copper, bismuth, zinc. cadmium, aluminium interfere more or less, the seperation of gallium and indium from some of the above ions by means of ether extraction has been studied. the constitution of the complex examined by continuous variation method is that the molar ratio of gallium:PAR, indium-PAR are 1:2.