CBN(cubic boron nitride) 粉末 表面과Al₂O₃基板의 機能性 鍍金 特性에 關한 硏究

김동규 忠南大學校 2004 국내박사

CBN(Cubic Boron Nitride)은 입방정질화붕소의 약칭으로, 다이아몬드 합성 조건과 유사한 초고압고온 기술에 의해 제조되고, 다이아몬드에 다음가는 강도를 가지므로 연삭휠로서 널리 이용된다. 즉, 다이아몬드로는 곤란한 강의 연삭에 그 장점을 발휘한다. 강의 연삭에 일반적으로 이용되고 산화알루미늄 또는 탄화규소를 연삭재료로 하는 연삭 휠과 비교하여 CBN 연삭 휠은 수백 배 때로는 천 배를 넘는 연삭비를 가진다. 여기서, 연삭비는 연삭휠의 수명을 측정하는 지수로, 피삭제(연삭소재) 제거량 체적/연삭휠 소모체적의 비이다. 제거량이란 피연삭물에서 절삭되어 제거되는 양으로 가공량을 의미한다. 그러나, CBN 연삭휠은 가격이나 단위 소모체적에 있어서, 보통 연삭휠의 수 배 이상이기 때문에 CBN 연삭휠의 연삭비가 높아도 연삭 소모비는 상기의 보통 연삭휠에 비해 반드시 유리하지는 않다. 그러나, 연삭휠 소모비는 약간 높아도 작업능률이 좋으므로 종합하여 연삭 가공비는 보통 연삭휠 보다 우수하여 CBN 연삭휠이 이용되는 경우가 많다. 이러한 장점을 만족시키기 위해 CBN 연삭휠 제조시 CBN을 연삭휠에 고르게 도포하게 된다. 그러나 도포된 CBN 입자들이 기계가공시 손실될 수 있으므로 고가의 연삭휠 수명이 단축되는 경우가 있을 수 있다. 따라서 근래에 선진국을 중심으로 CBN 입자상에 무전해 도금법에 의한 불규칙한 모양의 금속코팅에 의하여 내구성을 향상시킨 제품에 대한 수요가 증가되고 있는 추세이다. 국내의 경우 표면처리 기초기술의 부족으로 인해 접근이 매우 까다롭기 때문에 원하는 형상제어를 위한 국내 표면처리 수준은 매우 낮은 상태이다. 일부 제조사를 중심으로 지금까지 무전해도금에 사용되는 도금용액을 전량 수입하여 사용하고 있으나 원가상승 및 도금기술에 대한 원천기술의 미흡으로 인하여 많은 어려움들이 발견되고 있다. 이러한 점으로 미루어 볼 때, 석출형상 제어가 가능한 CBN 분말상 무전해 니켈 도금기술개발은 약품개발에 의한 생산성의 원가절감 효과뿐 만 아니라 공구의 수명을 증가시킬 것이고, 보다 높은 기계가공속도에 의해 생산성이 향상된 다이아몬드 CBN공구를 생산할 수 있을 것이다. 이것은 다이아몬드 절삭 날과 날 모양의 최적화에 의해 아주 낮은 힘을 가하더라도 우수한 절삭성을 가질 수 있으며 절삭 시 Diamond 및 CBN의 손실을 최소화함으로서 절삭 날의 표면에 생기기 쉬운 흠집 모양의 깨짐 현상도 최소화 할 수 있다. 게다가 공구의 내구성이 월등히 향상되어서 많은 부품을 가공하여도 공구의 마모로 인한 제품의 치수변화가 거의 발생하지 않는 공구제작이 가능할 것으로 예상된다. 본 연구에서는 무전해 니켈도금 용액개발과 도금공정 및 장치의 개발을 통하여 합성다이아몬드를 금속으로 코팅하는 제품과 입방정질화붕소(CBN)를 금속으로 코팅하는 제품 중 Ni-P 무전해 도금에 있어서 석출 모양을 제어할 수 있는 첨가제를 개발함으로서 선진개발사 선호 형상인 연삭휠상의 CBN 손실을 최소화할 수 있는 모양인 Botryoidal type(포도송이 모양)과 Anisotropic 증착 제어를 통하여 Spiky type(침상 모양)에 대한 안정적인 Morphology를 얻을 수 있는 용액개발을 목표로 하였으며, 첨가제 및 교반장치 개선을 통하여 도금속도를 향상시킴으로서, 현재 전 세계적으로 생산되고 있는 제품군에 대한 120mesh이상의 경우에도 원하는 형상인 Botryoidal type(포도송이 모양)과 Spiky type(침상 모양)을 얻을 수 있는 고부가가치 표면처리 기술을 확보하고자 하였다. 특히 연삭재료 중 CBN(Cubic Boron Nitride) 입자상에 무전해 도금법에 의한 불규칙한 모양의 금속코팅 시 연삭공구에 연삭재료의 접착을 증진시키기 위한 기술로 CBN 분말상 무전해 니켈 도금층의 석출형상을 제어하기 위한 기술개발을 시도하였으며, 무전해 Ni도금 용액개발과 도금공정 및 장치의 개발을 통하여 합성다이아몬드를 금속으로 코팅하는 제품과 입방정질화붕소를 금속으로 코팅하는 제품 중 Ni-P 무전해 도금에 있어서 석출 모양을 제어할 수 있는 첨가제를 개발함으로서 목표 형상인 연삭휠상의 CBN 손실을 최소화할 수 있는 모양인 Botryoidal type(포도송이 모양)과 Anisotropic 증착 제어를 통하여 Spiky type(침상 모양)에 대한 안정적인 Morphology를 얻을 수 있는 용액개발을 목표로 하였고, 첨가제 및 교반장치 개발을 통하여 석출속도를 향상시키고자 하였다. 본 연구를 통하여 무전해도금욕의 첨가제 역할에 대하여 고찰하여 표면처리를 통하여 석출형상을 제어함으로써 제품의 특성에 맞는 기능을 부여하는 연구를 수행하였다. 또한 세라믹 소재를 금속화하기 위한 다양한 연구가운데 본 연구에서는 세라믹 소재 중 알루미나 세라믹 기판을 금속화하기 위한 표면처리 공정을 연구 개발하고자 하며, 그 과정 중 금속과 기판과의 밀착강도를 높이는 방법으로 제안되는 표면개질법인 IAR(Ion Assisted Reaction)법을 이용하여 세라믹 표면을 활성화시키고 친수성을 부여하여 이에 따른 금속과 세라믹 기판과의 밀착강도에 미치는 표면개질 조건에 대하여 고찰하였으며, 표면개질 소재 및 금속화에 따른 밀착강도 시험에 대한 연구를 병행하였다. In this study, the functional property as a super abrasive material was secured for CBN powder by the electroless Ni-P plating on the surface of the particle. The plating solution has been prepared to control the surface morphology by regulating surfactants and process conditions. For the surface modification of ceramic board, IAR(ion assisted reaction) was introduced to pre-treat the ceramic surface. The effects of processing parameters on the surface morphology of CBN powder and adhesion strength between metal and ceramic were discussed. Finally photo etching property was evaluated according to the parameters of surface modification. The results are summarized as follows; 1. A stable plating tendency was achieved from 1 hour after quantitatively dropping reducing agent. It was observed that over 50% of weight gain by Ni-P coating was obtained on the surface of CBN super abrasive powder. 2. The morphology of the Ni-P coating layer is consisted of botryoidal and spiky type and it could be controlled by regulating processing parameters. 3. Superior characteristic in terms of surface morphology was found in the nonionic surfactant XL-80N. It was found that XL-80N considerably decreased surface tension of CBN powder and Ni-P alloy surface then enhance wettability as well as plating rate. 4. Metal coated CBN powder as a raw material of resin bond wheel has been developed through this investigation. It was observed that crystallization behaviour was changed according to the content of phosphorus. The fraction of amorphous phase increased as the phosphorus content increased and amorphous like fine nickel aggregate was formed at the 5.8% of phosphorus. The microcrystalline Ni-P deposits obtained from plating baths had the <111> preferred orientation which persisted even after phase transformation into Ni3P and nickel. 5. The adhesion strength of electroless Cu and electro Cu plating layer accompanied by IAR treatment of ceramic board shows 150 gf/cm which is three times higher than that without the IAR treatment. 6. The wettability and adhesion strength between ceramic and Cu plating layer increased as the irradiation quantity of N₂ increased in the IAR treatment. The adhesion strength significantly increased to 450 gf/cm after formation of Cr seed. It was concluded that the surface roughness is more dominant factor on the adhesion strength of plating layer than the wettability gradient which is conventional concept. 7. Optimum etching parameters were found at the 2.5M of etchant and 1.8kgf/㎠ of injection pressure. Higher injection pressure over 1.8kgf/㎠ is believed to cause insufficient reaction between etchant and Cu.

還元擴散法에 依한 TiFe와 TiFe₁xMx(M=Mn, Ni Co. 0.1≤X≤0.3)系 水素貯藏合金의 製造 및 水素貯藏特性에 關한 硏究

강길구 忠南大學校 2001 국내박사

This thesis has made TiFe systemic hydrogen storage alloys by the most economical reduction diffusion process in the functional materials. The reduction materials were used by Mg and chip typical Ca. Each reduction materials was added 1.5 times due to being lost vaporization and reduction in these TiFe systemic hydrogen storage alloys. MgO was removed by HCl, H₂SO₄, NH₄Cl and CaO was removed by H₂O+NH₄Cl. These TiFe systemic hydrogen storage alloys were observed by XRD, SEM and the characteristic of the hydrogen storage of the hydrogen storage alloys was estimated by P-C-T which was the most important apparatus in these field. They were on the basic of Fe TiO₂,TiFe_(1-x)M_x(M=Mg, Ni, Co, 0.1≤x≤0.3) were made from a little adding Mn, Ni and Co. Thus, I’d like to provide the elementary data of the hydrogen storage alloys as the new functional material, which were presented the characteristic of hydrogen storage by P-C-T which was the most important apparatus. The major experimental results were summarized as follows. 1. TiFe systemic hydrogen storage alloys were manufactured when atonic weight by 50:50, at 1200c, 2hr of reaction by using Mg and Ca as the reduction material. The results of these parts are as follows. Fe and Ti remained because Mg which was 1.5 times of the theoretic contents didn't react completely as the reductions to remove MgO. I had reacted them for 30minutes as HC1, H₂SO₄and NH₄Cl, but MgO was not removed completely. Ca which added 1.5 times of the theoretic contents was not removed by H₂O, NH₄C1 and H₂O+NH₄Cl. CaO was removed completely when it was reacted NH₄Cl and H₂O for 30minutes. TiFe system storage alloys had the porous. 2. To make TiFe systemic hydrogen storage alloys, Ca which had good activity as reduction was added 1.5 times as much as theoretical contents for losing by vaporization and reaction. TiO₂and Fe powder were made when atomic weight was 50:50 at 1000, 1200℃ and 1, 2, 4, 6hr. The produced TiFe hydrogen storage alloys got rid of CaO through washing by acid and washing by water. It was similar to the melting methods at 1200℃, 2hr, 6hr from XRD at good measure results. If hydrogen storage alloys didn't contents initial activity first, TiFe systemic hydrogen storage alloys at 1200℃, 2hr were not reacted at all. If the initial activity treatments were done first at 450℃, 5MPa, the reaction occurred easily. 3. The second plateau appeared when the reaction temperature with hydrogen was at 30, 40, 55, 75℃. It obtained the same results as melting methods at 40℃ and the maximum hydrogen contents were highest at 40℃, when it was more than 40℃, the more temperature increased, the more maximum hydrogen contents decreased. 4. To make TiFe_(1-x)M_x, system hydrogen storage alloys, which were made by washing by acid and washing by water and XRD, SEM at 1200℃, 2hr, 6hr, adding to M=Mn, Ni and Co, 0.1≤x≤0.3 at the same methods as TiFe system hydrogen storage alloys. I realized that hydrogen storage alloys were produced easily. 5. To improve the initial activity adding to Mn, hydrogen storage alloys which added Mn stored hydrogen at 40℃, through didn't perform the initial activity treatment and the second plateau of TiFe hydrogen storage alloys were improved therefore, the more Mn increased, the more dissociation pressure decreased, the more maximum hydrogen contents decreased. 6. To improve the initial activity, when Ni was added, the intial activity was improved, the hydrogen was stored easily at 40℃ under the hydrogen and reaction temperature, but the more Ni added, the more hydrogen contents increased, and improved the second plateau of TiFe system hydrogen storage alloys, the more Ni increased, the more narrow the width was, the more slope increased and the more Ni increased, the less maximum hydrogen contents was. 7. To improve the initial activity, Co stored hydrogen at 40℃, 5MPa in hydrogen pressure though Co didn't treat the initial activity. The more slop of plateau and the dissociation pressure increased, the more maximum hydrogen contents decreased.

感濕材料 製造 및 特性을 應用한 濕度센서의 연구

채인창 충남대학교 대학원 2002 국내석사

A study for Humidity Sensor using The Charcteristics of Sensing moisture Polyvinyl alcohol is a common hydrophilic polymer but shows a significant impedance response with changing relative humidity only above 60% RH. Fabricating simply a polyvinyl alcohol film as humidity sensor lacks durability and also shows high impedance. To overcome this problem, cross-linking of polyvinyl alcohol was done with 4-styrene sulfonate (sodium salt) in presence of ferrous ions. The best results as a humidity sensor material were obtained when polyvinyl alcohol was cross-linked with 4-styrene sulfonate in presence of ferrous ions at a temperature of 140℃ for about 1 h and when polyvinyl alcohol, 4-styrene sulfonate (sodium salt hydrate) and FeCl_2·4H_2O were taken in a weight ratio of 10:2:3 respectively. The structure of the polymeric material was established using NMR and infra-red spectroscopy, to be a co-polymeric material in presence of ferrous ions. The polymeric mixture of the three materials made in water was casted on an alumina substrate (size 7.5mm×7.2mm×0.38mm) prefabricated with interdigitated gold electrodes and was cured at a temperature of 140℃. The results demonstrate that the logarithm of the resistance decreased linearly with increase in %RH in a range of 30-92% RH. Other factors viz. stability, sensitivity and response time for the fabricated sensor were also determined, * Polyvinyl alcohol (PVA) is a cheap and common hydrophilic polymer but lacks durability against moisture and shows high impedance. In this paper, several PVA based humidity sensors cross-linking it with m-benzenedisulphonate sodium salt (MBDS) in presence of various electrolytes were prepared. However, cross-linking PVA with MBDS in presence of ferrous ions showed the maximum sensitivity against relative humidity. Best results were obtained when cross-linking was done by curing the film on an alumina substrate, printed with gold electrodes at 150-160℃ and in a weight ratio of 25:5:9 for PVA : MBDS : FeCl_2·4H_2O composition. Dependence of resistance on the relative humidity(RH) showed linearity between 35 to 85%RH. Other factors viz. temperature dependence, response time were also measured. The humidity sensitive characteristice of the sensor did not change even after soaking in water for 100 min.

음향방출을 이용한 금속 및 콘크리트의 균열거동에 관한 연구

정중채 충남대학교 대학원 2002 국내박사

By using the relation between stress intensity factor and AE parameter, new approach method for assessing the crack length and detectability of crack was proposed. Laboratory experiment was carried out to identify AE characteristics of fatigue cracks for compact tension specimen. The relationship between the stress intensity factor and AE singles activity as well as the analysis of conventional AE parameter was discussed. As hits, showed the almost same trend in their increase as the number of fatigue cycle increased. From the comparison of peak amplitude and AE energy with the stress intensity factor, it was verified that the higher stress intensity factors generated AE signals with higher peak amplitude and a larger number of AE counts. If we can get more reliable database for the relation between AE parameters and stress intensity factor, this approach will provide good information for evaluation both the existence of crack and the minimum detectable size of crack. The objective of this study was to investigate the effect of crack opening and closure in the AE activities during fatigue test. Laboratory experiment using various materials and test conditions was carried out to identify AE characteristics during fatigue crack propagation. Compact tension specimens of 2024 T4, 6061-T6, 7075-T6 aluminum alloy and SWS 490B structural steel were prepared for fatigue test. The AE activities were analyzed based on the phase of the loading cycle at which they occur. From this a preliminary result it was found that AE activity was considerably affected by the mechanical properties, which has different microstructure. Generally, most of AE signals were generated at the time of early opening and closure of crack, not in the peak loading of cycle. Also the point of high occurrence of AE event was different for each specimen. However, in the same material, the trend of AE activity was not affected by the change of cycle frequencies (0.1, 0.2, 1, Hz). Opening and closure behavior according to each material is moved, AE occurring appearance is very differently observed. That is the AE when fatigue crack is moved depending on the microstructure or physical properties, and that it has a different appearance depending on tensile strength, yield strength and elongation. The AE behavior of reinforced concrete beams tested under flexural loading was investigated to characterize and identify the source of damage. This research was aimed at identifying the characteristic AE response associated with micro-crack development, localized crack propagation and debonding of the reinforcing steel. And this study was to investigate the effect of damage of concrete beams in the AE activities during four-point bending test. A reinforced and plain concrete beam specimens were made in order to reproduce the damage mechanism. In case of plain concrete, to simulate the burning damage, specimen were exposed in high temperature environment of 200,400,600℃ and in moisture environment. The beams were tested using four-point cyclic step loading. The AE response was analyzed to obtain key parameters such as the time history of AE events, the total number and rate of AE events, and the characteristic features of the waveform. Initial analysis of the AE signal has shown that a clear difference in the AE response is observed depending on the source of the damage. The Felicity ratio exhibited a correlation with the overall damage level, while the number of AE events during unloading can be an effective criterion to estimate the level of burning distress in reinforced concrete structures. Consequently, AE measurement characterization appears to provide a promising approach for estimating the level of deterioration in reinforced concrete structure.

自傳燃燒高溫合成法에 衣한 TiNi 金屬間化合物 製造

박상규 충남대학교 1996 국내석사

자전연소합성법에 의한 텅스텐 산화물 및 회중석의 환원 반응 특성

서동희 충남대학교 대학원 2001 국내박사

Tungsten has a high melting point (3410℃) as well as high-temperature strength and electrical conductivity. Thus, it finds wide applications in illumination, electronics, electrical contact. and heat-resistant materials. It. is also the main raw material for the hard alloys used in cutting tools, antifriction tools, and high-speed steels. In industry, tungsten is usually obtained by reduction of tungsten oxide with hydrogen in furnaces with electric heat-up, because WO₃+H₂reaction is endothermic. Lately, many pure substances including carbides, borides, intermetallic compounds, nitrides, and silicides have been prepared by the self-propagating light temperature synthesis(SHS) process using their high exothermic heats of formation. I he process is relatively simple and rapid without requiring much external heat. supply. That's why application of the SHS technology is one of the most promising method of tungsten powder production. Without controlling SHS process, however, required quality of products can't be provided. It is well-known that the mode of combustion-front propagation divided into two large groups, gasless and gaseous combustion. The former is relatively simple and has been extensively studied, whereas the heat and mass transportation phenomena of the latter is not clearly understood. Moreover, the report on the quantitative study for the gaseous combustion as of WO₃-Zn system is rare. The purpose of this study was to find out the processing parameters which govern synthesis conditions, and the effects of the such parameters as argon pressure, green mixture density, compact size and components ratio were systematically studied. And, the size control of tungsten powder and leaching test were investigated. The results of these studies are as follows; 1. Preperation of tungsten powder by the combustion of WO₃-Zn and WO₃-Mg 1) Zn vapor was discovered to significantly affect the combustion parameters (Δh, Δm, u and T), also the evaporation of zinc was suppressed as the Ar pressure increased. Hence, combustion limits were determined by Ar pressure and sample density for the system WO₃. 2) The most important variable in the reduction of WO₃by Mg was the molar ratio. Particle size and Mixing time also affected the result. Although the stoichiometric molar ratio Mg/WO₃is 3, a ration of 4 was necessary for complete reduction. 3) Increased compaction pressure reduced the distance between the reactant solids and held the reaction heat longer in the sample. This made the product rounder and larger. 2. Preperation of tungsten powder by the combustion of CaWO₄-Mg 1) The combustion characteristics of W reduction from CaWO₄ with Mg was carried out. The reduction process was shown to occur mainly by the following reaction. CaWO_4(s)+Mg_(con) ↔ CaO_(e)+MgO_(e)+W_(e)+Mg_(g) 2) Mg vapor was discovered to significantly affect the combustion parameters (T_c,u, Δm, Δh). Those effects were decreased by increasing the argon pressure. 3) The tungsten particle size increased as the sample diameter and combustion temperature increased, because the particle grew well by the decreased cooling rate. Also, the combustion parameters was successfully controlled by using a diluent or controlling argon pressure. 3. Size control of tungsten powder 1) Increased compaction pressure caused better contact among reactants and held the reactant heat longer in the sample. This made the products rounder and larger. It was possible to control the tungsten particle size from 1 to 5㎛ by various compaction pressures. 2) The produced tungsten powder had a higher purity than the reactant by vaporization of impurities during SHS reaction and dissolution by leaching solution.

SHS와 HPCS법에 의한 Ni-aluminide계 金屬間化合物 製造

정중채 忠南大學校 1996 국내석사

固體高分子電解質과 金屬間의 電氣化學反應 및 그 應用

유성남 충남대학교 대학원 2002 국내박사

In this study, the electrochemical reaction of solid polymer electrolyte to metals and its applications have been researched. Specifically, the purposes of this study were to devise the new method for water electrolysis using metal plating (mainly Pt) on solid polymer electrolyte as an electrode, to produce O₂and H₂at low prices in a safer way by this new method, and to obtain O₃at low prices in a safer way by immediate transforming O₂which was produced in the process of electrolyzing water into O₃. The results obtained through this study which was on the electrochemical reaction of solid polymer electrolyte to metals and its applications were as following. 1) Pt(NH₃)₄Cl₂·H₂O and H₂O and H₂Pt(OH)_6 were synthesised by the following steps. After H₂PtCl_6 was made by melting Pt in aqua regia, H₂PtCl₄could be made from that. t-Pt(NH₃)₂Cl₂was prepared from H₂PtCl₄made like above-mentioned, and then Pt(NH₃)₄Cl₂·H₂O with high purity was prepared from t-Pt(NH₃)₂Cl₂. H₂PtCl_6 was made by melting Pt in aqua regia, and Na₂Pt(OH)_6 could be made from that. H₂Pt(OH)_6 was prepared by letting Na₂Pt(OH)_6 made like this react to HCl through cation exchange membrane. 2) The method of Pt plating on solid polymer electrolyte surface with electroless plating using Pt(NH₃)₄Cl₂·H₂O and N₂H₄was developed. The appropriate dipping time in Pt(NH₃)₄Cl₂·H₂O was about 20 minutes and reduction time in N₂H₄solution was about 1.5 hours. At more or less than that, the condition of plating layer on soild polymer electrolyte surface was worsened and the movement of H was decreased by the loss of ion exchange lines. 3) Electroplating was used in Pt plating on Ti mesh. H₂Pt(OH)_6 was used as Pt plating reagent. In plating, Pt wire was used as an anode and Ti mesh to be plated as a cathode. In this case, the temperature of plating solution at 75℃±3℃ and the amperage range of 2.5±0.002V, 0.5±0.1A were the optimum plating conditions. To increase Pt plating time on Ti mesh didn't have influence on the surface condition except for accompanying the thickness of Pt plating layer. 4) Electrodepositing was used in β-PbO₂depositing on Ti mesh. First of all, Pt plating on Ti mesh was performed because there was the difficulty in direct β-PbO₂depositing on Ti mesh. Pb(NO₃)₂was used as β- PbO₂depositing reagent. In this case, the temperature of 65℃±3℃ and the amperage range of 3.6±0.0002V, 0.7±0.1A were the optimum depositing conditions. In depositing, Pt plated Ti mesh was used as an anode and Ti mesh as a cathode. In β-PbO₂depositing on Ti mesh, Pt plating time of the base part was at least more than 10 minutes, and β-PbO₂depositing time was at least more than 2 minutes. 5) Solid polymer electrolyte water electrolysis cell consisted of Pt plated solid polymer electrolyte on both sides, β-PbO₂deposited Ti mesh as an anode, Pt plated Ti mesh as a cathode, and each electrode had three sheets of Ti mesh, In addition to these, rubber, polymer, and Ti plate gasket were devised and used. And the cell combined with these items was tied with Al plate to fix up. 6) With water electrolysis using solid polymer electrolyte water electrolysis cell, the generation of O₃was confirmed at the range of 3.2~3.6V, 1.0~1.5A/㎠, and the devised O₃and H₂generator with amperage of 6V, 100A was based on this.

廢電池로부터 有價金屬回收 및 高機能性 素材化

김태현 忠南大學校 2008 국내박사

Fabrication and Oxygen permeation properties of perovskite-type Oxygen permeation ceramic membrane

임경태 忠南大學校 大學院 2001 국내석사

La_0.6Sr_0.4Co_0.2Fe_0.8O_3 _δ powders were synthesized by coprecipitation(CO), citrate(CT) and solid-state reaction(SS) methods for oxygen permeation membrane. Dense perovskite-structured membranes were fabricated by cold isostatic pressing, followed by sintering at 1300℃ for 3hr. Perovskite-type structures of all LSCF powders and membranes were confirmed by X-ray diffraction analysis. Whereas the SS-powder had the lowest surface area(2.24㎡/g), the powder showed the finest particle size(0.93㎛). Although lots of agglomerates were found in the CO and CT-powders, most of particles consisted of powders with the average size of 0.2 ~0.3㎛. According to the ICP analysis, most of powders were evaluated to have desired compositions close to the stoichiometry except the CO-powder. Much strontium deficiency was found during washing and filtering in the coprecipitation process. While the CO-membrane showed the highest sintered density(98.3%), CT-membrane had the lowest density(87%) in spite of longer sintering time(10h). Lower densification was due to the agglomeration of fine pores. Whereas CO-membrane showed the highest hardness and fracture toughness, SS-membrane exhibited the highest flexural strength. Accordingly, The CO-membrane was not suited for the oxygen permeation membrane because of Sr deficiency and phase separation. In addition, the CT-membrane was also not suited for the membrane because of larger pores. On the other hand, the SP and SS 6428 membrane showed smaller pore size and uniform pore distribution. Basing upon the above results, the SS-6428 membrane was decided for a suitable oxygen permeation membrane because of delicate composition controllability, high sintered density and good mechanical properties. Sintering behavior and microstructure of the SS-6428 membrane was investigated according to different sintering temperature. According to sintering temperature, sintering density, shrinkage rate and bending strength of the SS-6428 membrane showed the identical tendency. Notable densification and increase of sintered density were achieved between 1150℃ and 1200℃. The highest density and bending strength appeared at 1300℃. Oxygen permeation according to increased temperature were investigated. Lower permeation fluxes between 700℃ and 800℃ and comparatively higher permeation fluxes between 850℃ and 950℃ were measured. Membrane with 1.7mm thickness showed steady state oxygen permeation in 100min at 850℃. Oxygen permeation fluxes increased when membrane thickness was thinner and oxygen partial pressure gradient increased.