Microstructure and High Temperature Mechanical Property of Fe–Cr–B Based Metal/Ceramic Composite Manufactured by Metal Injection Molding Process

Kee‑Ahn Lee,Jin‑Han Gwon,윤태식 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

This study investigated the microstructure and the room and high temperature mechanical properties of Fe–Cr–B alloy manufacturedby metal injection molding. In addition, hot isostatic pressing was performed to increase the density of the material,and a comparison of properties was made. Microstructural observation confirmed a bi-continuous structure composedof a three-dimensional network of α-Fe phase and (Cr,Fe)2B phase. The HIPed specimen featured a well-formed adhesionbetween the α-Fe phase and boride, and the number of fine pores was significantly reduced. The tensile results confirmed thatthe HIPed specimen (RT to 900 °C) had higher strengths compared to the as-sintered specimen, and the change of elongationstarting from 700 °C was significantly greater in the HIPed specimen. Fractography suggested that cracks propagatedmostly along the interface between the α-Fe matrix and boride in the as-sintered specimen, while direct fracture of boridewas observed in addition to interface separation in the HIPed specimen.

외상성 횡격막 손상

안성국,이상목,이기형,고석환,김용호,박호철,고영관,조규석 대한응급의학회 1995 대한응급의학회지 Vol.6 No.1

Fifty two cases of traumatic diaphragmatic injuries that we have experienced from Jan. 1973 to Oct. 1994 were evaluated. The following results were obtained. The age of the patient was ranged from 1 to 74 years. Male was 38 and female was 14 in number with a ratio of 2.7 : 1. The traumatic diaphragmatic injuries were due to blunt trauma in 35 cases(motor vehicle accident 25, fall down 8, press 1, kick by fight 1) and penetrating trauma in 17 cases(stab wound 15, shot wound 1, explosion 1). In the blunt trauma, the preoperative diagnosis of the diaphragmatic injury was possible in 25 out of 35 cases(71%) and in the penetrating trauma, 15 out of 17 cases(88%). In the blunt trauma, the repture site was located in the left in 22 cases(63%) and in the right in 13 cases(31%). In the penetrating trauma, the rupture site was located in the left in 9 cases(53%) and in the right in 8 cases(47%). In the blunt trauma, 20 cases(63%) were treated within 24 hours and in the penetrating, 15 cases(88%) within 24 hours. In the blunt trauma, the herniated organs into the thorax were stomach(7), omentum(6), spleen(6), liver(5), colon(4), small bowel(2) and in the penetrating, stomach(7), colon(6), omentum(3), liver(2), and spleen(1) were herniated. Injury severity score(ISS) of 35-blunt trauma ranged from 11 to 66 with mean value of 30.6. Mean ISS of survivors and nonsurvivors was 27.6 and 52.7 respectively. The diaphragmatic repair of 49 cases was performed with thoracic approach in 23 cases, thoracoabdominal approach in 7 cases and abdominal approach in 19 cases, and 3 cases were not operated. The postoperative complication and mortality were developed in 16 out of 49 cases(33%) and in 5 cases(9.6%) respectively, and the causes of death were hypovolemic shock(1), combined head injury(2), asphyxia(1), and pulomnary edema and renal failure(1). In conclusion, the injuries of the diaphragm should be suspected in all patients with severe blunt trauma or penetrating injuries at thorax and upper abdominal area near the diaphragm. All of the cases had associated injury and most of deaths were related to the severity of associated injuries.

몇가지 작물중 침투성 살충제 Carbofuran의 잔류량 분석

이재구,최신종,경기성,안기창,권정욱 충북대학교 농업과학기술연구소 1999 農業科學硏究 Vol.16 No.-

In order to ascertain the safety of the systemic insecticide carbofuran - treated crops. garlic, peanut and potato were collected randomly from markets near the major producing farms and analyzed for the residues of carbofuran and its main metabolite, 3-hydroxycarbofuran. The in vitro metabolism of carbofuran in phosphate buffer extracts of the crops was investigated. The results obtained were as follows. 1.The recoveries of carbofuran and 3- hydroxycarbofuran from the spiked samples were 92~ 100% in all samples. The detection limit and minimum amount of carbofuran detected were 0.02ppm and 0.1ng, and those of 3-hydroxycarbofuran 0.06ppm and 0.3ng, respectively. 2.Two mature garlic samples out of 20 contained 0.13 and 0.07ppm of carbofuran, respectively, showing a detection frequancy of 10%. The residue level was less than the maximum residue limit(0.5ppm) set by the health authorities in Korea. Only one mature garlic sample out of 20 contained 0.13ppm of 3-hydroxycarbofuran. 3.The residues of carbofuran and 3-hydroxycarbofuran in the immature garlic, peanut and potato samples were less than the detection limits. 4.The application of carbofuran to the fields of garlic, peanut and potato would be safe, considering that the estimated maximum acceptable daily intake of carbofuran from garlic was 0.0007mg which is 0.13% of the maximum acceptable daily intake(0.55mg) . 5.Carbofuran was hydrolyzed in vitro mainly to carbofuran phenol(m/z 164) in phosphate buffer extracts of the three crops in contrast to the major oxidative metabolism in situ. The amount of the metabolite increased with the incubation time.

질화 분위기에서 결정화 된 Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ 연자성 합금의 자기적 성질

이기선,박인수,이기안,김문철,장석훈 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.11

Amorphous Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ alloy was crystallized in nitriding atmosphere of mixture gas of NH₃ and hydrogen. The crystallization at 823K showed the high electrical resistivity ranging from 494 to 538 mW-cm, which was higher level compared with nano-crystalline Fe_(73.5)Si_(13.5)B_(9)Cu₁Nb₃ alloy with a resistivity of about 110 mW-cm. Through the nitridation treatments, the amorphous alloy was transformed into nano-sized crystalline Fe3Si including iron nitrides such as γ' -Fe₄N phases. EPMA-concentration depth profiles confirmed an existence of nitrogen-rich region on the surface of the alloy ribbon, leading to the preferential formation of g -Fe4N phase. The formation of γ' -Fe₄N phase leaded to an increase of the resistivity and provided stable permeability and a low core loss at high frequency.

Two Stage 발효에 의한 고산도 식초 생산

이영철,이금용,김형찬,박기범,유익제,안평욱,최춘언,손세형 한국산업미생물학회 1992 한국미생물·생명공학회지 Vol.20 No.6

산업적으로 산도 17.0% 이상의 고산도 식초를 생산하기 위하여 반연속식인 1st stage와 유가식인 2nd stage로 구성된 two stage 초산 발효를 온도 30 ℃, 교반속도 600 rpm, 통기량 0.1 vvm에서 실시하였다. 1st stage에서 초기 에탄올 농도를 50.0 g/ℓ, 잔류 에탄올 농도를 5.0 g/ℓ로 정하여 반연속적으로 초산발효를 하고, 2nd stage 에서 발효시간의 경과에 따라 에탄올을 유가식으로 첨가하여 초산발효액내의 에탄올 농도를 5.0 g/ℓ에서 10.0 g/ℓ로 유지했을 때 산도가 17.6%인 고산도 식초를 생산할 수 있었으며, 또한 이 ??의 최대 초산 생산성은 3.3 g/ℓ·hr였다. The production of vinegar containing 16.0 ∼18.0% of acetic acid was examined in two stage fermentation consisting of semi-continuous and fed-batch type. The optimum conditions were obtained when the fermentation was carried out at agitation of 600 rpm, aeration of 0.1 vvm and temperature of 30℃. The initial and residual ethanol concentration in 1st stage were 50.0 g/ℓ and 5.0 g/ℓ, respectively, and the ethanol concentration in 2nd stage was maintained from 5.0 to 10.0 g/ℓ. The maximum productivity was 3.3 g/ℓ-hr and the acidity was 17.6% after the two days of acetic acid fermentation.

저열팽창성 Fe-29Ni-17Co 코바 합금의 고온균열 발생과 고온연성에 미치는 S 및 Mn의 영향

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

The effect of S & Mn on the hot ductility of Fe-29Ni-17Co Kovar alloy and the mechanism of high temperature cracking occurrence were investigated. It has been found that the brittle intergranular fracture at high temperature cracking is closely associated with the sulfide along grain boundary. Experimental results showed, especially when the S content was high and the Mn content was free, that small cavities could be nucleated easily on FeS particles along grain boundary and propagated fast at high temperature. The hot ductility of Kovar alloy was drastically increased with the addition of Mn and it was also increased with decreasing S content. SEM and FE-SEM analyses showed that the Mn addition in this alloy could cause ductile intergranular fracture appearance below 1150℃ by the precipitation of MnS. It was proposed from the results that the addition of Mn and optimum S content (below 30 ppm) in Kovar alloy was necessary in order to reduce the hot cracking susceptibility.

β-CuZn 합금의 인장 및 파괴 거동에 미치는 변형률 속도와 온도의 영향

이기안,이종수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

A series of tensile tests were carried out on a B2-type b-CuZn alloy in the temperature range, room temperature to 400oC at three different strain rates (10^(-5) sec^(-1), 10^(-4) sec^(-1), 5.2x10^(-2) sec^(-1)). The stress-strain curves could be divided into three types. Type I indicates a remarkably linear sustained work hardening to fracture, type II work hardening and subsequent necking, type III yield drop behavior and stress saturation, respectively; corresponding to the insensitive yield stress region, anomalous yield stress region, and yield stress decreasing region, in the yield strength vs. temperature graph. The ultimate tensile strength basically decreased as temperature increased, only showing characterized strength hump-up region just below T_(p). The fracture mode was changed mainly from transgranular at room temperature to intergranular at high temperatures. The elongation increases with increasing temperature in region I, and then slightly decreases in region II (anomalous yield stress region). When the specimens were tensile-fractured at high temperatures (region III, above Tp), the elongation drastically increased with decreasing strain rate, for instance from 12% at 5.2x10^(-2) sec^(-1) to 87% at 10^(-5) sec^(-1). The dependence of ductility on strain rate was mainly attributed to the thermally activated <100> dislocation climb, inducing stress relief at the grain boundaries, as evidenced by microvoids at grain facets.

非特異性 PHOSPHATASE에 關한 硏究 : 사람 胎盤 Alkaline Phosphatase의 燐蛋白 燐酸水解活性에 關하여

李民化,安鳳煥,李起榮,曺仲東 全南大醫大 1980 전남의대학술지 Vol.17 No.2

β-CuZn 합금의 항복강도 이상거동에 미치는 변형률 속도와 온도의 영향

이기안,장영원,이종수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3

A series of tensile and load relaxation behaviors in B2 type β-CuZn alloy have been examined to clarify the strain rate & the temperature dependence of yield stress anomaly. It has been found in tensile tests that the region showing anomalous peak of yield stress moves to a higher stress and higher temperature region with increasing strain rate. The anomalous yielding region below peak temperature(T_p) revealed slightly positive strain rate dependence, while the region above T_p showed considerably positive strain rate dependence. The slip lines formed below peak temperatures (T_P) were clearly visible with naked eye(coarse slip lines), and became finer near T_p(fine slip lines), while they disappeared completely above T_p. Based on the different tendency of temperature and strain rate dependence of anomalous yielding as the above-mentioned results, two types of deformation modes were suggested and incorporated into the flow curve analysis, which was in accord well with the experimental results. The slightly positive strain rate dependence of yield stress anomaly indicated that the yield stress anomaly in β-CuZn alloy mainly seemed to be attributed to the vacancy hardening.

Fe-29%Ni-17%Co 코바 합금의 고온 내산화성 및 열간 가공성에 미치는 Mo 첨가의 영향

이기안,조창완,성병근,김병문,김문철 대한금속ᆞ재료학회 2006 대한금속·재료학회지 Vol.44 No.3