• 한국재료학회지
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• 제10권6호
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• pp.437-444
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• 2000

기판온도, 박막조성 및 증착후 열처리 등의 조건에 따른 ${La_{1-x}}{Sr_x}{MnO_{3-{\delta}}}$(0.19$\leq$x$\leq$0.31) 박막의 결절구조와 전기전도 특성을 조사하였다. 스퍼터법을 이용하여 $500^{\circ}C$에서 증착된 박막은 강한 <001> 우선배향성과 유사정방정(pseudo-tetrag-onal, a/c-=0.97) 결정체를 나타냈다. 이러한 박막의 단위포는 산소분위기 내에서 증착후 열처리에 의하여 입장정 결정계로 변하였다. $La_{0.67}Sr_{0.33}MnO_3$ 조성의 주타겟과 $La_{0.3}Sr_{0.7}MnO_3$조성의 보조타겟을 동시에 이용하여 박막의 조성을 조절하였다. 보조타겟의 개수에 따라 박막내의 Sr 함량(x)은 0.19-0.31 범위의 값을 나타내었으며, x값이 0.19로부터 0.31로 증가시 금소-반도체의 전이 온도가 상승하였고, 전지비저항이 대체로 감소하였다. 0.18 T의 자기장 하에서, $La_{0.69}Sr_{0.31}MnO_3$조성의 박막의 자기저항변화 MR((%) = (${\rho}_o-{\rho}_H/{\rho}_H$)는 약 390% 이었다.

• 한국전기전자재료학회논문지
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• 제22권8호
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• pp.665-670
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• 2009

Lead-free piezoelectric ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO and $MnO_2$ were fabricated using the conventional oxide-mixing technique. With increasing content of CuO and $MnO_2$, the dielectric constant(${\varepsilon}_{33}$) and mechanical quality factor($Q_m$) value increased, while electromechanical coupling factor($K_p$) and piezoelectric constant($d_{33}$) decreased. The piezoelectric and dielectric properties ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO 2.461 wt% and $MnO_2$ 0.538 wt% at sintered temperature $1050\;^{\circ}C$ were attained ${\varepsilon}_{33}$ = 403, $K_p$ = 15, $Q_m$ = 122 and $d_{33}$ = 36 pC/N. Based on response surface methodology results using design of experiment, it was concluded that ($Na_{1/2}K_{1/2}$)$NbO_3$ doped with CuO 0.477 wt% and $MnO_2$ 0.269 wt% has possibility composition of being used for piezoelectric transformer.

• 열처리공학회지
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• 제23권4호
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• pp.191-197
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• 2010

Zr addition is known as effective method to improve the anisotropy of steel due to the elongated MnS inclusions which are observed in hot forged steels. The aim of this research is to investigate the effect of Zr addition on the mechanical properties and manganese sulphide morphology of 0.27%C-Cr-Mo plastic mold steel. The ingots were prepared by vacuum induction melting and forged to ${\Phi}35mm$ round bar. Forged bars were quenched and tempered at $560{\sim}640^{\circ}C$ for 1 hour. Jominy test, microstructual observation, tensile test and Charpy impact test were conducted. The morphology of MnS inclusions was changed by Zr addition. The shape of MnS inclusions was not so much lengthened and controlled not to be elongated by Zr inclusions which surround the MnS inclusions. Tensile strength and yield strength of the tempered steels were not nearly affected by the addition of Zr, but elongation and reduction of area were decreased. Especially, the toughness of Zr added steels was deteriorated with increasing of Zr content. From the results of this study, it is assumed that anisotropy of steels was improved by the addition of Zr. However, impact toughness of the steel was significantly decreased by the excessive Zr addition (over 0.066%).

• 한국재료학회지
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• 제23권7호
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• pp.385-391
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• 2013

The influence of Cu and Ni on the ductile-brittle transition behavior of metastable austenitic Fe-18Cr-10Mn-N alloys with N contents below 0.5 wt.% was investigated in terms of austenite stability and microstructure. All the metastable austenitic Fe-18Cr-10Mn-N alloys exhibited a ductile-brittle transition behavior by unusual low-temperature brittle fracture, irrespective of Cu and/or Ni addition, and deformation-induced martensitic transformation occasionally occurred during Charpy impact testing at lower temperatures due to reduced austenite stability resulting from insufficient N content. The formation of deformation-induced martensite substantially increased the ductile-brittle transition temperature(DBTT) by deteriorating low-temperature toughness because the martensite was more brittle than the parent austenite phase beyond the energy absorbed during transformation, and its volume fraction was too small. On the other hand, the Cu addition to the metastable austenitic Fe-18Cr-10Mn-N alloy increased DBTT because the presence of ${\delta}$-ferrite had a negative effect on low-temperature toughness. However, the combined addition of Cu and Ni to the metastable austenitic Fe-18Cr-10Mn-N alloy decreased DBTT, compared to the sole addtion of Ni or Cu. This could be explained by the fact that the combined addition of Cu and Ni largely enhanced austenite stability, and suppressed the formation of deformation-induced martensite and ${\delta}$-ferrite in conjunction with the beneficial effect of Cu which may increase stacking fault energy, so that it allows cross-slip to occur and thus reduces the planarity of the deformation mechanism.

• 한국응용과학기술학회지
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• 제28권2호
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• pp.135-139
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• 2011

In order to make high-purity ferro-manganese from $Mn_3O_4$ waste dust, the application of aluminothermite process to the reduction of the waste dust was investigated. The mixture from $Mn_3O_4$ dust as metallic source and Al metal powder as the reductant ignited, and reduced with an extremely intense exothermic reaction. The rapid propagation of the aluminothermite reaction occurred spontaneously and stably by ignition of the mixture. The Manganese having some alloy elements emerged as liquids due to the high temperatures reached up to about $2,500^{\circ}C$ and separated from the liquid by their differences of specific gravity. The result of thermite reaction showed the fact that can be obtained high purity ferro-manganese which have over about 90% of manganese content and lower impurities such as C, P, S than those of KS D3712 specification. The recovery of manganese from $Mn_3O_4$ dust was lower level of about 65% than about 75% from manganese ore by electric furnace process, that is due to spatter loss because of its extremely intense thermite reaction. But it will be improved by the process designed to provide CaO as the cooler or to use the Al metal powder having larger particle size distribution.

• 공학논문집
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• 제5권1호
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• pp.63-72
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• 2004

Mn-Co-Ni 3성분계에 Fe의 첨가량을 변화시켜 따른 산화물 서미스터소결체(Mn-Co-Ni-Fe oxide)를 소성온도 1200~$1400^{\circ}C$에서 제조하여 전기저항특성을 조사한 결과, 결정상은 단일입방정 스피넬형 결정구조였고, 소성온도에 따른 전기전도도는 $1300^{\circ}C$에서 4시간 소결한 시미스터가 가장 높았다. 대체로 F-2를 제외하고는 Fe의 첨가량이 증가할 때 비저항은 증가하고 상대적으로 전기전도도는 감소한다. 특히 F-2의 조성에 있어서는 전기전도도가 1.4${\times}$$10^-3$${\ textohm}cm로 높았고 상대적으로 B정수는 2906K로 낮았다.

• 한국재료학회지
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• 제3권3호
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• pp.215-222
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• 1993

에폭시 수지를 개질하기 위하여 반응성 첨가제 Malononitrild(MN)을 Diglycidy1 ether fo vispenol A (CGEBA)/Methylene dianiline(MDA)계를 첨가하여 이 계의 경화 반응속도론과 경화반응메카니즘을 시차주사 열분석(DSC)과 적외선 흡수 분광법을 통해 관찰하였다. 경화반응속도론으로부터 MN으로 개질된 DGEBA/MDA는 완전히 경화를 이루기 위하여 $80^{\circ}C$로 부터 $170^{\circ}C$까지 $30^{\circ}C$간격으로 경화시킨 시료로 반응메카니즘을 고찰한 결과 PA(primary amine)-E(epoxide)그리고 E(epoxide)-OH(hydroxy1 group)반응 이외에 PA(primary amine)-CN(nitrile)과 CN(nitrile)-OH(hydroxy1 group)반응이 일어남을 알았다.

• 한국분말재료학회지
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• 제26권5호
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• pp.389-394
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• 2019

In the present study, we have investigated the effect of sintering process conditions on the stability of the austenite phase in the nanocrystalline Fe-5wt.%Mn-0.2wt.%C alloy. The stability and volume fraction of the austenite phase are the key factors that determine the mechanical properties of FeMnC alloys, because strain-induced austenite-martensite transformation occurs under the application of an external stress at room temperature. Nanocrystalline Fe-5wt.%Mn-0.2wt.%C samples are fabricated using the spark plasma sintering method. The stability of the austenite phase in the sintered samples is evaluated by X-ray diffraction analysis and hardness test. The volume fraction of austenite at room temperature increases as the sample is held for 10 min at the sintering temperature, because of carbon diffusion in austenite. Moreover, water quenching effectively prevents the formation of cementite during cooling, resulting in a higher volume fraction of austenite. Furthermore, it is found that the hardness is influenced by both the austenite carbon content and volume fraction.

• 한국해양학회지:바다
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• 제16권4호
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• pp.169-179
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• 2011

본 연구에서는 미량 금속의 농축 가능성이 제기되는 천수만 퇴적물에 대하여 미량 금속의 조절 요인과 농축 정도를 파악하고자 하였다. 천수만 전역에 걸쳐 27개의 표층 퇴적물을 채취하였으며, 입도, 비표면적, 유기탄소 및 탄산칼슘 함량과 주성분 및 미량 금속(Al, Fe, Na, K, Mg, Ca, Ti, Mn, P, S, Ba, Sr, Li, Co, Cr, Ni, Cu, Zn, As, Cd, Cs, Sc, V, Sn) 농도를 분석하였다. 퇴적물의 총 금속 농도는 크게 3 가지 요인(석영, 희석, 탄산칼슘, 굵은 모래 혹은 정장석)에 의해 조절되었는데 V, Co, Cr, Ni, Cu, Zn, As, Cd는 석영 희석 효과(quartz dilution effect)에 의해 Mn 및 As는 석영 희석 효과와 정장석(굵은 모래) 함량의 복합적 요인에 의해 조절되었다. 농축 인자(enrichment factor) 및 약산(1 M HCl) 용출 실험 결과 천수만 퇴적물에서 미량 금속은 농축되지 않았음을 알 수 있었으며 금속의 농도는 퇴적물의 지화학적 특성들로 잘 설명되었다. 특징적으로 As는 조립질 퇴적물에서도 세립질 퇴적물과 유사한 농도를 보여주었는데, 이것은 조립질 퇴적물 내 Mn 산화물(용출 부분) 및 정장석(잔류 부분)과 밀접한 관련이 있는 것으로 해석되었다. 따라서 퇴적물 중 As의 농축 정도를 평가할 경우, 모래질을 포함하는 시료는 모래질 부분을 따로 분리하거나 $16{\mu}m$보다 작은 세립질 퇴적물의 함량이 10% 이상인 시료만을 대상으로 하는 것이 합리적인 것으로 판단된다.

• 생약학회지
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• 제8권2호
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• pp.61-68
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• 1977

The content of micro inorganic compounds in the 145 kinds of crude drugs on market was determined with Model 207 Atomic Absorption Spectrophotometer and Model 306 Flameless A.A. Content of Fe, Cu, Ni, Mn, Cd, Cr, Sn, and Pb was examined and the results revealed that the crude drugs which are using as a hematics and emmenagogues contained high content of iron, and those which are using as a antiinflammatory and emmenagogues contained high content of copper. Aromatic stomachics contain manganese and zinc, and diuretics and antiinaflammatory agents do tin. High content of Ni was found in tonics, but chronium and cadmium were not detected in crude drugs. There were no differences of content of trace metals in the various site of plants used.