Effect of post annealing on the microstructure, mechanical properties, and failure of Mo_xW_1-xSi₂ heaters produced by self-propagating high-temperature synthesis

Cho, Myung-Yeon,Lee, Sung-Chul,Park, Chulhwan,Lee, Daeseok,Koo, Sang-Mo,Moon, Kyoung-Sook,Lee, Dong-Won,Oh, Jong-Min Elsevier 2019 INTERMETALLICS Vol.110 No.-

<P><B>Abstract</B></P> <P>High-performance tungsten molybdenum disilicide (Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB>) heating elements were prepared using a self-propagating high temperature synthesis process. The effect of post annealing on the degradation behavior of the alloy was experimentally investigated. Increasing the attrition milling time up to 20 min during powder preparation resulted in Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters with the highest density, which increased the fracture strength compared to samples with shorter attrition times. Such samples were annealed and evaluated as heating elements using accelerated degradation tests and failure analysis in order to compare their structural characteristics and flexural strength with as-fabricated samples. The annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heater showed a relatively dense structure with few pores and no secondary phases, apart from a SiO<SUB>2</SUB> layer. This favorable structure prevented bubble formation, which can result in fracturing of the heater, as revealed by evaluation at high temperatures with various heating rates. The flexural strength of the annealed specimen was 2.5-times higher than that of the as-fabricated specimen, which was attributed to removal of secondary phases during annealing. Failure time and surface load analyses were used to investigate the fracture mechanism of the Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters in detail at 1790 °C by quantifying bubble formation and the presence of secondary phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Self-propagating high temperature synthesis of Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters demonstrated. </LI> <LI> Post-annealed Mo<SUB>x</SUB>W<SUB>1-x</SUB>Si<SUB>2</SUB> heaters were highly dense, with good flexural strength. </LI> <LI> Bubble formation (the main cause of fracture) suppressed at ultra-high temperature (above 1700 °C). </LI> <LI> Surface load, failure time, and bubble formation used to study fracture mechanisms. </LI> </UL> </P>

삼상 순환유동층의 상승관에서 연속 액상의 축방향 혼합특성

유명선,손성모,강석환,강용,김상돈 한국공업화학회 2004 공업화학 Vol.15 No.1

직경이 0.102 m이고 높이가 3.5 m인 기체-액체-고체 순환 유동층의 상승관에서 액상의 축방향 혼합특성을 고찰하였다. 기체유속(0.01~0.07 ㎧), 액체유속(0.25~0.31 ㎧) 그리고 고체순환속도(2~8 ㎏/㎡s)를 실험변수로 선정하였으며 이들 변수들이 액상의 축방향 분산계수에 미치는 영향을 고찰하였다. 축방향의 추적자 농도분포로부터 분산모델을 사용하여 액상의 축방향 분산계수를 구하였다. 액상의 축방향 분산계수는 기체유속과 고체순환속도가 증가함에 따라서 증가하였으나 액체의 유속의 증가에 따라서는 약간 감소하였다. 또한, 액상의 축방향 분산계수는 등방성 난류 모델을 적용한 무차원군으로 표현되는 상관식으로 나타낼 수 있었다. Characteristics of liquid dispersion in the axial direction were investigated in the riser of a three-phase circulating fluidized bed whose diameter is 0.102 m and 3.5 m in height. Effects of gas (0.01-0.07 m/sl and liquid (0.25-0.31./s) velocities and the circulation rate of solids (2∼8 kg/m^(2)s) on the dispersion coefficient of the continuous liquid phase in the axial direction were determined. A dispersion model was employed to obtain the axial dispersion coefficient of the liquid phase from the radial concentration profiles of tracer with variations of axial position. The axial dispersion coefficient of the liquid phase increased with increasing gas velocity or solid circulation rate, however, decreased slightly with increasing liquid velocity in the riser bed. The axial dispersion coefficient of the liquid phase was well correlated in terms of dimensionless groups based on the isotropic turbulence theory.

A2024와 SM45C 마찰용접의 열전달 해석

이상윤,고준빈,명태식,김기길,강형모 大田産業大學校 2001 한밭대학교 논문집 Vol.18 No.-

The heat transfer mechanism initiating the friction welding is examined and a transient three dimensional heat conduction model for the welding of two dissimilar cylindrical metal bars is investigated. The cylindrical metal bars are made of materials made of A2024 and SM45C. Numerical simulations of heat flow are performed using the finite volume method. Respectively, Commercial FLUENT code is used in the heat flow simulation and maximum temperature and distribution of temperature are calculated. Temperature of friction welded joining face is compared with the temperature distribution measured by experiment and numerical simulation. The maximum temperature of friction welded joining face is lower than melting point of A2024-T6 aluminum alloy using insert metal. The temperature distribution of friction welded joining face with insert metal is more uniform than that of without insert metal

객체지향형 실시간 EMS 데이터베이스 구축을 위한 개념디자인

최상열,김종형,신명철,김응모,김학만 성균관대학교 1997 학술회의지원논문목록집 Vol.1997 No.-

Currently, EMS(Energy Mangement System) database is implemented by relational concept but, It is hard to describe the characteristic of power system data which require real time management and composite type. This paper present the way how to design conceptual schema for EMS database using ovject-oriented concept which is free to decribe composite data type and support inheritance concept.

선박수리업무에 종사하는 군무원들의 작업환경에 대한 인식이 직업만족도에 미치는 영향

오경재,모영하,윤한,김명선,이정미,권근상 한국산업위생학회 2003 한국산업보건학회지 Vol.13 No.1

This study was carried out to evaluate the relations among working environments, health behaviors and satisfaction with their duty in a group of 200 ship-repair workers in the ROK navy. The results were as following; Age of workers was 40 years and over(83%) and working duration was 10 years and over (71.5%). Most of them were married and had studied beyond high school. The 69.5% of workers satisfied with their job, whereas. about 59.5% of workers had satisfaction with their working condition. There were current drinkers, 78.5%, current exercising workers, 43.5%, obese workers, 28.0%, and salted food intakers, 18.5% in the workers. The major harmful environmental factors in the ship-repair workplace are noise, vibration, dust and chemicals. Most of workers are exposed to above harmful factors and complained about exposure of noise and dust. The consumption of cigarette or alcohol in people who exposed to noise was much higher than in people who did not, but the difference was not statistically significant. Prevalence of obesity and hypertension were not significantly different between the exposure with noise and dust. Noise or dust exposure was significant relation to satisfaction with their duty and working condition. The affective factors for satisfaction with their duty were people who worked for 10 years or more(OR= 4.53), exercisers(OR=4.78) and dust(OR=3.05) in Logistic regression analysis.

Purge & Trap-GC를 이용한 의약품 필름코팅 정제 중 잔류용제에 관한 연구

장준식,이명자,소유섭,문춘선,이주헌,박희라,김진숙,강경모,이선옥,방성연,유미자,유문균,금오성,이병욱 식품의약품안전청 2000 식품의약품안전청 연보 Vol.4 No.-

의약품은 약물을 생체에 적풋하기 위하여 유효성분의 효과가 언제나 일정하게 확보되고 사응에 편리하도록 만들어지는 것이므로 유효썽분 이외에 약효에 영향을 주지 않는 성분이 첨가되는 경운가 많다. 이 때 사용되는 용매들은 제피의 광택 및 건쪼시간의 단축 등을 위하여 휘발점이 낮을 용매들이 주로 사용되어진다. 본 연구는 의약품 필름코팅정제 중 잔류용매 4종(chlorofonr benzen, trichloro ethylen, 1,4-dioxane)에 대한 변형된 pirge & trap-GC 장치를 이용한 동시분석방법을 개발하였으며, 각 표준품의 RSD 값은 chloroform 3.03%, benzen 3.17%, trichloroethylen 3.69% and 1,4-dioxane 3.41%였다. 또한 시중 유통중인 의약품 50종에 대하여 잔류웅매 양을 측정하였으며, 검출되는 잔류용매는 한 건도 없었다. This study nras carried out to develope the analytical method for the mixture of chlorefonn, benzen, trichloroethylen and 1,4-dioxane simultaneously and determine the remainingorgauic solvents in coating tablets by Purge & Trap-GC. The results were as follouFs ; 1. Chloroform, benzen, trio:tloroethylen and 1,4-dioxane separated by tenax #5 trap by HP-624GC column by terrlperature programming. The peaks were separated completely at retentiontime of 6.88min for chloroform, 8.21min for benzen, 10.38miu for trichloroethylen and 11.95minfor 1,4-dioxane. 2. Standard RSD were individually chloroform 3.03%, benzen 3.17%, trichloroethylen 3.69%and 1,4-diorane 3.41%. 3. 60 samples were not detrcted chloroform, benzen, trichloroethylen and 1,4-dioxane.

만성 승모판 패쇄부전증 환자에서의 안지오텐신 전환효소 억제제의 장기 투여 효과

김대희,이명묵,이해영,조현재,박승정,서재빈,서정원,양한모,윤창환,조상호,이준희,김용진,김명아,손대원,오병희,박영배 대한순환기학회 2004 Korean Circulation Journal Vol.34 No.2

위장질환과 Helocobacter pylori와의 상관관계

정동진,이정화,이상오,김재명,최태균 한국건강관리협회 1999 건협 Report Vol.2 No.-

Preparation of LiGaO₂ Thin Films by Chemical Vapor Deposition

Sung, Myung Mo 국민대학교 2002 기초과학연구소 논문집 Vol.21 No.-

LiGaO₂ films have been grown on Si (100) substrates using a new single precursor, [Li(OCH₂CH₂OCH₃)₂Ga(CH₃)₂]₂ under high vacuum conditions (5 × 10^(-6) Torr). The [Li(OCH₂CH₂OCH₃)₂Ga(CH₃)₂]₂ was synthesized and characterized using spectroscopic methods and single-crystal X-ray diffraction analysis. The chemical composition, crystalline structure, and morphology of the deposited films were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results show that polycrystalline LiGaO₂ films preferentially oriented in the [010] direction can be deposited on Si (100) at 500-550℃ by MOCVD. The single precursor [Li(OCH₂CH₂OCH₃)₂Ga(CH₃)₂]₂ has been found suitable for chemical vapor deposition of LiGaO₂ thin films on Si substrates.

The Radioprotective Effects of Bu-Zhong-Yi-Qi-Tang as a Prescriptions of Traditional Chinese Medicine in Irradiated Mice

( Sung Mo Kim ),( Se Ra Kim ),( Heon Oh ),( Jung Ah Yang ),( Sung Kee Jo ),( Myung Woo Byun ),( Sung Tae Yee ) 한국수의병리학회 2000 학술대회 Vol.2000 No.-

We perfornlecl this stucly to determine the effect of BLI-Zhong-Yi-Qi-Tang, as a prescription of traditional Oriental medicine, and its major ingreclients 011 jejunal crypt s~u-vival, enclogenous spleen colony formation, and apoptosis in jejunal crypt cells of mice irracliatecl with high ancl low close of 7 -racliation. Bu-Zhong-Yi-Qi-Tang aclinii~istration before irradiation protected the jejunal crypts (p<0.0001), increased the formation of endogenous spleen colony (p<0.05) and reduced the frecluency of radiation-ind~~cecal poptosis (p<0.05). In the experiment on the effect of ingreclients of Bu-Zhong-Yi-Qi-Tang, the result indicated that the extract of Rensan (Panax ginseng), Danggui (Radix Angelicae sinensis), Shengma (Rhizoma Cimicifugae) ancl Chaihu (Raclix Bupleuri) might have a major radioprotective effect. Although the mechanisms of this inhihitory effect remain to he elucidated, these results inclicatecl that Bu-Zhong-Yi-Qi-Tang might be a useful radioprotector, especially since it is a relatively nontoxic natural product. Further studies are needed to characterize better the protective nature of Bu-Zhong-Yi-Qi-Tang extract ancl its ingreclients.