고순도 나이오븀과 탄탈륨 희유금속의 물리적 특성평가

김일호,박종범,유신욱,조경원,최국선,서창열,김병규,김준수,Kim Il-Ho,Park Jong-Bum,You Sin-Wook,Cho Kyung-Won,Choi Good-Sun,Suh Chang-Youl,Kim Byoung-Gyu,Kim Joon-Soo 한국재료학회 2005 한국재료학회지 Vol.15 No.4

Thermal, electrical and mechanical properties of high purity niobium and tantalum refractory rare metals were investigated tn evaluate the physical purity. Higher purity niobium and tantalum metals showed lower hardness due to smaller solution hardening effect. Temperature dependence of electrical resistivity showed a typical metallic behavior. Remarkable decrease in electrical resistivity was observed for a high purity specimen at low temperature. However, thermal conductivity increased for a high purity specimen, and abrupt increase in thermal conductivity was observed at very low temperature, indicating typical temperature dependence of thermal conductivity for high purity metals. It can be known that reduction of electron-phonon scattering leads to increase in thermal conductivity of high purity niobium and tantalum metals at low temperature.

기계적합금화로 제조된 Ni-20Cr-20Fe-5Nb 합금에서 PCA로서 H₂O의 역할과 시효석출거동

김일호,권숙인,이원식,채수원,황선근,김명호,Kim Il-Ho,Kwun S.I.,Lee Won-Sik,Chae S.W.,Hwang S.K.,Kim M.H. 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.3

The effect of use of $H_2O$ as PCA(process control agent) to prevent the carbon contamination during mechanical alloying process and the precipitation behavior in Ni-20Cr-20Fe-5Nb bulk alloy after aging were investigated. NbC and $Cr_2O_3$ were formed during mechanical alloying and consolidation processes in the Ni-20Cr-20Fe-5Nb alloy in which methanol($CH_3OH$) was added as PCA. Formation of NbC in this alloy decreased the amount of Nb dissolved in the Ni matrix. The use of $H_2O$ as PCA in Ni-20Cr-20Fe-5Nb alloy prevented the formation of NbC and increased the hardness. The increase of hardness in this alloy was attributed to the increased amount of Nb dissolved in the Ni matrix. After aging treatment for 20 hours at $600^{\circ}C\;and\;720^{\circ}C$ of Ni-20Cr-20Fe-5Nb bulk alloy in which $H_2O$ added as PCA, ${\gamma}"$$(Ni_3Nb,\;tetragonal)\;and\;{\delta}\;(Ni_3Nb,\;orthorhombic)$ precipitates were formed, respectively. The precipitation temperatures of ${\gamma}"$ and ${\delta}$ in this bulk alloy were lower than those in commercial IN 718 alloy. It seemed that the lower precipitation temperatures for ${\gamma}"$ and ${\delta}$ in this bulk alloy than in commercial IN 718 alloy were due to severe plastic deformation during mechanical alloying.

기혼 여성의 직업이 신체적, 정신적 건강에 미치는 영향

김일호,천희란,Kim, Il-Ho,Chun, Hee-Ran 대한예방의학회 2009 예방의학회지 Vol.42 No.5

Objectives : The aim of this study was to investigate whether working married women in different occupational classes affected diverse health outcomes. Methods : We used data for married women aged 25-59 (N=2,273) from the 2005 National Health and Nutritional Examination Survey. Outcome measures included physical/mental and subjective/objective indicators (selfrated poor health, chronic diseases, depression, and suicidal ideation from reported results; metabolic syndrome dyslipidemia from health examination results). Agestandardized prevalence and logistic regression were employed to assess health status according to three types working groups (housewives, married women in manual jobs, married women in non-manual jobs). Sociodemographic factors (age, numbers of children under 7, education, household income) and health behaviors (health examination, sleep, rest, exercise, smoking, drinking) and a psychological factor (stress) were considered as covariates. Results : Non-manual married female workers in Korea showed better health status in all five health outcomes than housewives. The positive health effect for the non-manual group persisted in absolute (age-adjusted prevalence) and relative (odds ratio) measures, but multivariate analyses showed an insignificant association of the non-manual group with dyslipidemia. Manual female workers showed significantly higher age-adjusted prevalence of almost all health outcomes than housewives except chronic disease, but the associations disappeared after further adjustment for covariates regarding sleep, rest, and stress. Conclusions : Our results suggest that examining the health impact of work on married women requires the consideration of occupational class.

'직업을 통한 사회봉사만이 정화의 지름길'

김일호,Kim, Il-Ho 대한건축사협회 1984 建築士 Vol.1984 No.3

MA법으로 제조된 Ni기 합금에서 Y₂O₃ 첨가에 따른 인장강도변화와 시효처리 효과

김일호,이원식,고세현,장진만,권숙인,Kim, Il-Ho,Lee, Won-Sik,Ko, Se-Hyun,Jang, Jin-Man,Kwun, Sook-In 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.1

Ni-20Cr-20Fe-5Nb alloy with or without $Y_2O_3$ was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with $Y_2O_3$ was smaller than that of alloy without $Y_2O_3$ which results from the effect of $Y_2O_3$ suppressing grain growth. The tensile strength at room temperature was increased by the addition of $Y_2O_3$ but decreased abruptly at temperature above $600^{\circ}C$. It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above $600^{\circ}C$ while internal dislocation movement is predominant at below $600^{\circ}C$. After conventional heat treatment process of solution treatment and aging, a small amount of ${\delta}(Ni_3Nb)$ phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of ${\gamma}"(Ni_3Nb)$ was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.

Chalcogenide계 열전재료

김일호,Kim, Il-Ho 한국전기전자재료학회 2011 전기전자재료 Vol.24 No.7

현재 개발 중인 Chalcogenide계 열전재료 중에서, 이방성 재료인 Thallium chalcogenide, Alkalimetal bismuth chalcogenide, Bismuth telluride와 등방성 재료인 Lead telluride, Silver antimony telluride, TAGS, LAST 및 SALT를 소개하였고, 이 재료들에 대한 연구 동향을 살펴보았다. Chalcogenide는 S, Se, Te 및 다른 원소와의 다양한 조합에 의해, 넓은 온도범위에서 열전재료로 응용하기 위한 밴드갭 에너지의 조절이 가능하다. 또한 합성공정에 따른 상변태, 석출 등 구조변화에 따른 열전특성의 변화를 기대할 수 있어 열전재료 개발 초기부터 활발한 연구가 진행되어 왔다. 과거의 전통적인 Chalcogenide계 열전재료뿐만 아니라, Chalcogenide계 열전 신소재에 대해서도 살펴보았다. Chalcogenide는 전자적, 광학적, 열적 성질 등 특성이 독특하고 변화가 무궁무진하여 아주 매력적이기 때문에, 앞으로도 계속 열전재료로서 각광받는 물질군으로 판단된다. 그림 11에 현재까지 ZT의 최댓값이 1이 넘는다고 보고된 열전재료의 성능지수를 요약하였다.

고/액 계면에서의 Peltier 열 측정 및 결정성장에의 응용 II : 측정과 응용

김일호,장경욱,이동희,Kim, Il-Ho,Jang, Kyung-Wook,Lee, Dong-Hi 한국재료학회 1999 한국재료학회지 Vol.9 No.11

$\textrm{Bi}_{2}\textrm{Te}_{3}$의 고/액 계면을 통하여 전류밀도와 방향을 달리 하면서 통전시켰을 때 발생하는 고상, 액상 및 고/액 계면에서의 미소 온도변화를 측정하였다. 이 냉각(가열) 효과는 전류밀도, 통전방향 및 시간에 따라 다르게 나타났으며, 온도변화에 미치는 Peltier 열, Thomson 열 및 Joule 열의 영향을 이론 및 실험에 의해 각각 분류하였다. $\textrm{Bi}_{2}\textrm{Te}_{3}$의 고/액상간의 Peltier 계수는 -1.10$\times\textrm{10}^{-1}$V이었으며, 고상과 액상의 Thomson 계수는 각각 7.31\times\textrm{10}^{-4}V/K와 5.77\times\textrm{10}^{-5}V/K이었다. 직류를 통전하면서 Bi$_2$Te$_3$결정을 성장한 결과, 고상에서 액상으로 통전한 경우, Peltier 냉각에 의한 온도구배의 상승으로 방향성이 향상된 결정을 얻을 수 있었지만, 전류의 방향을 반대로 하면, 결정성 향상에 별 도움을 주지 못하였다. Thermoelectric effects on the temperature changes at the solid- and liquid-phase and its interface were studied by using the unidirectional solidification of $\textrm{Bi}_{2}\textrm{Te}_{3}$. Cooling or heating effects measured with current density. polarity and current passing time were quite different. By separating sole Peltier, Thomson and Joule heat theoretically and experimentally, the Peltier coefficient at the solid/liquid interface of $\textrm{Bi}_{2}\textrm{Te}_{3}$ was -1.10$\times\textrm{10}^{-1}$V, and the Thomson coefficients of solid- and liquid-phase were 7.31\times\textrm{10}^{-4}V/K, 5.77\times\textrm{10}^{-5}V/K, respectively. When D.C. passed from solid-phase to liquid-phase during the crystal growth of $\textrm{Bi}_{2}\textrm{Te}_{3}$ the crystal with more directionality was obtained owing to increase of the temperature gradient in liquid by the Peltier cooling. But in reverse current direction, the crystallinity was not changed significantly.

열전 박막 $Bi_{0.5}Sb_{1.5}Te_3/Bi_2Te_{2.4}Se_{0.6} p/n$ 접합에서의 확산 장벽에 관한 연구

김일호,이동희,Kim, Il-Ho,Lee, Dong-Hui 한국재료학회 1996 한국재료학회지 Vol.6 No.7

In the fabrication processes of thin film thermoelectrics, a subsequent annealing treatment is inevitable to reduce the defects and residual stresses introduced during the film growth, and to make the uniform carrier concentration of the film. However, the diffusion-induced atomic redistribution and the broadening of p/n junction region are expected to affect the thermoelectric properties of thin film modules. The present study intends to investigate the diffusion at the p/n junctions of thermoelectric thin films and to relate it to the property changes. The film junctions of p-type(Bi0.5Sb1.5Te3)and n-type(Bi2Te2.4Se0.6)were prepared by the flash evaporation method. Aluminum thin layer was employed as a diffusion barrier between p-and n-type films of the junction. This was found to be an effective barrier by showing a negligible diffusion into both type films. After annealing treatment, the thermoelectric properties of p/n couples with aluminum barrier layer were accordingly retained their properties without any deterioration.

P형 Bi_0.5Sb_1.5Te₃ 박막의 열전 특성에 미치는 두께 및 어닐링 효과

김일호,장경욱,Kim Il-Ho,Jang Kyug-Wook 한국재료학회 2004 한국재료학회지 Vol.14 No.1

P-type $Bi_{0.5}$$Sb_{1.5}$ $Te_3$ thin films were deposited by the flash evaporation technique, and their thermoelectric properties and electronic transport parameters were investigated. The effective mean free path model was adopted to examine the thickness effect on the thermoelectric properties. Annealing effects on the carrier concentration and mobility were also studied, and their variations were analyzed in conjunction with the antisite defects. Seebeck coefficient and electrical resistivity versus inverse thickness showed a linear relationship, and the effective mean free path was found to be 3150$\AA$. No phase transformation and composition change were observed after annealing treatment, but carrier mobility increased due to grain growth. Carrier concentration decreased considerably due to reduction of the antisite defects, so that electrical conductivity decreased and Seebeck coefficient increased. When annealed at 473 K for 1 hr, Seebeck coefficient and electrical conductivity were $160\mu$V/K and 610 $W^{-1}$ $cm^{ -1}$, respectively. Therefore, the thermoelectric quality factor were also enhanced to be $16\mu$W/cm $K^2$.>.

차세대 열전소재-Skutterudite

김일호,어순철,Kim, Il-Ho,Eo, Sun-Cheol 한국전기전자재료학회 2007 전기전자재료 Vol.20 No.1