AlSiCa($Al_2O_3-SiC-C$)계 내화물 재료에 관한 연구: (I) 국산 chamotte로부터 원료분말합성

심광보,주경,오근호,Shim, Kwang-Bo,Joo, Kyoung,Auh, Keun-Ho 한국결정성장학회 1997 韓國結晶成長學會誌 Vol.7 No.4

AlSiCa powders were prepared from the domestic Hadong Kaolin ($Al_2O_3{\cdot}2SiO_2{\cdot}2H_2O$). As a result of the reaction of Hadong Kaolin and carbon powder at reducing atmosphere, $Al_2O_3{\cdot}SiC$ composite started to form at $1300^{\circ}C$ and completed at $1400^{\circ}C$. The optimum amount of carbon was 1:4 in mole ratio. It was found that only bright-green $\beta-SiC$ phase forms when the mixture was packed without carbon powder in alumina crucible. 하동고령토($Al_2O_3-SiC-C$)를 출발원료로하여 AlSiCa내화재 원료를 합성하였다. 하동고령토와 탄소분말을 혼합하여 수소분위기하에서 반응시킨결과, $1300^{\circ}C$에서$Al_2O_3-SiC-C$ 복합체가 힙성되기 시작하여$1400^{\circ}C$에서 완전 합성되었고, $SiO_2$에 대한 최적carbon량은 mole비로 1:4이었다. 합성시 알루미나 용기에 탄소분말을 충전시키지 않을 때는 미합성부분이 없이 밝은 녹색을 띈 $\beta$-SiC(cubic form) 를 형성함을 확인하였다.

$CaF_{2}$ 결정의 annealing시 내부 bubbles의 거동

심광보,박대출,주경,오근호,Shim, Kwang-Bo,Park, Dai-Chul,Joo, Kyoung,Auh, Keun-Ho 한국결정성장학회 1996 韓國結晶成長學會誌 Vol.6 No.4

결정입계를 갖는 $CaF_{2}$ 결정을 annealing할 때, 내부에 존재하는 bubbles의 거동을 결정학적으로 분석하였다. 이들 bubbles는 결정 내에서 일어나는 slip 현상처럼 $CaF_{2}$ 결정구조에 의존하여 특정한 방향으로 배향되어 있음이 확인되었다. 또한, AFM(atomic force microscope)으로 분석한 결과, 이들의 움직임은 negative grain growth에 의한 S-surface를 형성하고 있음이 관찰되었다. The behaviour of the internal bubbles present in $CaF_{2}$ crystals was characterized crystallographically using a variety of the mircroscopical technique. The bubble defects were found to be aligned on the characteristic planes and directions depending on the crystals structure of the $CaF_{2}$. The AFM analysis revealed that these behaviors are related to the S-surface formation by the negative grain growth mechanism.

$AlSiCa(Al_2O_3-SiC-C)$계 내화물 재료에 관한 연구:(II) 합성원료의 산화 및 소결 특성

심광보,주경,오근호,Shim, Kwang-Bo,Joo, Kyoung,Auh, Keun-Ho 한국결정성장학회 1997 韓國結晶成長學會誌 Vol.7 No.3

국산 하동고령토로부터 AlSiCa의 주원료인 $Al_2O_3$-SiC계 내화물 원료를 합성하는 데는 성공하였으며, 합성된 $Al_2O_3$-Sic 합성분말의 산화반응을 검토하였다. 공기중에서 산소와 반응시켜 Sic가 $SiO_2$로 산화될 때 필요한 활성화 에너지는 $\Delta$G=74.86 KJ/mol 이었으며, 수소분위기에서 $1500^{\circ}C$ 및 $1600^{\circ}C$에서 상압소성한 결과 vaporization 현상때문에 소결특성이 좋지 않았다. whisker-SiC상태로 합성되는 이 복합체는 AlSiCa의 고온내화벽돌이외의 고온구조용 재료로 응용될 수도 있다. It was succeeded in synthesizing the $Al_2O_3$-SiC refractory powders, which is main raw material of AlSiCa, from the domestic Hadong Kaolin. The oxidation reaction of the synthesized $Al_2O_3$-SiC powder was examined. The activation energy for SiC in $Al_2O_3$-SiC powder was calculated to be $\Delta$G=74.86 KJ/mol in air, however the poor sinterability of the powders is thought to be due to the vaporization of SiC in $H_2$ atmosphere. The formation of the whisker-SiC gives the possibility in use for high temperature structural material over high temperature refractory brick.

특수학급 교사의 직무스트레스가 이직 의도에 미치는 영향

심광보 ( Gwang Bo Shim ) 한국초등특수교육학회 2012 초등특수교육연구 Vol.14 No.1

이 연구는 최근 특수학급이 특수교육의 현장으로서 점점 그 비중이 커져가고 있는 추세에 따라, 특수학교와는 다른 환경인 특수학급에 근무하는 특수교사의 직무스트레스와 이직 의도 특성을 확인하고, 직무스트레스가 어떻게 이직 의도에 영향을 미치는지 영향관계를 밝히고자 하였다. 이러한 연구 목적을 달성하기 위하여 대구광역시 소재의 특수학급교사 147명을 대상으로 설문조사를 실시하였다. 연구의 결론을 요약하면, 특수학급 교사의 특수학교 경험, 이직 경험, 희망근무지와의 불일치, 동료교사의 유무, 특수교육보조원 유무 등을 포함한 여러 요인의 차이들이 직무스트레스 및 이직 의도와 관련이 있는 것으로 확인되었으며, 또 행정관리자와의 관계, 신체적 증상 등 다양한 직무스트레스 요인들이 이직의도에 영향을 주고 있는 것으로 나타났다. The purpose of this study is to analyze properties of special class teachers` job stress and turnover intention and examine effects of job stress on turnover intention. For this purpose, a survey was conducted by mail with 200 special class teachers from primary and secondary schools in Daegu; of those questionnaires returned, 147 copies were analyzed. Statistical techniques used to analyze the collected data were t-test, one-way ANOVA, and regression analysis. Based on the results and discussion, the following conclusions were drawn. First, the level of general job stress for special class teachers was not high; teachers with shorter teaching career, less experience in special schools, experience in turnover, a larger number of students, discordance between the present working area and expected one, and presence of special education assistants and other special education teachers come to experience higher job stress. Second, the level of special class teachers` turnover intention was not high; teachers with short teaching career, discordance between the present working area and expected one, and absence of special education assistants showed greater turnover intent; male teachers, rather than female ones, with shorter teaching career and discordance between the present working area and expected one more frequently conducted actual turnover trial. Those with longer teaching career, experience in turnover, a hope to be placed in a special class, and presence of other special education teachers within a school showed stronger stay intent. Third, of job stress factors for special class teachers, the higher the degree of physical symptoms and the higher stress caused by relationships with administrative managers, the greater turnover intention. And the higher job stress caused by psychological and emotional symptoms, teachers` mutual relationships, and relations with parents, the higher level of actual turnover trial. The lower job stress caused by relations with administrative managers and internal conflicts, the lower turnover intent. However, job stress from students` behavior or time management causes no difference in turnover intention.

유한요소법을 이용한 박판 맞대기 용접부 잔류응력 및 균열 해석

심광보(Kwang-Bo Shim),배홍열(Hong-Yeol Bae),전준영(Jun-Young Jeon),송태광(Tae-Kwang Song),김윤재(Yun-Jae Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.5

본 논문은 박판 맞대기 용접부 잔류응력을 3 차원 유한 요소법을 이용해서 모사하였다. 경계조건이 잔류응력에 미치는 영향을 연구하기 위해 다양한 경계조건이 고려되었으며, 예측된 용접 잔류응력은 기존 문헌의 내용과 비교 검증하였으며, 본 연구의 결과는 박판 용접부 균열에 발생하는 잔류응력의 영향을 해석하는데 사용될 것이다. In this study, we calculate the welding residual stresses for a butt-welded thin-walled plate by carrying out threedimensional finite-element analyses. To study the effect of mechanical boundary conditions on the welding residual stresses, various boundary conditions are considered. The welding residual stresses obtained in the measurements and finite-element analyses are validated by comparing them with the welding residual stress profiles in the R6 code. The results of this study are used to analyze the influence of residual stress on the crack formation in thin-section weldments.

PCB 커넥터의 무납땜 결선을 위한 PRESS-FIT 성형 연구

심광보(Kwangbo Shim),유우식(Woosik Yoo) (사)한국CDE학회 2021 한국CDE학회 논문집 Vol.26 No.3

Recently, regulations on lead used in automobiles and electronics have been tightened. In particular, in the case of the existing PCB connector terminals, the use of lead is high, so the demand for the development of solderless PCB connector terminals to replace them is increasing. This paper describes the research on the development of the PCB connector terminal of the solderless connection method through the development of the Press Fit EoN shape terminal. In order to analyze the difference according to the press fit EoN product shape, the test sample was taken out by making two different types of progressive molds using the EoN outer corner “R” molding method of the press fit that has the greatest effect on the insertion force. Insertion and release tests were performed on the PTH with the extracted sample, and the required force was measured and compared. The press-fit EoN terminal developed in this study was applied to the soul power window switch of “Company K” and is being used as an eco-friendly PCB connector terminal.

유한요소법을 이용한 박판 맞대기 용접부 잔류응력 해석

심광보(Kwang-Bo Shim),배홍열(Hong-Yeol Bae),전준영(Jun-Young Jeon),송태광(Tae-Kwang Song),김윤재(Yun-Jae Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

In this paper, welding residual stresses for butt weld of thin-walled plate are calculated based on 3-dimensional finite element analyses. To study the effect of mechanical boundary condition on welding residual stresses, various boundary conditions are considered. Predicted welding residual stresses are validated existing results of measurements and finite element analyses and compared with welding residual stress profile in the R6 code. The results of this work are expected to be used in assessment of the crack in weldment.

$SrTiO_{3}$ 원료봉의 미세구조가 용융대 안정에 미치는 영향

조현,심광보,오근호,Cho, Hyun,Shim, Kwang-Bo,Auh, Keun-Ho 한국결정성장학회 1996 韓國結晶成長學會誌 Vol.6 No.2

Floating zone법에 의한 $SrTiO_{3}$ 단결정 성장에 있어서 원료봉의 미세구조가 원료봉과 융액간의 고액계면의 형상 및 용융대의 안정성에 미치는 영향을 광학현미경 및 전자현미경을 이용하여 조사하였다. $1400,\;1500,\;1600^{\circ}C$로 소결온도를 변화시키면서 소결한 $SrTiO_{3}$ 및 $Fe_{2}O_{3}$를 0.2 wt% 첨가한 $SrTiO_{3}$ 원료봉을 실험시편으로 사용하였다. 저온($1400^{\circ}C$)에서 소결한 경우는 치밀화가 덜 진행되어 존재하는 기공들이 균일한 용융대 형성을 저해하였고, 고온($1600^{\circ}C$)의 경우는 미세구조는 치밀하나 이상입자성장 현상으로 안정된 용융대 형성에 어려움을 주었음을 실험적으로 확인하였다. 따라서 이상입자성장을 하지 않은 즉, 균일한 결정입 크기 분포를 갖는 원료봉을 사용하여 결정성장을 하였을때 원료봉의 균일한 용융양상을 유도할 수 있었고 안정한 용융대 유지가 가능하여 결정성장에 가장 적합함을 알게 되었다. Microscopic analysis has been performed in order to investigate effects of the microstructure of the starting feed rods on the morphology of the S-L interface and the stability of the molten zone during single crystal growth of $SrTiO_{3}$ using a floating zone method. Undoped and $Fe_{2}O_{3}$ doped $SrTiO_{3}$ doped $SrTiO_{3}$ specimens, sintered at the different temperatures have been used. In the case of the feed rods sintered at the lower temperature($1400^{\circ}C$), the poor densification made the stability of the molten zone difficult to maintain. The feed rods sintered at the higher temperature ($1600^{\circ}C$) exhibited the higher density but their molten zone was difficult to maintain due to the presence of the abnormally grown grains. It is concluded that the uniform grain size distribution of the feed rod is the critical factor to maintain the stable molten zone and therefore to give optimum growth condition during FZ single crystal growth.

Floating zone법에 의한 $LiNbO_3$ 단결정 성장을 위한 최적 원료분말 합성 및 소결 조건

조현,심광보,오근호,Cho, Hyun,Shim, Kwang-Bo,Auh, Keun-Ho 한국결정성장학회 1996 韓國結晶成長學會誌 Vol.6 No.2

Floating zone법으로 $LiNbO_3$ 단결정올 육성하는데 있어서 원료분말 합성과 원료봉 소결 과정의 최척의 조건을 설험적으로 조사하였다. 원료분말 합성사 낮은 고상반응 온도(700, $800^{\circ}C$)에서는 미량의 $Li_2CO_3$와 $Nb_2O_5$가 미반응상태로 남아있고, 고상반응 온도가 높을 때 ($1000^{\circ}C$)에는 입자성장이 일어나 후속공정인 원료봉 소결에 악영향을 미침이 확인되었다. $950^{\circ}C$에서 12시간 고상반응시킨 원료분말이 $LiNbO_3$의 결정상을 가지면서 미세한 결정립 크기와 균일한 크기분포를 보여 $950^{\circ}C$, 12시간이 최적의 원료분말 합성조건이었다. 원료봉 소결시 소 결온도가 높아질수록, 또 소결시간이 늘어날수록 치밀도가 증가하고 업자성장 양상이 급격히 증가함을 알 수 었었다. $1100^{\circ}C$에서 2시간 동안 소결한 원료봉이 치밀하고, 작은 결정립 크기 와 균얼한 크기분포를 나타내어 floating zone법에 의한 $LiNbO_3$ 단결정성장에 가장 적합한 최적 의 소결 조건은 $1100^{\circ}C$, 2시간엄이 확인되었다. The optimum conditons were experimentally established for the powder synthesis and sintering of the feed-rods for $LiNbO_3$ crystal growth by a floating zone method. At the lower synthesis temperatures(700, $ 800^{\circ}C$) the minor amounts of $Li_2CO_3$ and $Nb_2O_5$ were present in the synthesized $LiNbO_3$ powder and at the higher temperature the particle size increased which is not favorable for the sintering process for the feed-rods. $LiNbO_3$ powder synthesized at $950^{\circ}C$ for 12 hours was found to be the best because it contains only the$LiNbO_3$ phase with the small particle size and uniform particle size distribution. As the sintering temperature and the soaking time increase, the sintered feed-rods exhibited the higher sintered density and grain growth phenomena. The $LiNbO_3$ feed rods sintering at $1100^{\circ}C$ for 2 hours were found to have the best microstructure for the precursor feed-rods of the floating zone crystal growth because of their higher density, small grain size and uniform particle size distribution. As the sintering temperature and the soaking time increase, the sintered feed-rods exhibited the higher sintered density and grain growth phenomena. The $LiNbO_3$ feed rods sintering at $1100^{\circ}C$ for 2 hours were found to have the best microstructure for the precursor feed-rods of the floating zone crystal growth because of their density, small grain size and uniform grain size distribution.

알루미늄이 첨가된 Li(Ni_1/3Co_1/3Mn_1/3-xAl_x)O₂ 양극활물질의 전기화학적 특성

김선혜,심광보,김창삼,Kim Seon-Hye,Shim Kwang-Bo,Kim Chang-Sam 한국전기화학회 2006 한국전기화학회지 Vol.9 No.2

초음파분무열분해법과 한 단계의 후열처리로 이차상이 없는 Al이 첨가된 $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01. 0.05) 리튬이차전지용 양극활물질을 합성하였다. 합성된 분말은 Al의 첨가량이 많아짐에 따라서 $I_{003}/I_{104}$ 비는 감소하고 입자가 커지는 경향을 보였다. 상온에서 전류밀도 1C의 rate로 $3.0\sim4.5V$ 범위에서 충방전 시험한 결과, Al 치환량이 0.5와 1.0 at%에서는 초기용량이 180과 $184mAhg^{-1}$으로 치환하지 않았을 때의 $182mAhg^{-1}$과 차이가 없었으며, 싸이클 특성도 치환하지 않은 것과 0.5, 1.0 at% 치환한 조성에서 각각 81, 77, 81%의 방전용량이 유지되었다. 그러나 $3.0\sim4.6V$에서는 치환효과가 확실하게 나타나서, 50 싸이클 후의 치환하지 않은 것의 방전용량은 초기용량의 30%가지 감소한데 비하여 Al을 0.5 at% 치환한 것은 70%를 유지하였다. 치환에 의한 싸이클 특성 향상은 XPS 분석 결과 Al 치환이 $Mn^{3+}$의 양을 감소시켰기 때문인 것으로 사료되었다. Cathode materials of Al-doped $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single-step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of $I_{003}\;to\;I_{104}$, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and $184mAhg^{-1}$ in a voltage range of $3.0\sim4.5V$ at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of $3.0\sim4.6V$, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to $Mn^{3+}$ ion decrease as the Al doping from the XPS analysis results.