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Vacuum Hot Pressing 조건이 $SiC_w$/2124AI 금속복합재료의 기계적 성질 및 미세구조에 미치는 영향
홍순형 한국분말야금학회 1994 한국분말재료학회지 (KPMI) Vol.1 No.2
The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.
Fe-10Cr-10Ni-2 W 마르에이징강에서 reverted 오스테나이트의 형태와 결정학적 특징
홍순형,남수우,석진이 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.3
The morphology and crystallographic feature of austenite formed from martensite during aging have been investigated in a Fe-10Cr-10Ni-2W maraging steel. The microstructure of solution-treated sample is fully martensite before aging. Four types morphology, such as lath-like, allotriomorph, Widmansta¨tten and wedge-shaped austenite. appeared in this maraging steel during aging. The reverted austenite is formed having both a Kurdjumov-Sachs(K-S) orientation relationship and a Nishiyama(N) orientation relationship with martensitic matrix. Furthermore, a wedge-shaped austenite is found to have a twin relationship between adjacent austenites. The twinned austenite is observed to have a very sharpy twin boundary, and longitudinal direction of the twin boundary is dependent upon both the beam direction and the orientation relationships between austenite and martensite.
경남지역 중학교 과학교사의 환경교육에 대한 의식조사 : Centered on the Kyungnam area
홍순형,최병태,박원혁,조운복 부산대학교 사범대학 과학교육연구소 1994 科學敎育硏究報 Vol.21 No.-
A questionnaire was administered to investigate science teacher's knowledge and the attitude toward the environmental education in the junior high school. 384 science teachers were selected from public and private junior high schools in Kyungnam area. The results obtained were as follows; 1. Most of science teachers(99.4%) were interested in environmental education, but 24.74% of them were educated regarding environmental education through teacher's discipline(41.11%) and university classes(33.68%). Respondents indicated that the knowledge of environmental education was useful when they took classes. Also, 95.83% of science teachers preferred more classes about environmental education. The most of science teachers(65.36%) felt that the environment problem on the region of their residence is very serious for humans such as water pollution(79.17%), air pollution(57.29%), and garbage pollution(57.03%). About science teacher's knowledge regarding environmental education, they were aware of only 11.94% in 30 questions. 2. The results indicated that most of science teachers(99.74%) expected the necessity of systematic environmental education in junior high school curriculum. The respondents indicated that all education system(58.35%); all teachers take charge of environmental education(59.00%), and 96.09% of the science teachers expected appropriate modification of contents regarding environmental education in current science book. 42.45% of the science teachers mentioned the environmental education should be taught as a separated subject in schools. As, 94,79% of the science teachers indicated that environmental education needs also to be implemented into the university curriculum. 3. The results of this study indicated that science teachers want to emphasize water pollution, air pollution, soil pollution in the junior(4.65, 4.51 and 4.36 points each) and senior(4.34, 4.32 and 4.23 points each) high school curriculum. Also, respondents felt that documentary(4.37 points), movie(4.13 points) and guide books(3.96 points) are important for environmental education reference. 4. The results of this study indicated that 81.77% of science teachers have teaching experience about environmental education and only 1.56% of them believed that students are well informed regarding environmental education subjects. As, 87.76% of science teachers believed that entrance examinations for senior level schools affects environmental education. Also, 44.79% of science teachers only taught environmental education in related classes. Most of respondents appeared not to teach environmental education due to fact they do not have time and reference. By way of solution to difficult problems, newspaper and journal(37.24%), and technical environmental education books(29.69%) were helpful. Respondents want the support of related journals, books, and references(41.15%). Also, almost science teachers(99.22%) believed that current contents of environmental education references are not enough to modify the attitude and the behavior of student. 5. Almost, half of science teachers did not know about environmental education policy of Korea(30.21%) and other countries(47.66%), and environment policy(37.51%). But 74.74% of science teachers tried to teach students to modify the attitudes and the behaviors of student regarding environmental education, and believed role has a strong effect on students. According to this study, problems about the environment issue in Korea are immoral business practices(4.48 points), the people's awareness(4.44 points), environment policy(4.20 points), and education(4.00 points). 6. Judging from above results, although science teachers have a deep interesting in environmental education, environmental education was not enough for changing the student's attitude due to the lack of time and materials. The science teachers themselves were in short of knowledge and experience about environmental education, so they should be educated through a systematic teachers' discipline.