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TiAl 금속간화합물에서의 응고과정과 제3원소 첨가의 영향
박정종,최진일 단국대학교 신소재기술연구소 1994 신소재 Vol.4 No.-
TiAl 금속간화합물은 기존의 내열재료인 Ni기지 Superalloy에 비해 비강도가 크고 기계적성질이 우수한 데 상온에서의 낮은 인성과 제조시 Ti의 높은 활성으로 인하여 사용이 제한되어 왔다. 본 연구에서는 Plasma arc melting법으로 γ상영역의 조성인 Ti-48 at% Al합금을 제조하여 그 응고과정과 기계적성질을 조사하고 제3원소인 Mn을 첨가했을 때의 조직에 미치는 영향을 조사하여 다음과 같은 결론을 얻었다. 1) Ti-48.1 at% 합금의 응고조직은 층상조직의 결정립계에 γ상이 석출하는 α_2+γ의 2상조직이다. 2) Ti-48.1 at% 합금에 1.22 at% Mn을 첨가하면 주조상태에서 초정 α상 Dendrite 조직이 미세해지며 경도는 감소하는 것으로 나타났다. Ti-48.1 at% Al alloy and Ti-48.3 at% Al-1.22 at% Mn alloy in the composition range of γ phase were casted by using plasma arc melting system. Microstructure, mechanical properties and solidification process of TiAl alloys were investigated. Dendrite structure of primary α phase in alloy added 1.22 at% Mn to Ti-48.1 at% Al was fined and the amount of α_2 phase was decreased.
정종원,박남국,박선정,박종래,김영철 全南大學校 觸媒硏究所 1997 觸媒硏究 論文集 Vol.19 No.-
The effects of polyols, isocyanates. surfactants and water on the physical properties of the polyurethane foam were investigated. The resin used in this study was prepared from a variety of polyol mixtures by adding catalyst, surfactant and cross-linker. The polyurethane was foamed from the resin by adding an equivalent amount of isocyanate and was used in property measurements. The physical properties were more affected by the type of isocyanates and the amount of water than the sound absorption coefficient. The sound absorption coefficient of the polyurethane foam was superior for the polyol mixture of KE-810(40%)FA-733(40%)/FA-703(20%). The sound absorption coefficient was increased with the amount of surfactant L-5309 up to 3000Hz, but was decreased above that frequency.
로디움 첨가량에 따른 Au-Ag 합금의 미세조직과 기계적 성질에 관한 연구
김경남,김광만,노학,박정종 大韓齒科器材學會 2000 대한치과재료학회지 Vol.27 No.3
There are solid solution strengthening, precipitation strengthening, dispersion strengthening, grain size strengthening and strain hardening in strengthening mechanism of alloys. Grain size refiners in dental casting alloys were generally high melting point platinum group metals- Ir(iridium), Ru(ruthenium), Rh(rhodium) etc. But they are shown greater segregation in casting ingot because they have relatively large atomic mass and little additional amount than other alloying elements. In this study, 75wt% Au-25wt% Ag was selected basic composition, and then 0.05wt%, 0.1wt% and 0.3wt% Rh was added to a basic composition as a grain refiner. Analytic specimen were made with diameter 5 mm and length 40mm, and tensile test specimens were prepared with conical shoulders. To evaluate Rh effect, changes of microstructure and X-ray diffraction patterns were observed. Tensile strength and micro-Vickers hardness were also measured. In according to Rh content, percentage of dendrite was decreased and disappeared at 0.3 wt% Rh addition. From the result of x-ray diffraction, second phase was not observed. Each value of yield strength was 46.9±6.1MPa(0.00 wt% Rh), 57.5±4.2MPa(0.05 wt% Rh), 59.8±5.3 MPa(0.1 wt% Rh)and 66.2±6.5 MPa(0.3wt% Rh). From these result, it was shown that yield strength, tensile strength and micro-Vickers hardness were increased with increasing Rh content. In conclusion, addition of Rh to 75wt% Au-25wt% Ag alloy improved microstructure and mechanical properties.
우리나라 一部地域에 있어서의 年齡別 死亡率 및 平均壽命에 關한 硏究
朴亭鍾,高應麟,李星熙 서울대학교 1964 서울대학교 論文集 Vol.15 No.-
A survey was carried out on 37,750 people (5,944 households) during the period from 21 July to the end of the month 1963 for the purpose of grasping the present status of mortality as well as expectation of life in Korea. This study covered the structure of population, age specific average death rate, mortality rate, number dying, number surviving and expectation of life, and the following conclusions were obtained. 1. Structure of population shows pyramid form in general. The proportions of he population under 14 years of age are 49.5% in male and 42.1% in female respectively. 2. Crude death rate is calculated as 11.1 in meal, 10.2 i female and 10.6 in the total. Age specific death rate is shown as table 3. 3. Infant mortality rate shows 68.4 in male and 66.8 in female per 1,000 live births. 4. Mortality curve shows that the higher rate is observed under 1 year of age and drops to the lower point at the age of around 10 years. The mortality goes up slowly again and makes rapid increase after the age of around 50 years. Male shows more higher rate than that of female in general. 5. Number dying is greater during the first year of life and drops to the lowest at the age of around 10 years. Rapid increase of the rate is observed at the age of around 40 years in male and 50 years in female. 6. Higher rate in the number surviving is observed in female than male though whole age group and the time of half surviving is seen during 60 to 70 years of age in both male and female. 7. Expectation of life at the age of 0 shows 57.59 years in male and 60.94 years in female.