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하호,이희철,Ho Ha,Heecheol Lee 대한화학회 1988 대한화학회지 Vol.32 No.3
$Al(OC_3H_7)_3$ 및 $Si(OC_2H_5)_4$, 알콕사이드를 합성하고 그 물질을 각각 또는 혼합가수분해하여 $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$계의 물질을 얻고 $Al_2O_3-SiO_2$계에 환원제로서 carbon black을 혼합하여 $N_2$분위기에서 환원질화반응시켜 고순도의 ${\beta}-sialon$ 초미분말을 합성하였다. 가수분해 과정에서는 반응조건이 가수분해반응에 미치는 영향을 알아보았고, 환원질화반응 과정에서는 중간생성물을 분석하여 반응경로를 추정하고 ${\beta}-sialon$의 생성반응에 대한 동력학적 고찰을 하였다. Fine powders of amorphous $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$ system were prepared by hydrolysis of solutions containing alkoxides, aluminium tri-isopropoxide and silicon tetra-ethoxide. High purity ultrafine ${\beta}-sialon$ powders were prepared by the carbothermal reduction-nitridation of amorphous $Al_2O_3-SiO_2$ powders mixed with carbon black as a reducing agent. In the hydrolysis step the effect of the factors such as pH, reaction temperature and amount of water on the conversion rate of alkoxides to oxides was investigated. In the carbothermal reduction-nitridation the reaction path was assumed by the analysis of intermediates formed in the process of ${\beta}-sialon$ synthesis and the reaction kinetics of ${\beta}-sialon$ formation was considered.
온도 보상형 FBG 변형률 센서 개발을 위한 EDF 온도 특성 평가
김헌영(Heonyoung Kim),강동훈(Donghoon Kang),이희철(Heecheol Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
FBG sensors containing capability of multiplexing are often used to measure thermal and strain of structures exposed to harsh environments. However, temperature compensation using a thermocouple is required for FBG sensors to measure the strain in condition of temperature changes because the demodulation principle of them is a function of strain and temperature. So, there are rising concerns on FBG strain sensors that do not require additional sensors for temperature compensation. In this paper, as a fundamental study, thermal characteristics of erbium-doped fibers (EDF) are investigated to develop an FBG strain sensor with autonomous temperature compensation. For the test, the change of light absorption ratio is examined when the length of EDF is changed from 1m to 3m and the temperature is changed from RT to 100℃, respectively. From the test results, light absorption ratio of EDF is proportional to both the length of EDF and temperature change. Consequently, on the basis of experimental results, it is confirmed that an FBG strain sensor with autonomous temperature compensation can be developed using the relation between light absorption and temperature change.
심종성 ( Sim Jongsung ),문도영 ( Do-young Moon ),임채옥 ( Lim Chae-ok ),이희철 ( Lee Heecheol ) 한국구조물진단유지관리공학회 2002 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.6 No.2
The use of Basalt fiber can overcome the disadvantages of other fibers(Carbon and Glass fiber) which are mostly used for reinforcing concrete structures, firstly the price of products is lower than others due to the easier process of production, secondly it has higher fire resistance compared to other fibers, thirdly it has also higher resistance of chemical attack and finally it is superior to the resistance of impact. Therefore the Basalt preferentially has to be considered for use where the concrete structures are exposed in high temperature or severe environment by chemical attack, if the requirement of mechanical properties on site are similar. In these points of view the basalt has to be studies in parallel with other new materials. An experimentals study on the bond performance of Basalt fiber is conducted. Pure shear loadings were applied to all specimens. Test variables were Strengthening length, width, number of ply and bonding area.