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정의창,신상엽,김영수 대한건축학회지회연합회 2007 대한건축학회연합논문집 Vol.9 No.4
The purpose of this study is to investigate the effect of different levels of cement replacement(0, 5, 10, 15, 20, 25%) by copper slag on the expansion of mortar bars containing reactive aggregates. The experimental program included expansion measurement of the mortar bar specimens, also the determination of the morphology and composition of the alkali-silica reaction products by using scanning electron microscopy(SEM), energy dispersive x-ray(EDX), and x-ray fluorescence spectrometer(XRF). The results of the experimentation are as follow. 1) From the result, the expansion levels of mortar-bars containing CoS reduced as replacement levels increased. and the 25% replacement of CoS produced the least expansion. 2) The amount of A.E.W decreased with an increasing amount of CoS replacement, which indicated that the amount of alkali-silica reaction products decreased an increasing amount of CoS replacement. 3) After the accelerated test, SEM and BEM analysis showed the presence of alkali-silica gel and rim around the aggregate and cement paste, however the reaction products decreased markedly as the level of replacement was increased. 4) The presence of CoS changed significantly the alkali-silica gel composition, highlighting the strong relationship between the gel composition and expansion rate. Containing CoS, the higher replacement level, the higher CaO/SiO2, CaO/(Na2O)e, and EBIV ratio in the alkali-silica gel, the lower the gel's capacity for expansion.
전자총 시스템 제작과 이를 이용한 고융점 금속 증발에 관한 연구
정의창,노시표,김철중 한국진공학회 2003 Applied Science and Convergence Technology Vol.12 No.1
An axial electron beam gun system, which emits the electron beam power of 50 kW, has been manufactured. The electron beam gun consists of two parts. One is the electron beam generation part. including the filament, cathode, and anode. The maximum beam current is 2 A and the acceleration voltage is 25 kV. The other part includes the focusing-, deflection-, and scanning coils. The beam diameter and ham trajectory can be controlled by these coils. The characteristic of each part is measured ior the optimum condition of evaporation process. Moreover, Helmholtz coil is installed inside the vacuum chamber to adjust the incident angel of the beam to the melting surface for the maximum evaporation. We report on the evaporation rates for zirconium(Zr) and gadolinium(Gd) metals which have the high melting temperatures. 50 kW급 출력의 전자빔을 발생시킬 수 있는 축선 방식 전자총 (axial electron beam gun)과 전원장치를 제작하였다. 전자총은 전자빔 발생장치와 전자빔 궤적제어장치로 이루어졌다. 전자빔 발생장치는 필라멘트와 음극(cathode), 양극(anode)으로 구성되었고 전자빔의 최대전류는 2A, 가속전압은 평균 25kV이다. 전자빔 궤적제어장치는 전자빔의 크기를 조절하는 초점 (focusing) 코일과 전자빔의 방향을 조절하는 편향(deflection) 코일 및 주사 (scanning) 코일로 구성되었다. 전자총과 별개로 진공용기 내부에 Helmholtz 코일을 설치하여 시료의 표면에 입사되는 전자빔의 입사각도를 최적화시켰다. 각 부분의 동작 특성을 측정한 결과와 제작된 전자총으로 고융점 원소인 지르코늄 (zirconium, Zr)과 가돌리늄(gadolinium, Gd) 금속을 증발시킨 결과를 정리하였다.