Abstract
본 연구에서는 지상 및 미소중력환경하에서 물리적 승화법 공정에서의 확산-대류유동에 미치는 불순물의 영향을 이론적으로 <TEX>$Hg_2Cl_2-I_2$</TEX> 시스템에 적용하여 규명하는 것이다. 이론적 해석은 증기상에서 확산-대류 흐름, 열 및 물질전달을 속도 벡터 흐름, 유선, 온도, 농도 분포를 통하여 제시된다. 결정 영역에서의 전체 몰플럭스는 중력가속도와 성분 <TEX>$I_2$</TEX>, 불순물에 상당히 민감하게 반응한다. 성분 <TEX>$I_2$</TEX>을 증가시켰을 때, 농도 대류효과는 확산-대류 유동흐름을 안정화시키는 경향이 있다. 지상중력가속도의 0.001환경에서는 유동흐름은 1차원포물선의 흐름 구조를 나타내며, 확산지배형태를 보여주고 있다. <TEX>$10^{-3}$</TEX>지상중력가속도 이하에서는 대류 영향은 무시할 수 있다. In this study, impurity effects on diffusive-convection flow fields by physical vapor transport under terrestrial and microgravity conditions were numerically analyzed for the mixture of <TEX>$Hg_2Cl_2-I_2$</TEX> system. The numerical analysis provides the essence of diffusive-convection flow as well as heat and mass transfer in the vapor phase during the physical vapor transport through velocity vector flow fields, streamlines, temperature, and concentration profiles. The total molar fluxes at the crystal regions were found to be much more sensitive to both the gravitational acceleration and the partial pressure of component <TEX>$I_2$</TEX> as an impurity. Our results showed that the solutal effect tended to stabilize the diffusive-convection flow with increasing the partial pressure of component <TEX>$I_2$</TEX>. Under microgravity conditions below <TEX>$10^{-3}g_0$</TEX>, the flow fields showed a one-dimensional parabolic flow structure indicating a diffusion-dominant mode. In other words, at the gravitational levels less than <TEX>$10^{-3}g_0$</TEX>, the effects of convection would be negligible.
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