The purpose of flow analysis is to develop a simple CFD analysis model to develop a heat transfer analysis model including transient heat transfer characteristics, especially phase change, of thin film evaporators. The simple analytical model focuses on the evaporation phase change. To reduce the computational cost, the shape was simplified to two dimensions, and the simulation time was set short with a focus on simulating the phase change phenomenon. In the future, based on this analysis model, we will develop an analysis model for simulating not only vaporization but also liquefaction, that is, transient distillation phenomenon, according to the shape of the thin film distillation device.
The 3D printing process provides a higher degree of freedom when designing ceramic parts than the conventional press forming process. However, the generation and growth of the microcracks induced during heat treatment is thought to be due to the occurrence of local tensile stress caused by the thermal decomposition of the binder inside the green body. In this study, an alumina columnar specimen, which is a representative ceramic material, is fabricated using the digital light process (DLP) 3D printing method. DTG analysis is performed to investigate the cause of the occurrence of microcracks by analyzing the debinding process in which microcracks are mainly generated. HDDA of epoxy acrylates, which is the main binder, rapidly debinded in the range of 200 to 500oC, and microcracks are observed because of real-time microscopic image observation. For mitigating the rapid debinding process of HDDA, other types of acrylates PETA, PUA, and MMA are added, and the effect of these additives on the debinding rate is investigated. By analyzing the DTG in the 25 to 300oC region, it is confirmed that the PETA monomer and the PUA monomer can suppress the rapid decomposition rate of HDDA in this temperature range.
Ti has received considerable attention for aerospace, vehicle, and semiconductor industry applications because of its acid-resistant nature, low density, and high mechanical strength. A common precursor used for preparing Ti materials is TiCl4. To prepare high-purity TiCl4, a process based on the removal of VOCl3 has been widely applied. However, VOCl3 removal by distillation and condensation is difficult because of the similar physical properties of TiCl4 and VOCl3. To circumvent this problem, in this study, we have developed a process for VOCl3 removal using Cu powder and mineral oil as purifying agents. The effects of reaction time and temperature, and ratio of purifying agents on the VOCl3 removal efficiency are investigated by chemical and structural measurements. Clear TiCl4 is obtained after the removal of VOCl3. Notably, complete removal of VOCl3 is achieved with 2.0 wt% of mineral oil. Moreover, the refined TiCl4 is used as a precursor for the synthesis of Ti powder. Ti powder is fabricated by a thermal reduction process at 1,100oC using an H2-Ar gas mixture. The average size of the Ti powder particles is in the range of 1-3 μm.
Hydroxy sodalite (HS) is reported as high-temperature water separating zeolite membrane because of its small β-cage structure (pore size=2.8Å). HS zeolite particles were synthesized using various experimental set-ups including water bath, oil bath, refluxing and hydrothermal method using a gel composition of 5SiO2:1Al2O3:50Na2O:1000H2O. The morphology, crystallinity and purity of HS particles by changing silica source, temperature and synthesis time were studied. The products were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Particle sizes were increased with increase of temperature (90 °C - 180 °C) and time (2 – 24 h). Pure HS particles were obtained by using conventional hydrothermal synthesis at 120°C for 2h.
1970년대 중반 석유 파동 이후 대체 에너지 개발에 대한 관심이 커지면서 그중에서 혐기성 공정에서 발생하는 바이오가스 생산과 활용 기술 개발에 대한 연구가 진행되고 있다. 바이오 가스의 주성분은 50-70%CH4/30-40%CO2으로 이루어져 있고 이 때 메탄을 >95%순도로 농축하면 도시가스와 자동차 연료로 사용이 가능하다. 바이오가스의 정제기술로 막 분리법은 낮은 에너지 소모량, 이 동성 및 쉬운 작동성 등의 장점을 가지고 있다. 본 연구에서는 바이오가스를 95% 이상의 메탄으로 농축하기 위해 폴리설폰 중공사막과 다단 분리막 공정을 이용하였다. 분리막 공정에서 압력, 온도, 막면적 등 다양한 공정 변수에서 95% 이상의 메탄 순도를 얻기 위한 연구를 진행 하였다.