본 연구에서는 폴리술폰 분리막을 이용한 바이오가스 정제 공정으로 고선택성 소재를 이용한 2단 공정의 높은 회 수율 및 경제성과 동등한 수준의 회수율을 확보하기 위해 저온 고압의 분리막 공정을 설계하고 평가하였다. 폴리술폰 고분자 를 4성분계 도프를 이용하여 비용매 유도 상전이법으로 중공사 분리막을 제조하였다. 기체 분리용 중공사 분리막은 1.6 m2의 유효 막면적을 갖는 샘플을 제조하여 상온 및 저온에서 기체 투과 특성을 평가하였다. 제조된 기체분리막 모듈의 온도에 따 른 기체 투과 특성을 분석하기 위하여 온도별 단일 기체 투과도를 평가한 결과 이산화탄소와 메탄 투과도는 20°C에서 각각 412, 12.7 GPU이며, -20°C에서는 각각 280, 3.6 GPU로써 이상 선택도는 32.4에서 77.8로 향상되었다. 단일 기체 투과 테스 트 후 혼합 기체에 대한 분리 테스트를 진행하였으며, 모듈 1단 구성 및 2단 구성(막 면적비 1:1, 1:2, 1:3)을 통하여 투과 거 동을 살펴보았다. 1단 구성에서는 stage-cut이 상승함에 따라 메탄의 농도가 상승하지만, 반대로 회수율은 떨어지는 결과를 나 타내었다. 2단 구성 테스트에서는 메탄 농도 97% 기준에서 막 면적비 1:1보다 1:3이 메탄의 회수율이 더 높게 측정되었으며, 공급 기체의 온도가 낮을수록 메탄의 회수율이 높아짐을 확인하였고, 최종적으로 폴리술폰 2단 공정에서 메탄 농도 97%, 회 수율 97%의 결과를 달성하였다.

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.

In this study, using a wet chemical process, we evaluate the effectiveness of different solution concentrations in removing layers from a solar cell, which is necessary for recovery of high-purity silicon . A 4-step wet etching process is applied to a 6-inch back surface field(BSF) solar cell. The metal electrode is removed in the first and second steps of the process, and the anti-reflection coating(ARC) is removed in the third step. In the fourth step, high purity silicon is recovered by simultaneously removing the emitter and the BSF layer from the solar cell. It is confirmed by inductively coupled plasma mass spectroscopy(ICP-MS) and secondary ion mass spectroscopy(SIMS) analyses that the effectiveness of layer removal increases with increasing chemical concentrations. The purity of silicon recovered through the process, using the optimal concentration for each process, is analyzed using inductively coupled plasma atomic emission spectroscopy(ICP-AES). In addition, the silicon wafer is recovered through optimum etching conditions for silicon recovery, and the solar cell is remanufactured using this recovered silicon wafer. The efficiency of the remanufactured solar cell is very similar to that of a commercial wafer-based solar cell, and sufficient for use in the PV industry.

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.