Zeolitic Imidazolate Framework(ZIF)는 기체의 선택적인 분리나 센서, 촉매 반응 등의 목적으로 널리 연구된다. 특히 촉매의 역할이 가능하기 때문에 반응과 동시에 가스를 분리 할 수 있는 막 반응기의 역할을 할 수 있다. 본 연구에서는 ZIF-8 입자를 합성하고, 이를 PVC-g-POEM 고분자 매트릭스에 분산하여 MMM(Mixed matrix membrane)으로 제조하였다. 특히, α-알루미나 지지체 위에 PVC-g-POEM/ZIF-8 혼합 용액을 스핀 코팅하여 균일한 두께의 MMM을 얻을 수 있었다. 합성된 MMM은 XRD, FE-SEM을 통해 결정상과 표면, 코팅 두께 등을 측정하였으며, 이성분계 기체 투과 실험을 통해 다양한 이성분계 기체에 대한 투과 특성을 살펴보았다.

MOF는 큰 비표면적과 조절 가능한 기공구조로 요즘 분리막 소재로 큰 관심을 받고 있다. ZIF-8은 MOF의 일종으로 높은 화학적 열적 안정성으로 최근 많은 연구가 진행되고 있다. ZIF-8 나노기공의 다공성 물질로 Zn이온이 2-메틸이미다졸로 연결되어 있는 유-무기 하이브리드 구조를 가진다. 본 연구에서는 디스크 모양의 α–알루미나 지지체 위에 in situ 방법으로 잘 상호 성장한 ZIF-8 분리막을 합성했다. In situ 방법은 오토클레이브 내에 지지체와 전구체 용액을 넣고 용매열 합성법으로 막을 합성하는 방법이다. 합성시간을 조절하여 막의 두께를 조절했고, 두께 변화에 따른 H2/CO2 기체 투과 특성을 조사했다. 합성된 ZIF-8 분리막은 XRD와 SEM를 통해 결정 및 표면, 두께 분석했다.

The H2/CO2selectivity across ZIF-7 membrane prepared by in-situ growth method at 105°C synthesis temperature for 2 h, was the highest at 15.98, nearly 4 times higher than H2/CO2 Knudsens E.q. factor of 4.7. ZIF-7 membranes prepared from in-situ growth method also surprisingly performed better than ZIF-7 membranes prepared by other innovative techniques such as electro-spray deposition and secondary growth methods. (selectivity : 9.59 and 4.7, respectively) Despite lower selectivity performance than the numerically predicted results, the micro-porous ZIF-7 membrane prepared in this work demonstrated higher H2 permeability of 3770 barrer. Performance comparison between various inorganic membranes, including ZIF-7 & ZIF-8 membranes, was made and a new upper boundary for inorganic membranes was also constructed and reported.

기체분리막으로 사용되는 주요 소재 중 하나인 폴리이미드는 강직한 유리상 고분자로써 우수한 열적⋅화학적 안정성을 가지며 기체에 대해 높은 선택도를 가지고 있다. 그러나 낮은 용해성으로 인해 가공이 어렵다는 단점이 있다. 본 연구에서는 이러한 문제를 해결하기 위해 고분자 사슬 내에 지환족을 가진 다이안하이드라이드와 여러 가지 다이아민을 이용하여 공중합체를 합성하였다. 자체의 비틀린 구조로 인한 사슬의 자유회전과 유연성의 증가시켜 사슬의 packing현상을 유도하였으며, 이에 따른 물리적 특성과 기체투과도에 미치는 영향을 알아보고자 하였다.

프로필렌은 석유화학제품의 기초원료이며 Naphtha Cracker에서 나오는 프로필렌/프로판 혼합물을 저온증류하여 생산된다. 이들을 분리하기 위해서는 많은 에너지가 소비되기 때문에 저소비형 공정인 막분리법이 대체법으로 연구가 진행되고 있다. 분리막 소재 중 폴리이미드는 높은 기계적 강도, 내열성, 내화학성을 가지고 있으며 특히 cardo 구조의 폴리이미드는 분별자유부피가 크기 때문에 투과도가 좋은 특징을 가지고 있다. 따라서 본 연구에서는 cardo 구조의 BAPF를 이용하여 폴리이미드 및 폴리이미드 공중합체를 합성하였고 FT-IR을 통해 합성이 이루어졌음을 확인하였다. 또한, time-lag 장치를 통해 프로필렌과 프로판의 기체투과특성을 알아보았다.

본 연구에서는 평균입경 0.2, 0.5, 1,7㎛ 크기의 α-알루미나 분말을 이용하여 다공성 α-알루미나 지지체의 기공구조를 조절하고자 하였다. 다공성 α-알루미나 지지체는 슬립캐스팅공법을 이용하여 제조한 후 소결하였으며, 이 때 소결 온도가 지지체의 기공특성에 미치는 영향에 대하여 고찰하였다. 제조된 다공성 α-알루미나 지지체는 수은기공분석기를 이용하여 기공크기 및 기공률 등을 분석하였으며, 단일기체투과장치를 이용하여 기체 투과도를 측정하였다. 그 결과 평균입경 0.2, 0.5, 1.7㎛ 크기의 α-알루미나 분말을 이용하여 제조된 지지체는 각각 80, 130, 200㎚의 기공경을 가졌으며, CO2 단일기체에 대해 각각 1300, 1700, 5000GPU를 나타냈다.

In this work, uniform and nanosize(75nm) silicalite-1 crystals was hydrothermally synthesized by using 9TPAOH:0.16NaOH:25Si:495H2O solution at 80 ℃. They were applied as seed in the secondary growth process for preparing silicalite-1 membrane by template-free method. The highest ethanol/water separation factor of 119 with flux 0.58kg/m². Furthermore, these membranes (nano seed, template free silicalite-1 membrane) exhibit high permselectivity of He over SF6(123), and small gas permeation mechanism and Knudsen diffusion studies suggest that the membranes contain negligible intercrystalline or non-zeolite pores.

금속 유기 골격체(Metal Organic Framework, 이하 MOF) 종류의 하나인 제올라이트형 이미 다졸레이트 골격체(Zeolitic Imidazolate Framework, 이하 ZIF) 중 ZIF-8은 Zn 금속이온과 imidazole 유기 리간드의 결합으로 이루어져 있다. 본 연구에서는 여러 종류의 용매에서 합성된 ZIF-8의 1차 결정과 2차 입자의 형성이 용매가 가진 특성에 영향을 받는 것을 확인하였다. HBD(hydrogen bond donation) 값이 큰 용매에서 합성된 ZIF-8의 1차 결정은 HBD 값이 작은 용매에서의 것보다 크기가 컸고, 용매의 유전상수의 값이 작을수록 2차 입자의 크기가 큰 ZIF-8이 합성되었다.

본 연구에서는 막 축전식 탈이온 공정에 적용하기 위해 온도와 시간을 달리하여 술폰화 Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP)을 합성 후 캐스팅법에 의해 양이온교환막이 제조되었다. 술폰화 PVDF (SPVDF) 는 Fourier-transform infrared (FT-IR), 1H Nuclear magnetic resonance (1H NMR)를 통해 구조확인을 하였고, X-ray Photoelectron Spectroscopy (XPS)를 통해 화학조성에 대한 정량적 분석을 하였다. 막 성능은 함수율 및 이온교환용량과 전기 저항을 측정하였고. 60°C에서 7시간 술폰화한 SPVDF 멤브레인이 이온교환용량 0.89 meq/g, 함수율 21.5%, 전기저항 3.70 Ω ⋅cm2로 가장 우수하였다. 수중 이온제거 특성을 막 축전식 탈이온 방법(MCDI)으로 전압(0.9~1.5 V), 유속(10~40 mL/min)을 변수로 SPVDF의 탈염 특성을 확인하여 MCDI 공정에 적용가능 여부를 평가하였다. MCDI 충방전 시험 결과 최대 탈염제거 율은 62.5%이었다.

Perforated polygonal cobalt oxide (Co3O4) is synthesized using electrospinning and a hydrothermal methodfollowed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravi-metric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal Co3O4, we pre-pare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template-10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sam-ple A exhibits the perforated polygonal Co3O4 with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF tem-plate. However, sample B and sample C synthesized perforated round Co3O4 and destroyed Co3O4 powders, respectively,due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonalCo3O4. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the suc-cessful formation of perforated polygonal Co3O4. Thus, perforated polygonal Co3O4 can be applied to electrode materialsof energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

One-dimensional (1D) silver nanostructures, which possess the highest conductivity among all room-temperature materials, moderate flexibility and high transmittance, are one of the most promising candidate materials to replace conventional indium tin oxide transparent electrodes. However, the short length and large diameter of 1D silver nanostructures cause a substantial decrease in the optical transparency or an increase in the sheet resistance. In this work, ultra-long silver nanofiber networks were synthesized with a low-cost and scalable electrospinning process, and the diameter of the nanofibers were finetuned to achieve a higher aspect ratio. The decrease in the diameter of the nanofibers resulted in a higher optical transparency at a lower sheet resistance: 87 % at 300 Ω/sq, respectively. It is expected that an electrospun silver nanofiber based transparent electrode can be used as a key component in various optoelectronic applications.

For the first time, PLL frequency synthesizer using DDS was adapted for the data link communication system which should fast transmit and receive each other with the correct information and fast Hopping System. It is inevitable to lost the synchronization by slow lock time about PLL and no cut off the noise. This paper propose the design of PLL frequency synthesizer which can make 800MHz frequency range. The PLL frequency synthesizer has three high qualities those are frequency accuracy, fast lock time and outstanding phase noise.

This study investigates the application of a synthetic resine based net-hose system to sustain vegetated embankment slope reinforcement. The net-hose system is designated to improve water supply to the vegetation that can suffer the lack of water in case of extreme drying condition or rock slope where water supply is relatively insufficient to ensure the growth of vegetation. A series of laboratory tests were conducted to check the structural adequacy and effectiveness of net-hose system. The results indicated that the model slope equipped with net-hose system seemed to provide better water supply resulting in more vegetated areas and higher matric suction due to active water uptake capacity, which might be contributed to greater shear strength of slope surface. A limited numerical analysis was conducted to verify the effect of water uptake on vegetated root system that generally yields better slope stability.

Fe-base superalloy powders with Y2O3 dispersion were prepared by high energy ball milling, followed by sparkplasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50mm were usedfor the preparation of Fe-20Cr-4.5Al-0.5Ti-O.5Y2O3 powder mixtures (wt%). The milling process of the powders was carriedout in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation(350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) wereapplied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclicoperation and was about 15nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constantmilling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at 1100oC for 30 min invacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, ahomogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized Zr41.2Ti13.8Cu12.5Ni10Be22.5 metallic glass powder under of 0.2 kJ generated by a 450 μF capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at 150oC for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped Fe2O3 and needle-shaped Fe3O4 are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

A low thermal expansion ceramic, cordierite (2MgO·2Al2O3·5SiO2), was synthesized using pyrophyllite. Pyrophyllite usually consists of SiO2 and Al2O3, which are the main components of cordierite. MgCO3 and Al(OH)3 were added in various amounts to pyrophyllite and fired for synthesis and sintering. α-cordierite crystallized from 1000 oC with mixing of 20 wt% MgCO3 and 1.7 wt% Al(OH)3, and un-reacted cristobalite was also detected with the cordierite. As the temperature was increased to 1400 oC, the cordierite yield was gradually increased. Powder compacts of the synthesized cordierite were sintered between 1250 oC ~ 1400 oC; the sintered samples showed a low thermal expansion coefficient of 2.1 × 10−6/ oC and typical sintering behavior. It is anticipated that it will be possible to synthesize cordierite ceramics on a mass production scale using the mineral pyrophyllite.

The functional wood plastic composite(WPC) is one of the noted materials for landscape architecture and residential construction. Iron band, embossing and drain holes are improve the strength and skid resistance of the WPC. In this study, we had developed an automatic manufacturing system for the functional WPC that has vertical pattern embossing and drain holes. The system is consist of an automatic vertical pattern embossing device, multi-spindle drilling M/C, sanding device, inspection equipment, and some facilities developed in the previous research. The performance tests on the several functional items of the system and manufactured WPC represented satisfactory values except the skid resistance and absorption thickness expansion rate.