• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.393-402
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• 2021

In this study, a mixed matrix membrane was prepared by putting the zeolitic imidazolate framework-7 (ZIF-7) synthesized in Pebax-1657 and Pebax-2533, which are representative poly(ether-b-amide), and the permeability properties of single gas such as N₂ and CO₂ were investigated. From the gas permeation results, in the case of N₂, both the Pebax-1657/ZIF-7 and Pebax-2533/ZIF-7 mixed matrix membranes showed a similar phenomenon in which the permeability decreased with the incorporation of ZIF-7. For CO₂ permeability, the tendency was slightly different depending on the type of polymer. In the Pebax-1657/ZIF-7 mixed membrane, the CO₂ permeability decreased in the range of 0~3 wt% of ZIF-7, and increased at higher contents. The CO₂ permeability of the Pebax-2533/ZIF-7 mixed matrix membrane gradually decreased without increasing the permeability in the range of 0~5 wt% of ZIF-7. Regarding CO₂/N₂ selectivity, both mixed films showed a tendency to increase with increasing the ZIF-7 content. In particular, Pebax-2533/ZIF-7 5 wt% showed the best gas permeation performance compared to other mixed matrix membrane. This is thought to be because ZIF-7 shows better compatibility with Pebax-2533 than that of Pebax-1657 and also better CO₂ selective property.

• Membrane Journal
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• v.23 no.4
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• pp.278-282
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• 2013

Zeolitic imidazolate frameworks (ZIFs) have been the focus of interest for their physical and chemical properties, especially, for their extraordinary gas separation properties. In this study, a novel and efficient method for the fabrication of continuous ZIF-7 film on ${\alpha}$-alumina substrate has been investigated. The electrospray deposition method was tried for the first time to prepare ZIF films directly without the necessity of prior substrate seeding. It has the advantage of depositing thin ZIF-7 films directly on the ${\alpha}$-alumina substrate by electrospraying the precursor solution. The ZIF-7 films have been characterized through XRD, FE-SEM, and single gas permeation tests.

• Membrane Journal
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• v.24 no.4
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• pp.259-267
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• 2014

PEBAX[poly(ether-block-amide)-ZIF-8(zeolitic imidazolate framework) composite membranes were prepared with different amounts of ZIF-8; 0, 1, 3, 7, 10, and 20 wt%. Gas permeation experiment were performed by varying the temperature of 25, 35, $40^{\circ}C$ under condition $6kgf/cm^2$. Gas permeability of $C_3H_6$, $C_3H_8$ and selectivity ($C_3H_6/C_3H_8$) were investigated by increasing the amount of ZIF-8 in the PEBAX. The gas permeability of $C_3H_6$ and $C_3H_8$ increased as ZIF-8 content increased among 0 to 7 wt% range and decreased among 7 to 20 wt% range. When the ZIF contents of PEBAX-ZIF composite membrane were 7 wt%, the selectivity ($C_3H_6/C_3H_8$) was taken between 3.6 and 3.8 value and also had the lowest activation energy.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.340-346
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• 2014

Continuous and dense ZIF-7 membranes were successfully synthesized on ${\alpha}-Al_2O_3$ porous substrate via two-step crystallization technique. ZIF-7 seeding layer was first deposited on porous ${\alpha}-Al_2O_3$ substrate by in-situ low temperature crystallization, and then ZIF-7 membrane layer can be grown through the secondary high-temperature crystallization. Two synthesis solutions with different concentration were used to prepare ZIF-7 seeding layer and membrane layer on porous ${\alpha}-Al_2O_3$ substrate, respectively. As a result, a continuous and defect-free ZIF-7 membrane layer can be prepared on porous ${\alpha}-Al_2O_3$ substrate, as confirmed by scanning electron microscope. XRD characterization shows that the resulting membrane layer is composed of pure ZIF-7 phase without any impurity. A single gas permeation test of $H_2$, $O_2$, $CH_4$ or $CO_2$ was conducted based on our prepared ZIF-7 membrane. The ZIF-7 membrane exhibited excellent H2 molecular sieving properties due to its suitable pore aperture and defect-free membrane layer.

• Membrane Journal
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• v.31 no.3
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• pp.200-211
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• 2021

In this study, mixed matrix membranes were prepared by mixing the synthesized zeolitic imidazolate framework-7 (ZIF-7) with poly(ether-b-amide) 2533 (PEBAX2533). A single gas (N₂, CO₂) was permeated through the membrane to investigate the properties of the gas. Through FT-IR, XRD, and FE-SEM, the peaks and shapes of ZIF-7 were confirmed, and it was determined that the synthesis was successful. Through TGA, it was confirmed that ZIF-7 has excellent thermal stability and that when incorporated into the membrane, the thermal stability is improved compared to pure PEBAX2533. It was found that ZIF-7 synthesized through BET had excellent CO₂ adsorption capacity and CO₂/N₂ adsorption selectivity showed a high value of about 49.64. For the gas permeation, as the ZIF-7 content in the mixed membrane increases, the N₂ permeability decreases and the CO₂ permeability slightly decreases, while the CO₂/N₂ selectivity steadily increases. In particular, when 20 wt% of ZIF-7 was added, the CO₂ permeability did not decrease significantly and the CO₂/N₂ selectivity increased considerably, resulting in the performance approaching to the Robeson upper-bound.

• Journal of Sensor Science and Technology
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• v.26 no.3
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• pp.204-208
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• 2017

Highly uniform and well-dispersed Zeolitic Imidazolate Framework-7 (ZIF-7) particles were prepared by the precipitation of $Zn^{2+}$ using benzimidazole, which were converted into ZnO nanoparticles by heat treatment at $500^{\circ}C$ for 24 h. The ZIF-7 derived ZnO nanoparticles showed abundant mesopores, high surface area, and good dispersion. The gas sensing characteristics toward 5 ppm acetone, ethanol, trimethylamine, ammonia, p-xylene, toluene, benzene, and carbon monoxide and carbon dioxide were investigated at $350-450^{\circ}C$. ZIF-7 derived ZnO nanoparticles exhibited high response to 5 ppm acetone ($R_a/R_g=57.6$; $R_a$: resistance under exposure to the air, Rg: resistance under exposure to the gas) at $450^{\circ}C$ and negligible cross-responses to other interference gases (trimethylamine, ammonia, p-xylene, toluene, benzene, carbon monoxide, carbon dioxide) and relatively low responses to ethanol. ZIF derived synthesis of metal oxide nanoparticles can be used to design high performance acetone sensors.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.106-106
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• 2017

가스센서는 사내 및 산업 환경에서의 유독성 또는 폭발성 가스 검출, 환경 모니터링, 질병 진단 등 매우 다양한 응용분야에서 큰 관심을 가지고 있다. 반도체 금속산화물(SMOs) 기반의 센서 분야에서는 이들의 감도 및 선택성을 향상시키기 위해 많은 노력을 기울이고 있다. 이는 센서의 선택성을 부여하게 되면 다양한 가스들이 존재하는 환경에서도 검출자가 원하는 가스만의 응답을 얻을 수 있기 때문이다. 본 연구에서는 MOF(Metal-Organic Framwork) 기반 멤브레인으로 ZIF-8(Zeolitic Imidazolate Frameworks 구조들 중 하나) 멤브레인 쉘 층을 이용하여 ZnO 나노선에 형성하였다. ZnO 나노선은 VLS공정 (Vapor-Liquid-Solid)을 이용하여 패턴된 전극을 갖는 $SiO_2$-grown Si 웨이퍼 상에 성장되었고, 성장된 ZnO 나노선은 2-methyl imidazole과 methanol이 포함된 고용체에 넣고 폐쇄된 압력용기 속에서 가열시켜 얻게 된다. 이렇게 얻어진 ZIF-8@ZnO 나노선의 ZIF-8 멤브레인은 분자 체 구조(molecular sieving structure)를 갖게 되며, 이들의 pore 크기는 약 $3.4{\AA}$을 갖는다. 따라서 이보다 더 큰 동적 직경을(kinetic diameter) 갖는 가스 종은 이 멤브레인을 통과할 수 없음을 나타내므로 제작된 시편은 $H_2$(kinetic diameter : $2.89{\AA}$), $C_7H_8$(kinetic diameter : $5.92{\AA}$), 그리고 $C_6H_6$(kinetic diameter : $5.27{\AA}$) 가스들을 각각 사용함으로써 ZIF-8@ZnO 나노선의 센서 특성을 조사했으며, 보다 정확한 비교를 위해 순수한 ZnO 나노선 역시 동일한 조건에서 측정되었다. 결과를 통해, 수소 가스를 제외한 다른 가스들에 대해서는 반응을 하지 않고, 오직 수소 가스에 대해서만 반응을 나타냈으며, 순수 ZnO 나노선의 수소 감응도보다 낮은 감응도를 나타내었다. 이는 멤브레인 쉘 층을 형성함으로써 ZnO 나노선의 표면적이 감소해 가스 분자와의 접촉점을 감소시키기 때문이라고 판단된다. 이와 같은 MOF 멤브레인의 캡슐화 전략은 가스센서뿐 아니라 바이오 센서 및 광촉매 등과 같은 이온 선택성을 필요로 하는 다양한 응용분야에 적용될 수 있을 것으로 기대된다.

• Radiation Oncology Journal
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• v.24 no.4
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• pp.309-316
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• 2006

$\underline{Purpose}$: To analyze the recent citation trend and to find a way to improve impact factor (IF) of the Journal of Korean Therapeutic Radiology and Oncology (JKSTRO) by analysis of Korean Medical Citation Index (KoMCI) citation data of JKSTRO and comparison with that of mean citation data of all journals enlisted on KoMCI (KoMCI journals) during 2000-2005. $\underline{Materials\;and\;Methods}$: All citation data of entire journals enlisted on KoMCI and JKSTRO from 2000 to 2005 were obtained from KoMCI. The trend of total and annual number of published articles and reference citations, total citations and self-citations per paper, IF and impact factor excluding self-citations (ZIF) were described and compared on both KoMCI journals and JKSTRO. $\underline{Results}$: Annual number of published articles was decreased for 6 years on both KoMCI journals and JKSTRO (32% and 38% reduction rate). The number of Korean journal references per article is 1.6 papers on JKSTRO comparing to 2.0 papers on KoMCI journals. The percentage of Korean references/total references increased from 5.0% in 2000 to 7.7% in 2005 on JKSTRO and from 8.5% in 2000 to 10.1% on KoMCI journals. The number of total citations received/paper on JKSTRO (average 1.333) is smaller than that of KoMCI journals (average 1.694), there was an increased rate of 67% in 2005 comparing to 2000. The percentage of self-citations/total citations (average 72%) on JKSTRO is slightly higher than that of KoMCI journals (average 61%). IF of JKSTRO was gradually improved and 0.144, 0.125, 0.088, 0.107, 0.187, and 0.203 in 2000-2005 respectively. However, ZIF of JKSTRO is steadily decreased from 0.038 in 2000 to 0.013 in 2005 except 0.044 in 2004. $\underline{Conclusion}$: IF of JKSTRO was slightly improved but had some innate problem of smaller number of citations received. To make JKSTRO as a highly cited journal, the awareness of academic status of JKSTRO and active participation of every member of JKSTRO including encouraging self-citations of papers published recent 2 years and submission of English written papers, and active academic cooperation with related academic societies.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.12-17
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• 2017

Design of Reverse Stirling Cycle based refrigerator can be predicted by Schmidt theory as a useful tool and by experiment it is found that for practical purposes the power and efficiency predicted by this analysis are about 35% of the actual values. Therefore, appropriate provision is to be made for getting the realistic result with the minimum deviation. The present paper first investigates the suitability of application of Schmidt design analysis for standard ZIF-1002 and PLN-106 Single cylinder Cryogenerator model. As the result is found to be optimistic, the same design procedure is applied for the design of a separate Cryogenerator for generating a cooling effect which is sufficient to produce 7 kg per hour liquid nitrogen using an indigenous condenser of 80% effectiveness. The paper describes all the details of the design methodologies and relevant results are found to be satisfactory.